Sanofi announced on June 10 that it is discontinuing a late-stage study of its investigational complement inhibitor riliprubart in chronic inflammatory demyelinating polyneuropathy. The decision follows an interim data analysis by an independent board, which found the trial was unlikely to demonstrate sufficient efficacy. The MOBILIZE study, launched in 2024, compared riliprubart against placebo in approximately 140 patients with chronic inflammatory demyelinating polyneuropathy.
William Blair told investors on Wednesday morning, “The news is obviously disappointing for the complement inhibitor class in CIDP,” especially after riliprubart’s “impressive” open-label Phase 2 data. In a June 2024 readout, 87% of patients who switched to riliprubart from standard care improved or remained stable after 24 weeks. At least 72% of these patients were relapse-free after about one year on riliprubart. Additionally, 89% of patients unresponsive to standard care remained stable or improved while taking riliprubart.
Alongside MOBILIZE, Sanofi is conducting other studies involving riliprubart, including the Phase 3 VITALIZE trial in chronic inflammatory demyelinating polyneuropathy with intravenous immunoglobulin as a comparator arm. The company said on Wednesday that whether VITALIZE and other programs will continue, "will be evaluated accordingly.”
Sanofi does not expect any significant financial cost from winding down the MOBILIZE trial, according to its press announcement.
William Blair analysts said the discontinuation could lead to volatility for other companies developing complement inhibitors. Among these is argenx, which is developing empasiprubart for chronic inflammatory demyelinating polyneuropathy and other diseases driven by complement activity. Argenx currently has two Phase 3 trials—EMVIGORATE and EMNERGIZE—with expected results in the second half of 2027. Both are parallel-group studies similar in design to Sanofi’s program and face challenges such as patient heterogeneity and misdiagnosis.
“But argenx has experience in running successful studies and confirming CIDP diagnoses,” William Blair said. For example, argenx owns Vyvgart Hytrulo, which received FDA approval for CIDP treatment in June 2024.
