Next-Generation Imipridones ONC206 and ONC212 Synergize with Lurbinectedin in Killing Pancreatic Ductal Adenocarcinoma Cells

Pancreatic ductal adenocarcinoma (PDAC) is a devastating malignancy with a five-year survival rate of approximately 13%, underscoring the urgent need for novel therapeutic strategies. Next-generation imipridones ONC206 and ONC212 are potent anticancer agents that activate the mitochondrial ClpP protease and the integrated stress response. Lurbinectedin, an FDA-approved therapy for metastatic small cell lung cancer, inhibits transcription by binding the DNA minor groove and has demonstrated preclinical efficacy in PDAC models. Here, we show that ONC206 and ONC212 are highly cytotoxic against PDAC cell lines as monotherapies and in combination with lurbinectedin. Both ONC206 and ONC212 achieved sub-micromolar seventy-two-hour IC values in BxPC-3, PANC-1, and HPAF-II PDAC cells, with ONC212 exhibiting greater potency across all lines. Mechanistically, ONC206 and ONC212 induce apoptosis through ClpX depletion, ATF4 induction, and caspase-mediated PARP cleavage. Combination treatment of lurbinectedin with both imipridones produced robust synergy, with ONC212 generally exhibiting stronger synergy at lower concentrations and HSA synergy scores up to 29.5. Importantly, these combinations showed minimal toxicity in CCD 841 CoN non-malignant colon epithelial cells, indicating selective tumor cell killing. Western blot analysis revealed that synergy between lurbinectedin and ONC212 is associated with upregulation of DR5 and downregulation of Bcl-2 and ClpX. These findings provide mechanistic and preclinical support for combining lurbinectedin with next-generation imipridones as a therapeutic strategy in PDAC.