424B5

424B5 1 d119567d424b5.htm 424B5 424B5

Filed Pursuant to Rule 424(b)(5)
Registration Statement No. 333-297027

PROSPECTUS SUPPLEMENT

(to Prospectus dated July 13, 2026)

LOGO

6,027,399 Shares of Common Stock

Pre-Funded Warrants to Purchase up to 4,931,506 Shares of Common Stock

We are offering 6,027,399 shares of our common stock and, in lieu of common stock to certain investors that so choose, pre-funded warrants to purchase up to 4,931,506 shares of our common stock in this offering.

The per share purchase price of the common stock is $18.25. The purchase price of each pre-funded warrant will be equal to the price per share at which shares of our common stock are being sold to the public in this offering, minus $0.0001, which is the exercise price of each pre-funded warrant. Each pre-funded warrant is exercisable for one share of our common stock at an exercise price of $0.0001 per share. The pre-funded warrants are exercisable at any time after issuance, subject to ownership limitations, and will expire when exercised in full. This offering also relates to the shares of common stock issuable upon exercise of the pre-funded warrants sold in this offering.

Our common stock is listed on the Nasdaq Capital Market under the symbol “QTTB.” On July 10, 2026, the last reported sale price of our common stock on the Nasdaq Capital Market was $11.21 per share. There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to list the pre-funded warrants on the Nasdaq Capital Market or any other national securities exchange or nationally recognized trading system.

As of the date of this prospectus supplement, we are a “smaller reporting company” as defined under Rule 405 of the Securities Act of 1933, as amended (the “Securities Act”), and, as such, are subject to certain reduced public company reporting requirements. See “Prospectus Summary—Implications of Being a Smaller Reporting Company” on page S-5 of this prospectus supplement.

Per Share

Per Pre-Funded
Warrant

Total

Public offering price

18.2500

18.2499

199,999,523.0994

Underwriting discounts and commissions (1)

1.0950

12,000,000.9750

Proceeds, before expenses, to us

17.1550

17.1549

187,999,522.1244

(1)

See the section titled “Underwriters” beginning on page S-24 for a description of the compensation payable to the underwriters.

We have granted the underwriters an option for a period of 30 days from the date of this prospectus supplement to purchase up to an additional 1,643,835 of shares of our common stock at the public offering price, less the underwriting discounts and commissions.

Investing in our common stock or pre-funded warrants involves a high degree of risk. You should review carefully the risks and uncertainties described under the header “Risk Factors” contained in this prospectus supplement beginning on page S-8 and under similar headings in the other documents that are incorporated by reference into this prospectus supplement and the accompanying prospectus.

Neither the Securities and Exchange Commission, nor any state securities commission nor any other regulatory body has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the shares of common stock and pre-funded warrants against payment therefor on or about July 16, 2026.

Joint Book-Running Managers



Morgan Stanley	Jefferies	Cantor	Oppenheimer & Co.

Lead Manager

H.C. Wainwright & Co.

The date of this prospectus supplement is July 14, 2026.

TABLE OF CONTENTS

Prospectus Supplement


		Page
ABOUT THIS PROSPECTUS SUPPLEMENT		S-1
PROSPECTUS SUPPLEMENT SUMMARY		S-3
THE OFFERING		S-6
RISK FACTORS		S-8
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS		S-11
USE OF PROCEEDS		S-13
DIVIDEND POLICY		S-14
DILUTION		S-15
DESCRIPTION OF PRE-FUNDED WARRANTS		S-17
MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES TO NON-U.S. HOLDERS		S-19
UNDERWRITERS		S-24
LEGAL MATTERS		S-34
EXPERTS		S-34
WHERE YOU CAN FIND MORE INFORMATION		S-34
INCORPORATION BY REFERENCE		S-34

Prospectus


	Page
ABOUT THIS PROSPECTUS		1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS		3
PROSPECTUS SUMMARY		5
SECURITIES WE MAY OFFER		7
RISK FACTORS		8
USE OF PROCEEDS		9
DESCRIPTION OF CAPITAL STOCK		10
DESCRIPTION OF DEBT SECURITIES		15
DESCRIPTION OF WARRANTS		17
DESCRIPTION OF UNITS		18
TAXATION		19
PLAN OF DISTRIBUTION		20
LEGAL MATTERS		24
EXPERTS		24
WHERE YOU CAN FIND MORE INFORMATION		24
INCORPORATION BY REFERENCE		24

ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering of common stock and pre-funded warrants and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The second part is the accompanying prospectus dated July 13, 2026, included in our registration statement on Form S-3, along with the documents incorporated by reference therein, which provides more general information, some of which may not apply to this offering. Generally, when we refer to this prospectus, we are referring to both parts of this document combined.

To the extent there is a conflict between the information contained in this prospectus supplement, on the one hand, and the information contained in the accompanying prospectus or in any document incorporated by reference that was filed with the Securities and Exchange Commission (the “SEC”), before the date of this prospectus supplement, on the other hand, you should rely on the information contained in this prospectus supplement. If any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement.

This prospectus supplement and the accompanying prospectus are part of a “shelf” registration statement that we filed with the SEC. Under the shelf registration statement, we may offer from time to time various securities, of which this offering of shares of our common stock and pre-funded warrants is a part. Such registration statement also includes exhibits that provide more detail on the matters discussed in this prospectus supplement and the accompanying prospectus. You should read this prospectus supplement, the accompanying prospectus, including the information incorporated by reference herein and therein, the exhibits filed with the SEC, and any free writing prospectus that we have authorized for use in connection with this offering, in their entirety before making an investment decision.

You should rely only on the information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus, along with the information contained in any free writing prospectus that we have authorized for use in connection with this offering. We have not, and the underwriters have not, authorized anyone to provide you with information other than the information that we have provided or incorporated by reference in this prospectus supplement or the accompanying prospectus and your reliance on any unauthorized information or representation is at your own risk. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus, the documents incorporated by reference in this prospectus supplement and the accompanying prospectus, and in any free writing prospectus that we have authorized for use in connection with this offering is accurate only as of the respective dates of those documents, unless we indicate otherwise. Our business, financial condition, results of operations and prospects may have changed since those dates.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference in this prospectus supplement or the accompanying prospectus were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties and covenants were accurate only as of the date when made; therefore, such representations, warranties and covenants should not be relied on as accurate representations of the current state of our affairs.

We are offering to sell, and seeking offers to buy, shares of our common stock and pre-funded warrants only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement or the accompanying prospectus and the offering of the common stock and pre-funded warrants in certain jurisdictions may be restricted by law. Persons outside the United States who come into possession of this prospectus

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supplement or any accompanying prospectus must inform themselves about, and observe any restrictions relating to, the offering of the common stock and pre-funded warrants and the distribution of this prospectus supplement or any accompanying prospectus outside the United States. This prospectus supplement or any accompanying prospectus does not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement or any accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

When we refer to “Q32 Bio,” “we,” “our,” “us” and the “Company” in this prospectus supplement, we mean Q32 Bio Inc. and, where appropriate, our subsidiaries, unless otherwise specified. When we refer to “you,” we mean the holders of our common stock and pre-funded warrants.

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PROSPECTUS SUPPLEMENT SUMMARY

This summary highlights certain information about us, this offering and selected information contained elsewhere in, or incorporated by reference into, this prospectus supplement and the accompanying prospectus. This summary is not complete and does not contain all of the information that you should consider before deciding whether to invest in our common stock or pre-funded warrants. For a more complete understanding of our company and this offering, we encourage you to read and consider carefully the more detailed information in this prospectus supplement and the accompanying prospectus, including our financial statements and related notes and the other information incorporated by reference into this prospectus supplement and the accompanying prospectus, and the information included in any free writing prospectus that we have authorized for use in connection with this offering, including the information referred to under the heading “Risk Factors” in this prospectus supplement beginning on page S-8 and in the documents incorporated herein by reference.

Company Overview

We are a clinical stage biotechnology company focused on developing innovative therapies for alopecia areata (“AA”) and other autoimmune and inflammatory diseases.

Bempikibart (ADX-914), our most advanced product candidate, is a fully human anti–interleukin-7 receptor alpha antagonist monoclonal antibody designed to re-regulate adaptive immune function by potently blocking signaling mediated by interleukin-7 and thymic stromal lymphopoietin. We have completed two Phase 2a clinical trials evaluating bempikibart, SIGNAL-AA Part A, for the treatment of AA, and SIGNAL-AD, for the treatment of atopic dermatitis. In December 2024, we announced topline results from both of these trials, as well as our intention to advance bempikibart for the treatment of AA.

In April 2025, we announced dosing of the first patients in Part B of the SIGNAL-AA Phase 2a clinical trial. Patients will be treated with bempikibart for 36 weeks, with follow-up out to 52 weeks. Efficacy will be evaluated on the basis of mean percentage change from baseline in Severity of Alopecia Tool (“SALT”) scores as well as the proportion of subjects achieving various relative and absolute SALT score improvements at week 36, with follow-up through week 52. The trial is intended to support advancement into pivotal trials upon completion, pending review of the results.

Following completion of the SIGNAL-AA Part B trial through 52 weeks, eligible patients can enter an open-label extension (“OLE”) period to enable longer-term follow-up and continued dosing. In May 2026, we announced that the first patient has been dosed in the OLE portion of Part B.

In addition to bempikibart, our strategy has been focused on the advancement of our proprietary tissue-targeted complement inhibitor platform. However, in February 2025, we announced a corporate restructuring to focus on the advancement of bempikibart for the treatment of patients with AA. In November 2025, we entered into an Asset Purchase Agreement with Akebia Therapeutics, Inc. (“Akebia”) pursuant to which we sold to Akebia substantially all of our assets related to the research, development, manufacture and commercialization of ADX-097, a Phase 2 asset from this platform. Following the asset sale, Akebia is now responsible for the future development and commercialization of ADX-097. Other assets developed from our proprietary platform include ADX-096, and C3d mAb fusions and nanobodies designed for tissue-targeted complement inhibition. We retain the rights to our wholly owned tissue-targeted complement inhibitor platform, including ADX-096, and other remaining early-stage assets, and are continuing to evaluate strategic options for these programs.

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Recent Developments

36-Week Topline Results from Part B of the SIGNAL-AA Program

The Part B portion of the SIGNAL-AA program is an open-label clinical trial building upon the previously completed Part A, which established proof-of-concept of bempikibart in AA. In Part B, bempikibart is being evaluated in 33 patients with severe or very severe AA (baseline SALT scores of 50-100) with a maximum duration of current episode of four years. Enrollment amongst patients with prior exposure to JAK inhibitor therapy were allowed; amongst the 33 enrolled patients, 36.4% had previously been treated with oral JAK inhibitors.

Total enrollment exceeded the initial target due to patient demand. In Part B, patients are treated with bempikibart for 36 weeks, with off-drug follow-up through Week 52 before optional enrollment in the OLE. Dosing includes an initial loading regimen of 200mg of bempikibart dosed weekly for four doses, followed by continued dosing of 200mg every-other-week over a 32-week period, for a total dosing period of 36 weeks. Across both regimens, bempikibart was administered subcutaneously.

The prespecified primary efficacy analysis was evaluated on the basis of mean percentage change from baseline in SALT scores in the modified intent-to-treat (“mITT”) population. Additional prespecified efficacy analyses included the proportion of patients achieving various relative and absolute SALT improvements including SALT-20 (80% of scalp hair coverage), SALT₃₀ (30% improvement in SALT score from baseline), and SALT₅₀ (50% improvement in SALT score from baseline) responses at Week 36, with follow-up through Week 52.

Key topline efficacy results from Part B of SIGNAL-AA at Week 36 include:

•

Mean percent reduction in SALT score from baseline of 35.3% in the mITT analysis.

•

40.0% (10/25) of patients in the mITT analysis and 30.3% (10/33) of patients in the intent-to-treat (“ITT”) analysis achieved a SALT-20 response. Achievement of a SALT-20 response was observed in patients with both severe and very severe disease.

•

44.0% (11/25) of patients in the mITT analysis and 33.3% (11/33) of patients in the ITT analysis achieved SALT₃₀ response.

•

44.0% (11/25) of patients in the mITT and 33.3% (11/33) of patients in the ITT analysis achieved SALT₅₀ response.

•

Early signs of durability in the off-drug period include maintenance or deepening of response in multiple patients including one who achieved complete hair growth (SALT = 0).

Bempikibart was observed to have a generally well-tolerated safety profile in SIGNAL-AA Part B, consistent with prior studies. No new safety signals were observed. There were no serious adverse events or Grade 3 or higher adverse events related to treatment. The most common treatment-emergent adverse event was injection site reaction (“ISR”) (36.3%) which were primarily singular events, with ISR incidence of 4% across all Part B dose administrations. All ISRs reported were mild and resolved with no intervention, with the majority resolving within a day.

Bempikibart demonstrated a favorable pharmacokinetic (“PK”), pharmacodynamic and anti-drug antibody (“ADA”) profile in Part B. PK data from Part B support the loading dose regimen had its intended effect, achieving steady state concentrations approximately 10-weeks earlier than in Part A. Negligible ADA was observed in Part B.

The Part B off-drug follow-up period through Week 52 remains ongoing. Additionally, enrollment of eligible patients into the OLE remains ongoing. We intend to advance bempikibart into a registration-directed program in the first half of 2027 and plan to share full results from Part B at a future medical meeting.

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Results from SIGNAL-AA Part A OLE

Following the emergence of Part A data suggesting durability of response in the off-drug follow-up from SIGNAL-AA Part A and given patient demand for continued dosing, we announced the initiation of an OLE in April 2025. The Part A OLE has been completed. Eight patients enrolled in the Part A OLE, spanning responders, non-responders, and placebo patients from the Part A treatment portion. Patients were off-drug for various time periods ranging from 26 to 55 weeks prior to re-dosing. In the Part A OLE, bempikibart continued to demonstrate a generally well-tolerated safety profile with longer-term dosing and no new safety issues. Patients who maintained hair at entry to the OLE were observed to have durable or further hair growth. In totality, the Part A OLE dataset supports the importance of a maintenance dosing regimen.

Corporate Updates

On June 24, 2026, we paid off the remaining balance in the amount of approximately $6.8 million under the Loan and Security Agreement (the “Loan Agreement”) between us and Silicon Valley Bank, a division of First-Citizens Bank & Trust Company (“SVB”), pursuant to a Pay-Off Letter between us and SVB dated June 24, 2026. Accordingly, the Loan Agreement has been terminated.

Corporate Information

We were incorporated under the laws of the State of Delaware on April 10, 2017. On March 25, 2024, Kenobi Merger Sub, Inc. (the “Merger Sub”), a wholly-owned subsidiary of Homology Medicines, Inc. (“Homology”), completed its merger with and into Q32 Bio Operations Inc. (previously named Q32 Bio Inc. and referred to herein as Legacy Q32), with Legacy Q32 continuing as the surviving entity as a wholly-owned subsidiary of Homology (the “Merger”). Homology changed its name to Q32 Bio Inc., and Legacy Q32, which remains as a wholly-owned subsidiary of ours, changed its name to Q32 Bio Operations, Inc. The Merger was effected pursuant to an Agreement and Plan of Merger, dated as of November 16, 2023, by and among Homology, Legacy Q32, and Merger Sub. Effective March 26, 2024, our common stock began trading on the Nasdaq Global Market under the trading symbol “QTTB.” Our principal executive office is located at 830 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (781) 999-0232. Our website address is https://www.q32bio.com. We do not incorporate the information on or accessible through our website into this prospectus supplement, and you should not consider any information on, or that can be accessed through, our website as part of this prospectus supplement.

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company” as defined in the Securities Exchange Act of 1934, as amended (the “Exchange Act”). We may take advantage of certain of the scaled disclosures available to smaller reporting companies and will be able to take advantage of these scaled disclosures for so long as the market value of the common stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter, or our annual revenue is less than $100.0 million during the most recently completed fiscal year and the market value of the common stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter. As a result, the information in or incorporated by reference into this prospectus supplement and that we provide to our investors in the future may be different than what you might receive from other public reporting companies.

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THE OFFERING


Common stock offered by us		6,027,399 shares.

Pre-funded warrants offered by us		We are also offering, in lieu of common stock to certain investors that so choose, pre-funded warrants to purchase up to 4,931,506 shares of common stock. The purchase price of each pre-funded warrant will be equal to the price per share at which shares of our common stock are being sold to the public in this offering, minus $0.0001, which is the exercise price of each pre-funded warrant. Each pre-funded warrant is exercisable for one share of our common stock at an exercise price of $0.0001 per share. The pre-funded warrants are exercisable at any time after issuance, subject to ownership limitations, and will expire when exercised in full. This prospectus supplement also relates to the offering of the shares of common stock issuable upon exercise of the pre-funded warrants sold in this offering.

Underwriters’ option to purchase additional shares		We have granted the underwriters an option to purchase up to an additional 1,643,835 shares of our common stock from us, at the public offering price, less the underwriting discounts and commissions, for a period of 30 days after the date of this prospectus supplement. The number of shares subject to the underwriters’ option will equal 15% of the aggregate number of shares of common stock and pre-funded warrants we are offering.

Common stock to be outstanding immediately after this offering		29,708,814 shares (or 31,352,649 shares, if the underwriters exercise their option in full to purchase additional shares), in each case, assuming no exercise of any pre-funded warrants offered and sold by us.

Use of proceeds		We currently intend to use the net proceeds from this offering, together with our existing cash and cash equivalents, for working capital purposes including expenses related to research, clinical development and commercialization efforts including for supporting the advancement of bempikibart into future clinical trials. See “Use of Proceeds” on page S-13 of this prospectus supplement.

Risk Factors		Investing in our common stock or pre-funded warrants involves significant risks. You should read the “Risk Factors” section of this prospectus supplement beginning on page S-8, page 8 of the accompanying prospectus, and other information included in, or incorporated by reference into, this

S-6


		prospectus supplement and the accompanying prospectus for a discussion of factors to consider before deciding to purchase shares of our common stock or pre-funded warrants.

Nasdaq Capital Market Symbol		“QTTB”. There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to list the pre-funded warrants on any securities exchange or nationally recognized trading system. Without a trading market, the liquidity of the pre-funded warrants will be limited.

The number of shares of our common stock to be outstanding immediately after this offering is based on 14,629,463 shares of our common stock outstanding as of March 31, 2026 and after giving effect to (i) 6,725,000 shares of common stock (the “PIPE Shares Issuance”) issued to certain institutional investors pursuant to a private placement on May 28, 2026 (the “2026 PIPE”) and (ii) 2,326,952 shares of common stock sold pursuant to our “at-the-market” program in accordance with our Controlled Equity Offering^SM Sales Agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor”), since March 31, 2026 and through the date of this prospectus supplement (the “ATM Issuance”), and excludes:

•

2,264,082 shares of common stock issuable upon the exercise of stock options outstanding as of March 31, 2026 at a weighted-average exercise price of $2.86 per share;

•

599,326 shares of common stock issuable upon vesting and settlement of restricted stock units outstanding as of March 31, 2026;

•

2,130,724 shares of common stock available for future issuance under our 2024 Stock Option and Incentive Plan (the “2024 Plan”) as of March 31, 2026;

•

371,393 shares of common stock available for future issuance under our 2024 Employee Stock Purchase Plan (the “2024 ESPP”) as of March 31, 2026;

•

18,144 shares of common stock issuable upon the exercise of outstanding warrants as of March 31, 2026;

•

1,025,654 shares of common stock issuable upon the exercise of outstanding pre-funded warrants as of March 31, 2026; and

•

150,000 shares of common stock issuable upon the exercise of outstanding pre-funded warrants issued as part of the 2026 PIPE.

Unless otherwise stated, all information contained in this prospectus supplement reflects and assumes (a) no exercise of the outstanding options, vesting and settlement of unvested restricted stock units or exercise of outstanding warrants or pre-funded warrants described referred to above after March 31, 2026, (b) no exercise by the underwriters of their option to purchase additional shares of our common stock from us, and (c) no exercise of the pre-funded warrants that we are offering in lieu of common stock to certain investors in this offering.

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RISK FACTORS

Investing in our common stock or pre-funded warrants involves a high degree of risk. You should carefully consider the risk factors described below and the risk factors incorporated by reference to our Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on March 10, 2026, our subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K and any such reports we file after the date of this prospectus supplement, and all other information contained or incorporated by reference into this prospectus supplement and the accompanying prospectus, including our financial statements and the related notes, as updated by our subsequent filings under the Exchange Act and in any free writing prospectus that we have authorized for use in connection with this offering before acquiring any of our common stock or pre-funded warrants. These risks could have a material and adverse impact on our business, results of operations, financial condition and growth prospects, which may cause the trading price of our common stock to decline, and you could lose all or part of your investment. The risks discussed below also include forward-looking statements and our actual results may differ substantially from those discussed in these forward-looking statements. See “Cautionary Note Regarding Forward-Looking Statements.”

Risks Relating to this Offering, our Common Stock and the Pre-Funded Warrants

You will experience immediate and substantial dilution in the net tangible book value of shares or pre-funded warrants you purchase.

Given that the offering price of our securities in this offering is substantially greater than the net tangible book value per share of our common stock prior to this offering, you will suffer immediate and substantial dilution in the net tangible book value of the common stock or pre-funded warrants you purchase in this offering. Accordingly, if you purchase our common stock or pre-funded warrants in this offering, you will incur immediate substantial dilution of approximately $8.13 per share, representing the difference between the public offering price per share of common stock and our as adjusted net tangible book value as of March 31, 2026. For a more detailed discussion of the foregoing, see the section entitled “Dilution” below. To the extent outstanding stock options, warrants or pre-funded warrants are exercised or any outstanding restricted stock units vest and settle, there will be further dilution to new investors. See the section entitled “Dilution” below for a more detailed illustration of the foregoing.

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

Our management will have broad discretion in the application of the net proceeds from this offering, including for any of the purposes described in the section entitled “Use of Proceeds,” and you will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used appropriately. Because of the number and variability of factors that will determine our use of the net proceeds from this offering, their ultimate use may vary substantially from their currently intended use. Our management might not apply our net proceeds in ways that ultimately increase the value of your investment. If we do not invest or apply the net proceeds from this offering in ways that enhance stockholder value, we may fail to achieve expected financial results, which could cause our stock price to decline.

You may experience future dilution as a result of future equity offerings.

To raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions

S-8

may be higher or lower than the price per share paid by investors in this offering. Further, the exercise of pre-funded warrants sold in this offering will result in further dilution to the holders of our common stock.

Future sales or issuances of our common stock in the public markets, or the perception of such sales, could depress the trading price of our common stock.

The sale of a substantial number of shares of our common stock or other equity-related securities in the public markets, or the perception that such sales could occur, could depress the market price of our common stock and impair our ability to raise capital through the sale of additional equity securities. We may sell large quantities of our common stock at any time in one or more separate offerings in the future. We cannot predict the effect that future sales of common stock or other equity-related securities would have on the market price of our common stock.

The price of our common stock may be volatile and fluctuate substantially, which could result in substantial losses for purchasers of our common stock.

Our stock price is likely to be volatile. The stock market in general and the market for biopharmaceutical companies in particular have experienced extreme volatility that has often been unrelated to the operating performance of particular companies. As a result of this volatility, purchasers of our common stock could incur substantial losses. The market price for our common stock may be influenced by many factors, including:

•

the success of competitive drugs or technologies;

•

results of preclinical studies and clinical trials of our current or future product candidates or those of our competitors;

•

unanticipated safety concerns related to the use of any of our product candidates;

•

regulatory or legal developments in the U.S. and other countries;

•

developments or disputes concerning patent applications, issued patents or other proprietary rights;

•

the recruitment or departure of key personnel;

•

the level of expenses related to any of our current or future product candidates or clinical development programs;

•

the results of our efforts to discover, develop, acquire or in-license additional current or future product candidates or drugs;

•

actual or anticipated changes in estimates as to financial results, development timelines or recommendations by securities analysts;

•

variations in our financial results or those of companies that are perceived to be similar to us;

•

product liability claims or other litigation;

•

changes in the structure of healthcare payment systems;

•

market conditions in the pharmaceutical and biotechnology sectors;

•

general economic, industry and market conditions, including inflation and potential tariffs; and

•

the other factors described in this prospectus supplement and the accompanying prospectus and listed under the caption “Risk Factors” in our most recent Annual Report on Form 10-K and our subsequent Quarterly Reports on Form 10-Q.

The stock market in general, and the Nasdaq Capital Market and biotechnology companies in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the

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operating performance of these companies, which has resulted in decreased stock prices for many companies notwithstanding the lack of a fundamental change in their underlying business models or prospects. Broad market and industry factors, including potentially worsening economic conditions and other adverse effects or developments relating to geopolitical events or public health crises, may negatively affect the market price of our common stock, regardless of our actual operating performance. The realization of any of the above risks or any of a broad range of other risks, including those described in this prospectus supplement, the accompanying prospectus, our most recent Annual Report on Form 10-K and our subsequent Quarterly Reports on Form 10-Q, could have a significant and material adverse impact on the market price of our common stock.

There is no public market for the pre-funded warrants being offered in this offering.

There is no public trading market for the pre-funded warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to list the pre-funded warrants on the Nasdaq Capital Market or any other national securities exchange or nationally recognized trading system. Without an active trading market, the liquidity of the pre-funded warrants will be limited.

We will not receive a significant amount or any additional funds upon the exercise of the pre-funded warrants.

Each pre-funded warrant is exercisable for $0.0001 per share of common stock underlying such pre-funded warrant, which may be paid by way of a cashless exercise, in which the holder would receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the pre-funded warrant. Accordingly, we will not receive a significant amount of additional funds (if any) upon the exercise of the pre-funded warrants.

Except as otherwise provided in the pre-funded warrants, holders of pre-funded warrants purchased in this offering will have no rights as stockholders of common stock until such holders exercise their pre-funded warrants and acquire our common stock.

The pre-funded warrants offered in this offering do not confer any rights of common stock ownership on their holders, such as voting rights or the right to receive dividends (except as otherwise provided in the pre-funded warrants), but rather merely represent the right to acquire shares of our common stock at a fixed price. Specifically, a holder of a pre-funded warrants may exercise the right to acquire a share of common stock and pay an exercise price equal to $0.0001 per share. Upon exercise of the pre-funded warrants, the holders thereof will be entitled to exercise the rights of a holder of common stock only as to matters for which the record date occurs after the exercise date.

Significant holders or beneficial holders of our common stock may not be permitted to exercise pre-funded warrants that they hold.

A holder of a pre-funded warrant will not be entitled to exercise any portion of any pre-funded warrant which, upon giving effect to such exercise, would cause the aggregate number of shares of our common stock beneficially owned by the holder (together with its affiliates and other attribution parties, as defined under “Description of Pre-Funded Warrants—Exercise Limitations”) to exceed 19.99%, or if the purchaser elected prior to the issuance of pre-funded warrants to have the initial exercise limitation set at any of 4.99% or 9.99% of our outstanding common stock, such lower threshold, of the number of shares of our common stock that would be outstanding immediately after giving effect to the exercise. However, subject to certain limitations, any holder may increase or decrease such percentage to any other percentage not in excess of 19.99% upon at least 61 days’ prior notice from the holder to us. As a result, you may not be able to exercise your pre-funded warrants for shares of our common stock at a time when it would be financially beneficial for you to do so. In such circumstance you could seek to sell your pre-funded warrants to realize value, but you may be unable to do so in the absence of an established trading market for the pre-funded warrants.

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CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein, and any free writing prospectus that we have authorized for use in connection with this offering, contain forward-looking statements. All statements other than statements of historical facts contained in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein are forward-looking statements. These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements. This prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and therein also contain estimates and other statistical data made by independent parties and by us relating to market size and growth and other data about our industry. This data involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. In addition, projections, assumptions and estimates of our future performance and the future performance of the markets in which we operate are necessarily subject to a high degree of uncertainty and risk.

Although we believe that the expectations reflected in these forward-looking statements are reasonable, these statements relate to future events or our future operational or financial performance, and involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. Forward-looking statements in this prospectus supplement, the accompanying prospectus and the documents incorporated herein and therein include, but are not limited to, statements about:

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our ability to achieve and sustain profitability in the future;

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our strategies, prospects, plans, expectations or objectives of management for our future operations;

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estimates of our future expenses, revenues, capital requirements, cash runway, and our needs for additional financing;

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our estimates of and anticipated use of our existing cash and cash equivalents;

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the progress, scope or timing of the development of our product candidates;

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our expectations surrounding the potential safety, efficacy, and regulatory and clinical progress of our product candidates, including bempikibart, and our anticipated milestones, timing of anticipated registrational trials, and timing of data readouts;

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our ability to obtain and maintain regulatory approval of our product candidates;

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our ability to achieve and maintain market acceptance and adoption of our product candidates;

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the benefits that may be derived from any of our future products or the commercial or market opportunity with respect to any of our future products;

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our ability to maintain patent protection for our product candidates and protect our intellectual property rights;

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our ability to successfully compete against other companies developing similar products to ours;

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our anticipated operations, financial position, ability to raise capital to fund our operations, revenues, costs or expenses;

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our ability to retain our key executives and to attract and retain highly qualified personnel;

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our ability to successfully protect against cyber-attacks, security breaches and other disruptions to our information technology systems;

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our ability to establish and maintain an effective system of internal controls over financial reporting;

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the effect of unfavorable macroeconomic conditions or market volatility resulting from global economic conditions or geopolitical developments, including fluctuating interest rates and inflation and capital market disruptions, changes in governmental agencies, government shutdowns, international tariffs, trade protection measures, public health crises, economic sanctions and potential economic slowdowns or recessions, or similar events;

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our reliance on third parties in the supply and manufacture of our product candidates;

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the impact of applicable laws and regulations, whether in the U.S. or foreign jurisdictions, and any changes thereto;

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the impacts of changes in the policies or regulations of the U.S. Food and Drug Administration or comparable foreign regulatory authorities regarding development, approval, and marketing of products;

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our anticipated use of proceeds from this offering;

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the statements regarding our future economic conditions or performance, statements of belief and any statement of assumptions underlying any of the foregoing; and

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other risks and uncertainties, including those listed under the caption “Risk Factors.”

We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus supplement, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and you are cautioned not to unduly rely upon these statements.

We have included important factors in the cautionary statements included in this prospectus supplement, our most recent Annual Report on Form 10-K and our subsequent Quarterly Reports on Form 10-Q, particularly in the “Risk Factors” section, that could cause actual results or events to differ materially from the forward-looking statements that we make. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, collaborations, joint ventures or investments that we may make or into which we may enter.

You should read this prospectus supplement, the accompanying prospectus, our most recent Annual Report on Form 10-K and our subsequent Quarterly Reports on Form 10-Q and the documents that we reference herein and therein and have filed or incorporated by reference as exhibits thereto and to the registration statement of which this prospectus supplement and the accompanying prospectus are part, completely and with the understanding that our actual future results may be materially different from what we expect. We do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by law.

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USE OF PROCEEDS

We estimate that the net proceeds to us from this offering will be approximately $187.59 million (or approximately $215.79 million if the underwriters exercise their option to purchase additional shares of our common stock in full), after deducting underwriting discounts and commissions and estimated offering expenses payable by us. We will receive nominal proceeds, if any, from the exercise of the pre-funded warrants.

We currently intend to use the net proceeds from this offering, together with our existing cash and cash equivalents for working capital purposes including expenses related to research, clinical development and commercialization efforts including for supporting the advancement of bempikibart into future clinical trials.

We cannot specify with certainty all of the particular uses for the net proceeds to be received upon the completion of this offering. Due to uncertainties inherent in the product development process, it is difficult to estimate the exact amounts of the net proceeds that will be used for any particular purpose. We may use our existing cash and cash equivalents to fund our operations, either of which may alter the amount of net proceeds used for a particular purpose. In addition, the amount, allocation and timing of our actual expenditures will depend upon numerous factors, including the results of our research and development efforts, the timing and success of clinical trials and the timing of regulatory submissions. Accordingly, we will have broad discretion in using these proceeds.

Pending the uses described above, we plan to invest the net proceeds of this offering in short- and immediate-term, interest-bearing obligations, investment-grade instruments, certificates of deposit or direct or guaranteed obligations of the U.S. government.

The amounts and timing of our actual expenditures will depend on numerous factors, including the factors described under “Risk Factors” in this prospectus supplement, the accompanying prospectus and in the documents incorporated by reference herein and therein, as well as the amount of cash used in our operations. We may find it necessary or advisable to use the net proceeds for other purposes, and we will have broad discretion in the application of the net proceeds.

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DIVIDEND POLICY

We currently expect to retain all future earnings, if any, for use in the development, operation and expansion of our business. Any determination to pay cash dividends in the future will depend upon, among other things, our results of operations, plans for expansion, tax considerations, available net profits and reserves, limitations under law, financial condition, capital requirements and other factors that our board of directors considers to be relevant.

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DILUTION

If you invest in our common stock or pre-funded warrants in this offering, your ownership interest will be diluted to the extent of the difference between the price per share you pay in this offering and the net tangible book value per share of our common stock immediately after this offering. Our net tangible book value of our common stock as of March 31, 2026 was approximately $46,313,000, or approximately $3.17 per share of common stock based upon 14,629,463 shares outstanding. Net tangible book value per share is equal to our total tangible assets, less our total liabilities, divided by the total number of shares of common stock outstanding as of March 31, 2026.

After giving effect to (i) the PIPE Shares Issuance, (ii) the ATM Issuance and (iii) the sale by us of shares of common stock at the public offering price of $18.25 per share of common stock and pre-funded warrants at $18.2499 per pre-funded warrant (which equals the public offering price of the common stock at which shares of our common stock are being sold to the public in this offering less the $0.0001 per share exercise price of each such pre-funded warrant) (excluding shares of common stock issuable upon exercise of the pre-funded warrants, any proceeds which may be received upon exercise of the pre-funded warrants or any resulting accounting associated with the exercise of the pre-funded warrants), and after deducting underwriting discounts and commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of March 31, 2026 would have been approximately $300,750,022, or $10.12 per share of common stock. This represents an immediate increase in net tangible book value of $5.34 per share to our existing stockholders and an immediate dilution in net tangible book value of $8.13 per share of common stock issued to the investors participating in this offering.

The following table illustrates this calculation on a per share basis.


Public offering price per share			$	18.25
Net tangible book value per share as of March 31, 2026	$	3.17
Increase in net tangible book value per share attributable to the PIPE Shares Issuance and the ATM Issuance		1.61

As adjusted net tangible book value per share as of March 31, 2026		4.78
Increase in net tangible book value per share attributable to sale of shares of common stock and pre-funded warrants in this offering	$	5.34

As adjusted net tangible book value per share after this offering				10.12

Dilution in net tangible book value per share to the investors participating in this offering			$	8.13

If holders of pre-funded warrants exercise the pre-funded warrants offered hereby, the as adjusted net tangible book value per share of our common stock after giving effect to the PIPE Shares Issuance, the ATM Issuance and this offering would be $8.68 per share, and the dilution in net tangible book value per share to investors participating in this offering would be $9.57 per share.

If the underwriters exercise their option to purchase additional 1,643,835 shares of our common stock in full at the public offering price of $18.25 per share (and excluding shares of common stock issued and any proceeds received upon exercise of the pre-funded warrants or any resulting accounting associated with the exercise of the pre-funded warrants), the as adjusted net tangible book value after giving effect to the PIPE Shares Issuance, the ATM Issuance and this offering would be approximately $10.49 per share, representing an increase in net tangible book value of $5.71 per share to existing stockholders and dilution of $7.76 per share to investors participating in this offering.

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The above discussion and table are based on 14,629,463 shares of our common stock outstanding as of March 31, 2026 and after giving effect to the PIPE Shares Issuance and the ATM Issuance, and excludes:

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2,264,082 shares of common stock issuable upon the exercise of stock options outstanding as of March 31, 2026 at a weighted-average exercise price of $2.86 per share;

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599,326 shares of common stock issuable upon vesting and settlement of restricted stock units outstanding as of March 31, 2026;

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2,130,724 shares of common stock available for future issuance under our 2024 Plan as of March 31, 2026;

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371,393 shares of common stock available for future issuance under our 2024 ESPP as of March 31, 2026;

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18,144 shares of common stock issuable upon the exercise of outstanding warrants as of March 31, 2026;

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1,025,654 shares of common stock issuable upon the exercise of outstanding pre-funded warrants as of March 31, 2026; and

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150,000 shares of common stock issuable upon the exercise of outstanding pre-funded warrants issued as part of the 2026 PIPE.

To the extent that outstanding stock options are exercised, new stock options are issued, unvested restricted stock units are vested and settled, outstanding warrants or pre-funded warrants are exercised or we issue additional shares of common stock in the future, there will be further dilution to new investors. In addition, we may choose to raise additional capital because of market conditions or strategic considerations, even if we believe that we have sufficient funds for our current or future operating plans. If we raise additional capital through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders. As of the date of this prospectus supplement, $75 million of shares of common stock remain available for sale under the Sales Agreement. There can be no assurance as to whether or, if so, how many or when, additional shares will be issued by us thereunder.

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DESCRIPTION OF PRE-FUNDED WARRANTS

The following summary of certain terms and provisions of the pre-funded warrants that are being offered hereby is not complete and is subject to, and qualified in its entirety by, the provisions of the pre-funded warrants the form of which will be filed with the SEC and incorporated by reference into the registration statement of which this prospectus supplement and the accompanying base prospectus form a part. Prospective investors should carefully review the terms and provisions of the form of pre-funded warrants for a complete description of the terms and conditions of the pre-funded warrants.

Duration and Exercise Price. Each pre-funded warrant offered hereby has an initial exercise price per share equal to $0.0001. The pre-funded warrants are immediately exercisable upon issuance and may be exercised at any time until they are exercised in full.

Exercisability. The pre-funded warrants will be exercisable, at the option of the holder, in whole or in part by delivering to us a duly executed exercise notice and, at any time a registration statement registering the issuance of shares of common stock underlying the pre-funded warrants under the Securities Act is effective and available for the issuance of such shares, or an exemption from registration under the Securities Act is available for the issuance of such shares, by payment in full in immediately available funds for the number of shares of common stock purchased upon such exercise.

Cashless Exercise. The pre-funded warrants may also be exercised, in whole or in part, at such time by means of a cashless exercise, in which case the holder would receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the pre-funded warrant.

Exercise Limitations. A holder will not have the right to exercise any portion of the pre-funded warrants if the holder (together with its affiliates) would beneficially own in excess of 4.99% or 9.99%, as elected by the holder, of the number of our shares of common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants. However, any holder may increase or decrease such percentage, but in no event may such percentage be increased to more than 19.99%, provided that any increase will not be effective until the 61st day after such election.

Exercise Price Adjustment. The exercise price and the number of shares issuable upon exercise of the pre-funded warrants are subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our shares of common stock. In no event may the exercise price be adjusted below the par value of our common stock then in effect.

Transferability. Subject to applicable laws, the pre-funded warrants may be offered for sale, sold, transferred or assigned without our consent.

Exchange Listing. There is no established trading market for the pre-funded warrants and we do not expect a market to develop. In addition, we do not intend to list the pre-funded warrants on any national securities exchange or other trading market.

Fundamental Transactions. In the event of any fundamental transaction, as described in the pre-funded warrants and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer or exchange offer, or reclassification of our shares of common stock, then upon any subsequent exercise of a pre-funded warrant, the holder will have the right to receive as alternate consideration, at the option of the holder, for each share of common stock that would have been issuable upon such exercise immediately prior to the occurrence of such fundamental transaction (without regard to any beneficial ownership limitation), the number of shares of common stock of the successor or acquiring corporation of our company, if it is the surviving corporation, and any additional consideration receivable upon or as a result of such transaction by a holder of the number of shares of common stock for which the pre-funded warrant is exercisable immediately prior to such fundamental transaction.

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Rights as a Stockholder. Except as otherwise provided in the pre-funded warrants or by virtue of such holder’s ownership of our common stock, the holder of a pre-funded warrant will not have the rights or privileges of a holder of our common stock, including any voting rights or rights to receive dividends, until the holder exercises the pre-funded warrant.

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MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES TO NON-U.S. HOLDERS

The following discussion is a summary of the material U.S. federal income tax considerations applicable to non-U.S. holders (as defined below) with respect to their purchase, ownership and disposition of shares of our common stock and pre-funded warrants issued pursuant to this offering. For purposes of this discussion, a non-U.S. holder means a beneficial owner of our common stock or pre-funded warrants that is for U.S. federal income tax purposes, neither an entity or arrangement treated as a partnership nor:

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an individual who is a citizen or resident of the United States;

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a corporation, or other entity treated as a corporation for U.S. federal income tax purposes, created or organized in or under the laws of the United States, any state thereof, or the District of Columbia;

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an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

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a trust if (1) a U.S. court is able to exercise primary supervision over the administration of the trust and one or more U.S. persons has authority to control all substantial decisions of the trust or (2) the trust has a valid election in effect under applicable U.S. Treasury Regulations to be treated as a U.S. person.

This discussion does not address the tax treatment of partnerships or other entities that are pass-through entities for U.S. federal income tax purposes or persons that hold their common stock or pre-funded warrants through partnerships or other pass-through entities. If an entity treated as a partnership for U.S. federal income tax purposes holds our common stock or pre-funded warrants, the tax treatment of a partner in the partnership will generally depend on the status of the partner, the activities of the partnership and certain determinations made at the partner level. A partner in a partnership or other pass-through entity that will hold our common stock or pre-funded warrants should consult his, her or its tax advisor regarding the tax consequences of acquiring, holding and disposing of our common stock or pre-funded warrants through a partnership or other pass-through entity, as applicable.

This discussion is based on current provisions of the U.S. Internal Revenue Code of 1986, as amended (the “Code”), U.S. Treasury Regulations promulgated thereunder, administrative rulings and judicial decisions, all as in effect as of the date of this prospectus supplement and all of which are subject to change or to differing interpretation, possibly with retroactive effect. Any such change or differing interpretation could alter the tax consequences to non-U.S. holders described in this prospectus supplement. There can be no assurance that the Internal Revenue Service (the “IRS”) will not challenge one or more of the tax consequences described herein. We assume in this discussion that a non-U.S. holder holds shares of our common stock or pre-funded warrants as a capital asset within the meaning of Section 1221 of the Code (generally, property held for investment).

This discussion does not address all aspects of U.S. federal income taxation that may be relevant to a particular non-U.S. holder in light of that non-U.S. holder’s individual circumstances nor does it address U.S. state, local or non-U.S. taxes, the alternative minimum tax, the Medicare contribution tax on net investment income, the special tax accounting rules under Section 451(b) of the Code, the rules regarding qualified small business stock within the meaning of Section 1202 of the Code or any aspect of any U.S. federal tax other than the income tax. This discussion also does not consider any specific facts or circumstances that may apply to a non-U.S. holder and does not address the special tax rules applicable to particular non-U.S. holders, such as:

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insurance companies;

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tax-exempt or governmental organizations;

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financial institutions;

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brokers or dealers in securities;

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regulated investment companies;

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pension plans;

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“controlled foreign corporations,” “passive foreign investment companies,” and corporations that accumulate earnings to avoid U.S. federal income tax;

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“qualified foreign pension funds” as defined in Section 897(l)(2) of the Code and entities all of the interests of which are held by one or more qualified foreign pension funds;

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partnerships or other entities or arrangements treated as partnerships for U.S. federal income tax purposes (and partners and investors therein);

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persons deemed to sell our common stock under the constructive sale provisions of the Code;

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persons that hold our common stock as part of a straddle, hedge, conversion transaction, synthetic security or other integrated investment;

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persons who hold or receive our common stock pursuant to the exercise of any employee stock option or otherwise as compensation; and

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U.S. expatriates.

This discussion is for general information only and is not tax advice. Accordingly, all prospective non-U.S. holders of our common stock or pre-funded warrants should consult their tax advisors with respect to the U.S. federal, state, local and non-U.S. tax consequences of the purchase, ownership and disposition of our common stock or pre-funded warrants, including the consequences of any proposed changes in applicable laws.

Characterization of the pre-funded warrants for tax purposes

Although the characterization of the pre-funded warrants for U.S. federal income tax purposes is not entirely clear, because the exercise price of the pre-funded warrants is a nominal amount, we intend to treat the pre-funded warrants as our common stock for U.S. federal income tax purposes and a holder of pre-funded warrants should generally expect to be taxed in the same manner as a holder of common stock as described below. Accordingly, for U.S. federal income tax purposes, no gain or loss should be recognized upon the exercise of a pre-funded warrant (except to the extent of cash received in lieu of a fractional share, if any), and upon exercise, the holding period of the share of common stock received would include the holding period of the pre-funded warrant. Similarly, the tax basis of a share of common stock received upon exercise of a pre-funded warrant should include the tax basis of the pre-funded warrant increased by the exercise price of $0.0001 per share. The balance of this discussion assumes that the characterization described above is respected for U.S. federal income tax purposes.

Our position with respect to the characterization of pre-funded warrants is not binding on the IRS and the IRS may successfully challenge the treatment of the pre-funded warrants to acquire our common stock and, if so, the tax considerations to a holder with respect to an investment in our pre-funded warrants could differ from the description below. Each holder should consult its tax advisor regarding the characterization of pre-funded warrants for U.S. federal income tax purposes, and the consequences of an investment in the pre-funded warrants based on such holder’s own particular facts and circumstances.

Distributions on Our Common Stock and Pre-Funded Warrants

As described in the “Dividend Policy” section above, we do not anticipate paying any cash dividends on our capital stock or pre-funded warrants in the foreseeable future. Distributions, if any, on our common stock or pre- funded warrants will generally constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. If a distribution exceeds our current and accumulated earnings and profits, the excess will be treated as a tax-free return of the non-U.S. holder’s investment, up to such holder’s tax basis in the common stock or pre-funded warrants. Any remaining excess will be treated as capital gain, subject to the tax treatment described below in

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“Gain on Sale or Other Taxable Disposition of Our Common Stock and Pre-Funded Warrants.” Any such distributions will also be subject to the discussions below in the sections titled “Backup Withholding and Information Reporting” and “FATCA.”

A non-U.S. holder of a pre-funded warrant is entitled to receive certain distributions paid with respect to common stock prior to the exercise of the pre-funded warrant and, in such case, would be taxed in the same manner as a non-U.S. holder of common stock that receives such a distribution. However, under certain circumstances, it is possible for the distributions to be held in abeyance for the non-U.S. holder until a pre-funded warrant is exercised or the ownership limitations (described under “Description of Pre-Funded Warrants”) would not be exceeded, at which time such non-U.S. holder shall be entitled to receive distributions. It is possible that such entitlement to distributions could cause the declaration of a distribution on our common stock to be currently taxable to non-U.S. holders of pre-funded warrants, including under the principles governing Section 305 of the Code, even though the holders will not receive such distributions until a future date. Additionally, it is possible that other adjustments to the terms of the pre-funded warrants could be considered a constructive distribution under Section 305 of the Code. A holder of a pre-funded warrant should consult its tax advisor regarding the tax treatment of any distribution with respect to such pre-funded warrant that is held in abeyance in connection with any applicable limitation on the holder’s beneficial ownership of our common stock and the tax treatment of any other adjustments to the pre-funded warrants.

Subject to the discussion in the following two paragraphs in this section, dividends paid to a non-U.S. holder generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the U.S. and such holder’s country of residence.

Dividends that are treated as effectively connected with a trade or business conducted by a non-U.S. holder within the U.S. and, if an applicable income tax treaty so provides, that are attributable to a permanent establishment or a fixed base maintained by the non-U.S. holder within the U.S., are generally exempt from the 30% withholding tax if the non-U.S. holder satisfies applicable certification and disclosure requirements. To obtain this exemption, a non-U.S. holder must generally provide us with a properly executed IRS Form W-8ECI certifying such exemption. However, such U.S. effectively connected income, net of specified deductions and credits, is generally taxed at the regular U.S. federal income tax rates applicable to U.S. persons. Any U.S. effectively connected income received by a non-U.S. holder that is a corporation may also, under certain circumstances, be subject to an additional “branch profits tax” at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the U.S. and such holder’s country of residence.

A non-U.S. holder of our common stock or pre-funded warrants who claims the benefit of an applicable income tax treaty between the U.S. and such holder’s country of residence generally will be required to provide a properly executed IRS Form W-8BEN or W-8BEN-E (or other applicable or successor form) to the applicable withholding agent and satisfy any other applicable requirements. Any documentation provided to an applicable withholding agent may need to be updated in certain circumstances. Non-U.S. holders are urged to consult their tax advisors regarding their entitlement to benefits under a relevant income tax treaty. A non-U.S. holder that is eligible for a reduced rate of U.S. withholding tax under an income tax treaty may obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim with the IRS.

Gain on Sale or Other Taxable Disposition of Our Common Stock and Pre-Funded Warrants

Subject to the discussions below under “Backup Withholding and Information Reporting” and “FATCA,” a non-U.S. holder generally will not be subject to any U.S. federal income or withholding tax on any gain realized upon such holder’s sale or other taxable disposition of shares of our common stock or pre-funded warrants unless:

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the gain is effectively connected with the non-U.S. holder’s conduct of a U.S. trade or business and, if an applicable income tax treaty so provides, is attributable to a permanent establishment or a fixed base

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maintained by such non-U.S. holder in the U.S., in which case the non-U.S. holder generally will be taxed on a net income basis at the regular U.S. federal income tax rates applicable to U.S. persons and, if the non-U.S. holder is a foreign corporation, the branch profits tax described above in “Distributions on Our Common Stock and Pre-Funded Warrants” also may apply;

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the non-U.S. holder is a nonresident alien individual who is present in the U.S. for a period or periods aggregating 183 days or more in the taxable year of the disposition and certain other conditions are met, in which case the non-U.S. holder will be subject to a 30% tax (or such lower rate as may be specified by an applicable income tax treaty between the U.S. and such holder’s country of residence) on the net gain derived from the sale or disposition, which may be offset by certain U.S. source capital losses of the non-U.S. holder, if any (even though the individual is not considered a resident of the U.S.), provided that the non-U.S. holder has timely filed U.S. federal income tax returns with respect to such losses; or

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we are, or have been, at any time during the five-year period preceding such sale or other taxable disposition (or the non-U.S. holder’s holding period, if shorter) a U.S. real property holding corporation, unless our common stock is regularly traded on an established securities market at the time of the sale or disposition and the non-U.S. holder holds no more than 5% of our outstanding common stock, directly or indirectly, actually or constructively, during the shorter of the 5-year period ending on the date of the disposition or the period that the non-U.S. holder held our common stock. Special rules may apply to a holder of a pre-funded warrant. If we are or were a U.S. real property holding corporation during the relevant period and the foregoing exception does not apply, the non-U.S. holder generally will be taxed on its net gain derived from the disposition at the regular U.S. federal income tax rates applicable to U.S. persons. Generally, a corporation is a U.S. real property holding corporation only if the fair market value of its U.S. real property interests equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus its other assets used or held for use in a trade or business. Although there can be no assurance, we do not believe that we are, or have been, a U.S. real property holding corporation, or that we are likely to become one in the future. No assurance can be provided that our common stock will be regularly traded on an established securities market for purposes of the rules described above.

Backup Withholding and Information Reporting

We must report annually to the IRS and to each non-U.S. holder the gross amount of the distributions on our common stock or pre-funded warrants paid to such holder and the tax withheld, if any, with respect to such distributions. Non-U.S. holders may have to comply with specific certification procedures to establish that the holder is not a U.S. person in order to avoid backup withholding at the applicable rate with respect to dividends on our common stock or pre-funded warrants. Generally, a non-U.S. holder will comply with such procedures if it provides a properly executed IRS Form W-8BEN or W-8BEN-E (or other applicable Form W-8), or otherwise meets documentary evidence requirements for establishing that it is a non-U.S. holder, or otherwise establishes an exemption. Dividends paid to non-U.S. holders subject to withholding of U.S. federal income tax, as described above in “Distributions on Our Common Stock and Pre-Funded Warrants,” generally will be exempt from U.S. backup withholding.

Information reporting and backup withholding will generally apply to the proceeds of a disposition of our common stock or pre-funded warrants by a non-U.S. holder effected by or through the U.S. office of any broker, U.S. or foreign, unless the holder certifies its status as a non-U.S. holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to a non-U.S. holder where the transaction is effected outside the U.S. through a non-U.S. office of a broker. However, for information reporting purposes, dispositions effected through a non-U.S. office of a broker with substantial U.S. ownership or operations generally will be treated in a manner similar to dispositions effected through a U.S. office of a broker. Non-U.S. holders should consult their tax advisors regarding the application of the information reporting and backup withholding rules to them. Copies of

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information returns may be made available to the tax authorities of the country in which the non-U.S. holder resides or is incorporated under the provisions of a specific treaty or agreement. Backup withholding is not an additional tax. Any amounts withheld under the backup withholding rules from a payment to a non-U.S. holder can be refunded or credited against the non-U.S. holder’s U.S. federal income tax liability, if any, provided that an appropriate claim is filed with the IRS in a timely manner.

FATCA

The Foreign Account Tax Compliance Act (“FATCA”) generally imposes a U.S. federal withholding tax at a rate of 30% on payments of dividends on our common stock or pre-funded warrants paid to a foreign entity unless (i) if the foreign entity is a “foreign financial institution,” such foreign entity undertakes certain due diligence, reporting, withholding, and certification obligations, (ii) if the foreign entity is not a “foreign financial institution,” such foreign entity identifies certain of its U.S. investors, if any, or (iii) the foreign entity is otherwise exempt under FATCA. Such withholding may also apply to gross proceeds from the sale or other disposition of our common stock or pre-funded warrants, although under proposed U.S. Treasury Regulations, no withholding would apply to such gross proceeds. The preamble to the proposed regulations specifies that taxpayers (including withholding agents) are permitted to rely on the proposed regulations pending finalization. Under certain circumstances, a non-U.S. holder may be eligible for refunds or credits of the tax. An intergovernmental agreement between the U.S. and an applicable foreign country may modify the requirements described in this paragraph. Non-U.S. holders should consult their tax advisors regarding the possible implications of this legislation on their investment in our common stock or pre-funded warrants and the entities through which they hold our common stock or pre-funded warrants, including, without limitation, the process and deadlines for meeting the applicable requirements to prevent the imposition of the 30% withholding tax under FATCA.

THIS DISCUSSION IS NOT INTENDED TO BE TAX ADVICE. PROSPECTIVE INVESTORS SHOULD CONSULT THEIR TAX ADVISORS REGARDING THE PARTICULAR U.S. FEDERAL INCOME TAX CONSEQUENCES TO THEM OF THE PURCHASE, OWNERSHIP, AND DISPOSITION OF OUR COMMON STOCK, AS WELL AS ANY TAX CONSEQUENCES ARISING UNDER ANY STATE, LOCAL, OR NON-U.S. TAX LAWS AND ANY U.S. FEDERAL NON-INCOME TAX LAWS.

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UNDERWRITERS

Under the terms and subject to the conditions in an underwriting agreement dated the date of this prospectus supplement, the underwriters named below, for whom Morgan Stanley & Co. LLC, Jefferies LLC, Cantor Fitzgerald & Co. and Oppenheimer & Co. Inc. are acting as representatives, have severally agreed to purchase, and we have agreed to sell to them, severally, the number of shares of common stock and pre-funded warrants indicated below:


Name	Number of Shares		Number of Pre-Funded Warrants
Morgan Stanley & Co. LLC		2,169,863		1,775,343
Jefferies LLC		1,717,809		1,405,479
Cantor Fitzgerald & Co.		1,265,754		1,035,616
Oppenheimer & Co. Inc.		572,603		468,493
H.C. Wainwright & Co., LLC		301,370		246,575

Total:		6,027,399		4,931,506

The underwriters and the representatives are collectively referred to as the “underwriters” and the “representatives,” respectively. The underwriters are offering the shares of common stock and pre-funded warrants subject to their acceptance of the shares and pre-funded warrants from us and subject to prior sale. The underwriting agreement provides that the obligations of the several underwriters to pay for and accept delivery of the shares of common stock and pre-funded warrants offered by this prospectus supplement are subject to the approval of certain legal matters by their counsel and to certain other conditions precedent. The underwriters are obligated to take and pay for all of the shares of common stock and pre-funded warrants offered by this prospectus supplement if any such shares and pre-funded warrants are taken. However, the underwriters are not required to take or pay for the shares of common stock covered by the underwriters’ option to purchase additional shares described below.

The underwriters initially propose to offer part of the shares of common stock and pre-funded warrants directly to the public at the offering price listed on the cover page of this prospectus supplement and part to certain dealers at a price that represents a concession not in excess of $0.6570 per share or per pre-funded warrant under the public offering price. After the initial offering of the shares of common stock and pre-funded warrants, the offering price and other selling terms may from time to time be varied by the representatives.

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus supplement, to purchase up to 1,643,835 additional shares of common stock at the public offering price listed on the cover page of this prospectus supplement, less underwriting discounts and commissions. To the extent the option is exercised, each underwriter will become obligated, subject to certain conditions, to purchase about the same percentage of the additional shares of common stock as the number listed next to the underwriter’s name in the preceding table bears to the total number of shares of common stock listed next to the names of all underwriters in the preceding table.

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The following table shows the per share, per pre-funded warrant and total public offering price, underwriting discounts and commissions, and proceeds before expenses to us. These amounts are shown assuming both no exercise and full exercise of the underwriters’ option to purchase up to an additional 1,643,835 shares of common stock.


			Per Pre-Funded Warrant		Total
	Per Share		Per Pre-Funded Warrant		No Exercise		Full Exercise
Public offering price	$	18.2500	$	18.2499	$	199,999,523.0994	$	229,999,511.8494
Underwriting discounts and commissions to be paid by us	$	1.0950	$	1.0950	$	12,000,000.9750	$	13,800,000.3000

Proceeds, before expenses, to us	$	17.1550	$	17.1549	$	187,999,522.1244	$	216,199,511.5494

The estimated offering expenses payable by us, exclusive of the underwriting discounts and commissions, are approximately $412,500. We have agreed to reimburse the underwriters for expenses relating to clearance of this offering with the Financial Industry Regulatory Authority up to $15,000.

Our common stock is listed on The Nasdaq Capital Market under the trading symbol “QTTB.” We do not intend to list the pre-funded warrants on The Nasdaq Capital Market or any other national securities exchange or nationally recognized trading system.

We, all of our directors and officers and certain of our affiliates have agreed that, without the prior written consent of Morgan Stanley & Co. LLC, Jefferies LLC and Cantor Fitzgerald & Co. on behalf of the underwriters, we and they will not, and will not publicly disclose an intention to, during the period ending immediately after the close of trading day occurring on the 45th day after the date of this prospectus supplement or, if such day is not a trading day, ending immediately after the close of the last trading day immediately preceding such day (such applicable period, the “restricted period”):

•

offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of common stock or any securities convertible into or exercisable or exchangeable for shares of common stock; or

•

enter into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of the shares of common stock.

In addition, we have agreed that, without the prior written consent of Morgan Stanley & Co. LLC, Jefferies LLC and Cantor Fitzgerald & Co. on behalf of the underwriters, we will not, during the restricted period, file or confidentially submit any registration statement with the Securities and Exchange Commission relating to the offering of any shares of common stock or any securities convertible into or exercisable or exchangeable for shares of common stock. In addition, our directors and officers and certain of our affiliates agree that, without the prior written consent of Morgan Stanley & Co. LLC, Jefferies LLC and Cantor Fitzgerald & Co. on behalf of the underwriters, such other person will not, during the restricted period, make any demand for, or exercise any right with respect to, the registration of any shares of common stock or any security convertible into or exercisable or exchangeable for common stock.

The restrictions described above do not apply to us with respect to:

•

the shares of common stock and pre-funded warrants to be sold to the underwriters in the offering and the issuance of shares of common stock upon any exercise of such pre-funded warrants;

•

the issuance by us of shares of common stock upon the exercise of an option or warrant or the conversion of a security outstanding as of the date of the underwriting agreement and as described in this prospectus supplement and the registration statement of which this prospectus supplement forms a part;

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•

the grants of options, restricted stock or other equity awards and the issuance of shares of common stock or securities convertible into or exercisable for shares of common stock (whether upon the exercise of stock options or otherwise) to our employees, officers, directors, advisors, or consultants pursuant to the terms of an employee benefit plan in effect as of the date of the underwriting agreement and as described in this prospectus supplement and the registration statement of which this prospectus supplement forms a part, provided that we shall cause each newly appointed director or executive officer that is a recipient of such shares of common stock or other securities of the Company to enter into an agreement similar to other directors and officers not to engage in certain transactions during the restricted period;

•

the filing of a registration statement on Form S-8 to register shares of common stock issuable pursuant to any employee benefit plans, qualified stock option plans or other employee compensation plans, described in this prospectus supplement and the registration statement of which this prospectus supplement forms a part;

•

the issuance of shares of common stock, or any securities convertible into, or exercisable or exchangeable for shares of common stock, or the entrance into an agreement to issue shares of common stock or any securities convertible into, or exercisable or exchangeable for shares of common stock, in connection with any merger, joint venture, strategic alliance, commercial or other collaborative transaction or the acquisition or license of the business, property, technology or other assets of another individual or entity or the assumption of an employee benefit plan in connection with a merger or acquisition, other than for capital raising purposes, provided that the aggregate number of shares of common stock or any securities convertible into, or exercisable or exchangeable for shares of common stock that we may issue or agree to issue pursuant to this clause shall not exceed 5% of our total outstanding share capital immediately following the issuance of shares of common stock and pre-funded warrants to be sold to the underwriters in the offering and the issuance of shares of common stock upon any exercise of such pre-funded warrants, and provided, further, that the recipients of any such shares of common stock and securities issued pursuant to this clause during the restricted period described above shall enter into an agreement similar to other directors and officers not to engage in certain transactions during the restricted period;

•

facilitating the establishment of a trading plan on behalf of any of our shareholders, officers or directors pursuant to Rule 10b5-1 under the Exchange Act, for the transfer of shares of common stock, provided that (i) such plan does not provide for the transfer of common stock during the restricted period and (ii) to the extent a public announcement or filing under the Exchange Act, if any, is required of or voluntarily made by us regarding the establishment of such plan, such announcement or filing shall include a statement to the effect that no transfer of common stock may be made under such plan during the restricted period;

•

the issuance of shares of common stock pursuant to any non-employee director stock plan or dividend reinvestment plan referred to in this prospectus supplement and the registration statement of which this prospectus supplement forms a part; or

•

the filing of a registration statement covering the resale of certain securities issued by us in the 2026 PIPE, pursuant to the registration rights agreement, dated as of May 26, 2026, among us and the several investors signatory thereto.

The restrictions described above do not apply to our directors, officers and certain of our affiliates with respect to:

•

transactions relating to shares of common stock or other securities acquired (i) from the underwriters in the offering described in this prospectus supplement or (ii) in open market transactions after the completion of this offering, provided that no public report or filing with the Securities and Exchange Commission or otherwise is required or voluntarily made during the restricted period in connection with subsequent sales of common stock or other securities acquired in this offering or such open market or other transactions (other than (1) Schedule 13 filings filed with the SEC, and (2) any Form 4

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or Form 5 required to be filed under the Exchange Act if the party subject to the lock-up restrictions is subject to Section 16 reporting under the Exchange Act and indicating by footnote disclosure or otherwise the nature of the transaction and that such securities were acquired from the underwriters in this offering or in open market transactions after completion of the offering);

•

transfers, dispositions or distributions of shares of common stock or any security convertible into common stock as: (i) a bona fide gift, including, without limitation, to a charitable organization or educational institution, or for bona fide estate planning purposes, (ii) by will, testamentary document or intestacy, (iii) by operation of law, such as pursuant to a qualified domestic order, divorce settlement, divorce decree or separation agreement, (iv) pursuant to an order of a court or regulatory agency having jurisdiction over the party subject to the lock-up restrictions, (v) to any corporation, partnership, limited liability company or other entity of which the party subject to the lock-up restrictions or the immediate family of such party (as defined in FINRA Rule 5130(i)(5)) are the legal and beneficial owner of all of the outstanding equity securities or similar interests, (vi) to any nominee or custodian of a person or entity to whom a disposition or transfer would be permissible under clauses (i) through (v) above, (vii) to any member of the immediate family of the party subject to the lock-up restrictions or to any trust, partnership, limited liability company or other entity for the direct or indirect benefit of the party subject to the lock-up restrictions and/or any member of the immediate family of such party, or if the party subject to the lock-up restrictions is a trust, to a trustor or beneficiary of the trust or to the estate of the beneficiary of such trust or (viii) to us upon the death, disability or termination of employment or other service relationship of the party subject to the lock-up restrictions with us; provided that such common stock was issued to such party pursuant to an agreement or equity award granted pursuant to an employee benefit plan, option, warrant or other right disclosed in this prospectus supplement;

•

if the party subject to the lock-up restrictions is not an individual, distributions of shares of common stock or any security convertible into or exercisable or exchangeable for common stock to: (i) another corporation, partnership, limited liability company or other business entity that is a subsidiary or an affiliate (as defined in Rule 405 promulgated under the Securities Act, and including the subsidiaries of the party subject to the lock-up restrictions) of the party subject to the lock-up restrictions, or to any investment fund or other entity controlling, controlled by, managing or managed by or under common control or management with the party subject to the lock-up restrictions or affiliates of such party (including, for the avoidance of doubt, where such party is a partnership, to its general partner or a successor partnership or fund, or any other funds managed by such partnership), or (ii) as part of a distribution to limited partners, limited liability company members, general partners, members, beneficiaries, stockholders of the party subject to the lock-up restrictions or holders of similar equity interests in such party or to the estate of any such limited partners, limited liability company members, general partners, members, beneficiaries, stockholders or equityholders;

•

facilitating the establishment of a trading plan on behalf of any of our shareholders, officers or directors pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of common stock, provided that (i) such plan does not provide for the transfer of common stock during the restricted period and (ii) to the extent a public announcement or filing under the Exchange Act, if any, is required of or voluntarily made by or on behalf of the party subject to the lock-up restrictions or us regarding the establishment of such plan, such announcement or filing shall include a statement to the effect that no transfer of common stock may be made under such plan during the restricted period;

•

securities transferred to us pursuant to the vesting, settlement or exercise of restricted stock units, restricted stock, options, warrants or other rights to purchase common stock (including, in each case, by way of “net” or “cashless” exercise), including for the payment of exercise price and tax and remittance payments due as a result of the vesting, settlement or exercise of such restricted stock units, restricted stock, options, warrants or rights); provided that (1) any such common stock received upon such exercise, vesting or settlement shall be subject to the terms of the lock-up agreement; (2) any filing under the Exchange Act required to be made during the restricted period shall indicate in the footnotes

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thereto that the filing relates to circumstances described in this clause; (3) the party subject to the lock-up restrictions does not otherwise voluntarily effect any public filing or report regarding such transfers; and (4) any such restricted stock units, restricted stock, options, warrants or rights are held by the party subject to the lock-up restrictions pursuant to an agreement or equity award granted under a stock incentive plan or other equity award plan, each of which is disclosed in this prospectus supplement;

•

(i) transfers of common stock or any security convertible into or exercisable or exchangeable for common stock pursuant to a bona fide third-party tender offer for shares of our capital stock made to all holders of our securities, merger, consolidation or other similar transaction approved by our board of directors the result of which is that any person (as defined in Section 13(d)(3) of the Exchange Act), or group of persons, other than us, becomes the beneficial owner (as defined in Rules 13d-3 and 13d-5 of the Exchange Act) of more than 50% of the total voting power of our voting stock and (ii) entry into any lock-up, voting or similar agreement pursuant to which the party subject to the lock-up restrictions may agree to transfer, sell, tender or otherwise dispose of common stock or such other securities in connection with a transaction described in (i) above; provided that in the event that such change of control transaction is not completed, the common stock (or any security convertible into or exercisable or exchangeable for common stock) owned by the party subject to the lock-up restrictions shall remain subject to the restrictions contained in the lock-up agreement; or

•

shares of common stock or securities convertible into or exercisable or exchangeable for common stock transferred in “sell to cover” or similar open market transactions during the restricted period to satisfy any exercise price or tax withholding obligations (up to the amount required for such satisfaction) as a result of the vesting, exercise or settlement of restricted stock units, restricted stock, options, warrants or other rights to purchase or otherwise acquire common stock or any security convertible into or exercisable or exchangeable for common stock; provided that, any such shares of common stock retained by the party subject to the lock-up restrictions after giving effect to this provision shall remain subject to the restrictions contained in the lock-up agreement.

provided that in the case of any transfer or distribution pursuant to bullets 2 or 3 above, (i) each donee, devisee, trustee, distributee or transferee, as the case may be, shall sign and deliver a lock-up agreement substantially in the form of the lock-up agreement described above, (ii) any such transfer shall not involve a disposition for value, (iii) such transfers are not required to be reported during the restricted period in a filing with the SEC under Section 16(a) of the Exchange Act on Form 4 or Form 5 (except, in the case of a transfer or other disposition pursuant to clauses (i) through (iv) of bullet 2 above, any filing, if required, shall indicate in the footnotes thereto that the filing relates to circumstances described in the relevant clause) and (D) the party subject to the lock-up restrictions does not otherwise voluntarily effect any public filing or report regarding such transfers.

Morgan Stanley & Co. LLC, Jefferies LLC and Cantor Fitzgerald & Co., in their sole discretion, may release the common stock and other securities subject to the lock-up agreements described above in whole or in part at any time.

In order to facilitate the offering of the common stock and pre-funded warrants, the underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the common stock. Specifically, the underwriters may sell more shares than they are obligated to purchase under the underwriting agreement, creating a short position. A short sale is covered if the short position is no greater than the number of shares available for purchase by the underwriters under the option to purchase additional shares. The underwriters can close out a covered short sale by exercising the option to purchase additional shares or purchasing shares in the open market. In determining the source of shares to close out a covered short sale, the underwriters will consider, among other things, the open market price of shares compared to the price available under the option. The underwriters may also sell shares in excess of the option, creating a naked short position. The underwriters must close out any naked short position by purchasing shares in the open market. A naked short position is more likely to be created

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if the underwriters are concerned that there may be downward pressure on the price of the common stock in the open market after pricing that could adversely affect investors who purchase in this offering. As an additional means of facilitating this offering, the underwriters may bid for, and purchase, shares of common stock in the open market to stabilize the price of the common stock. These activities may raise or maintain the market price of the common stock above independent market levels or prevent or retard a decline in the market price of the common stock. The underwriters are not required to engage in these activities and may end any of these activities at any time.

We and the underwriters have agreed to indemnify each other against certain liabilities, including liabilities under the Securities Act.

A prospectus supplement in electronic format may be made available on websites maintained by one or more underwriters participating in this offering. The representatives may agree to allocate a number of shares of common stock or pre-funded warrants to underwriters for sale to their online brokerage account holders. Internet distributions will be allocated by the representatives to underwriters that may make Internet distributions on the same basis as other allocations.

The underwriters and their respective affiliates are full service financial institutions engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. Certain of the underwriters and their respective affiliates have, from time to time, performed, and may in the future perform, various financial advisory and investment banking services for us, for which they received or will receive customary fees and expenses. For example, we are party to the Sales Agreement with Cantor, pursuant to which we may offer and sell shares of our common stock from time to time in “at-the-market” offerings.

In addition, in the ordinary course of their various business activities, the underwriters and their respective affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers and may at any time hold long and short positions in such securities and instruments. Such investment and securities activities may involve our securities and instruments. The underwriters and their respective affiliates may also make investment recommendations or publish or express independent research views in respect of such securities or instruments and may at any time hold, or recommend to clients that they acquire, long or short positions in such securities and instruments.

Selling Restrictions

Canada

The shares or pre-funded warrants may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the shares or pre-funded warrants must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

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Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (“NI 33-105”), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Dubai International Financial Centre

This prospectus supplement relates to an Exempt Offer in accordance with the Offered Securities Rules of the Dubai Financial Services Authority (“DFSA”). This prospectus supplement is intended for distribution only to persons of a type specified in the Offered Securities Rules of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for the prospectus. The shares and pre-funded warrants to which this prospectus supplement relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the shares and pre-funded warrants offered should conduct their own due diligence on the shares and pre-funded warrants. If you do not understand the contents of this prospectus supplement you should consult an authorized financial advisor.

European Economic Area

In relation to each Member State of the European Economic Area (each, a “Relevant State”), no shares or pre-funded warrants have been offered or will be offered pursuant to the offering to the public in that Relevant State prior to the publication of a prospectus in relation to the shares and pre-funded warrants which has been approved by the competent authority in that Relevant State or, where appropriate, approved in another Relevant State and notified to the competent authority in that Relevant State, all in accordance with the Prospectus Regulation, except that offers of shares and pre-funded warrants may be made to the public in that Relevant State at any time under the following exemptions under the Prospectus Regulation:

(a)

to any legal entity which is a qualified investor as defined under Article 2 of the Prospectus Regulation;

(b)

to fewer than 150 natural or legal persons (other than qualified investors as defined under Article 2 of the Prospectus Regulation), subject to obtaining the prior consent of the representatives for any such offer; or

(c)

in any other circumstances falling within Article 1(4) of the Prospectus Regulation, provided that no such offer of shares or pre-funded warrants shall require us or any representative to publish a prospectus pursuant to Article 3 of the Prospectus Regulation or supplement a prospectus pursuant to Article 23 of the Prospectus Regulation.

For the purposes of this provision, the expression an “offer to the public” in relation to the shares and pre-funded warrants in any Relevant State means the communication in any form and by any means of sufficient information on the terms of the offer and any shares or pre-funded warrants to be offered so as to enable an investor to decide to purchase or subscribe for any shares or pre-funded warrants, and the expression “Prospectus Regulation” means Regulation (EU) 2017/1129 (as amended).

Hong Kong

The shares and pre-funded warrants may not be offered or sold by means of any document other than (i) in circumstances which do not constitute an offer to the public within the meaning of the Companies (Winding Up and Miscellaneous Provisions) Ordinance (Cap. 32, Laws of Hong Kong), or (ii) to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder, or (iii) in other circumstances which do not result in the document being a “prospectus” within the meaning of the Companies (Winding Up and Miscellaneous Provisions) Ordinance (Cap. 32, Laws of Hong Kong), and no advertisement, invitation or document relating to the shares and pre-funded warrants may be

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issued or may be in the possession of any person for the purpose of issue (in each case whether in Hong Kong or elsewhere), which is directed at, or the contents of which are likely to be accessed or read by, the public in Hong Kong (except if permitted to do so under the laws of Hong Kong) other than with respect to shares or pre-funded warrants which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” within the meaning of the Securities and Futures Ordinance (Cap. 571, Laws of Hong Kong) and any rules made thereunder.

Japan

No registration pursuant to Article 4, paragraph 1 of the Financial Instruments and Exchange Law of Japan (Law No. 25 of 1948, as amended) (the “FIEL”) has been made or will be made with respect to the solicitation of the application for the acquisition of the shares of common stock and pre-funded warrants.

Accordingly, the shares of common stock and pre-funded warrants have not been, directly or indirectly, offered or sold and will not be, directly or indirectly, offered or sold in Japan or to, or for the benefit of, any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity organized under the laws of Japan) or to others for re-offering or re-sale, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan except pursuant to an exemption from the registration requirements, and otherwise in compliance with, the FIEL and the other applicable laws and regulations of Japan.

For Qualified Institutional Investors (“QII”)

Please note that the solicitation for newly-issued or secondary securities (each as described in Paragraph 2, Article 4 of the FIEL) in relation to the shares of common stock and pre-funded warrants constitutes either a “QII only private placement” or a “QII only secondary distribution” (each as described in Paragraph 1, Article 23-13 of the FIEL). Disclosure regarding any such solicitation, as is otherwise prescribed in Paragraph 1, Article 4 of the FIEL, has not been made in relation to the shares of common stock and pre-funded warrants. The shares of common stock and pre-funded warrants may only be transferred to QIIs.

For Non-QII Investors

Please note that the solicitation for newly-issued or secondary securities (each as described in Paragraph 2, Article 4 of the FIEL) in relation to the shares of common stock and pre-funded warrants constitutes either a “small number private placement” or a “small number private secondary distribution” (each as is described in Paragraph 4, Article 23-13 of the FIEL). Disclosure regarding any such solicitation, as is otherwise prescribed in Paragraph 1, Article 4 of the FIEL, has not been made in relation to the shares of common stock and pre-funded warrants. The shares of common stock and pre-funded warrants may only be transferred en bloc without subdivision to a single investor.

Singapore

This prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, this prospectus supplement and any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of shares of our common stock and pre-funded warrants may not be circulated or distributed, nor may the shares of our common stock or pre-funded warrants be offered or sold, or be made the subject of an invitation for subscription or purchase, whether directly or indirectly, to persons in Singapore other than (i) to an institutional investor under Section 274 of the Securities and Futures Act, Chapter 289 of Singapore (“SFA”), (ii) to a relevant person, or any person pursuant to Section 275(1A), and in accordance with the conditions, specified in Section 275 of the SFA or (iii) otherwise pursuant to, and in accordance with the conditions of, any other applicable provision of the SFA.

Where shares of our common stock or pre-funded warrants are subscribed or purchased under Section 275 by a relevant person which is: (i) a corporation (which is not an accredited investor) the sole business of which is

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to hold investments and the entire share capital of which is owned by one or more individuals, each of whom is an accredited investor; or (ii) a trust (where the trustee is not an accredited investor) whose sole purpose is to hold investments and each beneficiary is an accredited investor, shares, debentures, and units of shares and debentures of that corporation or the beneficiaries’ rights and interest in that trust shall not be transferable for 6 months after that corporation or that trust has acquired shares of our common stock or pre-funded warrants under Section 275 except: (i) to an institutional investor under Section 274 of the SFA or to a relevant person, or any person pursuant to Section 275(1A), and in accordance with the conditions, specified in Section 275 of the SFA; (ii) where no consideration is given for the transfer; or (iii) by operation of law.

Switzerland

The shares of common stock and pre-funded warrants may not be publicly offered in Switzerland and will not be listed on the SIX Swiss Exchange (“SIX”), or on any other stock exchange or regulated trading facility in Switzerland. This document has been prepared without regard to the disclosure standards for issuance prospectuses under art. 652a or art. 1156 of the Swiss Code of Obligations or the disclosure standards for listing prospectuses under art. 27 ff. of the SIX Listing Rules or the listing rules of any other stock exchange or regulated trading facility in Switzerland. Neither this document nor any other offering or marketing material relating to the shares and pre-funded warrants or the offering may be publicly distributed or otherwise made publicly available in Switzerland. Neither this document nor any other offering or marketing material relating to the offering, us, or the shares and pre-funded warrants have been or will be filed with or approved by any Swiss regulatory authority. In particular, this document will not be filed with, and the offer of shares will not be supervised by, the Swiss Financial Market Supervisory Authority, and the offer of shares has not been and will not be authorized under the Swiss Federal Act on Collective Investment Schemes (“CISA”). The investor protection afforded to acquirers of interests in collective investment schemes under the CISA does not extend to acquirers of shares or pre-funded warrants.

United Kingdom

In relation to the United Kingdom, no shares or pre-funded warrants have been offered or will be offered pursuant to the offering to the public in the United Kingdom except that the shares and pre-funded warrants may be offered to the public in the United Kingdom at any time:

(a)

where (i) the offer is conditional on the admission of the shares to trading on the London Stock Exchange plc’s main market (in reliance on the exception in paragraph 6(a) of Schedule 1 of the POATR) or (ii) the shares being offered are at the time of the offer already admitted to trading on London Stock Exchange plc’s main market (in reliance on the exception in paragraph 6(b) of Schedule 1 of the POATR);

(b)

to any qualified investor as defined in paragraph 15 of Schedule 1 of the POATR;

(c)

to fewer than 150 persons (other than qualified investors as defined in paragraph 15 of Schedule 1 of the POATR), subject to obtaining the prior consent of the representatives for any such offer; or

(d)

in any other circumstances falling within Part 1 of Schedule 1 of the POATR.

For the purposes of this provision, the expression an “offer to the public” in relation to the shares and pre-funded warrants in the United Kingdom means the communication to any person which presents sufficient information on: (a) the shares and pre-funded warrants to be offered; and (b) the terms on which they are to be offered, to enable an investor to decide to buy or subscribe for the shares or pre-funded warrants and the expression “POATR” means the Public Offers and Admissions to Trading Regulations 2024.

Each underwriter severally and not jointly represents, warrants and agrees that:

(a)

it has only communicated or caused to be communicated and will only communicate or cause to be communicated an invitation or inducement to engage in investment activity (within the meaning of

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Section 21 of the FSMA) in connection with the issue or sale of the shares and pre-funded warrants in circumstances in which Section 21(1) of the FSMA does not apply to the Company; and

(b)

it has complied and will comply with all applicable provisions of the FSMA with respect to anything done by it in relation to the shares and pre-funded warrants in, from or otherwise involving, the United Kingdom.

Israel

In the State of Israel this prospectus supplement shall not be regarded as an offer to the public to purchase shares of common stock and pre-funded warrants under the Israeli Securities Law, 5728-1968, which requires a prospectus to be published and authorized by the Israel Securities Authority, if it complies with certain provisions of Section 15 of the Israeli Securities Law, 5728-1968, including, inter alia, if: (i) the offer is made, distributed or directed to not more than 35 investors, subject to certain conditions (the “Addressed Investors”); or (ii) the offer is made, distributed or directed to certain qualified investors defined in the First Addendum of the Israeli Securities Law, 5728-1968, subject to certain conditions (the “Qualified Investors”). The Qualified Investors shall not be taken into account in the count of the Addressed Investors and may be offered to purchase shares of common stock and pre-funded warrants in addition to the 35 Addressed Investors. The company has not and will not take any action that would require it to publish a prospectus in accordance with and subject to the Israeli Securities Law, 5728-1968. We have not and will not distribute this prospectus or make, distribute or direct an offer to subscribe for our common stock to any person within the State of Israel, other than to Qualified Investors and up to 35 Addressed Investors.

Qualified Investors may have to submit written evidence that they meet the definitions set out in of the First Addendum to the Israeli Securities Law, 5728-1968. In particular, we may request, as a condition to be offered common stock, that Qualified Investors will each represent, warrant and certify to us and/or to anyone acting on our behalf: (i) that it is an investor falling within one of the categories listed in the First Addendum to the Israeli Securities Law, 5728-1968; (ii) which of the categories listed in the First Addendum to the Israeli Securities Law, 5728-1968 regarding Qualified Investors is applicable to it; (iii) that it will abide by all provisions set forth in the Israeli Securities Law, 5728-1968 and the regulations promulgated thereunder in connection with the offer to be issued common stock; (iv) that the shares of common stock or pre-funded warrants that it will be issued are, subject to exemptions available under the Israeli Securities Law, 5728-1968: (a) for its own account; (b) for investment purposes only; and (c) not issued with a view to resale within the State of Israel, other than in accordance with the provisions of the Israeli Securities Law, 5728-1968; and (v) that it is willing to provide further evidence of its Qualified Investor status. Addressed Investors may have to submit written evidence in respect of their identity and may have to sign and submit a declaration containing, inter alia, the Addressed Investor’s name, address and passport number or Israeli identification number.

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LEGAL MATTERS

The validity of the shares of our common stock and pre-funded warrants to be offered in connection with this offering will be passed upon for us by Goodwin Procter LLP, Boston, MA. The underwriters are being represented in connection with this offering by Wilmer Cutler Pickering Hale and Dorr LLP, New York, New York.

EXPERTS

The consolidated financial statements of Q32 Bio Inc. appearing in Q32 Bio Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2025, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such financial statements are, and audited financial statements to be included in subsequently filed documents will be, incorporated herein by reference in reliance upon the report of Ernst & Young LLP pertaining to such financial statements (to the extent covered by consents filed with the SEC) given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

We are subject to the informational requirements of the Exchange Act and in accordance therewith, file annual, quarterly and current reports, proxy statements and other information with the SEC electronically, and the SEC maintains a website that contains our filings as well as reports, proxy and information statements, and other information issuers file electronically with the SEC at www.sec.gov.

We also make available free of charge on or through our website at www.q32bio.com, our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act as soon as reasonably practicable after we electronically file such material with or otherwise furnishes it to the SEC. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus and you should not consider information on our website to be part of this prospectus supplement or the accompanying prospectus.

This prospectus supplement and the accompanying prospectus are part of a registration statement on Form S-3 that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided above. Statements in this prospectus supplement and the accompanying prospectus about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement through the SEC’s website, as provided above.

INCORPORATION BY REFERENCE

The SEC’s rules allow us to “incorporate by reference” information in this prospectus supplement and the accompanying prospectus, which means that we can disclose important information to you by referring you to another document filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus supplement and the accompanying prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. Any statement contained in a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement or a subsequently filed document incorporated by reference modifies or replaces that statement.

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We incorporate by reference our documents listed below and any future filings made by us with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, between the date of this prospectus supplement and the termination or completion of the offering of the securities described in this prospectus supplement. We are not, however, incorporating by reference any documents or portions thereof, whether specifically listed below or filed in the future, that are not deemed “filed” with the SEC, including any information furnished pursuant to Items 2.02 or 7.01 of Form 8-K or related exhibits furnished pursuant to Item 9.01 of Form 8-K.

This prospectus supplement and the accompanying prospectus incorporate by reference the documents set forth below that have previously been filed with the SEC (other than those documents or the portions of those documents not deemed to be filed):

•

Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on March 10, 2026;

•

The information specifically incorporated by reference into our Annual Report on Form 10-K for the year ended December 31, 2025 from our Definitive Proxy Statement on Schedule 14A, filed with the SEC on April 30, 2026;

•

Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2026, filed with the SEC on May 5, 2026;

•

Current Reports on Form 8-K filed with the SEC on February 17, 2026, March 27, 2026, April 24, 2026, May 27, 2026, June 16, 2026, July 13, 2026 and July 13, 2026; and

•

The description of our Common Stock contained in (i) the Registration Statement on Form 8-A (File No. 001-38433), filed by us with the SEC under Section 12(b) of the Exchange Act on March 19, 2018, including any amendments or reports filed for the purpose of updating such description and (ii) Exhibit 4.1—Description of Registrant’s Securities to our Annual Report on Form 10-K for the year ended December 31, 2025, as filed with the SEC on March 10, 2026.

Upon request, we will provide, without charge, to each person, including any beneficial owner, to whom a copy of this prospectus supplement is delivered, a copy of the documents incorporated by reference into this prospectus supplement and the accompanying prospectus but not delivered with this prospectus supplement and the accompanying prospectus. You may request a copy of these filings, and any exhibits we have specifically incorporated by reference as an exhibit in this prospectus supplement, at no cost by writing or telephoning us at the following address:

Q32 Bio Inc.

830 Winter Street

Waltham, MA 02451

Attn: Investor Relations

(781) 999-0232

Email: IR@q32bio.com

You may also access these documents free of charge on the SEC’s website at www.sec.gov or on our website at www.q32bio.com. Information contained on our website is not incorporated by reference into this prospectus supplement or the accompanying prospectus, and you should not consider any information on, or that can be accessed from, our website as part of this prospectus supplement or the accompanying prospectus.

This prospectus supplement and the accompanying prospectus are part of a registration statement we filed with the SEC. We have incorporated exhibits into the registration statement. You should read the exhibits carefully for provisions that may be important to you.

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You should rely only on the information incorporated by reference or provided in this prospectus supplement and the accompanying prospectus. We have not authorized anyone to provide you with different information. We are not making an offer of these securities in any state where the offer is not permitted. You should not assume that the information in this prospectus supplement, the accompanying prospectus or in the documents incorporated by reference is accurate as of any date other than the date on the front of this prospectus supplement or those documents.

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PROSPECTUS

LOGO

$300,000,000

COMMON STOCK

PREFERRED STOCK

DEBT SECURITIES

WARRANTS

UNITS

We may offer from time to time, in one or more offerings, any combination of up to $300,000,000 in the aggregate principal amount of the following securities: common stock, preferred stock, debt securities, warrants, and units, or collectively, the securities. We may offer and sell these securities at times, in amounts, at prices and on terms to be determined at or prior to the time of each offering.

This prospectus describes some of the general terms that may apply to these securities. The specific terms of these securities and information regarding the offering in which these securities will be offered will be provided in supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with each offering of the securities. The prospectus supplements may add, update or change the information contained in this prospectus. You should read this prospectus and any applicable prospectus supplement and any applicable free writing prospectus together with additional information described under the heading “Where You Can Find More Information” carefully before you invest.

We may offer and sell these securities to or through one or more underwriters, dealers or agents, or directly to one or more purchasers, on a continuous or delayed basis, on or off the Nasdaq Capital Market, or Nasdaq. If any underwriters, dealers, or agents are involved in the sale of any of the securities, their names and any applicable purchase price, fee, commission, or discount arrangement between or among them will be set forth, or will be calculable from the information set forth, in the applicable prospectus supplement. See the “Plan of Distribution” section of this prospectus for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

Our common stock, par value $0.0001 per share, or the common stock, is listed on Nasdaq under the symbol “QTTB.” On June 24, 2026, the closing price for our common stock, as reported on Nasdaq, was $11.16 per share. The applicable prospectus supplement will contain information, where applicable, as to any other listing, if any, on Nasdaq or any securities market or other exchange of the securities covered by the applicable prospectus supplement.

As of the date of this prospectus, we are a smaller reporting company as defined under Rule 405 of the Securities Act of 1933, as amended, or the Securities Act, and, as such, are subject to certain reduced public company reporting requirements. See “Prospectus Summary—Implications of Being a Smaller Reporting Company” on page 6 of this prospectus.

Investing in our securities involves certain risks. See the section entitled “Risk Factors” beginning on page 8 of this prospectus, in any applicable prospectus supplement and any related free writing prospectus, and in our Securities and Exchange Commission, or the SEC, filings that are incorporated by reference herein. You should read the entire prospectus carefully before you make your investment decision.

Neither the SEC nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is July 13, 2026.

TABLE OF CONTENTS


	Page

ABOUT THIS PROSPECTUS		1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS		3
PROSPECTUS SUMMARY		5
SECURITIES WE MAY OFFER		7
RISK FACTORS		8
USE OF PROCEEDS		9
DESCRIPTION OF CAPITAL STOCK		10
DESCRIPTION OF DEBT SECURITIES		15
DESCRIPTION OF WARRANTS		17
DESCRIPTION OF UNITS		18
TAXATION		19
PLAN OF DISTRIBUTION		20
LEGAL MATTERS		24
EXPERTS		24
WHERE YOU CAN FIND MORE INFORMATION		24
INCORPORATION BY REFERENCE		24

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the SEC, utilizing a “shelf” registration process. Under this shelf process, we may sell the securities or any combination of the securities described in this prospectus in one or more offerings for an aggregate offering amount of up to $300,000,000. This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and any prospectus supplement together with additional information described under the heading “Where You Can Find More Information” and “Incorporation by Reference.”

Registration of the securities covered by this prospectus does not mean that these securities will necessarily be offered or sold. As of the date of filing this prospectus, we have no specific plans for selling the securities registered hereunder.

You should rely only on the information provided in this prospectus as well as the information incorporated by reference herein and any applicable prospectus supplement or amendment. We have not authorized anyone to give any information or to make any representation other than those contained or incorporated by reference in this prospectus. You must not rely upon any information or representation not contained or incorporated by reference in this prospectus. We take no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. We are not making an offer of these securities in any state where the offer is not permitted. This prospectus does not constitute an offer to sell or the solicitation of an offer to buy any securities other than the registered securities to which it relates, nor does this prospectus constitute an offer to sell or the solicitation of an offer to buy securities in any jurisdiction to any person to whom it is unlawful to make such offer or solicitation in such jurisdiction. You should not assume that the information contained in this prospectus is accurate on any date subsequent to the date set forth on the front of the document or that any information we have incorporated by reference is correct on any date subsequent to the date of the document incorporated by reference, even though this prospectus is delivered or securities are sold on a later date. Our business, financial condition, results of operations and prospects may have changed since those dates.

This prospectus, any applicable prospectus supplement or free writing prospectus and the information incorporated herein or therein incorporates by reference market data and industry statistics and forecasts that are based on independent industry publications and other publicly available information. Although we believe these sources are reliable, we do not guarantee the accuracy or completeness of this information and we have not independently verified this information. In addition, the market and industry data and forecasts that may be included or incorporated by reference in this prospectus may involve estimates, assumptions and other risks and uncertainties and are subject to change based on various factors, including those discussed under the heading “Risk Factors” contained in this prospectus and under similar headings in other documents that are incorporated by reference into this prospectus. Accordingly, investors should not place undue reliance on this information.

A prospectus supplement or free writing prospectus may add to, update or change the information contained in this prospectus. You should read both this prospectus and any applicable prospectus supplement together with additional information described below under the heading “Where You Can Find Additional Information” or incorporated by reference herein as described under the heading “Incorporation of Certain Information by Reference.”

Unless the context otherwise indicates, references in this prospectus to “Company,” “we,” “our” and “us” refer, collectively to Q32 Bio Inc., a Delaware corporation, and its consolidated subsidiaries (including Legacy Q32 (as defined herein)).

We use various trademarks and trade names in our business, including without limitation our corporate name and logo. All other trademarks or trade names referred to in this prospectus are the property of their

respective owners. Solely for convenience, the trademarks and trade names in this prospectus may be referred to without the ^® and ^™ symbols, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus contains and/or incorporates by reference statements that are not historical facts and are considered forward-looking within the meaning of Section 27A of the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. Our forward-looking statements include, but are not limited to, statements regarding our or our management team’s expectations, hopes, beliefs, intentions or strategies regarding the future. In addition, any statements that refer to projections, forecasts or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking statements. The words “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intends,” “may,” “might,” “plan,” “possible,” “potential,” “predict,” “project,” “should,” “will,” “would” and similar expressions may identify forward-looking statements, but the absence of these words does not mean that a statement is not forward-looking. Forward looking statements in this prospectus may include, for example, statements about:

•

our ability to achieve and sustain profitability in the future;

•

our strategies, prospects, plans, expectations or objectives of management for our future operations;

•

estimates of our future expenses, revenues, capital requirements, cash runway, and our needs for additional financing;

•

our estimates of and anticipated use of our existing cash, cash equivalents and marketable securities;

•

the progress, scope or timing of the development of our product candidates;

•

our expectations surrounding the potential safety, efficacy, and regulatory and clinical progress of our product candidates, including bempikibart, and our anticipated milestones and timing therefor;

•

our ability to obtain and maintain regulatory approval of our product candidates;

•

our ability to achieve and maintain market acceptance and adoption of our product candidates;

•

the benefits that may be derived from any of our future products or the commercial or market opportunity with respect to any of our future products;

•

our ability to maintain patent protection for our product candidates and protect our intellectual property rights;

•

our ability to successfully compete against other companies developing similar products to ours;

•

our anticipated operations, financial position, ability to raise capital to fund our operations, revenues, costs or expenses;

•

our ability to retain our key executives and to attract and retain highly qualified personnel;

•

our ability to successfully protect against cyber-attacks, security breaches and other disruptions to our information technology systems;

•

our ability to establish and maintain an effective system of internal controls over financial reporting;

•

our reliance on third parties in the supply and manufacture of our product candidates;

•

the impact of applicable laws and regulations, whether in the U.S. or foreign jurisdictions, and any changes thereto;

•

the statements regarding our future economic conditions or performance, statements of belief and any statement of assumptions underlying any of the foregoing; and

•

other risks and uncertainties, including those listed under the caption “Risk Factors.”

These forward-looking statements are based on information available to us at the time of this prospectus or the documents incorporated by reference herein and current expectations, forecasts and assumptions, and involve a number of judgments, risks and uncertainties. Accordingly, forward-looking statements should not be relied upon as representing our views as of any subsequent date, and we do not undertake any obligation to update forward-looking statements to reflect events or circumstances after the date they were made, whether as a result of new information, future events or otherwise, except as may be required under applicable securities laws.

The outcome of the events described in these forward-looking statements is subject to known and unknown risks, uncertainties, and other factors. As a result of a number of known and unknown risks and uncertainties, our actual results or performance may be materially different from those expressed or implied by these forward-looking statements, including those set forth in this prospectus in the section entitled “Risk Factors” and in our periodic filings with the SEC. Our SEC filings are available publicly on the SEC’s website at www.sec.gov. Given these risks and uncertainties, you should not place undue reliance on these forward-looking statements. Additional cautionary statements or discussions of risks and uncertainties that could affect our results or the achievement of the expectations described in forward-looking statements may also be contained in any accompanying prospectus supplement. Should one or more of the risks or uncertainties described in this prospectus, or should underlying assumptions prove incorrect, actual results and plans could differ materially from those expressed in any forward-looking statements.

You should read this prospectus and any accompanying prospectus supplement completely and with the understanding that our actual future results, levels of activity and performance as well as other events and circumstances may be materially different from what we expect. Except as otherwise required by applicable law, we disclaim any duty to update any forward-looking statements, all of which are expressly qualified by the statements in this section, to reflect events or circumstances after the date of this prospectus. We qualify all of our forward-looking statements by these cautionary statements.

PROSPECTUS SUMMARY

Our Company

We are a clinical stage biotechnology company focused on developing innovative therapies for alopecia areata, or AA, and other autoimmune and inflammatory diseases.

In April 2025, we announced dosing of the first patients in Part B of the SIGNAL-AA Phase 2a clinical trial. Patients will be treated with bempikibart for 36 weeks, with follow-up out to 52 weeks. Efficacy will be evaluated on the basis of mean percentage change from baseline in Severity of Alopecia Tool, or SALT, scores as well as the proportion of subjects achieving various relative and absolute SALT score improvements at week 36, with follow-up through week 52. The trial is intended to support advancement into pivotal trials upon completion, pending review of the results.

Following completion of the SIGNAL-AA Part B trial through 52 weeks, eligible patients can enter an open-label extension, or OLE, period to enable longer-term follow-up and continued dosing. In May 2026, we announced that the first patient has been dosed in the OLE portion of Part B.

In addition to bempikibart, our strategy has been focused on the advancement of our proprietary tissue-targeted complement inhibitor platform. However, in February 2025, we announced a corporate restructuring to focus on the advancement of bempikibart for the treatment of patients with AA. In November 2025, we entered into an Asset Purchase Agreement with Akebia Therapeutics, Inc., or Akebia, pursuant to which we sold to Akebia substantially all of our assets related to the research, development, manufacture and commercialization of ADX-097, a Phase 2 asset from this platform. Following the asset sale, Akebia is now responsible for the future development and commercialization of ADX-097. Other assets developed from our proprietary platform include ADX-096, and C3d mAb fusions and nanobodies designed for tissue-targeted complement inhibition. We retain the rights to our wholly owned tissue-targeted complement inhibitor platform, including ADX-096, and other remaining early-stage assets, and are continuing to evaluate strategic options for these programs.

Corporate Information

We were incorporated under the laws of the State of Delaware on April 10, 2017. On March 25, 2024, Kenobi Merger Sub, Inc., or Merger Sub, a wholly-owned subsidiary of Homology Medicines, Inc., or Homology, completed its merger with and into Q32 Bio Operations Inc. (previously named Q32 Bio Inc. and referred to herein as Legacy Q32), with Legacy Q32 continuing as the surviving entity as a wholly-owned subsidiary of Homology. This transaction is referred to herein as the Merger. Homology changed its name to Q32 Bio Inc., and Legacy Q32, which remains as a wholly-owned subsidiary of ours, changed its name to Q32 Bio Operations, Inc. The Merger was effected pursuant to an Agreement and Plan of Merger, or the Merger Agreement, dated as of November 16, 2023, by and among Homology, Legacy Q32, and Merger Sub. Effective March 26, 2024, our common stock began trading on the Nasdaq Global Market under the trading symbol “QTTB.” Our principal executive office is located at 830 Winter Street, Waltham, Massachusetts 02451, and our telephone number is (781) 999-0232. Our website address is https://www.q32bio.com. We do not incorporate the information on or accessible through our website into this prospectus, and you should not consider any information on, or that can be accessed through, our website as part of this prospectus.

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company” as defined in the Exchange Act. We may take advantage of certain of the scaled disclosures available to smaller reporting companies and will be able to take advantage of these scaled disclosures for so long as the market value of the common stock held by non-affiliates is less than $250.0 million measured on the last business day of our second fiscal quarter, or our annual revenue is less than $100.0 million during the most recently completed fiscal year and the market value of the common stock held by non-affiliates is less than $700.0 million measured on the last business day of our second fiscal quarter. As a result, the information in or incorporated by reference into this prospectus and that we provide to our investors in the future may be different than what you might receive from other public reporting companies.

SECURITIES WE MAY OFFER

We may offer from time to time, in one or more offerings, any combination of up to $300,000,000 in the aggregate principal amount of the following securities at prices and on terms to be determined by market conditions at the time of offering: common stock, preferred stock, debt securities, warrants, and units. This prospectus may not be used to offer or sell securities unless accompanied by an applicable prospectus supplement. The applicable prospectus supplement may add, update or change information contained in this prospectus or in documents incorporated by reference in this prospectus. You should read the prospectus supplement related to any securities being offered.

RISK FACTORS

Investing in our securities involves risks. Before you make a decision to buy our securities, in addition to the risks and uncertainties discussed above under “Cautionary Note Regarding Forward-Looking Statements,” you should carefully consider the risks factors incorporated herein by reference to our most recent Annual Report on Form 10-K and in any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K we file after the date of this prospectus, all other information contained or incorporated by reference into this prospectus, as updated by our subsequent filings under the Exchange Act, and the risk factors and other information contained in any applicable prospectus supplement. We operate in a dynamic and rapidly changing industry that involves numerous risks and uncertainties. If any of these risks actually occur, it may materially harm our business, financial condition, liquidity and results of operations. As a result, the market price of our securities could decline, and you could lose all or part of your investment. Additionally, the risks and uncertainties described in this prospectus or any prospectus supplement are not the only risks and uncertainties that we face. Additional risks and uncertainties not presently known to us or that we currently believe to be immaterial may become material and adversely affect our business.

USE OF PROCEEDS

We will retain broad discretion over the use of the net proceeds from any sale of our securities offered by us under this prospectus. Unless otherwise indicated in a prospectus supplement, the net proceeds from our sale of securities will be used for general corporate purposes, including working capital, expenses related to research, clinical development and commercial efforts and general and administrative expenses, acquisitions and other business opportunities.

DESCRIPTION OF CAPITAL STOCK

The following description summarizes some of the terms of our restated certificate of incorporation and amended and restated bylaws and of the Delaware General Corporation Law. This description is summarized from, and qualified in its entirety by reference to, our restated certificate of incorporation and amended and restated bylaws, each of which has been publicly filed with the SEC.

Our authorized capital stock consists of:

•

400,000,000 shares of common stock, par value $0.0001 per share; and

•

10,000,000 shares of preferred stock, par value $0.0001 per share.

Common Stock

Our common stock is listed on Nasdaq under the symbol “QTTB.”

Voting Rights. Holders of our common stock are entitled to one vote for each share held on all matters submitted to a vote of stockholders and do not have cumulative voting rights. An election of directors by our stockholders shall be determined by a plurality of the votes cast by the stockholders entitled to vote on the election. Subject to the supermajority votes for some matters, other matters shall be decided by the affirmative vote of our stockholders having a majority in voting power of the votes cast by the stockholders present or represented and voting on such matter. Our restated certificate of incorporation, as amended, and amended and restated bylaws also provide that our directors may be removed only for cause and only by the affirmative vote of the holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote thereon. In addition, the affirmative vote of the holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote thereon is required to amend or repeal, or to adopt any provision inconsistent with, several of the provisions of our restated certificate of incorporation, as amended. See below under “-Anti-Takeover Effects of Delaware Law and Our Certificate of Incorporation and Bylaws-Amendment of Charter Provisions.”

Rights Upon Liquidation. In the event of our liquidation or dissolution, the holders of common stock are entitled to receive proportionately our net assets available for distribution to stockholders after the payment of all debts and other liabilities and subject to the prior rights of any outstanding preferred stock.

Other Rights. Holders of common stock have no preemptive, subscription, redemption or conversion rights. Our outstanding shares of common stock are, when issued and paid for, validly issued, fully paid and nonassessable. The rights, preferences and privileges of holders of common stock are subject to and may be adversely affected by the rights of the holders of shares of any series of preferred stock that we may designate and issue in the future.

Transfer Agent

The transfer agent and registrar for our common stock is Equiniti Trust Company, LLC.

Dividend

Holders of common stock are entitled to receive proportionately any dividends as may be declared by our board of directors, subject to any preferential dividend rights of outstanding preferred stock. We have never declared or paid any cash dividends on our common stock. We do not intend to declare or pay cash dividends for the foreseeable future. We currently expect to retain all future earnings, if any, for use in the development, operation and expansion of our business. Any determination to pay cash dividends in the future will depend upon, among other things, our results of operations, plans for expansion, tax considerations, available net profits and reserves, limitations under law, financial condition, capital requirements and other factors that our board of directors considers to be relevant.

Preferred Stock

Under the terms of our restated certificate of incorporation, as amended, our board of directors is authorized to issue shares of preferred stock in one or more series without stockholder approval. Our board of directors have the discretion to determine the rights, preferences, privileges and restrictions, including voting rights, dividend rights, conversion rights, redemption privileges and liquidation preferences, of each series of preferred stock.

The purpose of authorizing the board of directors to issue preferred stock and determine its rights and preferences is to eliminate delays associated with a stockholder vote on specific issuances. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions, future financings and other corporate purposes, could have the effect of making it more difficult for a third party to acquire, or could discourage a third party from seeking to acquire, a majority of our outstanding voting stock.

Registration Rights

2024 Registration Rights Agreement

In connection with the Merger Agreement, Legacy Q32 entered into a subscription agreement in November 2023, or the Subscription Agreement, with certain investors to consummate their purchase of shares of Legacy Q32’s common stock for an aggregate purchase price of $42.0 million, or the Pre-Closing Financing. Pursuant to the Subscription Agreement, on March 25, 2024, we entered into a registration rights agreement, or the 2024 Registration Rights Agreement, with the investors in the Pre-Closing Financing. Under the 2024 Registration Rights Agreement, among other things, we agreed to register for resale certain shares of our common stock held by such investors from time to time, including shares of our common stock issued in the Merger in exchange for the shares of Legacy Q32 common stock issued in the Pre-Closing Financing.

Pursuant to the 2024 Registration Rights Agreement, we are obligated to prepare and file a shelf registration statement covering the resale of covered shares of our common stock within forty-five (45) calendar days following the closing of the Merger, subject to certain exceptions, pursuant to Rule 415 of the Securities Act. We also agreed to use our reasonable best efforts to keep such registration statement continuously effective under the Securities Act until the earlier of the date that all registrable securities covered by such registration statement (a) have been sold, thereunder or pursuant to Rule 144 of the Securities Act, or Rule 144, or (b) may be sold without volume or manner-of-sale restrictions pursuant to Rule 144 and without the requirement for us to be in compliance with the current public information requirement under Rule 144. The 2024 Registration Rights Agreement also provides that we will pay certain expenses of the securityholders and indemnify the applicable securityholders against certain liabilities.

2026 Registration Rights Agreement

On May 26, 2026, we entered into a securities purchase agreement with selected investors to sell shares of common stock and pre-funded warrants to purchase shares of common stock for an aggregate purchase price of approximately $55 million, or the Offering. In connection with the Offering, we entered into a registration rights agreement with each of such selected investors, or the 2026 Registration Rights Agreement, pursuant to which we are required to prepare and file a registration statement with the SEC under the Securities Act, covering the resale of the shares such investors purchased in the Offering and the shares underlying the pre-funded warrants such investors purchased in the Offering. We are required to file such registration statement with the SEC within fifty (50) days of the closing date of the Offering and is required to have such registration statement declared effective by the SEC in accordance with the terms of the Registration Rights Agreement. We also agreed to use our reasonable best efforts to keep such registration statement continuously effective under the Securities Act until the earlier of the date that all registrable securities covered by such registration statement (a) have been sold, thereunder, or (b) may be sold without registration and without volume or manner-of-sale restrictions pursuant to Rule 144 and without the requirement for us to be in compliance with the current public information requirement under Rule 144. The 2026 Registration Rights Agreement also provides that we will pay certain expenses of the securityholders and indemnify the applicable securityholders against certain liabilities.

Pre-Funded Warrants

As of March 1, 2026, we had 1,025,654 shares of common stock issuable upon the exercise of pre-funded warrants and each of such pre-funded warrants has an initial exercise price per share equal to $0.0001. The pre-funded warrants are immediately exercisable upon issuance and may be exercised at any time until they are exercised in full. The exercise price and number of shares of common stock issuable upon exercise is subject to appropriate adjustment in the event of stock dividends and distributions, stock splits, stock combinations, reclassification, reorganizations or similar events affecting our common stock and the exercise price.

A holder of the pre-funded warrants does not have the right to exercise any portion of the pre-funded warrants if the holder (together with its affiliates) would beneficially own in excess of 9.99% of the number of our shares of common stock outstanding immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrants. However, any holder may increase or decrease such percentage, but in no event may such percentage be increased to more than 9.99%, provided that any increase will not be effective until the 61st day after such election.

The pre-funded warrants are exercisable, at the option of the holder, in whole or in part by delivering to us a duly executed exercise notice and, at any time a registration statement registering the issuance of shares of common stock underlying the pre-funded warrants under the securities act is effective and available for the issuance of such shares, or an exemption from registration under the securities act is available for the issuance of such shares, by payment in full in immediately available funds for the number of shares of common stock purchased upon such exercise. The pre-funded warrants may also be exercised, in whole or in part, at such time by means of a cashless exercise, in which case the holder would receive upon such exercise the net number of shares of common stock determined according to the formula set forth in the pre-funded warrant.

Except as otherwise provided in the pre-funded warrants or by virtue of such holder’s ownership of our common stock, the holder of a pre-funded warrant does not have the rights or privileges of a holder of our common stock, including any voting rights or rights to receive dividends, until the holder exercises the pre-funded warrant.

There is no established trading market for the pre-funded warrants and we do not expect a market to develop. In addition, we do not intend to apply for the listing of the pre-funded warrants on any national securities exchange or other trading market.

Anti-Takeover Effects of Delaware Law and Our Certificate of Incorporation and Bylaws

Some provisions of the Delaware law, our restated certificate of incorporation, as amended, and amended and restated bylaws could make the following transactions more difficult: an acquisition by means of a tender offer; an acquisition by means of a proxy contest or otherwise; or the removal incumbent officers and directors. It is possible that these provisions could make it more difficult to accomplish or could deter transactions that stockholders may otherwise consider to be in their best interest or in our best interests, including transactions which provide for payment of a premium over the market price for our shares.

These provisions, summarized below, are intended to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of our company to first negotiate with our board of directors. We believe that the benefits of the increased protection of our potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us outweigh the disadvantages of discouraging these proposals because negotiation of these proposals could result in an improvement of their terms.

Undesignated Preferred Stock

The ability of our board of directors, without action by the stockholders, to issue up to 10,000,000 shares of undesignated preferred stock with voting or other rights or preferences as designated by our board of directors

could impede the success of any attempt to change control of it. These and other provisions may have the effect of deferring hostile takeovers or delaying changes in control or management.

Stockholder Meetings

Our amended and restated bylaws provide that a special meeting of stockholders may be called only by our chairman of the board, chief executive officer or president (in the absence of a chief executive officer), or by a resolution adopted by a majority of our board of directors.

Requirements for Advance Notification of Stockholder Nominations and Proposals

Our amended and restated bylaws establish advance notice procedures with respect to stockholder proposals to be brought before a stockholder meeting and the nomination of candidates for election as directors, other than nominations made by or at the direction of the board of directors or a committee of the board of directors.

Elimination of Stockholder Action by Written Consent

Our restated certificate of incorporation, as amended, eliminates the right of stockholders to act by written consent without a meeting.

Staggered Board

Our board of directors is divided into three classes. The directors in each class will serve for a three-year term, one class being elected each year by our stockholders. This system of electing and removing directors may tend to discourage a third party from making a tender offer or otherwise attempting to obtain control of our company, because it generally makes it more difficult for stockholders to replace a majority of the directors.

Removal of Directors

Our restated certificate of incorporation, as amended, and amended and restated bylaws provide that, subject to the rights of holders of any series of preferred stock, no member of our board of directors may be removed from office by our stockholders except for cause and, in addition to any other vote required by law, upon the approval of the holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote in the election of directors. Subject to the rights of holders of any series of preferred stock, any vacancy on our board of directors, including a vacancy resulting from an enlargement of our board of directors, may be filled only by vote of a majority of directors then in office, unless our board of directors determines by resolution that any such vacancy or newly created directorship shall be filled by our stockholders.

Stockholders Not Entitled to Cumulative Voting

Our restated certificate of incorporation, as amended, does not permit stockholders to cumulate their votes in the election of directors. Accordingly, the holders of a majority of the outstanding shares of our common stock entitled to vote in any election of directors can elect all of the directors standing for election, if they choose, other than any directors that holders of our preferred stock may be entitled to elect.

Delaware Anti-Takeover Statute

We are subject to Section 203 of the General Corporation Law of the State of Delaware, which prohibits persons deemed to be “interested stockholders” from engaging in a “business combination” with a publicly held Delaware corporation for three years following the date these persons become interested stockholders unless the business combination is, or the transaction in which the person became an interested stockholder was, approved

in a prescribed manner or another prescribed exception applies. Generally, an “interested stockholder” is a person who, together with affiliates and associates, owns, or within three years prior to the determination of interested stockholder status did own, 15% or more of a corporation’s voting stock. Generally, a “business combination” includes a merger, asset or stock sale, or other transaction resulting in a financial benefit to the interested stockholder. The existence of this provision may have an anti-takeover effect with respect to transactions not approved in advance by the board of directors.

Choice of Forum

Our restated certificate of incorporation, as amended, provides that, unless we consent in writing to an alternative forum, the Court of Chancery of the State of Delaware will be the sole and exclusive forum for: (1) any derivative action or proceeding brought on our behalf; (2) any action asserting a claim of breach of a fiduciary duty or other wrongdoing by any of our directors, officers, employees or agents to us or our stockholders; (3) any action asserting a claim against it arising pursuant to any provision of the General Corporation Law of the State of Delaware or our restated certificate of incorporation, as amended, or amended and restated bylaws; or (4) any action asserting a claim governed by the internal affairs doctrine. Our restated certificate of incorporation, as amended, also provides that any person or entity purchasing or otherwise acquiring any interest in shares of our capital stock will be deemed to have notice of and to have consented to this choice of forum provision. It is possible that a court of law could rule that the choice of forum provision contained in our restated certificate of incorporation, as amended, is inapplicable or unenforceable if it is challenged in a proceeding or otherwise.

In addition, our amended and restated bylaws provide that unless we consent in writing to the selection of an alternative forum, to the fullest extent permitted by law, the federal district courts of the United States of America shall be the exclusive forum for the resolution of any complaint asserting a cause of action arising under the Securities Act, and any person or entity purchasing or otherwise acquiring or holding any interest in our shares of capital stock shall be deemed to have notice of and consented to this choice of forum provision.

Amendment of Charter Provisions

The amendment of any of the above provisions, except for the provision making it possible for our board of directors to issue preferred stock and the provision prohibiting cumulative voting, would require approval by holders of at least two-thirds in voting power of the outstanding shares of capital stock entitled to vote thereon.

The provisions of Delaware law, our restated certificate of incorporation, as amended, and amended and restated bylaws could have the effect of discouraging others from attempting hostile takeovers and, as a consequence, they may also inhibit temporary fluctuations in the market price of our common stock that often result from actual or rumored hostile takeover attempts. These provisions may also have the effect of preventing changes in the composition of our board and management. It is possible that these provisions could make it more difficult to accomplish transactions that stockholders may otherwise deem to be in their best interests.

DESCRIPTION OF DEBT SECURITIES

The following description, together with the additional information that we include in any applicable prospectus supplements, summarizes the material terms and provisions of the debt securities that we may offer under this prospectus. While the terms we have summarized below will apply generally to any debt securities that we may offer under this prospectus, we will describe the particular terms of any debt securities in more detail in the applicable prospectus supplement. The terms of any debt securities and related guarantees offered under a prospectus supplement may differ from the terms described below.

We may issue senior debt securities under an indenture, or the senior debt indenture, to be entered into between us and the trustee named in the senior debt indenture. We may issue subordinated debt securities under an indenture, or the subordinated debt indenture, and together with the senior debt indenture, the indentures, and each individually, an indenture, to be entered into between us and the trustee named in the subordinated debt indenture.

We have summarized certain terms and provisions of the indentures. The summary is not complete. Forms of the indentures have been filed as exhibits to the registration statement of which this prospectus forms a part, which we have filed with the SEC. You should read the indentures for the provisions that may be important to you. The indentures are subject to and governed by the Trust Indenture Act of 1939, as amended, or the Trust Indenture Act. The senior debt indenture and the subordinated debt indenture are substantially identical, except for the provisions relating to subordination and covenants. See “—Subordinated Debt.”

We may issue debt securities up to an aggregate principal amount as we may authorize from time to time. The prospectus supplement will describe the terms of any debt securities being offered, including:

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classification as senior or subordinated debt securities;

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ranking of the specific series of debt securities relative to other outstanding indebtedness, including subsidiaries’ debt;

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if the debt securities are subordinated, the aggregate amount of outstanding indebtedness, as of a recent date, that is senior to the subordinated securities, and any limitation on the issuance of additional senior indebtedness;

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the designation, aggregate principal amount and authorized denominations;

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the maturity date;

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the interest rate, if any, and the method for calculating the interest rate;

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the interest payment dates and the record dates for the interest payments;

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any mandatory or optional redemption terms or prepayment, conversion, sinking fund or exchangeability or convertibility provisions;

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the place where we will pay principal and interest;

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if other than denominations of $1,000 or multiples of $1,000, the denominations the debt securities will be issued in;

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whether the debt securities will be issued in the form of global securities or certificates;

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additional provisions, if any, relating to the defeasance of the debt securities;

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the currency or currencies, if other than the currency of the United States, in which principal and interest will be paid;

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any United States federal income tax consequences;

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the dates on which premium, if any, will be paid;

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our right, if any, to defer payment interest and the maximum length of this deferral period;

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any listing on a securities exchange;

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the initial public offering price; and

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other specific terms, including any additional events of default or covenants.

Senior Debt

We will issue under the senior debt indenture the debt securities that will constitute part of our senior debt. These senior debt securities will rank equally and pari passu with all of our other unsecured and unsubordinated debt.

Subordinated Debt

We will issue under the subordinated debt indenture the debt securities that will constitute part of our subordinated debt. Payment by us of the principal of, premium, if any, and interest on any series of subordinated debt securities issued under the subordinated debt indenture will be subordinated to the extent set forth in an indenture supplemental to the subordinated indenture relating to such series. The specific subordination terms will be set forth in a supplemental indenture to the subordinated debt indenture and described in the prospectus supplement for the relevant series of debt.

DESCRIPTION OF WARRANTS

The following description, together with the additional information that we include in any applicable prospectus supplements, summarizes the material terms and provisions of the warrants that we may offer under this prospectus. While the terms we have summarized below will apply generally to any warrants that we may offer under this prospectus, we will describe the particular terms of any warrants in more detail in the applicable prospectus supplement. The terms of any warrants offered under a prospectus supplement may differ from the terms described below.

We may issue warrants for the purchase of common stock, preferred stock and/or debt securities in one or more series. Warrants may be issued independently or together with any other securities and may be attached to, or separate from, such securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a warrant agent. The terms of any warrants to be issued and a description of the material provisions of the applicable warrant agreement will be set forth in the applicable prospectus supplement.

The applicable prospectus supplement will describe the following terms of any warrants in respect of which this prospectus is being delivered:

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the title of such warrants;

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the aggregate number of such warrants;

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the price or prices at which such warrants will be issued;

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the currency or currencies in which the price of such warrants will be payable;

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the securities purchasable upon exercise of such warrants;

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the price at which and the currency or currencies in which the securities purchasable upon exercise of such warrants may be purchased;

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the date on which the right to exercise such warrants shall commence and the date on which such right shall expire;

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if applicable, the minimum or maximum amount of such warrants which may be exercised at any one time;

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if applicable, the designation and terms of the securities with which such warrants are issued and the number of such warrants issued with each such security;

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if applicable, the date on and after which such warrants and the related securities will be separately transferable;

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information with respect to book-entry procedures, if any;

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if applicable, a discussion of any material United States federal income tax considerations; and

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any other terms of such warrants, including terms, procedures and limitations relating to the exchange and exercise of such warrants.

DESCRIPTION OF UNITS

The following description, together with the additional information that we include in any applicable prospectus supplements, summarizes the material terms and provisions of the units that we may offer under this prospectus. While the terms we have summarized below will apply generally to any units that we may offer under this prospectus, we will describe the particular terms of any series of units in more detail in the applicable prospectus supplement. The terms of any units offered under a prospectus supplement may differ from the terms described below.

As specified in the applicable prospectus supplement, we may issue units consisting of one or more warrants, debt securities, shares of preferred stock, shares of common stock or any combination of such securities. The applicable supplement will describe:

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the terms of the units and of the warrants, debt securities, preferred stock and common stock comprising the units, including whether and under what circumstances the securities comprising the units may be traded separately;

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a description of the terms of any unit agreement governing the units; and

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a description of the provisions for the payment, settlement, transfer or exchange of the units.

TAXATION

The applicable prospectus supplement may contain information about any material U.S. federal income tax considerations relating to the securities covered by such prospectus supplement.

PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, “at the market offerings,” negotiated transactions, block trades or a combination of these methods or any other method permitted by law. We may sell the securities to or through one or more underwriters or dealers (acting as principal or agent), through agents, or directly to one or more purchasers. The securities may be distributed at a fixed price or prices, which may be changed, market prices prevailing at the time of sale, prices related to the prevailing market prices, or negotiated prices, either:

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on or through the facilities of Nasdaq or any other securities exchange or quotation or trading service on which such securities may be listed, quoted or traded at the time of sale; and/or

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to or through a market maker otherwise than on Nasdaq or such other securities exchanges or quotation or trading services.

In addition, we may issue the securities as a dividend or distribution or in a subscription rights offering to our existing security holders.

We may directly solicit offers to purchase securities, or agents may be designated to solicit such offers. In the prospectus supplement relating to such offering, we will name any agent that could be viewed as an underwriter under the Securities Act and describe any commissions that we must pay to any such agent. Any such agent will be acting on a best efforts basis for the period of its appointment or, if indicated in the applicable prospectus supplement, on a firm commitment basis. This prospectus may be used in connection with any offering of our securities through any of these methods or other methods described in the applicable prospectus supplement.

Each prospectus supplement will describe the method of distribution of the securities and any applicable restrictions.

The prospectus supplement with respect to the securities of a particular series will describe the terms of the offering of the securities, including the following:

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the name of the agent(s), dealer(s) or underwriter(s), if any;

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the purchase price of the securities or other consideration therefor, and the proceeds, if any, we will receive from the sale;

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any over-allotment or other options under which underwriters may purchase additional securities from us;

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any agency fees or discounts or commissions to be allowed or paid to the agent or underwriters;

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all other items constituting agents’ or underwriters’ compensation;

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any discounts and commissions to be allowed or paid to dealers; and

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any exchanges on which the securities will be listed.

If any underwriters or agents are used in the sale of the securities in respect of which this prospectus is delivered, we will enter into an underwriting agreement, sales agreement or other agreement with them at the time of sale to them, and we will set forth in the prospectus supplement relating to such offering the names of the underwriters or agents and the terms of the related agreement with them.

In connection with the offering of securities, we may grant to the underwriters an option to purchase additional securities with an additional underwriting commission, as may be set forth in the applicable prospectus supplement. If we grant any such option, the terms of such option will be set forth in the prospectus supplement for such securities.

If a dealer is used in the sale of the securities in respect of which the prospectus is delivered, we will sell such securities to the dealer, as principal. The dealer, who may be deemed to be an “underwriter” as that term is defined in the Securities Act, may then resell such securities to the public at varying prices to be determined by such dealer at the time of resale.

If we offer securities in a subscription rights offering to our existing security holders, we may enter into a standby underwriting agreement with dealers, acting as standby underwriters. We may pay the standby underwriters a commitment fee for the securities they commit to purchase on a standby basis. If we do not enter into a standby underwriting arrangement, we may retain a dealer-manager to manage a subscription rights offering for us.

Agents, underwriters, dealers and other persons may be entitled under agreements which they may enter into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, and may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

Each underwriter, dealer and agent participating in the distribution of any of the securities that are issuable in bearer form will agree that it will not offer, sell or deliver, directly or indirectly, securities in bearer form in the United States or to United States persons, other than qualifying financial institutions, during the restricted period, as defined in United States Treasury Regulations Section 1.163–5(c)(2)(i)(D)(7).

If so indicated in the applicable prospectus supplement, we will authorize underwriters or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in the prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in the prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will not be subject to any conditions except that:

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the purchase by an institution of the securities covered under that contract shall not at the time of delivery be prohibited under the laws of the jurisdiction to which that institution is subject; and

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if the securities are also being sold to underwriters acting as principals for their own account, the underwriters shall have purchased such securities not sold for delayed delivery. The underwriters and other persons acting as our agents will not have any responsibility in respect of the validity or performance of delayed delivery contracts.

Offered securities may also be offered and sold, if so indicated in the prospectus supplement, in connection with a remarketing upon their purchase, in accordance with a redemption or repayment pursuant to their terms, or otherwise, by one or more remarketing firms, acting as principals for their own accounts or as agents for us. Any remarketing firm will be identified and the terms of its agreement, if any, with us and its compensation will be described in the applicable prospectus supplement. Remarketing firms may be deemed to be underwriters in connection with their remarketing of offered securities.

Certain agents, underwriters and dealers, and their associates and affiliates, may be customers of, have borrowing relationships with, engage in other transactions with, or perform services, including investment banking services, for us or one or more of our respective affiliates in the ordinary course of business.

If any securities are offered by us through underwriters, the underwriters will acquire the securities for their own account and may resell them from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. Underwriters may offer and sell securities to the public either through underwriting syndicates represented by one or more

managing underwriters or directly by one or more firms acting as underwriters. Unless otherwise provided in the applicable prospectus supplement, the obligations of the underwriters to purchase the securities will be subject to certain conditions, and the underwriters will be obligated to purchase all of the offered securities if they purchase any of them. In connection with the sale of securities, underwriters may be deemed to have received compensation from us in the form of underwriting discounts or commissions and dealers may receive compensation from the underwriters in the form of discounts or concessions. The underwriters may change from time to time any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers.

In order to facilitate the offering of the securities, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the securities or any other securities the prices of which may be used to determine payments on such securities. Specifically, any underwriters may over allot in connection with the offering, creating a short position for their own accounts. In addition, to cover overallotments or to stabilize the price of the securities or of any such other securities, the underwriters may bid for, and purchase, the securities or any such other securities in the open market. Finally, in any offering of the securities through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing the securities in the offering if the syndicate repurchases previously distributed securities in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the securities above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

We may engage in at the market offerings into an existing trading market in accordance with Rule 415(a)(4) under the Securities Act. To the extent that we make sales through one or more underwriters or agents in at the market offerings, we will do so pursuant to the terms of a sales agency financing agreement or other at the market offering arrangement between us and the underwriters or agents. If we engage in at the market sales pursuant to any such agreement, we will issue and sell our securities through one or more underwriters or agents, which may act on an agency basis or a principal basis. During the term of any such agreement, we may sell securities on a daily basis in exchange transactions or otherwise as we agree with the underwriters or agents. Any such agreement will provide that any securities sold will be sold at prices related to the then prevailing market prices for our securities. Therefore, exact figures regarding proceeds that will be raised or commissions to be paid cannot be determined at this time. Pursuant to the terms of the agreement, we may agree to sell, and the relevant underwriters or agents may agree to solicit offers to purchase blocks of our securities. The terms of any such agreement will be set forth in more detail in the applicable prospectus supplement.

In addition, we may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement so indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third party may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock. The third party in such sale transactions will be an underwriter and, if not identified in this prospectus, will be named in the applicable prospectus supplement (or a post-effective amendment). In addition, we may otherwise loan or pledge securities to a financial institution or other third party that in turn may sell the securities short using this prospectus and an applicable prospectus supplement. Such financial institution or other third party may transfer its economic short position to investors in our securities or in connection with a concurrent offering of other securities.

Under Rule 15c6-1 of the Exchange Act, trades in the secondary market generally are required to settle in one business day, unless the parties to any such trade expressly agree otherwise. The applicable prospectus supplement may provide that the original issue date for your securities may be more than one scheduled business day after the trade date for your securities. Accordingly, in such a case, if you wish to trade securities on any date prior to the first business day before the original issue date for your securities, you will be required, by virtue of

the fact that your securities initially are expected to settle in more than one scheduled business day after the trade date for your securities, to make alternative settlement arrangements to prevent a failed settlement.

The securities may be new issues of securities and may have no established trading market. Any underwriters to whom we sell securities for public offering and sale may make a market in those securities, but they will not be obligated to do so and they may discontinue any market making at any time without notice. The securities may or may not be listed on a national securities exchange. We can make no assurance as to the liquidity of or the existence of trading market for any of the securities.

The specific terms of any lock-up provisions in respect of any given offering will be described in the applicable prospectus supplement.

The underwriters, dealers and agents may engage in transactions with us, or perform services for us, in the ordinary course of business for which they receive compensation.

The anticipated date of delivery of offered securities will be set forth in the applicable prospectus supplement relating to each offering.

LEGAL MATTERS

The legality of any securities offered will be passed upon for us by Goodwin Procter LLP, Boston, Massachusetts, and for any underwriters or agents by counsel named in the applicable prospectus supplement.

EXPERTS

WHERE YOU CAN FIND MORE INFORMATION

We also make available free of charge on or through our website at www.q32bio.com, our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act as soon as reasonably practicable after we electronically file such material with or otherwise furnishes it to the SEC. The website addresses are inactive textual references and except as specifically incorporated by reference into this prospectus, information on those websites is not part of this prospectus.

This prospectus and any prospectus supplement are part of a registration statement that we filed with the SEC and do not contain all of the information in the registration statement. The full registration statement may be obtained from the SEC or us, as provided below. Other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement or documents incorporated by reference in the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the actual documents for a more complete description of the relevant matters. You may inspect a copy of the registration statement through the SEC’s website, as provided above.

INCORPORATION BY REFERENCE

The SEC allows us to incorporate by reference into this prospectus the information contained in other documents we file with the SEC, which means that we can disclose important information to you by referring you to those documents. Any statement contained in any document incorporated or deemed to be incorporated by reference herein shall be deemed to be modified or superseded, for purposes of this prospectus, to the extent that a statement contained in or omitted from this prospectus, or in any other subsequently filed document that also is or is deemed to be incorporated by reference herein, modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus. We incorporate by reference the documents listed below which have been filed by us:

•

Annual Report on Form 10-K for the fiscal year ended December 31, 2025, filed with the SEC on March 10, 2026;

•

Quarterly Report on Form 10-Q for the fiscal quarter ended March 31, 2026, filed with the SEC on May 5, 2026;

•

Current Reports on Form 8-K filed with the SEC on February 17, 2026, March 27, 2026, April 24, 2026, May 27, 2026 and June 16, 2026; and

•

The description of our Common Stock contained in (i) the Registration Statement on Form 8-A (File No. 001-38433), filed by us with the SEC under Section 12(b) of the Exchange Act on March 19, 2018, including any amendments or reports filed for the purpose of updating such description and (ii) Exhibit 4.1—Description of Securities to our Annual Report on Form 10-K for the year ended December 31, 2025, as filed with the SEC on March 10, 2026.

All documents we file with the SEC pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act, except as to any portion of any report or documents that is not deemed filed under such provisions, (i) on or after the date of filing of the registration statement containing this prospectus and prior to the effectiveness of the registration statement and (ii) on or after the date of this prospectus until the earlier of the date on which all of the securities registered hereunder have been sold or the registration statement of which this prospectus is a part has been withdrawn, shall be deemed incorporated by reference in this prospectus and to be a part of this prospectus from the date of filing of those documents and will be automatically updated and, to the extent described above, supersede information contained or incorporated by reference in this prospectus and previously filed documents that are incorporated by reference in this prospectus.

Nothing in this prospectus shall be deemed to incorporate information furnished but not filed with the SEC pursuant to Item 2.02, 7.01 or 9.01 of Form 8-K. Upon written or oral request, we will provide without charge to each person, including any beneficial owner, to whom a copy of the prospectus is delivered a copy of any or all of the reports or documents incorporated by reference herein (other than exhibits to such documents, unless such exhibits are specifically incorporated by reference herein). You may request a copy of these filings, at no cost, by writing or telephoning us at the following address or phone number:

Q32 Bio Inc.

830 Winter Street

Waltham, MA 02451

Attn: Investor Relations

(781) 999-0232

Email: IR@q32bio.com

LOGO

6,027,399 Shares of Common Stock

Pre-Funded Warrants to Purchase up to 4,931,506 Shares of Common Stock

Prospectus supplement

Joint Book-Running Managers



Morgan Stanley	Jefferies	Cantor	Oppenheimer & Co.

Lead Manager

H.C. Wainwright & Co.

July 14, 2026