1.Pharmacologic properties of AG-012986, a pan-cyclin-dependent kinase inhibitor with antitumor efficacy.
Zhang C1, Lundgren K, Yan Z, Arango ME, Price S, Huber A, Higgins J, Troche G, Skaptason J, Koudriakova T, Nonomiya J, Yang M, O'Connor P, Bender S, Los G, Lewis C, Jessen B. Mol Cancer Ther. 2008 Apr;7(4):818-28. doi: 10.1158/1535-7163.MCT-07-0440.
AG-012986 is a multitargeted cyclin-dependent kinase (CDK) inhibitor active against CDK1, CDK2, CDK4/6, CDK5, and CDK9, with selectivity over a diverse panel of non-CDK kinases. Here, we report the potent antitumor efficacies of AG-012986 against multiple tumor lines in vitro and in vivo. AG-012986 showed antiproliferative activities in vitro with IC(50)s of <100 nmol/L in 14 of 18 tumor cell lines. In vivo, significant antitumor efficacy induced by AG-012986 was seen (tumor growth inhibition, >83.1%) in 10 of 11 human xenograft tumor models when administered at or near the maximum tolerated dose for 8 or 12 days. AG-012986 caused dose-dependent hypophosphorylation at Ser(795) of the retinoblastoma protein, cell cycle arrest, and apoptosis in vitro. Colony-forming assays indicated that the potency of AG-012986 substantially decreased with treatment time of <24 h. In vivo, AG-012986 also showed dose-dependent retinoblastoma Ser(795) hypophosphorylation, cell cycle arrest, decreased Ki-67 tumor staining, and apoptosis in conjunction with antitumor activity.
2.Off-target immune cell toxicity caused by AG-012986, a pan-CDK inhibitor, is associated with inhibition of p38 MAPK phosphorylation.
Lee DU1, Jessen B. J Biochem Mol Toxicol. 2012 Mar;26(3):101-8. doi: 10.1002/jbt.20415. Epub 2011 Nov 16.
AG-012986 is a pan-CDK (cyclin-dependent kinase) inhibitor that has in vitro and in vivo antitumor properties but was stopped in development due in part to rapid bone-marrow-independent white blood cell toxicity in preclinical studies and the potential for acute and delayed immunosuppression in humans. Because peripheral lymphocytes are largely nonproliferating, it was hypothesized the toxicity of AG-012986 was due to an off-target mechanism and not driven by the intended pharmacology. We show the toxicity mechanism in primary human immune cells is caspase driven. T-cells treated with AG-012986 and acutely stimulated through the T-cell receptor exhibited decreased toxicity while still maintaining cell division inhibition. This indicated that the pharmacology of AG-012986 functioned as expected but the toxicity had now been decoupled through activation. Induced phosphorylation of p38 and IL-2 production was impaired with AG-012986. Thus, AG-012986 could cause apoptosis of T-cells by targeting upstream kinases in the p38 Mitogen-activated protein kinase (MAPK) pathway and impairing cellular survival.