Youcare Pharmaceutical Group (SSE: 688658) has secured US FDA clearance to take GalNAc-siRNA YKYY033 into US trials, adding a long-acting RNAi approach to the growing race to inhibit Factor XI without the bleeding liability of conventional anticoagulants. The Study May Proceed letter covers prevention and treatment of arterial and venous thrombosis and marks YKYY033's first clearance for clinical development outside China.
YKYY033 is a chemically synthesized double-stranded siRNA conjugated to GalNAc for hepatocyte delivery. By degrading FXI mRNA, the therapy is designed to suppress hepatic production of Factor XI and provide prolonged anticoagulant activity. Youcare reported that YKYY033 reduced FXI mRNA and protein across animal models, prolonged APTT without affecting PT, and inhibited arterial and venous thrombosis without increasing bleeding in humanized mouse models.
YKYY033 already has clinical clearance in China, where the NMPA authorized development across indications including orthopedic VTE prophylaxis, DVT, atrial fibrillation, coronary and peripheral artery disease, end-stage renal disease and cancer-associated VTE in June and July 2026. The US FDA clearance marks the program's first expansion into overseas clinical development.
YKYY033 enters a crowded and increasingly competitive FXI/FXIa inhibitor pipeline. YKYY033's closest mechanistic comparator is Ribocure's vortosiran, another GalNAc-conjugated siRNA targeting hepatic FXI production that has already completed Phase I testing in healthy volunteers. The broader FXI field includes Novartis' antibody abelacimab, Bristol Myers Squibb/Janssen's oral FXIa inhibitor milvexian, and Ionis's antisense therapy fesomersen, illustrating the range of modalities competing to validate FXI as a safer anticoagulation target.