IDO and TGF-β Inhibitors for the Treatment of Lung Cancer

Indoleamine-2,3-dioxygenase (IDO) is an enzyme that catalyzes the conversion of tryptophan to N-formylkynurenine, and it is the rate-limiting step in the kynurenine pathway. The increased IDO activity is well correlated with many diseases and disorders. Hence, inhibition of IDO will suppress the proliferation of cancer cells and exhibit beneficial effects on cancer patients. This book chapter focuses on the structure of IDO’s active site, the pharmacophore of IDO inhibitors, the most widely studied IDO inhibitors, and the discovery of new IDO inhibitors for treating lung cancer. The second part of this chapter discusses the inhibitors of transforming growth factor-β (TGF-β) receptor I. TGF-β is a group of polypeptide molecules acting like hormones or like local mediators. They are present in both vertebrates and invertebrates. Dysregulation of the TGF-β pathway leads to the development of several diseases and disorders. It includes immune dysfunction, fibrosis, cerebrovascular diseases, and cancer. Inhibiting the TGF-β signaling pathway leads to beneficial effects in cancer. This section focuses on different targets of TGF-β signaling pathways, the most widely studied TGF-β receptor I inhibitors from the synthetic and natural origin, the structure of TGF-β receptor I and pharmacophoric elements of TGF-β receptor I inhibitors, and the discovery of new TGF-β receptor I inhibitors for the treatment of lung cancer.