BI-2536 is a potent, selective inhibitor of polo-like kinase 1 (PLK1) (IC₅₀ = 0.83 nM). It blocks the activities of Plk2 and Plk3 to a slightly lesser extent with IC₅₀ of 3.5 nM and 9.0 nM, respectively. BI-2536 potently causes a mitotic arrest and induces apoptosis in human cancer cell lines of diverse tissue origin.