US approves Merck & Co.'s insomnia drug Belsomra

The FDA said Wednesday that it approved Merck & Co.'s Belsomra (suvorexant) to treat people with insomnia, making it the first orexin receptor antagonist cleared for use in the country. The agency, which has previously rejected the drug on grounds that evidence did not support approval at higher doses, cleared Belsomra at dosage strengths ranging from 5 mg to 20 mg, lower than what Merck had originally sought to market.

After issuing a complete response letter for the therapy, the FDA directed the drugmaker to conduct a study assessing next-day driving performance in individuals who used the therapy, with the data identifying driving impairment in both males and females who received the 20-mg dose. Consequently, the regulator cautioned that patients using the highest dose should be advised against next-day driving and other activities requiring mental alertness, while those using lower doses should also be warned of the potential for next-day driving impairment due to individual variation in sensitivity to the drug. "Using the lowest effective dose can reduce the risk of side effects, such as next-morning drowsiness," remarked Ellis Unger, director of the Office of Drug Evaluation I in the FDA's Center for Drug Evaluation and Research.

The efficacy of Belsomra was supported by three trials involving more than 500 patients. In the studies, patients who received the drug fell asleep faster and spent less time awake throughout the night than those who received placebo. The FDA noted that because the therapy was not compared to other approved drugs, its safety and efficacy relative to other medicines are unknown.

Analysts project that Belsomra will generate revenue of $305 million by 2017, down from an earlier estimate of $516 million before the FDA declined to approve the therapy at higher doses. Meanwhile, the US Drug Enforcement Agency has proposed that the drug be classified as a Schedule IV product because of its potential for abuse and dependence.

Merck noted it expects the therapy to be available in the US in late 2014 or early 2015, once the Drug Enforcement Agency has made its decision on the scheduling of the drug.

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