The CDC42 family of GTPases (RHOJ, RHOQ, CDC42) control both the ability of tumor cells to invade surrounding tissues and the ability of endothelial cells to vascularize tumors. While recent studies have developed small molecules that target RAS GTPases, little progress has been made in targeting the related CDC42 family of GTPases for cancer treatment. Here, we use computer-aided drug design to identify a novel class of inhibitors that act on an allosteric pocket in the active form of the CDC42 GTPase, RHOJ. These allosteric inhibitors prevent RHOJ and CDC42 from binding to their downstream effector PAK, while having no effect on the interactions between the closely related GTPase RAC1 and PAK or RAS and its downstream effector RAF. Our lead compound ARN22089 has a druglike profile and can block both tumor growth and tumor angiogenesis in a three-dimensional vascularized microtumor (VMT) model, indicating that ARN22089 blocks RHOJ/CDC42 signaling in both the tumor cell and the tumor endothelium. Short term treatment of nascent melanoma tumors with ARN22089 halted the growth of BRAF mutant autochthonous mouse melanoma tumors, slowed the growth of melanoma patient-derived xenografts, and induced tumor necrosis in PDX models. In summary, we describe a multidisciplinary structure-based drug discovery platform that can identify new RHO family allosteric inhibitors and use this system to identify RHOJ inhibitors that block tumor growth in vivo.

Citation Format: Jessica L. Flesher, Sohail Jahid, Jose A. Ortega, Giuseppina La Sala, Nicoletta Brindani, Jose M. Arencibia, Jacopo Manigrasso, Stephanie Hachey, Chi-Fen Chen, Chris Hughes, Marco De Vivo, Anand K. Ganesan. Structure-based design of CDC42/RHOJ effector inhibitors for the treatment of cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5324.