Eisai has kicked off a mid-stage study assessing its potential first-in-class experimental therapy lemborexant in Alzheimer's patients with Irregular Sleep-Wake Rhythm Disorder (ISWRD).

ISWRD is a circadian rhythm sleep disorder characterised by an irregular sleep-wake pattern, with patients experiencing multiple naps during the daytime but then fragmented and shortened sleep during the night.

Lemborexant is a dual orexin receptor antagonist that binds to two subtypes of orexin receptors. The orexin system is a key regulator of the sleep-wake cycle, and thus orexin receptor antagonists have the potential to counteract inappropriately timed nighttime wakefulness and to promote a regular sleep-wake cycle, the firm noted.

The Phase II double-blind, placebo-controlled, parallel-group study is geared up to assess the efficacy and safety of the drug in 125 participants aged 65 to 90 with ISWRD and mild to moderate Alzheimer's disease.

The primary objective is to evaluate the sleep efficiency and wake efficiency during the last four weeks of treatment with lemborexant compared to placebo, measured by actigraphy, a non-invasive device worn on the wrist to assess the circadian rhythm of sleep-wake patterns.

A Phase III study of lemborexant is also underway in insomnia, with the primary endpoint change from baseline in mean wake after sleep onset in the second half of the night compared with zolpidem tartrate.