FDA Delays Decision on Biohaven's Troriluzole for Spinocerebellar Ataxia, Plans Advisory Committee Meeting

The U.S. Food and Drug Administration (FDA) has extended its review period for Biohaven's investigational glutamate modulator troriluzole, pushing the decision date into the fourth quarter of 2025. This three-month delay for the potential first-ever treatment for spinocerebellar ataxia (SCA) comes as a surprise to industry analysts and investors, given the proximity to the completed mid-cycle review.

Regulatory Review Extension and Advisory Committee Plans

Biohaven announced on Wednesday evening that the FDA requires additional time to review supplementary data submitted by the company in response to agency queries. The delay is purportedly part of the routine review process, with Biohaven management stating they have responded to the FDA's questions "in a timely manner."

In a significant development, the FDA now intends to convene an advisory committee to discuss troriluzole's application. While not unexpected for a potential first-in-class therapy, this decision represents a change in the agency's approach. The advisory committee meeting has yet to be scheduled.

Troriluzole's Mechanism and Clinical Promise

Troriluzole functions by modulating glutamate, a key excitatory neurotransmitter. The drug increases glutamate uptake from the synapse, effectively lowering its concentration in the synaptic space. This mechanism aims to prevent neuronal overexcitation, a factor in SCA pathology.

In September 2024, Biohaven released topline data from a pivotal trial demonstrating troriluzole's ability to slow SCA disease progression by 50% to 70% compared to untreated controls. These results have bolstered optimism for the drug's potential approval, despite the current regulatory delay.

FDA Delays and Industry Context

The postponement of troriluzole's review is not an isolated incident. Recent weeks have seen similar delays affecting other pharmaceutical companies, including GSK's Nucala for chronic obstructive pulmonary disease, Stealth BioTherapeutics' Barth Syndrome application, and Novavax's COVID-19 vaccine.

While some industry observers speculate that these delays may be related to recent layoffs and restructuring at the FDA, analysts at William Blair note that extended reviews are not uncommon in the neuroscience space. They cite a similar delay for argenx's supplemental application for Vyvgart Hytrulo in myasthenia gravis in January 2023.

Despite the setback, William Blair analysts remain "optimistic that the FDA will show more regulatory flexibility" toward troriluzole, citing the rare-disease nature of SCA, the lack of existing treatment options, and the drug's risk-benefit profile.