Redundancy of the OST catalytic subunit facilitates therapeutic targeting of N-glycosylation

Protein asparagine (N)-glycosylation, which promotes the folding and trafficking of cell surface receptors, has not traditionally been viewed as a viable target in oncology due to the essential and non-redundant enzymatic activities required for glycan synthesis and transfer. However, in mammals, an exception is the presence of the oligosaccharyltransferase (OST) catalytic subunit paralogs, STT3A and STT3B. In this study, we investigate the biological activity of OST inhibitors and develop a strategy for selectively inhibiting N-glycosylation that is optimized for its downstream effects on the EGFR glycoprotein. Small molecules with improved pharmacokinetic properties and selective preferences for STT3A or STT3B were synthesized, characterized in vitro, and advanced to in vivo testing. The lead compound from this series, NGI-189, induces tumor regression or growth delay in patient-derived and TKI-resistant EGFR-mutant lung cancer xenografts without causing toxicity. Collectively, these findings suggest that bioavailable OST inhibitors can be developed as therapeutic agents for oncology.