Sanofi halts Phase 3 trial of riliprubart in CIDP after interim analysis shows unlikely efficacy

Sanofi announced Wednesday that it is stopping the Phase 3 MOBILIZE study of its experimental anti‑inflammatory drug riliprubart in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). The decision follows an interim analysis by an independent data monitoring board that concluded the drug is unlikely to achieve sufficient efficacy, although no safety issues were identified.

The trial had enrolled patients who had not responded to standard‑of‑care therapies. CIDP is a rare neurological disorder that can cause progressive weakness and sensory loss, and Sanofi had hoped the drug could become a blockbuster treatment.

Sanofi’s share price dipped about 1% in early U.S. trading, while the news sent rival Dianthus Therapeutics, which is developing a similar C1‑targeted therapy for CIDP, down 16%, reflecting investor concerns that the negative readout may signal broader challenges for the therapeutic class.