Second-Generation AOH1996 Analogues with Enhanced Pharmacological Properties for Targeting PCNA

Proliferating Cell Nuclear Antigen (PCNA) plays a critical role in at least 11 distinct cellular pathways. Tumor cells express an acidic isoform of the protein (caPCNA), while nonmalignant cells express only a basic isoform (nmPCNA). We previously identified AOH1996 as a first-in-class, orally bioavailable small molecule that selectively inhibits caPCNA-mediated activities. In this study, second-generation AOH analogues with enhanced pharmacological properties were created through scaffold optimization, with AOH2.60 and AOH2.58 incorporating 3-methoxy-5-methyl substitutions (Scaffold A) and, respectively, 6-fluoro or 6-cyano on the 1-naphthoyl moiety (Scaffold D). The compounds AOH2.60 and AOH2.58 exhibited 9.6-fold and 6.6-fold increased potency across multiple cancer cell lines without affecting normal cells, and 38% and 68% greater microsomal stability relative to AOH1996, warranting further development as anticancer therapeutic agents. In cell-based assays, both compounds induced robust G2/M arrest at lower concentrations than the parent molecule and significantly enhanced transcription-replication conflicts in pancreatic cancer cells.