On October 2, the Food and Drug Administration (FDA) granted accelerated approval for pembrolizumab (Keytruda®) to treat patients with metastatic non-small cell lung cancer (NSCLC) whose tumors express a protein called PD-L1 and whose cancers progressed after platinum-based chemotherapy.
Pembrolizumab targets a protein on immune cells called PD-1, one of a family of so-called checkpoint proteins that can restrain the immune response. When PD-1 ligand, or PD-L1, on tumor cells binds to PD-1 on immune system cells, the PD-1 signaling pathway is activated, inhibiting an immune response. By blocking this interaction, pembrolizumab allows the immune system to recognize and attack tumor cells.
The FDA approval was based on a subgroup analysis of 61 patients in a large clinical trial whose tumors overexpressed PD-L1. After treatment with pembrolizumab, tumor size decreased in 24 patients (41 percent) and the effect lasted up to 9.1 months.
The approval of pembrolizumab for this indication requires the use of a companion diagnostic test called PD-L1 IHC 22C3 pharmDx, which is used to measure the PD-L1 expression levels of a patient’s tumor.
