French healthcare company Sanofi S.A. (Euronext Paris:SAN) (Nasdaq:SNY) announced on Monday that the Ministry of Health, Labour and Welfare in Japan has granted orphan drug designation to riliprubart (SAR445088), an investigational monoclonal antibody targeting activated C1s in the classical complement pathway, for the treatment of chronic inflammatory demyelinating polyneuropathy (CIDP).

This designation reflects riliprubart's potential to address significant unmet medical needs for the estimated 4,000 individuals in Japan living with CIDP, a rare autoimmune neurological disorder marked by progressive weakness and sensory impairment.

The decision follows similar orphan drug designations in the United States and Europe, reinforcing global regulatory interest in the candidate's clinical potential.

Despite available treatments, approximately 30% of patients with CIDP do not respond to current therapies, and many continue to experience residual symptoms impacting quality of life.

Riliprubart is currently being evaluated in two phase 3 trials: MOBILIZE, in patients refractory to standard care, and VITALIZE, in those treated with intravenous immunoglobulin. Phase 2 data presented in May 2025 at the Peripheral Nerve Society meeting demonstrated sustained efficacy and safety over 76 weeks.

Riliprubart remains an investigational therapy and has not been approved by any regulatory authority. Its mechanism of selectively inhibiting C1s may offer a novel approach to halting inflammation-driven nerve damage in CIDP.