Abstract 4994: Crizotinib enhances the efficacy of BX-795 identified by high-throughput screening of pan-active drugs in colorectal cancer cells
Authors: Ghosh Susmita , Fan Fan , Roszik Jason , Powell Reid , Park Yong , Stephan Clifford , Ellis Lee M. , Bhattacharya Rajat 
Published: April 2023

Background: Colorectal cancer (CRC) is a heterogeneous disease with various driver genetic mutations. Recent improvements in targeted therapies have shown some benefit in patients with BRAF mutated metastatic CRC (mCRC), while several efforts focusing on KRASG12C inhibitors (alone or in combination) are being examined with outcomes pending. Immunotherapies have shown efficacy in only ~5% of patients with mCRC having MSI-H. Hence, it is important to utilize unbiased approaches in order to identify novel therapies that have the potential to improve the outcomes in a large proportion of patients with mCRC.

Aim: We aimed to perform high-throughput screening (HTS) using “pan-active” drugs to identify novel effective therapeutic combinations for patients with KRAS/BRAF mutated mCRC.

Methods: We performed unbiased HTS with a set of 250 drugs that were either approved by the FDA or are currently in clinical trials. The effect of these drugs on cell growth inhibition were determined as single agents in 2D and 3D cultures using KRAS or BRAF mutated CRC cell lines. Drugs that decreased cell proliferation in both 2D and 3D cultures and effective in both HCT116 (KRAS mutated) and HT29 (BRAF mutated) cell lines, were termed as “pan-active” drugs. 57 “pan active” drugs were identified that primarily fall into 9 classes based on targets/pathways they inhibit. Next, the efficacy of the top three candidate drugs from each class of “pan-active” drugs were determined by pairing with drugs of other classes to identify combinations that are most effective in inducing cell death in CRC cells. Using the Bliss model of synergy, BX-795 was identified to be synergistic with Crizotinib. Effects of combining BX-795 with Crizotinib were further validated in vitro by 1) cell growth assays, and 2) measuring changes in cell signaling pathways and apoptotic mediators by western blotting and flow cytometry.

Results: Pairwise HTS studies using “pan-active” drugs demonstrated that combining BX-795 with Crizotinib was synergistic in multiple CRC cell lines. This combination was further validated in vitro by MTT and colony formation assays. Analyses of markers for apoptosis by western blotting demonstrated that the drug combination increased cell death in multiple CRC cell lines as compared to single agents. Flow cytometry results using FITC Annexin V and PI confirmed that the combination increased apoptotic cell death in multiple CRC cell lines when compared to the monotherapies.

Conclusions: Our unbiased HTS along with in vitro validation studies demonstrated that the combination of BX-795 with Crizotinib can serve as a possible novel effective therapeutic combination in patients with mCRC. Our preclinical in vitro studies serve as the basis for in vivo efficacy studies and future clinical studies in order to determine the efficacy of this drug combination in patients with mCRC.

Citation Format: Susmita Ghosh, Fan Fan, Jason Roszik, Reid Powell, Yong Park, Clifford Stephan, Lee M. Ellis, Rajat Bhattacharya. Crizotinib enhances the efficacy of BX-795 identified by high-throughput screening of pan-active drugs in colorectal cancer cells. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4994.