Is the light at the end of the tunnel nigh? A review of ADPKD focusing on the burden of disease and tolvaptan as a new treatment

Novel Approaches in Chronic Renal Failure without Renal Replacement Therapy: A Review

Chronic kidney disease (CKD) is characterized by renal parenchymal damage leading to a reduction in the glomerular filtration rate. The inflammatory response plays a pivotal role in the tissue damage contributing to renal failure. Current therapeutic options encompass dietary control, mineral salt regulation, and management of blood pressure, blood glucose, and fatty acid levels. However, they do not effectively halt the progression of renal damage. This review critically examines novel therapeutic avenues aimed at ameliorating inflammation, mitigating extracellular matrix accumulation, and fostering renal tissue regeneration in the context of CKD. Understanding the mechanisms sustaining a proinflammatory and profibrotic state may offer the potential for targeted pharmacological interventions. This, in turn, could pave the way for combination therapies capable of reversing renal damage in CKD. The non-replacement phase of CKD currently faces a dearth of efficacious therapeutic options. Future directions encompass exploring vaptans as diuretics to inhibit water absorption, investigating antifibrotic agents, antioxidants, and exploring regenerative treatment modalities, such as stem cell therapy and novel probiotics. Moreover, this review identifies pharmaceutical agents capable of mitigating renal parenchymal damage attributed to CKD, targeting molecular-level signaling pathways (TGF-β, Smad, and Nrf2) that predominate in the inflammatory processes of renal fibrogenic cells.

Public support for patients with intractable diseases in Japan: impact on clinical indicators from nationwide registries in patients with autosomal dominant polycystic kidney disease

BACKGROUND

Clinical practice guidelines recommend antihypertensive and tolvaptan therapies for patients with autosomal dominant polycystic kidney disease (ADPKD) in Japan. However, tolvaptan therapy may pose an economic burden. The Japanese Ministry of Health, Labour and Welfare supports patients with intractable diseases. This study aimed to confirm the impact of the intractable disease system in Japan on the clinical treatment of ADPKD.

METHODS

We analyzed the data of 3768 patients with ADPKD having a medical subsidy certificate from the Japanese Ministry of Health, Labour and Welfare in 2015-2016. The following quality indicators were use: the adherence rate to the 2014 clinical practice guideline for polycystic kidney disease (prescription rates of antihypertensive agents and tolvaptan in this cohort) and the number of Japanese patients with ADPKD nationwide started on renal replacement therapy in 2014 and 2020.

RESULTS

Compared with new applications from 2015 to 2016, the prescription rates of antihypertensives and tolvaptan for the indicated patients at the 2017 renewal application increased by 2.0% (odds ratio = 1.41, p = 0.008) and 47.4% (odds ratio = 10.1, p > 0.001), respectively. These quality indicators improved with antihypertensive treatment, especially in patients with chronic kidney disease stages 1-2 (odds ratio = 1.79, p = 0.013) and in those aged < 50 years (odds ratio = 1.70, p = 0.003). The number of patients with ADPKD who were started on renal replacement therapy in Japan decreased from 999 in 2014 to 884 in 2020 in the nationwide database (odds ratio = 0.83, p < 0.001).

CONCLUSIONS

The Japanese public intractable disease support system contributes to improvement of ADPKD treatment.

Venglustat, a Novel Glucosylceramide Synthase Inhibitor, in Patients at Risk of Rapidly Progressing ADPKD: Primary Results of a Double-Blind, Placebo-Controlled, Phase 2/3 Randomized Clinical Trial

RATIONALE & OBJECTIVE

Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the formation of multiple kidney cysts that leads to growth in total kidney volume (TKV) and progression to kidney failure. Venglustat is a glucosylceramide synthase inhibitor that has been shown to inhibit cyst growth and reduce kidney failure in preclinical models of ADPKD.

STUDY DESIGN

STAGED-PKD was a 2-stage, multicenter, double-blind, randomized, placebo-controlled phase 2/3 study in adults with ADPKD at risk of rapidly progressive disease, who were selected based on Mayo Clinic imaging classification of ADPKD class 1C, 1D, or 1E and an estimated glomerular filtration rate (eGFR) of 30-89.9mL/min/1.73m².

SETTING & PARTICIPANTS

Enrollment included 236 and 242 patients in stages 1 and 2, respectively.

INTERVENTIONS

In trial stage 1, the patients were randomized 1:1:1 to venglustat, 8mg; venglustat, 15mg; or placebo. In stage 2, the patients were randomized 1:1 to venglustat, 15mg (highest dose identified as safe and well tolerated in stage 1), or placebo.

OUTCOMES

Primary end points were rate of change in TKV over 18 months in stage 1 and eGFR slope over 24 months in stage 2. Secondary end points were eGFR slope over 18 months (stage 1), rate of change in TKV (stage 2), and safety/tolerability, pain, and fatigue (stages 1 and 2).

RESULTS

A prespecified interim futility analysis showed that venglustat treatment had no effect on the annualized rate of change in TKV over 18 months (stage 1) and had a faster rate of decline in eGFR slope over 24 months (stage 2). Due to this lack of efficacy, the study was terminated early.

LIMITATIONS

The short follow-up period after the end of treatment and limited generalizability of the findings.

CONCLUSIONS

In patients with rapidly progressing ADPKD, treatment with venglustat at either 8mg or 15mg showed no change in the rate of change in TKV and a faster rate of eGFR decline in STAGED-PKD despite a dose-dependent decrease in plasma glucosylceramide levels.

FUNDING

This study was funded by Sanofi.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT03523728.

Caregiver Burden of Autosomal Dominant Polycystic Kidney Disease: A Qualitative Study

Rationale & Objective

There is limited published research on how autosomal dominant polycystic kidney disease (ADPKD) impacts caregivers. This study explored how caregivers of individuals with ADPKD perceive the burdens placed on them by the disease.

Study Design

Qualitative study consisting of focus groups and interviews. Discussions were conducted by trained interviewers using semi-structured interview guides.

Setting & Participants

The research was conducted in 14 countries in North America, South America, Asia, Australia, and Europe. Eligible participants were greater than or equal to 18 years old and caring for a child or adult diagnosed with ADPKD.

Analytical Approach

The concepts reported were coded using qualitative research software. Data saturation was reached when subsequent discussions introduced no new key concepts.

Results

Focus groups and interviews were held with 139 participants (mean age, 44.9 years; 66.9% female), including 25 participants who had a diagnosis of ADPKD themselves. Caregivers reported significant impact on their emotional (74.1%) and social life (38.1%), lost work productivity (26.6%), and reduced sleep (25.2%). Caregivers also reported worry about their financial situation (23.7%). In general, similar frequencies of impact were reported among caregivers with ADPKD versus caregivers without ADPKD, with the exception of sleep (8.0% vs 28.9%, respectively), leisure activities (28.0% vs 40.4% respectively), and work/employment (12.0% vs 29.8%, respectively).

Limitations

The study was observational and designed to elicit concepts, and only descriptive analyses were conducted.

Conclusions

These findings highlight the unique burden on caregivers in ADPKD, which results in substantial emotional, social, and professional/financial impact.

The STAGED-PKD 2-Stage Adaptive Study With a Patient Enrichment Strategy and Treatment Effect Modeling for Improved Study Design Efficiency in Patients With ADPKD

Rationale & Objective

Venglustat, a glucosylceramide synthase inhibitor, inhibits cyst growth and reduces kidney failure in mouse models of autosomal dominant polycystic kidney disease (ADPKD). STAGED-PKD aims to determine the safety and efficacy of venglustat and was designed using patient enrichment for progression to end-stage kidney disease and modeling from prior ADPKD trials.

Study Design

STAGED-PKD is a 2-stage, international, double-blind, randomized, placebo-controlled trial in adults with ADPKD (Mayo Class 1C-1E) and estimated glomerular filtration rate (eGFR) 45-<90 mL/min/1.73 m² at risk of rapidly progressive disease. Enrichment for rapidly progressing patients was identified based on retrospective analysis of total kidney volume (TKV) and eGFR slope from the combined Consortium for Radiologic Imaging Studies of Polycystic Kidney Disease and HALT Progression of Polycystic Kidney Disease A studies.

Setting & Participants

Target enrollment in stages 1 and 2 was 240 and 320 patients, respectively.

Interventions

Stage 1 randomizes patients 1:1:1 to venglustat 8 mg or 15 mg once daily or placebo. Stage 2 randomizes patients 1:1 to placebo or venglustat, with the preferred dose based on stage 1 safety data.

Outcomes

Primary endpoints are TKV growth rate over 18 months in stage 1 and eGFR slope over 24 months in stage 2. Secondary endpoints include: annualized rate of change in eGFR from baseline to 18 months (stage 1); annualized rate of change in TKV based on magnetic resonance imaging from baseline to 18 months (stage 2); and safety, tolerability, pain, and fatigue (stages 1 and 2).

Limitations

If stage 1 is unsuccessful, patients enrolled in the trial may develop drug-related adverse events that can have long-lasting effects.

Conclusions

Modeling allows the design and powering of a 2-stage combined study to assess venglustat’s impact on TKV growth and eGFR slope. Stage 1 TKV assessment via a nested approach allows early evaluation of efficacy and increased efficiency of the trial design by reducing patient numbers and trial duration.

Funding

This study was funded by Sanofi.

Trial registration

STAGED-PKD has been registered at ClinicalTrials.gov with study number NCT03523728.

NS398 as a potential drug for autosomal-dominant polycystic kidney disease: Analysis using bioinformatics, and zebrafish and mouse models

Autosomal‐dominant polycystic kidney disease (ADPKD) is characterized by uncontrolled renal cyst formation, and few treatment options are available. There are many parallels between ADPKD and clear‐cell renal cell carcinoma (ccRCC); however, few studies have addressed the mechanisms linking them. In this study, we aimed to investigate their convergences and divergences based on bioinformatics and explore the potential of compounds commonly used in cancer research to be repurposed for ADPKD. We analysed gene expression datasets of ADPKD and ccRCC to identify the common and disease‐specific differentially expressed genes (DEGs). We then mapped them to the Connectivity Map database to identify small molecular compounds with therapeutic potential. A total of 117 significant DEGs were identified, and enrichment analyses results revealed that they are mainly enriched in arachidonic acid metabolism, p53 signalling pathway and metabolic pathways. In addition, 127 ccRCC‐specific up‐regulated genes were identified as related to the survival of patients with cancer. We focused on the compound NS398 as it targeted DEGs and found that it inhibited the proliferation of Pkd1^−/− and 786‐0 cells. Furthermore, its administration curbed cystogenesis in Pkd2 zebrafish and early‐onset Pkd1‐deficient mouse models. In conclusion, NS398 is a potential therapeutic agent for ADPKD.

Disconnect in Assessments of Autosomal Dominant Polycystic Kidney Disease Burden Between Patients and Physicians: A Survey Study

Background

Autosomal dominant polycystic kidney disease (ADPKD) is a rare inherited kidney disorder with considerable symptom burden and negative effects even in early-stage disease. Patients' reporting of ADPKD symptom burden may differ from physicians' impressions. In this quantitative, cross-section survey study, we evaluated patient and physician assessments of symptom burden at early- and late-stage ADPKD.

Methods

In the United States, 300 patients with ADPKD and 155 physicians treating patients with ADPKD completed online surveys administered by Kantar. Disease stage was categorized as early (chronic kidney disease [CKD] stages 1-3) or late (stages 4-5). Patients completed the Work Productivity and Activity Impairment Questionnaire and reported current disease symptoms. Patients and physicians assessed impacts of ADPKD on daily life and burden of specific symptoms. Statistical analyses compared patient versus physician responses stratified by early- versus late-stage ADPKD.

Results

We found that impairment in work productivity was statistically greater in late- versus early-stage CKD. Compared with physicians' impressions, patients were more likely at early stages and less likely at later stages to report a moderate/strong impact of ADPKD on daily life. Among patients, 74% with early- and 88% with late-stage disease reported that ADPKD caused them to modify their daily lives. In early-stage disease, patients reported a statistically greater burden from feeling exhausted and less burden from dull kidney pain, cardiovascular problems, high blood pressure, and liver cysts than physicians assumed. At later stages, patients reported feeling exhausted and skeletal/joint pain as more burdensome, and frequent urination, high blood pressure, liver cysts, and hematuria as less burdensome, compared with physicians' impressions.

Conclusion

The results of this survey study demonstrate a disconnect between patients' experiences and physicians' awareness of the burden of ADPKD and highlight the need for more patient/physician discussion of symptoms and disease management.

Methylation of the PKD1 Promoter Inversely Correlates with its Expression in Autosomal Dominant Polycystic Kidney Disease

Background

Autosomal dominant polycystic kidney disease (ADPKD), a multisystem disorder, is the most prevalent type of hereditary kidney disease. Here, we aimed to evaluate methylation of the PKD1 gene (PKD1) promoter and its correlation with PKD1 expression in peripheral blood.

Methods

In this case-control study methylation of the PKD1 promoter was evaluated using methylation-sensitive high-resolution melt (MS-HRM) analysis. PKD1 expression was assessed by quantitative real-time PCR. The correlation was evaluated using the Pearson correlation test.

Results

Twenty subjects from both the patient and control groups (n= 40 for each) were methylated at the PKD1 promoter to various levels (18.9% in patients and 62.5% in controls). This difference was statistically significant (p< 0.0001). PKD1 expression in blood samples was significantly greater in ADPKD patients than in controls (p= 0.0081). Significant correlation was seen between PKD1 expression and its promoter methylation status in peripheral blood (r case= -0.5300, p= 0.0162, and r control = -0.6265, p= 0.0031).

Conclusion

Methylation of the PKD1 promoter in ADPKD patients was inversely correlated with PKD1 expression.

Cardiovascular Risk and Quality of Life in Autosomal Dominant Polycystic Kidney Disease Patients on Therapy With Tolvaptan: A Pilot Study

INTRODUCTION

Cardiovascular (CV) complications are the most frequent cause of morbidity and mortality in autosomal dominant polycystic kidney disease (ADPKD) patients. In 2017, the Italian Medicines Agency authorised tolvaptan, a vasopressin V2 receptor antagonist, for the treatment of ADPKD, based on the Tolvaptan Phase 3 Efficacy and Safety Study in ADPKD (TEMPO 3: 4), TEMPO 4: 4 and Replicating Evidence of Preserved Renal Function: An Investigation of Tolvaptan Safety and Efficacy (REPRISE) studies.

AIM OF THE STUDY

The aim of the study was to assess the impact of tolvaptan on CV risk and quality of life, evaluated by nutritional, inflammatory, metabolic, instrumental parameters and psychocognitive tests on ADPKD patients.

METHODS AND MATERIALS

We evaluated 36 patients with ADPKD; 10 patients (7 males, mean age 42.5±7.0 years) treated with tolvaptan and 26 controls (11 males, mean age 36.7±9.1 years). They underwent, at T0, monthly, and at T1 (1 year) clinical, laboratory and instrumental evaluation, in addition to psychocognitive tests.

RESULTS

In ADPKD patients treated with tolvaptan, we found at T1, a decrease in carotid intima-- media thickness (p=0.048), epicardial adipose tissue thickness (p=0.002), C-reactive protein (p=0.026), sympathovagal balance during night (p=0.045) and increased flow-mediated dilation (p=0.023) with a reduction in depression (Hamilton and Beck tests, p=0.008 and p=0.002, respectively) compared with controls.

CONCLUSION

These preliminary results suggest that treatment with tolvaptan could improve early atherosclerosis and endothelial dysfunction markers and improve mood in ADPKD patients (probably by acting on endothelial cell and adipocyte V2 receptors).

Rationale and study protocol of ACQUIRE, a prospective, observational study measuring quality of life, treatment preference and treatment satisfaction of autosomal dominant polycystic kidney disease (ADPKD) patients in Europe

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is considered the most common inherited renal disease. Patient-Reported Outcomes (PROs) and patient experience in ADPKD are difficult to quantify and have not been well studied, particularly in the early stages of the disease. There is evidence to suggest that early-stage ADPKD patients have a lower Health-Related Quality of Life (HRQoL) than the general population due to the signs and symptoms of early-stage ADPKD. However, no research has been carried out on the HRQoL of early-stage ADPKD patients using validated ADPKD-specific PRO measures. Additionally, a new disease progression delaying treatment option has recently emerged for ADPKD. Patient preference for this treatment and unmet treatment needs have not yet been investigated.

METHODS

The ACQUIRE study is a prospective, observational study investigating the influence of early-stage ADPKD-related symptoms and treatments on PROs. It aims to collect real-world data on patient demographics, treatment patterns, clinical outcomes, and PROs such as HRQoL, treatment satisfaction and treatment preference in early-stage ADPKD. Adult ADPKD patients in stages 1-3 of chronic kidney disease (CKD) with evidence of rapidly progressing disease are being recruited from seven European countries. At baseline and every 3 months, for a follow-up period of 18 months, general and disease-specific questionnaires are completed remotely to capture patients' own assessment of their overall and ADPKD-related HRQoL. A Discrete Choice Experiment (DCE) is also used to investigate the value patients place on different attributes of hypothetical treatment options (e.g. treatment outcomes, side effects) and the role each attribute plays in determining overall patient treatment preference.

DISCUSSION

The results of this study will highlight the real-world effects of ADPKD-related challenges on PROs including HRQoL, treatment experience and satisfaction; and help physicians gain greater insight into likely disease outcomes based on early-stage patient symptoms and patients' experience with treatment. Data captured by the DCE may inform ADPKD treatment decision-making from a patient perspective. The DCE will also provide insights into which patients are more likely to perceive benefit from treatments based on the value and trade-offs they place on specific treatment attributes.

TRIAL REGISTRATION

NCT02848521 . Protocol Number/Version: 156-303-00096/Final.

Core Outcome Domains for Trials in Autosomal Dominant Polycystic Kidney Disease: An International Delphi Survey

RATIONALE & OBJECTIVE

Outcomes reported in trials involving patients with autosomal dominant polycystic kidney disease (ADPKD) are heterogeneous and rarely include patient-reported outcomes. We aimed to identify critically important consensus-based core outcome domains to be reported in trials in ADPKD.

STUDY DESIGN

An international 2-round online Delphi survey was conducted in English, French, and Korean languages.

SETTING & PARTICIPANTS

Patients/caregivers and health professionals completed a 9-point Likert scale (7-9 indicating critical importance) and a Best-Worst Scale.

ANALYTICAL APPROACH

The absolute and relative importance of outcomes were assessed. Comments were analyzed thematically.

RESULTS

1,014 participants (603 [60%] patients/caregivers, 411 [40%] health professionals) from 56 countries completed round 1, and 713 (70%) completed round 2. The prioritized outcomes were kidney function (importance score, 8.6), end-stage kidney disease (8.6), death (7.9), blood pressure (7.9), kidney cyst size/growth (7.8), and cerebral aneurysm (7.7). Kidney cyst-related pain was the highest rated patient-reported outcome by both stakeholder groups. Seven themes explained the prioritization of outcomes: protecting life and health, directly encountering life-threatening and debilitating consequences, specificity to ADPKD, optimizing and extending quality of life, hidden suffering, destroying self-confidence, and lost opportunities.

LIMITATIONS

Study design precluded involvement from those without access to internet or limited computer literacy.

CONCLUSIONS

Kidney function, end-stage kidney disease, and death were the most important outcomes to patients, caregivers, and health professionals. Kidney cyst-related pain was the highest rated patient-reported outcome. Consistent reporting of these top prioritized outcomes may strengthen the value of trials in ADPKD for decision making.

The societal economic burden of autosomal dominant polycystic kidney disease in the United States

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited kidney diseases characterized by progressive development of renal cysts and numerous extra-renal manifestations, eventually leading to kidney failure. Given its chronic and progressive nature, ADPKD is expected to carry a substantial economic burden over the course of the disease. However, there is a paucity of evidence on the impact of ADPKD from a societal perspective. This study aimed to estimate the direct and indirect costs associated with ADPKD in the United States (US).

METHODS

A prevalence-based approach using data from scientific literature, and governmental and non-governmental organizations was employed to estimate direct healthcare costs (i.e., medical services, prescription drugs), direct non-healthcare costs (i.e., research and advocacy, donors/recipients matching for kidney transplants, transportation to/from dialysis centers), and indirect costs (i.e., patient productivity loss from unemployment, reduced work productivity, and premature mortality, caregivers' productivity loss and healthcare costs). The incremental costs associated with ADPKD were calculated as the difference between costs incurred over a one-year period by individuals with ADPKD and the US population. Sensitivity analyses using different sources and assumptions were performed to assess robustness of estimates and account for variability in published estimates.

RESULTS

The estimated total annual costs attributed to ADPKD in 2018 ranged from $7.3 to $9.6 billion in sensitivity analyses, equivalent to $51,970 to $68,091 per individual with ADPKD. In the base scenario, direct healthcare costs accounted for $5.7 billion (78.6%) of the total $7.3 billion costs, mostly driven by patients requiring renal replacement therapy ($3.2 billion; 43.3%). Indirect costs accounted for $1.4 billion (19.7%), mostly driven by productivity loss due to unemployment ($784 million; 10.7%) and reduced productivity at work ($390 million; 5.3%). Total excess direct non-healthcare costs were estimated at $125 million (1.7%).

CONCLUSIONS

ADPKD carries a considerable economic burden, predominantly attributed to direct healthcare costs, the majority of which are incurred by public and private healthcare payers. Effective and timely interventions to slow down the progression of ADPKD could substantially reduce the economic burden of ADPKD.