Energetic Dissection of Mab-Specific Reversible Self-Association Reveals Unique Thermodynamic Signatures

Purpose Reversible self-association (RSA) remains a challenge in the development of therapeutic monoclonal antibodies (mAbs). We recently analyzed the energetics of RSA for five IgG mAbs (designated as A-E) under matched conditions and using orthogonal methods. Here we examine the thermodynamics of RSA for two of the mAbs that showed the strongest evidence of RSA (mAbs C and E) to identify underlying mechanisms. Methods Concentration-dependent dynamic light scattering and sedimentation velocity (SV) studies were carried out for each mAb over a range of temperatures. Because self-association was weak, the SV data were globally analyzed via direct boundary fitting to identify best-fit models, accurately determine interaction energetics, and account for the confounding effects of thermodynamic and hydrodynamic nonideality. Results mAb C undergoes isodesmic self-association at all temperatures examined, with the energetics indicative of an enthalpically-driven reaction offset by a significant entropic penalty. By contrast, mAb E undergoes monomer-dimer self-association, with the reaction being entropically-driven and comprised of only a small enthalpic contribution. Conclusions Classical interpretations implicate van der Waals interactions and H-bond formation for mAb C RSA, and electrostatic interactions for mAb E. However, noting that RSA is likely coupled to additional equilibria, we also discuss the limitations of such interpretations.

Automated summary

This study investigated the thermodynamics of reversible self-association (RSA) for two monoclonal antibodies (mAbs C and E) showing strong evidence of RSA, using dynamic light scattering and sedimentation velocity studies. The results revealed that mAb C undergoes isodesmic self-association driven by enthalpy, while mAb E undergoes monomer-dimer self-association driven by entropy with minimal enthalpic contribution. The study also discussed the classical interpretations involving van der Waals and electrostatic interactions for mAbs C and E, respectively, as well as the limitations of these interpretations due to potential additional equilibria coupling with RSA.