Sanofi’s MS Drug Rejected After Six Hy’s Law Cases; Backs Enable with $30M
The FDA issued a complete response letter rejecting Sanofi’s tolebrutinib application for non-relapsing secondary progressive multiple sclerosis after six Hy’s Law liver injury cases, including one death requiring transplant, said no subpopulation benefited from its risk profile. Sanofi also committed $30 million to Enable Injections’ enFuse manufacturing expansion and won FDA priority review to expand Tzield use to children as young as one with type 1 diabetes.
1. FDA Rejects Tolebrutinib Application Over Liver Safety Concerns
The U.S. Food and Drug Administration issued a complete response letter rejecting Sanofi’s new drug application for tolebrutinib in non-relapsing secondary progressive multiple sclerosis. In its letter, the agency cited six confirmed cases of severe drug-induced liver injury meeting Hy’s Law criteria during the pivotal Phase III program, including one fatality that required a liver transplant. The FDA concluded that Sanofi had not demonstrated a positive benefit-risk profile for any patient subgroup, pointing to both insufficient efficacy signals and unacceptable hepatic safety risks. Sanofi now faces the prospect of additional clinical studies or a reformulated safety monitoring plan before resubmission, potentially delaying approval by 18 to 24 months and impacting expectations for its multiple sclerosis portfolio.
2. Sanofi Commits $30 Million to Enable Injections Manufacturing Expansion
Sanofi will invest $30 million in Enable Injections to accelerate the build-out of its enFuse® On-Body Delivery System manufacturing capacity in Springdale, Ohio. The funding supports construction of new clean-room facilities and installation of automated assembly lines, enabling Enable to boost output by 200% by year-end 2027. The enFuse platform, which subcutaneously administers large-volume oncology and biologic therapies, has already been used in Sarclisa phase III and II trials. Sanofi’s latest injection builds on its leadership of Enable’s 2018 Series B and participation in the $215 million Series C round in 2022. With global demand for patient-friendly injectables rising 15% annually, this partnership aims to secure Sanofi’s supply chain and position the company for joint commercial launches starting in 2026.
3. FDA Grants Priority Review for Tzield in Young Children
The FDA has accepted Sanofi’s supplemental biologics license application for Tzield® (teplizumab-mzly) to delay the onset of type 1 diabetes in children aged one to eight years. The agency’s priority review voucher targets an action date in the third quarter of 2026. Sanofi’s filing is supported by the Phase II/III PROTECT trial, which showed a 27% reduction in progression to clinical diabetes over two years in the younger cohort, with an adverse event rate comparable to that seen in adolescents. Expansion into this population could unlock a new patient pool of approximately 5,000 U.S. children diagnosed annually with stage 2 type 1 diabetes, potentially generating incremental annual revenues of $150 million upon approval.