Table 1.

Natural killer T (NKT) cell-based clinical and preclinical studies

Strategy	Regimen			Cancer	Phase	Outcome	References
	Expansion	Target	Co-stim
CAR-iNKT
2nd/3rd generation	IL-2	GD2	CD28; 4-1BB; CD28+4-1BB	Neuroblastoma	Preclinical	Cytotoxic against GD-2 positive tumors; co-stimulatory molecule expression improved survival; increased localization to tumor sites; no induction of GVHD	[83]
2nd generation CD62L+	IL-2	CD19	4-1BB	B-cell lymphoma	Preclinical	Increased in vitro and in vivo persistence; enhanced tumor growth control	[88]
2nd generation	IL-2	CSPG4	CD28	Melanoma	Preclinical	Increased production of pro-inflammatory cytokines	[92]
2nd/3rd generation	IL-2, IL-17, and/or IL-21	CD19	4-1BB	B-cell lymphoma	Preclinical	Preservation of CD26L+ NKT cells during expansion; enhanced cytotoxicity; increased production of Th1 cytokines	[89]
2nd/4th generation	IL-2 and/or IL-15	CD19	CD28; CD28+OX40	B-cell lymphoma	Preclinical	Increased proliferation and persistence of CAR-NKTs in vivo against CD1d-positive-CD19-positive B cell malignancies	[87]
2nd generation	IL-2, IL-7, and/or IL-21	GD2	Coexpression of IL-15 with CD28 or 4-1BB	Neuroblastoma	Preclinical	Co-expression of IL-15 increased survival and cytotoxicity against GD-2 positive tumors, enhanced in vivo expansion, and increased number of CAR-NKTs able to infiltrate and persist in tumor sites	[84]
2nd generation	IL-2, IL-7, and IL-15	CD38/BCMA	CD28; 4-1BB	Multiple myeloma	Preclinical	Maintained expansion and tumor killing ability against cells ranging in levels of CD1d expression	[93]
2nd generation	IL-2	CD19	CD28	B-cell lymphoma	Preclinical	Induction of host CD8 T-cell priming; enhanced tumor control; prolonged survival	[90]
		Isomesothelin			Preclinical	Cytotoxic against solid tumors; potential in vivo persistence through central memory phenotype	[114]
4th generation		GD2	Coexpression of IL-15 with CD28	Neuroblastoma	Phase I recruiting	Effective and safe expansion of CAR-NKTs localized to GD2-positive tumors	NCT03294954; [85]
4th generation		CD19	Coexpression of IL-15 with CD28	B-cell lymphoma	Phase I recruiting		NCT03774654
4th generation		CD19	4-1BB	B-cell lymphoma	Phase I recruiting		NCT04814004
HSC-iNKT
HSC-iNKT	αGC/PBMCs, αGC/APCs and IL-7/IL-15	CD1d		Multiple myeloma and melanoma	Preclinical	Increased survival rate; increased localization to and infiltration of tumor sites; no increase in tissue inflammation; no induction of GVHD	[112]
Combined HSC and CAR-iNKT
HSC-iNKT and 2nd generation  CAR	αGC/PBMCs and IL-7/IL-15	BCMA	4-1BB	Multiple myeloma	Preclinical	High levels of effector cytokines; increased tumor infiltration; no induction of GVHD; low immunogenicity; low risk of NK-cell-mediated allorejection; ability to be manufactured on a clinical scale	[113]
Oncolytic virus
VSV and/or reovirus		4T1 and ID8		Ovarian and breast metastases	Preclinical	Prolonged survival; decreased tumor burden; increase in antigen presentation capacity; induce immunogenic cell death	[107]
Antibody fusion proteins and BiTEs
	αGalCer/sCD1d-anti-HER2 fusion protein			Lung metastases and squamous cell carcinoma	Preclinical	Increased tumor localization; increased accumulation and activation of iNKT, NK and T cells at tumor sites; increased inhibition of lung metastases	[115]
	αGalCer/sCD1d-anti-HER2 fusion protein; αGalCer/sCD1d-anti-CEA fusion protein			Pancreatic cancer, breast cancer, and colon cancer	Preclinical	Increase activation of iNKT cells; directly cytotoxic against either HER2 or CEA positive tumors depending on which fusion protein is administered; increased cytokine production	[101]
	CD3xPDL1 BiTE			PDL1+ tumors (melanoma, SCLC, and NSCLC)	Preclinical	Increased activation of CD4+ and CD8+ T cells and NKT cells cytotoxic against PDL1+ tumors; increased activation of PBMCs against PDL1+ tumor cells; prolonged survival	[105]
Checkpoint inhibitors
	Anti-PD-1 and/or anti-CTLA-4 checkpoint blockade			Colon carcinoma	Preclinical	Decreased TNF-α production; increased IFN-γ driven NKT cell response; decrease in tumor growth through cytokine production	[116]
	Anti-PDL1 checkpoint blockade with αGalCer-pulsed APCs			NSCLC	Preclinical	Increased PD-1 expression on iNKT cells; increased IFN-γ production by iNKT cells; enhanced directed cytotoxicity and recruitment of effector cells	[100]
	Anti-PD-L1 blocking antibody with αGalCer treatment			Melanoma	Preclinical	Inhibited iNKT cell anergy; increased IFN-γ production; increased activation of NK cells	[99]
Combination therapies
	αGalCer-conjugated BiTEs with anti-CTLA-4 inhibitor			Colorectal cancer and melanoma	Preclinical	Enhanced iNKT cell activation; increased cytokine production and effector cell activation; no induction of iNKT cell anergy or exhaustion	[117]

CAR chimeric antigen receptor, iNKT invariant natural killer T cell, TCR T-cell receptor, GVHD graft-versus-host disease, BiTEs bispecific T-cell engagers, SCLC small-cell lung cancer, NSCLC non-SCLC