SK Biopharm has announced that its partner, Ono Pharmaceutical, has received approval from Japan’s Ministry of Health, Labour and Welfare (MHLW) for cenobamate, an innovative treatment for epilepsy marketed in Japan under the brand name Xcopri.
Japan is the world’s second-largest single-country epilepsy market after the United States, with an estimated 1 million people living with epilepsy. About 30% are believed to have difficulty achieving adequate seizure control with existing anti-seizure medications.
The approval is expected to provide a new treatment option for Japanese epilepsy patients with significant unmet medical needs.
The Japanese approval was based on results from the multinational Phase 3 YKP3089C035 trial, which enrolled adults in Korea, China and Japan with focal-onset seizures that remained inadequately controlled despite treatment with existing anti-seizure medications.
In the trial, adjunctive treatment with cenobamate significantly reduced seizure frequency compared with placebo, meeting the primary endpoint while demonstrating a manageable safety profile.
With the Japanese approval, SK Biopharm has now secured new-drug approvals for cenobamate across all three major Northeast Asian markets—Korea, China and Japan—through local partners.
The company received approvals in Korea and China in November and December 2025, respectively. In China, cenobamate officially launched in March 2026, when the first prescriptions were issued. In Japan, Ono Pharmaceutical submitted a New Drug Application (NDA) in September 2025 and has now obtained regulatory approval, establishing the foundation for entry into the Japanese market.
SK Biopharm signed a licensing agreement with Ono Pharmaceutical in October 2020 for the development and commercialization of cenobamate in Japan. Under the agreement, SK Biopharm will receive a milestone payment following the approval, although the specific amount has not been disclosed under the terms of the contract.
The company is also expected to receive royalties tied to cenobamate sales in Japan. As commercialization expands, the Japanese market is expected to make a growing contribution to SK Biopharm’s earnings over the medium to long term.
Cenobamate has now been approved as a treatment for focal-onset seizures in adults in more than 45 countries and regions worldwide, including the United States and Europe. In the United States, SK Biopharm’s local subsidiary, SK Life Science, directly markets the drug.
Alongside expanding cenobamate’s global market presence, SK Biopharm is pursuing additional indications and age-group expansions. In Japan, Ono Pharmaceutical is conducting a Phase 3 trial in adolescents and adults with primary generalized tonic-clonic seizures (PGTCS). A separate Phase 3 trial is also underway in pediatric patients with focal-onset seizures.
Donghoon Lee, president and CEO of SK Biopharm, said, “Japan is a critical market that must be secured for cenobamate’s global growth, given both the demand for epilepsy treatment and the size of the market. With this approval, we have completed the foundation for entry into the major Northeast Asian markets linking Korea, China and Japan. We will now focus on turning that market access into tangible commercialization results through prescriptions for patients in each market.”
Cenobamate is an epilepsy treatment developed by SK Biopharm, which led the drug’s development from candidate discovery through clinical development. It is an anti-seizure medication that suppresses seizures by regulating excessive and abnormal neural signals in the brain.