Sanofi has discontinued one of its phase 3 clinical trials evaluating riliprubart for chronic inflammatory demyelinating polyneuropathy (CIDP) after an interim analysis indicated that the treatment was unlikely to demonstrate sufficient efficacy. The decision marks a setback for one of the company’s key late-stage development programs.
The Paris-based pharmaceutical company launched two phase 3 studies of riliprubart in 2024. The antibody targets C1s in the classical complement pathway and was being developed as a potential subcutaneous alternative to intravenous immunoglobulin therapy. The studies enrolled different groups of CIDP patients.
One trial was designed to compare riliprubart with placebo over a 24-week period in approximately 140 patients whose disease had not responded to immunoglobulin or corticosteroid treatment. On June 10, Sanofi announced that the study had been terminated early following a review of interim data conducted by an independent data monitoring committee.
According to the company, the analysis concluded that the therapy was unlikely to provide sufficient efficacy in the study population.
Sanofi is still evaluating the future of its second phase 3 study. That trial compares riliprubart with intravenous immunoglobulin in patients who previously responded to standard treatment and are receiving a stable maintenance dose. The company has not yet announced whether that study will proceed as planned.
The phase 3 outcome contrasts with results previously reported from a phase 2 study. At Week 24 of that earlier trial, 87% of patients who had been receiving standard-of-care treatment improved or remained stable after switching to riliprubart. The drug also appeared to show similar activity in patients whose disease had not responded to standard therapies during the midstage study. However, the phase 3 trial in that population did not generate evidence sufficient to support further development.
Riliprubart is among the programs Sanofi has identified as an important mid- to late-stage asset. Analysts at Guggenheim Securities highlighted the drug in a note to investors last year as one of several pipeline candidates expected to deliver potentially value-creating data in 2027. They estimated that riliprubart could generate sales of 480 million euros, or approximately $555 million, in 2033.
The phase 3 studies had originally been expected to produce results this year, but Sanofi delayed the timelines because of slower-than-expected patient enrollment. After modifying its screening procedures, the company reported improved recruitment rates. During a first-quarter earnings call in April, Houman Ashrafian, Ph.D., head of research and development at Sanofi, said the company was “optimistic about the impact riliprubart can have on patient outcomes.”
The setback adds to a series of recent clinical disappointments for Sanofi. These include the anti-OX40L-ligand antibody amlitelimab failing a phase 2 asthma study, the oral TNF inhibitor balinatunfib missing the primary objective of a midstage psoriasis trial, and the Regeneron-partnered IL-33 candidate itepekimab failing one of two phase 3 studies in chronic obstructive pulmonary disease.
The implications of the setback extend beyond Sanofi. Immunoglobulin manufacturers, including CSL Behring, Grifols, and Pfizer, could benefit if riliprubart does not reach the market. Meanwhile, Argenx is conducting phase 3 trials of a C2 inhibitor in CIDP, and Dianthus Therapeutics is advancing its C1 inhibitor claseprubart through phase 3 development.
Sanofi has announced the discontinuation of its Phase 3 clinical trial evaluating riliprubart for the treatment of chronic inflammatory demyelinating polyneuropathy (CIDP). The decision by Sanofi followed a planned interim review that assessed the study’s progress and likelihood of achieving its primary objectives.
The move highlights the importance of data-driven decision-making in clinical development, where companies regularly evaluate ongoing studies to ensure resources are directed toward the most promising therapeutic opportunities.
Interim Review Influences Sanofi Decision
The interim analysis conducted by Sanofi provided critical insights into the performance of riliprubart within the study population. Based on the findings, Sanofi determined that continuing the trial was unlikely to deliver the desired outcomes necessary to support future regulatory submissions.
Interim reviews play a key role in modern drug development by helping organizations identify challenges early and make informed decisions regarding program continuation or termination.
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