Functional analysis of glycosylation in Etanercept: Effects over potency and stability
This study evaluated how Etanercept glycosylation contributes to biological activity and physicochemical stability by generating a panel of defined glycoforms through sequential deglycosylation. The authors produced variants by enzymatically trimming key glycan features: (1) terminal sialic acids, (2) O-linked glycans and (3) N-linked glycans, either alone or in combination to reach broader deglycosylation states. They then confirmed the specificity and completeness of each step using orthogonal analytical approaches, including Q-TOF mass spectrometry and ion-exchange profiling.
Across glycoforms, the primary mechanism of action, TNFα neutralization, remained largely unchanged and stayed within the dispersion of the neutralization bioassay. In contrast, Fc-mediated effector functions shifted with specific glycan changes. Desialylation produced a strong increase in complement-dependent cytotoxicity (CDC) potency (about a 29-fold decrease in EC50 vs the unmodified control), while full deglycosylation reduced CDC relative to the desialylated state but remained above the unmodified control. ADCC activity also increased after desialylation, while N-deglycosylation eliminated measurable ADCC in the in vitro assay format, identifying different glycan dependencies for these Fc-associated readouts.
Physicochemical testing further mapped glycan specific roles: sialic acids drove the largest charge effects (more basic pI profile), N-glycan removal produced the most pronounced loss in thermal stability (Tm decreased by ~5–6°C) and more extensive deglycosylation increased hydrophobic surface exposure and susceptibility in forced-oxidation experiments (with sialic acids and O-glycans contributing most to oxidative protection). Overall, selective glycan removal revealed that TNFα neutralization is largely resilient to major glycosylation changes, while CDC, ADCC and multiple stability metrics shift in glycan-specific ways.
Keywords: Etanercept, glycosylation, deglycosylation, sialic acids, N-glycans, O-glycans, TNFα neutralization, ADCC, CDC, thermal stability, oxidation
