ibrutinib or acalabrutinib (AbbVie Inc.)

**Ibrutinib or acalabrutinib** is a non-specific alternative-drug expression rather than the name of one chemical entity. It refers to either of two oral, covalent small-molecule inhibitors of Bruton tyrosine kinase that suppress B-cell receptor signaling and are used in B-cell malignancies. The provided study context is a retrospective comparison of incident atrial-fibrillation risk in patients with chronic B-cell malignancies exposed to either agent; it is not a fixed-dose combination or a single investigational product. Both agents bind a cysteine residue in the Bruton tyrosine kinase active site and irreversibly inhibit its enzymatic activity. ([accessdata.fda.gov](https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/216387s006lbl.pdf))