PD-L1 expression serves as a biomarker for potential response to which type of inhibitors?

• A. PD-1/PD-L1 inhibitors
• B. CTLA-4 inhibitors
• C. EGFR inhibitors
• D. PARP inhibitors

Answer: (A)

PD-L1 expression helps predict response to therapies that block the PD-1/PD-L1 immune checkpoint. When tumor cells express PD-L1, they can engage PD-1 on T cells to dampen the immune attack. Inhibitors that target this axis—PD-1 inhibitors or PD-L1 inhibitors—disrupt that interaction, reactivating T cells to attack the tumor. Tumors with higher PD-L1 expression are more likely to rely on this pathway, so they tend to respond better to these inhibitors. The other inhibitors target different pathways—CTLA-4 is a separate checkpoint, while EGFR inhibitors and PARP inhibitors act on distinct mechanisms—so PD-L1 levels specifically inform potential benefit from PD-1/PD-L1 blockade.