Development of a Highly Selective Ferroptosis Inducer Targeting GPX4 with 2-Ethynylthiazole-4-carboxamide as Electrophilic Warhead

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.