The present invention belongs to the field of medical technology. Particularly, the present invention relates to a compound shown in formula (I), a pharmaceutically acceptable salt thereof, and a stereoisomer of the same. X, Y, Z, R<；sup>；1<；/sup>；, R<；sup>；2<；/sup>；, R<；sup>；3<；/sup>；, R<；sup>；1a<；/sup>；, R<；sup>；2a<；/sup>；, m, and n are as defined in the specification. The present invention also relates to pharmaceutical preparations and pharmaceutical compositions of these compounds and a use thereof in preparing a drug for treating a related disease mediated by abnormal indoleamine 2,3-dioxygenase (IDO).
