Thus, the GnRH-II antagonist [Ac-D2Nal1, D-4Cpa2, D-3Pal3,6, Leu8, D-Ala10]GnRH-II seems to be a suitable drug for an efficacious and less-toxic endocrine therapy for breast cancers, including triple-negative breast cancers. Here, GNRH2 is linked to breast cancer.