Modeling retention time distribution in continuous Protein A affinity capture for materials traceability and...

The biopharmaceutical industry is increasingly shifting from batch processing to continuous manufacturing. The ICH Q13 guideline outlines regulatory considerations for the implementation of continuous manufacturing with emphasis on material traceability. Although continuous capture with Protein A affinity chromatography is widely used, the aspect of material traceability remains underexplored. In this study, a retention time distribution (ReTD) model for a twin-column continuous capture process was developed, building on the single column model and the connection condition of the process to enable material traceability. The ReTD behaviors during the startup, interconnected load and disconnected load steps were simulated, focusing on how the material are distributed in the elution peaks across subsequent switches. These simulations were validated through tracer experiments using fluorescently labeled proteins as inert tracer, showing good agreement between the model predictions and experimental results. This observed ReTD behavior is attributed to the combination effects of breakthrough dynamics, exchange effects, and operational step changes. Based on the developed ReTD model, a method for materials traceability and diversion was proposed. The ReTD behavior for materials with extended durations can be extrapolated from materials with duration shorter than one switch, owing to the periodic nature of the continuous capture process. This ReTD-based approach allows for the tracking and evaluation of disturbance entering the system at any time, as well as their persistence for varying durations. These materials can then be diverted according to the acceptable limits, facilitating real-time product release. The proposed ReTD-based method offers a practical solution for ensuring material traceability and diversion, helping meet regulatory requirements and improving real-time product release in continuous capture processes.