Abstract 607: Development of a novel, selective, and potent inhibitor of RON kinase
Authors: Kaadige Mohan Rao , Thode Trason , Fornetti Jaime , Weston Alexis , Ng Serina , Ghosh-Halder Tithi , Bargenquast Taylor , Durbin Brian , Kasibhatla Srinivas , Soldi Raffaella , Welm Alana , Sharma Sunil 
Published: March 2024

Purpose: Receptor d’origine nantais (RON) is a highly conserved transmembrane protein expressed at low levels in healthy adult tissues of epithelial origin and at various levels in immune cells such as macrophages. Aberrant activation of RON has been described in many solid tumors, and it contributes to tumorigenesis by modulating the immune tumor microenvironment, activating numerous oncogenic signaling pathways, and protecting tumor cells under stress. The overexpression of RON protein and the subsequent generation of oncogenic variants are mainly responsible for the persistent activation of downstream signaling pathways. In breast cancer, more than 80% of primary cancer samples are positive for RON expression, with overexpression reported in approximately 50% of cases. Importantly, tumoral RON expression correlates with increased breast cancer progression, metastasis, and poor prognosis independent of molecular subtype. We hypothesize that a small molecule inhibitor of RON that can target both full-length and truncated isoforms will promote anti-tumor immunity within the tumor microenvironment and block pro-metastatic signaling pathways. Herein, we report the development of a novel, orally bioavailable, selective, and potent inhibitor of RON kinase.

Methods: With structure-guided and iterative medicinal chemistry approaches, we identified a novel chemical entity that potently inhibited RON kinase activity. Further optimization resulted in the identification of ZB-60 with improved potency, selectivity, and desirable drug-like properties. In vitro kinase assays were performed using ADP-Glo RON kinase assay kit (Promega). Changes in phosphorylation of RON was demonstrated by Western blotting. Plasma pharmacokinetics (PK) was conducted in mice to measure exposures and to determine the oral bioavailability of ZB-60. In vivo efficacy of ZB-60 was evaluated in syngeneic mouse models of breast (EMT6) and colorectal (CT26) cancer.

Results: ZB-60 inhibited RON kinase activity with an IC50 of 56 nM and showed greater than 40-fold selectivity against MET and other closest members of the tyrosine kinase family. In ZB-60 treated breast cancer cells, there was a dose dependent reduction of RON phosphorylation and downstream signaling. PK analysis showed a high oral bioavailability with low clearance. In vivo evaluation of ZB-60 showed inhibition of tumor growth in EMT6 and CT26 models. Ongoing studies are focused on testing ZB-60 in combination with checkpoint inhibitors. The results from these studies along with ADME-TOX and pharmacokinetics will be presented.

Conclusion: ZB-60 has target specific activity and exhibits favorable drug-like properties.

Citation Format: Mohan Rao Kaadige, Trason Thode, Jaime Fornetti, Alexis Weston, Serina Ng, Tithi Ghosh-Halder, Taylor Bargenquast, Brian Durbin, Srinivas Kasibhatla, Raffaella Soldi, Alana Welm, Sunil Sharma. Development of a novel, selective, and potent inhibitor of RON kinase [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 607.