Bisindolylmaleimide I (GF 109203X) is a staurosporine (sc-3510) inspired molecule, which has been shown to display equally potent inhibition, but with vastly superior selectivity, for all of the known isoforms of PKC (IC50 = 8-20 nM). Inhibition is competitive with respect to ATP, which suggests that Bisindolylmaleimide I occupies the ATP binding domain of the PKC isoforms. Bisindolylmaleimide I (GF 109203X) has been used to selectively probe for PKC-mediated pathways for transduction of hormone, cytokine, and growth factor signals. It inhibits PKC within intact platelets and T cells, Fas-mediated apoptosis, and T cell-mediated autoimmune diseases, as well as GSK-3. See sc-24004 for water soluble form of Bisindolylmaleimide I. Bisindolylmaleimide I (GF 109203X) is an inhibitor of PHK/CaM, PKC α, PKC β, PKC δ, PKC ε, PKC γ and SR/HTR3.