Pembrolizumab

What it is and how it works

Mechanism of Action Binding of the PD-1 ligands, PD-L1 and PD-L2, to the PD-1 receptor found on T cells, inhibits T cell proliferation and cytokine production. Upregulation of PD-1 ligands occurs in some tumors and signaling through this pathway can contribute to inhibition of active T-cell immune surveillance of tumors. Pembrolizumab is a monoclonal antibody that binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2, releasing PD-1 pathway-mediated inhibition of the immune response, including the anti-tumor immune response. In syngeneic mouse tumor models, blocking PD-1 activity resulted in decreased tumor growth.

Mechanism class: Programmed Death Receptor-1-directed Antibody Interactions

Indications

is a programmed death receptor-1 (PD-1)-blocking antibody indicated: Melanoma for the treatment of patients with unresectable or metastatic melanoma. for the adjuvant treatment of adult and pediatric (12 years and older) patients with Stage IIB, IIC, or III melanoma following complete resection. Non-Small Cell Lung Cancer (NSCLC) in combination with pemetrexed and platinum chemotherapy, as first-line treatment of patients with metastatic nonsquamous NSCLC, with no EGFR or ALK genomic tumor aberrations. in combination with carboplatin and either paclitaxel or paclitaxel protein-bound, as first-line treatment of patients with metastatic squamous NSCLC. as a single agent for the first-line treatment of patients with NSCLC expressing PD-L1 [Tumor Proportion Score (TPS) ≥1%] as determined by an FDA-authorized test, with no EGFR or ALK genomic tumor aberrations, and is: Stage III where patients are not candidates for surgical resection or definitive chemoradiation, or metastatic.

Dosage and administration (summary)

Melanoma: 200 mg every 3 weeks or 400 mg every 6 weeks; 2 mg/kg (up to 200 mg) every 3 weeks for pediatrics. NSCLC: 200 mg every 3 weeks or 400 mg every 6 weeks. MPM: 200 mg every 3 weeks or 400 mg every 6 weeks. HNSCC: 200 mg every 3 weeks or 400 mg every 6 weeks. cHL or PMBCL: 200 mg every 3 weeks or 400 mg every 6 weeks for adults; 2 mg/kg (up to 200 mg) every 3 weeks for pediatrics. Urothelial Cancer: 200 mg every 3 weeks or 400 mg every 6 weeks. MSI-H or dMMR Cancer: 200 mg every 3 weeks or 400 mg every 6 weeks for adults; 2 mg/kg (up to 200 mg) every 3 weeks for pediatrics. MSI-H or dMMR CRC: 200 mg every 3 weeks or 400 mg every 6 weeks.

Contraindications

None. None.

Warnings and precautions

Immune-Mediated Adverse Reactions Immune-mediated adverse reactions, which may be severe or fatal, can occur in any organ system or tissue, including the following: immune-mediated pneumonitis, immune-mediated colitis, immune-mediated hepatitis, immune-mediated endocrinopathies, immune-mediated nephritis with renal dysfunction, immune-mediated dermatologic adverse reactions, and solid organ transplant rejection. Monitor for early identification and management. Evaluate liver enzymes, creatinine, and thyroid function at baseline and periodically during treatment.

Pregnancy

Pregnancy Risk Summary Based on its mechanism of action, KEYTRUDA can cause fetal harm when administered to a pregnant woman. There are no available human data informing the risk of embryo-fetal toxicity.

Storage and supply

Store vials under refrigeration at 2°C to 8°C (36°F to 46°F) in original carton to protect from light. Do not freeze. Do not shake.

Source: Pembrolizumab (Keytruda) — US FDA prescribing information, 2026-07-10, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.