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# BTK inhibitors

Oral drugs that switch off Bruton tyrosine kinase, the hub of B-cell receptor signalling, in CLL and other B-cell cancers.

Updated Nov 12, 2026

## What they are

Bruton tyrosine kinase (BTK) inhibitors (suffix «-brutinib») treat chronic lymphocytic leukaemia, mantle cell, marginal zone and follicular lymphoma and Waldenström macroglobulinaemia. Ibrutinib was the first; acalabrutinib and zanubrutinib are more selective covalent inhibitors.

## Mechanism of action

B-cell receptor signalling passes through BTK. Covalent inhibitors bond to cysteine 481 in the ATP site and switch BTK off for the life of the protein. Malignant B cells lose their survival signals and die.

Target: Bruton tyrosine kinase (BTK)

## Key points

- Covalent BTK inhibitors (ibrutinib, acalabrutinib, zanubrutinib) bond to cysteine 481 in the active site.
- Class warnings: bleeding, infections, atrial fibrillation and other arrhythmias, cytopenias, second cancers.
- They are usually held around surgery because of bleeding risk.
- Zanubrutinib is more selective for BTK than ibrutinib, with less effect on TEC, EGFR and Src family kinases.

## Drugs in this class

- [**Zanubrutinib** A second-generation covalent BTK inhibitor for CLL and several B-cell lymphomas. Watch for bleeding, infections and… Bruton tyrosine kinase (BTK)](https://durgical.com/en/pharmacology/zanubrutinib/)

## Others in the class

- Ibrutinib and acalabrutinib (their pages sit under kinase inhibitors)
- Pirtobrutinib
- Orelabrutinib, tirabrutinib

## Test yourself

Think of the answer, then tap the question to see it.

## Which residue do covalent BTK inhibitors bond to?

Cysteine 481 of BTK.

## Why are BTK inhibitors usually held around surgery?

Because of their bleeding risk.

## Which three class adverse effects of BTK inhibitors matter most?

Bleeding, infection and atrial fibrillation.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=L01EL) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [Zanubrutinib: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a620009.html) (MedlinePlus (U.S. National Library of Medicine), 2024); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/medicines/895) (World Health Organization, 2025); [RCSB PDB - 6J6M: Co-crystal structure of BTK kinase domain with Zanubrutinib](https://www.rcsb.org/structure/6J6M) (RCSB Protein Data Bank, 2026).

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Source: https://durgical.com/en/pharmacology/classes/btk-inhibitors/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/classes/btk-inhibitors/