According to Reuters, Gilead Sciences Inc plans to appeal a request by the U.S. Food and Drug Administration for an additional clinical study of the company's experimental cystic fibrosis drug, aztreonam lysine.

Gilead spokeswoman, Cara Miller, told the agency that "Gilead intends to appeal the decision with the FDA on the basis of what we believe is the strength of the efficacy and safety of aztreonam lysine and of its overall clinical profile as outlined in our new drug application."

Gilead applied for approval of the drug to treat lung infections associated with cystic fibrosis and, at the time, the drugmaker said the FDA did not raise any significant concerns regarding the drug’s safety.

Analysts at Oppenheimer estimated that sales of the drug would eventually reach $105 million in 2010, rising to $205 million in 2012.