Abstract 682: Development of novel eIF4E inhibitors to potently and selectively suppress tumor growth across multiple indications

Abstract Despite considerable progress in treating cancer, drug resistance remains the primary hurdle to achieving cures in patients. Tumors often develop resistance through reactivation of the drug-targeted pathway, or activation of alternative parallel pathways, thereby maintaining the original downstream signaling effects. One of the furthest downstream effectors and critical nodes for many oncogenic signaling pathways is eukaryotic translation initiation factor 4E (eIF4E) ; the main regulator and rate limiting factor for protein synthesis. eIF4E is reactivated by many resistance mechanisms to promote translation of multiple pro-oncogenic factors including Cyclin D1/3, making it an attractive target to potentiate the anti-cancer activity of targeted therapies and to overcome drug resistance. Here, we present the development of novel, potent, and selective eIF4E inhibitors for use in both treatment-naïve and resistance settings across multiple tumor indications. To capitalize on the potential of targeting eIF4E, we developed a series of compounds with unique properties that maintain anti-tumor efficacy while minimizing toxicity. Our novel, selective, and potent oral eIF4E inhibitors (RBX-eIF4Ei) elicit a reversible, dose-dependent cell cycle arrest. Unlike targeting eIF4A, eIF4E inhibition selectively regulates translation of cancer-dependent pathway proteins instead of global protein synthesis, thus reducing on-target toxicity and increasing tolerability. Cellular profiling demonstrates RBX-eIF4Ei are highly selective, nanomolar inhibitors across many tumor types including, NSCLC, CRC, breast, and melanoma. Additionally, RBX-eIF4Ei demonstrate consistent efficacy across both sensitive and resistant cell lines, including intrinsic and acquired resistance models. Combining RBX-eIF4Ei with standard of care targeted therapies produces additive responses in both settings, suggesting its potential anti-neoplastic benefits post progression. In vivo, daily oral monotherapy treatment with RBX-EIF4Ei causes significant tumor growth inhibition across a variety of indications including BRAFmut CRC, BRAFmut melanoma and ER+ breast cancer, with minimal signs of toxicity. Intratumoral concentration of RBX-eIF4Ei correlate with significant tumor cell growth inhibition, as well as reductions in eIF4E target proteins, ODC1 and Cyclin D1. Combination studies with standard of care in both the treatment naïve and resistant settings are ongoing. Collectively, these data support the addition of RBX-eIF4Ei to standard of care in both the naïve and treatment resistance settings across a variety of indications including NSCLC, breast, CRC, and melanoma. IND enabling studies are planned, marking a significant step toward advancing these promising eIF4E inhibitors into clinical development. Citation Format: Matthew B. Friedersdorf, Devon R. Blake, Sarah E. Thompson, Roheeth Pavana, Ramamurty V. Changalvala, Andrew S. Truong, Krista Marran, Abha Bias, Jessica A. Sorrentino. Development of novel eIF4E inhibitors to potently and selectively suppress tumor growth across multiple indications 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 (6Suppl): Abstract nr 682.