Recently, Agilent Technologies' Dako said that the US Food and Drug Administration has approved the firm's companion diagnostic assay in connection with a simultaneous approval for Merck's non-small lung cancer drug.

The companion diagnostic called PD-L1 IHC 22C3 pharmDx is used to determine whether a patient with advanced NSCLC is likely to respond to Merck's anti-PD-1 therapy Keytruda (pembrolizumab), which was approved by the FDA for treating patients with metastatic NSCLC whose tumors expressed PD-L1 and whose disease has progressed on or after platinum-containing chemotherapy.

Dako's test, developed in partnership with Merck, will be used to determine whether the patient's tumor expresses the PD-L1 protein. Dako said that it hopes to gain regulatory clearance for the assay in Canada, Europe, and other jurisdictions next year.

"The approval of the first PD-L1 diagnostic has the potential to provide information that will help guide treatment decisions for many patients," Roger Dansey, senior vice president at Merck Research Laboratories, said in a statement. Dako and Merck announced a deal to develop a CDx for Keytruda in May 2014.

Separately, Labortory Corporation and Quest Diagnostics each said that they will provide clinical laboratory testing using PD-L1 IHC 22C3 pharmDx. Physicians are able to order the test from either firms starting today. Also, GE Healthcare's Clarient is offering the test.