Abstract 3692: Preclinical studies of a mutant p53 reactivating drug in pancreatic cancer

Abstract

Abstract Pancreatic cancer therapy suffers from a lack of effective chemotherapy. TP53 is second only to Kras as the most commonly mutated gene in pancreatic cancer with point mutations occurring in 75% of patients. Recently, our laboratory identified NSC319726 (726) as an allele specific p53 mutant reactivating compound (Yu, et al. 2012, Cancer Cell). This compound selectively kills cancer cells that express the p53-R175H mutation by restoring wildtype structure and function to this mutant. It does not reactivate the DNA contact mutant, p53-R273H or p53-R248H. This established 726 as a lead compound for mutant p53 targeted drug development. We are currently investigating the potential of 726 as novel anti-cancer drug through pre-clinical studies in pancreatic cancer. We have investigated the pharmacokinetics (PK) and pharmacodynamics (PD) of 726 in murine pancreatic cancer cell lines derived from the KPC mouse model expressing mutant KrasG12D and different alleles of TP53 (WT, null, p53R172H, p53R270H). Using LC/MS/MS we developed a sensitive assay for detection of 726 in mouse plasma. PK studies indicate a half-life of approximately 4 hours with an AUC of 199.78 ng/ml/h for a single 1mg/kg dose given Intravenously. Treatment of KPC cell lines with 726 indicates that the murine p53R172H protein is reactivated as indicated by loss of mutant conformation and induction of p53 target gene transcription. Cell growth inhibition assays reveal that the cell line KPCp53-R172H is sensitive to 726 while the KPCp53-R270H is not. We have developed a PD assay for 726 consisting of cleaved caspase-3 immunostaining and measurement of transcriptional levels of p53 targets PUMA, Noxa and p21. Using these assays we have tested several doses of 726 and found that we detect activity of 726 in KPCp53-R172H xenograft tumors while at the same time relatively no activity in KPCp53-R270H tumors. These same assays were also performed on KPC autochthanous tumors and again reveal activity of 726 in the KPCp53-R172H mice. Efficacy studies in the KPCp53-R172H xenografts reveal potent tumor growth inhibition at both IV (1mg/kg) and IP (5mg/kg) dosing while no evidence of growth inhibition in KPCp53-R270H. These studies confirm that 726 is an allele-specific p53 mutant reactivating compound and holds promise for future applications in pancreatic cancer. Citation Format: Xin Yu, Zhe Li, Oliver S. Eng, Ashley T. Tsang, Hongxia Lin, Murugesan Gounder, Darren R. Carpizo. Preclinical studies of a mutant p53 reactivating drug in pancreatic cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3692. doi:10.1158/1538-7445.AM2014-3692