Ion-exchange chromatography (IEC) is universally accepted as the optimal method for achieving process scale separation of charge variants of a monoclonal antibody (mAb) therapeutic. These variants are closely related to the product and a baseline separation is rarely achieved. The general practice is to fractionate the eluate from the IEX column, analyze the fractions offline and then pool the desired fractions to obtain the targeted composition of variants. This is, however, a very cumbersome and time consuming exercise. A mechanistic model that is capable of simulating the peak profile will be a much more elegant and effective way to make a decision on the pooling strategy if implemented as a PAT tool. This work proposes use of a mechanistic model for enabling PAT for making online pooling decision to obtain desired composition of product in terms of its charge variants. The mechanistic model is based on the general rate model, to predict elution peak profile for separation of the main product from its variants. The packed bed column has been modelled along with the chromatographic system consisting of the mixer, tubing and detectors as a series of dispersed plug flow and continuous stirred tank reactors which gives the flexibility to obtain model parameters by inverse fit of process chromatogram. Five batches having different composition of charge variants have been used to demonstrate pooling strategy based on simulated chromatogram and compared to offline pooling based on fractionation. Further, to establish the robustness of method, variations in flow rate (150- 300 cm/h), product load capacity (15-28 mg/mL), and rate of elution gradient (20 - 40 CV) have been tested. In all the conditions examined, the variations in mechanistic pooling strategy to the offline method has been found to be less than 5%. Simulation of process chromatogram has been achieved in couple of minutes so as to make implementation possible. We think that the approach followed in this study can be extended to any mAb product and that the proposed process would have a great appeal to those interested in PAT implementing for bioprocessing.

Application of mechanistic modeling for enabling PAT in process chromatography: Separation of charge variants of mAbs by ion exchange chromatography

251st National Meeting (2016)

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