The discontinuation of Sanofi’s Phase 3 study for its complement inhibitor drug in chronic inflammatory demyelinating polyneuropathy delivers an ‘obviously disappointing’ blow to the broader drug class, according to William Blair.
Sanofi is pulling the plug on a late-stage study of its investigational complement inhibitor riliprubart in chronic inflammatory demyelinating polyneuropathy—a move that analysts say could have broader ramifications across the drug class.
The decision to discontinue the trial, dubbed MOBILIZE, comes after an interim data analysis by an independent data board found that the study would be “unlikely to provide sufficient efficacy.” Launched in 2024, MOBILIZE was comparing riliprubart against placebo in around 140 patients with chronic inflammatory demyelinating polyneuropathy (CIDP).
“The news is obviously disappointing for the complement inhibitor class in CIDP,” William Blair told investors on Wednesday morning, particularly after riliprubart’s “impressive” open-label Phase 2 data.
In the June 2024 readout, 87% of patients who switched to riliprubart from standard of care improved or remained stable after 24 weeks. At least 72% of these patients were relapse-free after about one year on riliprubart. In addition, 89% of patients who were unresponsive to standard of care remained stable or improved on riliprubart.
In addition to MOBILIZE, Sanofi is running other studies of riliprubart, including the Phase 3 VITALIZE trial in CIDP, which includes intravenous immunoglobulin as a comparator arm. Whether VITALIZE and other riliprubart programs will move forward “will be evaluated accordingly,” the company said on Wednesday.
The pharma doesn’t expect to sustain any “significant financial cost” as a result of MOBILIZE’s wind-down, according to the press announcement.
The trial’s discontinuation, however, could lead to “volatility” for other companies developing complement inhibitors, William Blair analysts continued. Among these is argenx, which is developing the investigational antibody empasiprubart for CIDP and other complement-driven diseases.
Argenx is currently running the Phase 3 EMVIGORATE and EMNERGIZE studies for the asset, with expected readouts in the second half of 2027. Both trials “are similar in design” to Sanofi’s riliprubart program—parallel-group studies that come with the issues of “patient heterogeneity and misdiagnosis,” according to William Blair
“But argenx has experience in running successful studies and confirming CIDP diagnoses,” William Blair said. For example, the biotech owns the FDA-approved Vyvgart Hytrulo, which won its CIDP go-ahead in June 2024. This experience, the analysts noted, “should not be overlooked.”
