Design Space Identification (DSpI) enables the Quality by Design (QbD) framework by evaluating and representing feasible regions of operations that meet quality constraints [1]. In biopharma, QbD is fundamental in streamlining the design process and guaranteeing process robustness and reliability. Protein A chromatography is the most resource-intensive step in typical biopharma downstream processing and possibly the main process bottleneck [2]. The application of QbD at this step enables a rigorous rationale on how to systematically tackle the causes that limit the process efficiency and effectiveness and provide a clear indication of how to approach and reduce them [3].
The traditional approach to design space identification typically comprises an initial mechanistic modelling step, where either a new model is created for the system under investigation or an off-the-shelf existing model is reparametrized. Such an approach enables the application of model-based design space identification strategies that provide high accuracy [4, 5]. The main challenge of this approach is related to the mechanistic modelling stage, which might require extensive experts’ time and effort. In fact, it is not always the case that such experts are readily available in-house.
To address these issues, a valid alternative route is to employ a data-driven approach directly harnessing the available data. Naturally, this approach relies heavily on the quality and quantity of data itself. If the data is sufficiently good and enough, then the data-driven DSpI strategy enables a rapid and efficient way of applying the QbD framework.
In this work, we propose a data-driven DSpI methodology based on machine learning that utilizes artificial neural network classifiers to distinguish between feasibility and infeasibility regions. The methodology is systematically applied to different experimental scenarios with varying data quality and quantity to determine its effectiveness. Thus, the role of data quality and quantity is investigated to assess how robust and accurate the machine learning-based approach is in predicting the design space.
The experimental setup analysed is that of an industrial Protein A chromatography column for monoclonal antibodies separation using the MabSelect™ Sure™ resin. Additionally, transfer learning is implemented to support the data-driven approach in data-scarce scenarios to boost the reliability and accuracy of the design space predictions. Its application involves an initial training of the artificial neural network on the mechanistic model of Grom et al. [6], developed and validated for Protein A chromatography, and a final specialization on the target system under investigation. Transfer learning is able to extract intrinsic knowledge from the mechanistic model that has not been parametrized or adapted to the current system investigated and to enhance the predictive accuracy and reliability of the DSpI in data-scarce scenarios.
Acknowledgements
Funding from the UK Engineering & Physical Sciences Research Council (EPSRC) for the i-PREDICT:Integrated adaPtive pRocEss DesIgn and ConTrol (Grant reference: EP/W035006/1) is gratefully acknowledged.
References
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