By Elizabeth Csaszar, Rohin Iyer, and Spencer Hoover
For many cell and gene therapy (CGT) companies, translating a potentially curative therapy from a new biological concept into a scalable and manufacturable product is the largest challenge to commercial success. Navigating this path is particularly difficult for the CGT field for multiple reasons: limited highly qualified personnel who have both the biological and process engineering know-how; an evolving regulatory strategy; and, investors with very aggressive timelines. Even for experienced teams, there is a difficult balance between achieving the major inflection point of the first clinical trial using a manual, open process, and building a more commercially suitable process along with the associated team and facility. Many companies are choosing to work with Contract Development and Manufacturing Organizations (CDMOs) to accelerate their clinical and commercial programs. In this article, we highlight key areas where CDMOs can help companies getting started in the world of CGT manufacturing, with considerations around timing of engagement to maximize commercial and clinical success.
Cell source decisions and access
All CGT products start with a cell. A major initial decision is the choice of primary cells vs. modified or immortalized cell lines as the cell source. This is a decision guided by biology, as the former is often chosen in cases where dosing / patient numbers are low and personalized therapy is required to circumvent complications, such as immune responses, whereas the latter is often chosen in cases where large patient populations are targeted, or where the cells are being used as a producer line for secreted products (exosomes, viral vectors). Each cell source has a different set of technical, regulatory, access, and licensing considerations. A CDMO can help an early stage CGT developer to understand the limitations of their source cells and develop strategies around processing tissue, generating cell banks, or performing cell line engineering.
Early engagement with an experienced CDMO can also help in navigating the evolving and often nebulous regulatory landscape around CGT cell sources. Commercially available cell sources and vectors, though often available for unrestricted use in academic and research settings, may carry licensing fees for clinical and commercial use, and primary cell and tissue sources can often be very challenging to source for preclinical development. CDMOs can leverage existing relationships with public and private entities to help in sourcing these materials. Regardless of the source, thorough characterization of the identity and quality of the starting cell material is critical in pre-clinical development. CDMOs are able to tailor process and assay development programs around the unique needs of biological input material.
In the research stage of a new CGT, cell manipulations are typically highly manual, technically complicated, and demonstrated only at laboratory scale for proof of concept (PoC) and pre-clinical needs. Turning this process into one that will be sufficiently robust, scalable and cost-efficient requires substantial process development work. A CGT developer’s projection of cell quantity needs at clinical trial scale and commercial scale is the starting point for many important process decisions as this will dictate the required scale per batch and number of batches per year. In turn, these parameters guide decisions regarding choice of hardware and the degree of desired process closure, integration and automation that may be appropriate. CDMOs are well positioned to provide guidance on these aspects to early-stage CGT developers. They also have access to, and experience with, varied hardware solutions to enable the evaluation of different platforms and assessment of different technologies without the capital cost and training burden of performing these studies in-house.
As process changes between clinical trial phases are costly to develop and can delay clinical programs, CGT developers need to identify their biggest pain-points to decide where process development will provide the most value. Considerations include understanding where the greatest sources of risk or variability are in the current process and identifying process steps that are incompatible with target scales. An example of the latter would be a company working with an adherent cell type at laboratory scale. To achieve commercial scale production, adaptation of the cell culture to a suspension-based solution, such as a stirred tank reactor with cell aggregates or microcarriers, may be the best technical solution. CDMOs are well suited to work with CGT developers to identify the biggest value-add process changes and recommend a step-wise program for development, optimization and comparability studies. For CGT developers, outsourcing the engineering aspects of process optimization, while building up internal expertise in this field, can save time and allow for process changes to be aligned with aggressive clinical programs.
Analytical methods and assay development
Analytical methods are needed for raw material characterization, in-process testing and quality control (QC) release of final products. When starting out, it can be difficult to know what the critical quality attributes (CQAs) of the drug product will be, so CGT developers often aim to capture as much data as possible about their product during process development. Identifying the correct method to use for a measurement is challenging, and one option for the field is to adopt some of the best practices from design controls used in the development of medical devices and in vitro diagnostics. These include defining design inputs of a method by building a user requirements specification for each analytic so that the assay chosen is truly fit for purpose. Examples of specifications to consider include sensitivity, specificity, turn-around time, cost per test, and the robustness/ruggedness of the assay. Working with CDMOs who have expertise in assay development and qualification can ensure that the appropriate specifications are incorporated. Leaning on established methods at CDMOs, or transferring existing methods for further development and qualification, can also be a strategy to initiate a small project with the CDMO to determine whether they are the right partner.
Ideally, a company would use the same qualified analytical methods from early process development to commercial manufacture. This ensures consistency and comparability of data throughout the life cycle of the CGT product. Furthermore, it is important that robust assays for CQAs are in place before initiating major process changes, as use of these assays will serve to ensure that manufacturing changes are not adversely impacting the final product. Changes in methods between different phases of clinical trials – whether it is because a method is too challenging to run in a QC lab, a critical reagent is no longer available, or the method is no longer relevant based on clinical data – require lengthy and costly equivalency studies to be carried out. Having an established relationship with a CDMO, in which key assays can be run consistently and comparably to other sites, also allows for efficient comparability studies and facilitates smoother tech transfer.
There has been a concerted push toward the use of xeno-free (XF) and animal component-free (ACF) reagents, and pre-sterilized single-use disposables with closed access ports in CGT products, due to the risks of transmissible diseases and contamination during manufacture. Moreover, these choices can also impact cell quality, as evidenced by a recent example suggesting that serum-free media may improve potency and transduction of CAR-T cells both in vitro and in vivo compared to serum-containing media . To this end, many ancillary material manufacturers are now offering reagents and consumables to support CGT developers, though some are still designed to be research use only (RUO). GMP-compliant reagent and consumable sources need to be identified early on and costed out by CGT developers, considering they may be up to ten times more expensive than their RUO counterparts, and often suffer from longer manufacturing and lead times. Leveraging CDMOs at an early stage during development is helpful to establish primary and secondary suppliers of reagents and consumables to meet future demands and identify options that will be suitable to regulators and clinicians.
Challenges remain with manufacturing suitable reagents and consumables. As examples, smaller volume reagents are typically not provided in closed formats and consumables are often hand-assembled, which can lead to manufacturing failures. Though most culture media still come in bottles, bags with weldable lines are now becoming more common. Despite the wider availability of ACF reagents, off-the-shelf reagents may not always support specific cell populations of interest in a cost-efficient manner, which may motivate exploring custom media formulation services. While several vendors offer custom media development, these often rely on conventional formulation techniques, which typically lead, at best, to incremental improvements on current formulations. Novel methods of media formulation involve the use of metabolomics- and proteomics-based discovery, combined with design-of-experiments-(DoE) approaches and the use of liquid handling robotics to enable thousands of formulations to be tested in parallel. Such approaches are now being offered by some CDMOs in the CGT space, which is driving a more complete understanding of the underlying biology of CGTs, while simultaneously reducing cost of goods.
Clinical and logistical considerations
For CGTs, the activities at a manufacturing facility form the central component of the “vein-to-vein” process. Manufacturing decisions must be aligned with clinical and logistical constraints. On the front end, acquisition of input cell material is often dependent on processes outside of the manufacturer’s direct control. These may include obtaining autologous cell material like apheresis units from collection sites, where scheduling and sophistication can vary greatly from site to site. Similarly, handling the manufactured CGTs at clinical sites is also challenging to standardize and is subject to variability of both process and analytics. CDMOs are experienced at interfacing with these sites and identifying solutions to minimize risks. Typically, manufacturers aim to formulate CGTs so that point-of-care manipulations are minimized. This might include selecting a cryoprotectant that is safe for direct infusion to avoid the need for wash or dilution steps, and developing processes that use automated cell thawing systems as a hardware solution to standardize point-of-care handling.
The logistical considerations of access and shipping weigh in to business decisions around using a centralized, regional, or local manufacturing model. This, in turn, will influence which CDMO(s) a therapeutic developer should work with. The proximity of manufacturing facilities to clinical sites will constrain the required shelf life of the CGT. For logistical reasons, frozen products (and frozen input cell materials) are substantially easier to manage and schedule. However, shipping cryopreserved products introduces the need for rigorous cold chain management. Patient-specific CGTs add additional complexity around management of chain of custody throughout the end-to-end manufacturing process and motivate the use of digital tools to support these needs. As the CGT field matures, CDMOs are serving not only as development experts but as supply chain, digital management and logistical partners. Initiating plans early in the development process to manage these aspects will set up CGT developers for success through their clinical and commercial programs.
It is important for CGT developers to think about their manufacturing needs from the outset in their pre-clinical development activities. CGT developers must drive the underlying biological understanding of their product, define their target product profile, and plan their clinical program. These activities can be supported by working in partnership with a CDMO that brings complementary knowledge and skills around process development and manufacturing. In a quickly maturing field, CDMOs are rapidly evolving to serve as full service partners for CGT developers by combining historical expertise from adjacent industries with new tools and capabilities specific to the unique complexities of CGTs. By developing a strong partnership with the right CDMO at the pre-clinical stage, CGT developers can chart out a manufacturing development program that is aligned with their clinical plans and financing expectations. This ensures that their process and analytic methods are meeting all stakeholder needs, from pre-clinical development all the way through to commercialization.
1Medvec AR, Ecker C, Kong H, Wintera EA, Glover J, Varela-Rohena A, Riley JL. Improved Expansion and In Vivo Function of Patient T Cells by a Serum-free Medium. Mol Ther Methods Clin Dev. 2018 Mar 16; 8: 65–74.