[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Immune checkpoint inhibitors](https://durgical.com/en/pharmacology/classes/immune-checkpoint-inhibitors/) › Pembrolizumab # Pembrolizumab ## Immune checkpoint inhibitors? Immune checkpoint inhibitors ## High alert? An error with this medicine can cause serious harm: double checks and protocols are used. An anti-PD-1 antibody that reactivates T cells against many cancers, including melanoma, lung cancer and any tumour with mismatch-repair deficiency. Updated Nov 1, 2026 Also called: anti-PD-1 antibody ## Quick facts **Group** [Immune checkpoint inhibitors](https://durgical.com/en/pharmacology/classes/immune-checkpoint-inhibitors/) **Target** Programmed cell death protein 1 (PD-1) on T cells **Used for** Melanoma · Non-small cell lung cancer · Urothelial **Key effects** Fatigue · Rash and itching · Diarrhoea **Monitor** Thyroid function · Glucose · Stool frequency **ATC** L01FF02 No doses: the clinician sets them by the current guideline. On this page - The basics Mechanism of action - Indications - Adverse effects - Pharmacokinetics - Memory aid - Clinical What the labels mean - Safety Contraindications - Key interactions - What is monitored - Administration and safety - Pregnancy and breastfeeding - Nursing care - Study Test yourself - Connections Connections ## Mechanism of action ◎**Programmed cell death protein 1 (PD-1) on T cells**Pembrolizumab ⓘ The crystal shows the extracellular domain of human PD-1 bound by the pembrolizumab Fab, which covers the surface PD-L1 would use. **Target in 3D:** Programmed cell death protein 1 (PD-1) on T cells. PDB structure 5GGS (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/5GGS) · Drag to rotate · pinch to zoom Pembrolizumab is a humanised IgG4 antibody that binds PD-1 on activated T cells and prevents it from engaging PD-L1 and PD-L2. Tumours that display PD-L1 use this pathway to exhaust the T cells that infiltrate them; blocking it restores T-cell activity, cytokine release and killing of tumour cells. Tumours with many mutations (for example mismatch-repair deficient or MSI-H) make more abnormal proteins for T cells to recognise and respond more often. - Tumour PD-L1 switches off PD-1-positive T cells - Pembrolizumab binds PD-1 and blocks PD-L1/PD-L2 - T cells regain activity inside the tumour - Tumour cells are killed; autoimmunity is possible ## Indications - Melanoma, advanced or after resection of high-risk disease. [Melanoma →](https://durgical.com/en/conditions/melanoma/) - Non-small cell lung cancer, alone (high PD-L1) or with chemotherapy. [Lung cancer →](https://durgical.com/en/conditions/lung-cancer/) - Head and neck squamous cell carcinoma. [Head and neck squamous cell carcinoma (oral cavity and oropharynx, HPV) →](https://durgical.com/en/conditions/head-and-neck-squamous-cell-carcinoma/) - Urothelial (bladder) cancer. [Bladder cancer →](https://durgical.com/en/conditions/bladder-cancer/) - Classical Hodgkin lymphoma. [Hodgkin lymphoma →](https://durgical.com/en/conditions/hodgkin-lymphoma/) - Merkel cell carcinoma. [Merkel cell carcinoma →](https://durgical.com/en/conditions/merkel-cell-carcinoma/) - Triple-negative breast cancer, with chemotherapy. [Breast cancer →](https://durgical.com/en/conditions/breast-cancer/) - Any solid tumour with mismatch-repair deficiency or high microsatellite instability (tissue-agnostic), including colorectal cancer. [Colorectal cancer →](https://durgical.com/en/conditions/colorectal-cancer/) ## Adverse effects ### Common - Fatigue - Rash and itching - Diarrhoea, nausea, decreased appetite - Cough and breathlessness - Muscle and joint pain - Thyroid dysfunction ### Serious (rare, important) - Immune-mediated pneumonitis - Immune-mediated colitis - Immune-mediated hepatitis - Endocrinopathies: hypophysitis, thyroiditis, adrenal insufficiency, type 1 diabetes - Immune-mediated nephritis - Severe skin reactions - Myocarditis, myositis and neurological reactions (myasthenia, Guillain-Barré syndrome) - Infusion reactions ## Contraindications - Previous severe immune-mediated reaction to a checkpoint inhibitor (generally not re-exposed) - Caution: active autoimmune disease, organ or allogeneic stem-cell transplant ## Key interactions **Systemic corticosteroids and other immunosuppressants** Used to treat moderate to severe immune-mediated reactions; they damp the immune response. **Allogeneic stem-cell transplant before or after treatment** A recognised caution: the stronger immune response can cause serious transplant complications, so the team weighs it before use. ## What is monitored - Thyroid function (TSH) before starting and regularly - Liver tests and creatinine before each dose - Glucose; cortisol if fatigue or low blood pressure - Stool frequency, cough and breathlessness at each visit - Signs of myocarditis (chest pain, palpitations) and muscle weakness ## Administration and safety - Intravenous infusion only, never as a push or bolus, through a line as the product instructions specify. - Look-alike names: the -mab checkpoint inhibitors (nivolumab, pembrolizumab, atezolizumab, cemiplimab, ipilimumab) are checked by full name; products combined with hyaluronidase for subcutaneous use are not interchangeable with the intravenous ones. - Watch for infusion reactions (chills, fever, rash, breathlessness) during the infusion. ## Pregnancy and breastfeeding Blocking PD-1/PD-L1 or CTLA-4 can harm the fetus (IgG antibodies cross the placenta); effective contraception is used during treatment and for months after, and breastfeeding is avoided. ## Nursing care - Before each dose, ask about diarrhoea, cough, rash, headache, fatigue, dizziness, thirst or passing more urine, and review thyroid, liver, kidney and glucose results. - Teach the patient that side effects can start weeks or months after a dose, even after treatment ends, and must be reported early. - Teaching: report diarrhoea or blood in the stool, new cough or breathlessness, yellow skin, severe headache, extreme tiredness, chest pain or muscle weakness at once. - Make sure the patient carries information that they receive immunotherapy, for any emergency visit. ## Pharmacokinetics **Absorption** Intravenous infusion. **Elimination** Broken down like natural IgG. **Half-life** About 26 days. ## Memory aid «PD-1 = Please Don't stop the T cell»: pembrolizumab takes the brake off. Any organ can become inflamed (the «-itis» list): colitis, pneumonitis, hepatitis, thyroiditis, hypophysitis. ## Test yourself Think of the answer, then tap the question to see it. ## What does pembrolizumab bind, and what does it block? PD-1 on T cells; it blocks its interaction with PD-L1 and PD-L2. ## Which tumour feature makes pembrolizumab usable regardless of the organ of origin? Mismatch-repair deficiency or high microsatellite instability (MSI-H). ## A patient on pembrolizumab has fatigue, low blood pressure and low sodium. Which immune-related problem should be considered? Adrenal insufficiency, primary or from hypophysitis. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/pembrolizumab/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## What the labels mean **High alert** An error with this medicine can cause serious harm: double checks and protocols are used. ## Connections ## Related drugs 4 - [Nivolumab](https://durgical.com/en/pharmacology/nivolumab/) - [Cemiplimab](https://durgical.com/en/pharmacology/cemiplimab/) - [Atezolizumab](https://durgical.com/en/pharmacology/atezolizumab/) - [Ipilimumab](https://durgical.com/en/pharmacology/ipilimumab/) ## Related conditions 8 - [Melanoma](https://durgical.com/en/conditions/melanoma/) - [Lung cancer](https://durgical.com/en/conditions/lung-cancer/) - [Head and neck squamous cell carcinoma (oral cavity and oropharynx, HPV)](https://durgical.com/en/conditions/head-and-neck-squamous-cell-carcinoma/) - [Bladder cancer](https://durgical.com/en/conditions/bladder-cancer/) - [Hodgkin lymphoma](https://durgical.com/en/conditions/hodgkin-lymphoma/) - [Merkel cell carcinoma](https://durgical.com/en/conditions/merkel-cell-carcinoma/) - [Breast cancer](https://durgical.com/en/conditions/breast-cancer/) - [Colorectal cancer](https://durgical.com/en/conditions/colorectal-cancer/) [← Back to the class: Immune checkpoint inhibitors](https://durgical.com/en/pharmacology/classes/immune-checkpoint-inhibitors/) Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given. Sources: [Pembrolizumab Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a614048.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01FF02) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/pembrolizumab/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/pembrolizumab/