Cell-permeable. A potent protein kinase C (PKC) inhibitor (IC₅₀ = 7.9 nM). In vitro, discriminates between Ca²⁺-dependent and -independent isoforms of PKC; selectively inhibits PKCα and PKCβ1 (IC₅₀ values are 2.3 and 6.2 nM respectively) but does not inhibit the activity of PKCδ, -ε, or -ζ (IC₅₀ > 3µM).