The Food and Drug Administration has paused new patient enrollment in trials of opakalim, an experimental epilepsy drug also known as BHV-7000, over questions raised in rodent studies. Biohaven disclosed in a filing with the U.S. Securities and Exchange Commission that the FDA issued a partial clinical hold letter on Sept. 4.
According to the filing, there was not enough information about a specific metabolite, a substance produced when the body breaks down a drug, to assess its risk to people. Dosing continues for the more than 600 patients already randomized, or assigned to a study group, across the program. No new patients can join until additional animal studies are completed.
The decision matters most to adults whose epilepsy has not responded to existing medicines and to families weighing whether to join a trial. About 2.9 million U.S. adults reported having active epilepsy in 2021 and 2022, and about 1.5 million reported seizures that were not controlled in the past year, according to CDC epilepsy figures. For many of them, clinical trials can offer access to a new option.
Enrolled Patients Continue Treatment While New Sign-Ups Stop
Biohaven is running two late-stage studies in refractory focal epilepsy, a form in which seizures begin in one area of the brain and continue despite treatment. One of them, BHV7000-303, finished enrolling in June, so the pause does not change its timeline, the company said. Top-line results, the first summary of the main findings, remain expected in the second half of 2026.
The second pivotal study, BHV7000-302, and an open-label extension study will keep dosing current participants but cannot add new ones. Biohaven said it voluntarily applied the same plan at its study sites outside the United States. ClinicalTrials.gov lists an estimated completion date of December 2026 for BHV7000-302, an estimate posted before the hold.
The company said more than 1,200 people have received the drug across its development program and that it has generally been safe and well tolerated. Biohaven said the significance of the animal finding to humans is uncertain. “The findings may be specific to rodents and not relevant to human safety,” the company wrote.
Biohaven said additional animal data are expected in the coming weeks. The FDA will need to review those results before deciding whether to lift the hold.
The Evidence Gap Behind the Hold
The most important limitation is that the public does not know what the rodent studies showed. Biohaven has not identified the metabolite, described the effect seen in animals, or said at what doses it appeared. No harm in human participants has been reported.
Metabolite questions are common in drug development, because animals and people can break down the same drug differently. Regulators often ask for extra studies to show whether a substance seen in animals also forms in humans and at what levels.
A partial clinical hold is a precaution, not a finding that a drug is dangerous. It means the FDA wants more information before exposing additional people to an experimental treatment, while allowing current participants to continue under monitoring.
Opakalim is designed to calm overactive brain signaling by opening Kv7 potassium channels, which act as brakes on nerve cells. Biohaven describes it as a selective, next-generation option for focal epilepsy, but its effectiveness has not yet been shown in a completed pivotal trial.
A Licensing Deal Raises the Stakes for Biohaven
The hold arrived weeks after Biohaven agreed on Aug. 26 to license its Kv7 drug platform, including opakalim, to South Korea’s SK Biopharmaceuticals. According to BioPharma Dive, the deal is worth up to $795 million, including $350 million upfront, and Biohaven shares fell more than 10% after the hold was disclosed.
Biohaven said it shared all clinical and animal data about the metabolite with SK Biopharmaceuticals before the agreement was signed. The deal has not closed, and the companies are still completing a required U.S. antitrust filing.
For patients, the business details matter mainly because they could affect how quickly the drug moves forward. An RBC Capital Markets analyst quoted by BioPharma Dive wrote that the paused BHV7000-302 study may ultimately be needed for approval, so delays in its enrollment could push back any FDA application.
Guidance for Patients and Families Considering a Trial
People already enrolled in an opakalim study should keep following their study team’s instructions and raise any questions with the trial site. Anyone who was in screening for a paused study should expect the site to explain next steps.
No one should stop or change a prescribed seizure medicine without speaking to a neurologist, because stopping suddenly can trigger dangerous seizures. Families looking for other research options can search ClinicalTrials.gov and ask an epilepsy specialist which studies fit their situation.
The CDC’s first aid guidance for seizures advises calling 911 when a seizure lasts longer than five minutes, another seizure follows soon after, or the person has trouble breathing, has trouble waking, or is injured. Families caring for someone with uncontrolled seizures should keep a written seizure log and a current medication list for appointments.
Cost remains a major barrier in epilepsy care. CDC data show adults with epilepsy are more likely than other adults to skip medicine doses to save money or to be unable to afford specialty care, which is one reason trial access carries real weight for many households. The next developments to watch are Biohaven’s new animal data, the FDA’s response, and the top-line results expected later this year.
Key Questions Answered
What did the FDA do? It placed a partial clinical hold on trials of Biohaven’s experimental epilepsy drug opakalim, also called BHV-7000, pausing new patient enrollment as of Sept. 4, 2026.
Why was the hold issued? Rodent studies identified a metabolite, and there was not enough information to assess its risk to humans, according to Biohaven’s filing.
Can current trial participants keep taking the drug? Yes. Dosing continues for the more than 600 patients already randomized.
Has anyone been harmed? Biohaven has reported no human harm and says the drug has generally been safe and well tolerated in more than 1,200 participants.
What did the animal studies show? Biohaven has not publicly described the metabolite or the effects observed.
When will trial results arrive? Biohaven says top-line results from its fully enrolled pivotal study remain expected in the second half of 2026.
Should patients change their current seizure medicine? No. Do not stop or change seizure medication without speaking to a neurologist, because stopping suddenly can trigger dangerous seizures.
