Determination of protein-protein interactions in a mixture of two monoclonal antibodies

The co-formulation of monoclonal antibody (mAb) mixtures provides an attractive route to achieving therapeutic efficacy where the targeting of multiple epitopes is necessary. Controlling and predicting the behaviour of such mixtures requires elucidating the molecular basis for the self and cross protein-protein interactions, and how they depend on solution variables. While self interactions are now beginning to be well understood, there do not exist any systematic studies of cross interactions between mAbs in solution. Here, we have used static light scattering to measure the set of self and cross osmotic second virial coefficients in a solution containing a mixture of two mAbs, mAbA and mAbB, as a function of ionic strength and pH. mAbB exhibits strong association at low ionic strength, which is attributed to an electrostatic attraction that is enhanced by the presence of a strong short-ranged attraction of non-electrostatic origin. Under all solution conditions, the measured cross interactions are inter...