GK921 is a transglutaminase 2 (TGase) inhibitor with an IC₅₀ of 7.71 μM for human recombinant TGase 2. IC50 & Target: IC50: 7.71 μM (TGase)^[1] In Vitro: GK921 inhibits the TGase 2-induced polymerization of I-κBα and p53 in a dose-dependent manner. The cytotoxicity of GK921 ranged from GI₅₀ of 10^-10 to 10^-4 M. The average GI₅₀ is 9.05×10^-7 M. GK921 rescues p53 levels and consequently induces apoptosis; a concentration-dependent increase in cleaved poly(ADP-ribose) polymerase (c-PARP) and p53 levels is observed^[1]. In Vivo: A single treatment with GK921 almost completely reduces tumor growth by stabilizing p53 in the ACHN and CAKI-1 preclinical xenograft tumor models^[1].