Introduction
Commercializing cell and gene therapies (CGTs) is a prominent challenge and goal for the pharma industry facing patent cliffs and other regulatory headwinds. These novel medicines have rapidly advanced to the stage where both efficacy and safety has been achieved in the clinic. Unfortunately, current processes of manual, labor-intensive, open lab-scale manufacturing solutions for viral vector production and genetic modification of cells are not practical to quickly scaling and commercializing these innovations.
Equipment vendors, raw material suppliers and drug developers are working together to address these issues. While some challenges, such as scalability and capacity are well-known, others just as critical to timelines have received minimal attention. Even when the goal is first-in-human-studies to demonstrate a proof of concept, companies need to stay focused on striving for a right-the-first-time approach in their process development efforts. These efforts can be internal or by served by an experienced contract development and manufacturing organization (CDMO).
Investing in robust cell lines
Most viral vectors are currently produced in human HEK 293 cells. In general, these cells are not designed to make viruses and require additional helper function using recombinant techniques. To do this properly, time must be invested in developing robust cell lines to consistently achieve the yield, quality and potency required. Having these robust cell lines offers stability and high viral production capacity, which is essential to a streamlined process. Rather than using multiple different cell lines with limited viral production abilities, it is better to take the time to understand the specific viral vector requirements and develop a well-characterized cell line that can meet expected production demand.
Starting with good plasmids
The emerging best approach for proper sequencing of plasmids is using next-generation sequencing (both long and short read sequencing) to efficiently validate sequence integrity of plasmid ITRs and LTRs. This delivers a clear picture of genetic sequencing information encoded within these plasmids. ITRs and LTRs determine not only the packaging of DNA for the virus (full vs. partial vs. empty capsids), but also the in vivo potency and long-term stability of the resulting gene or gene-modified cell therapy. In addition, when plasmids are produced in suboptimal bacterial strains, the master cell bank can contain undesirable, low-level sequence variants that are not detectable using only Sanger sequencing.
Exploring the entire formulation space
When gene therapy formulation is an afterthought, it can cause unexpected time and expense on the back end for reformulation or further process development. Effective formulation of gene therapy products prior to phase 1 trials is the best strategy for overcoming these challenges. It is particularly useful to have extensive experience working with different adeno-associated virus (AAV) serotypes and other viral vectors. This knowledge can be leveraged to predict which excipients will afford the optimum formulation.
Monitoring subvisible particles
Gene and gene-modified cell therapy developers should monitor the presence of subvisible particles beginning at the earliest development stages. As drug products move to later development stages, regulatory expectations regarding subvisible particles (which have immunogenicity potential that can lead to drug degradation) become stricter and more extensive. The best approach is to determine how filtration, dilution and other unit operations affect subvisible particle generation at the beginning of process development. Applying this knowledge throughout the later stages of development can help avoid issues associated with excessive subvisible particle content in the final product.
Building flexible manufacturing solutions
Ideally, during early phase development, multiple scenarios are simulated with respect to potential dosage demand. The key is to find the optimum balance between what might be needed for the clinical studies and what is possible on the manufacturing floor. That is not always obvious, because the cells used to produce these autologous gene-modified cell therapies come from very sick patients and don’t always grow well. A modular approach to drug product presentation helps to address clinics’ need for access to the exact volumes of products required for infusion. It allows delivery of the specific dosages needed throughout the entire dose-escalation study as efficiently as possible.
Bridging the analytics gap
Including analytics from bench-top technology development through GMP manufacturing accelerates process development and scale-up. Advanced analytical techniques - including proteomics, mass spectrometry and other very detailed, high-sensitivity, high-accuracy methods - help drug developers understand how changes to the process impact post-translational modifications (glycan modifications, deamidation, etc.), viral particle stability, contamination profiles (host-cell DNA, host-cell proteins, etc.) and other product attributes. This knowledge is crucial to enabling the development of robust, highly reproducible, high-yielding processes that afford high-quality cell and gene therapy products. With integrated analytics on site, products and processes are well characterized and well validated and specialized formulation solutions are not needed to compensate for performance issues.
Working towards industrialization
The ability to access next-generation technologies via a CDMO can also be beneficial to drug developers. CDMO activities are built around the mindset of achieving better process and product characterization using an integrated analytics approach that helps to continue building knowledge of the product attributes that are critically important to mitigating risk and ensuring success for CGTs at any quantity.
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