Fasnall, a fatty acid synthase (FASN) inhibitor, exhibits an IC50 of 3.71 μM against the human recombinant enzyme. It halts tritiated acetate incorporation into lipids (IC50= 5.84 μM), boosts ceramide levels, and triggers lipid droplet formation in BT474 HER2+ breast cancer cells. Demonstrating antiproliferative effects on various breast cancer cell lines, including non-tumorigenic MCF-10A and tumorigenic MCF-7, MDA-MB-468, BT474, and SK-BR-3, its efficacy is directly linked to FASN expression in vitro. In murine models of HER2+ breast cancer, particularly the MMTV-Neu model, Fasnall significantly reduces tumor volume and extends survival. Furthermore, it enhances the efficacy of carboplatin in vivo, bolstering the objective response rate of stable disease from 25% with carboplatin alone to 88% when paired with Fasnall.