** Shares of rare neurological disease-focused pharma company Harmony Biosciences HRMY.O down 5.9% at $36.77

** Company says it has received "refusal to file" letter from the U.S. FDA for its drug pitolisant, which is being developed for the treatment of excessive daytime sleepiness (EDS) in adult patients with idiopathic hypersomnia, a type of sleep disorder

** The drug is marketed as Wakix in the U.S. for the treatment of EDS or cataplexy in adult patients with narcolepsy, and to treat EDS in children 6 years of age and older with narcolepsy

** The FDA's refusal to file letter notifies the company that its application is incomplete for a substantive review

** This presents a short-term setback for the expansion in idiopathic hypersomnia, says brokerage Oppenheimer

** Idiopathic hypersomnia is a condition that causes people to be very sleepy during the day even after a full night of sleep

** Stock has risen ~15% in the last 12 months

(Reporting by Siddhi Mahatole)

((Siddhiprabhanjan.mahatole@thomsonreuters.com))