Effect of Increasing Doses of Tiopronin on Cystine Capacity in Patients with Cystinuria

Brief description of study

The purpose of this study is to determine the effect of increasing dosages of Tiopronin (Thiola®) on the amount of cystine in the urine of individuals with cystinuria. Cystinuria is a rare inherited disease that results in the frequent formation of kidney stones. Patients with cystinuria have an abnormality in the way the kidneys handle cystine, an amino acid. This abnormality results in an excessive amount of cystine excreted into the urine. Cystine doesn't dissolve well in urine and therefore, compacts together to form stones. While Tiopronin is approved by the FDA for this condition, the research team will be administering the drug at doses that have not been FDA-approved. For this reason, some of the doses of the drug in this study are considered experimental. This study hopes to find the best dosage of Tiopronin that should be given to cystinuria patients in order to allow the urine to take up more cysteine and thus reduce the chance of kidney stones. Although Tiopronin is normally given as per standard of care, there is no set guideline to the best prescribed dosage. Therefore, this allows dosages to be too small, resulting in kidney stones; or too large, resulting in unnecessary side effects. This study will directly measure the cystine capacity in response to increasing doses of Tiopronin to determine if there is a dose at which the maximum benefit of the drugs exists, while accounting for the goal to help guide therapy and ultimately minimize unnecessary side effects caused by large dosages. The cystine capacity will be measured by using a test called CysCap, which was developed by the Litholink Corporation. Overall, we hope that tailoring the drug dosages to the effect on the urine cystine will improve the treatment and quality of life for patients with cystinuria.

Clinical Study Identifier: s18-00642
ClinicalTrials.gov Identifier: NCT03663855
Principal Investigator: David S. Goldfarb
Currently Recruiting

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