Natural killer (NK) cells are essential players in the innate immune system, capable of directly killing infected or malignant cells without prior activation, making them strong candidates for adoptive cell therapy in cancer. On this page, we have curated several examples that showcase how leading NK cell experts leverage cell avidity analysis to significantly advance therapy development.

The promise of NK cells in cancer therapy

NK cells offer a relatively safe therapeutic profile as, unlike T cell therapies, they do not induce cytokine release syndrome or graft-versus-host disease. However, while current NK cell therapies have shown overall promise in treating cancer, their efficacy can be limited by challenges such as poor persistence, limited cytotoxicity, and an inability to overcome inhibitory signals from tumor cells. With the help of cell avidity analysis, significant advancements are being made to address these limitations and improve NK cell function.

Therapy advancements included in this application highlight:

·       INKmune has demonstrated the ability to prime NK cells in vivo, generating memory-like NK cells that can effectively target tumors even after cryopreservation, overcoming resistance posed by conventional NK cells.

·       Venetoclax, traditionally used to induce tumor cell apoptosis and approved by the FDA, has emerged as a potential enhancer of NK cell cytotoxicity, broadening its role from a tumor-killing agent to an immune-modulating tool.

·       Advancements in CAR technology are improving NK cell-mediated tumor targeting, particularly in overcoming the disorganized synapse structures that have historically hindered effective signaling. By incorporating PDZ domain-binding moieties and leveraging proteins like CRTAM, researchers are enhancing immune synapse organization, significantly boosting the functional efficacy of NK cells in tumor surveillance.

INmune’s tumor-primed NK cells confer stronger avidity and increased killing

In a 2024 study, work by the Lowdell lab of University College London focused on uncovering the mechanisms that drive enhanced cytotoxicity in memory-like NK (mlNK) cells, generated through both cytokine-induced (iCIML) and tumor-primed (TpNK) methods. The researchers combined high-dimensional flow cytometry, proteomic and metabolomic profiling, with cell avidity measurements to deeply understand mlNK potency.

Flow cytometry and proteomic analysis identified proteins uniquely associated with mlNK cells, many of which are involved in enhancing effector function, increased adhesion and overcoming tumor-induced inhibition.

Metabolomic profiling showed that these cells have increased glycolytic activity and improved mitochondrial fitness, enabling them to sustain their cytotoxic functions for longer, even in the challenging conditions of the tumor microenvironment.

Crucially, cell avidity measurements using LUMICKS’ cell avidity technology demonstrated that binding to NK cell-resistant tumor targets was restored upon mlNK cell differentiation, while resting NK (rNK) cells were unable to bind to the same tumor types (figure). This increased avidity strongly correlated with improved cytotoxicity in vitro, validating that strong binding enhances NK cell function, even to otherwise NK cell-resistant tumor cells.

Promising indications of increased lysis potential of tumor-primed mlNK cells derived from patients treated with the trademarked INKmune protocol, ie., infusion of a replication-incompetent preparation of the INB16 tumor cell line, open the door for tumor-primed mlNK application in therapeutic context.

Curious for more details? Read the full story on the 2024 Lowdell publication in our research brief.

Venetoclax boosts adoptive NK cell therapy against leukemia by increasing cell avidity

Venetoclax, an FDA-approved BCL-2 inhibitor, is prescribed for chronic lymphocytic leukemia (CLL) and acute myeloid leukemia (AML). While known for its role in inducing apoptosis, its broader effects on immune responses are less understood.

A 2024 study by the laboratory of Fang Ni at the University of Science and Technology of China found that venetoclax enhances NK cell cytotoxicity, suggesting it may boost NK cell-mediated antitumor immunity. This research explores the drug’s impact on NK cells and its potential in NK cell-based immunotherapy.

First, the therapeutic potential of venetoclax-treated NK cells for AML was assessed using three human AML mouse models. Mice were injected with either AML cell lines or patient-derived AML cells. In all models, venetoclax-treated NK cells significantly reduced the leukemia burden in the bone marrow compared to untreated NK cells or controls. These findings demonstrate venetoclax’s ability to enhance NK cell cytotoxicity against AML in vivo.

To understand the mechanism underlying the enhanced killing activity of NK cells upon venetoclax treatment, cell avidity analysis with z-Movi was performed. Venetoclax-treated NK cells demonstrated an impressive six-fold increase in binding force for AML cells compared to untreated NK cells, resulting in faster conjugation and immune synapse formation. These enhancements in cellular avidity, because of cytoskeleton remodeling, as demonstrated by additional experiments, contributed to improved NK cell-mediated killing of AML cells.

In summary, this study highlights a promising approach to enhance NK cell-based immunotherapies using venetoclax. By boosting NK cell function, such as mitochondrial metabolism, immunological synapse formation, and cytotoxicity, venetoclax may improve cancer treatment outcomes. Its FDA approval can facilitate and fast track the translation of these findings into clinical practice, paving the way for more effective NK cell-based cancer therapies.

Cell avidity may be the best and earliest predictor for in vivo tumor control for CAR-NK cells

Work using cell avidity measurements by the Gottschalk lab at St. Jude Children’s Research Hospital (published in Nature Biotechnology) sought to tune CAR synapses in NK cells by adding an intracellular scaffolding protein binding site to the CAR called the PDZ binding motif.

PDZ specifically binds Scribble resulting in additional scaffolding and crosslinking to enhance synapse formation resulting in increased avidity and in vivo efficacy.

Hear Dr. Peter Chockley discuss his research insights in full context in the on-demand webinar, accessible when you subscribe to our newsletter.