Melatonin receptor agonist

Melatonin receptor agonists are analogues of melatonin that bind to and activate the melatonin receptor. Agonists of the melatonin receptor have a number of therapeutic applications including treatment of sleep disorders and depression. The discovery and development of melatonin receptor agonists was motivated by the need for more potent analogues than melatonin, with better pharmacokinetics and longer half-lives. Melatonin receptor agonists were developed with the melatonin structure as a model. The melatonin receptors are G protein-coupled receptors and are expressed in various tissues of the body. There are two subtypes of the receptor in humans, melatonin receptor 1 (MT1) and melatonin receptor 2 (MT2). Melatonin and melatonin receptor agonists, on market or in clinical trials, all bind to and activate both receptor types. The binding of the agonists to the receptors has been investigated since 1986, yet is still not fully understood. When melatonin receptor agonists bind to and activate their receptors it causes numerous physiological processes. In 1917 McCord and Allen discovered melatonin itself. In 1958, Aaron B. Lerner and his colleagues isolated the substance N-acetyl-5-methoxytryptamine and named it melatonin. High-affinity melatonin binding sites were pharmacologically characterized in the bovine brain in 1979. The first melatonergic receptor was cloned from melanophores of Xenopus laevis in 1994. In 1994-1995 the melatonin receptors were characterized and cloned in the human being by Reppert and colleagues. TIK-301 (PD-6735, LY-156735) has been in phase II clinical trial in the United States (US) since 2002. The FDA granted TIK-301 orphan drug designation in May 2004, to use as a treatment for circadian rhythm sleep disorder in blind individuals without light perception and individuals with tardive dyskinesia. In 2005 ramelteon (Rozerem) was approved in the US indicated for treatment of insomnia, characterized as difficulty with falling asleep, in adults.