Tomivosertib (eFT508) is a potent, highly selective, and orally active MNK1 and MNK2 inhibitor, with IC50s of 1-2 nM against both isoforms. Tomivosertib (eFT508) treatment leads to a dose-dependent reduction in eIF4E phosphorylation at serine 209 (IC50=2-16 nM) in tumor cell lines[1]. Tomivosertib (eFT508) also dramatically downregulates PD-L1 protein abundance[2].