The U.S. Food and Drug Administration expanded its approval of Agilent Technologies Inc.'s diagnostic test PD-L1 IHC 22C3 pharmDx to identify triple-negative breast cancer.

Specifically, the U.S. regulator approved the test to help diagnose triple-negative breast cancer patients who may be eligible for treatment with Merck & Co. Inc.'s Keytruda.

Keytruda is a checkpoint inhibitor — a tumor-targeting drug that blocks the PD-1 arm on healthy cells from linking up with a partner arm on the surface of cancer cells to spread the disease.

Earlier in November, Keytruda was approved by the U.S. FDA for treating patients with triple-negative breast cancer whose disease had returned or spread to other parts of the body and whose tumors express a protein known as PD-L1.

Agilent's diagnostic test is now approved by the FDA for identifying patients with seven types of cancer for treatment with Keytruda, or pembrolizumab. Santa Clara, Calif.-based Agilent developed PD-L1 IHC 22C3 pharmDx in partnership with Kenilworth, N.J.-based Merck & Co.

About 276,480 new cases of breast cancer are estimated to be diagnosed in the U.S. in 2020. About 10% of such diagnoses are triple-negative breast cancer.