Table 2. A summary of NK-cell-based clinical trials.

No.	Study title	Trial no.	Interventions	Location	Status
1	A phase I/II study of universal off-the-shelf NKG2S-ACE2 CAR NK cells for therapy of COVID-19	NCT04324996	NK cells, IL15-NK cells, NKG2D CAR-NK cells, ACE2 CAR-NK cells, NKG2D-ACE2 CAR-NK cells	China	Recruiting
2	Monocyte and NK cells activity in COVID-19 patients	NCT04375176	Diagnostic test: study of immune-mediated mechanisms in patients tested positive for SARS-CoV-2 Phenotypic and functional analysis of monocytes and NK cells	Italy	Recruiting
3	Off-the-shelf NK cells (KDS-1000) as immunotherapy for COVID-19	NCT04797975	KDS-1000	Not yet been determined	Not yet recruiting
4	Phase I clinical trial on NK cells for COVID-19	NCT04634370	NK Cells infusion	Brazil	Not yet recruiting
5	NK cells treatment for COVID-19	NCT04280224	NK Cells	China	Recruiting
6	Immune cell subgroups in COVID-19 patients	NCT04531319	Flow cytometric analysis	Turkey	Completed
7	NK cell (CYNK-001) infusion in adults with COVID-19	NCT04365101	CYNK-001	USA	Recruiting
8	Phase I/II clinical study of immunotherapy based on adoptive cell transfer as a therapeutic alternative for patients with COVID-19 in Colombia	NCT04344548	Allogenic NK cell transfer	Colombia	Not yet recruiting

NK: Natural killer cell.