Novel indoleamine 2, 3-dioxygenase inhibitor and application thereof in preparation of antitumor drugs

The invention belongs to the technical field of biological medicines, and discloses an innovative inhibitor of indoleamine 2, 3-dioxygenase IDO1, namely a nicotinic acid derivative (a derivative of 3-pyridine propionic acid). The 3-pyridine propionic acid derivative can effectively inhibit indoleamine 2, 3-dioxygenase IDO1 to catalyze tryptophan metabolism, can significantly inhibit high-expression IDO1 enzyme activity in human cancer cells, and is low in cytotoxicity. When the nicotinic acid derivatives are used as inhibitors of IDO1 enzyme independently, the growth of transplanted tumors of mice can be remarkably inhibited, and the nicotinic acid derivatives are combined with innate immune pathway STING agonists and/or immune checkpoint inhibitors for use, so that the drug effect of inhibiting tumor growth is better, and the safety is also very good. Therefore, the nicotinic acid derivative has a wide application prospect in preparation of immune antitumor drugs. 本发明属于生物医药技术领域，发明了一类创新的吲哚胺2，3-双加氧酶IDO1的抑制剂，即烟