Sanofi abandons phase 3 trial of neurology drug riliprubart

Sanofi's neurology pipeline has had a hole blown in it after a phase 3 trial of riliprubart (SAR445088) in rare disease chronic inflammatory demyelinating polyneuropathy (CIDP) was stopped for futility.

The MOBILIZE trial will be stopped early and abandoned after an interim analysis by the study's independent data monitoring committee found the C1s-targeting antibody "is unlikely to provide sufficient efficacy."

CIDP is a rare autoimmune disease of the peripheral nervous system that causes fatigue, muscle weakness, and loss of feeling that can lead to serious disability and the need to use a wheelchair. There are approved treatments, including Argenx's FcRn inhibitor Vyvgart Hytrulo and Takeda's intravenous immune globulin (IVIg) product HyQvia, but options are limited.

MOBILIZE started in 2024 and recruited approximately 140 people with CIDP who were not responding to current treatment, which also includes corticosteroids, and was comparing intravenous and subcutaneous formulations of riliprubart to matched placebos over 24 weeks, followed by riliprubart for another 24 weeks, and with around two years of overall follow-up.

Sanofi has another shot on goal for riliprubart in CIDP in the phase 3 VITALIZE trial, which is comparing the drug to IVIg in adults with CIDP who were on maintenance treatment with IVIg at enrolment. That also started in 2024, with a readout due next year, but, like MOBILIZE, it will be assessed for interim signals by the data monitoring committee.

Sanofi's pipeline listing for the drug also shows a phase 2 study is ongoing for antibody-mediated rejection in transplant patients. It was previously tested for another autoimmune condition – cold agglutinin disease – but that does not seem to be an active programme anymore.

In 2022, Sanofi won FDA approval for an anti-C1s antibody, Enjaymo (sutimlimab), which became the first therapy in the US for CAD, but the company is not currently running clinical trials in any follow-up indications, suggesting its focus on C1s has shifted to riliprubart.

Both drugs are derived from Sanofi's investment in Biogen spinoff Bioverativ, a company it acquired for $11.6 billion in 2018.

C1s is an enzyme, part of the classical complement pathway, and is thought to dampen down various inflammatory processes orchestrated by the innate immune system. It is being targeted by various other drug developers, including Dianthius Therapeutics, which is running clinical trials of its claseprubart (DNTH103) candidate in autoimmune diseases like multifocal motor neuropathy (MMN) and generalised myasthenia gravis (gMG).