By Fineline Cube 
China-based Sirius Therapeutics announced on July 23, 2025, that its next-generation siRNA therapy, SRSD107, has received approval from the European Medicines Agency (EMA) to proceed with Phase II clinical trials. SRSD107 is a novel siRNA drug targeting Factor XI (FXI) for the prevention and treatment of thromboembolic diseases.
Mechanism and Advantages
Factor XI plays a crucial role in pathological thrombosis with minimal impact on normal hemostatic function. SRSD107 selectively inhibits FXI to reduce thrombosis risk while minimizing bleeding adverse events. This approach offers a therapeutic advantage over FXa inhibitors. Potential applications include atrial fibrillation, venous thromboembolism (VTE), cancer-associated thrombosis, end-stage renal disease dialysis patients, and individuals undergoing major orthopedic surgery where bleeding risk limits existing anticoagulant treatments.
Preclinical and Clinical Progress
Preclinical studies demonstrated that a single subcutaneous injection of SRSD107 can reduce FXI levels to near undetectable levels, with efficacy lasting six months and a favorable safety profile. The drug has completed two Phase I clinical studies in China and Australia, with data presented at the 2024 ASH Annual Meeting and the 2025 ACC Annual Meeting.
Collaboration and Global Strategy
SRSD107 is co-developed by Sirius Therapeutics and CRISPR Therapeutics. Under their agreement, the parties share development costs and profits, with each responsible for commercialization in China and the U.S. This EU clinical trial approval sets the stage for pivotal studies and global market expansion.-Fineline Info & Tech