Novel EIF4A1 inhibitors with anti‐tumor activity Free

Dysregulated protein synthesis is a hallmark of many cancers, driven by aberrant control of mRNA translation. In this study, we focus on eukaryotic translation initiation factor 4A (eIF4A), a DEAD-box ATP-dependent RNA helicase crucial for unwinding secondary structures in 5' untranslated regions (UTRs) of mRNAs, facilitating ribosomal recruitment and translation initiation. This process is particularly important for oncogenes known to have complex secondary structures, making eIF4A an attractive therapeutic target for cancer treatment. Previous efforts to inhibit eIF4A, including Rocaglamide (RocA) analogs, have shown preclinical efficacy but have been hampered by challenges in pharmacokinetics and dose-limiting toxicities in clinical trials (Chang et al., Mol Cancer Ther 2020). Zotatifin, a novel eIF4A inhibitor currently in Phase I/II trials, has aimed to overcome these limitations. However, its development has faced significant hurdles, with dose-limiting toxicities observed above 0.28 mg/kg, limiting its therapeutic window (Rosen et al., Ann. Oncol 2024). Consequently, phase II clinical trials have been paused due to safety concerns, leaving a critical gap in the availability of viable eIF4A inhibitors for therapeutic use. These challenges underscore the need for next-generation inhibitors that maintain efficacy while minimizing off-target effects and toxicity.

To address this unmet clinical need, we utilized structure-based drug screening to identify RocA-independent inhibitors of eIF4A1. Using the eIF4A::RocA::RNA complex as a template for virtual screening of the publicly available compound libraries, we performed target-based screening and pharmacophore optimization to discover two novel inhibitors, RBF197 and RBF208. These compounds inhibit eIF4A1 by stabilizing its binding to mRNA in an ATP-independent manner, preventing the helicase activity required for efficient ribosome loading. We evaluated the role of eIF4A1 in Diffuse Large B-Cell Lymphoma (DLBCL), a malignancy where dysregulated translation is particularly prominent (Kayastha, F. (2023). RNA-based Mechanisms in Cancer. World Scientific). Analysis of publicly available datasets revealed that high eIF4A1 expression correlates with poor overall survival in DLBCL patients. Immunohistochemical staining of tissue microarrays further confirmed elevated eIF4A1 levels in DLBCL tissues compared to reactive lymph nodes, supporting its role as a critical driver of disease progression and an attractive therapeutic target. Functionally, RBF197 and RBF208 demonstrated potent anti-tumor activity in DLBCL cell lines. Both compounds significantly reduced DLBCL cell viability and colony-forming potential by selectively downregulating eIF4A1-dependent oncogenes, including MYC, BCL-2, and CCND1. Remarkably, these inhibitors exhibited minimal cytotoxicity in non-malignant B cells, highlighting their selectivity for cancer cells with dysregulated translation. These findings suggest a wide therapeutic window for these inhibitors, addressing one of the key challenges in developing translation-targeting therapies (Kayastha et al., Mol Med 2022).

In preclinical in vivo models, RBF197 demonstrated robust anti-tumor efficacy. In an orthotopic, transplantable lymphoma model in immunocompetent mice, RBF197 effectively suppressed Myc-dependent tumor growth and reduced metastasis in a dose-dependent manner. Notably, RBF197 exhibited favorable pharmacokinetic properties, including an extended half-life and broad tissue distribution, with minimal off-target toxicity, particularly to the spleen and liver. These results are promising indicators of the compound's potential for clinical development.

In conclusion, our findings demonstrate that eIF4A1 is a critical driver of oncogenic translation in DLBCL and a viable therapeutic target. The discovery of RBF197 and RBF208 represents a significant advance in the field, providing new RocA-independent inhibitors with a unique mechanism of action and potent anti-tumor activity in both in vitro and in vivo models. These novel inhibitors pave the way for future bench to bedside research, offering a promising strategy to target dysregulated translation in cancer, with the potential to expand therapeutic options for patients with DLBCL and other malignancies characterized by aberrant eIF4A1 activity/expression.