Pembrolizumab
Therapeutic class: Antineoplastic agent
Pharmacologic class: Immune Checkpoint Inhibitor (PD-1 Inhibitor)
Mechanism of Action
Pembrolizumab is a humanized monoclonal antibody that binds to the programmed death-1 (PD-1) receptor on T-cells. By blocking the interaction between PD-1 and its ligands (PD-L1 and PD-L2), pembrolizumab enhances the immune system’s ability to recognize and destroy cancer cells. This results in an increased anti-tumour immune response.
Formulations
Injection (Keytruda): 100 mg/4 mL single-dose vial
Route of administration: Intravenous infusion
Indications
| S.No | Labelled Indications | Dosing & frequency |
|---|---|---|
| 1. | Gastric cancer | 200 mg once every 3 weeks until disease progression, unacceptable toxicity, or (in patients without disease progression) for up to 24 months. |
| 2. | Head and neck squamous cell cancer | |
| 3. | Hodgkin’s Lymphoma, classical | |
| 4. | Melanoma | |
| 5. | Microsatellite instability-high cancer | |
| 6. | Non-small cell lung cancer (metastatic) | |
| 7. | Urothelial carcinoma | |
| 8. | Non-small cell lung cancer (metastatic, non-squamous) | 200 mg once every 3 weeks (in combination with pemetrexed and carboplatin) for 4 cycles, followed by pembrolizumab monotherapy of 200 mg once every 3 weeks |
Administration
IV: Infuse over 30 minutes through a 0.2 to 5 micron sterile, non-pyrogenic, low-protein binding inline or add-on filter. Do not infuse other medications through the same infusion line.
Non-small cell lung cancer (metastatic): When administered in combination with chemotherapy (pemetrexed and carboplatin), pembrolizumab should be administered prior to chemotherapy if scheduled to be administered on the same day.
Dose Adjustment
Hepatotoxicity: Stop temporarily if AST/ALT >3–5× Upper Limit of Normal ( ULN) or Bilirubin >1.5–3× ULN and give steroids; restart after recovery but stop permanently if AST/ALT >5× ULN, bilirubin >3× ULN, or if baseline liver enzymes increase ≥50% and persist for 1 week.
Global efficacy
Globally, pembrolizumab helps about 40% of cancer patients who show good response, and improves long-term survival, with around 20–30% of patients living for 5 years or more with some major cancers.
Side effects
Pembrolizumab causes immune-related side effects such as thyroid problems, colitis, hepatitis and pneumonitis due to immune overactivation.
