ACP-5862 is a major active, circulating, pyrrolidine ring-opened metabolite of Acalabrutinib with an IC50 of 5.0 nM for Bruton tyrosine kinase (BTK)[1]. Acalabrutinib is an orally active, irreversible, and highly selective BTK inhibitor, with an IC50 of 3 nM and EC50 of 8 nM[2].
[1]. Podoll T, et al. Bioavailability, Biotransformation, and Excretion of the Covalent Bruton Tyrosine Kinase Inhibitor Acalabrutinib in Rats, Dogs, and Humans. Drug Metab Dispos. 2019 Feb;47(2):145-154. [2]. Herman SE, et al. The Bruton's tyrosine kinase (BTK) inhibitor acalabrutinib demonstrates potent on-target effects and efficacy in two mouse models of chronic lymphocytic leukemia. Clin Cancer Res. 2016 Nov 30