Insight

Chromatographic processes have become an indispensable unit operation in biopharmaceutical manufacturing, and chromatography resins thus serve as critical raw materials in biopharmaceuticals. Validation associated with chromatography resins represents the most pivotal and complex component of process validation, as it spans all phases of process validation, including process characterization, process qualification, and continued process verification (CPV).

A typical chromatographic process consists of two core segments: chromatography process operational procedures and chromatography process maintenance procedures. Process parameters of both segments exert impacts on the quality and safety of processed drug products, thereby both requiring validation within the process validation framework.

PDA Technical Report No. 14, Validation of Column Chromatography Processes, summarizes the research, validation and scale-up requirements for chromatography resins. Certain validation activities shall be performed at commercial manufacturing scale, while others can only be implemented using scaled-down models.

The objective of chromatographic process characterization is to investigate the impacts of chromatographic operational parameters on process performance and product quality, so as to define critical process parameters (CPPs) along with their set points and acceptable ranges. Prospective studies are generally conducted via scaled-down models.

Data and outcomes generated from process characterization constitute an integral part of the process control strategy. Process Performance Qualification (PPQ) verifies the operability and robustness of such control strategy, laying a solid foundation for Biologics License Application (BLA) submission.

As a critical raw material, batch-to-batch variability of chromatography resins acts as a major source of process variation and shall be incorporated into process characterization. Methodologies such as robust parameter design can be adopted for this purpose.

The impurity removal capacity of chromatography resins in biopharmaceutical processes shall be investigated and confirmed. It is essential to clarify the impurity clearance capability of each individual chromatographic unit operation, which is normally achieved by tracking impurity removal profiles during PPQ campaigns.

For certain process steps, direct tracking of impurity clearance fails to accurately reflect the actual removal capability due to low inherent impurity levels or limited analytical method sensitivity. In such cases, spiking challenge studies are required. Since exogenous impurities need to be introduced into the chromatographic system, challenge studies are exclusively performed on scaled-down models.

PDA Technical Report No. 60-3, Process Validation for Biopharmaceutical Drug Substances, emphasizes the validation of chromatographic resin maintenance procedures. It specifies that this section primarily covers resin lifespan validation, cleaning validation, and storage validation.

Resin lifespan validation demonstrates that chromatography resins can maintain acceptable performance characteristics within the intended service life and consistently manufacture drug products complying with quality specifications. Lifespan validation is conducted on scaled-down models, which can adopt the qualified models established during process characterization (already proven representative of commercial-scale processes).

Blank runs can be designed and implemented throughout resin lifespan validation. As interpreted in PDA Technical Report No. 14, a blank run refers to replacing loaded feedstock with equilibration buffer (or Water for Injection, WFI) while keeping all other chromatographic steps unchanged, followed by collection and testing of elution fractions. Blank runs enable assessment of residue accumulation effects over the resin lifespan.

The purpose of cleaning validation is to demonstrate that the defined cleaning procedure can minimize residual contaminants between consecutive production batches. Development of resin cleaning procedures is generally completed on scaled-down models, whereas formal cleaning validation typically combines data from scaled-down models and commercial manufacturing scale.

Scaled-down cleaning validation is performed concurrently with resin lifespan validation. However, scaled-down models have inherent limitations in representing commercial cleaning performance; hence, commercial-scale data is mandatory to verify the effectiveness of cleaning procedures, which can be synchronized with PPQ execution.

Common approaches for resin cleaning validation include the rinse water method and blank run method. Testing indicators cover Total Organic Carbon (TOC), total protein content, and process-specific impurities such as Host Cell Protein (HCP) and Host Cell DNA (hcDNA). Acceptance criteria generally follow industrial benchmarks (e.g., 10 ppm for TOC). Enterprises may also establish customized specifications, especially for process-related specific impurities.

Although resin suppliers provide data regarding shelf life, bacteriostatic and antifungal properties of storage solutions, in-house storage validation is still indispensable. This is because supplier-provided storage data is generated using fresh unused resins under bulk storage conditions.

In actual biopharmaceutical manufacturing, resins are mostly stored after production use, frequently in on-column storage mode. Resin storage validation shall fully take such practical production conditions into account. A practical example of resin storage validation is illustrated below.

Following BLA regulatory approval, a dedicated CPV protocol for chromatography resins shall be established to sustain the validated and controlled state of resins at commercial scale, covering resin lifespan consistency, impurity clearance performance, residue accumulation control, viral clearance capability and other key attributes.

For resin lifespan monitoring, continuous tracking of step yield, process-related impurities and product-related impurities is required to confirm resin and process performance remain within the qualified lifespan boundaries. Cleaning status is monitored on an ongoing basis via critical cleaning process parameters. Periodic commercial-scale blank runs (e.g., once per 10 production batches) can be implemented to continuously verify cleaning procedure effectiveness.

In addition, a formal change control procedure shall be established to document and implement any changes impacting the controlled status of chromatography resins.

Validation activities for chromatography resins run through the entire lifecycle of process validation, integrating scaled-down model & commercial-scale studies, as well as prospective validation and concurrent validation approaches. This article systematically elaborates the core elements of chromatography resin validation, which aligns with mainstream industrial practices and fully meets global regulatory expectations.