Pembrolizumab (Keytruda) for Stage IV Cancer
Also known as: Keytruda, MK-3475
The most widely prescribed checkpoint inhibitor, pembrolizumab has revolutionized treatment across 30+ cancer types by unleashing anti-tumor immunity.
Mechanism of Action
Pembrolizumab is a humanized IgG4 monoclonal antibody that blocks PD-1 receptor on T cells, preventing engagement with PD-L1/PD-L2 ligands on tumor cells. This removes the 'immune brake,' restoring cytotoxic T cell function against tumor-associated antigens. Response correlates with PD-L1 expression, tumor mutational burden, and microsatellite instability.
General mechanism: Anti-PD-1 monoclonal antibody. Blocks immune checkpoint to restore T cell anti-tumor activity.
Current Evidence
Landmark trials across NSCLC, melanoma, head and neck, urothelial, gastric, cervical, and MSI-high cancers show durable responses in 20-40% of patients. KEYNOTE program has generated the largest immunotherapy dataset. Combination with chemotherapy improves first-line response rates.
Clinical Status: FDA-approved for 30+ indications. First-line standard of care for PD-L1+ NSCLC, melanoma, and many others. Over $25B annual revenue reflects clinical impact.
Safety Profile
Immune-related adverse events (colitis, pneumonitis, hepatitis, endocrinopathies) in 15-30% of patients. Most manageable with corticosteroids. Rare but serious: myocarditis, encephalitis.
Key Research Questions
- How can biomarker-driven selection improve response rates beyond PD-L1/TMB?
- What combinations (Anktiva, fenbendazole, metabolic interventions) may overcome primary resistance?
- Can liquid biopsy monitoring predict optimal treatment duration?