The nonglycosylated variant in therapeutic monoclonal antibodies preferentially forms large aggregates under typical thermal stresses used in forced degradation studies

Monoclonal antibodies (mAbs) feature a conserved N-linked glycosylation site in the CH2 domain, which exhibits heterogeneities in both occupancy and glycan structures. Previous studies have suggested that the unoccupied (nonglycosylated) variant exhibits decreased thermal stability, potentially impacting the overall stability of mAb products. This hypothesis, however, has remained largely unconfirmed, due to the low abundance of nonglycosylated variants in typical mAb products and the lack of effective analytical tools for detailed characterization of large aggregates with glycoform-specific information. Here, we used a postcolumn denaturation-assisted size exclusion chromatography mass spectrometry technique (SEC-PCD-MS) to reevaluate the effects of the nonglycosylated mAb variant on the thermal stability of mAb drugs during forced degradation studies. Our findings confirmed the compromised thermal stability of the nonglycosylated variant and its increased propensity to form large aggregates at elevated temperatures relevant to mAb-forced degradation studies. We also showed that this thermal stress-induced, nonglycosylation-mediated aggregation pathway could be widely observed in a diverse group of mAb molecules with varying properties. This study offers valuable insights into the rationale of selecting the appropriate temperature for mAb-forced degradation studies and highlights key considerations for data interpretation.