Fig. 1

Overview of the NK cell therapy field. A Total number of NK cell-based clinical trials per year of initiation. Since 1997, a total of N = 420 clinical trials with NK cells have been initiated, the majority of which between 2016 and 2021. Most are Phase I and Phase I/II studies, N = 165 and N = 144, respectively. N = 92 studies are Phase II. As the field has just recently emerged, Phase II/III, III and IV trials are few (N = 2, N = 3, N = 3, respectively). For N = 11 trials, the clinical phase is unknown. B Geographical location of companies and institutions developing NK cell therapies. Color scales are representative of the number per country. Data sources: ClinicalTrials.gov, search terms: “NK cell,” “NK cell therapy,” “Natural killer cells” (text); GlobalData.com, drug descriptor: “Natural Killer (NK) Cell Immunotherapy” (drop-down menu), or filter: “Natural Killer cells” (text). The search is limited to December 2021. Clinical studies not based on administration of NK cells to patients or evaluating the infusion of mixed immune cell populations were excluded