SHANGHAI, China and MÖLNDAL, Sweden, July 22, 2026
Suzhou Ribo Life Science Co., Ltd. and its subsidiary Ribocure Pharmaceuticals AB (collectively Ribo) have announced positive Phase 2a clinical trial results for vortosiran (RBD4059), an investigational small interfering RNA (siRNA) therapy targeting coagulation Factor XI (FXI) in patients with chronic coronary artery disease (CAD). Presented at the China Pharmaceutical Innovation Conference (CPIC) in Shanghai, the findings represent the world’s first clinical data demonstrating siRNA-mediated FXI inhibition following multiple dosing in patients with coronary artery disease. The randomized, double-blind, placebo-controlled study showed that vortosiran was generally well tolerated, produced dose-dependent and sustained suppression of FXI activity, and achieved a mean maximum reduction of 92% in FXI activity in patients receiving the highest maintenance dose while maintaining a favorable safety profile. The results strengthen the potential of vortosiran as a long-acting antithrombotic therapy capable of reducing thrombotic risk while minimizing bleeding complications.
Phase 2a Trial Demonstrates Durable FXI Suppression
The European Phase 2a clinical trial evaluated vortosiran in patients with chronic coronary artery disease who had experienced a previous myocardial infarction and were receiving standard aspirin therapy. The study demonstrated that patients treated with the highest maintenance dose of 400 mg vortosiran achieved a mean maximum 92% reduction in Factor XI activity, with suppression sustained for several months after dosing. These findings suggest that the investigational therapy could potentially support once every three to six months dosing, offering a significant advantage over several investigational small-molecule FXI inhibitors currently in Phase 3 development, which generally require daily administration. The durable pharmacodynamic response highlights the promise of RNA interference (RNAi) technology in developing long-acting cardiovascular medicines that improve patient convenience while maintaining therapeutic efficacy.
Safety Profile Supports Long-Acting Antithrombotic Strategy
Equally significant were the favorable safety outcomes observed during the trial. No treatment-related serious adverse events, major bleeding events, or clinically relevant non-major bleeding events were reported among study participants. Because Factor XI primarily contributes to pathological clot formation while playing a more limited role in normal hemostasis, selective FXI suppression has emerged as an attractive strategy for preventing thrombosis without substantially increasing bleeding risk. According to Ribo, the encouraging safety profile provides the first clinical proof-of-concept that siRNA-mediated FXI inhibition may offer an improved therapeutic balance between efficacy and safety compared with conventional anticoagulant therapies. This approach addresses one of the most important unmet needs in cardiovascular medicine by potentially reducing thromboembolic events while preserving normal blood clotting function.
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ORBIT-XI Program Advances RNAi Cardiovascular Innovation
Building on the successful Phase 2a findings, Ribo has initiated the ORBIT-XI (Optimizing RNA-Based Inhibition of Thrombosis) clinical development program, which includes multiple Phase 2b trials designed to accelerate the progression of vortosiran toward Phase 3 clinical development across several thromboembolic disease indications. The investigational therapy is based on Ribo’s proprietary RiboGalSTAR™ liver-targeting platform, which utilizes GalNAc-conjugated siRNA technology to selectively suppress hepatic production of Factor XI. Supported by extensive human genetic evidence showing that naturally reduced FXI levels are associated with protection against thrombosis without increased spontaneous bleeding, the program reflects growing interest in RNA interference therapeutics as a new generation of precision cardiovascular medicines. The positive Phase 2a data position vortosiran as one of the most advanced long-acting siRNA anticoagulant candidates, strengthening Ribo’s expanding cardiovascular pipeline and highlighting continued innovation in oligonucleotide drug development.
Source: Ribo Press release
