Tasimelteon

Toxicity

The most common adverse reactions are headache, increased alanine aminotransferase, nightmares or unusual dreams, and upper respiratory or urinary tract infections. There are currently no adequate or well-controlled studies that suggest that tasimelteon is safe to use during pregnancy. In animal studies, administration of tasimelteon during pregnancy resulted in developmental toxicity (embryofetal mortality, neurobehavioral impairment, and decreased growth and development in offspring) at doses greater than those used clinically. During clinical trials, rats did not self-administer tasimelteon, suggesting that the drug does not have a potential for abuse.

Description

Tasimelteon, which is marketed by Vanda Pharmaceuticals as Hetlioz and developed in partnership with Bristol-Myers Squibb, is a drug that was approved by the US FDA in January 2014 for the treatment of non-24-hour sleep–wake disorder (also called Non-24, N24 and N24HSWD). Tasimelteon is a melatonin MT1 and MT2 receptor agonist; because it exhibits a greater affinity to the MT2 receptor than MT1, is also known as Dual Melatonin Receptor Agonist.234 Two randomized controlled trials (phases II and III) demonstrated that tasimelteon improved sleep latency and maintenance of sleep with a shift in circadian rhythms, and therefore has the potential to treat patients with transient insomnia associated with circadian rhythm sleep disorders. Preclinical studies showed that the drug has similar phase-shifting properties to melatonin, but with less vasoconstrictive effects.

The Uses of Tasimelteon

Tasimelteon is a novel drug, used in the treatment of non-24 hour sleep-wake disorder. It helps to correct the circadian rhythm disorder often seen in patients who are visually impaired.

Indications

Tasimelteon oral capsules are indicated for the treatment of non-24 hour sleep-wake disorder in adult patients and for the treatment of nighttime sleep disturbances in Smith-Magenis Syndrome in patients ≥16 years old. Tasimelteon oral suspension is indicated for the treatment of nighttime sleep disturbances in Smith-Magenis syndrome in patients 3 to 15 years of age.

Background

Tasimelteon is a selective dual melatonin receptor agonist indicated for the treatment of Non-24-Hour Sleep-Wake Disorder (N24HSWD). Occurring commonly in blind individuals without light perception, this condition is often characterized by periods of night-time insomnia and day-time sleepiness. In blind individuals, a lack of light stimulation causes an extension of the 24-hour circadian cycle and can lead to progressively delayed sleep onset. By activating melatonin receptors MT1 and MT2 in the suprachiasmatic nucleus of the brain, tasimelteon has been shown to improve sleep by resynchronizing the circadian rhythm through its "non-photic" mechanism. Tasimelteon is currently the only drug available for the treatment of N24HSWD and was granted orphan drug status by the FDA in 2010.

Definition

ChEBI: A member of the class of 1-benzofurans that is propionamide in which one of the amide hydrogens is replaced by a [(1R,2R)-2-(2,3-dihydro-1-benzofuran-4-yl)cyclopropyl]methyl group. A melatonin receptor agonist used for the treatment of non-24-hour sleep-wake disorder.

Synthesis

Activation of commercial bis-ethanol 250 with 2.5 equivalents of the Vilsmeier salt 251 followed by treatment with base resulted an intramolecular cyclization reaction with the proximal phenol and concomitant elimination of the remaining imidate to deliver the vinylated dihydrobenzofuran 252 in 76% yield. Interestingly, this reaction could be performed on multi-kilogram scale, required no chromatographic purification, and generated environmentallyfriendly DMF and HCl as byproducts. Sharpless asymmetric dihydroxylation of olefin 252 delivered diol 253 in 86% yield and impressive enantioselectivity (>99% ee). This diol was then activated with trimethylsilyl chloride and then treated with base to generate epoxide 254. Next, a modified Horner¨CWadsworth¨C Emmons reaction involving triethylphosphonoacetate (TEPA, 255) was employed to convert epoxide 254 to cyclopropane 256. The reaction presumably proceeds through removal of the acidic TEPA proton followed by nucleophilic attack at the terminal epoxide carbon. The resulting alkoxide undergoes an intramolecular phosphoryl transfer reaction resulting in an enolate, which then attacked the newly formed phosphonate ester in an SN2 fashion resulting in the trans-cyclopropane ester, which was ultimately saponified and re-acidified to furnish cyclopropane acid 256. Conversion of this acid to the corresponding primary amide preceded carbonyl reduction with sodium borohydride. The resulting amine was acylated with propionyl chloride to furnish tasimelteon (XXXI) as the final product in 86% yield across the four-step sequence.

Metabolism

Tasimelteon is extensively metabolized. Metabolism of tasimelteon consists primarily of oxidation at multiple sites and oxidative dealkylation resulting in opening of the dihydrofuran ring followed by further oxidation to give a carboxylic acid. CYP1A2 and CYP3A4 are the major isozymes involved in the metabolism of tasimelteon. Phenolic glucuronidation is the major phase II metabolic route.

storage

Store at -20°C