Abstract 5964: Design and anticancer biological evaluation of novel 7-aza-8,9-methylenedioxyindenoisoquinoline derivatives that inhibit MYC and topoisomerase I
Authors: Han Yichen , Chen Luying , Buric Adam , Chintareddy Venkat , Chand Pooran , Riggs Randall , Cushman Mark , Yang Danzhou 
Published: March 2024

Abstract
MYC is one of the most validated driver oncogenes and is overexpressed in most human cancers. However, the MYC protein is considered “undruggable” due to its disordered structure and difficulties associated with targeting transcription factors. The MYC gene promoter forms G- quadruplex, a four-stranded non-canonical DNA secondary structure. The MYC G-quadruplex functions as a transcription silencer and further inhibits MYC expression upon drug binding, representing an exciting approach for MYC-targeting cancer therapy. Indenoisoquinolines are topoisomerase I inhibitors with better physicochemical and biological properties than the clinical camptothecin drugs. We previously revealed a novel mechanism of action for active anticancer indenoisoquinolines by dual inhibition of MYC and topoisomerase I, where potent MYC inhibition was achieved through targeting its promoter G-quadruplex. Herein, we report the design, cellular activity, and in vivo efficacy of novel anticancer 7-aza-8,9-methylenedioxyindenoisoquinoline derivatives based on optimized substituents and π-π stacking interactions. Using biophysical, biochemical, and cellular assays, we demonstrated that the new indenoisoquinoline derivatives greatly stabilized the MYC promoter G-quadruplex, significantly lowered MYC protein and mRNA levels in cancer cells, and inhibited topoisomerase I activity. A MYC G-quadruplex mediated mechanism of action was evident by differential activities in Raji vs CA-46 cells. The importance of MYC targeting was corroborated by potent cytotoxicity against a panel of MYC-dependent cancer cell lines as well as the NCI-60 panel of human cancer cell lines. The top three candidates were evaluated for pharmacokinetics and in vivo anticancer properties. Excellent metabolic stability, bioavailability, and tumor accumulation were observed in xenograft mouse models. Potent and significant tumor growth inhibition was demonstrated in the aggressive RD-ES Ewing Sarcoma xenograft mouse model while the drugs were well-tolerated. In addition, favorable brain penetration and pharmacokinetics were established, which encourage future evaluations in difficult-to-treat brain tumors. In conclusion, we designed and developed 7-aza-8,9-methylenedioxyindenoisoquinoline derivatives that are dual inhibitors of MYC and topoisomerase I. Our drug candidates demonstrated excellent pharmacokinetics and in vivo anticancer activities with promising indications in MYC-dependent cancers.
Citation Format: Yichen Han, Luying Chen, Adam Buric, Venkat Chintareddy, Pooran Chand, Randall Riggs, Mark Cushman, Danzhou Yang. Design and anticancer biological evaluation of novel 7-aza-8,9-methylenedioxyindenoisoquinoline derivatives that inhibit MYC and topoisomerase I [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5964.