A mechanistic model has been developed for hydrophobic interaction chromatography (HIC) based purification of monoclonal antibodies (mAbs). The model has been used to gain thorough process understanding as desired by the quality by design paradigm. The model is based on the general rate model coupled with exponentially modified Langmuir adsorption model. The latter has been modeled by using the solvophobic theory for correlating protein adsorption equilibrium on the hydrophobic media to the mobile phase salt concentration.
The proposed model satisfactorily predicts the elution profile of the monoclonal antibody product under consideration and its aggregates on HIC column (Phenyl Sepharose 6 Fast FlowTM low sub) operated in linear gradient mode. The model has been used to elucidate the underlying mechanism behind separation of monomer and aggregate species. A comparison of the relative time scales for the various mass transfer events for mAb and aggregate species indicates that the intra‐particle (pore) diffusion transport of these molecules to their respective binding sites within the porous HIC resin is the rate limiting step whereas convection, film diffusion, and binding kinetics are relatively faster (time scales are 10−1 to 10−3 order of magnitude times the time scale of intra‐particle pore diffusion).
The proposed methodology for modeling can be successfully implemented for achieving efficient aggregate removal by HIC using minimal experimentation as compared to the traditional experimentally extensive approaches.