Treatment with anti-killer-cell immunoglobulin-like receptor (KIR) monoclonal antibody (mAb) is a new approach aimed at harnessing the antileukaemic potential of natural killer (NK) cells for the treatment of acute myeloid leukaemia (AML). NK cell antitumour activity is regulated by a balance between activating and inhibitory receptors (KIR). 1-7F9/IPH2101 is a fully human immunoglobulin G4 (IgG4) mAb that binds to inhibitory KIR and blocks binding with its ligand (human leukocyte antigen C [HLA-C] molecule) on leukaemic cells.In vitro,and in a surrogatein vivomodel in mice, treatment with 1-7F9/IPH2101 was able to induce NK cell activation and cytotoxicity against leukaemic cells. Patients with AML often display abnormal NK cell function, while evidence of an impact of NK cell status on AML outcome has been reported in allogeneic transplantation. 1-7F9/IPH2101 is currently under clinical investigation in patients with AML. This article reviews the mechanisms of NK cell antileukaemic activity and its role and defects in AML. Currently available data on the pre-clinical and clinical development of 1-7F9/IPH2101 are presented, and the rationale for its future use as a single agent or in combination is discussed.