Sanofi scraps Phase 3 trial after CIDP drug fails to deliver results

Sanofi has halted its Phase 3 MOBILIZE study of riliprubart after the drug showed no effectiveness in treating chronic inflammatory demyelinating polyneuropathy (CIDP). The decision marks a setback for a compound designed to block the classical pathway of the human complement system. The study involved 140 patients across 134 global sites, all resistant to standard treatments. Riliprubart was developed as a C1s inhibitor, targeting a specific part of the immune system. Sanofi’s interim analysis revealed the drug failed to meet its goals in the MOBILIZE trial. As a result, the company is now reviewing all other ongoing studies of the treatment.

The setback raises questions about Sanofi’s $11.6bn acquisition of Bioverativ in 2018. While the deal brought successes like Altuviiio, approved for haemophilia A in 2023, its first-quarter sales in 2026 reached around €325 million. Another C1s inhibitor from the acquisition, Enjaymo, gained approval in 2022 before being sold to Recordati for $825 million. Sanofi’s decision to abandon the MOBILIZE study highlights the challenges in drug development. The company continues to assess riliprubart’s future while relying on other Bioverativ acquisitions for growth. The outcome underscores the mixed results from the high-cost purchase.