Sirius Therapeutics Receives European Medicines Agency (EMA) Authorization to Initiate a Phase 2 Clinical Trial of SRSD107 for Thromboembolic Disorders
July 23rd, 2025
SAN DIEGO and SHANGHAI, July 23rd, 2025 – Sirius Therapeutics, a clinical stage biotechnology company developing innovative small interfering RNA (siRNA) therapies for global markets, today announced it has received European Medicines Agency (EMA) authorization to initiate a Phase 2 clinical trial of SRSD107, a next-generation, long-acting Factor XI (FXI) siRNA for the treatment of thromboembolic disorders. The authorization marks a significant regulatory milestone and enables the trial to proceed across multiple European countries. SRSD107 is being co-developed by Sirius Therapeutics and CRISPR Therapeutics as part of a strategic collaboration to advance innovative treatments for cardiovascular and clotting-related diseases.
SRSD107 is a next generation, long-acting siRNA designed to selectively inhibit Factor XI (FXI), a key driver of pathological thrombosis with minimal impact on normal hemostasis. By targeting FXI, SRSD107 aims to reduce thrombotic events while minimizing the risk of bleeding, representing a differentiated approach compared to Factor Xa inhibitors. In addition, SRSD107 may offer the potential for reversibility not observed with other anti-Factor XI modalities. The addressable population includes patients with atrial fibrillation, cancer-associated thrombosis, chronic Coronary Artery Disease (CAD), chronic Peripheral Vascular Disease (PVD), end-stage renal disease requiring hemodialysis, and patients undergoing major orthopedic surgery, and other venous thromboembolism (VTE) where bleeding risk limits existing therapies.
Sirius’ Chief Medical Officer, Dr. Patrick Yue, stated, "Our Phase 2 clinical trial of SRSD107 is designed to evaluate its safety profile and efficacy in preventing venous thromboembolism in patients undergoing total knee arthroplasty. This study aims to confirm the anticoagulant potential of SRSD107 and inform optimal dosing strategies for future pivotal trials. We look forward to collaborating with clinical investigators across Europe in advancing this important initiative."
Dr. Qunsheng Ji, Sirius’ Chief Executive Officer, emphasized that "Sirius remains focused on addressing significant unmet needs in cardiovascular and cerebrovascular care. This achievement marks an important step forward in our pipeline strategy and reinforces our commitment to developing groundbreaking therapies for global use."
The Phase 2 trial follows two promising Phase 1 clinical trials with patients in China and another with patients in Australia, where single doses of SRSD107 were found to be safe and well tolerated. In addition, SRD107 demonstrated robust and prolonged reductions in FXI antigen and increases in activated partial thromboplastin time. Results from the trials were presented at the 2024 Annual Meeting of the American Society of Hematology (ASH) 1 and the 2025 Annual Scientific Sessions of the American College of Cardiology (ACC) 2.
About Thromboembolic Disorders
Thrombosis, or blood clot formation, is the common underlying mechanism of most cases of myocardial infarction, ischemic stroke, and venous thromboembolism. Based on epidemiological data from The Lancet of regional and global mortality rates, thromboembolic disorders are estimated to cause as many as 1 in 4 deaths worldwide3.
About SRSD107
SRSD107 is a novel double-stranded small interfering ribonucleic acid (siRNA). Developed by Sirius Therapeutics, SRSD107 specifically targets the human coagulation factor XI (FXI) mRNA and inhibits FXI protein expression, thereby blocking the intrinsic coagulation pathway and promoting anticoagulant/anti-thrombotic effects. SRSD107 has been engineered for the potential to enable once or twice yearly dosing.
About the CRISPR Therapeutics and Sirius Therapeutics Collaboration
CRISPR Therapeutics and Sirius Therapeutics entered into a strategic collaboration in 2025 to develop and commercialize novel small interfering RNA (siRNA) therapies for thromboembolic disorders and other serious diseases. The lead program, SRSD107, is a long-acting siRNA targeting Factor XI (FXI) with the potential to offer best-in-class efficacy and safety. Under the agreement, the companies will co-develop SRSD107 and share costs and profits equally. CRISPR Therapeutics will lead commercialization in the U.S., while Sirius will lead in Greater China. The collaboration also provides CRISPR Therapeutics with the option to license up to two additional siRNA programs. This partnership expands CRISPR Therapeutics’ therapeutic portfolio into RNA-based medicines, complementing its ongoing efforts in gene editing and broadening its impact across serious and chronic diseases. For Sirius, the collaboration marks a major milestone in its mission to deliver innovative RNA-based therapies globally, leveraging deep expertise in siRNA design and delivery.
About Sirius Therapeutics
Sirius is a clinical-stage biotech company developing innovative siRNA therapies for global markets. We are dedicated to discovering and developing new treatment options for cardiovascular and cerebrovascular disease and translating siRNA technology into transformative medicine for chronic disease patients. Sirius’s most advanced products are SRSD107 for the treatment of thromboembolic disorders, SRSD216 for the treatment of hyperlipoproteinemia, and SRSD101 for the treatment of dyslipidemia.
Founded in 2021 by a world-class leadership team and investors, Sirius has established an innovation center in the United States and a translational medicine center in China. Sirius has raised nearly US$150 million in funding to date from OrbiMed, Creacion Ventures, Hankang Capital, Delos Capital, and BioTrack Capital.
References
1. Blood (2024) 144 (Supplement 1): 4009.
2. J Am Col Card (2025) 85:12 (Supplement): 2379.
3. Lozano R, Naghavi M, Foreman K, et al. Global and regional mortality from 235 causes of death for 20 age groups in 1990 and 2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet. 2012;380, 2095-1128.
