CAR Therapies for Newbies: Traps and Pitfalls

Chimeric Antigen Receptor (CAR) expressing cells are one of the most promising breakthroughs in cancer research in decades. In brief, the technology involves transducing  immune cells with engineered receptors designed to target carcinogenic antigens in order to induce a systemic response in patients to target the cancer. Over the past decade, the technology has gone from a theoretical concept to an accepted treatment in the medical community with regulatory approval in both the US and Europe. However, the therapy represents a new trend of 'personalized medicine,' and therefore requires careful preparation before deploying in either an experimental or clinical setting to achieve the desired outcomes. The goal of this article is to help identify potential challenges or pitfalls for less experienced researchers that might be interested in studying the procedure so they can be addressed prior to any large investments.

It's important to understand the limitations of CAR therapy prior to implementation. The process is not equally effective against all cancers in its current state. At the moment, CAR therapy is most frequently deployed against B cell malignancies due to their expression of CD19, which serves as an identifying marker for the cancer. However, most other types of  cancers do not possess such an easily identifiable marker. Instead, solid tumors frequently undergo proportional changes in markers already present on the healthy cells or undergo changes in multiple markers at once. There have been studies on techniques to address these complications, such as co-stimulatory or multi-target CARs, but none have reached clinical acceptance yet. 

The design of the receptor determines the response

CAR receptors can be divided into 3 potential components, each with their own roles in the process of instigating an immune response. The binding sub-unit of the CAR, responsible for binding to the target antigen, the intermembrane region (sometimes further subdivided into an additional 'hinge' spacer region) of the CAR which plays a role in receptor structure and therefore affinity, and the signaling portion of the molecule, which controls downstream reactions. There are different versions of each subunit that one can use when designing a receptor and a mistake in this area can cause problems ranging from poor immune response to a potentially lethal cytokine storm. It is not recommended to implement a new type of CAR receptor without a thorough understanding of the molecular mechanisms involved in the binding of the CAR to the antigen. These will be unique to the specific cancer being treated, and so careful literature review should be performed to mitigate such concerns before they have a chance to play a role in treatment efficacy.

GMP considerations are extremely important

The final step prior to administering  treatment is to expand the cells. Because the product is intended for clinical use, it is vital that reagents intended for Good Manufacturing Practices (GMP) be used. Lonza's protocol for expanding T-cells currently calls for TheraPEAK® X-VIVO® Cell Medium as an expansion media as it is optimized for use with hematopoietic cells, including those of the immune system. The formulation is Xeno-free, cGMP produced and offered in many formats. 

In addition to this, Lonza has introduced the innovative TheraPEAK® T-VIVO® Cell Culture Medium, which boasts a unique chemically defined formulation aimed at enhancing and streamlining the production of CAR T-cells. This medium has demonstrated excellent performance across various cell culture platforms. All ingredients are non-animal origin (media contains only recombinant proteins), and serum supplementation is not required. 

In conclusion, CAR therapy is an extremely promising technology, but can be difficult to learn and implement due to the personalized nature of the medicine. We hope that this article will provide a starting place for investigators implementing the technology for the first time.

Written by

Angela and Jonathan

Scientific Support Specialists