Allen Davidoff, PhD, CEO of XORTX Therapeutics, discusses two phase 3 studies set to launch in the next two years evaluating oxypurinol in patients with autosomal dominant polycystic kidney disease (ADPKD).

ADPKD is a genetic disorder characterized by the formation of cysts in the kidneys. The most common symptoms – hypertension, flank pain, hematuria, and kidney insufficiency – are caused by cyst formation. In most patients, ADPKD leads to end-stage renal disease which requires either dialysis or a kidney transplant. ADPKD is caused by mutations of one of two genes responsible for proper function of the kidneys and other parts of the body. Approximately 85% have ADPKD1, the most aggressive form of the disease. 

As Dr. Davidoff explains, there is evidence that aberrant purine metabolism and increased serum uric acid, when increased above the upper limit of normal, is a causative mediator of hypertension. There is additional evidence suggesting a role of hyperuricemia in the development of endothelial dysfunction, insulin resistance, diabetes and diabetic nephropathy. As an xanthine oxidase inhibitor, oxypurinol is thought to manage aberrant purine metabolism and chronically high serum uric acid concentration

The first study will be a phase 3, multi-center, double-blind, placebo controlled, randomized withdrawal design study to evaluate the efficacy and safety of daily oxypurinol tablets in patients with progressing stage 2-4 ADPKD and coexisting hyperuricemia. This study will provide data to hopefully support “accelerated approval” submissions to regulatory bodies in the U.S. and Europe. This study is planned to start in the second half of 2023. The objective of this study is to evaluate the ability of oxypurinol to slow the expansion of total kidney volume over a 12-month treatment period.

The second study will be similar in design but the objective of this study will be to evaluate the safety and effectiveness of oxypurinol over a 24-month treatment period. The aim of the study will be to characterize the ability of oxypurinol to decrease the rate of decline of glomerular filtration rate. An estimated 300 patients will be enrolled. This study is planned to start in the second half of 2024, subject to Special Protocol Assessment negotiations with the FDA. 

To learn more about the clinical trials and how to register, visit 

To learn more about ADPKD and other rare kidney disorders, visit