Cogent Biosciences Inc. (NASDAQ:COGT) surged 12.6% in Monday’s premarket session after unveiling encouraging top-line findings from APEX Part 2, its registration-directed Phase 2/3 study evaluating bezuclastinib in advanced systemic mastocytosis (AdvSM).
The company reported a 57% objective response rate based on mIWG criteria and an 80% response rate per PPR criteria. Additionally, 89% of patients saw substantial reductions in bone marrow mast cells. Bezuclastinib continued to exhibit a clean safety profile, with no participants discontinuing treatment due to adverse events.
These results represent the therapy’s third positive pivotal readout in 2025, following earlier successes in NonAdvSM and GIST. Cogent said it is preparing to file a new drug application with the FDA in the first half of 2026.
Commenting on the data, Daniel J. DeAngelo, M.D., Ph.D., Chief of the Division of Leukemia at Dana-Farber Cancer Institute, said, “Bezuclastinib demonstrated the rapid, deep clinical activity we were expecting given its earlier clinical results. What is most exciting about these data is the impressive safety and tolerability results with no discontinuations due to treatment-related adverse events and only infrequent dose modifications. With this profile, bezuclastinib will become an important treatment option for this patient population.”
The study enrolled 81 AdvSM patients treated with 150 mg of bezuclastinib. Median time to response was 2.0 months, and several participants achieved unconfirmed responses while remaining on therapy awaiting further assessment.
The most frequent treatment-related side effects included hair-color changes (30.9%), neutropenia (29.6%), altered taste (28.4%), and thrombocytopenia (24.7%). Only 14.8% required dose reductions.
Analysts remained constructive: Stifel’s Laura Prendergast reiterated a Buy rating with a $40 target, while Raymond James’ Chris Raymond kept a Strong Buy and a $60 target on the shares.