Melatonin-Tamoxifen Conjugate (compound 16c) is an anticancer drug conjugate made of Melatonin and Tamoxifen, serving as an effective antagonist of ERα (IC50 = 863 nM). In cells expressing the hMT1 receptor, it binds to MLT receptors (Ki = 3.1 nM) and exhibits the ability to promote β-arrestin activation (EC50 = 914 nM) and ERK activation (EC50 = 98 nM). The IC50 values for Melatonin-Tamoxifen Conjugate in MCF-7, MDA-MB-231, and HT-1080 cell lines are 6.8 μM, 6.4 μM, and 1.7 μM, respectively.