Inhibition of agitation-induced aggregation of an IgG-antibody by hydroxypropyl-beta-cyclodextrin

In order to provide an alternative to nonionic surfactants as excipients for protein formulations, cyclodextrin-derivatives (CDs) were examined for their potential to inhibit agitation-induced aggregation of an IgG in aqueous solution. Loss of monomeric protein and protein aggregation were monitored throughout the agitation experiments by size exclusion chromatography. Hydroxypropyl-beta-cyclodextrin (HPbetaCD) completely suppressed IgG-aggregation at a remarkably low concentration (2.5 mM) and in contrast to other CDs it also did not negatively affect IgG-stability during storage in nonagitated solution. Further agitation experiments demonstrated the superiority of HPbetaCD to other common excipients in protein formulation, such as sugars and sugar alcohols or polysorbate 80 in low concentrations. Spectroscopic (fluorescence spectroscopy and Fourier transform infrared spectroscopy), thermodynamic (microcalorimetry), and physical investigations (surface tension measurements) were carried out to elucidate the mechanism of stabilization of the IgG. In contrast to other studies with HPbetaCD, protein stabilization could not be attributed to direct interaction between hydrophobic amino acids on the IgG and this excipient. Competition with the protein for the air-water interface appears to be the dominating mechanism of stabilization.