Background <p>Hypoxia-inducible factor prolyl hydroxylase inhibitor (HIF-PHI) represents a novel therapeutic approach for renal anemia, a prevalent complication of chronic kidney disease (CKD). However, the effects of HIF-PHI on renal functional outcomes remain poorly characterized. Here, the potential effects of FG-4592, an orally administered HIF-PHI, on renal fibrosis were explored systematically.</p> Methods <p>In this study, a CKD rat model was established through subtotal 5/6 nephrectomy. Rats were administered either FG-4592 or vehicle control via oral gavage three times weekly for 12 consecutive weeks. Additionally, recombinant FGF23 was continuously delivered via subcutaneously implanted Alzet osmotic minipumps for 28 days.</p> Results <p>Interestingly, we found that CKD-induced anemia was significantly ameliorated in CKD rats with FG-4592 treatment. Meanwhile, markedly alleviated histopathological changes and renal tubulointerstitial fibrosis (TIF) were observed in rats with FG-4592 administration. Notably, serum levels of intact FGF23 (iFGF23) were significantly reduced following FG-4592 administration in CKD rats. This finding was subsequently validated in CKD patients receiving Roxadustat therapy. Mechanistically, we illustrated that inhibition of the iFGF23-WNT5A pathway was the exact mechanism by which FG-4592 ameliorated TIF. Further, we also demonstrated that transcriptional activation of Furin enzyme was the exact molecular mechanism for FG-4592-mediated iFGF23 cleavage.</p> Conclusions <p>FG-4592 attenuates TIF through Furin-mediated proteolytic cleavage of iFGF23. These findings provide novel mechanistic insights into HIF-PHI-mediated renal protection and establish a theoretical framework for clinical translation.</p>