[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › Immune checkpoint inhibitors # Immune checkpoint inhibitors Antibodies that release the brakes on T cells (PD-1, PD-L1, CTLA-4) so the immune system attacks the cancer; the price is autoimmune-type side effects. Updated Nov 1, 2026 ## What they are Intravenous antibodies against PD-1 (pembrolizumab, nivolumab, cemiplimab), PD-L1 (atezolizumab) and CTLA-4 (ipilimumab). They are used in melanoma, lung cancer, kidney cancer, head and neck cancer, Hodgkin lymphoma and tumours with mismatch-repair deficiency, among others. ## Mechanism of action T cells carry inhibitory receptors that normally prevent autoimmunity. Tumours exploit them: PD-L1 on tumour cells switches off PD-1-positive T cells inside the tumour, and CTLA-4 limits T-cell priming in lymph nodes. Blocking these checkpoints lets T cells stay active and kill tumour cells, but it can also break tolerance to normal tissues. Target: T-cell checkpoints PD-1, PD-L1 and CTLA-4 ## Key points - Immune-related adverse events can hit any organ: skin (rash, itching, vitiligo), colon (diarrhoea, colitis), liver (hepatitis), lung (pneumonitis), glands (thyroiditis, hypophysitis, adrenal insufficiency, type 1 diabetes), kidney, nerves and heart. - Moderate to severe reactions: the drug is withheld and systemic corticosteroids are given; severe ones lead to permanent discontinuation. - Anti-CTLA-4 (ipilimumab) causes more immune toxicity than anti-PD-1; the ipilimumab–nivolumab combination causes the most, including rare fatal myocarditis. - Thyroid function, liver tests, glucose and creatinine are checked before each cycle. - Responses can take months and tumours may look bigger at first because of inflammation. ## Drugs in this class - [**Pembrolizumab** An anti-PD-1 antibody that reactivates T cells against many cancers, including melanoma, lung cancer and any tumour… Programmed cell death protein 1 (PD-1) on T cells](https://durgical.com/en/pharmacology/pembrolizumab/) - [**Nivolumab** An anti-PD-1 antibody used in melanoma, lung, kidney, head and neck and liver cancer and Hodgkin lymphoma, alone or… Programmed cell death protein 1 (PD-1) on T cells](https://durgical.com/en/pharmacology/nivolumab/) - [**Ipilimumab** Anti-CTLA-4 antibody for melanoma, often with nivolumab. It causes more immune toxicity (colitis, hypophysitis) than… Cytotoxic T-lymphocyte antigen 4 (CTLA-4)](https://durgical.com/en/pharmacology/ipilimumab/) - [**Atezolizumab** An anti-PD-L1 antibody for lung cancer (including small cell), liver cancer with bevacizumab, and melanoma; adverse… Programmed death-ligand 1 (PD-L1) on tumour and immune cells](https://durgical.com/en/pharmacology/atezolizumab/) - [**Cemiplimab** An anti-PD-1 antibody for advanced cutaneous squamous cell carcinoma, basal cell carcinoma after hedgehog inhibitors… Programmed cell death protein 1 (PD-1) on T cells](https://durgical.com/en/pharmacology/cemiplimab/) - [**Nivolumab/relatlimab** Two checkpoint antibodies in one infusion: nivolumab blocks PD-1, relatlimab blocks LAG-3. Used in advanced melanoma… PD-1 (nivolumab) and LAG-3 (relatlimab) on T cells](https://durgical.com/en/pharmacology/nivolumab-relatlimab/) - [**Durvalumab** Human anti-PD-L1 antibody that releases the brake on T cells. For lung, bladder, biliary, liver and other cancers… Programmed death-ligand 1 (PD-L1) on tumour and immune cells](https://durgical.com/en/pharmacology/durvalumab/) ## Others in the class - durvalumab - avelumab - dostarlimab - tremelimumab ## Test yourself Think of the answer, then tap the question to see it. ## A patient on pembrolizumab develops several watery stools a day with abdominal pain. What is the likely cause and the key treatment? Immune-mediated colitis; the drug is withheld and systemic corticosteroids are started according to severity. ## Where does CTLA-4 blockade act, compared with PD-1 blockade? CTLA-4 blockade boosts T-cell priming in lymph nodes; PD-1/PD-L1 blockade reactivates T cells inside the tumour. ## Which endocrine problems should be looked for during checkpoint inhibitor treatment? Hypo- or hyperthyroidism, hypophysitis, adrenal insufficiency and type 1 diabetes. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/classes/immune-checkpoint-inhibitors/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) [← All of pharmacology](https://durgical.com/en/pharmacology/) 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); [Ipilimumab Injection: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a611023.html) (MedlinePlus (U.S. National Library of Medicine), 2023); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01FF) (WHO Collaborating Centre for Drug Statistics Methodology, 2026). ## **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/classes/immune-checkpoint-inhibitors/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/immune-checkpoint-inhibitors/