Purity >95%. Acalabrutinib is an irreversible inhibitor of Bruton's tyrosine kinase (BTK). It can dose-dependently inhibit B cell receptor signaling in primary chronic lymphocytic leukemia cells. In kinase-inhibition assays, acalabrutinib was more selective than ibrutinib for inhibiting BTK and did not inhibit EGFR, Itk, or Txk signaling.