Dual-targeted CAR-NK cells prevent cell dysfunction and tumor escape

Researchers at the University of Texas MD Anderson Cancer Center have developed a new method that uses a second chimeric antigen receptor (CAR) as a logic gate to engineer natural killer cells (NK) that require two signals to eliminate one target cell
.
In preclinical studies, these next-generation CAR-NK cells improved tumor specificity and enhanced anti-tumor activity by overcoming processes that lead to NK cell dysfunction and tumor recurrence
.

The study, published today in the journal Nature Medicine, shows that a normal physiological process called trogocytosis can lead to tumor escape and adverse reactions after CAR-NK cell therapy, which can lead to tumor antigen loss, NK cell failure, and carnage (killing sibling CAR-NK cells
).

"We discovered a new mechanism for recurrence after CAR-NK cell therapy, and we also developed a strategy to mitigate this process," said
Katy Rezvani, MD, corresponding author and professor of stem cell transplantation and cell therapy.
"We designed CAR-NK cells with double-targeted CAR-NK cells, which are able to ignore tumor antigens on the surface of their sibling NK cells and selectively eliminate tumor cells
.
"

Rezwani and Rezwani's lab, M.
D.
Yelly, led the study
.

During cytosolation, the surface proteins of the target cells are transferred to the surface of immune cells (such as NK cells or T cells) to regulate their activity
.
Through preclinical models, Li and colleagues found that CAR activation promotes phagocytic action, leading to the metastasis and expression
of tumor antigens on CAR-NK cells.

This leads to a reduction in target antigens for tumor cells and CAR-NK cells, where engineered cells target each other rather than tumors
.
Self-targeting leads to NK cell failure, metabolic dysfunction and weakened
anti-tumor response.

By studying clinical samples from patients with lymphatic malignancies who used anti-CD19 CAR-NK cell therapy in clinical trials, the researchers confirmed that higher levels of CD19 antigen on CAR-NK cells correlate with lower CD19 levels and a higher probability of recurrence
on tumor cells.

To stop this process from happening, the researchers added an inhibitory CAR designed to recognize markers unique to NK cells, causing CAR-NK cells to receive a "don't kill me" signal when interacting with their sibling cells, even if they have tumor antigens
on their surfaces.
In preclinical models, these logically gated CAR-NK cells are able to better focus and attack tumor cells, reduce the frequency of NK cell failure and cannibalism, and improve anti-tumor activity
.

"It is important to prevent tumors from escaping after CAR-NK treatment, as this can cause relapse
in some patients.
By preventing the failure and cannibalism of CAR-NK cells, we can further increase their activity and function," Rezvani said
.
"We are excited to translate this research into the clinic because it is something that
can be applied to any CAR-NK cell therapy.
"

The study builds on the work that preceded Rezvani's lab to advance and improve CAR-NK cell therapy, including a clinical trial of leukemia and lymphoma patients, as well as a preclinical study
of engineering CAR-NK cells to overcome immunosuppression in glioblastoma.
This study provides a further understanding of CAR-NK biology and suggests that clinical evaluation of the dual CAR strategy is warranted
.