Synthesis and In Vitro Evaluation of Anticancer Activity of Fluorophenyl Derivatives of 1,3,4-Thiadiazole Against Estrogen-Dependent Breast Cancer

Breast cancer remains the most frequently diagnosed malignant tumor among women worldwide, and the limited selectivity as well as the emerging resistance to currently used therapies highlight the need to search for new therapeutic compounds. Aromatase, a key enzyme in the estrogen biosynthesis pathway, represents a recognized molecular target in the treatment of hormone-dependent cancers. In this study, six new 1,3,4-thiadiazole derivatives containing two halogen-substituted aromatic rings were designed and synthesized as potential nonsteroidal aromatase inhibitors. The cytotoxic activity of the obtained compounds was evaluated against two breast cancer cell lines: MCF-7 (estrogen-dependent) and MDA-MB-231 (estrogen-independent). All tested compounds exhibited concentration-dependent cytotoxic activity against MCF-7 cells, with the strongest effects observed for compounds <b>A2</b>, <b>A3</b>, <b>B1</b>, and <b>B3</b> (IC₅₀ ≈ 52-55 µM). In contrast, none of the tested compounds showed significant activity against MDA-MB-231 cells (IC₅₀ > 100 µM), suggesting their selectivity toward estrogen-dependent cancer cells. Compound <b>B3</b>, identified as the most promising, was further subjected to in silico analyses. Molecular docking and molecular dynamics simulations revealed that <b>B3</b> occupies a binding site similar to that of the co-crystallized native inhibitor and forms interactions characteristic of strong aromatase inhibitors. The obtained results confirm a mechanism of action related to aromatase inhibition and indicate that fluorophenyl-substituted 1,3,4-thiadiazole derivatives represent a promising scaffold for the design of new, selective, and less toxic aromatase inhibitors.