LY2857785

LY2857785 is a type I reversible and competitive ATP kinase inhibitor against CDK9 (IC₅₀ 11 nM) and other transcription kinases CDK8 (IC₅₀ 16 nM), and CDK7 (IC₅₀ 246 nM). IC50 & Target: IC50: 11 nM (CDK9), 16 nM (CDK8), 246 nM (CDK7)^[1] In Vitro: LY2857785 shows good selectivity against a panel of 114 protein kinases, with only 5 other protein kinases inhibited with potency (IC₅₀) less than 0.1 μM, and a total of 14 kinases less than 1 μM. At the cellular level, LY2857785 inhibits CTD P-Ser2 and CTD P-Ser5 in U2OS cells at IC₅₀s 0.089 (n=13) and 0.042 (n=1) μM, respectively. However, LY2857785 only induces a moderate G₂-M DNA content increase, from 35% to 55%, with EC₅₀ 0.135 μM. LY2857785 shows potent compound exposure- and time-dependent cell proliferation inhibition in MV-4-11, RPMI8226, and L363 cells. When incubated between 4 to 24 hours, the cell growth inhibition potency reaches a maximal effect at 8 hours with IC₅₀s 0.04, 0.2, and 0.5 μM for MV-4-11, RPMI8226, and L363 cells, respectively. LY2857785-induced cancer cell apoptosis is also time dependent, reaching maximal potency at 8 hours with IC₅₀ 0.5 μM in L363 cells^[1]. In Vivo: In HCT116 xenograft tumor-bearing mice, LY2857785 demonstrates dose-dependent RNAP II CTD P-Ser2 inhibition potently with TED50 of 4.4 mg/kg and TEC50 of 0.36 μM. LY2857785 also shows significant duration of CTD P-Ser2 inhibition for 3 to 6 hours at TED70 (8 mg/kg) in HCT116 and MV-4-11 nude mice xenograft models. In the nude rat MV-4-11 xenograft model, LY2857785 similarly shows dose-dependent CTD P-Ser2 inhibition for 8 hours at TED70 (7 mg/kg) and TED90 (10 mg/kg). LY2857785 demonstrates the most dramatic tumor regression in the AML MV-4-11 xenograft tumor model either by i.v. bolus in mice or i.v. infusion in rats^[1].