Preclinical Development – Biomolecular
2019 PharmSci 360
DART® molecules are bispecific antibodies that bind two targets simultaneously. Biophysical evaluation of a bispecific DART molecule “A” was performed to elucidate the effects of temperature, pH, ionic strength, protein concentration, and buffer excipients on reversible self-association (RSA). Sedimentation Velocity -Analytical Ultracentrifugation reveals that high molecular weight species of molecule “A” at 37 °C are reversible dimers that are antibody concentration and ionic strength-dependent. Addition of salt to molecule “A” led to decreased RSA, due to increased colloidal stability. The RSA observed in molecule “A” is atypical of proteins, where high salt content tends to decrease the like charge repulsions between proteins that favor colloidal stability. Moreover, RSA is thermally reversed in molecule “A” at lower 4 ⁰C temperature, in contrast to monoclonal antibodies, for which lower temperatures favor RSA. The effects of these temperature-dependent attractive protein-protein interactions on solution viscosity of molecule “A” will also be presented.