Metastin derivatives and use thereof

Disclosed is a metastin derivative of the pictured formula, or a salt thereof. Each XX group represents an amino acid or a similar group as defined in the specification. Also disclosed is the use of the metastin derivative for treating cancer, choriocarcinoma, hydatid mole, invasive mole, miscarriage, fetal hypoplasia, abnormal glucose metabolism, abnormal lipid metabolism or induction of delivery, hormone-dependent cancer, infertility, endometriosis, early puberty, myoma of the uterus, Alzheimer's disease, Autism or moderate cognitive impairment. Also disclosed is the use of the metastin derivative for controlling placental function, improving gonadal function, inducing or stimulating ovulation.