Ribo Discloses Positive Data from Vortosiran Phase IIa Trial - World’s First Clinical Data on siRNA-Mediated FXI Inhibition Following Multiple Dosing in Patients with Coronary Artery Disease
July 22, 2026 · Shanghai, China and Molndal, Sweden
Suzhou Ribo Life Science Co., Ltd. (06938.HK) and its subsidiary Ribocure Pharmaceuticals AB (collectively referred to as “Ribo”) today announce at China Pharmaceutical Innovation Conference (CPIC) in Shanghai, the positive results from a Phase 2a study in Europe evaluating vortosiran (RBD4059), Ribo’s siRNA therapy targeting coagulation Factor XI (FXI), in patients with chronic coronary artery disease (CAD).
The randomized, double-blind, placebo-controlled study demonstrated that vortosiran in patients receiving standard of care, aspirin, treatment was generally well tolerated and achieved profound, dose-dependent, and long-lasting suppression of FXI activity (NCT06717074, clinicaltrials.gov). Patients with chronic CAD with previous myocardial infarction on aspirin were investigated in the current trial. Patients completing the high dose group vortosiran dosing regimen, at a maintenance dose of 400mg, achieved a mean maximum reduction in FXI activity of 92%, which sustained for several months following dosing. This data supports every three to six months dosing in various indications.
The degree of FXI inhibition is markedly greater than that estimated for e.g. the ongoing small molecule programs, typically dosed once or twice daily, currently in Phase 3 clinical development.
Importantly, no treatment-related serious adverse events, major bleeding events, or clinically relevant non-major bleeding events were observed.
These findings provide the world’s first clinical proof-of-concept for siRNA-mediated FXI suppression in patients with coronary artery disease, supporting the potential of vortosiran as a differentiated, long-acting antithrombotic therapy. By targeting FXI, vortosiran aims to reduce thrombotic risk while preserving hemostasis, potentially addressing a major unmet need in cardiovascular disease.
"Preventing blood clots without increasing bleeding risk has long been a holy grail of cardiovascular medicine. These Phase 2a data, generated in the target patient population on top of standard of care, reinforce our belief that vortosiran is a safe and highly differentiated FXI-inhibition approach for thromboembolic diseases. Building on these findings, we have initiated the ORBIT-XI program (Optimizing RNA-Based Inhibition of Thrombosis), including several Phase 2b trials designed to support rapid progression into Phase 3 development across multiple indications." says Dr Li-Ming Gan, co-CEO and Global President of R&D, Ribo
About vortosiran, RBD4059
Vortosiran is a GalNAc-conjugated siRNA candidate based on the proprietary RiboGalSTAR™ liver-targeting platform. By selectively suppressing Factor XI (FXI) synthesis, vortosiran inhibits the intrinsic coagulation pathway and delivers potent antithrombotic activity. Compelling human genetic evidence indicates that individuals with naturally reduced FXI levels are protected against thrombotic disease without a corresponding increase in spontaneous bleeding risk. Consequently, FXI inhibition has emerged as a highly attractive therapeutic approach with the potential to combine effective thrombosis prevention with an improved safety profile relative to existing anticoagulant therapies.