Paris:Sanofi has announced that the US Food and Drug Administration (FDA) has extended by three months the target action date of its review of the new drug application (NDA) of tolebrutinib, an oral and brain-penetrant investigational Bruton's tyrosine kinase (BTK) inhibitor to treat non-relapsing, secondary progressive multiple sclerosis (nrSPMS) and to slow disability accumulation independent of relapse activity in adult patients. Based on the submission of additional analyses during the review, the FDA has determined that the additional information constituted a major amendment to the NDA and extended the target action date accordingly. The revised target action date for the FDA decision is December 28, 2025. "Sanofi is confident in the potential positive impact tolebrutinib can provide and will continue to collaborate closely with the FDA during the review period, the company stated. Tolebrutinib was the first brain-penetrant BTK inhibitor in nrSPMS to be designated as a breakthrough therapy by the FDA. The FDA review of tolebrutinib is based on pivotal data from the global, double-blinded randomized HERCULES and GEMINI 1 and 2 phase 3 studies evaluating the efficacy and safety of tolebrutinib in patients with nrSPMS and relapsing MS (RMS), respectively. The safety and efficacy of tolebrutinib have not been established by the FDA, and it remains under review by regulatory authorities worldwide, including in the EU. In addition to the completed HERCULES and GEMINI 1 and 2 studies, the PERSEUS phase 3 study in primary progressive MS is ongoing with study results anticipated in H2 2025. Multiple sclerosis is a chronic, immune-mediated neurodegenerative disease of the central nervous system (CNS) that may result in accumulation of irreversible disabilities over time. The physical and cognitive disability impairments translate into gradual deterioration of health status, impacting patients’ care and quality of life. Disability accumulation remains a significant unmet medical need in MS. Currently, the primary target of currently approved medicines has been peripheral B and T cells, while innate immunity within the CNS which is believed to drive disability accumulation remains largely unaddressed. People living with nrSPMS refers to people with MS who have stopped experiencing relapses but continue to accumulate disability, experienced as symptoms such as fatigue, cognitive impairment, balance and gait impairment, loss of bowel and/or bladder function, sexual dysfunction, amongst others.