Eisai and Purdue have formed a global development and commercialisation pact for Eisai's experimental insomnia therapy lemborexant.

The companies said they intend to share the cost of developing the drug - a dual orexin receptor antagonist - which is entering Phase III development for insomnia but may also be assessed in other indications under the alliance.

If successful, lemborexant will be co-promoted in the US, and potentially other territories, with related costs and profits shared. In other countries, either company can potentially solely market the drug, paying the other a royalty. 

Also under the terms, Eisai will receive an undisclosed upfront payment from Purdue as well as certain other regulatory and commercial milestone payments.

Around 30% of adults around the globe report one or more symptoms of insomnia including difficulty initiating and/or maintaining sleep. Lemborexant works by inhibiting orexin - which is believed to promote wakefulness. 

Financial specifics of the agreement were not disclosed.