Evaluation of recent Protein A stationary phase innovations for capture of biotherapeutics

We describe a comprehensive evaluation of 12 Protein A stationary phases for capture of biotherapeutics. We first examine the morphological properties of the stationary phases using a variety of orthogonal techniques including electron microscopy, particle sizing, pressure-flow behavior, and isocratic pulse response. A panel of nine proteins spanning a wide range of structures and biochemical properties was then used to assess equilibrium uptake, mass transport, dynamic binding capacity, and elution pH. Process performance and product quality were also examined under realistic bioprocess conditions using clarified mammalian cell culture broth. Equilibrium isotherms were found to be highly favorable, with equilibrium binding capacity for monoclonal and bispecific antibodies ranging from 47-100 mg/mL packed bed across all stationary phases tested. Effective pore diffusivities, D_e, were obtained by fitting the chromatography general rate model to breakthrough data. The fitted D_e values for monoclonal antibodies ranged from 1.1-5.7 × 10^-8 cm²/s. The stationary phases had high dynamic binding capacities for the model proteins. The highest dynamic capacities for monoclonal and bispecific antibodies were seen with MabSelect SuRe pcc and MabSelect PrismA, which ranged from 58-74 mg/mL packed bed at 4 min residence times. Product capture using clarified cell culture broth as a feedstock showed high yields and elution pool volumes that ranged from 2-3 column volumes in most cases. Host cell protein, DNA, and aggregate levels in the elution pool were dependent on the specific nature of protein being purified, and levels were consistent between stationary phases. Lastly, we perform an analysis of bivariate correlations and discuss considerations for process design and optimization.