Bisindolylmaleimide IV (Arcyriarubin A) is a potent protein kinase C (PKC) inhibitor, with IC50s ranging from 0.1 to 0.55 μM. Bisindolylmaleimide IV also inhibits PKA (IC50=3.1-11.8μM). Bisindolylmaleimide IV is a potent, selective inhibitor of human cytomegalovirus (HCMV) replication in cell culture with an IC50 of 0.2 μM.