SB-218078 is a potent, selective, ATP-competitive and cell-permeable checkpoint kinase 1 (Chk1) inhibitor that inhibits Chk1 phosphorylation of cdc25C with an IC₅₀ of 15 nM. SB-218078 is less potently inhibits Cdc2 (IC₅₀ of 250 nM) and PKC (IC₅₀ of 1000 nM). SB-218078 causes apoptosis by DNA damage and cell cycle arrest^[1][2][3]. In Vitro: SB-218078 (2.5-5 μM; 18 hours; HeLa cells) treatment abrogates G2 cell cycle arrest caused by either γ-irradiation or a topoisomerase I Topotecan inhibition^[1].
SB-218078 (500-625 μM; 96 hours; HeLa and HT-29 cells) treatment significantly increases the cytotoxicity of DNA damage ^[1]. In Vivo: SB-218078 (5 mg/kg; intraperitoneal injection; for 16 hours; C57/Bl6 mice) treatment could promote a strong increase of γ-H2AX and apoptosis throughout the lymphoma, while having no effect on a healthy spleen in Myc-induced lymphomas mouse model^[2].