Antitumor agent-159 (Compound 13b) targets the mitochondria and downregulates cardiolipin levels. Antitumor agent-159 inhibits the proliferation of cancer cell MDA-MB-231, arrests the cell cycle at sub-G1 phase, and induces apoptosis in MDA-MB-231. Antitumor agent-159 exhibits antitumor efficacy in MDA-MB-231 xenograft mouse models.