Sanofi Halts Phase 3 CIDP Study of Riliprubart After Futility Analysis

Sanofi has stopped its Phase 3 MOBILIZE trial evaluating riliprubart in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) who were refractory to standard-of-care therapies after an independent data monitoring committee concluded the study was unlikely to demonstrate sufficient efficacy.¹

The company stated that no safety signals related to riliprubart were identified during the interim analysis. Sanofi will work with investigators and study sites to wind down the trial and transition enrolled patients to appropriate care.¹

MOBILIZE (NCT06290128) was designed to evaluate the efficacy and safety of riliprubart compared with placebo in adults with CIDP whose disease had failed to respond adequately to available treatments. The phase 3 study was expected to enroll approximately 140 participants across multiple international sites.¹˒²

Why is the MOBILIZE study significant for CIDP drug development?

CIDP is a rare autoimmune neurological disorder characterized by progressive weakness and sensory impairment resulting from immune-mediated damage to peripheral nerve myelin. Although treatments such as intravenous immunoglobulin (IVIg), corticosteroids, and plasma exchange can be effective, a substantial proportion of patients experience incomplete responses or treatment failure.¹˒³

Sanofi had positioned riliprubart as a potential first-in-class therapy targeting activated C1s within the classical complement pathway. By inhibiting C1s, the monoclonal antibody was designed to reduce inflammatory processes associated with demyelination and axonal injury in CIDP.¹

The setback is notable because earlier phase 2 findings had suggested encouraging efficacy and safety across multiple patient populations, including individuals who had failed or responded inadequately to standard therapies. Investigators also reported improvements in disease-related biomarkers, fatigue, and quality-of-life measures.⁴

What does the decision mean for the broader riliprubart program?

Sanofi indicated that it will conduct a comprehensive analysis of the MOBILIZE data to better understand the outcome and inform future research.¹

The company is also evaluating the continuation of the VITALIZE Phase 3 trial (NCT06290141), which is investigating riliprubart in patients with CIDP receiving maintenance IVIg therapy.¹˒⁵

Why are new treatment options still needed for CIDP?

The outcome also highlights the ongoing challenges of developing new therapies for CIDP, a heterogeneous disease with variable clinical presentation and treatment response. While IVIg, corticosteroids, and plasma exchange remain standard treatment options, many patients continue to experience persistent disability, relapses, or incomplete symptom control.³

Researchers have increasingly explored targeted immunological approaches aimed at addressing underlying disease mechanisms while reducing the treatment burden associated with chronic therapy. Complement inhibition has emerged as one such strategy because evidence suggests activation of the complement system may contribute to nerve damage and disease progression in some patients with CIDP.³˒⁴ The findings from MOBILIZE may therefore provide important insights for future studies evaluating complement-targeted therapies in peripheral neuropathies.³˒⁴

While the discontinuation of MOBILIZE represents a significant setback for riliprubart in treatment-refractory CIDP, Sanofi emphasized that no new safety concerns emerged during the study and that the decision was based solely on a lack of anticipated efficacy.¹

References

1. Sanofi provides update on MOBILIZE phase 3 study of riliprubart in chronic inflammatory demyelinating polyneuropathy. (2026 Jun 10). Sanofi. https://www.sanofi.com/en/media-room/press-releases/2026/2026-06-10-05-00-00-3309444
2. A Study to Test the Effects and Safety of Riliprubart in People With Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) for Which the Usual Treatments do Not Work. Sanofi. https://www.sanofi.com/en/clinical-trials/nct06290128
3. European Academy of Neurology/Peripheral Nerve Society Guideline on Chronic Inflammatory Demyelinating Polyradiculoneuropathy. 2021. chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://medicalaffairs.cslbehring.com/-/media/medical-affairs/documents/hizentra_cidp-guideline_infographic_csl-medical-affairs.pdf
4. Riliprubart one-year results from phase 2 study underpin the potential as a first-in-class treatment in chronic inflammatory demyelinating polyneuropathy. (2024 Jun 25). Sanofi. https://www.sanofi.com/en/media-room/press-releases/2024/2024-06-25-20-30-00-2904145
5. A Study to Test the Efficacy and Safety of Riliprubart Against Intravenous Immunoglobulin (IVIg) in People With Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). ClinicalTrials.gov. https://clinicaltrials.gov/study/NCT06290141