Metformin vs Tolvaptan for Treatment of Autosomal Dominant Polycystic Kidney Disease

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited renal disorder occurring in 1:400-1:1.000 live births and affects 4 to 6 million persons worldwide and about 205.000 people in Europe (EU). This figure is equivalent to 4 in 10.000 people and thus below the prevalence threshold of 5 in 10.000 used to designate a disease as rare in EU. Renal cyst development and expansion in ADPKD involves both fluid secretion and abnormal proliferation of cyst-lining epithelial cells. The chloride channel of the cystic fibrosis transmembrane conductance regulator (CFTR) participates in secretion of cyst fluid, and the mammalian target of rapamycin (mTOR) pathway may drive proliferation of cyst epithelial cells. CFTR and mTOR are both negatively regulated by AMP-activated protein kinase (AMPK). Metformin, a drug widely used, is a pharmacological activator of AMPK. The investigators found that metformin stimulates AMPK, resulting in inhibition of both CFTR and the mTOR pathways. Metformin induces significant arrest of cystic growth in both in vitro and ex vivo models of renal cystogenesis. In addition, metformin administration produces a significant decrease in the cystic index in two mouse models of ADPKD. These results suggest a possible role for AMPK activation in slowing renal cystogenesis as well as the potential for therapeutic application of metformin in the context of ADPKD. Thus this study aims to evaluate metformin efficacy in slowing renal cystogenesis in ADPKD as compared to the actual gold standard (Tolvaptan).