Depomed Inc filed a lawsuit against U.S. health regulators, seeking market exclusivity for its shingles pain drug, which was designated as an orphan drug.
The U.S. Food and Drug Administration, which approved Gralise in January 2011, had granted orphan-drug designation to it, but not the market exclusivity that goes with the status.
An orphan drug status, granted to drugs treating fewer than 200,000 patients, gives the approved product seven years of marketing exclusivity from its approval date.
Gralise accounted for $3.2 million, or 23 percent of Depomed's sales in its latest quarter.
Menlo Park, California-based Depomed shares, which have slipped 7 percent since Gralise was approved, closed at $5.77 on Tuesday on the Nasdaq.
(Reporting by Vidya P L Nathan; Editing by Don Sebastian)