The U.S. Food and Drug Administration agreed to consider the medicine daridorexant for approval, as Idorsia seeks to go up against a similar drug, Merck's Belsomra, which last year racked up $327 million in sales.

Clozel, along with his wife, Martine Clozel, Idorsia's chief science officer, founded Actelion two decades ago and turned it into Switzerland's most-successful homegrown biotech startup in recent years before unloading the business to Johnson & Johnson in 2017.

Now, he's trying for repeat success with Idorsia, with daridorexant the first and most-advanced of several pipeline drugs to enter the FDA's review process.

While Merck's sleep drug hasn't met analyst expectations for sales, Clozel is hoping that trials showing his medicine improved not only sleep but also daytime functioning -- and a price tag of roughly $5 per day-- gives it an edge.

"Should approval be received, the company anticipates launch in the U.S. in the first half of 2022," Idorsia said.

About 25 million Americans struggle with insomnia, whose symptoms include trouble sleeping that reduces people's ability to function during daytime waking hours.

Idorsia's medicine has also been submitted to the European Medicines Association earlier this month for review, though European doctors are seen as more sceptical of sleep drugs than their U.S. counterparts.

(Reporting by John Miller, editing by John Revill)