Abstract B079: Identification of synergistic drug combinations including MEK inhibitor and agents modulating the tumor microenvironment in an electroporation-induced pancreatic cancer model
Authors: Konrad Aline S. , Hägele Tanja , Zens Stefan , Vent Caroline , Hamberger Moritz , Baiker Sarah , Maes Aron , Leonhardt Carl-Stephan , Strobel Oliver , Politz Oliver , Zopf Dieter , Baumann Daniel , Mochayedi Julian , Offringa Rienk 
Published: January 2024

Abstract
Pancreatic ductal adenocarcinoma (PDAC) is refractory to cytostatic and immuno-oncology therapeutic strategies, leaving surgical resection of the tumor as the only treatment that can significantly prolong survival. We are therefore exploring optimized treatment strategies targeting cancer cells as well as infiltrating immune cells and the tumor microenvironment (TME) in an autochthonous mouse model for PDAC. Single focal tumors are induced through in vivo electroporation of gene constructs into the pancreas which encode mutated Kras and facilitate knock out the tumor suppressor genes P53, Cdkn2a and/or Smad4 via CRISPR/Cas9. The resulting tumors recapitulate the human disease with respect to genetics, histology and TME composition. Furthermore, this model allows the generation of tumors reflecting different PDAC subtypes, as well as the resection of primary tumors in combination with the (neo-)adjuvant regimens. Like the human disease, these tumors are refractory to chemotherapy and immune checkpoint blockade, whereas targeted therapy by means of MEK inhibitors merely leads to temporary delay of tumor outgrowth. We therefore tested the combination of MEK inhibitor treatment with different, potentially complementary modalities. We found the combination with agonist anti-CD40 antibodies to be highly effective. Prominent regressions are observed, and in combination with primary tumor resection long-term complete responses can be achieved even in a metastatic variant of the model. Apart from the direct cytostatic impact of MEKi on the Kras-transformed tumor cells, the mechanism of action of this synergistic drug combination involves enhancement of the anti-tumor T-cell response, suppression of CD4+ Tregs, and reduction of MDSCs and M2-type macrophages in favor of M1-type pro-inflammatory macrophages. A second highly effective regimen as identified in our experiments involves the combination of MEK inhibitors with the multi-kinase inhibitor regorafenib. In contrast to the aforementioned regimen, the complementary action of these drugs involves modulation of the TME by regorafenib. While the clinical translation of the MEKi/CD40 Ab regimen is hampered by toxicity issues encountered with agonist anti-CD40 Ab, the synergy as observed in the MEKi/regorafenib regiment provides a tangible path towards clinical testing.
Citation Format: Aline S. Konrad, Tanja Hägele, Stefan Zens, Caroline Vent, Moritz Hamberger, Sarah Baiker, Aron Maes, Carl-Stephan Leonhardt, Oliver Strobel, Oliver Politz, Dieter Zopf, Daniel Baumann, Julian Mochayedi, Rienk Offringa. Identification of synergistic drug combinations including MEK inhibitor and agents modulating the tumor microenvironment in an electroporation-induced pancreatic cancer model [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr B079.