Fatty acid synthase (FASN) expression is elevated in several cancers and is associated with poor prognosis. Although several FASN inhibitors have been developed, they are associated with selectivity issues and toxicity. Alwarawrah et al. have now identified Fasnall, a novel, selective thiophenopyrimidine-based FASN inhibitor. Fasnall exhibited potent broad antitumour activity against various breast cancer cell lines and was well tolerated in mice. Moreover, Fasnall reduced tumour volume and increased survival in a mouse breast cancer model.