On December 9, 2023, Cogent Biosciences, Inc. announced positive initial data from the Company's ongoing Phase 2 APEX clinical trial evaluating bezuclastinib in patients with nonadvanced systemic mastocytosis ("NonAdvSM") at the 65th American Society of Hematology ("ASH 2023") Annual Meeting & Exposition taking place December 9-12, 2023 in San Diego, CA. On December 11, 2023, the Company announced positive data from Part 1 of the Company's ongoing Phase 2APEX clinical trial evaluating bezu Clastinib in patients with NonAdvSM ("AdvSM"), which data is also being presented at ASH 2023. Phase 2 SUMMIT Trial: Phase 2 SUMMIT is a randomized, double-blind, placebo-controlled, global, multicenter, Phase 2 clinical trial of bezuclast in patients with NonAdvSM.

Twenty patients in Part 1a were treated with either bezuclastinib or placebo plus best supportive care for all arms. By week 20, bezuclastinib patients increased median best improvement to 57% on MC-QoL Patients who crossed over from placebo to bezuclastinib, showed median best improvement on MC-QoL of 75% by week 8 of active treatment. At week 12, bezuclastinIB patients showed a 35% change from baseline on MAS vs. a 28% change from baseline for placebo.

For bezuclastinib patient treated at 100 mg QD, the MAS improvement from baseline at week 12 was 49% At week 12, 63% of bezuclastinib Patients showed a 1 point improvement on PGIS (5 point scale) compared with 0% of placebo patients. At week 20, this increased to 78% of bezuclast in Part 1 and plans to initiate SUMMIT Part 2, a registration-directed, global, randomized placebo-controlled trial in the first half of 2024. In addition, the Company plans to present data from the completed SUMMIT Part 1 trial (1a and 1b), including all 54 patients enrolled across Part 1a and Part 1b, in the first quarter of 2024; the potential of bezuclastinIB to become a new treatment option patients with AdvSM; the expectation for the Company to complete enrollment of approximately 65 patients in Part 2 of APEX by the end of 2024; that the 150 mg QD optimized formulation dose selected for APEX Part 2 is expected to deliver patient exposures consistent with the 100 mg BID Part 1 cohort; and plans to complete enrollment in PEAK by the end of 2024 with over 10 mg BID.