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Early Trials Show Responses for Some Blood Cancers

Natural killer cell

Natural killer cell (NIAID, Flickr.

25 Apr. 2022. First results from two clinical trials testing the safety of natural killer cell therapies show responses by patients with some forms of blood-related cancers. The studies, were released today by biotechnology company Nkarta Inc. in South San Francisco, developer of the experimental treatments, and are not yet peer-reviewed.

Nkarta develops genetically-altered natural killer cells as off-the-shelf cancer therapies. Like B- and T-cells also from the immune system, natural killer cells are white blood cells that respond to tumor cells and viral infections. They’re called “natural killers” for their ability to attack tumors on their own, without priming or prior activation. The company says it engineers natural killer cells by adding receptors to identify and bind to specific molecular targets, then release cancer-killing cytokine enzymes. Nkarta says it also adds interleukin-15, a cytokine that forms on natural killer cell membranes to induce more persistence and activity.

Nkarta says it takes natural killer cells from healthy donors, then expands and genetically modifies the donated cells to express chimeric antigen receptors or CARs and interleukin-15 on the cell membranes. The cells are then altered further with interleukin-15 and frozen to preserve for future administration to patients.

The two early-stage clinical trials are evaluating the safety and safe dosage levels of Nkarta’s two lead products, code-named NKX101 and NKX019. Neither trial has a control or comparison group. The NKX101 trial is recruiting 90 participants at seven sites in the U.S. with relapsed or non-responsive acute myeloid leukemia and myelodysplastic syndromes, both cancers that form in bone marrow. Participants receive two or three weekly doses of NKX101. The study team is looking for adverse effects or toxic responses in patients, such as cytokine release syndrome or immune-system rejection after 30 days, as well as changes in the state of their disease.

Nkarta says results from the first 21 patients in the trial show NKX101 is well tolerated by patients, with no toxic responses found. From two to 10 participants experience some form of low red, white, or platelet blood cell counts, and 4 or fewer report infections that require medical attention.

Greater response at higher doses

Of the 11 participants treated for acute myeloid leukemia and receiving three weekly doses of NKX101, seven participants report at least a partial clinical response to the treatments, and three participants experience a complete response. Of six acute myeloid leukemia patients receiving two NKX101 doses, however, only one shows a partial response. And four participants in the trial treated for myelodysplastic syndromes report no response to the treatments.

The NKX019 trial is enrolling 60 participants at three sites in the U.S. and four locations in Australia, with B-cell malignancies. The Nkarta team reported on the first 10 patients with non-Hodgkin lymphoma and three patients with B-cell acute lymphocytic leukemia. As in the NKX101 trial, participants overall tolerated the treatments and suffered no toxic responses. And like the NKX101 trial, adverse effects requiring medical attention were forms of low red, white, or platelet blood cell counts experienced by two to nine participants.

The study is assessing two different levels of NKX019 in the three doses given to participants. Of the six non-Hodgkin lymphoma patients receiving the higher dose, five patients experience at least a partial response to the treatment, while three of the six patients report a complete response. At the lower dose, two of the four participants report at least a partial response, and one patient experiences a complete response. None of the three patients with B-cell acute lymphocytic leukemia report any response at either dose level.

Nkarta says in a statement that it plans to continue enrolling patients to receive three doses in both trials. The company also says it plans to present more complete findings at a future medical meeting.

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