Background: Autosomal-dominant polycystic kidney disease (ADPKD) is an inherited renal cystic disease that leads to end-stage renal disease. Patients who present with symptoms at an early age are more likely to live to develop end stage renal disease. Patients with ADPKD and renal failure are most commonly treated with hemodialysis. Tolvaptan is expected to be effective in the treatment of ADPKD because of its success in animal models. If clinical trials can prove slowing of the disease progression, hemodialysis and kidney transplant for those patients may not be necessary. What is the effectiveness of tolvaptan as a treatment option for ADPKD to inhibit renal cyst progression?
Method: An exhaustive literature search was done using the following search engines, MEDLINE, CINAHL, EMBR, Web of Science, and the initial search used the following combined search terms as treatment, clinical trial, and polycystic kidney disease. The bibliographies of the articles were further searched for relevant sources. Articles with primary data evaluating ADPKD were included. Relevant articles were assessed for quality using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE). A search on the National Institute of Health (NIH) clinical trials site was done.
Results: Two studies met inclusion criteria and were included in this systematic review. The result of the 3 year study found tolvaptan to be significant in slowing down the total kidney volume (TKV), which is related to the cyst progression in kidneys. Cyst growth progressed more slowly in the tolvaptan treated patients than in the historical controls. The secondary objective of eGFR was also measured, but was not found to be significant in maintaining the filtration rate, even though the trend is more noticeable than in the control group. The other study was a 1-week administration of tovaptan where the result was analyzed post hoc. The post hoc blinded analysis of renal MRI showed a significant 3.1% reduction in the TKV from baseline after 1 week of tolvaptan with P-value
Conclusion: Tolvaptan showed a positive result on inhibition of renal cysts growth in patients with ADPKD, but it does not have a significant effect on the other outcomes, such as slowing progression of GFR, which measures kidney’s failure and its progression to ESRD. Further studies such as TEMPO (an NIH phase 2 registered trial), may show more evidence of slowing down the disease progression and tolvaptan drug alteration may be necessary to reduce AEs and be more of an appropriate drug to treat ADPKD.
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