Analytical methods are major quality control and integrity tools for biotherapeutic drug development. Transferring biotherapeutic characterization methods across receiving sites is rarely straightforward, warranting great attention to maintain the integrity of the methods and reliability and comparability of the data generated throughout the drug development process.
Re-optimizing the methods under new and subtly different conditions, complying with regulatory requirements, can be laborious and expensive in terms of time spent, downtime, and finances. However, this presents an opportunity to modernize the methods and better future-proof their applications.
The main challenges encountered in method transfer are around:
- emulating the method’s technical conditions and specifications in a new setting,
- providing clear protocols and standard operating procedures,
- assuring consistency in data calculations and review,
- compiling complete reports with historical data, and
- training the staff to ensure they are sufficiently knowledgeable.
Regulatory guidance on method transfer provides more information on the necessary requirements for liquid chromatography (LC) system suitability and performance, with USP chapters <621> and <1224> being two commonly used guidance. Such guidance can be used to develop risk strategies and plans to reduce risks and set out mitigating actions around method transfer.
Key factors for successful method transfer
Several key factors can help ensure the successful transfer of biotherapeutic characterization methods. These factors include simple elements, such as ensuring the utilization of the same equipment, tools, and reagents. Sourcing these components, especially the reagents, from the same vendors is also important: There may be slight variations in the raw materials and synthesis methods and tools used by different suppliers, which can impact the method transfer and re-optimization.
Ensuring robust knowledge transfer is also critical, as user errors can raise a substantial barrier to successful method transfer and modernization.
Liquid chromatography method transfer factors
Some factors are key to biotherapeutic characterization methods such as ultra-high performance liquid chromatography (UHPLC). For example, with size exclusion chromatography (SEC), these key factors include selecting the right buffer or mobile phase based on phosphate concentration, pH, salt type and concentration, and organic solvent.
A crucial element for SEC is the stationary phase, which is comprised of particles traditionally made of fully porous silica. But more recent varieties are made of impermeable silica cores surrounded by layers of fully porous silica grafted on top. These new, superficially porous particles are created using core-shell technology.
The overall hydrophobicity index of these particles varies depending on their silica content. Hydrophobicity is a key driver of how quickly and thoroughly a mobile phase passes through and elutes out of the LC column.
Another example could be the protein-stabilizing phosphate in the mobile phase, when analyzing monoclonal antibodies (mAbs) in drug development. Too much phosphate can salt out the protein, resulting in broader peaks on the chromatograph and making it difficult to analyze and characterize the mAb.
Maintaining uniformity and continuity in method transfer
It is critical to use the same type of LC column, selected for its optimal specifications for the characterization method, at the new site as part of the method transfer. And for method modernization, it is important to screen different columns to identify the candidate with the optimal combination of column length, particle size and morphology, to ensure column and method robustness.
While UHPLC with fully porous columns may be more appropriate depending on the demands and instrumentation of a particular application and laboratory, the columns based on the more recently developed core-shell technology offer certain useful benefits, such as portability with a diverse range of particle sizes, several unique phase selectivity for various applications, high efficiency at lower backpressures, and highly efficient performance, in addition to high resolution, sensitivity, and productivity.
Three key interrelated requirements need to be met, whether transferring or modernizing the biotherapeutic characterization method: The method must remain relevant, sustainable, and suitable for intended use, i.e., fit for purpose.