Design, synthesis, and antitumor evaluation of celastrol derivatives targeting PRDX3.

Peroxiredoxin 3 (PRDX3), located in mitochondria, plays a crucial catalytic role in maintaining mitochondrial redox homeostasis and represents a promising target for antitumor drug development. Celastrol is a natural inhibitor of PRDX3; however, it suffers from poor subtype selectivity and high toxicity. In this study, celastrol was used as a lead compound for structural optimization. First, we demonstrated that introducing a triphenylphosphine (TPP) group enables mitochondrial targeting and reduces cytotoxicity. Subsequently, the TPP moiety was exploited as a privileged fragment for further optimization. After two rounds of structural modification, compound 10d was obtained, exhibiting the best antiproliferative activity. Its key structural features include a TPP group attached at the C-3 position and an ethylamine fragment linked at the C-20 position. Compound 10d showed an IC50 value of 0.64 μM against H1975 cells, approximately 3-fold more potent than celastrol. Mechanistic studies revealed that 10d binds to PRDX3 with high affinity (Kd = 0.514 μM), about 17-fold higher than that of celastrol (Kd = 8.56 μM). Furthermore, 10d downregulated the downstream NF-κB and VEGF signaling pathways of PRDX3, effectively suppressing migration and invasion of H1975 cells. In vivo efficacy evaluation demonstrated that 10d exhibited significantly superior tumor suppression in a subcutaneous xenograft model of H1975 tumors compared to celastrol, without causing notable systemic toxicity such as significant body weight loss. In summary, this study successfully developed a highly effective and safe mitochondrially targeted PRDX3 inhibitor, providing a valuable lead compound for the development of innovative drugs targeting tumor redox metabolism.