Atrasentan and renal events in patients with type 2 diabetes and chronic kidney disease (SONAR): a double-blind, randomised, placebo-controlled trial

Report from the 5th cardiovascular outcome trial (CVOT) summit

The 5th Cardiovascular Outcome Trial (CVOT) Summit was held in Munich on October 24th-25th, 2019. As in previous years, this summit served as a reference meeting for in-depth discussions on the topic of recently completed and presented CVOTs. This year, focus was placed on the CVOTs CAROLINA, CREDENCE, DAPA-HF, REWIND, and PIONEER-6. Trial implications for diabetes management and the impact on new treatment algorithms were highlighted for diabetologists, cardiologists, endocrinologists, nephrologists, and general practitioners. Discussions evolved from CVOTs to additional therapy options for heart failure (ARNI), knowledge gained for the treatment and prevention of heart failure and diabetic kidney disease in populations with and without diabetes, particularly using SGLT-2 inhibitors and GLP-1 receptor agonists. Furthermore, the ever increasing impact of CVOTs and substances tested for primary prevention and primary care was discussed. The 6th Cardiovascular Outcome Trial Summit will be held in Munich on October 29th-30th, 2020 (https://www.cvot.org).

Single Cell Sequencing and Kidney Organoids Generated from Pluripotent Stem Cells

Methods to differentiate human pluripotent stem cells into kidney organoids were first introduced about 5 years ago, and since that time, the field has grown substantially. Protocols are producing increasingly complex three-dimensional structures, have been used to model human kidney disease, and have been adapted for high-throughput screening. Over this same time frame, technologies for massively parallel, single-cell RNA sequencing (scRNA-seq) have matured. Now, both of these powerful approaches are being combined to better understand how kidney organoids can be applied to the understanding of kidney development and disease. There are several reasons why this is a synergistic combination. Kidney organoids are complicated and contain many different cell types of variable maturity. scRNA-seq is an unbiased technology that can comprehensively categorize cell types, making it ideally suited to catalog all cell types present in organoids. These same characteristics also make scRNA-seq a powerful approach for quantitative comparisons between protocols, batches, and pluripotent cell lines as it becomes clear that reproducibility and quality can vary across all three variables. Lineage trajectories can be reconstructed using scRNA-seq data, enabling the rational adjustment of differentiation strategies to promote maturation of desired kidney cell types or inhibit differentiation of undesired off-target cell types. Here, we review the ways that scRNA-seq has been successfully applied in the organoid field and predict future applications for this powerful technique. We also review other developing single-cell technologies and discuss how they may be combined, using "multiomic" approaches, to improve our understanding of kidney organoid differentiation and usefulness in modeling development, disease, and toxicity testing.

Beneficial effect on podocyte number in experimental diabetic nephropathy resulting from combined atrasentan and RAAS inhibition therapy

Podocyte loss and proteinuria are both key features of human diabetic nephropathy (DN). The leptin-deficient BTBR mouse strain with the ob/ob mutation develops progressive weight gain, type 2 diabetes, and diabetic nephropathy that has many features of advanced human DN, including increased mesangial matrix, mesangiolysis, podocyte loss, and proteinuria. Selective antagonism of the endothelin-1 type A receptor (ET_AR) by atrasentan treatment in combination with renin-angiotensin-aldosterone system inhibition with losartan has been shown to have the therapeutic benefit of lowering proteinuria in patients with DN, but the underlying mechanism for this benefit is not well understood. Using a similar therapeutic approach in diabetic BTBR ob/ob mice, this treatment regimen significantly increased glomerular podocyte number compared with diabetic BTBR ob/ob controls and suggested that parietal epithelial cells were a source for podocyte restoration. Atrasentan treatment alone also increased podocyte number but to a lesser degree. Mice treated with atrasentan demonstrated a reduction in proteinuria, matching the functional improvement reported in humans. This is a first demonstration that treatment with the highly selective ET_AR antagonist atrasentan can lead to restoration of the diminished podocyte number characteristic of DN in humans and thereby underlies the reduction in proteinuria in patients with diabetes undergoing similar treatment. The benefit of ET_AR antagonism in DN extended to a decrease in mesangial matrix as measured by a reduction in accumulations of collagen type IV in both the atrasentan and atrasentan + losartan-treated groups compared with untreated controls.

The New Biology of Diabetic Kidney Disease-Mechanisms and Therapeutic Implications

Diabetic kidney disease remains the most common cause of end-stage kidney disease in the world. Despite reductions in incidence rates of myocardial infarction and stroke in people with diabetes over the past 3 decades, the risk of diabetic kidney disease has remained unchanged, and may even be increasing in younger individuals afflicted with this disease. Accordingly, changes in public health policy have to be implemented to address the root causes of diabetic kidney disease, including the rise of obesity and diabetes, in addition to the use of safe and effective pharmacological agents to prevent cardiorenal complications in people with diabetes. The aim of this article is to review the mechanisms of pathogenesis and therapies that are either in clinical practice or that are emerging in clinical development programs for potential use to treat diabetic kidney disease.

Pathophysiologic mechanisms in diabetic kidney disease: A focus on current and future therapeutic targets

Diabetic kidney disease (DKD) is the primary cause of chronic kidney disease around the globe and is one of the main complications in patients with type 1 and 2 diabetes. The standard treatment for DKD is drugs controlling hyperglycemia and high blood pressure. Renin angiotensin aldosterone system blockade and sodium glucose cotransporter 2 (SGLT2) inhibition have yielded promising results in DKD, but many diabetic patients on such treatments nevertheless continue to develop DKD, leading to kidney failure and cardiovascular comorbidities. New therapeutic options are urgently required. We review here the promising therapeutic avenues based on insights into the mechanisms of DKD that have recently emerged, including mineralocorticoid receptor antagonists, SGLT2 inhibitors, glucagon-like peptide-1 receptor agonist, endothelin receptor A inhibition, anti-inflammatory agents, autophagy activators and epigenetic remodelling. The involvement of several molecular mechanisms in DKD pathogenesis, together with the genetic and epigenetic variability of this condition, makes it difficult to target this heterogeneous patient population with a single drug. Personalized medicine, taking into account the genetic and mechanistic variability, may therefore improve renal and cardiovascular protection in diabetic patients with DKD.

The future of diabetic kidney disease management: what to expect from the experimental studies?

Diabetic kidney disease (DKD) is a major cause of end-stage renal disease. Intensive blood glucose and blood pressure control, particularly using inhibitors of the renin-angiotensin system, have long been mainstays of therapy in patients with DKD. Moreover, new anti-hyperglycemic drugs have recently shown renoprotective effects and this represents a major progress in the management of DKD. However, the risk of progression is still substantial and additional drugs are required. Recent preclinical studies have identified novel therapeutic targets that may optimize renoprotection in the near future. Besides strategies aimed to reduce oxidative stress and inflammation in the kidney, novel extra-renal approaches targeting stem cells, extracellular vesicles, and the microbiota are on the horizon with promising preclinical data. Herein, we will review these lines of research and discuss potential clinical applications. Given the poor yield of experimental studies in DKD in the past years, we will also discuss strategies to improve translation of preclinical research to humans.

Glucose and Blood Pressure-Dependent Pathways-The Progression of Diabetic Kidney Disease

The major clinical associations with the progression of diabetic kidney disease (DKD) are glycemic control and systemic hypertension. Recent studies have continued to emphasize vasoactive hormone pathways including aldosterone and endothelin which suggest a key role for vasoconstrictor pathways in promoting renal damage in diabetes. The role of glucose per se remains difficult to define in DKD but appears to involve key intermediates including reactive oxygen species (ROS) and dicarbonyls such as methylglyoxal which activate intracellular pathways to promote fibrosis and inflammation in the kidney. Recent studies have identified a novel molecular interaction between hemodynamic and metabolic pathways which could lead to new treatments for DKD. This should lead to a further improvement in the outlook of DKD building on positive results from RAAS blockade and more recently newer classes of glucose-lowering agents such as SGLT2 inhibitors and GLP1 receptor agonists.

Endothelin Receptor Antagonists: Status Quo and Future Perspectives for Targeted Therapy

The endothelin axis, recognized for its vasoconstrictive action, plays a central role in the pathology of pulmonary arterial hypertension (PAH). Treatment with approved endothelin receptor antagonists (ERAs), such as bosentan, ambrisentan, or macitentan, slow down PAH progression and relieves symptoms. Several findings have indicated that endothelin is further involved in the pathogenesis of certain other diseases, making ERAs potentially beneficial in the treatment of various conditions. In addition to PAH, this review summarizes the use and perspectives of ERAs in cancer, renal disease, fibrotic disorders, systemic scleroderma, vasospasm, and pain management. Bosentan has proven to be effective in systemic sclerosis PAH and in decreasing the development of vasospasm-related digital ulcers. The selective ERA clazosentan has been shown to be effective in preventing cerebral vasospasm and delaying ischemic neurological deficits and new infarcts. Furthermore, in the SONAR (Study Of Diabetic Nephropathy With Atrasentan) trial, the selective ERA atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease. These data suggest atrasentan as a new therapy in the treatment of diabetic nephropathy and possibly other renal diseases. Preclinical studies regarding heart failure, cancer, and fibrotic diseases have demonstrated promising effects, but clinical trials have not yet produced measurable results. Nevertheless, the potential benefits of ERAs may not be fully realized.

EDN1-AS, A Novel Long Non-coding RNA Regulating Endothelin-1 in Human Proximal Tubule Cells

Endothelin-1 (ET-1) is a peptide hormone that functions as a vasoconstrictor in the vasculature, whereas in the collecting duct of the kidney it exerts blood pressure-lowering effects via natriuretic actions. Aberrant ET-1 signaling is associated with several pathological states including hypertension and chronic kidney disease. ET-1 expression is regulated largely through transcriptional control of the gene that encodes ET-1, EDN1. Here we report a long, non-coding RNA (lncRNA) that appears to be antisense to the EDN1 gene, called EDN1-AS. Because EDN1-AS represents a potential novel mechanism to regulate ET-1 expression, we examined the regulation of EDN1-AS expression and action. A putative glucocorticoid receptor response (GR) element upstream of the predicted EDN1-AS transcription start site was identified using the ENCODE database and the UCSC genome browser. Two homozygous deletion clones of the element were generated using CRISPR/Cas9. This deletion resulted in a significant increase in the expression of EDN1-AS, which was associated with increased secretion of ET-1 peptide from HK-2 cells (two-fold increase in KO cells vs. CNTL, n = 7, P < 0.05). Phenotypic characterization of these CRISPR clones revealed a difference in cell growth rates. Using a standard growth assay, we determined that the KO1 clone exhibited a three-fold increase in growth over 8 days compared to control cells (n = 4, P < 0.01) and the KO2 clone exhibited a two-fold increase (n = 4, P < 0.01). These results support a role for EDN1-AS as a novel regulatory mechanism of ET-1 expression and cellular proliferation.

Targeting the progression of chronic kidney disease

Chronic kidney disease (CKD) is a devastating condition that is reaching epidemic levels owing to the increasing prevalence of diabetes mellitus, hypertension and obesity, as well as ageing of the population. Regardless of the underlying aetiology, CKD is slowly progressive and leads to irreversible nephron loss, end-stage renal disease and/or premature death. Factors that contribute to CKD progression include parenchymal cell loss, chronic inflammation, fibrosis and reduced regenerative capacity of the kidney. Current therapies have limited effectiveness and only delay disease progression, underscoring the need to develop novel therapeutic approaches to either stop or reverse progression. Preclinical studies have identified several approaches that reduce fibrosis in experimental models, including targeting cytokines, transcription factors, developmental and signalling pathways and epigenetic modulators, particularly microRNAs. Some of these nephroprotective strategies are now being tested in clinical trials. Lessons learned from the failure of clinical studies of transforming growth factor β1 (TGFβ1) blockade underscore the need for alternative approaches to CKD therapy, as strategies that target a single pathogenic process may result in unexpected negative effects on simultaneously occurring processes. Additional promising avenues include preventing tubular cell injury and anti-fibrotic therapies that target activated myofibroblasts, the main collagen-producing cells.

Unfavorable Reduction in the Ratio of Endothelin B to A Receptors in Experimental 5/6 Nephrectomy and Adenine Models of Chronic Renal Insufficiency

Chronic renal insufficiency (CRI) is characterized by increased endothelin 1 (ET-1) synthesis. We studied rat kidney endothelin receptor A (ETA) and receptor B (ETB) expressions after 12 and 27 weeks of 5/6 nephrectomy, and after 12 weeks of 0.3% adenine diet, representing proteinuric and interstitial inflammation models of CRI, respectively. Uric acid and calcium-phosphate metabolism were modulated after 5/6 nephrectomy, while ETA blocker and calcimimetic were given with adenine. Endothelin receptor mRNA levels were measured using RT-qPCR and protein levels using autoradiography (5/6 nephrectomy) or ELISA (adenine model). Both 12 and 27 weeks after 5/6 nephrectomy, kidney cortex ETA protein was increased by ~60% without changes in ETB protein, and the ETB:ETA ratio was reduced. However, the ETB:ETA mRNA ratio did not change. In the adenine model, kidney ETA protein was reduced by ~70%, while ETB protein was suppressed by ~95%, and the ETB:ETA ratio was reduced by ~85%, both at the protein and mRNA levels. The additional interventions did not influence the observed reductions in the ETB:ETA ratio. To conclude, unfavorable reduction in the ETB:ETA protein ratio was observed in two different models of CRI. Therefore, ETA blockade may be beneficial in a range of diseases that cause impaired kidney function.

Innate immunity in diabetic kidney disease

Increasing evidence suggests that renal inflammation contributes to the pathogenesis and progression of diabetic kidney disease (DKD) and that anti-inflammatory therapies might have renoprotective effects in DKD. Immune cells and resident renal cells that activate innate immunity have critical roles in triggering and sustaining inflammation in this setting. Evidence from clinical and experimental studies suggests that several innate immune pathways have potential roles in the pathogenesis and progression of DKD. Toll-like receptors detect endogenous danger-associated molecular patterns generated during diabetes and induce a sterile tubulointerstitial inflammatory response via the NF-κB signalling pathway. The NLRP3 inflammasome links sensing of metabolic stress in the diabetic kidney to activation of pro-inflammatory cascades via the induction of IL-1β and IL-18. The kallikrein-kinin system promotes inflammatory processes via the generation of bradykinins and the activation of bradykinin receptors, and activation of protease-activated receptors on kidney cells by coagulation enzymes contributes to renal inflammation and fibrosis in DKD. In addition, hyperglycaemia leads to protein glycation and activation of the complement cascade via recognition of glycated proteins by mannan-binding lectin and/or dysfunction of glycated complement regulatory proteins. Data from preclinical studies suggest that targeting these innate immune pathways could lead to novel therapies for DKD.

Study Design of the Phase 3 Sparsentan Versus Irbesartan (DUPLEX) Study in Patients With Focal Segmental Glomerulosclerosis

Introduction

Focal segmental glomerulosclerosis (FSGS), a histologic lesion in the kidney caused by varied pathophysiological processes, leads to end-stage kidney disease in a large proportion of patients. Sparsentan is a first-in-class orally active compound combining endothelin type A (ET_A) receptor blockade with angiotensin II type 1 (AT₁) receptor antagonism in a single molecule. A Randomized, Multicenter, Double-Blind, Parallel, Active-Control Study of the Effects of Sparsentan, a Dual Endothelin Receptor and Angiotensin Receptor Blocker, on Renal Outcomes in Patients With Primary FSGS (DUPLEX) study evaluates the long-term antiproteinuric efficacy, nephroprotective potential, and safety profile of sparsentan compared with an AT₁ receptor blocker alone in patients with FSGS.

Methods

DUPLEX is a multicenter, international, phase 3, randomized, double-blind, active-controlled study of sparsentan in patients with FSGS. Approximately 300 patients aged 8 to 75 years, inclusive (United States), and 18 to 75 years, inclusive (outside United States) will be randomized 1:1 to daily treatment with sparsentan or irbesartan. After renin-angiotensin-aldosterone system inhibitor washout, treatment will be administered for 108 weeks, with the final assessment at week 112, four weeks after withdrawal of study drug.

Results

The primary endpoint will be the slope of estimated glomerular filtration rate from week 6 to week 108. A novel surrogate efficacy endpoint, the proportion of patients achieving urinary protein-to-creatinine (UP/C) ratio of ≤1.5 g/g and >40% reduction from baseline in UP/C (FSGS partial remission endpoint: FPRE), will be evaluated at a planned interim analysis at week 36. Safety and tolerability of sparsentan will also be assessed.

Conclusion

The phase 3 DUPLEX study will characterize the long-term antiproteinuric efficacy and nephroprotective potential of dual ET_A and AT₁ receptor blockade with sparsentan in patients with FSGS.

Circulating Expression Level of LncRNA Malat1 in Diabetic Kidney Disease Patients and Its Clinical Significance

BACKGROUND

Long noncoding RNA MALAT1 is closely related to diabetes and kidney diseases and is expected to be a new target for the diagnosis and treatment of diabetic nephropathy.

OBJECTIVE

This study aimed to explore the circulating expression level and significance of lncRNA Malat1 in patients with type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD).

METHODS

Quantitative real-time PCR (qPCR) was conducted to assess the expression of lncRNA Malat1 in 20 T2DM patients, 27 DKD patients, and 14 healthy controls, and then, the clinical significance was analyzed.

RESULTS

LncRNA MALAT1 expression in peripheral blood mononuclear cells (PBMC) was significantly upregulated in T2DM and DKD groups when compared to control. Pearson's correlation analysis showed correlation of lncRNA MALAT1 levels with ACR, urine β2-microglobulin (β2-MG), urine α1-microglobulin (α1-MG), creatinine (Cr), and glycosylated hemoglobin (HbA1c), while negative with superoxide dismutase (SOD) (r = -0.388, P < 0.05). Binary regression analysis showed that ACR, creatinine, α1-MG, and LncRNA Malat1 were the risk factors for diabetic nephropathy with OR value of 1.166, 1.031, 1.031, and 2.019 (P < 0.05). The area under ROC curve (AUC) of DKD identified by the above indicators was 0.914, 0.643, 0.807, and 0.797, respectively. The AUC of Joint prediction probability of DKD recognition was 0.914, and the sensitivity and specificity of DKD diagnosis were 1.0 and 0.806, respectively. (Take ≥0.251 as the diagnostic cutoff point).

CONCLUSION

LncRNA Malat1 is highly expressed in DKD patients, and the combined detection of ACR, creatinine, α1-MG, and LncRNA Malat1 with diabetes mellitus may be the best way to diagnose diabetic nephropathy.

The Role of Endothelin and Endothelin Antagonists in Chronic Kidney Disease

Background

Endothelins (ET) are a family of peptides that act as potent vasoconstrictors and pro-fibrotic growth factors. ET-1 is integral to renal and cardiovascular pathophysiology and exerts effects via autocrine, paracrine and endocrine signaling pathways tied to regulation of aldosterone, catecholamines, and angiotensin. In the kidney, ET-1 is critical to maintaining renal perfusion and controls glomerular arteriole tone and hemodynamics. It is hypothesized that ET-1 influences the progression of chronic kidney disease (CKD), and the objective of this review is to discuss the pathophysiology, and role of ET and endothelin receptor antagonists (ERAs) in CKD.

Summary

The use of ERAs in hypertensive nephropathy has the potential to decrease proteinuria, and in diabetic nephropathy has the potential to restore glycocalyx thickness, also decreasing proteinuria. Focal segmental glomerular sclerosis has no specific Food and Drug Administration-approved therapy currently, however, ERAs show promise in decreasing proteinuria and slowing tissue damage. ET-1 is a potential biomarker for autosomal dominant polycystic kidney disease progression and so it is thought that ERAs may be of some therapeutic benefit.

Key Messages

Multiple studies have shown the utility of ERAs in CKD. These agents have shown to reduce blood pressure, proteinuria, and arterial stiffness. However, more clinical trials are needed, and the results of active or recently concluded studies are eagerly awaited.

Loss of Histone H3 K79 Methyltransferase Dot1l Facilitates Kidney Fibrosis by Upregulating Endothelin 1 through Histone Deacetylase 2

BACKGROUND

The progression rate of CKD varies substantially among patients. The genetic and epigenetic contributions that modify how individual patients respond to kidney injury are largely unknown. Emerging evidence has suggested that histone H3 K79 methyltransferase Dot1l has an antifibrotic effect by repressing Edn1, which encodes endothelin 1 in the connecting tubule/collecting duct.

METHODS

To determine if deletion of the Dot1l gene is a genetic and epigenetic risk factor through regulating Edn1, we studied four groups of mice: wild-type mice, connecting tubule/collecting duct-specific Dot1l conditional knockout mice (Dot1l^AC ), Dot1l and Edn1 double-knockout mice (DE^AC ), and Edn1 connecting tubule/collecting duct-specific conditional knockout mice (Edn1^AC ), under three experimental conditions (streptozotocin-induced diabetes, during normal aging, and after unilateral ureteral obstruction). We used several approaches (colocalization, glutathione S-transferase pulldown, coimmunoprecipitation, yeast two-hybrid, gel shift, and chromatin immunoprecipitation assays) to identify and confirm interaction of Dot1a (the major Dot1l splicing variant in the mouse kidney) with histone deacetylase 2 (HDAC2), as well as the function of the Dot1a-HDAC2 complex in regulating Edn1 transcription.

RESULTS

In each case, Dot1l^AC mice developed more pronounced kidney fibrosis and kidney malfunction compared with wild-type mice. These Dot1l^AC phenotypes were ameliorated in the double-knockout DE^AC mice. The interaction between Dot1a and HDAC2 prevents the Dot1a-HDAC2 complex from association with DNA, providing a counterbalancing mechanism governing Edn1 transcription by modulating H3 K79 dimethylation and H3 acetylation at the Edn1 promoter.

CONCLUSIONS

Our study confirms Dot1l to be a genetic and epigenetic modifier of kidney fibrosis, reveals a new mechanism regulating Edn1 transcription by Dot1a and HDAC2, and reinforces endothelin 1 as a therapeutic target of kidney fibrosis.

Endothelin: 30 Years From Discovery to Therapy

Discovered in 1987 as a potent endothelial cell-derived vasoconstrictor peptide, endothelin-1 (ET-1), the predominant member of the endothelin peptide family, is now recognized as a multifunctional peptide with cytokine-like activity contributing to almost all aspects of physiology and cell function. More than 30 000 scientific articles on endothelin were published over the past 3 decades, leading to the development and subsequent regulatory approval of a new class of therapeutics-the endothelin receptor antagonists (ERAs). This article reviews the history of the discovery of endothelin and its role in genetics, physiology, and disease. Here, we summarize the main clinical trials using ERAs and discuss the role of endothelin in cardiovascular diseases such as arterial hypertension, preecclampsia, coronary atherosclerosis, myocardial infarction in the absence of obstructive coronary artery disease (MINOCA) caused by spontaneous coronary artery dissection (SCAD), Takotsubo syndrome, and heart failure. We also discuss how endothelins contributes to diabetic kidney disease and focal segmental glomerulosclerosis, pulmonary arterial hypertension, as well as cancer, immune disorders, and allograft rejection (which all involve ET_A autoantibodies), and neurological diseases. The application of ERAs, dual endothelin receptor/angiotensin receptor antagonists (DARAs), selective ET_B agonists, novel biologics such as receptor-targeting antibodies, or immunization against ET_A receptors holds the potential to slow the progression or even reverse chronic noncommunicable diseases. Future clinical studies will show whether targeting endothelin receptors can prevent or reduce disability from disease and improve clinical outcome, quality of life, and survival in patients.

Diabetic kidney diseases revisited: A new perspective for a new era

BACKGROUND

Globally, diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. As the most common microvascular complication of diabetes, DKD is a thorny, clinical problem in terms of its diagnosis and management. Intensive glucose control in DKD could slow down but not significantly halt disease progression. Revisiting the tremendous advances that have occurred in the field would enhance recognition of DKD pathogenesis as well as improve our understanding of translational science in DKD in this new era.

SCOPE OF REVIEW

In this review, we summarize advances in the understanding of the local microenvironmental changes in diabetic kidneys and discuss the involvement of genetic and epigenetic factors in the pathogenesis of DKD. We also review DKD prevalence changes and analyze the challenges in optimizing the diagnostic approaches and management strategies for DKD in the clinic. As we enter the era of 'big data', we also explore the possibility of linking systems biology with translational medicine in DKD in the current healthcare system.

MAJOR CONCLUSION

Newer understanding of the structural changes of diabetic kidneys and mechanisms of DKD pathogenesis, as well as emergent research technologies will shed light on new methods of dealing with the existing clinical challenges of DKD.

Design and optimization strategies for the development of new drugs that treat chronic kidney disease

Introduction: Chronic kidney disease (CKD) is characterized by increased risks of progression to end-stage kidney disease requiring dialysis and cardiovascular mortality, predicted to be among the five top causes of death by 2040. Only the design and optimization of novel strategies to develop new drugs to treat CKD will contain this trend. Current therapy for CKD includes nonspecific therapy targeting proteinuria and/or hypertension and cause-specific therapies for diabetic kidney disease, autosomal dominant polycystic kidney disease, glomerulonephritides, Fabry nephropathy, hemolytic uremic syndrome and others.Areas covered: Herein, the authors review the literature on new drugs under development for CKD as well as novel design and development strategies.Expert opinion: New therapies for CKD have become a healthcare priority. Emerging therapies undergoing clinical trials are testing expanded renin-angiotensin system blockade with double angiotensin receptor/endothelin receptor blockers, SGLT2 inhibition, and targeting inflammation, the immune response, fibrosis and the Nrf2 transcription factor. Emerging therapeutic targets include cell senescence, complement activation, Klotho expression preservation and microbiota. Novel approaches include novel model systems that can be personalized (e.g. organoids), unbiased systems biology-based identification of new therapeutic targets, drug databases that speed up drug identification and repurposing, nanomedicines that improve drug delivery and RNA targeting to expand the number of targetable proteins.

Emerging Drug Classes and Their Potential Use in Hypertension

Despite the availability of multiple antihypertensive drugs targeting the different pathways implicated in its pathophysiology, hypertension remains poorly controlled worldwide, and its prevalence is increasing because of the aging of the population and the obesity epidemic. Although nonadherence to treatment contributes to uncontrolled hypertension, it is likely that not all the pathophysiological mechanisms are neutralized by the various classes of antihypertensive treatment currently available, and, the counter-regulatory mechanisms triggered by these treatments may decrease their blood pressure–lowering effect. The development of new antihypertensive drugs acting on new targets, with different modes of action, therefore, remains essential, to improve blood pressure control and reduce the residual burden of cardiovascular risks further. However, the difficulties encountered in the conception, development, costs, and delivery to the market of new classes of antihypertensive agents highlights the hurdles that must be overcome to release and to evaluate their long-term safety and efficacy for hypertension only, especially because of the market pressure of cheap generic drugs. New chemical entities with blood pressure–lowering efficacy are thus being developed more for heart failure or diabetic kidney disease, 2 diseases pathophysiologically associated with hypertension. These include dual angiotensin II receptor-neprilysin inhibitors, soluble guanylate cyclase stimulators, nonsteroidal dihydropyridine-based mineralocorticoid receptor antagonists, as well as sodium-glucose cotransporter 2 inhibitors. However, centrally acting aminopeptidase A inhibitors and endothelin receptor antagonists have a dedicated program of development for hypertension. All these emergent drug classes and their potential use in hypertension are reviewed here.

Kidney disease trials for the 21st century: innovations in design and conduct

Compared to other specialties, nephrology has reported relatively few clinical trials, and most of these are too small to detect moderate treatment effects. Consequently, interventions that are commonly used by nephrologists have not been adequately tested and some may be ineffective or harmful. More randomized trials are urgently needed to address important clinical questions in patients with kidney disease. The use of robust surrogate markers may accelerate early-phase drug development. However, scientific innovations in trial conduct developed by other specialties should also be adopted to improve trial quality and enable more, larger trials in kidney disease to be completed in the current era of burdensome regulation and escalating research costs. Examples of such innovations include utilizing routinely collected health-care data and disease-specific registries to identify and invite potential trial participants, and for long-term follow-up; use of prescreening to facilitate rapid recruitment of participants; use of pre-randomization run-in periods to improve participant adherence and assess responses to study interventions prior to randomization; and appropriate use of statistics to monitor studies and analyse their results. Nephrology is well positioned to harness such innovations due to its advanced use of electronic health-care records and the development of disease-specific registries. Adopting a population approach and efficient trial conduct along with challenging unscientific regulation may increase the number of definitive clinical trials in nephrology and improve the care of current and future patients.

Renoprotection Provided by Additional Diuretic Treatment in Partially Nephrectomized Ren-2 Transgenic Rats Subjected to the Combined RAS and ETA Blockade

Objective

Our previous study in heterozygous Ren-2 transgenic rats (TGR) demonstrated that long-term treatment with endothelin receptor A (ET_A) blocker atrasentan added to the renin-angiotensin system (RAS) blockade had renoprotective effects in a model of chronic kidney disease (CKD) induced by partial nephrectomy. Since ET_A blockade is known to cause edema, we were interested whether diuretic treatment added to this therapy would be beneficial.

Design and Methods

Partial nephrectomy (NX) was performed at the age of 3 months in TGR rats which were subjected to: (i) RAS blockade alone (angiotensin receptor blocker losartan and angiotensin converting enzyme inhibitor trandolapril), (ii) combined RAS (losartan and trandolapril) and ET_A receptor blockade (atrasentan), or (iii) diuretic (hydrochlorothiazide) added to the combined RAS + ET_A blockade for 50 weeks following NX.

Results

At the end of the study systolic blood pressure and cardiac hypertrophy were similarly decreased in all treated groups. Survival was significantly improved by ET_A receptor blockade added to RAS blockade with no further effects of diuretic treatment. However, additional diuretic treatment combined with RAS + ET_A blockade decreased body weight and had beneficial renoprotective effects - reductions of both kidney weight and kidney damage markers. Proteinuria gradually increased in rats treated with RAS blockade alone, while it was substantially lowered by additional ET_A blockade. In rats treated with additional diuretic, proteinuria was progressively reduced throughout the experiment.

Conclusion

A diuretic added to the combined RAS and ET_A blockade has late renoprotective effects in CKD induced by partial nephrectomy in Ren-2 transgenic rats. The diuretic improved: renal function (evaluated as proteinuria and creatinine clearance), renal morphology (kidney mass, glomerular volume), and histological markers of kidney damage (glomerulosclerosis index, tubulointerstitial injury).

Microalbuminuria and cardiorenal risk: old and new evidence in different populations

Since the association of microalbuminuria (MAU) with cardiovascular (CV) risk was described, a huge number of reports have emerged. MAU is a specific integrated marker of CV risk and targets organ damage in patients with hypertension, chronic kidney disease (CKD), and diabetes and its recognition is important for identifying patients at a high or very high global CV risk. The gold standard for diagnosis is albumin measured in 24-hour urine collection (normal values of less than 30 mg/day, MAU of 30 to 300 mg/day, macroalbuminuria of more than 300 mg/day) or, more practically, the determination of urinary albumin-to-creatinine ratio in a urine morning sample (30 to 300 mg/g). MAU screening is mandatory in individuals at risk of developing or presenting elevated global CV risk. Evidence has shown that intensive treatment could turn MAU into normoalbuminuria. Intensive treatment with the administration of an angiotensin-converting enzyme inhibitor or an angiotensin receptor blocker, in combination with other anti-hypertensive drugs and drugs covering other aspects of CV risk, such as mineralocorticoid receptor antagonists, new anti-diabetic drugs, and statins, can diminish the risk accompanying albuminuria in hypertensive patients with or without CKD and diabetes.

The Signaling of Cellular Senescence in Diabetic Nephropathy

Diabetic nephropathy is the leading cause of chronic kidney disease (CKD) in western countries. Notably, it has a rapidly rising prevalence in China. The patients, commonly complicated with cardiovascular diseases and neurologic disorders, are at high risk to progress into end-stage renal disease (ESRD) and death. However, the pathogenic mechanisms of diabetic nephropathy have not been determined. Cellular senescence, which recently has gained broad attention, is thought to be an important player in the onset and development of diabetic nephropathy. In this issue, we generally review the mechanisms of cellular senescence in diabetic nephropathy, which involve telomere attrition, DNA damage, epigenetic alterations, mitochondrial dysfunction, loss of Klotho, Wnt/β-catenin signaling activation, persistent inflammation, and accumulation of uremic toxins. Moreover, we highlight the potential therapeutic targets of cellular senescence in diabetic nephropathy and provide important clues for clinical strategies.

New Molecules for Treating Resistant Hypertension: a Clinical Perspective

PURPOSE OF REVIEW

To review the findings of trials evaluating pharmacological treatment approaches for hypertension in general, and resistant hypertension (RH) in particular, and propose future research and clinical directions.

RECENT FINDINGS

RH is defined as blood pressure (BP) that remains above target levels despite adherence to at least three antihypertensive medications, including a diuretic. Thus far, clinical trials of pharmacological approaches in RH have focused on older molecules, with spironolactone being demonstrated as the most efficacious fourth-line agent. However, the use of spironolactone in clinical practice is hampered by its side effect profile and the risk of hyperkalaemia in important RH subgroups, such as patients with moderate-severe chronic kidney disease (CKD). Clinical trials of new molecules targeting both well-established and more recently elucidated pathophysiologic mechanisms of hypertension offer a multitude of potential treatment avenues that warrant further evaluation in the context of RH. These include selective mineralocorticoid receptor antagonists (MRAs), aldosterone synthase inhibitors (ASIs), activators of the counterregulatory renin-angiotensin-system (RAS), vaccines, neprilysin inhibitors alone and in combined formulations, natriuretic peptide receptor agonists A (NPRA-A) agonists, vasoactive intestinal peptide (VIP) agonists, centrally acting aminopeptidase A (APA|) inhibitors, antimicrobial suppression of central sympathetic outflow (minocycline), dopamine β-hydroxylase (DβH) inhibitors and Na+/H+ Exchanger 3 (NHE3) inhibitors. There is a paucity of data from trials evaluating newer molecules for the treatment of RH. Emergent novel molecules for non-resistant forms of hypertension heighten the prospects of identifying new, effective and well-tolerated pharmacological approaches to RH. There is a glaring need to undertake RH-focused trials evaluating their efficacy and clinical applicability.

Diabetes news

Martin J. Kurian, Peter J. Rentzepis, Ann M. Carracher, and Kelly L. Close are of Close Concerns (http://www.closeconcerns.com), a healthcare information company focused exclusively on diabetes and obesity care. Close Concerns publishes Closer Look, a periodical that brings together news and insights in these areas. Each month, the Journal of Diabetes includes this News feature, in which Kurian, Rentzepis, Carracher, and Close review the latest developments relevant to researchers and clinicians.

Impact of ET-1 and sex in glomerular hyperfiltration in humanized sickle cell mice

Hyperfiltration, highly prevalent early in sickle cell disease (SCD), is in part driven by an increase in ultrafiltration coefficient (Kf). The increase in Kf may be due to enlarged filtration surface area and/or increased glomerular permeability (Palb). Previous studies have demonstrated that endothelin-1 (ET-1) contributes to Palb changes in models of diabetes and SCD. Thus, we performed longitudinal studies of renal function to determine the relationship between ET-1 and glomerular size and Palb that may contribute to hyperfiltration in humanized sickle cell (HbSS) and control (HbAA) mice at 8-32 weeks of age. HbSS mice were characterized by significant increases in plasma and glomerular ET-1 expression in both sexes although this increase was significantly greater in males. HbSS glomeruli of both males and females presented with a progressive and significant increase in glomerular size, volume, and Kf During the onset of hyperfiltration, plasma and glomerular ET-1 expression were associated with a greater increase in glomerular size and Kf in HbSS mice, regardless of sex. The pattern of Palb augmentation during the hyperfiltration was also associated with an increase in glomerular ET-1 expression, in both male and female HbSS mice. However, the increase in Palb was significantly greater in males and delayed in time in females. Additionally, selective endothelin A receptor (ETA) antagonist prevented hyperfiltration in HbSS, regardless of sex. These results suggest that marked sex disparity in glomerular hyperfiltration may be driven, in part, by ET-1-dependent ultra-structural changes in filtration barrier components contributing to glomerular hyperfiltration in HbSS mice.

Advances in Therapies and Imaging for Systemic Vasculitis

Vasculitis is a systemic disease characterized by immune-mediated injury of blood vessels. Current treatments for vasculitis, such as glucocorticoids and alkylating agents, are associated with significant side effects. Furthermore, the management of both small and large vessel vasculitis is challenging because of a lack of robust markers of disease activity. Recent research has advanced our understanding of the pathogenesis of both small and large vessel vasculitis, and this has led to the development of novel biologic therapies capable of targeting key cytokine and cellular effectors of the inflammatory cascade. In parallel, a diverse range of imaging modalities with the potential to monitor vessel inflammation are emerging. Continued expansion of combined structural and molecular imaging using positron emission tomography with computed tomography or magnetic resonance imaging may soon provide reliable longitudinal tracking of vascular inflammation. In addition, the emergence of radiotracers able to assess macrophage activation and immune checkpoint activity represents an exciting new frontier in imaging vascular inflammation. In the near future, these advances will allow more precise imaging of disease activity enabling clinicians to offer more targeted and individualized patient management.

Diabetic nephropathy: an insight into molecular mechanisms and emerging therapies

Introduction: Diabetic kidney disease (DKD) is a major cause of morbidity and mortality in diabetes and is the most common cause of proteinuric and non-proteinuric forms of end-stage renal disease (ESRD). Control of risk factors such as blood glucose and blood pressure is not always achievable or effective. Significant research efforts have attempted to understand the pathophysiology of DKD and develop new therapies. Areas covered: We review DKD pathophysiology in the context of existing and emerging therapies that affect hemodynamic and metabolic pathways. Renin-angiotensin system (RAS) inhibition has become standard care. Recent evidence for renoprotective activity of SGLT2 inhibitors and GLP-1 agonists is an exciting step forward while endothelin receptor blockade shows promise. Multiple metabolic pathways of DKD have been evaluated with varying success; including mitochondrial function, reactive oxygen species, NADPH oxidase (NOX), transcription factors (NF-B and Nrf2), advanced glycation, protein kinase C (PKC), aldose reductase, JAK-STAT, autophagy, apoptosis-signaling kinase 1 (ASK1), fibrosis and epigenetics. Expert opinion: There have been major advances in the understanding and treatment of DKD. SGLT2i and GLP-1 agonists have demonstrated renoprotection, with novel therapies under evaluation. Addressing the interaction between hemodynamic and metabolic pathways may help achieve prevention, attenuation or even reversal of DKD.

Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation and Study of Diabetic Nephropathy with Atrasentan: what was learned about the treatment of diabetic kidney disease with canagliflozin and atrasentan?

In April 2019, two major Phase 3 randomized clinical trials were published that assessed primary renal outcomes in diabetic kidney disease (DKD) in type 2 diabetes mellitus (T2DM). The Canagliflozin and Renal Events in Diabetes with Established Nephropathy Clinical Evaluation (CREDENCE) tested an already available antidiabetic drug, canagliflozin, and the Study of Diabetic Nephropathy with Atrasentan (SONAR) tested a novel molecule, the endothelin-1 receptor blocker atrasentan, both on top of renin-angiotensin system blockade. Both trials demonstrated significant nephroprotection in patients with overt DKD (albuminuria >300 mg/g urinary creatinine) for combined primary endpoints of end-stage kidney disease (ESKD), doubling of serum creatinine or death from renal or cardiovascular causes in CREDENCE {hazard ratio [HR] 0.70 [95% confidence interval (CI) 0.59-0.82]} and ESKD and doubling of serum creatinine in SONAR [HR 0.65 (95% CI 0.49-0.88)]. Canagliflozin also decreased the secondary renal endpoint ESKD, doubling of serum creatinine or renal death [HR 0.66 (95% CI 0.53-0.81)], which was similar in nature and impact to the primary endpoint in SONAR. In addition, canagliflozin decreased a secondary endpoint of cardiovascular death or hospitalization for heart failure [HR 0.69 (95% CI 0.57-0.83)], whereas atrasentan had no significant impact on a secondary cardiovascular composite endpoint or on hospital admissions for heart failure and, despite restrictive exclusion criteria, there was a non-significant trend towards more frequent episodes of heart failure. Based on these results, canagliflozin will likely be approved for the indication of treating DKD in T2DM and the estimated glomerular filtration rate threshold for prescribing it will be lifted, whereas the future and place of atrasentan in the treatment of DKD remain unclear.