Overcoming Analytical Challenges for Gene Therapies

Gene therapy developers face numerous analytical challenges, from discerning what product qualities are critical attributes to the need for fit-for-purpose analytical methods for viral vectors that offer a combination of speed, sensitivity, and resolution. Leveraging a contract research organization (CRO) partner with specialized expertise and awareness of evolving technological and regulatory development that functions as part of their customers’ internal analytical teams can lead to accelerated timelines and a higher probability of program success.

Short List of High-Level Challenges for Viral Vector–Based Therapies

Gene therapy based on viral vector delivery is still in its infancy, and like all other emerging technologies faces several high-level analytical challenges. One of the biggest is gaining the necessary depth of understanding of these novel materials. What is the best approach for analytically identifying viral vectors, and how does that approach scale so that it continues to provide valuable information? Making the right choices is central to the development of these products.

The in vivo outcomes of gene therapy drug products are becoming increasingly important in establishing the longevity and persistence of these treatments from the payer perspective. Gaining a platform understanding through detailed molecular characterization and interfacing that knowledge with clinical outcomes (safety and efficacy) is, therefore, essential, but can be difficult to achieve.

More specifically, what features of the molecules dictate both positive and negative aspects of the infectivity, productive transcription, and persistence of the therapeutic product in the body must be understood. Liquid chromatography (LC) and mass spectrometry (MS) are increasingly important because applying different methods to establish in vivo outcomes is critical.

Particular to viral vectors is the issue of full versus partial versus empty capsids. Production platforms that maximize full at the expense of partial and empty capsids are needed, as are methods for efficiently and effectively separating the desired full capsids from the undesirables.

Fortunately, because the application of analytics is really dictated by the product itself, there is a great deal of flexibility from a regulatory perspective. The key is to go back to the fundamentals of controlling quality for the purpose of known safety and efficacy, and safety is, ultimately, the priority for these products.

Analytics of Process Changes

Analytics are essential for understanding the impact of process changes on product quality attributes and safety and efficacy. Analytical tools (notably including potency assays) selected at the front end are important to enable full understanding of process changes and to correlate them with the outcomes of those assays for a limited number of batches.

With the necessity of making decisions on the basis of analysis of only a handful of samples, it is necessary to gather as much detail and establish as many correlations as possible to better control the process and outcomes. Platform methods are ideal because they enable the amalgamation of data from different batches and apply that amassed understanding in addition to the data from the actual runs under evaluation.

Evolution of Understanding

Gene therapy is not only an emerging field, but a rapidly evolving one, including from the point of view of analytics. There are some standard methods, but many methods are still evolving, and some are just being developed. In some cases, the current gold standard is not practical or appropriate, so alternatives are highly sought after, but analytical method development typically requires large sample sizes and is both time-consuming and costly. With viral vectors based on adeno-associated virus (AAV), for which more than a dozen serotypes are currently being leveraged in developmental programs, there is also the need to address serotype-specific issues.

The goal is to identify faster platform methods with sufficient resolution and sensitivity. LC- and capillary electrophoresis (CE)-based MS methods are emerging that require much smaller sample quantities and that offer much higher throughput. Work has also been conducted using ion exchange (IEX) chromatography for these purposes.

Improvements in capsid separation using these new techniques, however, are creating new questions that must be answered. Both IEX and CE-based methods reveal multiple peaks believed to represent partial capsids that have not previously been resolved. These results reflect the evolution of what is possible to monitor and what will become expected over time as understanding increases.

Wide Range of Expertise Required

While much of the initial analytical work on gene therapies was developed from a biology-focused perspective, analytical and protein chemists now have significant influence on current development and clinical thinking. In fact, the interface between this broad array of experts is critical, given the complexity of gene therapies and our current limited understanding.

For instance, while fluorescence and antibody detection are common tools for biologists, there are inherent biases in those methods for quantitation and consistency, because the xenogeneic reagent must be remade periodically. In contrast, with a chemical approach, such as MS, the right controls and approaches remain consistent for the lifetime of the product. Researchers are beginning to appreciate the advantages and disadvantages of these different approaches and how they can be used together to establish the optimum analytical package and understanding to drive gene therapy candidates forward.

As importantly, gains on the research side are translated into clinical understanding that then feeds back into the research end, enabling the design of more efficacious and practical platform solutions. Indeed, given the complexity of these products and the need to understand clinical parameters, it is essential to have more people at the table that can contribute different perspectives to the development of effective analytical solutions and strategies.

To learn how partnering with a specialized CRO can help overcome analytical challenges and increase program success for gene therapy developers, read the full article here.