Abstract 1055: Screens of targeted agents combined with the ubiquitin activating enzyme inhibitor TAK-243 or the pan-Akt inhibitor ipatasertib identified combinations that are effective in patient-derived complex spheroids
Authors: Coussens Nathan P. , Wright John J. , Parchment Ralph E. , Delosh René , Laudeman Julie , Reinhart Russell , Ogle Chad , Silvers Thomas , Dexheimer Thomas S. , Morris Joel , Doroshow James H. , Teicher Beverly A. 
Published: June 2022

Abstract
Combinations of targeted chemotherapeutics can provide new options to treat cancer; however, the preclinical discovery of potentially beneficial therapeutic combinations is challenging given the heterogeneity of cancer. Complex tumor spheroids, consisting of combined patient-derived tumor cells and stromal cells (human umbilical vein endothelial cells and mesenchymal stem cells) serve as a physiologically relevant in vitro model of solid tumors that is amenable to high-throughput screening. In this study, ten anticancer agents with a range of targets including MEK, mTOR, RAF, PI3K, and the proteasome, were tested both alone and in combination with the ubiquitin activating enzyme inhibitor, TAK-243, or the pan-Akt inhibitor, ipatasertib. All anticancer agents were tested over a 3 log range of concentrations up to their clinical Cmax value, if known. The activities of single agents and combinations were evaluated in complex spheroids grown from patient-derived tumor cells from the National Cancer Institute’s Patient-Derived Models Repository (https://pdmr.cancer.gov), including ten colon and six pancreatic adenocarcinoma and four melanoma cell lines. The spheroids were allowed to grow for three days prior to the addition of anticancer agents and cell viability was measured seven days later using CellTiter-Glo 3D. TAK-243 was cytotoxic against all six pancreatic adenocarcinoma spheroids and all four melanoma spheroids, as well as several colon adenocarcinoma spheroids. The single agent BRAF V600E-selective inhibitor, vemurafenib, showed selective cytotoxicity against melanoma spheroids with the BRAF V600E/K variant. TAK-243 in combination with vemurafenib produced greater than additive cytotoxicity in most complex spheroid models. The overall cytotoxicity of the TAK-243 and vemurafenib combination was similar in melanoma spheroids containing WT BRAF and the BRAF V600E/K variant. The activity of vemurafenib and the BRAF V600E-selective inhibitor dabrafenib were not equivalent in this combination screen and greater than additive cytotoxicity was observed more frequently when TAK-243 was combined with vemurafenib than with dabrafenib. The combination of ipatasertib and vemurafenib had additive and greater than additive cytotoxicity in more than half of the complex spheroid models tested. Other notable agents combined with ipatasertib included the MEK inhibitors trametinib and selumetinib, both of which produced greater than additive cytotoxicity in spheroids derived from pancreatic cancer metastases. These results might inform the prioritization of drug combinations for further investigation by in vivo studies. This project was funded in part with federal funds from the NCI, NIH, under contract no. HHSN261201500003I.
Citation Format: Nathan P. Coussens, John J. Wright, Ralph E. Parchment, René Delosh, Julie Laudeman, Russell Reinhart, Chad Ogle, Thomas Silvers, Thomas S. Dexheimer, Joel Morris, James H. Doroshow, Beverly A. Teicher. Screens of targeted agents combined with the ubiquitin activating enzyme inhibitor TAK-243 or the pan-Akt inhibitor ipatasertib identified combinations that are effective in patient-derived complex spheroids [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1055.