On June 12, 2026 Cogent Biosciences, Inc. (Nasdaq: COGT), a biotechnology company focused on developing precision therapies for genetically defined diseases, reported detailed and updated clinical results from the registration-directed APEX clinical trial of bezuclastinib in patients with advanced systemic mastocytosis (AdvSM) demonstrating clinically meaningful results as measured by consensus criteria used to assess patient response. The company also shared a more detailed review of the pathobiology data in AdvSM patients from the APEX trial, reinforcing the rapid and deep clinical benefit bezuclastinib has demonstrated in these patients. The data will be presented at the 2026 European Hematology Association (EHA) (Free EHA Whitepaper) Congress taking place in Stockholm, Sweden, June 11-14, 2026.

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"We are excited to share updated and detailed results from the APEX trial in AdvSM patients, building upon previously announced results from bezuclastinib in the SUMMIT trial in NonAdvSM patients," said Andrew Robbins, Cogent’s President and Chief Executive Officer. "The results shown across these two trials demonstrate that a selective, potent KIT D816V inhibitor like bezuclastinib will have tremendous opportunity to become the new standard of care and change the lives of patients living with systemic mastocytosis. We are on track to complete the APEX NDA submission in the very near future and plan to launch bezuclastinib later this year in both systemic mastocytosis and GIST following FDA approval."

As of the updated data cutoff of March 31, 2026 in Part 2 of the APEX trial, 81 AdvSM patients were treated with 150 mg of bezuclastinib, including 57 patients with SM-AHN, 11 patients with ASM and 13 patients with MCL. The primary endpoint of response per mIWG-MRT-ECNM was assessed on 68 evaluable patients and showed 65% ORR (CR+CRh+PR+CI), including 57% of patients who achieved CR, CRh or PR as best response.

Additional highlights include:

Key secondary endpoint of response per pure pathological response (PPR) criteria was assessed on 81 patients which showed an 81% ORR (CR+CRh+PR).
Bezuclastinib demonstrated reversal of bone marrow pathobiology including rapid and deep reductions in aberrant CD25 and CD30 expression, normalization of mast cell morphology, normalization of bone marrow cellularity, and improvement in myelofibrosis.
Bezuclastinib demonstrated durable clinical activity and prolonged PFS with a 12-month PFS rate of 79% and a 12-month OS rate of 87%. Median duration of PFS and OS were immature at the time of the data cutoff.
Bezuclastinib achieved clear and clinically significant reductions in objective disease markers for these AdvSM patients:
Outcome measure Bezuclastinib
Proportion with ≥50% reduction in serum tryptase (n=80) 89 %
Proportion with ≥50% reduction in bone marrow mast cells or clearance of aggregates (n=80) 89 %
Proportion with ≥50% reduction in KIT D816V variant allele frequency (n=43) 91 %

"The results from the APEX trial demonstrate clear evidence of bezuclastinib’s rapid and deep clinical activity in patients with advanced systemic mastocytosis," said Daniel J. DeAngelo, M.D., Ph.D., Chief of the Division of Leukemia at the Dana-Farber Cancer Institute and Professor of Medicine, Harvard Medical School. "Coupled with an impressive safety and tolerability profile minimizing off-target toxicities that allows for long-term therapeutic dosing, bezuclastinib will become an important treatment option for patients with advanced SM."

Pathobiology Data

Cogent will also present new data highlighting the impact bezuclastinib has at a cellular level in patients with AdvSM. In the APEX study, bezuclastinib demonstrated robust improvement in disease pathology, with effects observed as early as eight weeks, including high PPR rates, improvement (including normalization) in bone marrow mast cell distribution, improvement in broader bone marrow characteristics and a majority of patients achieving normalization of serum tryptase. In addition, approximately one-third of patients treated with bezuclastinib achieved undetectable levels of KIT D816V VAF, signifying modification of the underlying AdvSM disease with bezuclastinib treatment.

APEX Safety and Tolerability

As of the data cutoff, bezuclastinib continued to be well-tolerated, with infrequent need for dose reduction or discontinuation for treatment-related adverse events (TRAEs). The most frequent TRAEs reported on bezuclastinib treatment were hair color change (31%), neutropenia (31%), altered taste (28%), thrombocytopenia (25%), and ALT/AST elevations (21%). The majority of transaminase elevations were of low grade, asymptomatic and reversible. Of the two patients who experienced Grade 3 transaminase elevation, one discontinued treatment and one remains on therapy following dose reduction.

The EHA (Free EHA Whitepaper) posters and presentation will be available on the Cogent website at: View Source

Bezuclastinib – Expanded Access Program

Working with the FDA, Cogent has established active Expanded Access Programs (EAPs) for U.S. patients SM or GIST who meet disease-specific criteria and could benefit from treatment with bezuclastinib or the combination of bezuclastinib and sunitinib. For more information please visit: View Source

(Press release, Cogent Biosciences, JUN 12, 2026, View Source [SID1234666607])