Tasimelteon, developed by Vanda
Pharmaceuticals Inc under license from Bristol-Myers Squibb Co, is a
melatonin receptor agonist. Because of the high density of
melatonin receptors in the circadian pacemaker, the suprachiasmatic nucleus, melatonergic actions can phase-shift circadian rhythms and promote sleep.
Tasimelteon was effective in reducing sleep onset latency (in phase II and III clinical trials) and in resetting the circadian
melatonin rhythm (in phase II trials), which indicated its potential suitability as treatment for
jet lag, shift work and
circadian rhythm sleep disorders. Statistically significant improvements in sleep maintenance have also been observed with the
drug.
Tasimelteon has been claimed to be useful in the treatment of depression, and preclinical evidence in this respect is to be confirmed in a phase II clinical trial, which was ready to be initiated at the time of publication. It is plausible that the
drug may be effective in the treatment of
depressive disorders, at least those that are related to circadian dysfunction, and that it may attenuate sleep problems in depressed patients of different subtypes. A general suitability in mitigating other symptoms of
major depressive disorder cannot be deduced from the actions of
tasimelteon via the
melatonin receptors MT1 and MT2. The
drug is well tolerated, does not induce impairment of next-day functioning or dependence, and seems to be safe in short-term treatment; however, toxicological data would be required for assessing its long-term safety.