FDA seeks additional data on metabolite toxicity seen in rodent studies

Current patients to continue treatment; RISE3 topline timeline for second half unaffected

Company cites no related adverse events among 1,200 trial subjects, working closely with Biohaven before deal closes

[Courtesy of SK Biopharm]
[Courtesy of SK Biopharm]

The US Food and Drug Administration has placed a partial clinical hold on opacalim (BHV-7000), the next-generation epilepsy drug candidate that SK Biopharm recently agreed to license in. The company said the issue stems from a rodent-specific finding that it had already reviewed during due diligence before signing the deal. It added that the finding is likely unrelated to human safety.

SK Biopharm disclosed Thursday that Biohaven, the US biotech that originally developed opacalim, had been notified by the FDA of a partial clinical hold on the drug's Phase 2/3 trials, known as RISE2 and RISE3.

The FDA requested additional nonclinical data after toxicity was observed in a study in which a specific metabolite of opacalim was administered to rats. The agency sought the data to determine whether the effect was specific to rodents. The trial in question is a multicenter, randomized, double-blind, placebo-controlled Phase 2/3 study evaluating the efficacy, safety and tolerability of opacalim in patients with drug-resistant focal seizures.

Patients currently receiving the drug may continue treatment, but enrollment of new patients will be paused until the additional nonclinical studies are completed. However, the RISE3 trial has already completed patient enrollment and randomization, so it will not be affected by the hold. The company said its plan to release topline results in the second half of 2026 remains unchanged.

SK Biopharm said it had already closely reviewed the toxicity finding during due diligence before signing the licensing agreement. Based on data gathered at the time and assessments by multiple outside experts with FDA pharmacology and toxicology review experience, the company concluded the finding was likely specific to rodents. It added that the finding was unrelated to human safety.

Opacalim has been tested in clinical trials involving more than 1,200 subjects to date, and no adverse events directly linked to the nonclinical toxicity finding have been identified. Biohaven, the drug's original developer, plans to submit additional nonclinical evaluation data on the specific metabolite in consultation with the FDA. It aims to have the partial clinical hold lifted as soon as possible.

The licensing agreement between SK Biopharm and Biohaven for opacalim has not yet reached deal closing. Management from both companies is in close consultation over the matter and is working together to resolve the clinical hold.


silverpaper@heraldcorp.com