Abstract 800: Synergistic effects of CBL0137 and gemcitabine against non-small cell lung and pancreatic cancer xenografts

Abstract

Abstract CBL0137 represents a novel class of small molecules that simultaneously activate p53 and inhibit cancer-associated stress response pathways, such as NF-κB and HSF-1. The effects of CBL0137, culminating in tumor cell death, are mediated by the inhibition of FACT, a chromatin remodelling factor complex composed of SSRP1 and SPT16 subunits, that is involved in the transcription of genes with highly ordered chromatin structure, replication, and mitosis. FACT is expressed during early embryogenesis and in undifferentiated progenitors and stem cells of adult tissues while protein levels of both FACT subunits are almost undetectable in differentiated cells and tissues. FACT is expressed in several tumor types compared to equivalent normal tissues. In particular, SSRP1 is expressed in a high proportion of lung and pancreatic cancers (∼45-63%). FACT positive tumors are associated with an aggressive malignant phenotype (high grade, metastatic disease, worse overall survival). Therefore, FACT represents a potentially important target for cancer therapy. We investigated the effect of CBL0137 and its combination with gemcitabine a nucleoside analog used in treatment of non-small lung cancer (NSCLC) and pancreatic ductal adenocarcinoma (PDA). We found that CBL0137 had significant antitumor activity against a H1975 NSCLC xenograft model (89.6% growth inhibition) as well as a patient-derived PDA (PDA#2) model (70.4% growth inhibition). Furthermore, CBL0137 acted synergistically with gemcitabine against both tumor types as evidenced by increased median survival time compared to each drug administered as a single agent (increase in survival time: H1975- >47 days combination vs 24 days CBL0137 only, 32.5 days gemcitabine only; PDA#2- >42 days combination vs 28 days CBL0137 only, 30.5 days gemcitabine only). Preliminary investigation into the mechanism underlying the synergy of this combination suggest that CBL0137 may enhance gemcitabine activity in part by abrogating the expression of modulators of gemcitabine response, such as cytidine deaminase and ribonucleotide reductase. Together, these data indicate that CBL0137 may provide a clinical benefit for the treatment of both NSCLC and PDA when combined with standard agent gemcitabine. Citation Format: Catherine Burkhart, Rachael Kohrn, Brittany Walker, David Meyer, Katerina Gurova, Andrei Gudkov. Synergistic effects of CBL0137 and gemcitabine against non-small cell lung and pancreatic cancer xenografts. [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 800. doi:10.1158/1538-7445.AM2014-800