KLOTHO AS A THERAPEUTIC TARGET IN RENAL FIBROSIS: MECHANISMS, PHARMACOLOGY, PRECLINICAL EVIDENCE, AND TRANSLATIONAL PRIORITIES

Renal fibrosis is the convergent lesion of progressive chronic kidney disease (CKD), yet no approved drug directly reverses established renal scarring. The kidney is the major source of α-Klotho, a single-pass transmembrane protein whose extracellular domain is shed into the circulation and urine. Loss of renal Klotho is an early and potentially pathogenic feature of kidney injury. In experimental disease, Klotho replacement or expression suppresses fibrosis through convergent inhibition of transforming growth factor-β (TGF-β), Wnt/β-catenin, renin–angiotensin, endothelial-to-mesenchymal transition, oxidative/mitochondrial injury, cellular senescence, and maladaptive cell-cycle arrest. The most clinically interesting pharmacologic concepts are recombinant soluble Klotho, Klotho gene delivery, and smaller Klotho-derived peptides. Recombinant protein has shown benefit in ischemia–reperfusion, unilateral ureteral obstruction, remnant-kidney, adriamycin, and phosphate-loading models; a 30-amino-acid peptide (KP1) that binds TGF-β receptor 2 (TβR2) has preferentially accumulated in injured kidneys and reduced fibrosis after intravenous dosing. More recently, injury-targeted nanoparticles carrying Klotho plasmid prevented acute kidney injury (AKI)–CKD transition in mice through a PPARα/lipid-metabolism mechanism. These results establish biological plausibility, not clinical efficacy. Translation is constrained by protein production and stability, short or incompletely characterized exposure, tissue delivery, mineral-metabolism liabilities, immunogenicity and gene-therapy safety, disease heterogeneity, and non-standardized soluble-Klotho assays. The field should therefore prioritize kidney-targeted, exposure-defined interventions tested against contemporary CKD standard of care, with hard renal outcomes and validated pharmacodynamic assays.