Indoleamine 2,3-dioxygenase 1 (IDO1) is regarded as a promising target for cancer immunotherapy. Many naphthoquinone derivatives have been reported as IDO1 inhibitors so far. Herein, two series of naphthoquinone derivatives, naphthoindolizine and indolizinoquinoline-5,12-dione derivatives, were synthesized and evaluated for their IDO1 inhibitory activity. Most of the target compounds showed significant inhibition potency and high selectivity for IDO1 over tryptophan 2,3-dioxygenase (TDO). The structure-activity relationship was also summarized. The most potent compounds 5c (IC50 23 nM, IDO1 enzyme), and 5b' (IC50 372 nM, HeLa cell) were identified as promising lead compounds.
Keywords: Cancer immunotherapy; Indoleamine 2,3-dioxygenase 1; Indolizinoquinoline-5,12-dione derivatives; Naphthoindolizine.
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