Sanofi halts MOBILIZE Phase 3 trial of riliprubart in refractory CIDP
Sanofi has announced the termination of its MOBILIZE Phase 3 clinical study of riliprubart in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) refractory to standard-of-care treatment. The decision followed an interim analysis by an independent data monitoring committee, which concluded the trial was unlikely to yield sufficient evidence of efficacy. No safety signals attributable to the drug were identified in the review.
Riliprubart (SAR445088, BIVV020) is a humanised IgG4 monoclonal antibody designed to selectively inhibit activated C1s, a serine protease in the classical complement pathway. The mechanism is intended to suppress the inflammatory cascade that drives myelin and axonal damage in CIDP — a rare autoimmune neuropathy affecting roughly one person in every 100,000 and characterised by progressive limb weakness and sensory loss. Sanofi has stated the drug's safety and efficacy have not yet been assessed by any regulatory authority.
The trial and what follows
The MOBILIZE study (NCT06290128) enrolled patients who had not responded adequately to conventional therapies including corticosteroids, plasma exchange, or intravenous immunoglobulin (IVIg). This refractory population represents an area of particular unmet need: Sanofi's own background data suggest around 30% of CIDP patients fail to respond to standard treatments, and of those who do respond, roughly 70% achieve only a partial response.
Sanofi said it will conduct a full analysis of the MOBILIZE dataset and work with site teams to ensure appropriate transition of care for enrolled patients. The company added that the discontinuation will not result in any material financial cost and that its full-year 2026 guidance remains unchanged.
A separate Phase 3 study of riliprubart — VITALIZE (NCT06290141) — in IVIg-treated CIDP patients is still active, though Sanofi said its continuation will be reviewed in light of the MOBILIZE outcome. The VITALIZE population differs from MOBILIZE in that patients are actively receiving IVIg; whether the complement-inhibition mechanism interacts differently in that context will be a key question for the internal data review.
Competitive and regulatory context
The MOBILIZE failure arrives in a competitive neurology landscape where Argenx's efgartigimod (marketed as Vyvgart) has gained regulatory approval in CIDP after demonstrating efficacy in an FcRn-blocking approach — a distinct but adjacent immunological mechanism. UCB's zilucoplan and other complement-targeting agents are active across various neuromuscular indications, meaning riliprubart's C1s-focused profile will face close scrutiny of whether the pathway holds relevance across the heterogeneous CIDP patient population.
Complement inhibition has shown clear utility in conditions such as myasthenia gravis and paroxysmal nocturnal haemoglobinuria, where the target biology is better defined. The CIDP setting is mechanistically more complex, and the MOBILIZE interim readout raises questions about whether complement activity is sufficiently central to disease pathology in standard-of-care-refractory patients to sustain a treatment effect. The VITALIZE dataset, if it proceeds to completion, will be an important test of the hypothesis in a different disease-stage context.
For Sanofi, the setback represents a narrowing of its neurology pipeline ambitions in the near term, though the company has signalled that the financial impact is limited. Investors will focus on whether VITALIZE proceeds and on any mechanistic learnings from the MOBILIZE data that could inform repositioning of riliprubart in other complement-mediated diseases.