Table 1.

Summary of preclinical and clinical inhibitors that target MDSC development, suppressive activity, and differentiation

Inhibitors	Class of inhibitors	Mechanism of action
Sunitinib	Tyrosine kinase inhibitors	Inhibition of c‐kit and VEGFR functions
Zoledronic acid	Bisphosphonates	Posttranslational modification of MMPs; c‐Kit cleavage
Gemcitabine	Nucleoside analogs	Induction of MDSC apoptosis and necrosis
5‐FU	Pyrimidine analogs	Induction of MDSC cytotoxicity
Peptibodies	Genetically fused peptide sequences	Targeting the S100 proteins on the MDSCs
CpG ODN	Synthetic DNA molecules	Inhibition of MDSC ARG1 and iNOS production
Nitroaspirin	Nonsteroidal anti‐inflammatory drugs	Inhibition of MDSC ARG1 and iNOS production
N‐acetyl cysteine	Cysteine derivatives	Inhibition of MDSC ARG1 and iNOS production
Bardoxolone methyl	Synthetic triterpenoids	Inhibition of MDSC ROS production via Stat3 inhibition and up‐regulation of antioxidant genes
Celecoxib	NSAID (COX2/PGE2 inhibitor)	Regulation of ARG1 expression in MDSCs
Sildenafil and tadalafil	Phosphodiesterase 5 inhibitors	Regulation of ARG1/iNOS expression in MDSCs
4‐IPP	MIF tautomerase inhibitors	Inhibition of MDSC suppressive function and MDSC to DC differentiation
ATRA	Ligands of the retinoic acid receptors	MDSC to DC differentiation and Inhibition of MDSC‐mediated ROS ERK activation
1α,25‐dihydroxyvitamin D3	Vitamin D	Modulation of tumor‐derived growth factors?
PFK‐158	PFKFB3 inhibitors	Inhibition of MDSC suppressive function