Bruton tyrosine-protein kinase (BTK)

Molecular Classification

Enzyme, Non-receptor tyrosine kinase, Tec family kinase

Other Names

Bruton’s tyrosine kinase, tyrosine-protein kinase BTK, Btk

Disease Roles

Cancer (e.g., B cell leukemias, lymphomas, multiple myeloma, solid tumors)Autoimmune diseasesPrimary immunodeficiency (X-linked agammaglobulinemia)

Bruton tyrosine-protein kinase Overview

Bruton tyrosine-protein kinase (BTK) is a cytoplasmic non-receptor tyrosine kinase belonging to the Tec family, critically involved in B cell development, maturation, and signaling.[1][2][3][6][7] BTK transmits signals from activated B cell receptors and other immune receptors, leading to downstream activation of pathways such as phospholipase C gamma 2 (PLCγ2), nuclear factor-κB (NFκB), and MAP kinase, all central to immune cell function.[1][3] Loss-of-function mutations in the BTK gene cause X-linked agammaglobulinemia (XLA), characterized by an absence of mature B cells and immunoglobulins with recurrent infections.[1][7] Aberrant BTK activity is implicated in B-cell malignancies and autoimmune diseases, making it a validated therapeutic target. BTK inhibitors (e.g., ibrutinib, acalabrutinib, zanubrutinib) are used to treat B cell malignancies, and new indications are emerging in autoimmune and inflammatory diseases.[2][6][8] Emerging data also implicate BTK and its isoforms in several non-hematologic cancers, and in the regulation of myeloid cells and microglia, with clinical trials exploring BTK inhibition in conditions such as multiple sclerosis and solid tumors.[4][6][8]

Mechanism of Action

Irreversible covalent inhibition of kinase domain (e.g., ibrutinib binds Cys481) Disruption of B cell receptor signaling Impaired survival and proliferation of malignant B-cells Modulation of myeloid or microglial cell activation

Biological Functions

B cell development and maturation

Signal transduction (especially B cell receptor signaling)

Immune response modulation

Cell proliferation

Cell survival

Apoptosis regulation

Activation of myeloid cells and microglia

Disease Associations

Cancer (e.g., B cell leukemias, lymphomas, multiple myeloma, solid tumors)

Autoimmune diseases

Primary immunodeficiency (X-linked agammaglobulinemia)

Inflammation

Neurodegenerative disease (e.g., Multiple sclerosis)

Safety Considerations

Off-target effects (e.g., bleeding due to platelet dysfunction)
Increased risk of infections (due to B cell suppression)
Development of resistance mutations (e.g., C481S)
Cardiotoxicity (e.g., atrial fibrillation)
Cytopenias

Interacting Drugs

Ibrutinib

Acalabrutinib

Zanubrutinib

Spebrutinib

Evobrutinib

LFM-A13

CC-292 (also known as spebrutinib)

Associated Biomarkers

Biomarker
BTK protein expression (e.g., measured in B cells by flow cytometry for diagnosis/monitoring)
Mutational status of BTK (for resistance, e.g., C481S mutation)
p65BTK isoform (emerging biomarker in some solid tumors, such as colon and lung cancer)