The U.S. Food and Drug Administration approved Merck & Co.'s Keytruda for the treatment of the most common form of lung cancer.
Keytruda can be used in patients with non-small-cell lung cancer whose tumors contain a certain level of a protein known as PD-L1, and whose disease continued to worsen after the patient received chemotherapy or other drugs.
The regulator also approved a companion diagnostic developed by Dako North America Inc. to test for PD-L1, to screen for patients who should receive Merck's Keytruda.
A study found that Keytruda worked better in lung-cancer patients with higher levels of PD-L1 than in patients with lower or undetectable levels.
Merck estimates roughly 25% of all non-small-cell lung-cancer patients have PD-L1 levels that would make them eligible for Keytruda treatment.