Cogent Biosciences Presents Full SUMMIT Results of Bezuclastinib in Patients with NonAdvanced Systemic Mastocytosis (NonAdvSM) at the 67th Annual Meeting of the American Society of Hematology (ASH)

Cogent Biosciences (NASDAQ: COGT) reported full Part 2 SUMMIT results for bezuclastinib in nonadvanced systemic mastocytosis (NonAdvSM) presented at ASH on December 6, 2025.

Rhea-AI Summary

Cogent Biosciences (NASDAQ: COGT) reported full Part 2 SUMMIT results for bezuclastinib in nonadvanced systemic mastocytosis (NonAdvSM) presented at ASH on December 6, 2025. Data show clinically meaningful, statistically significant symptomatic and objective improvements at 24 weeks with continued deepening at 48 weeks.

Key facts: 65.4% achieved ≥30% TSS reduction at 24 weeks, 87.4% had ≥50% serum tryptase reduction at week 24, and 48-week follow-up showed 56.4% achieving ≥50% TSS reduction. Breakthrough Therapy designation was granted in October 2025 and an NDA is on track for December 2025 submission.

Positive

• 65.4% of patients achieved ≥30% TSS reduction at 24 weeks
• 87.4% achieved ≥50% serum tryptase reduction at week 24
• 56.4% achieved ≥50% TSS reduction at 48 weeks (follow-up)
• NDA submission for bezuclastinib on track for December 2025

Negative

• Treatment-emergent ALT/AST elevations in 22.0% of patients (≥Gr 3 in 5.9%)
• Discontinuations due to treatment-related AEs in 5.9% (all ALT/AST elevations)
• Very high overall TEAE incidence: 98.3% on bezuclastinib vs 88.3% placebo
• Common non-serious AEs include hair color change in 69.5% of patients

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Key Figures

Bezuclastinib arm size: 118 patients Placebo arm size: 60 patients ≥50% TSS reduction: 34.3% vs 18.1% +5 more

Bezuclastinib arm size

118 patients

SUMMIT Part 2 NonAdvSM once-daily bezuclastinib plus best supportive care

Placebo arm size

60 patients

SUMMIT Part 2 NonAdvSM placebo plus best supportive care

≥50% TSS reduction

34.3% vs 18.1%

Proportion of patients at 24 weeks, bezuclastinib vs placebo; p=0.01

Serum tryptase reduction

87.4%

Patients with ≥50% reduction at week 24 on bezuclastinib

Bone marrow mast cell reduction

75.6%

Patients with ≥50% reduction or clearance of aggregates at week 24

KIT D816V VAF reduction

85.7%

Patients with ≥50% reduction or undetectable KIT D816V variant allele frequency

Serious adverse events

4.2% vs 5.0%

Serious AEs on bezuclastinib vs placebo in SUMMIT Part 2

Discontinuations due to AEs

5.9%

Bezuclastinib-treated patients; all ALT/AST-related and fully resolved

Historical Context

5 past events · Latest: Nov 14

5 events

1. Nov 14

   Conference participation

   24h Move

   -0.9%

   Announcement of participation and webcast at Jefferies Global Healthcare Conference.

2. Nov 11

   Financing priced

   24h Move

   +3.0%

   Pricing of equity and 1.625% convertible notes offerings and use-of-proceeds disclosure.

3. Nov 10

   Financing proposed

   24h Move

   +119.0%

   Announcement of proposed concurrent common stock and convertible notes offerings.

4. Nov 10

   Phase 3 results

   24h Move

   +119.0%

   Positive Phase 3 PEAK data for bezuclastinib plus sunitinib in GIST with strong efficacy.

5. Nov 03

   Earnings & pipeline

   24h Move

   -4.9%

   Q3 results with strong cash position and multiple upcoming pivotal readouts and filings.

24h Move is the share-price change in the day after each event; other market factors may also have contributed.

Key Terms

breakthrough therapy designation, new drug application (nda), serum tryptase, kit d816v, +3 more

7 terms

breakthrough therapy designation regulatory

"Granted Breakthrough Therapy Designation for bezuclastinib in October 2025; New Drug Application..."

A breakthrough therapy designation is a regulatory fast-track given to a drug or treatment that shows early signs of providing a major improvement over existing options for a serious condition. Think of it as a VIP lane that can speed up development and more intensive guidance from regulators, which matters to investors because it can shorten time to market, reduce development risk and potentially increase a company’s value — though it does not guarantee approval.

new drug application (nda) regulatory

"New Drug Application (NDA) on track for submission in December 2025..."

A new drug application (NDA) is a formal request submitted to regulatory authorities to gain approval for a new medication to be sold and used by the public. It is a comprehensive review process that examines the drug’s safety, effectiveness, and manufacturing quality. For investors, an NDA approval can signal a potential breakthrough product and influence a company's stock value.

serum tryptase medical

"reducing objective measures of disease, including serum tryptase, correlates with improvement..."

A protein measured in the blood that acts like a smoke detector for cells involved in allergic reactions: higher levels signal activation or increased number of mast cells, which occur during severe allergies, anaphylaxis, or certain blood disorders. Investors care because this lab marker drives demand for diagnostics, informs clinical trial outcomes, and can determine the need or market size for drugs and tests targeting allergic and mast-cell related conditions.

kit d816v medical

"designed to potently inhibit the KIT D816V mutation as well as other mutations..."

The KIT D816V is a specific change in a cell’s KIT gene that acts like a single-letter typo in an instruction manual, causing certain cells to grow or behave abnormally. It matters to investors because this identifiable molecular change creates a clear target for drugs and diagnostics, shaping market size, clinical trial designs, regulatory decisions and the potential commercial value of therapies aimed at patients who carry that change.

variant allele frequency medical

"achieved ≥50% reduction in KIT D816V variant allele frequency or undetectable..."

Variant allele frequency is the proportion of DNA molecules in a sample that carry a specific genetic change, usually measured by sequencing and expressed as a percentage. Think of it as the share of colored marbles in a jar: a higher share means the mutation is more common in the measured tissue or virus. For investors, VAF matters because it helps assess how strongly a mutation drives disease, how likely a targeted therapy will work, and whether resistance or diagnostic tests will be commercially relevant.

tyrosine kinase inhibitor medical

"bezuclastinib, is a selective tyrosine kinase inhibitor that is designed to potently inhibit..."

A tyrosine kinase inhibitor is a type of drug that blocks specific proteins in cells that act like on/off switches for growth and survival signals, often used to stop cancer cells from multiplying. For investors, these drugs matter because their clinical trial results, regulatory approvals, safety profiles, and patent status drive sales potential and company valuation—think of them as precision tools whose effectiveness and market exclusivity determine commercial success.

fgfr2/3 inhibitor medical

"ongoing Phase 1 study of its novel internally discovered FGFR2/3 inhibitor."

A FGFR2/3 inhibitor is a drug that blocks two specific cell-surface proteins, FGFR2 and FGFR3, which act like switches that tell cells to grow or divide. Investors watch these drugs because they are targeted therapies that can shrink tumors in cancers driven by those switches; clinical trial results, approvals, or safety issues can sharply affect a drug’s commercial value and a company’s stock, much like a product launch or recall in other industries.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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-- Bezuclastinib achieves clear clinical benefit across all symptom domains including significant improvements on 11 individual symptoms plus the most severe symptom at baseline --

-- Bezuclastinib demonstrates that reducing objective measures of disease, including serum tryptase, correlates with improvement in symptom severity; the first time this has been shown in NonAdvSM patients --

-- New 48-week data demonstrate a clear, continued deepening of symptomatic improvement over time --

-- Bezuclastinib demonstrated a favorable safety and tolerability profile supporting chronic use -- 

-- Granted Breakthrough Therapy Designation for bezuclastinib in October 2025; New Drug Application (NDA) on track for submission in December 2025 -- 

-- Cogent to host investor conference call and webcast on Monday, December 8, at 8:00 a.m. ET -- 

WALTHAM, Mass. and BOULDER, Colo., Dec. 06, 2025 (GLOBE NEWSWIRE) -- Cogent Biosciences, Inc. (NASDAQ: COGT) today announced complete results from the registration-directed Part 2 of the SUMMIT clinical trial of bezuclastinib in patients with nonadvanced systemic mastocytosis (NonAdvSM). As previously reported, bezuclastinib demonstrated clinically meaningful and highly statistically significant improvements across the primary and all key secondary endpoints. New results further highlight the benefit of bezuclastinib on patient-reported symptoms and objective measures of mast cell burden and demonstrate significant correlation between improvement in disease pathology and patient-reported symptom severity. 

“We are excited to present additional data from the SUMMIT trial that support our conviction that bezuclastinib will be the best-in-class treatment option for patients with nonadvanced systemic mastocytosis,” said Andrew Robbins, Cogent’s President and Chief Executive Officer. “We remain on track to submit our first New Drug Application for bezuclastinib in NonAdvSM with the FDA this month and are encouraged by the increased interest in our Expanded Access Program.”

“Nonadvanced systemic mastocytosis patients currently have very limited treatment options, and the benefit bezuclastinib demonstrated in the SUMMIT trial across measures of disease pathology and symptomatic improvement is very exciting for this patient population,” said Lindsay Rein, MD, Associate Professor of Medicine in the Division of Hematologic Malignancies and Cellular Therapy, Duke University. “The SUMMIT trial results match my clinical experience using bezuclastinib with NonAdvSM patients, delivering rapid and deep improvement in symptom control and objective measures of disease without tolerability challenges.”

SUMMIT Trial Data 

In the registration-directed Part 2 of the SUMMIT clinical trial, 118 patients received bezuclastinib once daily plus best supportive care (BSC) and 60 patients received placebo plus BSC. The study included adults with a NonAdvSM diagnosis confirmed by central pathology review, and moderate-to-severe symptom burden despite an optimized regimen of BSC. 

Following completion of the 24-week treatment period, patients had the option to receive bezuclastinib in an open-label extension study. Baseline patient demographics were balanced between treatment arms and reflected significant disease burden. Disease symptoms were assessed using the Mastocytosis Symptom Severity Daily Diary (MS2D2).

Bezuclastinib delivered clinically meaningful and statistically significant symptomatic improvement

Outcome measure	Bezuclastinib	Placebo	p-value
At 24 weeks of treatment (primary endpoint and key secondary endpoints)
Mean change TSS (%)	-24.3 (-43%)	-15.4 (-29%)	p<0.001
Proportion of patients with ≥50% reduction in TSS	34.3%	18.1%	p=0.01
Proportion of patients with ≥30% reduction in TSS	65.4%	38.6%	p<0.001
For patients treated through 48 weeks (follow-up data cut off Nov 2025)
Mean change TSS (%)	-32.0 (-54%)	n/a	n/a
Proportion of patients with ≥50% reduction in TSS	56.4%	n/a	n/a
Proportion of patients with ≥30% reduction in TSS	86.2%	n/a	n/a

Across several additional key secondary endpoints, bezuclastinib demonstrated rapid, deep and sustained improvement on objective disease markers of mast cell burden. At week 24, 87.4% of patients achieved ≥50% reduction in serum tryptase levels, 75.6% of patients demonstrated ≥50% reduction in bone marrow mast cells or clearance of aggregates and 85.7% of patients achieved ≥50% reduction in KIT D816V variant allele frequency or undetectable, each of which was statistically significant when compared to placebo. Additional pathobiology data from SUMMIT patients will be shared in an oral presentation on Monday, December 8^th at ASH.

SUMMIT Subgroups

As part of the SUMMIT study, patients with Smoldering Systemic Mastocytosis (n=8 bezuclastinib arm, n=4 placebo arm) and patients who had previously been treated with avapritinib (n=11 bezuclastinib arm, n=3 placebo arm) were enrolled. Patients treated with bezuclastinib in these subgroups showed a mean change in TSS of -35.6 and -21.6, respectively. The response in objective measures of disease burden in these patients was consistent with results from the broader SUMMIT population, as were their related adverse events and overall tolerability.

Safety Data 

As previously reported on July 7, 2025, the majority of treatment emergent adverse events (TEAEs) (98.3% in bezuclastinib arm vs. 88.3% in placebo arm) were of low grade. The most frequent TEAEs reported on bezuclastinib treatment were hair color change (69.5% bezuclastinib vs. 5.0% placebo), altered taste (23.7% bezuclastinib vs. 0% placebo), nausea (22.0% bezuclastinib vs. 13.3% placebo) and ALT/AST elevations (22.0% bezuclastinib vs. 6.6% placebo; ≥Gr 3, 5.9% vs. 0%). Serious AEs occurred in 4.2% of patients treated with bezuclastinib, compared to 5.0% of patients treated with placebo. Discontinuations due to treatment-related AEs occurred in 5.9% of patients treated with bezuclastinib, all due to ALT/AST elevations and all patients fully resolved. There were no hepatic AEs reported in any patient other than transient and manageable lab abnormalities.

SUMMIT Long Term Follow-up

Data from longer term follow-up in patients participating in the SUMMIT trial are expected to be presented at an upcoming scientific meeting in Q1 2026. Preliminary 48-week data will be shared during the investor call scheduled for Monday, December 8^th.

Webcast Information  

Cogent will host a live webcast on Monday, December 8, at 8:00 a.m. ET to discuss these additional data from SUMMIT in NonAdvSM. The live event will be available on the Investors & Media page of Cogent’s website at investors.cogentbio.com. A replay of the webcast will be available approximately two hours after the completion of the event and will be archived for up to 30 days.

About Cogent Biosciences, Inc.
Cogent Biosciences is a biotechnology company focused on developing precision therapies for genetically defined diseases. The most advanced clinical program, bezuclastinib, is a selective tyrosine kinase inhibitor that is designed to potently inhibit the KIT D816V mutation as well as other mutations in KIT exon 17. KIT D816V is responsible for driving systemic mastocytosis, a serious disease caused by unchecked proliferation of mast cells. Exon 17 mutations are also found in patients with advanced gastrointestinal stromal tumors (GIST), a type of cancer with strong dependence on oncogenic KIT signaling. The company also has an ongoing Phase 1 study of its novel internally discovered FGFR2/3 inhibitor. In addition, the Cogent Research Team is developing a portfolio of novel targeted therapies to help patients fighting serious, genetically driven diseases targeting mutations in ErbB2, PI3Kα, KRAS and JAK2. Cogent Biosciences is based in Waltham, MA and Boulder, CO. Visit our website for more information at www.cogentbio.com. Follow Cogent Biosciences on social media: X (formerly known as Twitter) and LinkedIn. Information that may be important to investors will be routinely posted on our website and X.

Forward Looking Statements
This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding: plans to submit an NDA to the FDA for bezuclastinib in patients with NonAdvSM in December 2025; the company’s belief that bezuclastinib will be the best-in-class treatment option for NonAdvSM patients and plans to present data from longer term follow-up in patients participating in the SUMMIT trial at an upcoming scientific meeting in Q1 2026. The use of words such as, but not limited to, "anticipate," "believe," "continue," "could," "estimate," "expect," "intend," "may," "might," "plan," "potential," "predict," "project," "should," "target," "will," or "would" and similar words or expressions are intended to identify forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on our current beliefs, expectations and assumptions regarding the future of our business, future plans and strategies, our clinical results, the rate of enrollment in our clinical trials and other future conditions. New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements. We may not actually achieve the forecasts or milestones disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Such forward-looking statements are subject to a number of material risks and uncertainties including but not limited to those set forth under the caption "Risk Factors" in Cogent's most recent Annual Report on Form 10-K filed with the SEC. Any forward-looking statement speaks only as of the date on which it was made. Neither we, nor our affiliates, advisors or representatives, undertake any obligation to publicly update or revise any forward-looking statement, whether as result of new information, future events or otherwise, except as required by law. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date hereof. 

Contact: 
Christi Waarich 
Senior Director, Investor Relations 
christi.waarich@cogentbio.com 
617-830-1653    

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did Cogent Biosciences (COGT) announce about bezuclastinib on December 6, 2025?

Cogent reported full Part 2 SUMMIT results showing statistically significant symptom and objective improvements in NonAdvSM and said an NDA is on track for December 2025.

How effective was bezuclastinib in reducing symptoms in the SUMMIT trial (COGT)?

At 24 weeks, 65.4% achieved ≥30% TSS reduction and 34.3% achieved ≥50% TSS reduction versus placebo.

What objective disease marker improvements did COGT report for bezuclastinib at week 24?

87.4% showed ≥50% serum tryptase reduction; 75.6% had ≥50% bone marrow mast cell reduction or clearance; 85.7% had ≥50% KIT D816V VAF reduction or undetectable.

Did Cogent (COGT) report longer-term symptomatic benefit for bezuclastinib?

Yes — 48-week data showed deeper benefit with 56.4% achieving ≥50% TSS reduction and 86.2% achieving ≥30% TSS reduction in treated patients.

What safety signals did the SUMMIT results for COGT highlight?

Most TEAEs were low grade, but ALT/AST elevations occurred in 22.0% (≥Gr 3 in 5.9%), discontinuations for treatment-related AEs were 5.9%, and hair color change occurred in 69.5%.

Will Cogent (COGT) provide more details and when can investors hear them?

Cogent will host a live webcast and investor call on December 8, 2025 at 8:00 a.m. ET to discuss additional SUMMIT data.