Inspire Pharmaceuticals must perform an additional clinical study for its proposed dry eye drug, the company was told on Thursday by the Food and Drug Administration.

Inspire stock (Nasdaq: ISPH) dropped Friday morning on the news but rallied to trade up 46 cents at $13.01 in mid-afternoon trading.

The FDA notified Inspire on Dec. 19 that it had questions about the drug, known as diquafosol.

“We now have clarity on what we need to do in moving forward toward product approval and have already begun plans for an additional study,” stated Christy L. Shaffer, chief executive officer of Inspire, in a statement. “We plan to initiate a new study as quickly as possible, while taking the time needed to involve the FDA in review of the study protocol to ensure that the study design is acceptable. We believe that our experience, and that of our partner, Allergan, will be valuable in designing a study that is optimized for success. I will be providing an update on our other programs in development as well as our launch of Elestat(TM) in our conference call this morning.”

Inspire requested a meeting with the FDA after getting the letter. Inspire then submitted additional data that it felt addressed the FDA’s concerns.

“While we have demonstrated efficacy in one of the pivotal trials submitted as part of the original New Drug Application (NDA), the FDA requires that an additional clinical study be conducted to confirm or replicate this efficacy,” Inspire said in a statement. Among the information were results of a Phase III study (03-108) that was completed after Inspire had submitted its NDA. “The FDA indicated that the findings from study 108 are not sufficient to address the requirement for an additional clinical study as stated in the approvable letter,” Inspire added.

Inspire: www.inspirepharm.com