Biopharmaceutical development firm Trimeris faces a lawsuit over the HIV drug it developed called Fuzeon.

In a Securities and Exchange Commission filing on Tuesday, Trimeris (Nasdaq: TRMS) said it had been sued by Novartis. Roche, Trimeris’ partner in developing and selling Fuzeon, is also included in the suit.

Novartis is alleging patent infringement. According to Trimeris, Novartis received the patent at the center of the case, about one month ago.

Fuzeon was approved for sale in 2003.