Sirius Therapeutics Inks $95M Deal with CRISPR Therapeutics for Next-Gen Long-Acting FXI-Targeting siRNA SRSD107

On May 19, CRISPR Therapeutics (NASDAQ: CRSP), a biopharmaceutical company focused on creating transformative gene-based medicines for serious diseases, partnered with Sirius Therapeutics.peutics(Sirius Therapeutics)Is a clinical-stage company developing innovative small interfering RNA (siRNA) therapies for the global market.Phase Biotechnology Company Announces Strategic Partnership to Develop siRNA therapy and commercialize it. (Sirius Therapeutics Completes Nearly 50 Million USD B2 Round Financing, Developing New Small Nucleic Acid Drugs）

According to the terms of the agreement, CRISPR Therapeutics will provide toSirius Therapeutics Prepaid $25 Million in Cash and $70 Million in Equity Investment. The two companies will jointly develop SRSD107 under a 50/50 cost and profit-sharing structure. CRISPR Therapeutics will lead the commercialization in the United States.Sirius Therapeutics will be responsible for commercialization in Greater China.

In addition, CRISPR Therapeutics will have the right to nominate up to two siRNA targets for research and development. For each target, CRISPR Therapeutics will fund the research and retain the option to participate in leading clinical development and commercialization. Sirius Therapeutics will be eligible for milestone payments, as well as tiered royalties ranging from high single digits to low double digits.

Samarth Kulkarni, Ph.D., Chairman and Chief Executive Officer of CRISPR Therapeutics, stated:"We are thrilled to partner with Sirius to expand our cardiovascular drug portfolio, following the recent promising top-line data we shared for CTX310 targeting ANGPTL3. Coagulation Factor XI represents an innovative and highly compelling target for treating thrombotic disorders that affect millions of people worldwide. SRSD107 targets Factor XI and has the potential to become a first-in-class treatment, offering rare dosing convenience and improved patient outcomes. Sirius' siRNA platform complements our existing capabilities and expands our therapeutic toolkit, enabling us to develop a broader range of transformative gene medicines."

SRSD107 is a next-generation long-acting siRNA designed to selectively inhibit Factor XI (FXI).FXI is a key driver of pathological thrombosis with minimal impact on normal hemostasis. By targeting FXI, SRSD107 aims to reduce thrombotic events while minimizing bleeding risk—a different approach compared to Factor Xa inhibitors. Additionally, SRSD107 may offer reversible potential not observed with other anti-Factor XI drugs. The addressable population includes patients with atrial fibrillation, venous thromboembolism (VTE), cancer-associated thrombosis, chronic coronary artery disease (CAD), chronic peripheral vascular disease (PVD), end-stage renal disease requiring hemodialysis, and those undergoing major orthopedic surgery, where bleeding risks limit existing treatment options.

The clinical program for SRSD107 includes two promising Phase 1 clinical trials, in which a single dose of SRSD107 was found to be safe and well-tolerated. Additionally, SRSD107 demonstrated potent pharmacodynamic effects, including reductions of over 93% in FXI levels and FXI activity (FXIa), as well as more than a twofold increase in activated partial thromboplastin time (aPTT) relative to baseline. These effects were sustained, with responses lasting up to six months post-dosing. SRSD107 has the potential to become the best-in-class FXI inhibitor, demonstrating profound FXI reduction through semi-annual subcutaneous injections. The results of the Phase 1 clinical trials were presented at the American College of Cardiology’s 2025 Annual Scientific Session and the American Society of Hematology’s 2024 Annual Meeting.

SRSD107 Phase 1 Clinical Results: Sustained, Dose-Dependent Pharmacodynamic Response to Treatment

Phase 2 clinical trial of SRSD107 is being initiated to evaluate its safety and efficacy in preventing VTE in patients undergoing total knee arthroplasty. The trial aims to confirm the anticoagulant benefits of SRSD107 and provide dose-selection information for future pivotal trials.