Background: Colorectal cancer liver metastases (CRCLM) are a major source of morbidity and mortality. Historically, curative therapy has been limited to surgical resection, but only a small fraction of patients are eligible. Cellular immunotherapy has shown promise in hematologic cancers, but challenges to solid tumor therapy remain, including lymphocyte trafficking, elevated interstitial fluid pressures, and immunosuppression. Regional intravascular infusion is a non-surgical, minimally invasive procedure commonly used in liver cancer to deliver therapeutics, which can be augmented by Pressure Enabled Drug Delivery (PEDD). We hypothesized that utilizing established regional delivery strategies to administer natural killer (NK) cells engineered to express a natural killer group 2, member D (NKG2D) activating chimeric receptor and membrane bound IL-15 (CAR NKG2D cells) could increase anti-tumor activity against liver cancer. Methods: In vitro cytotoxicity of CAR NKG2D NK cells was determined in co-culture systems. CRCLM-bearing NSG mice were treated with either CAR NKG2D, non-transduced NK cells (NT-NK), or vehicle via portal vein (PV) for regional PEDD or tail vein (TV) for systemic delivery (SD). Tumor burden was measured via tumor bioluminescence. Mann-Whitney tests were performed for statistical comparisons. Correlation of NKG2D ligand expression in tissue and serum was measured by CODEX and Luminex. Results: Multiple NKG2D ligands are highly expressed in hepatocellular and colorectal carcinoma cell lines (HCC and CRC respectively). As such, these cells lines are highly susceptible to NKG2D-mediated cytotoxicity. CAR NKG2D NK cells were 3- to 4-fold more potent in vitro than NT-NK cells against multiple HCC and CRC cell lines, including those bearing Ras pathway mutations. Using a mouse model of locoregional delivery under high pressure (10 mL/minute), we show that significant tumor reduction (p < 0.05) is only achieved when CAR NKG2D NK cells, but not vehicle or NT-NK cells, were delivered via PV and not via TV. Recovery of CAR NKG2D NK cells in hepatic tissues was on average 2-fold higher after administration via PV than that observed after TV delivery (p = 0.0001). PV delivery of NT-NK cells did not result in appreciable liver engraftment or tumor growth inhibition. Conclusions: CAR NKG2D NK cells demonstrate enhanced in vitro and in vivo cytotoxicity against CRC and HCC cell lines. Significant tumor control using regional delivery in initial studies support continued clinical development. NKX101 is an investigational agent comprised of CAR NKG2D NK cells being evaluated in a phase 1 clinical study for treatment of relapsed/refractory acute myeloid leukemia or higher risk myelodysplastic syndrome. Studies are ongoing to understand NKX101 kinetics, role of delivery pressure, and activity in combination in preclinical models of CRCLM.