Biohaven Pharmaceuticals faced a significant setback when the U.S. Food and Drug Administration issued a Complete Response Letter (CRL) rejecting the company’s New Drug Application for Vyglxia (troriluzole), a promising treatment for spinocerebellar ataxia (SCA). Drugs.com reports that the rejection has sparked criticism from biotech leadership and leading neurologists regarding regulatory inflexibility for rare diseases.
A Devastating Disease with No Treatment Options
Spinocerebellar ataxia is a group of dominantly inherited neurodegenerative disorders affecting approximately 15,000 Americans and 24,000 Europeans. The disease causes progressive loss of voluntary motor control and cerebellar atrophy, leading to severe disability. Patients experience debilitating gait impairment, falls, loss of mobility requiring wheelchairs, speech impairment, swallowing difficulty, and premature death. Critically, currently no FDA-approved treatments or cures exist for this devastating condition.
Compelling Clinical Evidence
Biohaven’s eight-year development effort produced substantial clinical data supporting Vyglxia’s efficacy. The company’s real-world evidence study demonstrated that troriluzole achieved “highly consistent, sustained, robust and clinically meaningful treatment effects,” slowing disease progression by 50-70% with a safe, once-daily oral formulation. The application further documented that Vyglxia reduced fall risk and delayed progression to wheelchair dependence. The study protocol and statistical analysis plan were pre-reviewed by the FDA prior to data analysis, and leading SCA experts across the United States directly communicated their support for the troriluzole data to regulators.
Mechanism of Action
Troriluzole, a novel third-generation prodrug, modulates glutamate—the brain’s most abundant excitatory neurotransmitter. The medication increases glutamate uptake from synapses by enhancing excitatory amino acid transporter expression on glial cells. This mechanism addresses glutamate deregulation underlying neurodegeneration and Purkinje cell dysfunction in SCA patients.
Regulatory Controversy
CEO Vlad Coric expressed substantial disappointment, arguing that the FDA failed to apply regulatory flexibility mandated by Congress for rare diseases. “Patients with rare diseases also deserve an efficient, fair and flexible regulatory process that aligns with the urgency of their high unmet medical needs,” Coric stated. He criticized the FDA’s Office of Neuroscience for rejecting alternative regulatory pathways including Advisory Committee review involving experts and patients, post-marketing studies, labeling limitations, or accelerated approval.
Dr. Jeremy Schmahmann, Professor of Neurology at Harvard Medical School and Founding Director of the Ataxia Unit at Massachusetts General Hospital, concurred, characterizing the FDA’s decision as “a misstep in due process” and “a failure to deploy regulatory flexibility” for a medication proven safe and effective.
Strategic Pivot
Rather than abandon rare disease development, Biohaven announced strategic restructuring with approximately 60% reductions in annual direct R&D spending. The company will prioritize three key programs: BHV-1400 and BHV-1300 (extracellular degraders for IgA nephropathy and Graves’ disease), Opakalim (Kv7 ion channel activator for epilepsy and depression), and Taldefgrobep alfa (myostatin-activin pathway inhibitor for spinal muscular atrophy and obesity).
Biohaven remains committed to finding a path forward with the FDA, planning meetings to discuss next steps. The rejection highlights ongoing tensions between regulatory standards and the urgency facing patients with progressive rare diseases lacking therapeutic alternatives.
