Looking to the Future of CAR-T Cell Therapy Manufacture

It’s been 20 years since scientists at Memorial Sloan Kettering developed the first effective CAR-T cells [1], and almost 10 years since this same team published results of the first clinical trial treating 5 adults with relapsed B cell acute lymphoblastic leukemia (B-ALL) with CD19-directed CAR-T cells. These patients had a ‘dismal’ prognosis, but following treatment all 5 achieved rapid tumor eradication and complete molecular remission [2]. For the first time, patients diagnosed with ‘hopeless’ cancers had hope.

It’s hardly surprising that this led to a rapid expansion of the field and intense focus on arming and targeting the cells of the immune system against cancer. This focus rightfully shows no signs of waning. In 2021, there were 897 cell-based immune-oncology clinical trials ongoing worldwide, with an increasing number of trials focusing on treatments for solid tumors and allogeneic CAR-T cell therapies [3]. The scientific challenges involved in developing CAR-T cells for solid tumors and ‘off the shelf’ CAR-T cells are numerous and are being ably countered by therapeutics companies and academics alike. But it’s down to us as contract testing development and manufacturing organizations (CTDMOs) to help overcome the manufacturing and testing challenges this evolution of the field brings with it.

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Targeting Solid Tumors with Large Patient Populations

Developing a CAR-T cell that targets solid tumors doesn’t necessarily present a manufacturing challenge itself, but we do need to anticipate that increasing the number of target indications will also
increase the patient population that could potentially benefit from these therapies. Therefore, manufacturing processes will need to scale up to meet this potential significant increase in demand.

One of the earliest scalability challenges for CAR-T cell therapy manufacture comes from the requirement for plasmids to manufacture the large amount of cost-effective lentiviral vectors (LVV) commonly used to introduce the CAR construct into T cells. Plasmid-based manufacturing can be expensive; demand, especially for GMP grade plasmids, has historically outpaced supply; and plasmid-based lentiviral vector manufacture has inherent scalability and process variability limitations.

Overcoming this challenge requires a two-pronged approach. The first is for those therapeutics companies experiencing plasmid supply chain headaches today. Their manufacturing partner should work with them to provide a straightforward way to access high-quality, high-yielding lentiviral plasmids within a rapid timeframe, and ensure that the tech transfer process for lentiviral manufacturing is smooth and hassle free. Using plasmids that have been prevalidated for use on the lentiviral vector manufacturing platform can also help mitigate challenges with process variability, and working with a CDMO that can act as a single supplier of both plasmids and lentiviral vectors can further reduce limitations in this space.

The second, perhaps more appropriate for those therapeutics developers planning ahead to future commercial manufacture, is to devise ways to manufacture lentiviral vectors without needing plasmids at all. At WuXi Advanced Therapies, we have developed inducible lentiviral producer cell lines derived from HEK293 cells, which have all the genetic elements needed to produce a gene-of-interest expressing lentiviral vector stably integrated into the cells’ genome. This system therefore requires nothing more than cell culture and induced LVV production prior to harvesting the lentiviral vectors, so can overcome most of the challenges associated with plasmid based viral vector manufacture in a single step.

Our latest data shows that GFP expressing producer cell lines produce similar yields of lentiviral vectors to the transient system prior to any process development, and high lentiviral yields are maintained in producer cell lines encoding a CD19 construct. We hope that manufacturing systems like this that will improve the scalability and cost effectiveness of CAR-T cell manufacture will be a positive step towards making these life-saving treatments accessible to a wider patient population. 

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Allogeneic vs Autologous T-Cells

To some extent, a shift from autologous to allogeneic T-cell therapies should simplify some of the logistics involved in CAR-T cell manufacture and testing; the timelines will be less critical when there isn’t a patient waiting for their own activated T-cells to be reinfused, and there may well be larger volumes of material available for testing. However, a shift to off-the-shelf CAR-T cell therapies brings its own challenges. For example, unlike autologous cell therapies, allogeneic therapies will need to be produced in larger quantities (i.e., more expansion) with additional genetic modifications, more biosafety testing and will then need to be stored long term. They’ll likely need to be frozen and thawed again and the formulation / fill process will differ significantly from those of autologous CAR-T cell therapies; all processes that can affect the manufacturing timelines and costs, but more importantly the quality, of the fi nal product. This is somewhere that again, contract testing development and manufacturing organizations can work together with therapeutics developers to optimize this process and testing and make sure that the best possible version of the product reaches the patients who need it.

Over the last 20 years, the science behind immune-oncology cell-based therapies, most particularly CAR-T cell therapies, has made enormous leaps forward. Now it’s over to us, the CTDMOs, to make sure that we’re prepared not only to meet, but to welcome, this new era for CAR-T cell therapies targeting early stage disease, solid tumors or off-the-shelf treatments, and that our technologies and processes are set up in such a way that developers can maximize the cost effectiveness and quality of their end-product in order to score the most important goal of all – accessible treatments for patients who have hope, where before there was none.

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This article has been produced in partnership with WuXi Advanced Therapies.