State Key Laboratory of Pharmaceutical Biotechnology, Engineering Research Center of Protein and Peptide Medicine, School of Life Sciences, Nanjing University, Nanjing, People's Republic of China; and.
State Key Laboratory of Natural Medicines, Jiangsu Key Laboratory of Drug Discovery for Metabolic Diseases, Center of Drug Discovery, China Pharmaceutical University, Nanjing, People's Republic of China.
J Immunol. 2022 Jul 1;209(1):180-191. doi: 10.4049/jimmunol.2100938. Epub 2022 Jun 20.
The pharmacological inhibition of IDO1 is considered an effective therapeutic approach for cancer treatment. However, the inadequate response of existing holo-IDO1 inhibitors and unclear biomarkers available in clinical practice limit the possibility of developing efficacious IDO1 inhibitors. In the current study, we aimed to elucidate the activity and mechanism of a potent 1-pyrrole-2-carboxylic acid derivative (B37) targeting apo-IDO1 and to determine its role in tumor therapy. By competing with heme for binding to apo-IDO1, B37 potently inhibited IDO1 activity, with an IC of 22 pM assessed using a HeLa cell-based assay. The x-ray cocrystal structure of the inhibitor-enzyme complex showed that the B37-human IDO1 complex has strong hydrophobic interactions, which enhances its binding affinity, determined using isothermal titration calorimetry. Stronger noncovalent interactions, including π stacking and hydrogen bonds formed between B37 and apo-human IDO1, underlay the enthalpy-driven force for B37 for binding to the enzyme. These binding properties endowed B37 with potent antitumor efficacy, which was confirmed in a mouse colon cancer CT26 syngeneic model in BALB/c mice and in an azoxymethane/dextran sulfate sodium-induced colon carcinogenesis model in C57BL/6 mice by activating the host immune system. Moreover, the combination of B37 and anti-PD1 Ab synergistically inhibited tumor growth. These results suggested that B37 may serve as a unique candidate for apo-IDO1 inhibition-mediated tumor immunotherapy.
IDO1 的药理学抑制被认为是癌症治疗的一种有效治疗方法。然而，现有的全酶 IDO1 抑制剂反应不足和临床实践中可用的明确生物标志物有限，限制了开发有效 IDO1 抑制剂的可能性。在本研究中，我们旨在阐明针对apo-IDO1 的一种有效的 1-吡咯-2-羧酸衍生物（B37）的活性和机制，并确定其在肿瘤治疗中的作用。通过与血红素竞争与 apo-IDO1 结合，B37 强烈抑制 IDO1 活性，在基于 HeLa 细胞的测定中，IC 为 22 pM。抑制剂-酶复合物的 X 射线共晶结构表明，B37-人 IDO1 复合物具有强烈的疏水相互作用，这增强了其结合亲和力，通过等温滴定量热法确定。B37 和 apo-人 IDO1 之间形成的更强的非共价相互作用，包括π堆积和氢键，为 B37 与酶结合提供了焓驱动的力。这些结合特性使 B37 具有强大的抗肿瘤功效，这在 BALB/c 小鼠的小鼠结肠癌细胞 CT26 同基因模型和 C57BL/6 小鼠的氧化偶氮甲烷/葡聚糖硫酸钠诱导的结肠癌发生模型中得到证实，通过激活宿主免疫系统。此外，B37 和抗 PD1 Ab 的联合使用协同抑制肿瘤生长。这些结果表明，B37 可能是一种独特的 apo-IDO1 抑制介导的肿瘤免疫治疗候选药物。
