Eisai Co., Ltd. has announced that its novel selective orexin 2 receptor agonist, E2086, has received orphan drug designation from Japan's Ministry of Health, Labour and Welfare (MHLW) for the treatment of narcolepsy. This designation aims to support the development of drugs for diseases with small patient populations and high unmet medical needs.
Narcolepsy, a chronic sleep disorder characterized by excessive daytime sleepiness (EDS), affects an estimated 46,000 people in Japan. The disorder is divided into two subtypes: type 1, which involves cataplexy, and type 2, which does not. The pathogenesis of type 1 is linked to an autoimmune destruction of orexin-producing neurons, while the cause of type 2 remains unknown, though it may involve reduced orexin neurotransmission.
E2086 is designed to activate orexinergic neurons, potentially improving symptoms by enhancing orexin receptor activity. Eisai presented Phase Ib clinical study data at the World Sleep 2025 congress, suggesting that E2086 could improve daytime wakefulness in narcolepsy type 1 patients.
The orphan drug designation system in Japan offers several development incentives, including prioritized consultation, reduced application fees, and tax incentives, to encourage drug development for rare diseases. To qualify, a drug must be intended for use by fewer than 50,000 people in Japan and offer significant efficacy or safety improvements over existing treatments.
Eisai has previously developed DAYVIGO, an orexin receptor antagonist for insomnia, leveraging its orexin platform. The company views neurology, including sleep-wake disorders, as a key therapeutic area and aims to address high unmet medical needs through innovative products.