FILE PHOTO: A man walks past Pfizer's world headquarters in New York April 28, 2014. REUTERS/Andrew Kelly/File Photo

(Reuters) - Pfizer Inc said on Friday the U.S. Food and Drug Administration has approved its lung-cancer treatment for patients with a specific gene mutation who had been previously treated for an aggressive form of the disease.

The treatment, Lorbrena, is designed to treat advanced non-small cell lung cancer in patients with a mutation of the ALK gene, who have relapsed after being treated with ALK inhibitors, such as Pfizer’s Xalkori.

While many patients respond to initial ALK inhibitor therapy, they typically eventually experience disease progression and are faced with limited options due to resistance to existing treatments.

Non-small cell lung cancer (NSCLC) accounts for about 85 percent of lung cancer cases and remains difficult to treat. About 3 to 5 percent of NSCLC tumors are ALK-positive, and is often found in non-smokers.

Lorbrena, known chemically as lorlatinib, received an accelerated approval, Pfizer said. Its continued approval may depend on verification of clinical benefit in a confirmatory trial.