The present invention provides stable metastin derivatives having excellentbiological activities (a cancer metastasissuppressing activity, a cancer growth suppressing activity, a gonadotrophichormone secretion stimulating activity, sex hormonesecretion stimulating activity, etc.). By substituting the constituent aminoacids of metastin with specific amino acids in the metastinderivative of the present invention, blood stability, solubility, etc. aremore improved, gelation tendency is reduced, pharmacokineticsare also improved, and an excellent cancer metastasis suppressing activity ora cancer growth suppressing activity is exhibited.Furthermore, the metastin derivative of the present invention has the effectsof suppressing gonadotropic hormone secretion,suppressing sex hormone secretion, etc.
