Exchange of extracellular cystine for intracellular glutamate by the antiporter system x_c⁻is implicated in numerous pathologies. Pharmacological agents that inhibit system x_c⁻activity with high potency have long been sought, but have remained elusive. In this study, we report that the small molecule erastin is a potent, selective inhibitor of system x_c⁻. RNA sequencing revealed that inhibition of cystine–glutamate exchange leads to activation of an ER stress response and upregulation ofCHAC1, providing a pharmacodynamic marker for system x_c⁻inhibition. We also found that the clinically approved anti-cancer drug sorafenib, but not other kinase inhibitors, inhibits system x_c⁻function and can trigger ER stress and ferroptosis. In an analysis of hospital records and adverse event reports, we found that patients treated with sorafenib exhibited unique metabolic and phenotypic alterations compared to patients treated with other kinase-inhibiting drugs. Finally, using a genetic approach, we identified new genes dramatically upregulated in cells resistant to ferroptosis.

Ferrostatin-1 (Fer-1) inhibits ferroptosis, a form of regulated, oxidative, nonapoptotic cell death. We found that Fer-1 inhibited cell death in cellular models of Huntington’s disease (HD), periventricular leukomalacia (PVL), and kidney dysfunction; Fer-1 inhibited lipid peroxidation, but not mitochondrial reactive oxygen species formation or lysosomal membrane permeability. We developed a mechanistic model to explain the activity of Fer-1, which guided the development of ferrostatins with improved properties. These studies suggest numerous therapeutic uses for ferrostatins, and that lipid peroxidation mediates diverse disease phenotypes.

Significance: Cell death by regulated necrosis causes tremendous tissue damage in a wide variety of diseases, including myocardial infarction, stroke, sepsis, and ischemia–reperfusion injury upon solid organ transplantation. Here, we demonstrate that an iron-dependent form of regulated necrosis, referred to as ferroptosis, mediates regulated necrosis and synchronized death of functional units in diverse organs upon ischemia and other stimuli, thereby triggering a detrimental immune response. We developed a novel third-generation inhibitor of ferroptosis that is the first compound in this class that is stable in plasma and liver microsomes and that demonstrates high efficacy when supplied alone or in combination therapy.

Modulatory profiling of lethal small-molecule compounds identified FIN56 as an inducer of ferroptosis. FIN56 promotes the degradation of glutathione peroxidase 4 and directly activates squalene synthase, an enzyme involved in cholesterol synthesis. Apoptosis is one type of programmed cell death. Increasingly, non-apoptotic cell death is recognized as being genetically controlled, or 'regulated'. However, the full extent and diversity of alternative cell death mechanisms remain uncharted. Here we surveyed the landscape of pharmacologically accessible cell death mechanisms. In an examination of 56 caspase-independent lethal compounds, modulatory profiling showed that 10 compounds induced three different types of regulated non-apoptotic cell death. Optimization of one of those ten resulted in the discovery of FIN56, a specific inducer of ferroptosis. Ferroptosis has been found to occur when the lipid-repair enzyme GPX4 is inhibited. FIN56 promoted degradation of GPX4. FIN56 also bound to and activated squalene synthase, an enzyme involved in isoprenoid biosynthesis, independent of GPX4 degradation. These discoveries show that dysregulation of lipid metabolism is associated with ferroptosis. This systematic approach is a means to discover and characterize novel cell death phenotypes.