425 Antibody targeting tumor-derived soluble MIC reprograms NK cell metabolic fitness and enhances NK cell-based therapy for solid tumors

<h3>Background</h3> Lack of persistence and loss of effector function in human solid tumors are the major challenges of NK cell therapy. In our published studies with immune competent animal models, we have shown that human tumor-derived soluble NKG2D ligand sMIC significantly impaired tumoral NK cell persistence and function and that an anti-sMIC antibody B10G5 restored endogenous NK cell homeostatic renewal ability. With the knowledge, we further asked: 1) how does the anti-sMIC antibody restore NK cell homeostatic maintenance in MIC+ tumors? 2) Can a humanized anti-MIC huB10G5 enhance NK cell persistence and function in targeting MIC+ solid tumors? <h3>Methods</h3> We assessed NK cell metabolic abilities with Seahorse, carbo-metabolic flux, and flow cytometry assay ex vivo and in vivo when exposed to sMIC and in the presence and absence of the anti-sMIC antibody B10G5. Various metabolic inhibitors were applied in ex vivo assays to validate critical metabolic pathways. For ATNK assay, NCG mice were inoculated with MIC⁺ human sarcoma tumors, prostate tumors, and pancreatic tumors. When tumors were established to approximately 100 mm³ in size, the clinical format anti-MIC antibody (3 mg/Kg) huB10G5 and K562-expanded human primary NK cells (pNK, 5M/mouse) were administrated once per week. Tumors growth and bodyweight were monitored twice per week. <h3>Results</h3> The anti-sMIC antibody B10G5 forms a complex with sMIC to continuously bind to NKG2D with reduced affinity as compared to sMIC. High affinity sMIC stimulating NKG2D resulted in deranged NK cell metabolic activity that led to the overproduction of ROS and mitochondria DNA damage. The B10G5/sMIC complex stimulation of NKG2D allows the rhythmic NKG2D activation and enables NK cells to flexibly utilize multiple metabolic pathways, such as glycolysis, TCA cycle, and fatty acid pathway to sustain cellular physiology and effector function. Without huB10G5, transferred NK elicited limited anti-tumor activity and persistence in vivo. With the combination of huB10G5, transferred NK cell can effectively eradicate tumors in over 60% of animals. Intratumoral NK analyses revealed better NK cell persistence and effector function. <h3>Conclusions</h3> These results suggest that huB10G/sMIC can regulate NKG2D signaling to enable NK cell metabolic fitness and thus better persistence and function in solid tumors. As huB10G5 will be in clinic soon, this study provided a novel approach to enhance off-the-shelf NK cell therapy in solid tumors with novel mechanisms.