Novel PCNA inhibitor AOH1996 synergizes with KRAS-targeted therapies in pancreatic ductal adenocarcinoma

Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy driven predominantly by oncogenic KRAS mutations. Proliferating cell nuclear antigen (PCNA) is a ring-shaped clamp protein that encircles DNA and regulates replication, repair, and resolution of transcription-replication conflicts; processes hyperactivated in PDAC. AOH1996 is a first-in-class, selective PCNA inhibitor currently in Phase I clinical trials. PCNA has predicted synthetic lethal interactions with KRAS, suggesting combination potential with emerging KRAS inhibitors. This study evaluated AOH1996 alone and in combination with KRAS-targeted agents in PDAC models. Methods: In this study, we investigated the use of AOH1996 in preclinical models of KRAS-mutant PDAC. We determined cell viability and growth inhibition by MTT, colony formation and spheroid assays. Apoptosis and the cell cycle were analyzed by flow cytometry. RNA-seq, RT-qPCR and western blot were performed for mechanistic evaluations. Drug combination synergy modeling was performed using SynergyFinder. In vivo efficacy was assessed in PDAC xenograft models treated with AOH1996, KRAS inhibitors (MRTX1133, sotorasib, and RMC-6236), or combinations. Residual tumors were analyzed for pERK and pAKT signaling changes. Results: AOH1996 showed potent, dose-dependent cytotoxicity in multiple PDAC cell lines and 3D spheroids (IC₅₀: 0.5-1.5 μM). RNA-seq revealed broad transcriptional alterations, with enrichment of MAPK, PI3K-Akt and Hippo signaling pathways. Across KRAS G12C and G12D models, AOH1996 exhibited strong synergy with KRAS inhibitors, including MRTX1133, sotorasib, adagrasib, and RMC-6236. Combination therapy caused marked G1 and G2/M phase arrest, increased Annexin V-positive apoptosis, and dual suppression of pERK and pAKT. In patient-derived tumoroids, AOH1996 plus RMC-6236 significantly reduced viability compared to single agents. In vivo, AOH1996 combined with MRTX1133 or with sotorasib produced robust tumor regressions with no significant weight loss, supporting tolerability. Conclusions: AOH1996 is a promising therapeutic candidate for PDAC, demonstrating potent single-agent activity and strong synergy with clinically relevant KRAS inhibitors across in vitro, ex vivo, and in vivo models. The combination induces profound apoptotic and cell-cycle effects and disrupts key KRAS effector pathways. These results support further translational development of AOH1996-based combination regimens for patients with KRAS-mutant PDAC.