California-based biotech Gilead Sciences reported it had received a complete response letter from the U.S. health regulating agency for its NDA for its investigational treatment for cystic fibrosis Aztreonam Lysine for inhalation.

In the letter, the FDA informed the company that it cannot approve the new drug application in its current form and that an additional clinical study will be required.

Gilead´s chairman and CEO John Martin said the FDA has not raised any significant concerns regarding the safety of Aztreonam Lysine, and that the company plans to continue talks with the agency to determine if further analyses of existing data could lead to approval, or if it needs to conduct the additional study as suggested.

Gilead submitted its drug application on November 16, 2007, after having been granted the status of ‘orphan drug’ by both the FDA and the European Medicines Agency (EMEA).

According to market analysts, once the product is approved it could reach sales of between $ 150 and $ 200 million dollars yearly.

Currently there are two products on the market for this condition: Genentech/Roche Holding´s Pulmozyme, and Novartis´ TOBI.

Marketing applications for Aztreonam Lysine for inhalation are under review by regulatory agencies in the EU, Australia, Switzerland, Turkey and Canada.