CTX611 (SRSD107)
Overview
A long-acting, double-stranded siRNA that targets Factor XI (FXI) messenger RNA to inhibit FXI protein expression, aiming to provide anticoagulant and antithrombotic protection with less bleeding risk than existing anticoagulants, potentially dosed as infrequently as semi-annually. Co-developed with Sirius Therapeutics (50/50 cost and profit share; CRISPR leads U.S. commercialization, Sirius leads Greater China) across a range of thromboembolic indications including atrial fibrillation, venous thromboembolism, and stroke prevention.
Phase 2 trial for prevention of venous thromboembolism in total knee arthroplasty patients dosed its first patient in September 2025. Phase 1 data showed peak FXI activity reductions >93% and aPTT increases >2x, sustained up to 6 months. Topline Phase 2 data expected in H2 2026; CRISPR will lead global Phase 3 development outside Greater China.