Airway Transepithelial Transport of IgG Formulated with Excipients: A Case Study on What to Consider Regarding Impact on Epithelial Barrier Integrity, IgG Quality and Matrix Effects During the Analytics

Background: Surface-active excipients such as polysorbate 20 (PS20), polysorbate 80 (PS80), poloxamer 188 (Px188), and cyclodextrin (CD) are widely used to stabilize IgG formulations, including aerosols. However, their effects on transepithelial IgG transport and the reliability of associated analytical readouts remain poorly understood. Methods: Transepithelial transport of Bevacizumab was quantified across a primary airway epithelial model in the presence of clinically relevant concentrations of PS20, PS80, Px188, or CD using ELISA. Potential methodological bias was assessed by cytotoxicity and barrier integrity (Alamar Blue, LDH, TEER), IgG monomer content (SE-HPLC), micelle formation and excipient passage, and ELISA matrix effects using excipient-containing calibration curves. Results: Only CD at 10 mg/mL significantly increased IgG transport, whereas PS20, PS80, and Px188 had no significant effect. All excipients were non-toxic, with TEER being the most sensitive indicator. IgG monomer content remained unchanged under all conditions. Micelle-forming activity of PS20, PS80, and CD was retained, but only CD (10 mg/mL) crossed the epithelial barrier (11% of the initial concentration). Excipients caused concentration-dependent ELISA matrix effects; however, matrix-adjusted quantification showed only a modest, non-significant change in calculated IgG transport for CD. Conclusions: Excipients can influence in vitro IgG transport studies through biological and analytical mechanisms. Under the tested conditions, the increased IgG transport observed with CD appears to be genuine rather than assay-related, highlighting the importance of controlling excipient-related effects in mucosal IgG transport studies.