Jack Shuang Hou: Bezuclastinib Demonstrates Disease-Modifying Potential in Advanced Systemic Mastocytosis
Jack Shuang Hou, Diagnostic Executive, Microfluidics and Immunoassay Specialist, shared a post on LinkedIn:
“Cogent Biosciences reports Phase 3 APEX data with 65 percent ORR and 91 percent KIT D816V reduction, advancing Bezuclastinib toward FDA submission in Advanced Systemic Mastocytosis.
New data presented at EHA 2026 highlight the potential of Bezuclastinib, a selective KIT D816V inhibitor, to become a new standard of care for patients with advanced systemic mastocytosis (AdvSM), supported by deep clinical responses, disease modification, and favorable tolerability.
1. Strong Clinical Responses Across Advanced SM Subtypes.
The pivotal APEX trial reported a 65 percent ORR (CR plus CRh plus PR plus CI) by mIWG criteria, including 57 percent of patients achieving CR, CRh, or PR as their best response.
Response rates increased to 81 percent using pure pathological response (PPR) criteria.
At 12 months, progression-free survival reached 79 percent, while overall survival reached 87 percent.
2. Evidence of Deep Disease Modification.
91 percent of patients achieved greater than or equal to 50 percent reduction in KIT D816V variant allele frequency.
89 percent achieved greater than or equal to 50 percent reduction in bone marrow mast cells or complete clearance of mast cell aggregates.
89 percent achieved greater than or equal to 50 percent reduction in serum tryptase levels.
Approximately one-third of patients achieved undetectable KIT D816V levels, supporting potential disease-modifying activity.
3. Favorable Safety Profile Supports Long-Term Treatment.
Bezuclastinib remained well tolerated with infrequent dose reductions or discontinuations.
Most common treatment-related adverse events included hair color change (31 percent), neutropenia (31 percent), altered taste (28 percent), thrombocytopenia (25 percent), and reversible liver enzyme elevations (21 percent).
Cogent remains on track to submit its NDA in June 2026 and plans potential commercial launch following FDA approval.
Leadership Perspective
Andy Robbins, President and CEO of Cogent Biosciences, stated that results from both the APEX and SUMMIT programs position bezuclastinib to potentially become a new standard of care across systemic mastocytosis and KIT-driven diseases.
Daniel DeAngelo, Dana-Farber Cancer Institute, highlighted the combination of rapid, deep clinical activity and favorable tolerability as key differentiators for long-term AdvSM management.
My Takeaway
Advanced systemic mastocytosis remains a rare but highly challenging disease driven largely by KIT D816V mutations.
Bezuclastinib is showing not only meaningful response rates but also evidence of directly reducing the underlying disease burden.”
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