It is well recognized that many
cancers are addicted to a constant supply of
fatty acids (FAs) and exhibit brisk de novo FA synthesis. Upregulation of a key lipogenic
enzyme,
fatty acid synthase (FASN), is a near-universal feature of human
cancers and their precursor lesions, and has been associated with chemoresistance,
tumor metastasis, and diminished patient survival. FASN inhibition has been shown to be effective in killing
cancer cells, but progress in the field has been hindered by off-target effects and poor
pharmaceutical properties of candidate compounds. Our initial hit (compound 1) was identified from a high-throughput screening effort by the Sanford-Burnham Center for Chemical Genomics using purified FASN thioesterase (FASN-TE) domain. Despite being a potent inhibitor of purified FASN-TE, compound 1 proved highly unstable in mouse plasma and only weakly cytotoxic to
breast cancer (BC) cells in vitro. An iterative process of synthesis, cytotoxicity testing, and plasma stability assessment was used to identify a new lead (compound 41). This lead is more cytotoxic against multiple BC cell lines than tetrahydro-4-methylene-2S-octyl-5-oxo-3R-furancarboxylic
acid (the literature standard for inhibiting FASN), is stable in mouse plasma, and shows negligible cytotoxic effects against nontumorigenic mammary epithelial cells. Compound 41 also has
drug-like physical properties based on Lipinski's rules and is, therefore, a valuable new lead for targeting
fatty acid synthesis to exploit the requirement of
tumor cells for
fatty acids. SIGNIFICANCE STATEMENT: An iterative process of synthesis and
biological testing was used to identify a novel thioesterase domain FASN inhibitor that has
drug-like properties, is more cytotoxic to
breast cancer cells than the widely used tetrahydro-4-methylene-2S-octyl-5-oxo-3R-furancarboxylic
acid, and has negligible effects on the growth and proliferation of noncancerous mammary epithelial cells. Our studies have confirmed the value of using potent and selective FASN inhibitors in the treatment of BC cells and have shown that the availability of exogenous
lipoproteins may impact both
cancer cell FA metabolism and survival.