What Pembrolizumab Targets
Pembrolizumab (Keytruda) targets PD-1, an immune checkpoint receptor on T cells that tumors exploit to evade immune detection by binding to PD-L1 or PD-L2 ligands.[1]
How PD-1 Blockade Works
By binding PD-1, pembrolizumab prevents its interaction with PD-L1/PD-L2, reactivating T cells to attack cancer cells. This mechanism drives its approval in over 30 indications, including melanoma, lung cancer, and MSI-high tumors.[1][2]
Comparison with Other Checkpoint Inhibitors
Pembrolizumab differs from CTLA-4 inhibitors like ipilimumab (Yervoy), which block an earlier T-cell activation step. PD-1 rivals include nivolumab (Opdivo) and cemiplimab (Libtayo), all targeting the same receptor but with varying affinities and indications.[2]
Common Cancers Treated via PD-1 Inhibition
Approved for non-small cell lung cancer, head and neck squamous cell carcinoma, Hodgkin lymphoma, and more, often combined with chemotherapy or other immunotherapies.[1]
Key Side Effects from PD-1 Targeting
Immune-related adverse events like colitis, pneumonitis, and endocrinopathies occur in 10-20% of patients, due to unchecked T-cell activity.[2]
[1]: FDA Label for Keytruda
[2]: NEJM Review on PD-1 Inhibitors