Table 2.

Strategies for myeloid-derived suppressor cell (MDSC) targeting.

Strategy	Mechanism of Action	Examples	Clinical Trial
Blocking MDSC development	N-Bisphosphonates	Zoledronic acid	Phase 3-completed
	Multi-kinase inhibitors	Sunitinib Sorafenib	Phase 2-completed Phase 3-completed
	JAK2/STAT3 inhibitors	Cucurbitacin B JSI-124	N/A N/A
	Blocking antibodies	Anti-VEGF antibodies	NCT03503604
Differentiation of MDSC into mature cells	Vitamins	ATRA Vitamin A Vitamin D3 Vitamin E	NCT024403778 N/A N/A N/A
	Cytokines	IL-12	N/A
	Others	CpG	N/A
MDSC deactivation	PDE5 inhibitors	Sildenafil Tadalafil	NCT02544880 NCT01697800
	NO inhibitors	NO-aspirins (NCX-4016) L-NAME	Phase1-completed
	ROS inhibitors	Synthetic triterpenoids (omaveloxolone)	Phase 2-completed
	Arginase inhibitors	COX2 inhibitors NOHA L-NAME	N/A N/A N/A
	Recruitment and migration inhibitor	Anti-glycan antibodies CSF-1R inhibitors	NCT03557970
	Others	Histamine inhibitor (ranitidine) Anti-IL-17 antibodies	NCT03145012
MDSC depletion	Cytotoxic agents	Gemcitabine Cisplatin 5-Fluorouracil Paclitaxel	NCT01803152 NCT02432378 N/A N/A
	HSP90 inhibitors	17-DMAG	Phase 1-completed
	Peptide-FC fusion proteins	N/A	N/A

N/A refers to no available information. ATRA: All-trans retinoic acid; PDE5: phosphodiesterase type 5; NCX: Nitric Oxide-Aspirin; L-NAME: L-N^G-Nitroarginine methyl ester; NOHA: N(omega)-hydroxy-l-arginine; HSP90: heat shock protein 90; 17-DMAG: 17-Dimethylaminoethylamino-17-demethoxygeldanamycin.