Vanda Pharmaceuticals ( VNDA) brings its "sleeping pill for the blind" drug tasimelteon in front of an FDA advisory panel today. Tasimelteon is a form of melatonin designed to regulate the 24-hour sleep-wake cycle, also known as circadian rhythm. For some people who are totally blind, having no light perception at all knocks the normal, 24-hour circadian rhythm off kilter. Their sleep patterns start to shift -- less sleep at night, more during the day. The medical term for this condition is "non-24 sleep-wake disorder" (non-24) and there are no drugs approved to treat it. Based on results from two phase III studies, Vanda believes tasimelteon is the first drug shown to "entrain" non-24 patients back into a normal circadian rhythm. Tasimelteon also improves sleep performance, the company says. Experts participating in Thursday's FDA advisory panel will review the efficacy and safety data on tasimelteon and vote on whether or not the drug should be approved. -- Reported by Adam Feuerstein in Boston. Follow Adam Feuerstein on Twitter.