New drug cocktail enhances CAR-T cells for cancer treatment

Preclinical research findings from the University of North Carolina Lineberger Comprehensive Cancer Center identified a cocktail of three different drugs that can be used to generate more robust immune system CAR-Ts (chimeric antigen receptor-T cells) to fight cancer. This finding may have a significant impact on improving the production of CAR-T cells for clinical use.

CAR-T cell immunotherapy involves harvesting immune-system T cells from a patient and genetically re-engineering them in the lab to recognize targets on the surface of cancer cells when they are reinfused into patients. Patients treated with certain types of CAR-T cells can have significant responses to their cancer, particularly when the re-engineered cells contain a subset of immune cells identified as T-memory stem cells (T_SCM).

The research findings appeared Jan. 8 in Nature Immunology.

CAR-T cells produced in the lab for reinfusion can be extremely different from one patient to another and the lack of certain types of cells in the end product can significantly reduce the capacity of these cells to persist long term. Our study demonstrates that the addition of the drugs we have identified during the re-engineering process allows the preservation of a critical cell subset responsible for long-term persistence."

Gianpietro Dotti, MD, professor of microbiology and immunology at UNC School of Medicine and co-leader of the UNC Lineberger immunology research program

Dotti and Yang Xu, PhD, are the paper's corresponding authors. Feifei Song, PhD, a UNC Lineberger postdoctoral research fellow, is the first author.

The researchers, using lab and mouse experiments, identified several enzymes called kinases (ITK, ADCK3, MAP3K4 and CDK13) that are involved in the enrichment of TSCM-like CAR-T cells. In particular, ADCK3 and MAP3K4 were found to be potential novel targets in T cells, suggesting that further study into their functions and signaling pathways might reveal insights into how T cells differentiate, or change, to perform important immune functions.

The identification of the kinases then allowed the scientists to conduct a sophisticated screening process to search for kinase-inhibiting drugs that preserve TSCM-like cells in re-engineered CAR-T cells generated from both healthy donors and patients with chronic lymphocytic leukemia (CLL).

Because targeting a single signaling pathway often triggers compensatory defensive mechanisms in cancer cells, the researchers thought that the use of several kinase inhibitors that target multiple, non-overlapping pathways could have the potential to circumvent that compensation and achieve greater enrichment of TSCMs in CAR-T cell products, improving anti-tumor activity.

The investigators were correct.

One of their most striking findings was the inability of a lone kinase inhibitor to increase the frequency of certain TSCM-like CAR-T cells. In sharp contrast, the three-drug kinase inhibitor cocktail consistently increased the frequency of TSCM-like CAR-T cells in both healthy donors and patients with CLL who harbored particularly dysfunctional T cells.

"We tested our hypothesis in CLL because the T cells in these patients are really dysfunctional cells. The strategy we propose is not tailored to blood-borne malignancies but is a general concept applicable to CAR-T cell manufacturing for all diseases," Dotti said. "Our study also helps show the advantages of pharmacological approaches over genetic approaches to enrich TSCM-like cells as most gene-targeted therapies have not proven to be very effective in this arena."

Dotti and his colleagues said additional research is needed to determine how the kinase inhibitors actively drive the differentiation of TSCMs before the experimental drug cocktail can be studied in a clinical trial. But they believe that their kinase inhibitor cocktail could be rapidly integrated into the manufacturing of other T-cell products, such as tumor-infiltrating lymphocytes which are also used to fight cancer.