Ribo reports positive Phase 2a trial data for vortosiran in coronary artery disease patients
Ribo Life Science announced positive results from a European Phase 2a study of vortosiran, showing effective inhibition of coagulation Factor XI in patients with coronary artery disease without significant bleeding. The study provides the first clinical proof-of-concept for siRNA-mediated FXI inhibition with repeated administration.
Suzhou Ribo Life Science announced on July 23, 2026, positive outcomes from a European Phase 2a clinical trial investigating vortosiran (RBD4059), an siRNA therapy targeting coagulation Factor XI (FXI). The study examined the drug candidate in patients with chronic coronary artery disease (CAD) who were receiving standard aspirin therapy.
The randomized, double-blind, placebo-controlled study found that vortosiran was generally well-tolerated. It demonstrated marked, dose-dependent, and durable suppression of FXI activity, particularly at higher doses. Patients in the high-dose group achieved an average maximal reduction of 92% in FXI activity, which persisted for several months post-administration, suggesting potential for administration every three to six months.
These findings represent the world's first clinical proof-of-concept for siRNA-mediated FXI inhibition in CAD patients with repeated dosing. Ribo suggests this supports vortosiran's potential as a differentiated, long-acting antithrombotic therapy. By targeting FXI, vortosiran aims to reduce thrombosis risk while preserving hemostasis, potentially addressing a significant unmet need in cardiovascular disease.
No treatment-related serious adverse events, major bleeding, or clinically relevant non-major bleeding were observed. Ribo states this supports a favorable safety profile compared to existing anticoagulants. The company has initiated the ORBIT-XI program, comprising several Phase 2b studies, to advance towards Phase 3 development for various indications.