The primary endpoint of the trial was the change in estimated glomerular filtration rate (eGFR) from pre-treatment baseline levels to post-treatment assessment. In patients treated with tolvaptan the reduction in eGFR was significantly less than in patients treated with placebo (p<0.0001). eGFR is an estimate of the sum of the filtration rates of all single functional nephrons (filtering units) in the kidneys, measured through creatinine-based estimation equations.1 The difference observed in this study represents a 35% reduction in the loss of kidney function compared to placebo in these patients over the course of one year. The key secondary endpoint was a comparison of the efficacy of tolvaptan treatment versus placebo in reducing the decline of annualized eGFR slope across all measured time points in the study. These data also showed significant benefit from tolvaptan vs. placebo (p<0.0001).
The trial was completed to supply confirmatory data to the previous study2 to address the Complete Response Letter (CRL) issued by the U.S. Food and Drug Administration (FDA) in 2013 for a New Drug Application (NDA) for tolvaptan in the treatment of adults with ADPKD.
The Phase 3, multicenter, international, randomized-withdrawal, placebo-controlled, double-blind trial compared the efficacy and safety of tolvaptan (45 to 120 mg/day) to placebo. Trial enrollees were adults 18 to 65 years of age with ADPKD-induced chronic kidney disease between late stage 2 to early stage 4 (eGFR ranging from 65-25 mL/min) and not previously treated with tolvaptan. A total of 1,370 patients were randomized to either tolvaptan or placebo and were treated for a period of 12 months.3
There were no new safety issues identified for tolvaptan during the trial. As in the prior study,2 tolvaptan resulted in more patients than placebo with increased (>3x upper limit of normal (ULN)) levels of liver enzymes alanine aminotransferase (ALT; 5.6% vs. 1.2%) and aspartate aminotransferase (AST; 3.5% vs. 0.9%); however, none of these patients exhibited total bilirubin greater than 2x ULN. The most common adverse events associated with tolvaptan (incidence >5% and at least 1% more frequent than placebo) included diarrhea (6.9% vs. 3.4%), fatigue (6.8% vs 3.5%) and polyuria (5.3% vs. 1.6%).
Results from the trial will be submitted for presentation at a nephrology medical congress in the second half of 2017.
About Tolvaptan and ADPKD
Tolvaptan is a selective vasopressin V2-receptor antagonist. By selectively blocking vasopressin at the V2-receptor, tolvaptan has been shown to decrease cyst-cell proliferation and fluid secretion, ultimately reducing cyst development.4 In a previous Phase 3 clinical trial, tolvaptan was associated with reduced kidney growth and slowed decline of kidney function.2
ADPKD, a multi-systemic disease that is caused by inherited or acquired genetic mutation(s), is characterized by the formation and enlargement of cysts.5 Cyst growth and proliferation eventually lead to kidney damage, and often cause complications that include pain and hypertension.6,7 Up to 50% of patients require renal replacement therapy by the age of 60.6 In addition to the physical effects, ADPKD causes psychological and emotional burden for those living with the disease and their loved ones.8
Tolvaptan is approved for the treatment of adult patients with ADPKD in Japan, the EU and other countries (see local prescribing information for specific indications in each country).
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1 Lascano M., Poggio E. Kidney function assessment by creatinine-based estimation equations. Cleveland Clinic, Center For Continuing Education. 2010. [Accessed May 15, 2017] http://www.clevelandclinicmeded.com/medicalpubs/diseasemanagement/nephrology/kidney-function/
2 Torres VE, Harris PC et al. Tolvaptan in patients with autosomal dominant polycystic kidney disease. NEJM. 2012;367 (25): 2407-2418
3 Torres VE, Devuyst, O et al. Rationale and design of a clinical trial investigating tolvaptan safety and efficacy in autosomal dominant polycystic kidney disease. Am J Nephrol. 2017; 45 (3), 257-266
4 Reif, GA, Yamaguchi, T et al. Tolvaptan inhibits ERK-dependent cell proliferation, Cl – secretion, and in vitro cyst growth of human ADPKD cells stimulated by vasopressin. Am J Physiol Renal Physiol; 2011; 301:F1005-F1013
5 Tan Y, Blumenfeld J, and Rennert H. Autosomal dominant polycystic kidney disease: genetics, mutations and microRNAs. Biochimica Biophysica Acta. 2011;1812:1202-1212
6 Torra, R. Polycystic kidney disease. Medscape. 2017. [Accessed May 19, 2017] http://emedicine.medscape.com/article/244907-overview
7 Thong KM, Ong ACM. The natural history of autosomal dominant polycystic kidney disease: 30-year experience from a single centre. QJM. 2013;2-8
8 Baker A, King D et al. Understanding the physical and emotional impact of early-stage ADPKD: experiences and perspectives of patients and physicians. Clin Kidney J. 2015; 8(5): 531–537