Efficacy and safety of tolvaptan versus placebo in the treatment of patients with autosomal dominant polycystic kidney disease: a meta-analysis

A Snake Toxin Derivative for Treatment of Hyponatremia and Polycystic Kidney Diseases

Key Points

MQ232, a disulfide-bond reticulated peptide derived from a natural snake toxin, was optimized as a new aquaretic drug candidate. MQ232 showed very low acute and chronic toxicity in rat and a biodistribution in mice strongly in favor of the kidney organs. MQ232 induced a sole aquaretic effect and demonstrated high in vivo activities on hyponatremia and polycystic kidney disease models.

Background

Vaptans were developed at the end of the previous century as vasopressin type 2 receptor antagonists. Tolvaptan is the most prescribed vaptan for hyponatremia and autosomal dominant polycystic kidney disease (ADPKD). However, its use is not as widespread as it should be due to price issues, a narrow therapeutic window, and some side effects. With the aim of discovering new efficient and safer vasopressin type 2 receptor antagonists, we screened animal venoms and identified several peptide toxins. Among them, mambaquaretin 1 (MQ1) displayed unique biological properties in that regard that it was the starting point for the development of a potential drug candidate.

Methods

Human T-cell assays and bioinformatics were used to mitigate MQ1 immunogenicity risk. MQ232 biodistribution in mice was performed by positron emission tomography. Pharmacodynamics, pharmacokinetics, and acute and chronic toxicity tests were performed on control rats. A rat experimental model of desmopressin-induced hyponatremia, ex vivo mice model of kidney cysts, and mice orthologous model of ADPKD were used to validate MQ232 efficacy in these pathologies.

Results

Three mutations were introduced in MQ1 to mitigate its immunogenicity risk. A fourth gain-of-function mutation was added to generate MQ232. MQ232's safety was demonstrated by a first toxic dose as high as 3000 nmol/kg and a strong kidney organ selectivity by positron emission tomography imaging, while showing almost no interaction with the liver. MQ232's efficacy was first demonstrated with an effective dose of 3 nmol/kg in a hyponatremic model and then in polycystic kidney models, on which MQ232 significantly reduced cyst growth.

Conclusions

We demonstrated, using diverse translational techniques and minimizing animal use, MQ232's safety and efficacy in several rodent models of hyponatremia and ADPKD.

Effectiveness of tolvaptan on renal replacement therapy in patients with autosomal dominant polycystic kidney disease: a retrospective cohort study from the TriNetX global collaborative network

BACKGROUND AND HYPOTHESIS

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major genetic contributor to end-stage kidney disease (ESKD). Current evidence on tolvaptan primarily focuses on slowing estimated glomerular filtration rate (eGFR) decline and kidney volume growth. However, direct confirmation of its effectiveness in reducing the need for hemodialysis in ESKD remains limited.

METHODS

We included ADPKD patients aged ≥18 years using TriNetx data from Sep 2, 2018, to Sep 3, 2023. Propensity score matching (PSM) ensured baseline comparability (standardized mean difference (SMD) <0.1). Hazard ratios (HRs) with 95% confidence intervals (CIs) evaluated outcomes, and subgroup analyses were performed.

RESULTS

After 1:1 PSM, both groups comprised 673 patients. The average age was 45, with generally good health (3-5% diabetes, 2-3% ischemic heart disease). Baseline eGFR averaged ∼55 ml/min/1.732m2. Post-matching, all SMDs were <0.1, indicating successful matching. Tolvaptan users exhibited lower eGFR (51.45 ± 30.09 vs. 57.37 ± 33.65, p < 0.001) and higher risk of stage 4-CKD (HR: 2.436, 95% CI:1.649, 3.599) compared to non-users. However, tolvaptan users showed significantly reduced chances of initiating hemodialysis (HR:0.362, 95%CI:0.176, 0.745), experiencing urinary tract infections (HR:0.581, 95%CI:0.354, 0.956), and all-cause mortality (HR:0.355, 95% CI:0.180, 0.700). Kaplan-Meier curves for hemodialysis initiation indicated higher survival rates among tolvaptan users across age and number of medication refill subgroups.

CONCLUSIONS

This real-world study, employing precise matching, reveals tolvaptan's role in reducing hemodialysis initiation risk in ADPKD, despite initial hemodynamic-induced lower eGFR.

Low-dose tolvaptan to control disease progression in Chinese patients with autosomal dominant polycystic kidney disease: a retrospective cohort study

Background

Tolvaptan has been shown to be effective in the treatment of autosomal dominant polycystic kidney disease (ADPKD). However, there is limited evidence regarding optimal dosing and its application within the Chinese population. In this study, we aimed to determine whether a lower tolvaptan dose could effectively control ADPKD in Chinese patients.

Methods

This retrospective, single-center cohort study was conducted in a real-world setting and included all patients newly diagnosed with rapidly progressive ADPKD who initiated tolvaptan treatment and maintained it for at least 12 months. Data were collected at baseline and at 1, 2, 4, 8, and 12 months after treatment initiation. Patients began with morning/evening tolvaptan doses of 7.5 mg/7.5 mg, and the dose was subsequently adjusted based on effectiveness and tolerability. The patients were categorized by baseline estimated glomerular filtration rate (eGFR) and final daily tolvaptan dose. Changes in eGFR and other key physiological indicators after treatment were compared within each group.

Results

The study included 43 patients with ADPKD, of whom 20 were female, with a median age of 34.3 years (range, 16-85 years). At 12 months, eGFR improved by 5.48 mL/min/1.73 m2 [95% confidence interval (CI): 2.68-8.29] (P<0.001) compared to baseline. Significant improvements were observed in patients with baseline eGFR levels of 30-59, 60-89, and ≥90 mL/min/1.73 m2 (P=0.007, 0.045, and 0.02, respectively), as well as in medium and high dose groups (P=0.002 and 0.02, respectively). At 12 months, the annual height-adjusted total kidney volume (HtTKV) growth slope decreased by -0.17 %/year (95% CI: -0.33 to -0.01) (P=0.04). Significant decreases were observed in patients with an eGFR of 30-59 mL/min/1.73 m2 (P=0.008) and in the medium dose group (P=0.03). Thirst was reported in 22 (51.2%) patients, all of whom experienced mild symptoms. No liver-associated adverse events were noted.

Conclusions

Tolvaptan is well tolerated at low initial doses in Chinese patients with ADPKD. Significant improvements in eGFR and reduced HtTKV growth were observed in the overall population and across various baseline eGFR and final dose groups.

Evaluation of tolvaptan-associated hepatic disorder using different national pharmacovigilance databases

Tolvaptan-associated hepatic disorder is a rare, but lethal adverse event; however, the precise risk and time of onset remain unclear. This study aimed to characterize the severity, time‑to‑onset, and outcomes of hepatic disorder based on patient age and sex. Patient data were acquired from the Japanese Adverse Drug Event Report database (JADER) and the JAPIC AERS database, which consists of the U.S. Food and Drug Administration Adverse Event Reporting System (FAERS) processed by the Japan Pharmaceutical Information Center. Hepatic disorder was classified as severe or nonsevere. Tolvaptan use was associated with hepatic disorder in analyses using the FAERS [Severe hepatic disorder: reporting odds ratio (ROR) 4.93, 95% confidence interval (CI) 4.33‒5.61; information component (IC) 2.11, 95% CI 1.92‒2.29; nonsevere hepatic disorder: ROR 6.78, 95% CI 6.01‒7.65; IC 2.51, 95% CI 2.33‒2.68] and the JADER (severe hepatic disorder: ROR 4.21, 95% CI 3.57‒4.97; IC 1.86, 95% CI 1.63‒2.10; nonsevere hepatic disorder: ROR 4.27, 95% CI 3.68‒4.95; IC 1.83, 95% CI 1.62‒2.04). A time‑to‑onset analysis revealed that the median onset time was significantly longer in patients aged < 60 years compared with patients aged ≥ 60, regardless of the severity (FAERS: severe hepatic disorder 7 vs. 58 days, p < 0.0001; nonsevere hepatic disorder 8 vs. 52.5 days, p < 0.0001; JADER: severe hepatic disorder 9.5 vs. 32 days, p = 0.0017; nonsevere hepatic disorder 9 vs. 89 days, p < 0.0001). Severe outcomes were observed, regardless of the severity of hepatic disorder. Patients should be monitored for liver function based on age to prevent fatal outcomes.

[Kidney involvement in rare hereditary diseases]

Various rare inherited disorders can be associated with kidney involvement, including glomerulopathies, tubulopathies, multiple cysts, congenital anomalies of the kidneys and urinary tract, urolithiasis, malignant and benign tumors. Genetic nephropathy should be always considered in children, adolescents and young patients with the kidneys or urinary tract disorders and/or patients with positive family anamnesis. Extrarenal manifestations can be a valuable clue for diagnosis of certain hereditary diseases, e.g. neurosensory deafness in Alport syndrome or photofobia in nephropathic cystinosis. Diagnosis of monogenic inherited diseases should be verified by genetic testing. Specific drugs are available for treatment of certain hereditary diseases involving kidney, e.g. Fabry disease, cystinosis, primary hyperoxaluria I type and atypical hemolytic uremic syndrome.

Prospective Study on Individualized Dose Adjustment of Tolvaptan Based on Urinary Osmolality in Patients With ADPKD

Introduction

Tolvaptan has been shown to reduce renal volume and delay disease progression in autosomal-dominant polycystic kidney disease (ADPKD). However, no biomarkers are currently available to guide dose adjustment. We aimed to explore the possibility of individualized tolvaptan dose adjustments based on cut-off values for urinary osmolality (OsmU).

Methods

This prospective cohort study included patients with ADPKD, with rapid disease progression. Tolvaptan treatment was initiated at a dose of 45/15 mg and increased based on OsmU, with a limit set at 200 mOsm/kg. Primary renal events (25% decrease in estimated glomerular filtration rate [eGFR] during treatment), within-patient eGFR slope, and side effects were monitored during the 3-year follow-up.

Results

Forty patients participated in the study. OsmU remained below 200 mOsm/kg throughout the study period, and most patients required the minimum tolvaptan dose (mean dose, 64 [±10] mg), with a low discontinuation rate (5%). The mean annual decline in eGFR was -3.05 (±2.41) ml/min per 1.73 m2 during tolvaptan treatment, compared to the period preceding treatment, corresponding to a reduction in eGFR decline of more than 50%. Primary renal events occurred in 20% of patients (mean time to onset, 31 months; 95% confidence interval [CI] = 28-34).

Conclusion

Individualized tolvaptan dose adjustment based on OsmU in patients with ADPKD and rapid disease progression provided benefits in terms of reducing eGFR decline, compared with reference studies, and displayed lower dropout rates and fewer side effects. Further studies are required to confirm optimal strategies for the use of OsmU for tolvaptan dose adjustment in patients with ADPKD.

Dietary Aspects and Drug-Related Side Effects in Autosomal Dominant Polycystic Kidney Disease Progression

Autosomal dominant polycystic kidney disease (ADPKD) is the most commonly inherited kidney disease. In the absence of targeted therapies, it invariably progresses to advanced chronic kidney disease. To date, the only approved treatment is tolvaptan, a vasopressin V2 receptor antagonist that has been demonstrated to reduce cyst growth and attenuate the decline in kidney function. However, it has various side effects, the most frequent of which is aquaresis, leading to a significant discontinuation rate. The strategies proposed to combat aquaresis include the use of thiazides or metformin and a reduction in the dietary osmotic load. Beyond the prescription of tolvaptan, which is limited to those with a rapid and progressive decline in kidney function, dietary interventions have been suggested to protect against disease progression. Moderate sodium restriction, moderate protein intake (up to 0.8 g/kg/day), avoidance of being overweight, and increased water consumption are recommended in ADPKD guidelines, though all with low-grade evidence. The aim of the present review is to critically summarize the evidence on the effect of dietary modification on ADPKD and to offer some strategies to mitigate the adverse aquaretic effects of tolvaptan.