Abstract A259: Characterization of next generation (Gen2.5) KRAS antisense inhibitors in NSCLC, PDAC, and CRC models.

KRAS is among the first described oncogenes and one of the most frequently mutated genes in human solid tumors. Despite substantial efforts to identify specific KRAS inhibitors, no effective therapeutic strategies to target KRAS directly have been identified. Here we describe the selective inhibition of KRAS with next generation (Gen2.5) antisense oligonucleotides. We recently demonstrated preclinical and clinical activity of a next-generation constrained-ethyl (cEt) modified (Gen 2.5) antisense oligonucleotides (ASOs) targeting STAT3 mRNA (STAT3Rx/AZD9150). Systemic delivery of unformulated STAT3Rx/AZD9150 produced robust target RNA and protein reductions in a broad range of xenograft models (AACR 2013). More importantly, STAT3Rx/AZD9150 showed striking clinical activity in the phase I dose escalation study, producing anti-tumor activity in 4 out of 6 patients with advanced treatment-refractory lymphoma (ASCO 2013). In this study, we generated a panel of high affinity Gen2.5 ASO targeting KRAS. Anti-proliferative effects of the KRAS ASOs were evaluated on a panel of colorectal carcinoma (CRC), non-small cell lung carcinoma (NSCLC) and pancreatic ductal adenocarcinoma (PDAC) cell lines. KRAS ASOs potently and selectively inhibited growth of KRAS mutant CRC lines but did not affect the growth of KRAS WT CRC cells in 2D growth assays. Evaluation of KRAS depletion in NSCLC and PDAC lines revealed that sensitivity of these lines to growth inhibition in 2D assays required mutant KRAS status and the presence of a previously described “KRAS addiction” gene expression signature (Singh et al 2009). Surprisingly, further evaluation of KRAS ASO mediated depletion of NSCLC and PDAC lines in 3D growth assays (e.g. soft agar colony formation and polystyrene sponge (Alvetex)) resulted in strong inhibition of colony formation in all mutant KRAS lines, but not WT KRAS lines, and the sensitivity to KRAS depletion was independent of the expression of the “KRAS addiction” signature. Collectively, we have shown that KRAS mutational status confers specific sensitivity to the ASO-mediated KRAS knockdown (KRAS oncogene addiction). Our data also highlights that antisense-mediated inhibition of KRAS may represent a promising and translatable approach to target KRAS therapeutically. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A259. Citation Format: Alexey S. Revenko, Gourab Bhattachrjee, Chris May, Brett P. Monia, A. Robert MacLeod. Characterization of next generation (Gen2.5) KRAS antisense inhibitors in NSCLC, PDAC, and CRC models. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A259.