Development of a multivariate pharmacodynamic biomarker assay for HSP90 inhibitors

C131

Heat shock protein 90 (HSP90) is a ubiquitously expressed molecular chaperon which involves in multiple cellular functions, such as signal transduction and protein folding. Together with other co-chaperons, HSP90 participates in many key processes in oncogenesis such as self-sufficiency in growth signals, stabilization of mutant proteins, angiogenesis, and metastasis, by regulating the maturation and stability of its client proteins. Among HSP90 clients are Her2, v-Src, Bcr-Abl, p53 mutant, VEGF, NOS, MMP2, AKT, and steroid receptors. Multiple cancer drugs have targeted HSP90 to inhibit its activity in cancerous cells, including geldanamycin, its derivatives and ridicicol. In pre-clinical and clinical development, HSP70, CDK4 and other proteins have been used as single biomarkers to monitor drug activity and response. We have developed a multivariate biomarker development workflow based on our proprietary multiplex PCR technology on Beckman Coulter’s GeXP CEQ platform. The procedure starts from an extensive literature mining and informatics data mining to select potential biomarker genes which are highly related to the drug target and show expression response to the drug. A quantitative multiplex PCR assay is then developed and validated in model systems for drug response, followed by a recursive procedure to refine the biomarker gene set in the assay. The final product is a single quantitative assay which features both robust performance and convenient usage. For HSP90 inhibitors, we have developed a biomarker assay which shows both dose-dependent and time-dependent response to the model compounds 17-N-Allylamino-17-demethoxygeldanamycin (17-AAG) and Ridicicol in cancer cells.