Abstract LB-224: Anti-tumor effects of ECP-1014 in combination with erlotinib in HT-29 xenograft murine colon carcinoma model

Abstract

Abstract Objective: The objective of this study was to evaluate the effect of ECP-1014, a new selective COX-2 inhibitor, in combination with erlotinib on tumor growth in a HT-29 xenograft murine colon carcinoma model. Pre-clinical studies suggest that cyclooxygenase-2 (COX-2) inhibitors can affect most of the acquired epidermal growth factor (EGFR) resistance pathways. Therefore, the hypothesis was that combining a COX-2 inhibitor with an EGFR inhibitor such as erlotinib would result in superior tumor control versus either agent alone. Methods: 48 CB17-SCID male mice were implanted with 2-5×106 HT-29 cells. Once tumors reached approximately 75 mm3 in size mice were randomly assigned to 6 treatment groups: vehicle (G1), 1mg/kg ECP-1014 (G2), 1 mg/kg ECP-1014 + 50 mg/kg erlotinib (G3), 10 mg/kg ECP-1014 (G4), 10mg/kg ECP-1014 +50 mg/kg erlotinib (G5), 50 mg/kg erlotinib (G6). ECP-1014 and erlotinib were administered daily by oral gavage, beginning immediately following randomization and continued for 22 days. Tumor volume measurements were taken every 3 days. On day 24 tumor tissue was collected from each animal to determine ECP-1014, erlotinib, and PGE2 levels. Tumor samples were prepared using protein precipitation after grinding in nitrogen. 0.1μL of 50% methanol water solution and 50 mg tumor sample were vortexed for 3 minutes, and 200μL acetonitrile containing the internal standard was addd and vortexed for an additional 5 minutes. The tubes were then placed in the centrifuge at 16000 G for 40 minutes at 4oC. 100μL of the supernatant was transferred to a 96-well plate for analysis by LC-MS/MS.) Results: All animals developed tumors. There was no difference between treatment groups in body weights over the course of the study. The combinations of ECP-1014 + erlotinib produced a 66% (G3) and 60% (G5) slowing of tumor growth when compared to vehicle (G1). ECP-1014 10 mg/kg (G4) produced 51% suppression of tumor growth alone compared to G1, whereas erlotinib alone produced a 38% suppression of tumor growth alone when compared to G1. The addition of erlotinib produced a 1.5X increase in the tumor levels of ECP-1014 when compared to ECP-1014 tumor levels alone (mean+SD, 1479+652 to 2244+887μg/g for G3; 9720+2759 to 14745+4758μg/g for G5). ECP-1014 alone or in combination with erlotinib suppressed PGE-2 levels in the tumor from 66-100%. Summary: ECP-1014 alone was superior to erlotinib 50 mg/kg in slowing tumor growth. In a separate study using the identical model we demonstrated that 0.3 mg/kg 1014 was shown to be roughly equipotent to 10 mg/kg celecoxib both in terms of tumor control and PGE2 suppression. However, the combination of ECP-1014 + erlotinib showed the greatest tumor growth suppression when compared to vehicle and each therapy alone. There was little difference between ECP-1014 1 and 10 mg/kg dose groups when combined with erlotinib. Citation Format: Bobby W. Sandage, Micky Tortorella, Yanmei Zhang, Zhengchao Tu, Yican Wang, Xiaorong Liu, John J. Talley. Anti-tumor effects of ECP-1014 in combination with erlotinib in HT-29 xenograft murine colon carcinoma model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-224.