G? 6976 is a nonglycosidic indolocarbazole that inhibits protein kinase C (PKC) with IC50 values of 2.3 and 6.2 nM for PKCα and PKCβ1, respectively. It does not inhibit the activity of PKCδ, PKCε, or PKCζ (IC50s > 3 μM), indicating a preference for the Ca2+-dependent subtypes, PKCα and PKCβ1. G? 6976 also inhibits the checkpoint kinases Chk1/2. It was shown to abrogate DNA damage-induced S- and G2-phase cell cycle arrest, leading to cytotoxicity in p53 mutant tumor cells.
