While most cell therapies are autologous products, allogeneic approaches continue to advance in clinical pipelines. Allogeneic therapies offer several benefits including timely availability, scalable production, and cost-effectiveness in comparison to autologous treatments; one drawback, however, is the risk of immune system rejection.
There are many different cell types suitable for use as allogeneic therapies, and given the number of options, manufacturing processes are varied and thus not templated. Additional production challenges include the fact that process are typically performed at a larger scale and require more complex manipulations compared to autologous manufacturing processes.
Ultimately, robust commercial scale bioprocessing workflows must be established along with strategies for sterility assurance.
Bioprocessing Considerations
Establish a Robust Process
Regardless of the culture platform used to produce an allogeneic cell therapy, critical parameters such as cell quantity and quality must be consistently met at each stage of the manufacturing process. If the process is not robust, out-of-specification events may occur leading to early batch termination, product release delays, time- and labor-intensive investigations, and the to repeat production.
One strategy to define and establish a robust process is to leverage quality by design (QbD) principles to establish the manufacturing process.
Ensure Process Compatibility with GMP Suites Conditions
Processes must also be compatible with GMP suite conditions. For example, the use of any water-containing equipment or equipment that increases the humidity in the GMP suite should be avoided. Alternative systems and equipment, such as dry baths and non-humidified incubators, can be used, but the manufacturing process must be validated for these systems.
Create the Sampling Plan
A plan to collect samples to test for endotoxin, cell numbers, cell quality, and functionality is essential. In addition to considering how samples will be collected and where they will be tested, how and when the samples will be shipped must be determined to ensure sample integrity.
Plan for Media Production and Management
Media production planning is essential to ensure a sufficient supply throughout the entire manufacturing workflow. A key consideration is whether to produce it in-house or outsource it from validated and reputable suppliers. This decision is typically dictated by the complexity of the media, process volume requirements, shipping costs, the cadence at which media are needed, storage requirements, and shelf life/stability.
Sterility Assurance Considerations
Use Excipient-Grade GMP Materials
Raw materials should be suitable for GMP manufacturing, and when a tech transfer is made to a contract manufacturer, pharma- or IPEC-grade materials will be required, otherwise it may be necessary to source and validate the proper materials. Consumables such as pipettes and single-use assemblies must meet a stringent sterility assurance level (SAL) of 10-6.
Qualify Reagents for Human Use
Reagents must be qualified for human use, be free of contamination and adventitious agents, and if possible, should be of non-animal origin. If animal components cannot be avoided, a risk assessment of these components must be performed, and control strategies implemented as needed. Reagents with a higher risk of contamination from mycoplasma such as fetal bovine serum, for example, should be triple filtered through a 0.1 µm filter.
Adopt Closed Processing
Closed processing is preferred to minimize the risk of contamination. Sterile connections or welding/sealing can be used to connect or disconnect separate fluid paths between unit operations and maintain the sterility of the process path, even in lower classified environments. When open processing cannot be avoided, manipulations such as the transfer of media or cells should be minimized, and alternative solutions should also be explored. The risk of contamination from open processes should be assessed and the sterility of the process tested by aseptic process simulation (APS).
Perform Aseptic Process Simulation
APS is performed by simulating the process with tryptic soy broth, a media that supports the growth of micro-organisms. The simulation challenges the sterility of the process, operators executing the process steps, and the environment in which the processes are performed. APS is a requirement for GMP manufacturing and should be factored into overall timelines and budgets.
Ensure Proper Sterile Filtration
Filters used for sterile filtration of liquids should undergo pre-use post-sterilization integrity testing (PUPSIT) or the solution should preferably undergo double filtration. In both cases, the pre-sterilizing filtration burden must be less than 10 CFU per 100 mL. After filters are used, they must undergo integrity testing to ensure that their integrity was not affected during the filtration process.
Understand Extractable and Leachables (E&L)
The possible presence of E&L must be evaluated. Ideally, any E&Ls should be inert and not affect the quality of the cells. When using single-use components that consist of additives or antioxidants, a risk-based approach should be considered.
Particulates
The presence of particulates in the process path can be minimized. Options include visual checks of consumables, use of particulate filters prior to the final fill stage, and visual inspection of the product following the fill step. Rinse studies should also be carried out and particle libraries created to curate the particles that are found in the process.
