About YKP3089C035

YKP3089C035 was a randomized, double-blind, placebo-controlled, multinational Phase 3 clinical study conducted in South Korea, China, and Japan. In this study, the efficacy and safety of XCOPRI as adjunctive therapy was evaluated in adult patients aged 18–70 with uncontrolled partial-onset (focal) seizures on 1-3 ASMs. Patients were randomly allocated in a 1:1:1:1 ratio to adjunctive placebo or adjunctive XCOPRI 100, 200, or 400 mg once daily.
All dosage groups of XCOPRI achieved the primary efficacy endpoint, showing a significant reduction in the median percent change in seizure frequency during the 6-week maintenance phase compared with the placebo group. XCOPRI 400 mg group showed a 100% reduction in the median seizure frequency during the maintenance period (Placebo: 25.9% vs XCOPRI: 42.6% for 100 mg, 78.3% for 200 mg, and 100% for 400 mg). In the secondary endpoints for efficacy, all dosage groups of XCOPRI showed significantly higher seizure-free rate* compared with the placebo group (Placebo: 2.6% vs XCOPRI: 12.4% for 100 mg, 30.1% for 200 mg, and 52.4% for 400 mg). The most common adverse events with the incidence of 20% or more in XCOPRI groups were dizziness and somnolence.
The results of this study were presented in a poster session at the 2024 Annual Meeting of the American Epilepsy Society (AES).1
*The maximum rate of seizure-free, which aligns with the goal in epilepsy treatment, in adjunctive therapy with existing ASMs is reported to be around 6.4%.2

About Epilepsy

Epilepsy is a chronic brain disorder in which seizures are triggered by abnormal excitability of nerve cells in the brain. In Japan, approximately 1 million people are estimated to have epilepsy, which generally requires long-term drug therapy.3 Thirty percent of epilepsy patients do not achieve adequate seizure control with existing ASMs.4,5 Epilepsy is a disease with high unmet medical needs for which new ASMs are still anticipated.

Overview of XCOPRI® Tablets

About XCOPRI

Although the precise mechanism by which XCOPRI exerts its therapeutic effects remains unknown, XCOPRI reduces repetitive neuronal firing by inhibiting voltage-dependent sodium currents. In addition, XCOPRI positively modulates γ-aminobutyric acid type A (GABAA) ion channels. Based on its clinical results, XCOPRI has demonstrated efficacy and is expected to become a new treatment option that has been associated with seizure freedom in a proportion of patients in clinical studies, which is consistent with the goal of epilepsy treatment. As of September 2026, XCOPRI is approved as a treatment for partial-onset seizures in more than 45 countries or regions worldwide, including in the U.S. and Europe (where it is marketed as ONTOZRY®).
In Japan, Ono is conducting Phase 3 clinical study of XCOPRI for the treatment of primary generalized tonic-clonic (PGTC) seizures in adolescents and adults as well as Phase 3 clinical study for the treatment of pediatric patients with partial-onset seizures.

About Partnership with SK Biopharmaceuticals Co., Ltd.

In 2020, Ono entered into a licensing agreement with SK Biopharmaceuticals Co., Ltd. (headquartered in Gyeonggi-do, South Korea) which originally discovered and developed the anti-seizure medication (ASM) XCOPRI. Through this agreement, Ono has obtained the exclusive rights to develop and commercialize XCOPRI in Japan. SK Biopharmaceuticals and its U.S. subsidiary, SK Life Science Inc., are global pharmaceutical companies focused on the research, development, and commercialization of treatments for central nervous system (CNS) disorders. Their pipeline includes 7 development compounds for CNS diseases, including epilepsy. In addition, SK Biopharmaceuticals is actively engaged in early-stage oncology research. Further information can be found on the SK Biopharmaceuticals website ( www.skbp.com/eng ) and the SK Life Science Inc. website ( www.SKLifeScienceInc.com ).