High Throughput Screening of Formulations to Optimize the Thermal Stability of Therapeutic Monoclonal Antibody

Monoclonal antibodies (mAb) are progressively more important class of biotherapeutics. Antibodies are heterodimers composed of two heavy and two light polypeptide chains linked by disulfide bonds. The majority of recombinant antibodies currently under development are IgGs. Successful development of therapeutic antibodies depends not only on attainment of desired biological activities but also on physicochemical properties of these molecules, such as homogeneity, monomer oligomeric state and stability enabling manufacturing, storage and delivery. Antibody stability is affected by its formulation: ionic strength, pH, buffering substance, presence of excipients and protein concentration. Among many techniques used to study the effects of formulation on stability of antibodies, differential scanning fluorimetry (DSF) is distinguished by an unprecedented throughput and minimal material consumption. DSF measures the midpoint of unfolding transition of protein - Tm - during thermal denaturation based on the change in fluorescence intensity of environmentally sensitive dye Sypro Orange.Here, we analyzed the impact of formulation on stability of mAb1 using DSF adapted to the 96-well plate format. Two to three thermal unfolding transitions were visible for mAb1, which reproduced closely the melting profile obtained with differential scanning calorimetry (DSC). Good correlation was also observed between Tm of the main thermal unfolding transitions determined by DSF and DSC, with the former being on average lower by 3°C. Basal fluorescence of Sypro Orange was enhanced by the presence of detergents, limiting the use of this approach to the diluted detergent solutions. We have shown that low pH or high salt concentrations decreases the thermal stability of mAb1, whereas some excipients such as sucrose, methionine and phosphate buffer increase its stability. We have also shown that the throughput of DSF can be increased further with the use of 384-well plate.