Development of a Direct-to-Biology Platform to Discover Potent MNK Inhibitors

Eukaryotic translation initiation factor 4E (eIF4E) plays an essential role in driving the translation of mRNAs that promote cell proliferation. Its activity is regulated through phosphorylation at Ser209 by MNK1/2 kinases, which are downstream effectors of mitogen-activated protein kinase signaling. Elevated eIF4E phosphorylation drives malignant progression in multiple cancers, including glioblastoma, where it promotes translation of key oncoproteins responsible for tumor growth and therapy resistance. Here, we report the development and application of a direct-to-biology (D2B) platform to rapidly optimize new MNK inhibitors for cellular inhibition. This approach combines plate-based library synthesis with an in-cell Western assay to efficiently generate structure-activity relationship (SAR) data and new compounds with potent cellular inhibition. Using this platform, we synthesized and tested >150 new analogs directly in cells, identifying inhibitors with IC₅₀ values as low as 23 nM in LN229 cells. This work establishes a D2B approach as an effective strategy for efficient kinase inhibitor optimization.