D[LEU4,LYS8]-VP TFA is a selective agonist of vasopressin V1b receptor, with the Kis of 0.16 nM, 0.52 nM, and 0.1.38 nM for rat, human and mouse V1b receptor, respectively. D[LEU4,LYS8]-VP TFA has weak antidiuretic, vasopressor, and in vitro oxytocic activities.