Pembrolizumab is used in multiple solid tumors including lung cancer. Its mechanism is:
- A Anti-PD-1 antibody blocking interaction between tumor PD-L1 and T-cell PD-1, restoring anti-tumor T-cell activity ✓
- B Direct killing of cancer cells through complement-dependent cytotoxicity (CDC) after binding PD-1 on tumor cells
- C Blocking CTLA-4 on regulatory T cells, reducing immunosuppression in the tumor microenvironment
- D Delivering a cytotoxic payload to PD-1-expressing tumor-infiltrating lymphocytes via antibody-drug conjugate
Correct answer: A. Anti-PD-1 antibody blocking interaction between tumor PD-L1 and T-cell PD-1, restoring anti-tumor T-cell activity
Explanation
Pembrolizumab is a humanized anti-PD-1 monoclonal antibody that blocks the interaction between PD-1 (programmed death receptor-1) on T cells and its ligands PD-L1/PD-L2 expressed on tumor cells. Tumors exploit this checkpoint to suppress cytotoxic T-cell responses. By blocking this interaction, pembrolizumab restores T-cell activation and anti-tumor immune activity. Ipilimumab is the anti-CTLA-4 checkpoint inhibitor; atezolizumab/durvalumab target PD-L1 directly.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.