A Twice-Yearly Injection Cut Clotting Factor XI by 92%, With No Major Bleeding
- Ribo (Suzhou Ribo Life Science, 06938.HK, with Swedish subsidiary Ribocure) reported positive Phase 2a data for vortosiran, an siRNA targeting coagulation Factor XI, in patients with chronic coronary artery disease.
- In the randomised, double-blind, placebo-controlled study (NCT06717074), patients on the 400mg maintenance dose achieved a mean maximum 92% reduction in FXI activity, sustained for several months. That supports dosing every three to six months.
- No treatment-related serious adverse events, no major bleeding, and no clinically relevant non-major bleeding were observed. All patients were on standard-of-care aspirin.
- The company calls it the world’s first clinical proof-of-concept for siRNA-mediated FXI suppression, and has started the ORBIT-XI programme of Phase 2b trials to feed multiple Phase 3 indications.
Clinical read
Anticoagulation has always been a trade: prevent clots, accept bleeding. Factor XI is the genetically validated escape from that trade, people born with low FXI are protected from thrombosis without spontaneous bleeding, and this is the first clinical evidence an siRNA can reproduce it. But the competitive detail is the dosing interval, not the 92 percent. The small-molecule FXI inhibitors already in Phase 3 are dosed once or twice daily; a knockdown that holds for months supports dosing two to four times a year. In chronic prevention, where adherence quietly determines outcomes, twice-yearly dosing does not improve compliance, it removes compliance from the equation. Keep the stage honest: this is Phase 2a, and no bleeding events in a small sample is not proof of safety at scale. Note also who produced it, a Chinese company with a Swedish subsidiary, running the trial in Europe and presenting in Shanghai. The same Ribo sits in our H1 2026 top twenty through a $4.4 billion deal with Madrigal.