Discovery of 4-hydroxyl pyrazole derivatives as potent ferroptosis inhibitors.

Ferroptosis, an iron-dependent form of regulated cell death, has been well recognized as a pathogenic mechanism in driving many diseases, such as neurodegenerative disorders, ischemia-reperfusion (I/R) injury. Blocking ferroptosis has been emerging as a feasible therapeutic strategy for the prevention and treatment of these diseases. However, novel potent ferroptosis inhibitors remain to be developed for further clinical applications. In this study, we screened our in-house compound libraries by phenotypic assays and identified a 4-hydroxyl pyrazole derivative HW-3 with good ferroptosis inhibitory activity (EC50 = 120.1 ± 3.5 nM). Based on the structure of HW-3, a series of 4-hydroxyl pyrazole derivatives were further designed and synthesized. Among these compounds, compound 25 could significantly inhibit RSL3-induced ferroptosis with an EC50 value of 8.6 ± 2.2 nM in HT-1080 cells, which was 3-fold more potent than the classical ferroptosis inhibitor ferrostatin-1 (Fer-1) (EC50 = 23.4 ± 1.3 nM). The potent ferroptosis inhibitory activity of compound 25 was further validated in multiple additional cell lines. Our mechanistic study revealed that compound 25 inhibited ferroptosis via intrinsic radical-trapping antioxidative capacity. Taken together, the findings of our study demonstrate 4-hydroxyl pyrazole derivative 25 is a potent ferroptosis inhibitor, which holds a great therapeutic potential for further development.