Sirius Therapeutics Enters $900M Strategic Collaboration with CRISPR Therapeutics for Long-Acting siRNA Antithrombotic Therapy SRSD107

Today (May 20), Sirius Therapeutics and CRISPR Therapeutics announced a strategic partnership to jointly advance the co-development and commercialization of siRNA therapies. The press release stated that this collaboration combines the complementary capabilities of both parties in research, development, and industrialization to jointly develop and commercialize next-generation...Long-Acting Factor XI (FXI) Targeting Small Interfering RNA (siRNA) TherapySRSD107, for treatmentThrombosis and Thromboembolic Diseases。

According to the terms of the agreement, Sirius Therapeutics will receive payments from CRISPR Therapeutics.$95 millionCash and cash equivalents as the down payment, and are eligible to receiveOver $800 MillionThe upfront and milestone payments. Both parties will jointly develop SRSD107 through a 50-50 cost and profit sharing mechanism. In addition, the agreement grants CRISPR Therapeutics the exclusive right of first negotiation to license up to two additional siRNA programs in the future.

SRSD107 Injection is a double-stranded small interfering nucleic acid (siRNA) drug designed to selectively inhibit coagulation factor XI (FXI). The FXI target plays a crucial role in pathological thrombosis but has minimal impact on normal hemostatic function.By targeting FXI, SRSD107 is expected to reduce the occurrence of thrombotic events while significantly decreasing the risk of bleeding, demonstrating a therapeutic advantage distinct from factor Xa (FXa) inhibitors.SRSD107 has a wide range of potential indications, including atrial fibrillation, venous thromboembolism (VTE), cancer-related thrombosis, end-stage renal disease patients undergoing hemodialysis, and major orthopedic surgery populations whose treatment options are limited due to bleeding risks.

Preclinical trial data show that a single subcutaneous injection of SRSD107 can reduce peripheral blood FXI concentration by nearly 100%, with effects lasting up to half a year without any bleeding observed. SRSD107 combines potent and long-lasting effects with good safety, positioning it as a potential “first-in-class” and “best-in-class” next-generation safer anticoagulant drug.

Currently, SRSD107 has completed two Phase 1 clinical trials, showing good safety and tolerability with single dosing. Relevant research findings were presented at the 2025 American College of Cardiology (ACC) Annual Scientific Session and the 2024 American Society of Hematology (ASH) Annual Meeting.The Phase 2 clinical trial of SRSD107 is being initiated to evaluate its safety and efficacy in preventing venous thromboembolism (VTE) in patients undergoing knee replacement surgery.This study will provide clinical scientific evidence for confirming its anticoagulant clinical benefits and dose selection for subsequent pivotal trials.

Sirius Therapeutics and CRISPR Therapeutics will jointly advance the development of SRSD107. Under the agreement, CRISPR will be responsible for the commercialization of the product in the United States, while Sirius Therapeutics will handle the market in Greater China. Additionally, CRISPR Therapeutics has the right to nominate up to two siRNA targets and may choose to lead subsequent clinical development and commercialization. Sirius Therapeutics is eligible to receive milestone payments tied to project progress, conditional incentive payments, as well as tiered royalties based on sales revenue.

Dr. Qunsheng Ji, Executive Director and CEO of Sirius Therapeutics, stated that there is a significant unmet medical need in thrombotic diseases. The encouraging Phase 1 clinical data demonstrated by SRSD107 further validates its potential as a "best-in-class" therapy targeting coagulation factor XI (FXI). Sirius Therapeutics is committed to providing innovative treatment solutions for patients worldwide. This collaboration will fully leverage the strengths of both parties to jointly accelerate the global development and clinical translation of next-generation siRNA therapies.

Samarth Kulkarni, Ph.D., Chairman and Chief Executive Officer of CRISPR Therapeutics, stated: "We are thrilled to establish a partnership with Sirius Therapeutics and to further expand our pipeline in the cardiovascular disease field based on the exciting topline data recently announced for the CTX310 program (targeting ANGPTL3). Coagulation factor XI is an innovative and highly attractive target, demonstrating significant potential in treating thrombotic disorders that affect millions of patients worldwide. SRSD107 has the potential to become a 'best-in-class' therapy, offering major breakthroughs in clinical treatment through reduced dosing frequency and superior clinical benefits. The cutting-edge siRNA platform technology of Sirius Therapeutics is highly complementary to our existing R&D capabilities, further enriching our therapeutic technology platforms and empowering us to develop a broader range of transformative gene therapies."

Christian T. Ruff, MD, senior researcher of the TIMI Study Group, director of the Cardiology Division at Brigham and Women's Hospital, and associate professor at Harvard Medical School, stated: "Due to underlying conditions such as cardiovascular disease, malignancies, and hypercoagulable states, a significant number of patients are at risk of potentially fatal thromboembolic events. A considerable portion of these patients do not receive treatment or are undertreated due to concerns about bleeding risks or issues with medication adherence. SRSD107 has the potential to become a differentiated therapy with several advantages, including lower bleeding risk, less frequent dosing, improved patient compliance, no concerns regarding renal clearance or drug interactions, and better reversibility, further reducing the likelihood of bleeding risks. These advantages position it to stand out among existing therapies and other FXI-targeted approaches."