Document

424B4 1 cris-prospectusaugust2026.htm 424B4 Document

Filed Pursuant to Rule 424(b)(4)

Registration No. 333-298203

335,001 Shares of Common Stock

3,398,333 Pre-Funded Warrants to Purchase Up to 3,398,333 Shares of Common Stock

3,733,334 Common Warrants to Purchase up to 3,733,334 Shares of Common Stock

7,131,667 Shares of Common Stock underlying the Pre-Funded Warrants and Common Warrants

We are offering 335,001 shares of common stock, par value $0.01 per share (“Common Stock”), of Curis, Inc. (“Curis”, the “Company”, “our company”, “we” or “us”) and, to certain purchasers, 3,398,333 pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 3,398,333 shares of Common Stock, together with 3,733,334 common warrants (“August 2026 Warrants”) to purchase up to 3,733,334 shares of Common Stock at a combined public offering price of $1.50 per share of Common Stock and August 2026 Warrant and $1.49 per Pre-Funded Warrant and August 2026 Warrant, pursuant to this prospectus. The Common Stock and August 2026 Warrants will be sold in a fixed combination, with each share of Common Stock accompanied by one August 2026 Warrant to purchase one share of Common Stock.

We are offering to those purchasers whose purchase of our Common Stock in this offering would otherwise result in such purchaser, together with its affiliates and certain related parties, beneficially owning more than 9.99% of our outstanding Common stock immediately following the consummation of this offering, the opportunity, in lieu of purchasing Common Stock, to purchase the Pre-Funded Warrants. Each Pre-Funded Warrant will be immediately exercisable for one share of Common Stock at any time at the option of the holder until such Pre-Funded Warrant is exercised in full, provided that the holder will be prohibited from exercising Pre-Funded Warrants if, as a result of such exercise, the holder, together with its affiliates and certain related parties, would own more than 9.99% of the total number of shares of Common Stock then issued and outstanding. The combined purchase price of each Pre-Funded Warrant and August 2026 Warrant is $1.49 (which is the combined public offering price of $1.50 per share of Common Stock and August 2026 Warrant to be sold in this offering minus $0.01, the exercise price per share of Common Stock of each Pre-Funded Warrant). The Pre-Funded Warrants will be sold together with August 2026 Warrants in a fixed combination, with each Pre-Funded Warrant accompanied by one August 2026 Warrant to purchase one share of Common Stock.

Each August 2026 Warrant will have an exercise price of $1.75 per share of Common Stock, will be immediately exercisable upon issuance, and will expire on the five (5) year anniversary of the issuance date.

We are also registering the shares of Common Stock issuable from time to time upon the exercise of the Pre-Funded Warrants and August 2026 Warrants offered hereby.

Our Common stock is listed on The Nasdaq Capital Market under the symbol “CRIS”. On August 12, 2026, the last sale price of our Common stock was $1.67 per share. There is no established public trading market for the Pre-Funded Warrants or August 2026 Warrants and we do not expect a market to develop. Without an active trading market, the liquidity of those warrants will be limited. In addition, we do not intend to list the Pre-Funded Warrants or August 2026 Warrants on Nasdaq, any other national securities exchange or any other trading system.

The offering will terminate on September 9, 2026, unless (i) the closing occurs prior thereto or (ii) we decide to terminate the offering (which we may do at any time in our discretion) prior to that date. The securities purchased in this offering are expected to be issued in a single closing. The public offering price per share of Common Stock (or Pre-Funded Warrant) will be fixed for the duration of the offering.

We entered into a securities purchase agreement relating to the offering with those investors that chose to enter into such an agreement on August 12, 2026, the day that the registration statement of which this prospectus forms a part was declared effective, and that the closing of the offering will end one trading day after we first enter into a securities purchase agreement relating to the offering. The offering will settle delivery versus payment (“DVP”)/receipt versus payment (“RVP”). That is, on the closing date, we will issue the shares of Common Stock directly to the account(s) at the Placement Agent identified by each purchaser; upon receipt of such shares, the Placement Agent shall promptly electronically deliver such shares to the applicable purchaser, and payment therefor shall be made by the Placement Agent (or their clearing firm) by wire transfer to us.

We have engaged A.G.P./Alliance Global Partners. (“A.G.P.”) and Laidlaw & Company (UK) Ltd. (“Laidlaw”) (the “Placement Agents”) to act as our exclusive placement agents in connection with this offering. The Placement Agents have agreed to use their reasonable best efforts to arrange for the sale of the securities offered by this prospectus. The Placement Agents are not purchasing or selling any of the securities we are offering. We have agreed to pay to the Placement Agents the placement agent fees set forth in the table below


	Per Share of Common Stock and August 2026 Warrants			Per Pre-Funded Warrant and August 2026 Warrants		Total
Public Offering Price		$	1.50	$	1.49	$	5,600,000
Placement Agents Fees (1)		$	0.0975	$	0.09685	$	364,000
Proceeds to us, before expenses (2)(3)		$	1.4025	$	1.3931	$	5,236,000


(1)			We have agreed to pay the Placement Agents a cash fee equal to 6.5% of the gross proceeds raised in this offering. See “Plan of Distribution” for a description of the compensation and expense reimbursement to be received by the Placement Agents.

(2)			We estimate the total expenses of this offering payable by us, excluding the Placement Agents fees, will be approximately $0.4 million.

(3)			Does not include proceeds from the cash exercise of the Pre-Funded Warrants or August 2026 Warrants, if any.

Investing in our securities involves a high degree of risk. You should review carefully the risks and uncertainties described in the section titled “Risk Factors” beginning on page 8 of this prospectus, and under similar headings in any amendments or supplements to this prospectus.

Neither the Securities and Exchange Commission (the “SEC”) nor any state securities commission has approved or disapproved of the securities to be issued under this prospectus or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We expect to deliver the securities to the purchasers in the offering on or about August 14, 2026, subject to satisfaction of certain conditions.

Lead Placement Agent

A.G.P.

Co-Placement Agent

LAIDLAW & COMPANY (UK) LTD.

The date of this prospectus is August 12, 2026

TABLE OF CONTENTS


	Page
About this Prospectus		1
Prospectus Summary		2
The Offering		6
Risk Factors		8
Cautionary Note Regarding Forward-Looking Statements		11
Use of Proceeds		13
Selected Financial Data		14
Capitalization		15
Dilution		16
Dividend Policy		18
Description of Securities We are Offering		19
Plan of Distribution		25
Material U.S. Federal Income Tax Consequences		28
Legal Matters		35
Experts		36
Where You Can Find More Information		37
Incorporation by Reference		38

About this Prospectus

This prospectus is part of a registration statement that we filed with the SEC. As permitted by the rules and regulations of the SEC, the registration statement filed by us includes more information not contained in this prospectus. You may read the registration statement and the other reports we file with the SEC at the SEC’s website or its offices described below under the heading “Where You Can Find More Information.”

You should rely only on the information contained or incorporated by reference in this prospectus. We have not, and the Placement Agents have not, authorized anyone to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it. The distribution of this prospectus and sale of these securities in certain jurisdictions may be restricted by law. We are not making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. Persons in possession of this prospectus are required to inform themselves about and observe any such restrictions. The information contained in this prospectus and the documents incorporated by reference in this prospectus that we have authorized for use in connection with this offering, is accurate only as of the date of those respective documents regardless of the time of delivery of this prospectus when any sale of our securities occurs. Our business, financial condition, results of operations and prospects may have changed since those dates.

Neither we nor the Placement Agents have done anything that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons who come into possession of this prospectus and any free writing prospectus in jurisdictions outside the United States are required to inform themselves about and to observe any restrictions as to this offering and the distribution of this prospectus and any free writing prospectus applicable to that jurisdiction. We will not make an offer to sell these securities in any jurisdiction where the offer or sale is not permitted.

You should read this prospectus and the documents incorporated by reference in this prospectus in their entirety, before making an investment decision. You should also read and consider the information in the documents to which we have referred you in the sections of this prospectus entitled “Where You Can Find More Information” and “Incorporation by Reference.”

This prospectus contains summaries of certain provisions contained in some of the documents described herein, but reference is made to the actual documents for complete information. All of the summaries are qualified in their entirety by the actual documents. Copies of some of the documents referred to herein have been filed, will be filed or will be incorporated herein by reference as exhibits to the registration statement, and you may obtain copies of those documents as described below under the section entitled “Where You Can Find More Information.”

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 herein 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 or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

This prospectus incorporates by reference market data and certain industry data and forecasts that were obtained from market research databases, publicly available information and industry publications and surveys. Industry surveys, publications and forecasts generally state that the information contained therein has been obtained from sources believed to be reliable. We have relied on certain data from third-party sources, including industry forecasts and market research, which we believe to be reliable based on our management’s knowledge of the industry. Statements as to our market position are based on the most currently available data. While we are not aware of any misstatements regarding the industry data presented in this prospectus or in any document incorporated by reference, our estimates involve risks and uncertainties and are subject to change based on various factors, including those discussed under the headings “Risk Factors” in this prospectus, and under similar headings in the other documents that are incorporated herein by reference.

PROSPECTUS SUMMARY

This prospectus summary highlights selected information appearing elsewhere in this prospectus and in documents we file with the SEC that are incorporated by reference in this prospectus. Because it is a summary, it may not contain all of the information that may be important to you. To understand this offering fully, you should read this entire prospectus carefully, including the information incorporated by reference herein, the information set forth under the heading “Risk Factors” and our financial statements and the related notes thereto incorporated by reference in this prospectus.

Unless the context otherwise requires, all references in this prospectus to the “Company,” “Curis,” “we,” “our,” “ours,” and “us” refer to Curis, Inc.

Overview

We are a biotechnology company focused on the development of emavusertib (CA-4948), an orally available, small molecule inhibitor of Interleukin-1 receptor associated kinase, or IRAK4 and FMS-like tyrosine kinase 3 or FLT3. Emavusertib is currently being evaluated in the TakeAim Lymphoma Phase 1/2 study (CA-4948-101) in patients with relapsed/refractory primary central nervous system lymphoma, or PCNSL, in combination with ibrutinib, a Bruton Tyrosine Kinase inhibitor or BTK inhibitor and in our recently initiated TakeAim CLL study, a Phase 2 combination study of emavusertib in chronic lymphocytic leukemia, or CLL, with zanubrutinib, a BTK inhibitor. Our monotherapy and combination studies of emavusertib in AML are substantially complete. Emavusertib has received Orphan Drug Designation from the U.S. Food and Drug Administration, or FDA, for the treatment of PCNSL, AML and MDS and from the European Commission for the treatment of PCNSL. We, through our 2015 collaboration with Aurigene Discovery Technologies Limited, or Aurigene, have the exclusive license to emavusertib (CA-4948).

On July 2, 2026, the Company effected a 1-for-20 reverse stock split. All historical share counts, outstanding options, and per-share data (including loss per share) presented in this prospectus have been retroactively adjusted for all periods to reflect the impact of the stock split.

Emavusertib

Emavusertib is a small molecule inhibitor of Interleukin-1 receptor associated kinase, or IRAK4, and FMS‐like tyrosine kinase 3, or FLT3. IRAK4 plays an essential role in the toll-like receptor, or TLR, and interleukin-1 receptor, or IL-1R, signaling pathways, which are frequently dysregulated in patients with cancer. TLRs and the IL-1R family signal through the adaptor protein Myeloid Differentiation Primary Response Protein 88, or MYD88, which results in the assembly and activation of IRAK4, initiating a signaling cascade that induces cytokine and survival factor expression mediated by the NF-κB protein complex. Many B-cell leukemias and lymphomas are associated with constitutive activation of the NF-κB protein complex, which contributes to these cancers' proliferation and survival. The B-cell receptor, or BCR, and TLR pathways drive NF-κB activation. Preclinical studies have demonstrated that targeting both the BCR and TLR pathways is more synergistic than targeting either pathway alone. Similarly, preclinical studies targeting IRAK4 in combination with FLT3 have demonstrated the ability to overcome the adaptive resistance incurred when targeting FLT3 alone. In acute myeloid leukemia, or AML, emavusertib has shown monotherapy anti-tumor activity, particularly those with a FLT3 mutation, as well as synergy with both azacitidine and venetoclax. In non-Hodgkin's lymphoma patients, emavusertib has shown anti-tumor activity in combination with a BTK inhibitor.

In January 2026, we announced that we are focusing our operations on our ongoing combination Phase 1/2 study in relapsed/refractory, or R/R, PCNSL with ibrutinib and our recently initiated Phase 2 combination study of emavusertib in CLL with zanubrutinib. Our monotherapy and combination studies of emavusertib in AML are substantially complete, with additional funding, we plan to continue development of emavusertib in AML.

TakeAim CLL

In August 2025, we announced a Phase 2 open label clinical study of emavusertib in combination with zanubrutinib in frontline CLL (CA-4948-203, NCT07271667), also known as the TakeAim CLL study. In July 2026, we announced the first five patients in the study were dosed. We expect to announce initial CLL data in five to ten patients in December 2026.

TakeAim Lymphoma

Emavusertib is currently undergoing testing in combination with ibrutinib in a Phase 1/2 open-label, single arm expansion trial in patients with R/R PCNSL (CA-4948-101, NCT03328078), also known as the TakeAim Lymphoma Phase 1/2 study. In June 2022 and December 2023, we provided preliminary clinical data for patients with various hematological malignancies in the combination portion of the ongoing TakeAim Lymphoma Phase 1/2 study. In December 2023, we provided clinical and safety data of emavusertib in combination with ibrutinib in several non-Hodgkin's lymphoma subtypes, including PCNSL. In July and December 2024, emavusertib was granted Orphan Drug Designation by the European Commission and the U.S. Food and Drug Administration, or FDA, respectively, for the treatment of patients with PCNSL. In September 2024, March 2025, November 2025, and July 2026 we provided additional clinical data of emavusertib in combination with ibrutinib in R/R PCNSL. In March 2025, we announced that we had completed productive meetings with both the European Committee for Medicinal Products for Human Use, or CHMP, and the FDA on the suitability of using the ongoing TakeAim Lymphoma Phase 1/2 study to support a potential accelerated regulatory path for a Conditional Marketing Authorization, or CMA, submission in Europe and a New Drug Application, or NDA, submission in the U.S.

For submission in Europe, we engaged CHMP for scientific advice on the potential for CMA submission, with the following feedback:

•Current, single-arm, study could support a CMA;

•Primary endpoint of Overall Response Rate, or ORR, for a single-arm study is supported;

•45 patients may be sufficient to support a CMA, assuming compelling and consistent results;

•Due to the rarity of disease the proposed size of the safety database may be acceptable and will be a review issue for CMA; and

•Contribution of effect of each of emavusertib and ibrutinib as well as the emavusertib/ibrutinib combination in a BTKi-naïve population is required for CMA.

For submission in the U.S., we discussed with FDA the potential for an NDA submission for Accelerated Approval based on the lack of approved treatments, with the following feedback:

•Current, single-arm, study could support a submission for Accelerated Approval;

•ORR, supported by adequate duration of response, could be acceptable for Accelerated Approval;

•The number of patients needed to support safety and efficacy is a review issue, which is part of the NDA submission process; and

•An analysis of 100 mg vs 200 mg emavusertib dosing and contribution of effect of emavusertib, ibrutinib, and the emavusertib/ibrutinib combination in a BTKi-naïve population is required prior to NDA submission.

Both the CHMP and FDA encouraged us to continue discussions to align on the confirmatory study design, which is required prior to the CMA or NDA submission.

In July 2026, we announced the following updated data from PCNSL patients in our TakeAim Lymphoma study which included data for 7 BTK-naïve patients and 39 BTKi-experienced patients:

as of July 1, 2026

as of May 1, 2025

Evaluable Patients*

All Patients

Previous Data All Patients

BTKi-naïve

100% ORR (5 of 5)

86% ORR (6 of 7)

71% ORR (5 of 7)

BTKi-experienced

33% ORR (10 of 30)

26% ORR (10 of 39)

27% ORR (7 of 26)

*excludes patients who did not complete at lease 1 cycle (~1 month) of treatment

Our Collaboration and License Agreement

In January 2015, we entered into an exclusive collaboration agreement with Aurigene, which was amended in September 2016, February 2020, June 2020, and September 2024, for the discovery, development and commercialization of small molecule compounds in the areas of immuno-oncology and precision oncology worldwide, except for India and Russia, which are territories retained by Aurigene. We currently have licensed the IRAK4 (including emavusertib), PD1/TIM3, and an immuno-oncology program under the Aurigene collaboration.

For further information regarding our collaboration and license agreement, refer to Note 6, Research and Development Collaborations in Item 1 of Part I of our Quarterly Report on Form 10-Q and Note 9, Research and Development Collaborations, in Item 8 of Part II of our Annual Report on Form 10-K.

Liquidity and Events that Raise Substantial Doubt About Our Ability to Continue as a Going Concern

Since our inception, we have funded our operations primarily through private and public placements of our equity securities, license fees, contingent cash payments, royalties and research and development funding from our corporate collaborators, and the monetization of certain royalty rights. We have never been profitable on an annual basis and had an accumulated deficit of $1.3 billion as of March 31, 2026. For the three months ended March 31, 2026, we incurred a net loss of $24.2 million and used $9.0 million of cash in operations.

We expect to continue to generate operating losses in the foreseeable future. Our current cash and cash equivalents are not expected to fund our operations beyond 12 months from the date of filing this Prospectus. These factors raise substantial doubt regarding the Company’s ability to continue as a going concern. We will require substantial additional funds in the immediate term to maintain our research and development program and support operations.

We will need to generate significant revenues to achieve profitability, and do not expect to achieve profitability in the foreseeable future, if at all. We will require substantial additional funding to fund the development of emavusertib through regulatory approval and commercialization, and to support our continued operations. We will need to seek additional funding through a number of potential avenues, including private or public equity financings, collaborations, or other strategic transactions. Our ability to raise additional funds will depend on, among other factors, financial, economic and market conditions, as well as maintaining our listing on Nasdaq, many of which are outside of our control, and we may be unable to raise financing when needed, or on terms favorable to us. We have faced and expect to continue to face substantial difficulties in raising capital. If sufficient funds are not available, we will have to delay, reduce the scope of, or eliminate our research and development program for emavusertib, including related clinical trials and operating expenses, potentially delaying the time to market for or preventing the marketing of emavusertib, which could adversely affect our business prospects and our ability to continue our operations, and would have a negative impact on our financial condition and ability to pursue our business

strategies. In addition, we may seek to engage in one or more strategic alternatives, such as a strategic partnership with one or more parties, the licensing, sale or divestiture of some of our assets or proprietary technologies or the sale of our company, but there can be no assurance that we would be able to enter into such a transaction or transactions on a timely basis or on terms favorable to us, or at all. If we are unable to obtain sufficient capital, we would be unable to fund our operations and may be required to evaluate alternatives, which could include dissolving and liquidating our assets or seeking protection under the bankruptcy laws, and a determination to file for bankruptcy could occur at a time that is earlier than when we would otherwise exhaust our cash resources. If we decide to dissolve and liquidate our assets or to seek protection under the bankruptcy laws, it is unclear to what extent we would be able to pay our obligations, and, accordingly, it is further unclear whether and to what extent any resources would be available for distributions to stockholders.

Key Drivers

We believe near term key drivers to our success will include:

•our ability to focus and successfully plan and execute current and planned clinical trials for emavusertib, and for such clinical trials to generate favorable data;

•our ability to raise additional financing to fund operations; and/or

•our ability to collaborate or license emavusertib and to successfully develop and commercialize emavusertib.

Company Information

We were organized as a Delaware corporation in February 2000. Our principal executive offices are located at 128 Spring Street, Building C – Suite 500, Lexington, Massachusetts 02421, and our telephone number is (617) 503-6500. Our website is located at www.curis.com. The information contained in, or that can be accessed through, our website is not incorporated by reference into this prospectus and should not be considered to be a part of this prospectus. Our website address is included as an inactive textual reference only.

Implications of Being a Smaller Reporting Company

We are a “smaller reporting company,” meaning that the market value of our stock held by non-affiliates was less than $700 million measured on the last business day of our most recently completed second fiscal quarter and our annual revenue was less than $100 million during our most recently completed fiscal year. We may continue to be a smaller reporting company if either (i) the market value of our stock held by non-affiliates is less than $250 million measured on the last business day of our second fiscal quarter or (ii) our annual revenue was less than $100 million during the most recently completed fiscal year and the market value of our stock held by non-affiliates is less than $700 million measured on the last business day of our second fiscal quarter. For so long as we remain a smaller reporting company, we are permitted and intend to rely on exemptions from certain disclosure and other requirements that are applicable to other public companies that are not smaller reporting companies.


THE OFFERING


Common stock offered by us						335,001 shares.
Pre-funded Warrants offered by us						We are also offering, in lieu of Common Stock to certain investors, Pre-Funded Warrants to purchase up to 3,398,333 shares of our Common Stock. The purchase price of the Pre-Funded Warrants matches the price per share at which the shares of our Common Stock are being sold to the public in this offering, minus $0.01, which is the per share exercise price of the Pre-Funded Warrants. The Pre-Funded Warrants will be exercisable at any time after the date of issuance of such Pre-Funded Warrants, subject to an ownership limitation. See the section titled “Description of Securities We Are Offering” on page 19. This prospectus also relates to the offering of the shares of our Common Stock issuable upon exercise of the Pre-Funded Warrants.
August 2026 Warrants offered by us						We are also offering August 2026 Warrants to purchase 3,733,334 shares of our Common Stock. Each share of Common Stock or Pre-Funded Warrant is being offered together with one August 2026 Warrant exercisable for one share of Common Stock. Each August 2026 Warrant has an initial exercise price of $1.75 per share of Common Stock. The August 2026 Warrants will become exercisable immediately upon issuance and will expire five years from the date thereof. The August 2026 Warrants include certain mechanisms, including certain anti-dilution provisions and other standard adjustment provisions. To better understand the terms of the August 2026 Warrants, you should carefully read the “Description of August 2026 Warrants” section of this prospectus. You should also read the form of the August 2026 Warrant, which is filed as an exhibit to the registration statement of which this prospectus forms a part. The shares of Common Stock and Pre-Funded Warrants, and the accompanying August 2026 Warrants can only be purchased together in this offering but will be issued separately and will be immediately separable upon issuance. This prospectus also relates to the offering of the shares of Common Stock issuable upon exercise of the August 2026 Warrants.
Use of proceeds						We estimate the net proceeds of the offering will be approximately $4.8 million, after deducting the Placement Agents fees and expenses and estimated offering expenses payable by us. We currently intend to use the net proceeds from this offering to fund our research and development activities and for working capital and general corporate purposes. We have not determined the amount of net proceeds to be used specifically for such purposes. As a result, our management will have broad discretion in the application of the net proceeds of this offering. See “Use of Proceeds” on page 13 for more information.
Risk Factors						Investing in our securities involves a high degree of risk. You should read the “Risk Factors” section starting on page 8 of this prospectus for a discussion of factors to consider carefully before deciding to invest in our securities.


Nasdaq Capital Market symbol						Our Common Stock is listed on the Nasdaq Capital Market under the symbol “CRIS.” There is no established public trading market for the Pre-Funded Warrants and August 2026 Warrants being offered and we do not expect a market to develop. Without an active trading market, the liquidity of those warrants will be limited. In addition, we do not intend to list the Pre-Funded Warrants or August 2026 Warrants on the Nasdaq Capital Market, any other national securities exchange or any other trading system.
Best efforts offering						We have agreed to offer and sell the securities offered hereby to the purchasers through the Placement Agents. The Placement Agents are not required to buy or sell any specific number or dollar amount of the securities offered hereby, but they will use their reasonable best efforts to solicit offers to purchase the securities offered by this prospectus. See “Plan of Distribution” for more information.

The number of shares of our Common Stock that will be outstanding immediately after this offering as shown above is based on 2,090,077 shares outstanding as of August 7, 2026 and excludes:

•460,833 shares of our Common Stock issuable upon the exercise of stock options outstanding at a weighted average exercise price of $79.82 per share;

•5,464 shares of Common Stock issuable upon the vesting of restricted stock units outstanding;

•an aggregate of 28,069 shares of Common Stock reserved for future issuance under our 2026 Incentive Plan;

•an aggregate of 17,891 shares of Common Stock reserved for future issuance under our Amended and Restated 2010 Employee Stock Purchase Plan, as amended;

•153,278 shares of our Common Stock issuable upon the exercise of pre-funded warrants outstanding at an exercise price of $0.20 per share; and

•4,728,671 shares of our Common Stock issuable upon the exercise of warrants outstanding at a weighted average exercise price of $20.95 per share.

Except as otherwise noted, all information in this prospectus gives effect to a 1-for-20 reverse stock split of our Common Stock, which was effected on July 2, 2026.

Unless otherwise indicated, all information in this prospectus assumes:

•no additional sales of our Common Stock through our ATM Facility;

•no exercise or conversion of options, pre-funded warrants or warrants described above.

RISK FACTORS

An investment in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully the risks described below and discussed in the “Risk Factors” sections of our Annual Report on Form 10-K for the fiscal year ended December 31, 2025 and our Quarterly Report on Form 10-Q for the quarter ended March 31, 2026 incorporated by reference herein, together with other information in this prospectus, and the information and documents incorporated by reference in this prospectus. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be seriously harmed. This could cause the trading price of our securities to decline, resulting in a loss of all or part of your investment.

Risks Related to This Offering

We have identified conditions and events that raise substantial doubt about our ability to continue as a going concern.

We will require substantial funds to maintain our research and development program and support operations in the near term. We have incurred losses and negative cash flows from operations since our inception. As of March 31, 2026, we had $15.0 million in cash and cash equivalents. Without taking into account the anticipated net proceeds from this offering, we expect these available cash resources to fund our existing operations into the fourth quarter of 2026. We have based this assessment on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect. Based on our current cash and cash equivalents, recurring losses and cash outflows from operations since inception, an expectation of continuing losses and cash outflows from operations for the foreseeable future and the need to raise additional capital to finance our future operations, we do not have sufficient cash on hand to support current operations beyond the next 12 months. These factors raise substantial doubt regarding the Company’s ability to continue as a going concern. The proceeds of this offering will not be sufficient to alleviate our substantial doubt about our ability to continue as a going concern beyond the next 12 months.

We will require substantial additional funding in the immediate term to fund the development of emavusertib through regulatory approval and commercialization, and to support our continued operations. We will need to seek additional funding through a number of potential avenues, including private or public equity financings, collaborations, or other strategic transactions. We have faced and expect to continue to face substantial difficulty in raising capital. If sufficient funds are not available, we will have to delay, reduce the scope of, or eliminate our research and development program for emavusertib, including related clinical trials and operating expenses, potentially delaying the time to market for or preventing the marketing of emavusertib, which would adversely affect our business prospects and our ability to continue our operations, and would have a negative impact on our financial condition and ability to pursue our business strategies. In addition, we may seek to engage in one or more strategic alternatives, such as a strategic partnership with one or more parties, the licensing, sale or divestiture of some of our assets or proprietary technologies or the sale of our company, but there can be no assurance that we would be able to enter into such a transaction or transactions on a timely basis or on terms favorable to us, or at all. If we are unable to obtain sufficient capital, we would be unable to fund our operations and may be required to evaluate alternatives, which could include dissolving and liquidating our assets or seeking protection under the bankruptcy laws, and a determination to file for bankruptcy could occur at a time that is earlier than when we would otherwise exhaust our cash resources. If we decide to dissolve and liquidate our assets or to seek protection under the bankruptcy laws, it is unclear to what extent we would be able to pay our obligations, and, accordingly, it is further unclear whether and to what extent any resources would be available for distributions to stockholders.

If we are unable to continue as a going concern, we may have to liquidate our assets and may receive less than the value at which those assets are carried on our audited financial statements, and it is likely that investors will lose all or a part of their investment. The report from our independent registered public accounting firm issued in connection with our Annual Report on Form 10-K for the year ended December 31, 2025 contains, and future reports may contain, statements expressing substantial doubt about our ability to continue as a going concern. If we seek additional financing to fund our business activities in the future and there remains substantial doubt about our

ability to continue as a going concern, investors or other financing sources may be unwilling to provide funding to us on commercially reasonable terms, if at all.

We have broad discretion in how we use the net proceeds of this offering, and we may not use these proceeds effectively or in ways with which you agree.

Our management will have broad discretion as to the application of the net proceeds of this offering, including for any of the purposes described in the section of this prospectus entitled “Use of Proceeds.” You will be relying on the judgment of our management regarding the application of the proceeds of this offering. The results and effectiveness of the use of proceeds are uncertain, and we could spend the proceeds in ways that you do not agree with or that do not improve our results of operations or enhance the value of our Common Stock. Our failure to apply these funds effectively could have a material adverse effect on our business, delay the development of our drug candidates and cause the price of our Common Stock to decline.

Investors in this offering will pay a much higher price than the book value of our stock.

The offering price of our Common Stock is substantially higher than the net tangible book value per share of our Common Stock. Therefore, if you purchase shares of Common Stock in this offering, you will pay a price per share of Common Stock that substantially exceeds our net tangible book value per share after giving effect to this offering. Based on an offering price of $1.50 per share of Common Stock, if you purchase shares of Common Stock in this offering, you will experience immediate dilution of $0.05 per share, representing the difference between the offering price of the Common Stock and our as adjusted net tangible book value per share after giving effect to this offering. For a further description of the dilution that you will experience immediately after this offering, see “Dilution.”

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

We will need additional capital to fund our research and development programs and to fulfill our planned operating goals. We may seek additional capital through a combination of private and public equity offerings, debt financings, strategic partnerships and alliances and licensing arrangements, which may cause your ownership interest to be diluted. We have a significant number of options and warrants to purchase shares of our Common Stock outstanding. If these securities are exercised, you may incur further dilution. Moreover, to the extent that we issue additional options to purchase, or securities convertible into or exchangeable for, shares of our Common Stock in the future and those options or other securities are exercised, converted or exchanged, stockholders may experience further dilution.

A substantial number of shares may be sold in the market following this offering, which may depress the market price for our Common Stock or cause it to be highly volatile.

Sales of a substantial number of shares of our Common Stock in the public market following this offering, or the perception that such sales could occur, could cause the market price of our Common Stock to decline or cause it to be highly volatile. A substantial majority of the outstanding shares of our Common Stock are, and all of the shares sold in this offering will be, freely tradable without restriction or further registration under the Securities Act, unless these shares are owned or purchased by “affiliates” as that term is defined in Rule 144 under the Securities Act. In addition, we have also registered the shares of Common Stock that we may issue under our equity incentive plans. As a result, these shares can be freely sold in the public market upon issuance, subject to restrictions under securities laws.

Common Stock representing a substantial percentage of our outstanding shares are being sold in this offering, which could cause the price of our shares to decline.

We are selling 335,001 shares of our Common Stock in this offering, or approximately 16% of our Common Stock outstanding, prior to this offering, as of August 7, 2026. This sale and any future sales of a substantial number of shares of Common Stock in the public market, or the perception that such sales may occur, could adversely affect

the price of the Common Stock on the Nasdaq Capital Market. We cannot predict the effect, if any, that market sales of the Common Stock or the availability of the Common Stock for sale will have on the market price of the Common Stock.

There is no public market for the Pre-Funded Warrants or the August 2026 Warrants in this offering.

There is no public trading market for the Pre-Funded Warrants or the August 2026 Warrants, and we do not expect a market to develop. In addition, we do not intend to apply to list the Pre-Funded Warrants or the August 2026 Warrants on any securities exchange or nationally recognized trading system, including Nasdaq. Without an active market, the liquidity of the Pre-Funded warrants or warrants will be limited.

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

The Pre-Funded Warrants are exercisable for $0.01 per share of Common Stock underlying such Pre-Funded Warrants or they may be exercised by way of a cashless exercise, meaning that the holders may not pay a cash purchase price upon exercise, but instead would receive upon such exercise the net number of shares of our Common Stock determined according to the formula set forth in the Pre-Funded warrants. Accordingly, we may not receive a significant amount or any additional funds upon the exercise of the Pre-Funded Warrants.

The holders of the Pre-Funded Warrants and August 2026 Warrants purchased in this offering will have no rights as holders of our Common Stock with respect to the shares of Common Stock underlying such Pre-Funded Warrants and August 2026 Warrants until such holders exercise the Pre-Funded Warrants and August 2026 Warrants and acquire our Common Stock.

Until a holder of the Pre-Funded Warrants and/or August 2026 Warrants acquires shares of our Common Stock upon exercise, such holder will have no rights with respect to the shares of our Common Stock underlying such Pre-Funded Warrants and/or August 2026 Warrants including with respect to dividends and voting rights. Upon exercise of the Pre-Funded Warrants and/or August 2026 Warrants, such holder will be entitled to exercise the rights of a holder of our Common Stock with respect to the shares of Common Stock underlying such warrants only as to matters for which the record date occurs after the exercise date.

Because we do not anticipate paying any cash dividends on our capital stock in the foreseeable future, capital appreciation, if any, will be your sole source of gain.

We have never declared nor paid cash dividends on our Common Stock. We currently plan to retain all of our future earnings, if any, to finance the operation, development and growth of our business. In addition, the terms of any future debt or credit agreements may preclude us from paying dividends. As a result, capital appreciation, if any, of our Common Stock will be your sole source of gain for the foreseeable future.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS AND INDUSTRY DATA

This prospectus contains forward-looking statements. Certain statements in this prospectus may constitute “forward-looking statements” for purposes of the federal securities laws. Our forward-looking statements include, but are not limited to, statements regarding 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,” “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:

• the initiation, timing, progress and results of future preclinical studies and clinical trials, and our research and development program for emavusertib;

• our estimates of the period in which we anticipate that existing cash and cash equivalents will enable us to fund our current and planned operations;

• our ability to continue as a going concern;

• our ability to obtain additional financing;

• our ability to establish and maintain collaborations;

• our plans to develop and commercialize emavusertib;

• the timing or likelihood of regulatory filings and approvals;

• the implementation of our business model and strategic plans for our business, drug candidate and technology;

• our estimates regarding expenses, future revenue and capital requirements;

• developments and projections relating to our competitors and our industry;

• our commercialization, marketing and manufacturing capabilities and strategy;

• the rate and degree of market acceptance and clinical utility of our products;

• our ability to continue meeting the listing standards of The Nasdaq Stock Market LLC;

• our competitive position; and

• our intellectual property position.

Our actual results may differ materially from those indicated by these forward-looking statements as a result of various important factors, including the factors referred to under the heading “Risk Factors” beginning on page 8 of this prospectus and in the “Risk Factors” sections of our Annual Report on Form 10-K for the fiscal year ended December 31, 2025 and our Quarterly Report on Form 10-Q for the quarter ended March 31, 2026. If one or more of these factors materialize, or if any underlying assumptions prove incorrect, our actual results, performance or achievements may vary materially from any future results, performance or achievements expressed or implied by these forward-looking statements.

You should consider these factors and the other cautionary statements made in this prospectus and the documents we incorporate by reference herein and therein as being applicable to all related forward-looking statements wherever they appear in this prospectus or the documents incorporated by reference. While we may elect to update forward-looking statements wherever they appear in this prospectus or the documents incorporated by reference herein and therein, we do not assume, and specifically disclaim, any obligation to do so, whether as a result of new information, future events or otherwise, except as required by law.

This prospectus and the documents incorporated by reference herein and therein include statistical and other industry and market data that we obtained from industry publications and research, surveys, and studies conducted by third parties as well as our own estimates. All of the market data used in this prospectus and the documents incorporated by reference herein and therein involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such data. Industry publications and third-party research, surveys, and studies generally indicate that their information has been obtained from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. Our estimates of the potential market opportunities for our product candidates include several key assumptions based on our industry knowledge, industry publications, third-

party research, and other surveys, which may be based on a small sample size and may fail to accurately reflect market opportunities. While we believe that our internal assumptions are reasonable, no independent source has verified such assumptions.

USE OF PROCEEDS

The net proceeds of the sale of shares of Common Stock and Pre-Funded warrants in this offering will be approximately $4.8 million at the combined public offering price of $1.50 per share and accompanying warrant (or at the combined public offering price of $1.49 per Pre-Funded warrant and accompanying common warrant) after deducting estimated placement agents fees and expenses and estimated offering expenses payable by us.

As of March 31, 2026, we had cash and cash equivalents of $15.0 million. We currently intend to use the net proceeds from this offering to fund our research and development activities and for working capital and general corporate purposes. Accordingly, we will retain broad discretion over the use of the net proceeds from the sale of our securities pursuant to this prospectus. The precise amount and timing of the application of such proceeds will depend upon our liquidity needs and the availability and cost of other capital over which we have little or no control.

Pending the use of the proceeds from this offering, we intend to invest the net proceeds in short-term, interest-bearing, investment-grade securities, certificates of deposit or government securities.

SELECTED FINANCIAL DATA

The following selected financial data has been derived from our audited financial statements in Curis’s Annual Report on Form 10-K for the year ended December 31, 2025 filed with the Commission on March 24, 2026 and our Quarterly Report on Form 10-Q for the period ended March 31, 2026 filed with the Commission on May 13, 2026, as adjusted to reflect the 1-for-20 reverse stock split effected on July 2, 2026 for all periods presented. Our historical results are not indicative of the results that may be expected in the future.

AS REPORTED (in thousands, except share and per share amounts)


	Three Months Ended March 31,				Year Ended December 31,
		2026		2025		2025		2024
	(unaudited)
Net loss	$	(24,199)	$	(10,616)	$	(7,582)	$	(43,389)
Net loss per share, basic and diluted	$	(1.25)	$	(1.25)	$	(0.58)	$	(6.88)
Weighted-average shares outstanding, basic and diluted		19,363,478		8,493,886		13,164,032		6,306,284
Common shares outstanding		39,978,693		10,462,250		12,928,853		8,487,818

AS ADJUSTED (in thousands, except share and per share amounts)


	Three Months Ended March 31,				Year Ended December 31,
		2026		2025		2025		2024
	(unaudited)
Net loss	$	(24,199)	$	(10,616)	$	(7,582)	$	(43,389)
Net loss per share, basic and diluted	$	(24.99)	$	(24.99)	$	(11.52)	$	(137.61)
Weighted-average shares outstanding, basic and diluted		968,276		424,781		658,297		315,315
Common shares outstanding		1,999,041		523,202		646,537		424,478

CAPITALIZATION

The following table sets forth our capitalization as of March 31, 2026 as follows:

•on an actual basis; and

•on an as adjusted basis to give effect to the issuance and sale in this offering of 335,001 shares of Common Stock at the combined public offering price of $1.50 per share and accompanying warrant and 3,398,333 pre-funded warrants at the combined public offering price of $1.49 per pre-funded warrant and accompanying warrant, after deducting the estimated Placement Agents fees and estimated offering expenses payable by us, as if such issuances and sales had occurred on March 31, 2026.

The following depiction of our capitalization on an as adjusted basis as of March 31, 2026 reflects the completion of this offering and does not reflect exercise of any options or warrants. The adjusted amounts shown below represent management’s estimate. The information in this table should be read in conjunction with and is qualified by reference to the financial statements and notes thereto and other financial information incorporated by reference into this prospectus.


	As of March 31, 2026
(U.S. dollars in thousands)	Actual				As Adjusted
Cash and cash equivalents	$	15,001		$	19,802

Shareholders’ equity:
Preferred Stock, $0.01 par value			-		-
Common Stock, $0.01 par value			20		23
Additional paid-in capital			1,284,267		1,289,065
Accumulated deficit			(1,271,580)		(1,271,580)
Total shareholders’ equity	$	12,707		$	17,508

The above discussion and table are based on 1,999,041 shares of Common Stock outstanding as of March 31, 2026, after giving effect to a 1-for-20 reverse stock split of our Common Stock, which was effected on July 2, 2026, and exclude, as of such date, the shares of Common Stock underlying the Pre-Funded Warrants or August 2026 Warrants, as well as the following:

•116,456 shares of our Common Stock issuable upon the exercise of stock options outstanding at a weighted average exercise price of $313.84 per share;

•349,574 shares of our Common Stock issuable upon the exercise of stock options granted after March 31, 2026, at a weighted average exercise price of $5.29 per share;

•7,408 shares of Common Stock issuable upon the vesting of restricted stock units outstanding;

•an aggregate of 28,069 shares of Common Stock reserved for future issuance under our 2026 Incentive Plan;

•an aggregate of 17,891 shares of Common Stock reserved for future issuance under our Amended and Restated 2010 Employee Stock Purchase Plan, as amended;

•50,000 shares of Common Stock converted to pre-funded warrants;

•33,587 shares of Common Stock issued upon the exercise of pre-funded warrants;

•153,278 shares of our Common Stock issuable upon the exercise of pre-funded warrants outstanding at an exercise price of $0.20 per share;

•4,728,671 shares of our Common Stock issuable upon the exercise of warrants outstanding at a weighted average exercise price of $20.95 per share; and

•107,449 shares of Common Stock sold through our ATM Facility.

DILUTION

If you invest in our Common Stock in this offering, your ownership interest will be diluted immediately to the extent of the difference between the public offering price per share of our Common Stock and the pro forma net tangible book value per share of our Common Stock after this offering.

Our historical net tangible book value as of March 31, 2026 was $3.7 million, or $1.74 per share of our Common Stock. Historical net tangible book value per share represents the amount of our total tangible assets less total liabilities, divided by 2,135,906 shares of our Common Stock and pre-funded warrants outstanding.

After giving effect to the sale of 335,001 shares of common stock of the Company at a combined public offering price of $1.50 per share and accompanying common warrant and 3,398,333 pre-funded warrants to purchase shares of common stock at a combined public offering price of $1.49 per pre-funded warrant and accompanying common warrant, less the estimated placement agents fees and expenses and estimated offering expenses payable by us our pro forma net tangible book value as of March 31, 2026 would have been approximately $8.5 million, or approximately $1.45 per share. This represents an immediate decrease in pro forma net tangible book value per share of $0.29 to existing stockholders and immediate dilution of $0.05 in pro forma net tangible book value per share to new investors purchasing common stock in this offering.

Dilution per share to new investors is determined by subtracting pro forma net tangible book value per share after this offering from the assumed public offering price per share paid by new investors. The following table illustrates this dilution on a per share basis.


Assumed offering price per share			$	1.50
Net tangible book value per share as of March 31, 2026	$	1.74
Decrease in net tangible book value per share attributable to new investors	$	(0.29)
Pro forma net tangible book value per share after this offering			$	1.45
Dilution per share to new investors			$	0.05

The above discussion and table are based upon 1,999,041 shares of Common Stock and 136,865 pre-funded warrants outstanding as of March 31, 2026, after giving effect to a 1-for-20 reverse stock split of our Common Stock, which was effected on July 2, 2026, and exclude, as of such date, the shares of Common Stock underlying the Pre-Funded Warrants and August 2026 Warrants, as well as the following: