US firm Arena Pharmaceuticals has initiated patient screening in a Phase I clinical trial of APD916, an oral drug that targets the histamine H3 receptor for the treatment of narcolepsy and cataplexy.

The randomised, double-blind, placebo-controlled Phase I trial will evaluate the safety, tolerability and pharmacokinetics of single-ascending doses of APD916 and will enroll up to 72 healthy adult volunteers.

Narcolepsy is a chronic neurological disorder caused by the brain’s inability to regulate sleep-wake cycles normally, where patients experience irresistible bouts of sleep.

Cataplexy, or the sudden loss of voluntary muscle tone triggered by emotional factors, is a symptom of narcolepsy and can cause a range of physical changes, from slurred speech to complete weakness of most muscles.