GAITHERSBURG, Md., Dec 10 - A U.S. Food and Drug Administration advisory panel on Thursday said it found Gilead Sciences Inc's (GILD.O) aztreonam was an effective new treatment for life-threatening lung infections in cystic fibrosis patients.

The drug won marketing approval in September in Europe and Canada under the brand name Cayston.

The anti-infective drugs panel's finding on a vote of 15-2 that the drug is safe and effective serves as a recommendation that the FDA approve the drug. While the agency is not required to follow an advisory panel's recommendation, the panel's opinion carries great weight.

The panel said the safety and efficacy involved a 75 milligram dose administered three times a day to aid in improvement of respiratory symptoms and lung function.

Cystic fibrosis is an inherited chronic disease that affects the lungs and digestive systems of about 70,000 people worldwide, according to the Cystic Fibrosis Foundation. A defective gene and the protein it produces cause the body to produce thick, sticky mucus that clogs the lungs, leads to life-threatening lung infections and obstructs the pancreas.

Azteronam is designed to treat lung infections in these patients caused by common pseudomonas aeruginosa bacteria, for which there are few inhaled antibiotics available.

Aztreonam sales could reach at least $200 million globally by 2015, according to Summer Street Research analyst Carol Werther. The medicine could strengthen Gilead's pulmonary franchise but pales in importance when compared with its stable of HIV drugs, Werther said.

Dr. Bruce Marshall of the Cystic Fibrosis Foundation urged FDA to approve the drug swiftly and told the panel: There is a desperate need for additional inhaled antibiotics.

Drug resistance is a complication in treatment for these patients.

While cystic fibrosis patients live longer now than 20 years ago, it is still a devastating disease, Marshall said. The average age at death is 26 years.

Gilead shares were up 0.3 percent to $46.15 in afternoon trading. (Writing by Jackie Frank, editing by Gerald E. McCormick)