Using molecular scissors to improve CAR-T cell therapy

“This is a very exciting discovery that offers new hope of overcoming challenges of CAR-T cell therapy that many cancer patients experience,” says Dr. Kenderian, senior author. “We describe for the first time a mechanism causing the resistance and failure of CAR-T cells, which lies within a protein routinely made by the engineered cells. This research puts us on a new path for improving the longevity of CAR-T cell therapy.”

CAR-T cell therapy is a regenerative immunotherapy in which a person’s T cells are collected from the body and genetically modified in the lab to target proteins on tumors. The engineered T cells are returned to the patient, where they act as a living drug that continually harnesses the power of the immune system to recognize and destroy tumors.

CAR-T cells lose their potency

CAR-T cell therapy is an emerging treatment for blood cancers, putting some B-cell lymphomas and leukemias into complete remission. However, this potential game-changing treatment works very well in only about one-third of cancer patients.

One of the main drivers of failure is T-cell exhaustion. That condition occurs when CAR-T cells weaken, losing their ability to multiply, target and eliminate cancer cells. T-cell exhaustion causes relapse in many patients within a year of receiving CAR-T cell therapy.

In search of new solutions, Dr. Kenderian’s team analyzed pre-infusion CAR-T cells from patients treated with CAR-T cell therapy. They compared data from patients who went into remission to those whose CAR-T cell therapy failed. They also studied how CAR-T cells killed lymphoma, leukemia and multiple myeloma tumors grown in laboratory mice. They compared the results of mice who responded well to CAR-T therapy to those that did not.

The team documented an elevated amount of the protein interleukin-4 (IL-4) in both the human and mice samples of CAR-T cell exhaustion. IL-4 is a protein that regulates inflammation and immunity. In moderation, the IL-4 protein acts as a catalyst that activates the body’s immune system against cancer. This study found the supercharged CAR-T cells sometimes make too much IL-4.

“We discovered CAR-T cells make proteins that are not always helpful to patients. Too much of an IL-4 protein overloads cells and can cause cell exhaustion,” says Carli Stewart, a Ph.D. student within Mayo Clinic Graduate School of Biomedical Sciences and first author.

“This finding prompted us to explore strategies to modify or eliminate the IL-4 protein and study whether that would recharge CAR-T cells and restore their ability to stop cancer.”

Gene editing unveils new understanding

The team used clustered regularly interspaced short palindromic repeats (CRISPR) gene-editing technology to explore genetic function and interaction in CAR-T cell therapy. CRISPR was a key tool in singling out the overabundance of the IL-4 protein in dysfunctional CAR-T cells.

CRISPR acts as “molecular scissors” to precisely cut and alter a person’s genes. In this case, researchers used the high-tech tool to knock out or modify the IL-4 protein causing CAR-T cell dysfunction.

“After applying the CRISPR gene-editing technology to remove the IL-4 protein from the cell, our team documented a significant improvement in the ability of CAR-T cell therapy to recognize and kill cancer,” says Dr. Kenderian.

Researchers also tested monoclonal antibodies to block or neutralize the IL-4 protein. They found that it also rejuvenated CAR-T cells and their ability to block cancer.

Additional research is needed to verify the scientific findings of this study. The data in this paper could lay the foundation for the first-in-human clinical trials for Mayo Clinic patients with CAR-T cell exhaustion.