Cassette dosing in tumor bearing animals for the discovery of NVP-AUY922, a novel HSP90 inhibitor.

B289

Cassette or cocktail dosing increases pharmacokinetic throughput in drug discovery by administering a combination of compounds to animals and measuring each discrete compound by LCMSMS. We first demonstrated that cassette dosing did not affect the mouse plasma pharmacokinetics (PK) of individual compounds in a series of diarylpyrazole resorcinols. Having validated the approach, we used this methodology to evaluate plasma and tumor pharmacokinetics in a diarylisoxazole resorcinol series. Combinations of five novel agents were administered together with a pharmacokinetic standard (VER-50589) to NCr athymic mice bearing HCT116 human colon carcinoma xenografts using an i.v. dose of 4 mg/kg of a cocktail of each compound in 10% DMSO, 1% tween 20 in saline. Evaluation of plasma and tumor pharmacokinetics showed no more than 2-fold variation in plasma and tissue levels and pharmacokinetic parameters of compound VER-50589 dosed as a standard in 5 different cassettes. The tested compounds showed much greater differences in distribution in tumors with tumor to plasma ratios ranging from 0.2 to 19.6 resulting in significant differences in tumor levels between compounds. Those compounds with the greatest tumor concentrations giving values well above their in vitro cellular inhibitory activity (GI50) were selected for further in vivo evaluation. The compound NVP-AUY922 gave tumor concentrations 35 times above its GI50 and was subsequently shown to have significant antitumor efficacy associated with target modulation in xenograft models. This work exemplifies the power of cassette dosing in tumor bearing animals. NVP-AUY922 has recently entered Phase I clinical trials.