Nov 12 (Reuters) - Alkermes' ( ALKS ) experimental drug

significantly improved wakefulness and reduced excessive

sleepiness in patients with a rare sleep disorder in a mid-stage

study, it said on Wednesday.

The company was testing the drug, alixorexton, in

patients with narcolepsy type 2, a chronic neurological disorder

that disrupts the brain's ability to control sleep and wake

cycles.

The drug was generally well-tolerated, with most side

effects being mild to moderate, the company said.