Eisai Inc., the US pharmaceutical subsidiary of Eisai Co., Ltd., and Purdue Pharma L.P., a privately held pharmaceutical company, have entered into a worldwide collaboration agreement for the development and commercialisation of Eisai's clinical candidate lemborexant (E2006), a dual orexin receptor antagonist entering phase III clinical development for the treatment of insomnia.

Under the terms of the agreement, Eisai and Purdue Pharma will share the costs of lemborexant global clinical studies. While the potential indication for the product candidate is for the treatment of insomnia, the companies may also seek to develop other indications in the future. In addition, the two companies will form a joint steering committee to manage development and pursue marketing authorizations for lemborexant worldwide.

Once approved, Eisai and Purdue Pharma will co-promote the product and share co-promotion costs and profits in the United States and other territories (to be agreed by the parties), which may include the European Union, China, Japan and Canada. Eisai will book sales in all co-promotion territories. In certain other countries, either Eisai or Purdue Pharma may solely commercialise lemborexant and pay the other party a royalty. Eisai will receive an upfront payment from Purdue Pharma, and is also eligible to receive certain other milestone payments that are contingent upon achieving regulatory approval and certain commercial milestones.

Insomnia is common worldwide; approximately 30 per cent of adults report one or more symptoms of insomnia including difficulty initiating and/or maintaining sleep. Insomnia is associated with impairments in daytime functioning, including difficulty with thinking and concentration, as well as altered mood.

Discovered by Eisai, lemborexant is a dual orexin receptor antagonist which competitively binds to the two subtypes of orexin receptors. It is believed that the orexin system promotes wakefulness, and therefore, orexin receptor antagonists such as lemborexant have the potential to promote sleep.

With the signing of this agreement, the phase III clinical development programme will commence immediately. The global trial programme is designed to evaluate the efficacy of lemborexant on both objective and subjective measures of sleep. In addition, the development program will evaluate the impact of treatment of insomnia on daytime function. Safety and tolerability will also be evaluated during the clinical program.

"Eisai is excited about the significant and far-reaching potential of this compound as we commence phase III clinical trials," said Lynn D. Kramer, MD, FAAN, president of the neuroscience and general medicine product creation unit at Eisai.

"We are looking forward to collaborating with Purdue Pharma, which brings deep expertise and proven successes in drug development and commercialisation."

"This agreement reflects our strategy to diversify and grow our business through partnerships and business development," said Mark Timney, president and chief executive officer, Purdue Pharma L.P.

"We look forward to a productive relationship with Eisai and the prospects for growth this collaboration brings, as we seek to further expand our product portfolio with differentiated treatments."

Lemborexant, a dual orexin receptor antagonist, is an Eisai in-house discovered and developed small molecule which inhibits orexin by binding competitively to two subtypes of orexin receptors (orexin receptor 1 and 2). In individuals with insomnia, it is possible that the orexin system, which regulates sleep and wakefulness, is not functioning normally. During normal periods of sleep, orexin system activity is suppressed, suggesting it is possible to purposefully counteract inappropriate wakefulness and facilitate the initiation and maintenance of sleep by interfering with orexin neurotransmission. Therefore, Eisai has been developing lemborexant as a potential treatment for insomnia.