Tokyo-based Eisai Co Ltd presented data from a Phase II clinical study (Study 201) on its in-house-developed investigational dual orexin receptor antagonist (DORA) E2006 in patients with insomnia at the 53rd American College of Neuropsychopharmacology (ACNP) Annual Meeting held from December 7 through 11 in Phoenix. In the study, E2006 demonstrated a statistically significant improvement in sleep initiation and sleep maintenance without increasing next-day residual sleepiness when compared with placebo.

E2006 is a novel DORA discovered by Eisai. As orexins are neuropeptides that are major regulators of the neural mechanisms underlying sleep and wakefulness, E2006 is being developed for the potential treatment of insomnia. The drug competitively binds to two subtypes of orexin neuron receptors, interfering with orexin neurotransmission to facilitate sleep onset and maintenance.

Study 201 was a multicenter, randomized, placebo-controlled, parallel-group Phase II clinical study conducted in the United States. The primary objective was to identify at least one dose of E2006 that could provide a satisfactory balance of sleep efficiency (total sleep time as a proportion of time in bed) and next-day residual sleepiness; 291 patients with insomnia disorder were randomized to receive one of six doses of E2006 (1 mg, 2.5 mg, 5 mg, 10 mg, 15 mg, 25 mg) or placebo for 15 days.

Compared to baseline, E2006 statistically significantly improved mean sleep efficiency at all doses. E2006 also shortened both latency to persistent sleep (LPS) and wake after sleep onset (WASO), demonstrating a statistically significant reduction compared to placebo at all dosage amounts of 2.5 mg and higher for LPS, and 10 mg and higher for WASO, respectively. Moreover, the only E2006 group to show a statistically significant increase compared to placebo in next-day residual sleepiness as measured by the Karolinska Sleepiness Scale (KSS) was at the dose of 25 mg.

The most common treatment-emergent adverse events reported in patients treated with E2006 (overall group) were somnolence, headache, and sleep paralysis. Based on the results of study 201, Eisai is making preparations in cooperation with the health authorities in various countries toward conducting Phase III studies for E2006. Eisai considers integrative neuroscience to be a therapeutic area of focus, and is committed to the development of drugs such as E2006. Through these efforts, Eisai is committed to addressing the unmet medical needs that exist in the field of neuroscience and making contributions to further increase the benefits to patients and their families.