Moreover, the treatment with GnRH-III-Dau conjugates cause a significant in vivo tumor growth and metastases inhibitory effect in three different orthotopic models, including 4T1 mice and MDA-MB-231 human breast carcinoma, as well as HT-29 human colorectal cancer bearing BALB/s and SCID mice, while toxic side-effects were substantially reduced in comparison to the treatment with the free drug. Here, GNRH1 is linked to breast carcinoma.