CYD-4-61 is a novel Bax activator used for breast cancer research. CYD-4-61 inhibits triple-negative breast cancer MDA-MB-231 and ER-positive breast cancer MCF-7 cell lines proliferation. CYD-4-61 activates Bax protein to induce cytochrome c release and regulate apoptotic biomarkers, leading to cancer cell apoptosis.