Abstract 5480: Aristolochic acid as a scaffold for antitumor drug development

Abstract We have synthesized an analog of aristolochic acid (AA) with potent growth inhibitory activity in various human cancer cell lines and report here on mechanistic studies of this potential therapeutic. AA is a natural product and the main active principle of Aristolochia plants, a known source of antitumor agents. In 1964 due to nephrotoxicity, drug development efforts with AA were terminated following Phase I clinical trial in patients with terminal cancer of different origin. Structure activity studies of AA species allowed us to select a structural analog of AA (RJ-34) that lacks the determinants responsible for the renal toxicity and carcinogenicity of the parent compound. Building further on our experience with AA molecules, we developed a synthetic approach that affords efficient high-yield synthesis of RJ-34. Its structure and purity has been confirmed by high-performance liquid chromatography, liquid chromatography coupled with two-stage mass spectrometry and high resolution nucleic magnetic resonance. Sulforhodamine B assay revealed that RJ-34 has growth inhibitory activity in A549 and HCT-15 human cancer cell lines comparable to or stronger than that of paclitaxel or topotecan. At five nanomolar, RJ-34 inhibited DNA synthesis and cut the growth of A549 cells by 50%, leading to cell cycle arrest in G1/M and G2/S, with apparent apoptosis at concentrations greater than 200 nanomolar. Notably, protein synthesis in cultured cells, as evaluated by puromycin labelling, remained unaffected. RJ-34 was screened against the NCI-60 cell line panel - encompassing sixty human cancer cell lines from various tissues - providing clues to its mechanisms of action; namely, that RJ-34 acts through inhibition of DNA topoisomerases I and II and/or DNA intercalation. Follow-up studies using purified calf Topo I and human Topo II alpha and various plasmid substrates confirmed the role of RJ-34 as a DNA intercalator and human Topoisomerase II alpha poison. The pattern of activity of RJ-34 in the NCI-60 panel was distinct from that of AA and aristolactam - another related compound - suggesting that RJ-34 acts by mechanisms distinct from AA. In summary, RJ-34— a non-nephrotoxic analog of aristolochic acid— has a potent growth inhibitory activity in various human cancer cell lines with a mechanism of action different from the parent AA. Moving forward, pre-clinical pharmacokinetics, safety and efficacy studies are necessary to establish the potential of RJ-34 for development as an anticancer therapeutic. Citation Format: Keiji Hashimoto, Rajesh Chennamshetti, Radha Bonala, Francis Johnson, Arthur P. Grollman, Viktoriya S. Sidorenko. Aristolochic acid as a scaffold for antitumor drug development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5480.