eFT508 has a half-maximal inhibitory concentration (IC50) of 1-2 nM against both MNK isoforms in enzyme assays and inhibits the kinase through a reversible, ATP-competitive mechanism of action. Treatment of tumor cell lines with eFT508 leads to a dose-dependent reduction in eIF4E phosphorylation at serine 209 (IC50 = 2-16 nM). In a panel of ~50 hematological cancers, eFT508 shows anti-proliferative activity against multiple DLBCL cell lines. Sensitivity to eFT508 in TMD8, OCI-Ly3 and HBL1 DLBCL cell lines is associated with dose-dependent decreases in production of pro-inflammatory cytokines including TNFα, IL-6, IL-10 and CXCL10.