Abstract 2078: The imipridone ONC212 cooperates with MEK and immune checkpoint inhibition to elicit in vivo regression of KPC mouse pancreatic tumors
Authors: Chan Jasper , Lannigan Alexis J. , Sun Grace , Prabhu Varun V. , Edwards Robert , Zhang Leiqing , Zhou Lanlan , El-Deiry Wafik S. , Raufi Alexander Grenander 
Published: March 2024

Abstract
Background: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with limited therapeutic options. ONC212 is a second-generation imipridone with antitumor effects in human PDAC cell lines. ONC212 has been shown to bind to mitochondrial protease ClpP, suppress ClpX, and impair oxidative phosphorylation by decreasing ATP production. While ONC212 has been evaluated in immunocompromised mice xenografted with human pancreatic tumors, ONC212 has not been evaluated, either alone or in combination with MEK and/or immune checkpoint inhibition (ICI), in immunocompetent mice bearing notoriously aggressive KrasLSL.G12D/+; Tp53LSL.R172H/+; Pdx1Cretg/+ (KPC) murine PDAC tumors. We hypothesized that, like human PDAC cells, KPC cells would demonstrate sensitivity to ONC212 both in vitro and in vivo. Our group has previously shown that ONC212 synergizes with trametinib to induce tumor cell death in human PDAC cells. We therefore hypothesized that this combination, together with ICI, would enhance KPC tumor cell death in vivo.
Methods: We determined in vitro sensitivity of the KPC cells to ONC212 alone and in combination with trametinib using CellTiter-Glo® luminescent cell viability assays. Results were analyzed after 72 hours of incubation using Compusyn and Combenefit. In vivo experiments involved C57BL/6 mice that were injected subcutaneously with 3 × 105 KPCy cells in 100 mL of PBS/matrigel. To determine the ideal ONC212 dose, we tested five different doses/dosing frequencies (50 mg/kg; 25 mg/kg; 12.5 mg/kg given by oral gavage weekly or twice weekly) in tumor-bearing (50-75 mm3) mice. Mouse weight and tumor size was measured every four days. Treatment was stopped once tumor volumes reached 3,000 mm3 or if ulceration occurred. Once the ideal dose of ONC212 was determined, a study treating KPC tumor-bearing C57BL/6 mice with ONC212, trametinib, and ICI (anti-PD-1 mAb) alone and all possible doublet/triplet combinations was performed using the same methods.
Results: We found that the combination of ONC212 and trametinib exhibited synergy in the KPC cell line in vitro. Our in vivo experiments revealed that ONC212 controlled KPC tumor growth in a dose-dependent manner, however, toxicity was also noted at higher, more frequent doses. While both 25 mg/kg and 50 mg/kg twice weekly were equally effective, 25 mg/kg was better tolerated and determined to be the ideal dose. In the combination therapy study, all treatments resulted in tumor reduction, as compared to the vehicle control; however, the triple therapy group had the lowest average tumor size at day twenty. Toxicity was noted in mice receiving at least two treatments, reflected by reduced weights and mobility. Further analysis of the tumor immune microenvironment using multiplex cytokine and immunofluorescence are ongoing.
Citation Format: Jasper Chan, Alexis J. Lannigan, Grace Sun, Varun V. Prabhu, Robert Edwards, Leiqing Zhang, Lanlan Zhou, Wafik S. El-Deiry, Alexander Grenander Raufi. The imipridone ONC212 cooperates with MEK and immune checkpoint inhibition to elicit in vivo regression of KPC mouse pancreatic tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2078.