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ABSTRACT
Excipients are added to biopharmaceutical formulations to enhance protein stability and enable the development of robust formulations with acceptable physicochemical properties, but the mechanism by which they confer stability is not fully understood. Here, we aimed to elucidate the mechanism through direct experimental evidence of the binding affinity of an excipient to a monoclonal antibody (mAb), using saturation transfer difference (STD) nuclear magnetic resonance (NMR) spectroscopic method. We ranked a series of excipients with respect to their dissociation constant (KD) and nonspecific binding constants (Ns). In parallel, molecular dynamic and site identification by ligand competitive saturation (SILCS)-Monte Carlo simulations were done to rank the excipient proximity to the proteins, thereby corroborating the ranking by STD NMR. Finally, the excipient ranking by NMR was correlated with mAb conformational and colloidal stability. Our approach can aid excipient selection in biologic formulations by providing insights into mAb–excipient affinities before conventional and time-consuming excipient screening studies are conducted.
Abbreviations
| At | = | attenuation |
| B22 | = | second osmotic virial coefficient |
| BMSmAb | = | Bristol Myers Squibb mAb |
| CD | = | circular dichroism |
| CGenFF | = | CHARMM general force field |
| D2O | = | Deuterium oxide |
| DTPA | = | diethylenetriaminepentaacetic acid |
| EDTA | = | Ethylenediaminetetraacetic acid |
| FTIR | = | Fourier transform Infra-Red |
| GCMC | = | grand canonical Monte Carlo |
| GFE | = | grid-based free energy |
| ITC | = | isothermal titration calorimetry |
| KD | = | dissociation constant |
| LGFE | = | ligand grid free energy |
| Lp | = | laser power |
| mAb | = | monoclonal antibody |
| MC | = | Monte Carlo |
| MD | = | Molecular dynamic |
| MOE | = | Molecular Operating Environment |
| NAMD | = | Nanoscale Molecular Dynamics |
| nanoDSF | = | nano differential scanning fluorimetry |
| NMR | = | nuclear magnetic resonance |
| Ns | = | nonspecific binding constant |
| PPI | = | protein-protein interactions |
| SILCS | = | Site Identification by Ligand Competitive Saturation |
| SLS | = | static light scattering |
| STD | = | saturation transfer difference |
| STDaf | = | STD amplification factor |
| Tm | = | mid-point of thermal transition |
| TSP | = | sodium trimethylsilyl propionate |
| VMD | = | Visual Molecular Dynamics |
Acknowledgments
The authors would like to thank Janet Cortes, Tracy Gaebele and Arvind Mathur for this collaboration opportunity, and Dilbir Bindra for valuable discussions on expanding this work.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary material
Supplemental data for this article can be accessed online at https://doi.org/10.1080/19420862.2023.2212416.