ibrutinib
Imbruvica (ibrutinib) is the first-in-class Bruton tyrosine kinase inhibitor. Taken by mouth, it blocks the survival signalling of malignant B cells and transformed the treatment of chronic lymphocytic leukaemia, Waldenstrom macroglobulinaemia and mantle cell lymphoma.
This page is based on FDA prescribing information and the EMA medicine record for ibrutinib, cross-checked with DailyMed and MedlinePlus; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
Malignant B cells keep themselves alive by constantly receiving a "stay and multiply" memo through the B-cell receptor, and BTK is the clerk who processes every memo. Ibrutinib permanently jams that clerk's desk, so the memos pile up unread, the cells stop dividing and eventually fade away.
In simple terms
B-cell cancers such as chronic lymphocytic leukaemia rely on signals passing through a protein called Bruton tyrosine kinase. Ibrutinib binds to BTK and permanently switches it off. Without that signal, cancer cells stop growing, lose their ability to survive in protective tissue niches and drift into the blood, where they die. As an oral medicine, it replaced many infusion-based regimens.
In depth
Ibrutinib is an oral small molecule that forms a covalent bond with the C481 residue of BTK, irreversibly inhibiting its kinase activity. This blocks B-cell receptor signalling through PLCg2, PI3K and NF-kB pathways, suppressing malignant B-cell proliferation, adhesion and migration. Continuous once-daily dosing maintains target occupancy; resistance most often emerges through BTK C481 mutations or downstream pathway activation.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How ibrutinib covalently switches off BTK in B-cell cancers
- B-cell cancers such as chronic lymphocytic leukaemia rely on signals passing through a protein called Bruton tyrosine kinase.
- Ibrutinib is an oral small molecule that forms a covalent bond with the C481 residue of BTK, irreversibly inhibiting its kinase activity.
- This blocks B-cell receptor signalling through PLCg2, PI3K and NF-kB pathways, suppressing malignant B-cell proliferation, adhesion and migration.
- Continuous once-daily dosing maintains target occupancy; resistance most often emerges through BTK C481 mutations or downstream pathway activation.
Target: Bruton tyrosine kinase (BTK)
A kinase in the B-cell receptor pathway that malignant B cells depend on for survival and proliferation; irreversible blockade cuts the signal that keeps them alive.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- Treatment of adult patients with chronic lymphocytic leukemia or small lymphocytic lymphoma
- Treatment of adult patients with chronic lymphocytic leukemia or small lymphocytic lymphoma with 17p deletion
- Treatment of adult patients with Waldenstrom's macroglobulinemia
Approved uses in European Union
EMA- With rituximab, cyclophosphamide, doxorubicin, vincristine and prednisolone, alternating with R-DHAP, followed by ibrutinib monotherapy, for previously untreated mantle cell lymphoma in adults eligible for autologous stem cell transplantation
Official sources
The statements on this page trace back to these records.
- Imbruvica (ibrutinib) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- DailyMed: Imbruvica (ibrutinib) label
DailyMed, U.S. National Library of Medicine
- U.S. Food and Drug Administration: ibrutinib prescribing information
U.S. Food and Drug Administration
- MedlinePlus: ibrutinib
MedlinePlus, U.S. National Library of Medicine
- National Cancer Institute: ibrutinib
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.