Sirius Therapeutics Announces EMA Approval for Phase II Clinical Trial of Next-Generation Long-Acting FXI-Targeting siRNA Anticoagulant SRSD107
Sirius Therapeutics
Oligonucleotide Drug Developer
On July 23, 2025, Sirius Therapeutics announced that itsNext-Generation siRNA Therapy SRSD107 Approved by the European Medicines Agency (EMA) for Phase II Clinical TrialsSRSD107 is a next-generation siRNA therapy that specifically targets anticoagulant Factor XI, aimed at the prevention and treatment of thromboembolic diseases. This approval marks a significant milestone in the regulatory pathway and lays the groundwork for conducting clinical studies across multiple European countries. The development of SRSD107 is part of a strategic collaboration between Sirius Therapeutics and CRISPR Therapeutics, both committed to advancing innovative therapies in the field of cardiovascular and coagulation-related diseases.Hankang Capital led the Series B financing of Sirius Therapeutics in 2023.
SRSD107 is a next-generation long-acting siRNA therapy 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 bleeding risks, demonstrating therapeutic advantages distinct from factor Xa (FXa) inhibitors. The potential indications for SRSD107 are broad and include atrial fibrillation, venous thromboembolism (VTE), cancer-associated thrombosis, end-stage renal disease patients undergoing hemodialysis, and major orthopedic surgery populations whose treatment options are limited by bleeding risks.
This Phase II clinical trial is based on two Phase I clinical studies of SRSD107 completed in China and Australia. In these studies, a single dose of SRSD107 demonstrated good safety and tolerability. Additionally, SRSD107 showed significant and sustained pharmacological effects in reducing FXI antigen levels and prolonging activated partial thromboplastin time (aPTT). The relevant research findings were presented at the 2024 American Society of Hematology (ASH) Annual Meeting and the 2025 American College of Cardiology (ACC) Annual Meeting.
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Sirius Therapeutics Chief Medical Officer Dr. Peichuan Yu stated:
"The Phase II clinical trial of SRSD107-201 aims to evaluate the safety and efficacy of preventing venous thromboembolism (VTE) in patients undergoing total knee replacement surgery. This study will validate the anticoagulant potential of SRSD107 and provide a basis for dose optimization in future pivotal clinical trials. We look forward to collaborating closely with clinical trial institutions across Europe to advance this important research."
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Dr. Qunsheng Ji, CEO and Executive Director of Sirius Therapeutics, stated:
"Sirius Therapeutics team has always been committed to addressing significant unmet medical needs in the cardiovascular and cerebrovascular fields. This progress not only represents an important step in the company’s R&D pipeline strategy but also further demonstrates our firm commitment to advancing the development of innovative therapies worldwide."
About Vascular Embolism
Thrombosis is a blood clot that restricts blood flow within blood vessels and can occur in either arterial or venous circulation. It serves as the common pathological basis for most myocardial infarctions, ischemic strokes, and venous thromboembolism (VTE). Globally, one in four people die from diseases caused by thromboembolism.
About SRSD107 Injection
SRSD107 Injection is a double-stranded small interfering nucleic acid (siRNA) drug independently developed by Sirius Therapeutics with proprietary intellectual property rights. By specifically targeting the liver to inhibit human coagulation factor XI (FXI) messenger ribonucleic acid (mRNA), it suppresses FXI protein expression, blocking the activation of the intrinsic coagulation pathway, thereby exerting an anticoagulant effect. Preclinical trial data show that a single subcutaneous injection of SRSD107 can reduce peripheral blood FXI concentration by nearly 100%, lasting up to half a year without causing bleeding. With its potent, long-lasting efficacy and favorable safety profile, SRSD107 has the potential to become a First-in-Class and Best-in-Class next-generation safer anticoagulant drug.
About the Cooperation between CRISPR Therapeutics and Sirius Therapeutics
CRISPR Therapeutics and Sirius Therapeutics entered into a strategic collaboration in May 2025 to co-develop and commercialize novel small interfering RNA (siRNA) therapies for the treatment of thrombotic disorders and other severe diseases. The first collaborative project, SRSD107, is a long-acting siRNA drug targeting coagulation factor XI (FXI), with the potential to achieve best-in-class efficacy and safety.
According to the agreement, both parties will jointly develop SRSD107 and share costs and profits proportionally. CRISPR Therapeutics will be responsible for the commercialization of the product in the United States, while Sirius Therapeutics will handle commercialization and promotion in Greater China. Additionally, CRISPR Therapeutics has the option to license up to two additional siRNA projects.
This collaboration marks CRISPR Therapeutics' expansion into the RNA drug field, further enriching its therapeutic product portfolio and complementing its ongoing efforts in the gene-editing domain, thereby expanding its influence in severe and chronic disease areas. For Sirius Therapeutics, this partnership represents a significant milestone in its global deployment of innovative RNA therapies, fully leveraging its profound technical expertise in siRNA design and delivery.
About Sirius Therapeutics
Sirius Therapeutics is a clinical-stage biotechnology company dedicated to advancing human health and well-being. As a leader in the development of groundbreaking siRNA therapies for chronic disease prevention and treatment, its current pipeline includes SRSD107 for thromboembolic disorders, SRSD216 for elevated lipoprotein(a), and SRSD101 for dyslipidemia, all of which have entered the clinical development phase.
Founded in 2021, Sirius Therapeutics was incubated by an internationally renowned management team and globally prominent healthcare investment institutions. The company adopts an international strategic positioning, leveraging the talent and resource advantages in the field of small nucleic acid therapies from both the United States and China. It has established a layout with the U.S. as the source of innovative discovery center and China as the global translational medicine center. Utilizing its core technology platform for small nucleic acid drug research and development, the company has developed multiple product pipelines with either first-in-class or best-in-class potential, offering differentiated global competitive advantages. To date, the company has raised nearly 150 million U.S. dollars in cumulative financing.
About Hancang Capital
Hankang Capital is a venture capital fund focused on the pharmaceuticals and healthcare industry. With the mission of "empowering pharmaceutical innovation and safeguarding human health," the fund collaborates with top scientists and entrepreneurs to develop breakthrough drugs for the treatment of major diseases. Hankang Capital, rooted in China while maintaining a global perspective, has invested in multiple enterprises that have since grown into industry leaders, such as Akeso Inc. (09926.HK), InnoCare Pharma (09969.HK, 688428.SH), Connaught Bio (02162.HK), Abbisko Therapeutics (02256.HK), DualityBio (09606.HK), Chipscreen Biosciences (688321.SH), and OPM Biosciences (688293.SH).