Discovery of a highly potent orally bioavailable imidazo-[1, 2-a]pyrazine Aurora inhibitor

Imidazo-[1, 2-a]pyrazine 1 is a potent inhibitor of Aurora A and B kinase in vitro and is effective in in vivo tumor models, but has poor oral bioavailbility and is unsuitable for oral dosing. We describe herein our effort to improve oral exposure in this class, resulting ultimately in the identification of a potent Aurora inhibitor 16, which exhibited good drug exposure levels across species upon oral dosing, and showed excellent in vivo efficacy in a mouse xenograft tumor model when dosed orally.

2'-Modified Guanosine Analogs for the Treatment of HCV

Novel 2'-modified guanosine nucleosides were synthesized from inexpensive starting materials in 7-10 steps via hydroazidation or hydrocyanation reactions of the corresponding 2'-olefin. The antiviral effectiveness of the guanosine nucleosides was evaluated by converting them to the corresponding 5'-O-triphosphates (compounds 38-44) and testing their biochemical inhibitory activity against the wild-type NS5B polymerase.

Discovery of a Potent, Injectable Inhibitor of Aurora Kinases Based on the Imidazo-[1,2-a]-Pyrazine Core

The imidazo-[1,2-a]-pyrazine (1) is a dual inhibitor of Aurora kinases A and B with modest cell potency (IC50 = 250 nM) and low solubility (5 μM). Lead optimization guided by the binding mode led to the acyclic amino alcohol 12k (SCH 1473759), which is a picomolar inhibitor of Aurora kinases (TdF K d Aur A = 0.02 nM and Aur B = 0.03 nM) with improved cell potency (phos-HH3 inhibition IC50 = 25 nM) and intrinsic aqueous solubility (11.4 mM). It also demonstrated efficacy and target engagement in human tumor xenograft mouse models.

Abstract 1648: SCH 1473759, a novel aurora inhibitor, demonstrates enhanced antitumor activity in combination with taxanes and KSP inhibitors

Aurora kinases are required for orderly progression of cells through mitosis. Inhibition of these kinases by siRNA or a small molecule inhibitors results in aberrant endoreduplication and cell death. SCH 1473759 is a novel Aurora inhibitor with potent mechanism based cell activity. The compound is active against a large panel of tumor cell lines from different tissue origin and genetic backgrounds. We found that asynchronous cells require 24 hour exposure to SCH 1473759 to induce maximal endoreduplication and cell kill. However, following a taxane or KSP inhibitor mitotic arrest, less than 4-hour exposure was sufficient to induce endoreduplication. This finding correlated with the ability of SCH 1473759 to accelerate exit from mitosis in response to taxane and KSP induced arrest, but not that of a nocodazole arrest. SCH 1473759 demonstrated single agent biomarker and anti-tumor activity in A2780 ovarian xenograft models. Further, efficacy was enhanced in combination with taxotere and found to be most efficacious when SCH 1473759 was dosed 12-hours post taxotere. These findings could have clinical implications for the development of Aurora inhibitors.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1648.