In the first-ever (sanctioned) investigational use of multiple edits to the human genome, a study found that cells edited in three specific ways and then removed from patients and brought back into the lab setting were able to kill cancer months after their original manufacturing and infusion.
This is the first U.S. clinical trial to test the gene editing approach in humans, and the publication of this new data today follows on the initial report last year that researchers were able to use CRISPR/Cas9 technology to successfully edit three cancer patients' immune cells. The ongoing study is a cooperative between Tmunity Therapeutics, the Parker Institute for Cancer Immunotherapy, and the University of Pennsylvania.
Patients on this trial were treated by Edward A. Stadtmauer, MD, section chief of Hematologic Malignancies at Penn, co-lead author on the study. The approach in this study is closely related to CAR T cell therapy, in which patient immune cells are engineered to fight cancer, but it has some key differences. Just like CAR T, researchers in this study began by collecting a patient's T cells from blood. However, instead of arming these cells with a receptor against a protein such as CD19, the team first used CRISPR/Cas9 editing to remove three genes. The first two edits removed a T cell's natural receptors so they can be reprogrammed to express a synthetic T cell receptor, allowing these cells to seek out and destroy tumors. The third edit removed PD-1, a natural checkpoint that sometimes blocks T cells from doing their job.
Once the three genes are knocked out, a fourth genetic modification was accomplished using a lentivirus to insert the cancer-specific synthetic T cell receptor, which tells the edited T cells to target an antigen called NY-ESO-1. Previously published data show these cells typically survive for less than a week, but this new analysis shows the edited cells used in this study persisted, with the longest follow up at nine months.
Several months after the infusion, researchers drew more blood and isolated the CRISPR-edited cells for study. When brought back into the lab setting, the cells were still able to kill tumors.
The CRISPR-edited T cells used in this study are not active on their own like CAR T cells. Instead, they require the cooperation of a molecule known as HLA-A*02:01, which is only expressed in a subset of patients. This means that patients had to be screened ahead of time to make sure they were a match for the approach. Participants who met the requirements received other clinically-indicated therapy as needed while they waited for their cells to be manufactured. Once that process was completed, all three patients received the gene-edited cells in a single infusion after a short course of chemotherapy. Analysis of blood samples revealed that all three participants had the CRISPR-edited T cells take root and thrive in the patients. While none responded to the therapy, there were no treatment-related serious adverse events.
CRISPR technology has not previously been tested in humans in the U.S. so the research team had to move through a comprehensive and rigorous series of institutional and federal regulatory approval steps, including approval by the National Institutes of Health's Recombinant DNA Research Advisory Committee and review by the U.S. Food and Drug Administration, as well as Penn's institutional review board and institutional biosafety committee. The entire process required more than two years.
Researchers say these new data will open the door to later stage studies to investigate and extend this approach to a broader field beyond cancer, several of which are already planned at Penn.
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