Cogent Biosciences, Inc. reported positive data from Part 1 of the Company's ongoing Phase 2 APEX clinical trial evaluating bezuclastinib in patients with advanced systemic mastocytosis (AdvSM) at the 65th American Society of Hematology (ASH 2023) Annual Meeting & Exposition taking place December 9-12, 2023 in San Diego, CA. APEX is a global, open-label, multi-center, two-part Phase 2 clinical trial in patients with AdvSM evaluating the safety, efficacy, pharmacokinetic, and pharmacodynamic profiles of bezuclastinib. As of the data cutoff date of September 25, 2023, 32 patients were treated in Part 1 at one of four dose levels (50 mg BID, 100 mg BID, 200 mg BID or 400 mg QD).

(CR+CRh+PR) per mIWG-MRT-ECNM criteria, including 56% ORR r TKI-treatment-nave patients; 100% of patients treated with 100 mg BID achieved PR or better and all remain on study; 150 mg QD optimized formulation dose selected for APEX Part 2 is expected to deliver patient exposures consistent with this cohort; 75% ORR (CR+PR) per pure pathological response (PPR) criteria, including86% ORR for TKI-treatment-nav patients; Nearly all patients demonstrated a significant improvement in biomarkers associated with disease burden; 94% of patients achieved =50% reduction in serum tryptase levels; 100% of patients receiving =2 cycles achieved =50% reduction; 53% of patients achieved reduction of serum tryptase below 20 ng/mL; 93% of KITD816V-positive patients achieved =50% reduction In KIT D816V variant allele fraction (VAF); 97% of patients achieved a =50% reduction in bone marrow mast cell burden; 79% achieved complete clearance of mast cell aggregates by central review. Cogent continues to actively enroll Pt 2 of the APEX trial which is expected to include approximately 65 AdvSM patients and is on track to complete enrollment by the end of 2024. Cogent reported positive initial Part 1a data on December 9, 2023 from SUMMIT, a Phase 2 clinical trial of bezuclastinIB in patients with nonadvanced systemic mastocytosis (NonAdvSM), showing rapid improvement in patient symptoms and improvement across all biomarkers with a safety and tolerability profile that supports the potential for chronic chronic mastocytosis (Adv SM), showing rapid improvement in patient conditions and improvement across all biomarkers With a safety and tolerability profile and tolerability profile that supports The potential for chronic chronic mastocyTosis (AdvSM) and is expected to bezuclastinib is expected to include approximately 65AdvSM patients and is on track.