Long-Term Stability and Reversible Thermal Unfolding of Antibody Structure at Low pH: Case Study

We have here observed that the differential scanning calorimetry profiles and melting temperatures of a humanized antibody were unchanged over a 10-year span when stored at 4°C and at different pH values, even at pH 2.7. This is somewhat surprising, as this particular antibody undergoes conformational changes below pH 4.0. Differential scanning calorimetry analysis showed that melting of the antibody at pH 2.7 was highly reversible, suggesting a possibility that the observed reversibility is at least in part responsible for a 10-year stability at low pH. Conversely, it showed thermal unfolding followed by aggregation at higher pH.