By Lisa Seachrist

Washington Editor

Orphan Medical Inc.'s narcolepsy drug, Xyrem (sodium oxybate) in oral solution, proved an effective treatment in two pivotal Phase II clinical studies.

The Minneapolis-based company's drug effectively combated the two primary symptoms of narcolepsy: cataplexy, the sudden loss of muscle control precipitated by emotion, and excessive daytime sleepiness (EDS). Should the product be approved it would be the first therapy to address both primary symptoms of narcolepsy.

"We knew from previous data that the drug should work on cataplexy," said Orphan Medical CEO John Bullion. "We were pleasantly surprised to see the positive effects on daytime sleepiness."

The company intends to file an NDA for the drug, which has orphan drug status with FDA and qualifies for expedited review, in the second half of this year. The agency has already said the data from an additional Phase III study won't be required for an NDA submission; however, that study would support additional label claims.

Sodium oxybate, as a chemical compound, has been around for quite some time. It is known to induce sleep. Orphan Medical, in conjunction with the FDA's orphan drug division, decided to explore the drug's efficacy in narcolepsy.

Narcoleptics suffer from a dissociation between their deep sleep and rapid-eye-movement sleep. As a result, they will fall asleep many times throughout the day. Xyrem works by "gluing" the two types of sleep back together, allowing the patient to fully rest, Bullion said.

The results of a 136-patient placebo-controlled, double-blind study showed that patients receiving the highest dose of Xyrem (9 grams) experienced 68.6 percent fewer attacks of cataplexy than their placebo counterparts. After completion of that study, 118 patients agreed to continue on Xyrem. The study investigators established the effective dose for each individual patient and monitored excessive daytime sleepiness. The 9-gram dose of the drug markedly reduced daytime sleepiness - some patients even obtained levels of sleepiness considered "normal."

Because the chemical compound isn't novel, there is no inherent proprietary value for Xyrem. Bullion noted the company has reformulated the drug and filed for use patents "to carve out a proprietary position."

Orphan Medical's stock (NASDAQ:ORPH) closed Wednesday at $6.562, down 81.25 cents.