Axsome Therapeutics Inc. said the U.S. Food and Drug Administration granted its drug AXS-12 an orphan drug status for treating narcolepsy.

Narcolepsy is a serious, debilitating condition that causes daytime sleepiness and physical collapse while being conscious.

The New York-based drugmaker plans to initiate a mid-stage study of the drug during the fourth quarter and expects to report its outcome in the first half of 2019.

The orphan drug status is designed for therapies targeting rare diseases that affect less than 200,000 people in the U.S. The designation will also provide seven years of market exclusivity if the drug is approved in the U.S.