AIDS patients expecting approval of a new HIV-associated diarrhea treatment in June must wait at least another three months for a decision.

Salix Pharmaceuticals (Nasdaq: SLXP) had been scheduled for a June 5 decision date on its experimental diarrhea treatment crofelemer. But the Raleigh company said it has been notified by the U.S. Food and Drug Administration that regulators need more time to review the submission. The new Prescription Drug User Fee Act (PDUFA) date is Sept. 5.

There’s no indication that there is a problem with the application and the FDA did not request any additional studies. But it’s the second extension Salix has received in the last week. The FDA last week notified the company of a three-month extension to review an expanded indication for constipation treatment Relistor.

Crofelemer already had some regulatory roadblocks removed to speed its pathway to approval. HIV-associated diarrhea is an unmet medical need and the FDA gave the drug candidate priority review and fast-track status. The clinical trials were done under a special protocol assessment to further expedite the regulatory process. But the speed of that development became a point of contention between Salix and Napo Pharmaceuticals, the California biotechnology company that licensed crofelemer to Salix in 2008.

Napo last year sued Salix and claimed its partner breached the contract by failing to file a new drug application for crofelemer, even with positive phase 3 clinical trial data in hand. Last November, Napo terminated the contract and claimed that the alleged contract breach provided the grounds to do so. Napo claims that Salix’s contract breach means crofelemer’s rights revert back to Napo. Salix has repeatedly said that Napo’s case and its claims are groundless, and without merit. The case is still pending in court.

Meanwhile, Napo is acting as if crofelemer belongs entirely to the California company. Napo CEO Lisa Conte told the Burrill Report last month that her company is looking ahead to plans to commercialize crofelemer in other countries and develop the drug for other gastrointestinal indications. The company is also studying the compound for pediatric diarrhea and diarrhea predominant irritable bowel syndrome. And not just in humans. The company has started developing veterinary applications for crofelemer.

“In fact, a lot of the understanding of the disease’s state of watery diarrhea was learned from animals in the first place,” she said.