Quince Therapeutics to Participate at A-T Society's 2025 A-T Clinical Research Conference

Phase 3 NEAT enrollment momentum continues with 99 total participants enrolled to date

Quince Therapeutics, Inc. (NASDAQ:QNCX), a late-stage biotechnology company dedicated to unlocking the power of a patient's own biology for the treatment of rare diseases, today announced its participation at the upcoming 2025 A-T Clinical Research Conference organized by the A-T Society, a leading Ataxia-Telangiectasia (A-T) patient advocacy group based in the United Kingdom. Taking place June 25-27, 2025 at Loughborough University in the U.K., key opinion leaders (KOLs) will present post hoc data analyses from the company's prior Phase 3 ATTeST clinical trial of its lead asset, eDSP, for the treatment of patients with A-T. Additionally, Quince management will provide an overview of its pivotal Phase 3 NEAT clinical trial.

Highlights of A-T Clinical Research Conference Presentations

KOLs will present the following data and information at the upcoming A-T Clinical Research Conference:

• Endocrine and Metabolic Events in Patients with A-T Treated with eDSP: William Whitehouse, M.D., Honorary Clinical Associate Professor of the School of Medicine at the University of Nottingham, England, recently retired Consultant Pediatric Neurologist at Nottingham Children's Hospital, Nottingham University Hospitals NHS Trust, and current Quince Scientific Advisory Board member, will provide a presentation titled Endocrine and Metabolic Events in Children with Ataxia-Telangiectasia Treated Long-term with Erythrocyte-Delivered Encapsulated Dexamethasone Sodium Phosphate (eDSP). The objective of the data analysis was to evaluate metabolic and endocrine adverse events (AEs), growth, and safety laboratory results in patients with A-T treated with eDSP. Key findings reported in Dr. Whitehouse's presentation highlighted that there were no reports of serious metabolic or endocrine events in the 68 patients with A-T treated with eDSP for two years or longer. Growth in height of these patients was also preserved.

• MiniATM Family Expression in Patients with A-T Treated with eDSP: Michele Menotta, Ph.D., Associate Professor in the Department of Biomolecular Sciences at the University of Urbino in Urbino, Italy, will provide a presentation titled MiniATM Family Expression in ATTeST: Molecular Insights into Unusual ATM Variants in A-T Cells. The objective of the data analysis investigates the potential relationship between miniATM family expression in the blood of patients with A-T who participated in Quince's prior Phase 3 ATTeST clinical trial and their corresponding neurological scores. Additionally, novel functions of the miniATM family were explored in A-T cells and its molecular mechanism of action was investigated. The analysis found that miniATM genes were present in 40% of patients with A-T and were correlated with A-T disease severity at baseline. Lab tests also showed results that may variably influence cell processes, offering new insights for potential treatments.

Pivotal Phase 3 NEAT Enrollment Update

Quince's management will provide an overview of the company's pivotal Phase 3 NEAT (Neurologic Effects of eDSP on Subjects with A-T; #IEDAT-04-2022/NCT06193200) clinical trial and latest enrollment update at the A-T Society meeting. A total of 99 participants have been enrolled to date, including 78 participants in the six to nine year-old primary analysis population and 21 participants aged 10 years or older. All 42 NEAT participants to date have elected to transition to the NEAT open label extension (OLE) study (NCT06664853/IEDAT-04-2022).

Quince is currently enrolling a pivotal Phase 3 NEAT clinical trial, which is an international, multi-center, randomized, double-blind, placebo-controlled clinical trial evaluating the neurological effects of eDSP (previously referred to as EryDex) treatment in patients with A-T. The company expects to report topline results in the first quarter of 2026 with a potential New Drug Application (NDA) submission to the FDA in the second half of 2026, assuming positive study results. Quince was granted Fast Track designation by the FDA for the company's eDSP System for the treatment of patients with A-T based on the potential for eDSP to address a high unmet medical need.

About Ataxia-Telangiectasia

A-T is an inherited autosomal recessive neurodegenerative and immunodeficiency disorder caused by mutations in the ATM gene, which is responsible for cell homeostatic and cell division functions including but not limited to double-stranded DNA repair. Typically, A-T is first diagnosed before the age of five as children begin to develop an altered gait and fall with greater frequency. Neurological symptoms worsen and patients with A-T frequently become wheelchair-bound by adolescence. Teenage years for patients with A-T are typically marked by repeated infections, pulmonary impairment, and malignancies. The median lifespan is approximately 25 to 30 years old with mortality due to infections and malignancy. Based on IQVIA Medical Claims (Dx), PharmetricsPlus (P+), and IQVIA Analytics information, there are approximately 4,600 diagnosed patients with A-T in the U.S. Quince estimates that there are approximately 5,000 patients with A-T in the U.K. and EU4 countries. There are currently no approved therapeutic treatments in any global market for A-T.

About eDSP for A-T

eDSP is comprised of dexamethasone sodium phosphate (DSP) encapsulated in a patient's own red blood cells (autologous erythrocytes). DSP is a corticosteroid well known for its anti-inflammatory properties as well as its dose-limiting toxicity due to adrenal suppression. The eDSP System is designed to provide the efficacy of corticosteroids and to reduce or eliminate the significant adverse effects that accompany chronic use of corticosteroid treatment.

eDSP leverages Quince's proprietary Autologous Intracellular Drug Encapsulation, or AIDE, technology platform, which is a novel drug/device combination that uses an automated process designed to encapsulate a drug into the patient's own red blood cells. Red blood cells have several characteristics that make them a potentially effective vehicle for drug delivery, including potentially better tolerability, enhanced tissue distribution, reduced immunogenicity, and prolongation of circulating half-life. Quince's AIDE technology is designed to harness these benefits to allow for the chronic administration of drugs that have limitations due to toxicity, poor biodistribution, suboptimal pharmacokinetics, or immune response.

About Quince Therapeutics

Quince Therapeutics, Inc. (NASDAQ:QNCX) is a late-stage biotechnology company dedicated to unlocking the power of a patient's own biology for the treatment of rare diseases. For more information on the company and its latest news, visit www.quincetx.com and follow Quince on social media platforms LinkedIn, Facebook, X, and YouTube.

Forward-looking Statements

Statements in this news release contain "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995 as contained in Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended, which are subject to the "safe harbor" created by those sections. All statements, other than statements of historical facts, may be forward-looking statements. Forward-looking statements contained in this news release may be identified by the use of words such as "believe," "may," "should," "expect," "anticipate," "plan," "believe," "estimated," "potential," "intend," "will," "can," "seek," or other similar words. Examples of forward-looking statements include, among others, statements relating to the timing, success, and reporting of results of the clinical trials and related data, including plans and the ability to enroll participants, impact of closing enrollment, conduct, and/or complete current and additional studies; expected cash position and operating runway; ability to secure additional funding and financial support; current and future clinical development of eDSP, including for the potential treatment of Ataxia-Telangiectasia (A-T), Duchenne muscular dystrophy (DMD), and other potential indications; the strategic development path for eDSP; planned regulatory agency submissions and clinical trials and timeline, prospects, and milestone expectations; and the potential benefits of eDSP and the company's market opportunity. Forward-looking statements are based on Quince's current expectations and are subject to inherent uncertainties, risks, and assumptions that are difficult to predict and could cause actual results to differ materially from what the company expects. Further, certain forward-looking statements are based on assumptions as to future events that may not prove to be accurate. Factors that could cause actual results to differ include, but are not limited to, the risks and uncertainties described in the section titled "Risk Factors" in the company's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on May 13, 2025, and other reports as filed with the SEC. Forward-looking statements contained in this news release are made as of this date, and Quince undertakes no duty to update such information except as required under applicable law.

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Media & Investor Contact:

Stacy Roughan

Quince Therapeutics, Inc.

Vice President, Corporate Communications & Investor Relations

[email protected]