NGI-1 is a reversible catalytic subunit inhibitor of the oligosaccharyltransferase (OST) that has higher specificity for STT3B compared to STT3A (STT: OST catalytic subunit). In non-small cell lung cancer cells NGI-1 blocks cell surface localization and signaling of the EGFR glycoprotein, but selectively arrests proliferation in only those cell lines that are dependent on EGFR (or FGFR) for survival. In these cell lines OST inhibition causes cell cycle arrest accompanied by induction of p21, autofluorescence, and changes in cell morphology; all hallmarks of senescence. NGI-1 exhibits broad antiviral activity against multiple flaviviruses. It blocks viral RNA replication independent of inhibition of the catalytic activity of the OST complex.
