Abstract We recently developed a novel chimeric antigen receptor (CAR) T-cell therapy, called CYAD-01 (a.k.a. NKR-2), incorporating the full-length human natural killer receptor NKG2D fused with the human CD3 zeta signaling domain, which associates with the adaptor molecule DAP10 to provide co-stimulatory signal upon ligand binding. CYAD-01 is currently evaluated in multiple intravenous administrations in the ongoing THINK study (NCT03018405) in both hematological and solid indications. Classical CAR-Ts has yet to demonstrate positive results in the context of solid tumors. Underlying reasons for this reduced clinical activity include the need to extravasate from the peripheral circulation, infiltrate into the tumor and overcome the hostile immune suppressive tumor microenvironment (TME) to deliver anti-tumor effector responses. To address the challenge related to the difficulty of CAR-T cells to access the site of metastasis, the LINK trial (Locoregional Immunotherapy with NKR-2) has been developed to assess the safety and clinical activity of multiple hepatic transarterial administrations of CYAD-01 treatment (every 2 weeks x 3 infusions) in colorectal cancer patients with unresectable liver metastases (NCT03370198). The hepatic transarterial administration (HTAA) cell therapy may offer the advantage of lower systemic toxicity and higher and more persistent concentration of the infused cells on the TME compared with systemic administration. The difference in blood supply between uninvolved liver parenchyma and metastases may favor CYAD-01 tumor homing. Moreover, based on the potential impact of the CYAD-01 treatment on the host immune system, combined with the tumor antigens spreading induced by its direct anti-cancer cells activity, the CYAD-01 HTAA may boost the adaptive immune response and therefore may control any distant lesion (aboscopal effect). This dose escalation study will use a 3+3 design including 3 dose levels of CYAD-01 (3x108, 1x109 and 3x109 cells per injection) to evaluate the maximum tolerated dose of the CYAD-01 hepatic transarterial administration. Peripheral blood samples, as well as tumor biopsies will be collected to determine systemic CYAD-01 kinetics and within the liver tumor tissues, NKG2D ligand expression and systemic cytokine levels in peripheral blood post-infusion. This study will enroll 12 patients in case of no DLT and is open for recruitment. Citation Format: Nathalie Braun, Alain Hendlisz, Leila Shaza, Michaël Vouche, Vincent Donckier, Philippe Aftimos, Ahmad Awada, Caroline Lonez, Bikash Verma, David E. Gilham, Frédéric F. Lehmann. A phase I study assessing the safety and clinical activity of multiple hepatic transarterial administrations of a NKG2D-based CAR-T therapy CYAD-01, in patients with unresectable liver metastases from colorectal cancer abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr CT134.