GPX4 inhibitors (Hainan University)

A highly selective ferroptosis inducer with drug-like properties can significantly advance the research on inducing ferroptosis for anticancer treatment. We previously reported a highly active GPX4 inhibitor 26a, but its activity and stability need further improvement. In this work, a novel GPX4 inhibitor (R)-9i with more potent cytotoxicity (IC₅₀ = 0.0003 μM against HT1080) and ferroptosis selectivity (selectivity index = 24933) was gained via further electrophilic warhead screening and structure-based optimization. The cellular thermal shift assay (CETSA) indicated that (R)-9i could stabilize GPX4 with a T_m value of 6.2 °C. Furthermore, (R)-9i showed strong binding affinity against GPX4 (K_D = 20.4 nM). More importantly, (R)-9i has more favorable pharmacokinetic properties than 26a, which endowed (R)-9i with potential in antitumor research and as a tool drug for further study of ferroptosis. Associated with these, (R)-9i treatment significantly inhibited tumor growth in the xenograft tumor mouse model without detectable toxicity.

Ferroptosis is a non-apoptotic mode of cell death characterized by iron-dependent accumulation of lipid peroxidation. While lipid radical elimination reaction catalyzed by glutathione peroxidase 4 (GPX4) is a major anti-ferroptosis mechanism, inhibiting this pathway pharmaceutically shows promise as an antitumor strategy. However, certain tumor cells exhibit redundancy in lipid radical elimination pathways, rendering them unresponsive to GPX4 inhibitors. In this study, we conducted screens across different cancer cell lines and Food and Drug Administration-approved drugs, leading to the identification of temsirolimus in combination with the GPX4 inhibitor RSL3 as a potent inducer of ferroptosis in liver cancer cells. Mechanistically, temsirolimus sensitized liver cancer cells to ferroptosis by directly binding to and inhibiting ferroptosis suppressor protein 1 (FSP1) enzyme. Notably, while temsirolimus is recognized as a potent mammalian target of rapamycin (mTOR) inhibitor, its ferroptosis-inducing effect is primarily attributed to the inhibition of FSP1 rather than mTOR activity. By employing in vitro colony formation assays and in vivo tumor xenograft models, we demonstrated that the combination of temsirolimus and RSL3 effectively suppressed liver tumor progression. This tumoricidal effect was associated with increased lipid peroxidation and induction of ferroptosis. In conclusion, our findings underscore the potential of combining multitarget ferroptosis-inducing agents to circumvent the resistance to ferroptosis of liver cancer cells and highlight temsirolimus as a promising FSP1 inhibitor and ferroptosis inducer, which also deserves further investigation in translational medicine.