The US Food and Drug Administration (FDA) has granted fast track designation to SAR446268, Sanofi's one-time AAV gene therapy for the treatment of non-congenital (juvenile and adult onset) DM1 myotonic dystrophy type 1 (DM1). This designation process aims to facilitate the development and expedite the review of medicines to treat serious conditions and fill an unmet medical need. The FDA created this process to help deliver important new medicine to patients earlier and it covers a broad range of serious illnesses.

SAR446268 employs a vectorised RNA interference (RNAi) approach to silence DMPK expression through a single administration. By reducing DMPK transcripts, the gene therapy aims to eliminate the abnormal and toxic RNA foci responsible for splicing defects in muscle tissue, thereby restoring normal splicing and improving muscular function. This approach has the potential to address key symptoms of the disease, including progressive muscle weakness, difficulty relaxing muscles (myotonia) and effects on multiple body systems including heart, lungs and endocrine functions.

SAR446268 is the only investigational therapy in clinical development for this disease, and there are no currently approved therapies for DM1.

SAR446268 is currently under investigation in a first-in-human, phase I/II study to evaluate the safety, tolerability and efficacy (clinical study identifier: NCT06844214). The first patient is planned for enrolment in late 2025. Sanofi has already been granted orphan designations for SAR446268 in both the US (July 2024) and EU (October 2024).