Structure–activity Relationships of Glutathione Peroxidase 4 Inhibitor Warheads

Direct inhibition of GPX4 requires covalent modification of the active-site selenocysteine. While phenotypic screening has revealed that activated alkyl chlorides and masked nitrile-oxides can inhibit GPX4 covalently, a systematic assessment of potential electrophilic warheads with the capacity to inhibit cellular GPX4 has been lacking. Here we survey more than 25 electrophilic warheads across several distinct GPX4-targeting scaffolds. Surprisingly, we find that electrophiles with attenuated reactivity compared to chloroacetamides are unable to target GPX4. The highly reactive propiolamide warheads we uncover in this study highlight the potential need for masking strategies similar to those we have described for nitrile-oxide-based GPX4 inhibitors. Finally, our observations that there are spatial requirements between warhead and scaffold for achieving optimal GPX4 targeting and that certain low-molecular-weight analogs inhibit GPX4 with selectivity suggest that rational design of GPX4 inhibitors may be a productive approach. The generation of ligand-bound crystal structures to facilitate such studies should therefore be prioritized by the field.