Sparsentan in patients with IgA nephropathy: a prespecified interim analysis from a randomised, double-blind, active-controlled clinical trial

Alternative Complement Pathway Inhibition with Iptacopan in IgA Nephropathy

BACKGROUND

The alternative complement pathway plays a key role in the pathogenesis of IgA nephropathy. Iptacopan specifically binds to factor B and inhibits the alternative pathway.

METHODS

In this phase 3, double-blind, randomized, placebo-controlled trial, we enrolled adults with biopsy-confirmed IgA nephropathy and proteinuria with a 24-hour urinary protein-to-creatinine ratio of 1 or higher (with protein and creatinine both measured in grams) despite optimized supportive therapy. Patients were randomly assigned, in a 1:1 ratio, to receive oral iptacopan (200 mg) or placebo twice daily for 24 months while continuing to receive supportive therapy. The primary objective of this prespecified interim analysis was to assess the efficacy of iptacopan as compared with that of placebo in reducing proteinuria at month 9; the primary end point was the change from baseline in the 24-hour urinary protein-to-creatinine ratio at month 9. The proportion of patients who had a 24-hour urinary protein-to-creatinine ratio of less than 1 at month 9 without receiving rescue or alternative medication or undergoing kidney-replacement therapy (dialysis or transplantation) was a secondary end point. Safety was also assessed. The effect of iptacopan on kidney function will be assessed at the end of the 2-year double-blind treatment period.

RESULTS

The main trial population included 222 patients in the iptacopan group and 221 in the placebo group. The interim efficacy analysis included the first 250 patients who underwent randomization in the main trial population (125 patients in each group) and who remained in the trial until month 9 or discontinued the trial by month 9. Safety was assessed in all the patients in the main trial population. At month 9, the adjusted geometric mean 24-hour urinary protein-to-creatinine ratio was 38.3% (95% confidence interval, 26.0 to 48.6; two-sided P<0.001) lower with iptacopan than with placebo. The reduction in proteinuria was supported by consistent results in secondary end point analyses. There were no unexpected safety findings with iptacopan. The incidence of adverse events that occurred during the treatment period was similar in the two groups; most events were mild to moderate in severity and reversible. No increased risk of infection was observed.

CONCLUSIONS

Among patients with IgA nephropathy, treatment with iptacopan resulted in a significant and clinically meaningful reduction in proteinuria as compared with placebo. (Funded by Novartis; APPLAUSE-IgAN ClinicalTrials.gov number, NCT04578834.).

Atrasentan in Patients with IgA Nephropathy

BACKGROUND

Patients with IgA nephropathy and severe proteinuria have a high lifetime risk of kidney failure. The efficacy and safety of the selective endothelin type A receptor antagonist atrasentan in reducing proteinuria in patients with IgA nephropathy are incompletely understood.

METHODS

We are conducting a phase 3, multinational, double-blind, randomized, controlled trial involving adults with biopsy-proven IgA nephropathy, a total urinary protein excretion of at least 1 g per day, and an estimated glomerular filtration rate of at least 30 ml per minute per 1.73 m2 of body-surface area. Patients were randomly assigned to receive atrasentan (0.75 mg per day) or matched placebo for 132 weeks. The primary outcome, assessed at a prespecified interim analysis of data from the first 270 patients in the main stratum, was the change in the 24-hour urinary protein-to-creatinine ratio from baseline to week 36; the change was estimated with the use of a repeated-measures model. (An exploratory stratum of patients who were receiving a sodium-glucose cotransporter 2 inhibitor were included in a separate analysis.) Safety analyses were based on adverse events across the entire main stratum.

RESULTS

A total of 340 patients were recruited into the main stratum. Among the first 270 patients in the main stratum (135 per trial group) who completed the week 36 visit, the geometric mean percentage change in the urinary protein-to-creatinine ratio relative to baseline was significantly greater with atrasentan (-38.1%) than with placebo (-3.1%), with a geometric mean between-group difference of -36.1 percentage points (95% confidence interval, -44.6 to -26.4; P<0.001). The percentage of patients with adverse events did not differ substantially between the two groups. Fluid retention was reported by 19 of 169 patients (11.2%) in the atrasentan group and in 14 of 170 (8.2%) in the placebo group but did not lead to discontinuation of the trial regimen. No apparent cases of cardiac failure or severe edema occurred.

CONCLUSIONS

In this prespecified interim analysis, atrasentan resulted in a significant and clinically meaningful reduction in proteinuria as compared with placebo in patients with IgA nephropathy. (Funded by Novartis; ALIGN ClinicalTrials.gov number, NCT04573478.).

Selective endothelin A receptor antagonism in chronic kidney disease: improving clinical application

Endothelin-1 (ET-1) is a peptide that is involved in various chronic diseases including cardiovascular and kidney disease. ET-1 can bind to two receptors, endothelin A (ETA) and endothelin B (ETB), which are found in different organs and tissues. When ET-1 binds to the ETA receptor, it causes blood vessels to narrow, while binding of ET-1 to the ETB receptor causes blood vessels to widen. These receptors help regulate fluid and electrolyte balance in the kidneys, as well as the kidney's ability to filter various substances out of the body. Overactivation of ET-1 can occur in people with diabetes or obesity, which can damage the structure and function of the kidney.Studies in mice and humans with kidney disease have shown that blocking the ETA receptor improves kidney health. As a result, medicines that specifically block the ETA receptor, known as endothelin receptor antagonists (ERAs), are a promising option for treating these kidney diseases. The first ERA (sparsentan) is now available for use in patients with immunoglobulin A (IgA) nephropathy, a specific type of kidney disease. It should be noted that ERAs can cause side effects. Fluid retention, which can increase the risk of heart failure, is a side effect that is particularly observed in patients with type 2 diabetes and severe kidney disease. This side effect is less often observed in patients with IgA nephropathy or patients without diabetes.Treatment strategies to optimize safe and effective use of ETA blockers are being developed. Overall, these insights offer hope for better care of patients with kidney disease.

ABSTRACT

Endothelin-1 (ET-1) is a 21-amino acid peptide involved in numerous cardiovascular and renal processes. ET-1 can bind to endothelin receptor A (ETA) and endothelin receptor B (ETB), which are found in various organs and tissues. In general, binding of ET-1 to the ETA receptor causes vasoconstriction, whereas activation of the ETB receptor leads to vasodilation. In the kidney, endothelin receptors regulate fluid and electrolyte balance, regional blood flow and glomerular filtration rate. In pathological conditions, ET-1 promotes kidney injury through adverse effects on the endothelial glycocalyx, podocytes and mesangial cells, and stimulating inflammation and fibrosis in the tubules. In experimental and clinical studies, inhibition of the ETA receptor has been shown beneficial in a variety of kidney diseases. These include diabetic kidney disease, immunoglobulin A nephropathy, focal segmental glomerulosclerosis and Alport syndrome. Accordingly, selective ETA endothelin receptor antagonists (ERA) may prove a viable therapeutic option in these diseases. However, clinical application is challenged by the occurrence of fluid retention which can lead to heart failure, in particular in patients with severe CKD. Concomitant use of sodium-glucose cotransporter 2 inhibitors (SGLT2i) may mitigate these adverse effects through their diuretic actions. The development of highly selective ETA antagonists, such as atrasentan and zibotentan, and the opportunities of combining these with SGLT2i, holds promise to optimize efficacy and safety of ERAs in clinical practice.

Design and baseline characteristics of the Finerenone, in addition to standard of care, on the progression of kidney disease in patients with Non-Diabetic Chronic Kidney Disease (FIND-CKD) randomized trial

BACKGROUND

Finerenone, a non-steroidal mineralocorticoid receptor antagonist, improved kidney and cardiovascular outcomes in patients with chronic kidney disease (CKD) and type 2 diabetes in two phase 3 outcome trials. The Finerenone, in addition to standard of care, on the progression of kidney disease in patients with Non-Diabetic Chronic Kidney Disease (FIND-CKD) study investigates the effect of finerenone in adults with CKD without diabetes.

METHODS

FIND-CKD (NCT05047263 and EU CT 2023-506897-11-00) is a randomized, double-blind, placebo-controlled phase 3 trial in patients with CKD of non-diabetic aetiology. Adults with a urinary albumin:creatinine ratio (UACR) ≥200-≤3500 mg/g and an estimated glomerular filtration rate (eGFR) ≥25-<90 ml/min/1.73 m2 receiving a maximum tolerated dose of a renin-angiotensin system inhibitor were randomized 1:1 to once-daily placebo or finerenone 10 or 20 mg depending on eGFR >60 or <60 ml/min/1.73 m2. The primary efficacy outcome is total eGFR slope, defined as the mean annual rate of change in eGFR from baseline to month 32. Secondary efficacy outcomes include a combined cardiorenal composite outcome comprising time to kidney failure, sustained ≥57% decrease in eGFR, hospitalization for heart failure or cardiovascular death, as well as separate kidney and cardiovascular composite outcomes. Adverse events are recorded to assess tolerability and safety.

RESULTS

Across 24 countries, 3231 patients were screened and 1584 were randomized to study treatment. The most common causes of CKD were chronic glomerulonephritis (57.0%) and hypertensive/ischaemic nephropathy (29.0%). Immunoglobulin A nephropathy was the most common glomerulonephritis (26.3% of the total population). At baseline, mean eGFR and median UACR were 46.7 ml/min/1.73 m2 and 818.9 mg/g, respectively. Diuretics were used by 282 participants (17.8%), statins by 851 (53.7%) and calcium channel blockers by 794 (50.1%). Sodium-glucose co-transporter 2 (SGLT2) inhibitors were used in 16.9% of patients; these individuals had a similar mean eGFR (45.6 versus 46.8 ml/min/1.73 m2) and a slightly higher median UACR (871.9 versus 808.3 mg/g) compared with those not using SGLT2 inhibitors at baseline.

CONCLUSIONS

FIND-CKD is the first phase 3 trial of finerenone in patients with CKD of non-diabetic aetiology.

Treatment of Patients with IgA Nephropathy: A call for a new paradigm

IgA nephropathy (IgAN), the world's most common primary glomerular disease, carries a significant lifetime risk for kidney failure as well as an enormous socioeconomic burden. In the past, studies in patients with IgAN largely focused on optimizing so-called supportive care, i.e. blockade of the renin-angiotensin system (RAS), blood pressure control and lifestyle modifications. The effectiveness of immunosuppressive measures, particularly high-dose corticosteroid therapy, has been reported variably, but there is considerable evidence for an increase in serious adverse effects with such therapies. This disappointing situation has changed dramatically with better understanding of the pathogenesis of IgAN, and with regulatory agencies accepting changes in proteinuria and the eGFR loss or slope over 2-3 years as surrogate outcome markers. A multitude of new therapies are now being evaluated in IgAN, and several drugs, such as sodium-glucose transporter-2 inhibitors, sparsentan (a dual endothelin-1 and angiotensin II receptor blocker), nefecon (a targeted release formulation of budesonide) and iptacopan (a complement factor B inhibitor) have been approved, with more to come in the next few years. In this review, we propose a new treatment paradigm that combines therapies with different mechanisms of action to target the immune components and the chronic kidney disease components of IgAN in parallel to preserve long-term kidney survival.

Chronic kidney disease

Chronic kidney disease (CKD) is defined by persistent abnormalities of kidney function or structure that have consequences for the health. A progressive decline of excretory kidney function has effects on body homeostasis. CKD is tightly associated with accelerated cardiovascular disease and severe infections, and with premature death. Kidney failure without access to kidney replacement therapy is fatal - a reality in many regions of the world. CKD can be the consequence of a single cause, but CKD in adults frequently relates rather to sequential injuries accumulating over the life course or to the presence of concomitant risk factors. The shared pathomechanism of CKD progression is the irreversible loss of kidney cells or nephrons together with haemodynamic and metabolic overload of the remaining nephrons, leading to further loss of kidney cells or nephrons. The management of patients with CKD focuses on early detection and on controlling all modifiable risk factors. This approach includes reducing the overload of the remaining nephrons with inhibitors of the renin-angiotensin system and the sodium-glucose transporter 2, as well as disease-specific drug interventions, if available. Hypertension, anaemia, metabolic acidosis and secondary hyperparathyroidism contribute to cardiovascular morbidity and reduced quality of life, and require diagnosis and treatment.

Lifetime progression of IgA nephropathy: a retrospective cohort study with extended long-term follow-up

BACKGROUND

IgA nephropathy (IgAN) exhibits an unpredictable trajectory, creating difficulties in prognostication, monitoring, treatment, and research planning. This study provides a comprehensive depiction of the progression of kidney function throughout the disease course, from diagnosis to a span of 36 years post-diagnosis.

METHODS

We utilized a cohort of 400 Norwegian IgAN patients, from diagnosis to the occurrence of death, initiation of kidney replacement therapy (KRT), or the latest follow-up. Recorded proteinuria (n = 2676) and creatinine (n = 8738) measurements were retrieved. Patients were divided into subgroups based on their specific estimated glomerular filtration rate (eGFR) slopes.

RESULTS

Median follow-up was 16 years. During this period, 34% of patients either died or initiated KRT. Among patients who reached endpoint, the median duration from diagnosis to the initiation of KRT or death was 8 years. Notably, 34% of the cohort exhibited a stable disease course, characterized by an eGFR decline of less than 20% between two consecutive measurements. Differences in subsequent disease trajectories among two subgroups with similar eGFR levels at diagnosis could not be accounted for by variations in treatment strategies. Among patients with proteinuria < 1 g/24 h in less than half of the measurements, KRT was five times more prevalent compared to those with more than half of the measurements recording proteinuria < 1 g/24 h (p-value = 0.001).

CONCLUSIONS

While a significant proportion of IgAN patients reach kidney failure within their lifetimes, outcomes vary widely. Clinical data at diagnosis offer limited insights into long-term risks. Enhanced risk stratification necessitates data collection at multiple time points.

Systematic review of the application of the Kidney Failure Risk Equation and Oxford classification in estimating prognosis in IgA Nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common primary glomerulonephritis in the world and is an important cause of chronic kidney disease (CKD) and kidney failure. Outcomes are heterogeneous, and accurate risk stratification is important to identify the highest risk individuals for treatment and to help prevent disease progression. The Oxford classification (OC) is an internationally adopted standard for renal biopsy reporting in IgAN, which measures the degree of histological abnormalities and predicts prognosis. The kidney failure risk equation (KFRE) was developed to predict kidney failure in all causes of CKD and has been shown to be highly accurate across diverse etiologies. This review aimed to compare the KFRE with formulae incorporating the OC in accurately determining the risk of kidney failure in IgAN.

METHODS

A systematic review was conducted in accordance with the Cochrane library guidelines and PRISMA statement for reporting of systematic reviews. Studies comparing the accuracy of the KFRE with the OC in predicting disease progression and kidney failure in IgAN were evaluated. The search strategy and analysis were performed independently by two reviewers. Studies that were eligible for inclusion compared the KFRE with any tool incorporating the OC in a cohort of individuals with IgAN. Eligible outcomes were reduction of estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD), and prognostic tools were required to assess the accuracy of these formulae by discrimination and/or calibration.

RESULTS

After searching several databases, only one study was eligible for inclusion in the review. This study of 2300 Chinese individuals with IgAN had a median follow-up of 2.5 years. Two-hundred eighty-eight individuals had a composite outcome of 50% decline in eGFR or ESRD, and 214 individuals developed ESRD. Both the KFRE and the IgAN Risk Prediction (IRP) tool (incorporating the OC) were highly accurate at predicting ESRD with a C-statistic of 0.90 and 0.91, respectively. Subgroup analysis demonstrated improved performance of IRP over KFRE in discrimination for individuals with preserved eGFR (> 60 ml/min/1.73 m2) at baseline. The risk of bias was high due to insufficient follow-up and handling of missing data, so overall confidence in findings is very low.

CONCLUSION

There is currently insufficient evidence to compare the accuracy of the KFRE and OC in determining outcomes in IgAN. Further research is required in this field.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022364569.

ALIGNing the treatment of IgA nephropathy: Reducing proteinuria with endothelin A receptor inhibition

The ALIGN trial1 demonstrates that atrasentan, an endothelin A (ETA) receptor antagonist, reduces proteinuria in patients with IgA nephropathy (IgAN), a key goal to slow progressive renal disease. These results are consistent with those from sparsentan,2,3 a combined ETA and angiotensin inhibitor, in IgAN, suggesting two-year data will show atrasentan improves renal outcomes.

Semaglutide in patients with overweight or obesity and chronic kidney disease without diabetes: a randomized double-blind placebo-controlled clinical trial

Semaglutide reduces albuminuria and the risk of kidney disease progression in patients with type 2 diabetes and chronic kidney disease (CKD). We conducted a randomized placebo-controlled double-blind clinical trial in adults with CKD (estimated glomerular filtration rate (eGFR) ≥25 ml min-1 1.73 m-2 and urine albumin-to-creatinine ratio (UACR) ≥30 and <3,500 mg g-1) and body mass index ≥27 kg m-2. Participants were randomized to semaglutide 2.4 mg per week or placebo. The primary endpoint was percentage change from baseline in UACR at week 24. Safety was monitored throughout. Overall, 125 participants were screened, of whom 101 were randomized to semaglutide (n = 51) or placebo (n = 50). Mean age was 55.8 (s.d. 12) years; 40 participants (39.6%) were female; median UACR was 251 mg g-1 (interquartile range 100, 584); mean eGFR was 65.0 (s.d. 25) ml min-1 1.73 m-2; and mean body mass index was 36.2 (s.d. 5.6) kg m-2. Chronic glomerulonephritis (n = 25) and hypertensive CKD (n = 27) were the most common CKD etiologies. Treatment for 24 weeks with semaglutide compared to placebo reduced UACR by -52.1% (95% confidence interval -65.5, -33.4; P < 0.0001). Gastrointestinal adverse events were more often reported with semaglutide (n = 30) than with placebo (n = 15). Semaglutide treatment for 24 weeks resulted in a clinically meaningful reduction in albuminuria in patients with overweight/obesity and non-diabetic CKD. ClinicalTrials.gov registration: NCT04889183 .

Study Design and Baseline Characteristics of ALIGN, a Randomized Controlled Study of Atrasentan in Patients With IgA Nephropathy

Introduction

Endothelin A (ETA) receptor activation is a driver of proteinuria, kidney inflammation, and fibrosis in IgA nephropathy (IgAN). Atrasentan, a selective ETA receptor antagonist, has potential to reduce proteinuria and preserve kidney function in IgAN. ALIGN (NCT04573478) is a phase 3, randomized, double-blind, placebo-controlled clinical trial of atrasentan in patients with IgAN at high risk of kidney function loss.

Methods

Eligibility criteria for the ALIGN main stratum included patients with biopsy-proven IgAN, total protein excretion ≥ 1 g/d, estimated glomerular filtration rate (eGFR) ≥ 30 ml/min per 1.73 m2, receiving a maximally tolerated stable dose of a renin-angiotensin system (RAS) inhibitor. An exploratory stratum enrolled participants also receiving a stable dose of sodium glucose cotransporter-2 inhibitors (SGLT2i). Participants were randomized to 0.75 mg atrasentan or placebo orally daily for 132 weeks followed by a 4-week wash-out period. The primary outcome is proteinuria change from baseline (24-hour urine protein-to-creatinine ratio [UPCR]) to week 36 in the main stratum. Key secondary end points include eGFR change from baseline to week 136, safety, and tolerability.

Results

Enrolment occurred across 20 countries; 404 patients were randomized: 340 in the main stratum and 64 in the SGLT2i stratum. At baseline in the main stratum, mean age was 44.7 years, 42.4% were female, mean eGFR and median UPCR were 58.9 ml/min per 1.73 m2 and 1.4 g/g, respectively.

Conclusion

The ongoing ALIGN trial evaluates the efficacy and safety of atrasentan in a representative global IgAN population at risk for disease progression despite optimized RAS inhibitor therapy and includes an exploratory stratum evaluating atrasentan use in combination with an SGLT2i.

The pathogenesis of IgA nephropathy and implications for treatment

IgA nephropathy (IgAN) is a common form of primary glomerulonephritis and represents an important cause of chronic kidney disease globally, with observational studies indicating that most patients are at risk of developing kidney failure within their lifetime. Several research advances have provided insights into the underlying disease pathogenesis, framed by a multi-hit model whereby an increase in circulating IgA1 that lacks galactose from its hinge region - probably derived from the mucosal immune system - is followed by binding of specific IgG and IgA antibodies, generating immune complexes that deposit within the glomeruli, which triggers inflammation, complement activation and kidney damage. Although treatment options are currently limited, new therapies are rapidly emerging that target different pathways, cells and mediators involved in the disease pathogenesis, including B cell priming in the gut mucosa, the cytokines APRIL and BAFF, plasma cells, complement activation and endothelin pathway activation. As more treatments become available, there is a realistic possibility of transforming the long-term outlook for many individuals with IgAN.

First real-world evidence of sparsentan efficacy in patients with IgA nephropathy treated with SGLT2 inhibitors

Background

Sparsentan, a dual-acting antagonist for both the angiotensin II receptor type 1 and the endothelin receptor type A, has emerged as a promising therapeutic agent for the treatment of IgA nephropathy (IgAN). Following the publication of the PROTECT trial, sparsentan recently received approval for the treatment of IgAN in Europe. However, it remains uncertain whether an additive effect can be observed in the context of existing treatment with sodium-glucose co-transporter 2 (SGLT2) inhibitors, given that the PROTECT study did not investigate this dual therapy approach.

Methods

A total of 23 patients with IgAN were treated with sparsentan via the Managed Access Programme between December 2023 and August 2024. The patients were stable on maximum tolerated doses of renin-angiotensin system (RAS) and SGLT2 inhibitors, with an estimated glomerular filtration rate (eGFR) >30 mL/min/1.73 m² and a urine protein/creatinine ratio (UPCR) >0.75 g/g.

Results

In the 23 patients, median (IQR) baseline eGFR (CKD-EPI) was 42 mL/min/1.73 m2 (32-63) and median baseline UPCR was 1.5 g/g (0.9-1.8). After initiation of sparsentan, UPCR significantly decreased (P < 0.0001) to a median of 0.85 g/g (0.42-1.15) in the 2-week follow-up and further declined (P = 0.001) to a median of 0.60 g/g (0.32-0.82) after 14 weeks, equivalent to a relative reduction in proteinuria up to 62% (45-74). A similar significant reduction was observed for the urine albumin/creatinine ratio. No drug-related serious adverse events were reported.

Conclusions

In this real-world setting, sparsentan shows a significant impact on proteinuria, leading to a relative reduction of 62% in UPCR after 14 weeks and beyond, even in patients already receiving SGLT2 inhibitors.

Vascular injury in glomerulopathies: the role of the endothelium

In glomerulopathies, endothelial dysfunction and the presence of histological vascular lesions such as thrombotic microangiopathy, arteriolar hyalinosis, and arteriosclerosis are related to a severe clinical course and worse renal prognosis. The endothelial cell, which naturally has anti-inflammatory and anti-thrombotic regulatory mechanisms, is particularly susceptible to damage caused by various etiologies and can become dysfunctional due to direct/indirect injury or a deficiency of protective factors. In addition, endothelial regulation and protection involve participation of the complement system, factors related to angiogenesis, the renin-angiotensin system (RAS), endothelin, the glycocalyx, the coagulation cascade, interaction between these pathways, interactions between glomerular structures (the endothelium, mesangium, podocyte, and basement membrane) and interstitial structures (tubules, arterioles and small vessels). Dysregulation of those components is also associated with the progression of renal fibrosis, since endothelial cell damage promotes endothelial-to-mesenchymal transition. Although the potential mechanisms of vascular injury have been widely described in diabetic kidney disease, hypertensive nephrosclerosis, and hemolytic uremic syndrome, they require further elucidation in other glomerulopathies. A better understanding of the pathogenesis of vascular injury in patients with glomerular diseases could contribute to the development of specific treatments for such injury.

Sex differences in response to the endothelin receptor antagonist atrasentan in individuals with type 2 diabetes and chronic kidney disease: a post hoc analysis of the SONAR trial

AIMS/HYPOTHESIS

In the Study Of diabetic Nephropathy with AtRasentan (SONAR), the endothelin receptor antagonist (ERA) atrasentan slowed progression of chronic kidney disease (CKD) in individuals with type 2 diabetes. Pre-clinical research suggests sex-based differences in the endothelin system might influence the efficacy and safety of atrasentan. We therefore assessed the effects of atrasentan in men and women participating in SONAR.

METHODS

SONAR was a double-blind, placebo-controlled trial that compared atrasentan 0.75 mg/day with placebo in individuals with type 2 diabetes and CKD (eGFR 25-75 ml/min per 1.73 m2, urine albumin/creatinine ratio [UACR] 300-5000 mg/g). The primary endpoint was defined as the time from randomisation to the first occurrence of a doubling in serum creatinine or kidney failure (eGFR <15 ml/min per 1.73 m2, chronic dialysis, kidney transplantation or death from kidney failure). Hospitalisation for heart failure was the secondary endpoint. We performed Cox proportional hazards regression analyses to compare the treatment effect of atrasentan between male and female participants on the risk of the composite kidney outcome as well as hospitalisation for heart failure. Additionally, differences between male and female participants in atrasentan plasma exposure and eGFR change were assessed using, respectively, a t test and linear mixed effect model.

RESULTS

Among 3668 randomised participants, 946 (25.8%) were female. Atrasentan significantly reduced the risk of the composite kidney outcome in female participants (HR 0.46 [95% CI 0.28, 0.76]) but not in male participants (HR 0.83 [95% CI 0.65, 1.05]; p value for interaction 0.032). Atrasentan compared with placebo reduced eGFR decline to a greater extent in female than in male participants (treatment effect difference between male vs female participants -0.99 ml/min per 1.73 m2, p value for interaction=0.020). The RR for hospitalisation for heart failure with atrasentan vs placebo was 1.14 (95% CI 0.74, 1.76) in male participants and 1.88 (95% CI 0.98, 3.63) in female participants (p value for interaction=0.217). Female participants also had significantly higher atrasentan plasma exposure than male participants (geometric mean AUC 54.5 vs 42.6 ng/ml×h; p<0.001).

CONCLUSIONS/INTERPRETATION

Atrasentan showed greater kidney protection in female than in male participants but also induced more heart failure events in the female participants. These data suggest that sex-specific dosing regimens may be considered to optimise ERA treatment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01858532.

Endothelin receptor antagonists in chronic kidney disease

Endothelin-1 is a potent vasoconstrictor that has diverse physiological functions in the kidney, including in the regulation of blood flow and glomerular filtration, electrolyte homeostasis and endothelial function. Overexpression of endothelin-1 contributes to the pathophysiology of both diabetic and non-diabetic chronic kidney disease (CKD). Selective endothelin receptor antagonists (ERAs) that target the endothelin A (ETA) receptor have demonstrated benefits in animal models of kidney disease and in clinical trials. In patients with type 2 diabetes and CKD, the selective ETA ERA, atrasentan, reduced albuminuria and kidney function decline. Concerns about the increased risks of fluid retention and heart failure with ERA use have led to the design of further trials to optimize dosing and patient selection. More recent studies have shown that the dual ETA receptor and angiotensin receptor blocker, sparsentan, preserved kidney function with minimal fluid retention in patients with IgA nephropathy. Moreover, combined administration of a low dose of the ETA-selective ERA, zibotentan, with the sodium-glucose cotransporter 2 (SGLT2) inhibitor, dapagliflozin, enhanced albuminuria reduction and mitigated fluid retention in patients with CKD. Notably, sparsentan and aprocitentan have received FDA approval for the treatment of IgA nephropathy and treatment-resistant hypertension, respectively. This Review describes our current understanding of the use of ERAs in patients with CKD to guide their optimal safe and effective use in clinical practice.

Baseline, Early Changes, and Residual Albuminuria: Post Hoc Analysis of a Randomized Clinical Trial of Dapagliflozin in Chronic Kidney Disease

Key Points

Dapagliflozin reduced albuminuria in participants with CKD, with reductions being proportional to reductions in the risk of disease progression. Residual albuminuria (at month 4) was linked to higher risks of primary and kidney end points, with no heterogeneity by diabetes status or allocated treatment. Participants with residual albuminuria at month 4 had high rates of kidney end points, implying the need for added therapy for long-term kidney and cardiovascular benefits.

Background

Albuminuria is a strong indicator of kidney and cardiovascular risk in patients with CKD. We assessed risk associations between albuminuria at baseline and 4 months after randomization in a placebo-controlled trial of dapagliflozin and kidney end points in patients with CKD and albuminuria, with and without type 2 diabetes.

Methods

In this post hoc analysis of the dapagliflozin and prevention of adverse outcomes in CKD (DAPA-CKD) trial, 4304 adult patients with CKD were randomized to dapagliflozin 10 mg or placebo as an adjunct to maximally tolerated renin-angiotensin system inhibitors. The primary end point was a composite of sustained ≥50% decline in eGFR, kidney failure, or death from kidney or cardiovascular cause. The kidney composite end point was similar, but excluded cardiovascular death. We assessed associations among baseline albuminuria, early change in albuminuria (baseline to month 4), and residual albuminuria (month 4) with the primary composite and kidney composite end points using Cox proportional hazards regression analyses.

Results

Compared with placebo, dapagliflozin reduced urinary albumin–creatinine ratio (baseline to month 4) by 36.4% (95% confidence interval, 30.2% to 42.5%) and 20.5% (95% confidence interval, 11.6% to 29.5%) in participants with and without type 2 diabetes, respectively (P -interaction: 0.02). A reduction in urinary albumin–creatinine ratio from baseline to month 4 was associated with a lower risk of the primary and kidney composite end points with a similar risk gradient for participants with and without type 2 diabetes (P -interaction: 0.10 and 0.19, respectively). Residual albuminuria was associated with a similar risk of the primary and kidney composite end points in each treatment arm (P -interaction: 0.19 and 0.18, respectively).

Conclusions

Dapagliflozin reduced albuminuria, and the magnitude of albuminuria reduction showed similar proportional reductions in risks of the primary and kidney composite end points in participants with and without type 2 diabetes. Participants with residual albuminuria at month 4—whether randomized to dapagliflozin or placebo—experienced relatively high rates of CKD progression kidney end points, suggesting that therapies added to renin-angiotensin system inhibitors and dapagliflozin may be required to sustain kidney and cardiovascular health.

Clinical trial registry name and registration number:

A Study to Evaluate the Effect of Dapagliflozin on Renal Outcomes and Cardiovascular Mortality in Patients with CKD (DAPA-CKD), NCT03036150 .

Emerging perspectives in the management of IgA nephropathy: a comprehensive review

IgA nephropathy (IgAN) is the most prevalent form of primary glomerulonephritis worldwide and a leading cause of chronic kidney disease and renal failure. This disorder is characterized by the deposition of immune complexes containing galactose-deficient forms of IgA and complement C3 in the glomeruli. Until now, disease management relied mainly on optimized supportive care. Systemic corticosteroid therapy is proposed for patients at high risk of disease progression, but the effectiveness and safety of this approach are under debate. A significant proportion of patients do not respond to current therapies and require kidney replacement therapy at a young age, with substantial costs and impact on quality of life. Recently, there have been multiple joint efforts to improve the understanding of IgAN pathophysiology. International collaborations resulted in multiple ongoing clinical trials that are providing new insights toward innovative therapeutic options such as SGLT2 inhibitors, dual endothelin and angiotensin receptor blockers, targeted-release budesonide, B-cell proliferation and differentiation inhibitors, and complement system blockers. Based on this new evidence, revision of the guidelines to manage IgAN is expected to occur in the near future. In addition to the novelty in therapeutic agents, there is also a growing interest in new noninvasive biomarkers for IgAN screening, risk stratification to monitor the course of the disease, and the response to treatment. In this review, we discuss current knowledge on the pathophysiology of IgAN, disease management, and emerging advances in clinical translation of IgAN research.

Dual blockade of endothelin A and angiotensin II type 1 receptors with sparsentan as a novel treatment strategy to alleviate IgA nephropathy

INTRODUCTION

Although immunoglobulin A nephropathy (IgAN) had been discovered more than 50 years ago, 30-40% of IgAN patients still have primary glomerular disease that progresses to end-stage renal disease. However, various treatment strategies for IgAN have rapidly expanded in recent years to include endothelin (ET) receptor antagonists.

AREAS COVERED

In this review, we discuss the role of the ET-1/ETA receptor axis in the development of IgAN, especially focusing on the potential of sparsentan, a dual ET and angiotensin receptor antagonist as a novel therapy for IgAN.

EXPERT OPINION

Evaluation of the MEST-C score at the time of renal biopsy in IgAN is important in determining treatment strategies. If lesions are mainly in the acute phase, such as crescents, steroid therapy should be continued. However, if lesions are mainly in the chronic phase, such as glomerulosclerosis, sparsentan rather than steroid or angiotensin II receptor blocker alone may improve renal outcomes. Although further clinical studies are needed to back up these assumptions, appropriate combination of new drugs containing sparsentan and conventional drugs for IgAN treatment at the appropriate disease stage is expected to further inhibit the progression of renal damage.

Drug repurposing for glomerular diseases: an underutilized resource

Drug repurposing in glomerular disease can deliver opportunities for steroid-free regimens, enable personalized multi-target options for resistant or relapsing disease and enhance treatment options for understudied populations (for example, children) and in resource-limited settings. Identification of drug-repurposing candidates can be data driven, which utilizes existing data on disease pathobiology, drug features and clinical outcomes, or experimental, which involves high-throughput drug screens. Information from databases of approved drugs, clinical trials and PubMed registries suggests that at least 96 drugs on the market cover 49 targets with immunosuppressive potential that could be candidates for drug repurposing in glomerular disease. Furthermore, evidence to support drug repurposing is available for 191 immune drug target-glomerular disease pairs. Non-immunological drug repurposing includes strategies to reduce haemodynamic overload, podocyte injury and kidney fibrosis. Recommended strategies to expand drug-repurposing capacity in glomerular disease include enriching drug databases with glomeruli-specific information, enhancing the accessibility of primary clinical trial data, biomarker discovery to improve participant selection into clinical trials and improve surrogate outcomes and initiatives to reduce patent, regulatory and organizational hurdles.

Application of the updated International IgA Nephropathy Prediction Tool in children one or two years post-biopsy

The pediatric International IgA Nephropathy (IgAN) Prediction Tool comprises two models with and without ethnicity and is the first method to predict the risk of a 30% decline in estimated glomerular filtration rate (eGFR) or kidney failure in children at the time of biopsy using clinical risk factors and Oxford MEST histology scores. However, it is unknown if the Prediction Tool can be applied after a period of observation post-biopsy. Using an international multi-ethnic cohort of 947 children with IgAN, 38% of whom were followed into adulthood, the Prediction Tool was updated for use one year after biopsy. Compared to the original pediatric Prediction Tool, the updated post-biopsy Prediction Tool had a better model fit with higher R2D (51%/50% vs 20%), significant increase in 4-year C-statistics (0.83 vs 0.73/0.69, ΔC 0.09 [95% confidence interval 0.07-0.10] and ΔC 0.14 [0.12-0.15]) and better 4-year calibration with lower integrated calibration indices (0.74/0.54 vs 2.45/1.01). Results were similar after internal validation and when the models were applied two years after biopsy. Trajectories of eGFR after a baseline one year post-biopsy were non-linear and those at higher predicted risk started with a lower eGFR and experienced a more rapid decline over time. In children, eGFR had a variable rate of increase until 15-18 years old and then decreased linearly with a more rapid decline in higher risk groups that was similar to young adults of comparable risk. Thus, the original pediatric Prediction Tool should be used in children at the time of biopsy, and the updated pediatric Prediction Tool should be used to re-evaluate risk one or two years after biopsy.

Lessons from IgA Nephropathy Models

IgA nephropathy (IgAN) is the most common type of primary glomerulonephritis worldwide; however, the underlying mechanisms of this disease are not fully understood. This review explores several animal models that provide insights into IgAN pathogenesis, emphasizing the roles of aberrant IgA1 glycosylation and immune complex formation. It discusses spontaneous, immunization, and transgenic models illustrating unique aspects of IgAN development and progression. The animal models, represented by the grouped ddY (gddY) mouse, have provided guidance concerning the multi-hit pathogenesis of IgAN. In this paradigm, genetic and environmental factors, including the dysregulation of the mucosal immune system, lead to increased levels of aberrantly glycosylated IgA, nephritogenic immune complex formation, and subsequent glomerular deposition, followed by mesangial cell activation and injury. Additionally, this review considers the implications of clinical trials targeting molecular pathways influenced by IgAN (e.g., a proliferation-inducing ligand [APRIL]). Collectively, these animal models have expanded the understanding of IgAN pathogenesis while facilitating the development of therapeutic strategies that are currently under clinical investigation. Animal-model-based studies have the potential to facilitate the development of targeted therapies with reduced side effects for IgAN patients.

Endothelin Inhibitors in Chronic Kidney Disease: New Treatment Prospects

The endothelin system is reported to play a significant role in glomerular and tubulointerstitial kidney disease. In the kidney, endothelins are produced in mesangial cells and the glomerular basement membrane by the endothelium and podocytes. The endothelin system regulates glomerular function by inducing proliferation, increasing permeability and in effect proteinuria, and stimulating inflammation, tubular fibrosis, and glomerular scarring. Endothelin A receptor antagonists have been proven to delay the progression of chronic kidney disease and play a protective role in immunoglobulin A nephropathy, focal segmental glomerulosclerosis, and diabetic nephropathy. There are several ongoing research studies with ETAR antagonists in nondiabetic nephropathy, Alport disease, vasculitis and scleroderma nephropathy, which results are promising. Some reports suggest that the endothelin system might contribute to ischemia-reperfusion injury, acute graft rejection and deterioration of graft function. Endothelin inhibition in renal transplantation and its influence on graft survival is the future direction needing further research. The most frequent side effects associated with ETAR antagonists is fluid retention. Additionally, it should be considered if selective ETAR antagonists therapy needs to be co-administered with sodium-glucose co-transporter 2 inhibitors, renin-angiotensin-aldosterone inhibitors or diuretics and which patients should be recruited to such treatment to minimize the risk of adverse outcomes.

Podocyte-targeted therapies - progress and future directions

Podocytes are the key target cells for injury across the spectrum of primary and secondary proteinuric kidney disorders, which account for up to 90% of cases of kidney failure worldwide. Seminal experimental and clinical studies have established a causative link between podocyte depletion and the magnitude of proteinuria in progressive glomerular disease. However, no substantial advances have been made in glomerular disease therapies, and the standard of care for podocytopathies relies on repurposed immunosuppressive drugs. The past two decades have seen a remarkable expansion in understanding of the mechanistic basis of podocyte injury, with prospects increasing for precision-based treatment approaches. Dozens of disease-causing genes with roles in the pathogenesis of clinical podocytopathies have been identified, as well as a number of putative glomerular permeability factors. These achievements, together with the identification of novel targets of podocyte injury, the development of potential approaches to harness the endogenous podocyte regenerative potential of progenitor cell populations, ongoing clinical trials of podocyte-specific pharmacological agents and the development of podocyte-directed drug delivery systems, contribute to an optimistic outlook for the future of glomerular disease therapy.

Correlation of Urinary Soluble CD163 Levels With Disease Activity and Treatment Response in IgA Nephropathy

Introduction

The TESTING trial demonstrated that corticosteroids reduce the risk of kidney failure in patients with IgA nephropathy (IgAN) but increase the risk of serious adverse events. Reliable noninvasive biomarkers are needed to identify patients who would benefit most from corticosteroid therapy. Previous studies suggest glomerular macrophage infiltration is associated with response to immunosuppressive therapy in IgAN and urinary soluble CD163 ([u-sCD163], a marker of alternatively activated macrophages [M2]c macrophage) is correlated with clinical remission in vasculitis. This study aims to investigate the association between u-sCD163 and response of steroids therapy in IgAN.

Methods

We measured u-sCD163 in patients from a large IgAN cohort and Chinese participants of the TESTING trial. The correlation of baseline or serial u-sCD163 and their response of corticosteroids therapy or kidney outcomes were investigated.

Results

In cross-sectional analysis, u-sCD163 levels correlated with kidney macrophage infiltration, especially in crescentic areas, and with active lesions. Subgroup analysis of the TESTING cohort showed higher levels u-sCD163 were associated with greater benefits from corticosteroids therapy in proteinuria remission (odds ratio, 35.56 [95% confidence interval, CI: 7.62-292.34] vs. 3.94 [95% CI: 1.39-12.93], P for interaction: 0.036). Corticosteroids therapy significantly reduced u-sCD163 levels at 6 months compared to placebo group (79% [interquartile range: 58%-91%] vs. 37% [-11% to 58%], P <0.001). There was no difference in the suppressive effects on u-sCD163 by either dosage of corticosteroids (full and reduced-dose). The suppression of u-sCD163 was significantly associated with a reduced risk of kidney progression events (adjusted hazard ratio: 0.52, 95% CI: 0.30-0.93, P = 0.027).

Conclusion

u-sCD163 is a reliable noninvasive biomarker associated with active pathological lesions in IgAN and can guide glucocorticoid therapy.

Safety and efficacy of sparsentan versus irbesartan in focal segmental glomerulosclerosis and IgA nephropathy: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Sparsentan has shown positive effects on managing different subtypes of glomerulonephritis. The recent results of trials require a pooled analysis to validate these results.

AIM

We aim to assess the safety and efficacy of sparsentan versus irbesartan for patients with IgA nephropathy and focal glomerulosclerosis (FSGS).

METHODS

We conducted a systematic review and meta-analysis of randomized controlled trials retrieved by systematically searching PubMed, Web of Science, Scopus, and Cochrane through March 2024. We used Review Manager v.5.4 to pool dichotomous data using risk ratio (RR) and continuous data using mean difference (MD) with a 95% confidence interval (CI).

RESULTS

Three studies with a total of 884 patients were included. Sparsentan was superior to irbesartan in improving urine protein to creatinine ratio (UP/C) (ratio of percentage reduction 0.66, 95% CI [0.58 to 0.74], P < 0.001); as well as the proportion of patients achieved complete and partial remission of proteinuria (RR = 2.57, 95% CI [1.73 to 3.81], P < 0.001) and (RR = 1.63, 95% CI [1.4 to 1.91], P < 0.001) respectively. Regarding the effect on the glomerular filtration rate, the results estimate did not favor either sparsentan or irbesartan (MD = 1.98 ml/min per 1.73mm2, 95% CI [-1.05 to 5.01], P = 0.2). There were no significant differences in adverse events except for hypotension, which showed higher rates in the sparsentan group (RR = 2.02, 95% CI [1.3 to 3.16], P = 0.002).

CONCLUSION

Sparsentan is effective and has a good safety profile for treating FSGS and patients with IgA nephropathy. However, more well-designed RCTs against ARBs, ACE inhibitors, and steroids with larger sample sizes are needed to get conclusive evidence.

Targeting endothelin signaling in podocyte injury and diabetic nephropathy-diabetic kidney disease

Despite advances in diabetes management, there is an urgent need for novel therapeutic strategies since the current treatments remain insufficient in halting the progression of diabetic nephropathy-diabetic kidney disease (DN-DKD). This review is mainly addressed on the pivotal role of endothelin-1 in the pathophysiology of DN, with a specific focus on its effects on podocytes and the glomerular filtration barrier. Endothelin-1 promotes mesangial cell proliferation, sclerosis, and direct podocyte injury via the activation of endothelin type A and B receptors, that drive the progression of glomerulosclerosis in DN-DKD. Endothelin receptor antagonists, including drugs like atrasentan and sparsentan, have demonstrated nephroprotective effects in experimental models by reducing proteinuria and podocyte injury. The therapeutic potential to slow the progression of DN to end-stage kidney disease (ESKD) of these endothelin receptor antagonists in clinical practice is currently under evaluation. However, fluid retention and increased risk of heart failure associated with endothelin receptor antagonists need careful consideration. This review aims to provide an in-depth analysis of the pathophysiological role of endothelin and the emerging therapeutic implications of targeting this pathway in DN-DKD and discusses efficacy, safety, and the possibility of combining the new generation of endothelin receptor antagonists with the standard treatment of CKD and DN-DKD.

The role of endothelin receptor antagonists in IgA nephropathy

There is growing evidence of endothelin receptor antagonists (ERAs) in renoprotection in proteinuric kidney disease including IgA nephropathy (IgAN). Here, we review current evidence, including the use of sparsentan, atrasentan and zibotentan in IgAN. Recent trails of combination therapy including SGLT2 inhibitors and ERAs suggest possible benefit in further reduction of proteinuria and reducing ERA fluid-retention side effects although more evidence is needed for clinical applications.

State-of-Art Therapeutics in IgA Nephropathy

Immunoglobulin-A nephropathy (IgAN) is the most common primary glomerulonephritis in the world, with up to 40% of patients progressing to end-stage kidney disease (ESKD) within 30 years of diagnosis. IgAN is characterized by elevated serum levels of galactose-deficient IgA1 (Gd-IgA1), which leads to immune complex formation and deposition in the glomerular mesangium, causing kidney injury. A diverse disease course and the long-term follow-up required for clinically relevant endpoints (e.g., ESKD) have been barriers to the development of novel therapies in IgAN. Disease management has focused on supportive care with inhibitors of the renin-angiotensin system and, more recently, sodium-glucose transporter inhibitors to control proteinuria. The recent acceptance of proteinuria as a surrogate endpoint by regulatory bodies and a better understanding of disease pathology have helped to initiate the development of several novel treatments. Subsequently, a targeted-release formulation of budesonide and a dual endothelin/angiotensin inhibitor (sparsentan) have received accelerated approval for patients with IgAN. However, additional therapies are needed to target the different pathogenic mechanisms and individualize patient care. Several compounds currently under investigation target various effectors of pathology. There are promising clinical results from emerging compounds that target the generation of Gd-IgA1 by B cells, including inhibitors of A PRoliferation-Inducing Ligand (APRIL) and dual inhibitors of APRIL and B-cell activating factor (BAFF). Other investigational therapies target the complement cascade by inhibiting proteins of the lectin or alternative pathways. As the therapeutic landscape evolves, it will be important to revise treatment guidelines and develop updated standards of care.

Access to Expensive Therapies and Diagnostics for Kidney Care in Switzerland

Key Points

Inconsistent responses to the prior approval process for similar patients may lead to inequities in access to optimal care. The prior authorizations process leads to frustration among nephrologists and may contribute to moral distress. The prior authorizations process may lead to important delays in kidney care.

Background

In Switzerland, nephrologists must frequently obtain preauthorizations from health insurers for certain medications/tests for individual patients. These are time consuming, and outcomes are inconsistent. Clinical experience suggests inequities in access to expensive medications, related to need for and processes involved with medication preauthorization requests.

Methods

An anonymous survey was conducted between November 2021 and March 2022 regarding experiences in applying for preauthorizations for medications and genetic testing required for kidney care among nephrologists in Switzerland.

Results

Ninety-four responses were received. The most common medications reported to require preapprovals were rituximab, sodium glucose cotransporter-2 inhibitors (SGLT2is), mycophenolate mofetil, and eculizumab. Rebuttals were reported to be most frequently required for rituximab, eculizumab, and SGLT2is, also the most frequently denied medications. Most frequent genetic testing requests were for complement and Alport spectrum disorders. Requests for genetic testing were reported to be most frequently denied for cystic renal diseases, congenital syndromes, and nephrotic syndromes. Most nephrologists found requests for further information from the health insurers seldom reasonable, 72% reported it was rarely/never possible to engage with the insurance physicians, 69% were concerned insurance physicians did not have relevant expertise. Respondents reported receiving different responses from different insurers for similar requests more frequently than from the same insurer (58% versus 8%). One in three nephrologists reported that the preauthorizations process frequently resulted in a clinically relevant delay in treatment. Four of five respondents reported that the preauthorization process frequently made them feel that they could not do their best for the patient.

Conclusions

From the perspective of nephrologists, the preauthorizations process in Switzerland is cumbersome, is not transparent and inequitable, may result in denial or delays of important treatment for patients, and contributes to moral distress.

Current understanding and new insights in the treatment of IgA nephropathy

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide, and almost all patients are at risk of progression to end-stage kidney disease within their lifetime. The mechanisms responsible for the presentation and development of IgAN are required for the development of highly targeted therapies for this disease. In this review, we first demonstrate the current treatment strategy of IgAN recommended by the 2021 KDIGO guideline. Then, we update the new insights into disease pathogenesis based on the well acknowledged 'multiple-hit hypothesis' and provide the potential therapeutic targets involved in the upstream production of pathogenic IgA1 and the downstream complement activation. Finally, the recent large randomized controlled trials focusing on these novel targets have been summarized, among which Nefecon and Sparsentan have received approval and Telitacicept have been used off-label for IgAN. In the future, emerging treatment approaches for IgAN is likely to evolve, which will signify a shift in the management of the IgAN from traditional immunosuppressive approaches to an era of targeted treatment based on the understanding of the pathogenic mechanisms.

Sparsentan is superior to losartan in the gddY mouse model of IgA nephropathy

BACKGROUND

The mechanism leading to the development of immunoglobulin A nephropathy (IgAN) remains to be completely understood. Endothelin-1 (ET-1) as well as angiotensin II (AngII) promote glomerular injury, tubulointerstitial inflammation and fibrosis leading to chronic kidney disease. Sparsentan, a dual endothelin angiotensin receptor antagonist, recently received accelerated approval in the USA for the reduction of proteinuria in adults with IgAN at high risk of disease progression. To elucidate the mechanisms by which sparsentan is efficacious in IgAN, we examined the effect of treatment in gddY mice, a spontaneous IgAN mouse model, versus the monoselective angiotensin II type 1 receptor (AT1R) antagonist, losartan, on the development of renal injury at doses resulting in similar blood pressure lowering.

METHODS

Four-week-old gddY mice were given control chow, chow containing sparsentan or drinking water containing losartan until 12 or 20 weeks old.

RESULTS

Remarkably, the albumin:creatine ratio (ACR) was attenuated more rapidly and to a greater extent in mice treated with sparsentan than those treated with losartan. The decrease in ACR from baseline after 4 weeks of treatment correlated with beneficial effects of sparsentan on glomerulosclerosis and protection of podocytes and glycocalyx after 16 weeks of treatment across treatment groups; thus, sparsentan treatment delayed development of renal injury to a greater extent than losartan. Expression of mRNA for ET-1, endothelin type A receptor and AT1R and proinflammatory genes was upregulated in 12-week-old gddY mice and was prevented by sparsentan and losartan to a comparable extent.

CONCLUSIONS

The results of this study, and in light of the results of the phase 3 PROTECT trial, provide a novel perspective and understanding of the mechanisms by which sparsentan has a beneficial renoprotective effect against IgAN compared with AT1R antagonism alone.

Contemporary review of IgA nephropathy

IgA nephropathy (IgAN) is considered the most common primary glomerulonephritis worldwide with a predilection for Asian-Pacific populations and relative rarity in those of African descent. Perhaps 20%-50% of patients progress to kidney failure. The pathogenesis is incompletely understood. Mesangial deposition of immune complexes containing galactose-deficient IgA1 complexed with anti-glycan IgG or IgA antibodies results in mesangial cell activation and proliferation, inflammatory cell recruitment, complement activation, and podocyte damage. Diagnosis requires a biopsy interpreted by the Oxford criteria. Additional pathologic features include podocytopathy, thrombotic microangiopathy, and C4d staining. Biomarkers predicting adverse outcomes include proteinuria, reduced GFR, hypertension, and pathology. Acceptable surrogate endpoints for therapeutic trials include ongoing proteinuria and rate of eGFR decline. The significance of persisting hematuria remains uncertain. The mainstay of therapy is supportive, consisting of lifestyle modifications, renin-angiotensin inhibition (if hypertensive or proteinuric), sodium-glucose-transporter 2 inhibition (if GFR reduced or proteinuric), and endothelin-receptor antagonism (if proteinuric). Immunosuppression should be considered for those at high risk after maximal supportive care. Corticosteroids are controversial with the most positive results observed in Chinese. They carry a high risk of serious side effects. Similarly, mycophenolate may be most effective in Chinese. Other immunosuppressants are of uncertain benefit. Tonsillectomy appears efficacious in Japanese. Active areas of investigation include B-cell inhibition with agents targeting the survival factors BAFF and APRIL and complement inhibition with agents targeting the alternate pathway (Factors B and D), the lectin pathway (MASP-2), and the common pathway (C3 and C5). Hopefully soon, the who and the how of immunosuppression will be clarified, and kidney failure can be forestalled.

Role of serum complement C3 and C4 on kidney outcomes in IgA nephropathy

IgA Nephropathy (IgAN) is the most prevalent glomerular disease worldwide. Complement system activation is crucial in its pathogenesis. Few studies correlated serum C3 and C4 with disease activity and prognosis. This retrospective study investigated the prognostic value of serum complement at the time of diagnosis in patients with IgAN. Specifically we evaluated whether adding serum C3 and C4 levels to established predictive models-one based on variables related to chronic kidney disease (CKD) progression and another incorporating variables from the International IgA Prediction Tool (IntIgAPT)-enhances the accuracy of outcome prediction. A composite renal outcome was defined as 50% decline in eGFR or onset of kidney failure. 101 patients were stratified according to baseline C3 levels in three groups (Low, Medium and High). During a median follow-up of 54 months, the Low group exhibited higher incidence of primary outcome (16.3 events vs 2.9 and 1.7 events × 100 pts/year, p = 0.0026). Model-1 (M1), consisting of CKD progression variables, and Model-3 (M3), comprising IntIgANPT variables, were implemented with baseline C3 and C4 to create Model-2 (M2) and Model-4 (M4), respectively. M2 demonstrated better predictive performance over M1, showing higher discrimination (lower AIC and BIC, higher C-index and NR2). Similarly, M4 outperformed M3, showing enhanced outcome prediction when C3 and C4 levels were added. Implementation of serum C3 and C4 can enhance prediction accuracy of already-validated prognostic models in IgAN. Lower C3 and higher C4 levels were associated with poorer prognosis, highlighting a more 'Complement-Pathic' subset of patients.

IgA Nephropathy: Emerging Mechanisms of Disease

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis reported across the world and is characterized by immunoglobulin A (IgA) dominant mesangial deposits, which are poorly O-glycosylated. This deposition leads to a cascade of glomerular and tubulointerstitial inflammation and fibrosis, which can progress to chronic kidney disease. The variability in rate of progression reflects the many genetic and environmental factors that drive IgAN. Here, we summarize the contemporary understanding of the disease mechanisms that drive IgAN and provide an overview of new and emerging therapies, which target these mechanisms.

Advancements in understanding the role of intestinal dysbacteriosis mediated mucosal immunity in IgA nephropathy

IgA nephropathy, presently recognized as the foremost primary glomerular disorder, emerges as a principal contributor to renal failure globally, with its pathogenesis yet to be fully elucidated. Extensive research has highlighted the critical role of gut microbiome in the onset and progression of IgA nephropathy, underscoring its importance in accurately delineating the disease's etiology. For example, gut microbiome dysbacteriosis can lead to the production of nephritogenic IgA1 antibodies, which form immune complexes that deposit in the kidneys, causing inflammation and damage. The gut microbiome, a source of numerous bioactive compounds, interacts with the host and plays a regulatory role in gut-immune axis modulation, earning it the moniker of the "second brain." Recent investigations have particularly emphasized a significant correlation between IgA nephropathy and gut microbiome dysbacteriosis. This article offers a detailed overview of the pathogenic mechanisms of IgA nephropathy, specifically focusing on elucidating how alterations in the gut microbiome are associated with anomalies in the intestinal mucosal system in IgA nephropathy. Additionally, it describes the possible influence of gut microbiome on recurrent IgA nephropathy following kidney transplantation. Furthermore, it compiles potential therapeutic interventions, offering both theoretical and practical foundations for the management of IgA nephropathy. Lastly, the challenges currently faced in the therapeutic approaches to IgA nephropathy are discussed.

Mechanism of protective actions of sparsentan in the kidney: lessons from studies in models of chronic kidney disease

Simultaneous inhibition of angiotensin II AT1 and endothelin ETA receptors has emerged as a promising approach for treatment of chronic progressive kidney disease. This therapeutic approach has been advanced by the introduction of sparsentan, the first dual AT1 and ETA receptor antagonist. Sparsentan is a single molecule with high affinity for both receptors. It is US Food and Drug Administration approved for immunoglobulin A nephropathy (IgAN) and is currently being developed as a treatment for rare kidney diseases, such as focal segmental glomerulosclerosis. Clinical studies have demonstrated the efficacy and safety of sparsentan in these conditions. In parallel with clinical development, studies have been conducted to elucidate the mechanisms of action of sparsentan and its position in the context of published evidence characterizing the nephroprotective effects of dual ETA and AT1 receptor inhibition. This review summarizes this evidence, documenting beneficial anti-inflammatory, antifibrotic, and hemodynamic actions of sparsentan in the kidney and protective actions in glomerular endothelial cells, mesangial cells, the tubulointerstitium, and podocytes, thus providing the rationale for the use of sparsentan as therapy for focal segmental glomerulosclerosis and IgAN and suggesting potential benefits in other renal diseases, such as Alport syndrome.

Is endothelin targeting finally ready for prime time?

The endothelin family of peptides has long been recognized as a physiological regulator of diverse biological functions and mechanistically involved in various disease states, encompassing, among others, the cardiovascular system, the kidney, and the nervous system. Pharmacological blockade of the endothelin system, however, has encountered strong obstacles in its entry into the clinical mainstream, having obtained only a few proven indications until recently. This translational gap has been attributable predominantly to the relevant side effects associated with endothelin receptor antagonism (ERA), particularly fluid retention. Of recent, however, an expanding understanding of the pathophysiological processes involving endothelin, in conjunction with the development of new antagonists of endothelin receptors or adjustment of their doses, has driven a flourish of new clinical trials. The favorable results of some of them have extended the proven indications for ET targeting to a variety of clinical conditions, including resistant arterial hypertension and glomerulopathies. In addition, on the ground of strong preclinical evidence, other studies are ongoing to test the potential benefits of ERA in combination with other treatments, such as sodium-glucose co-transporter 2 inhibition in fluid retentive states or anti-cancer therapies in solid tumors. Furthermore, antibodies providing long-term blockade of endothelin receptors are under testing to overcome the short half-life of most small molecule endothelin antagonists. These efforts may yet bring new life to the translation of endothelin targeting strategies in clinical practice.

A phase 2b, randomized, double-blind, placebo-controlled, clinical trial of atacicept for treatment of IgA nephropathy

Atacicept is a first-in-class, dual anti-B-cell Activation Factor-A Proliferation-Inducing Ligand fusion protein in clinical evaluation for treatment of IgA nephropathy. To compare efficacy and safety of atacicept versus placebo in patients with IgAN, this randomized, double-blind, placebo-controlled phase 2b clinical trial ORIGIN enrolled 116 individuals with biopsy-proven IgA nephropathy. Participants were randomized to atacicept 150, 75, or 25 mg versus placebo once weekly for up to 36 weeks. Primary and key secondary endpoints were changes in urine protein creatinine ratio based on 24-hour urine collection at weeks 24 and 36, respectively, in the combined atacicept 150 mg and 75 mg group versus placebo. The primary endpoint was met at week 24 as the mean urine protein creatinine ratio was reduced from baseline by 31% in the combined atacicept group versus 8% with placebo, resulting in a significant 25% reduction with atacicept versus placebo. At week 36, the key secondary endpoint was met as the mean urine protein creatinine ratio reduced from baseline by 34% in the combined atacicept group versus a 2% increase with placebo, resulting in a significant 35% reduction with atacicept versus placebo. The reduction in proteinuria was accompanied by stabilization in endpoint eGFR with atacicept compared to a decline with placebo at week 36, resulting in significant between-group geometric mean difference of 11%, approximating an absolute difference of 5.7 mL/min/1.73m2. Endpoint galactose deficient IgA1 levels significantly decreased from baseline by 60% versus placebo. The safety profile of atacicept was like placebo. Thus, our results provide evidence to support a pivotal, phase 3 study of atacicept in IgA nephropathy.

Sparsentan for Focal Segmental Glomerulosclerosis in the DUET Open-Label Extension: Long-term Efficacy and Safety

Rationale & Objective

Sparsentan is a novel, non-immunosuppressive, single-molecule, dual endothelin angiotensin receptor antagonist (DEARA) examined in the ongoing phase 2 DUET trial for focal segmental glomerulosclerosis (FSGS). In the DUET 8-week double-blind period, sparsentan resulted in greater proteinuria reduction versus irbesartan. We report the long-term efficacy and safety of sparsentan during the open-label extension over more than 4 years.

Study Design

Patients were examined from their first sparsentan dose (double-blind period or open-label extension) through 4.6 years.

Setting & Participants

Patients with FSGS, excluding secondary FSGS.

Intervention

Sparsentan (200, 400, and 800 mg/d).

Outcomes

Urinary protein-creatinine ratio, FSGS partial remission endpoint (urinary protein-creatinine ratio ≤1.5 g/g and >40% reduction from baseline), estimated glomerular filtration rate, and blood pressure approximately every 12 weeks. Treatment-emergent adverse events by year and cases/100 patient-years.

Results

109 patients were enrolled; 108 received ≥1 sparsentan dose; 103 entered the open-label extension (68 sparsentan, 35 irbesartan during the double-blind period). Sparsentan was ongoing in 45/108 patients (41.7%); median time to treatment discontinuation was 3.9 years (95% CI, 2.6-5.2). Mean percent proteinuria reduction from baseline was sustained through follow-up. Achieving partial remission within 9 months of first sparsentan dose (52.8% of patients) versus not achieving (47.2%) was associated with significantly slower rate of estimated glomerular filtration rate decline over the entire treatment period (-2.70 vs -6.56; P = 0.03) and in the first 2 years (-1.69 vs -6.46; P = 0.03). The most common treatment-emergent adverse events (>9 cases/100 patient-years) were headache, peripheral edema, upper respiratory infection, hyperkalemia, and hypotension. Peripheral edema and hypotension declined from year 1 (13.9% and 15.7% of patients, respectively) to ≤4% in years ≥2. There were no cases of heart failure and no patient deaths.

Limitations

The open-label extension does not include a comparison group.

Conclusions

Long-term sparsentan treatment showed sustained proteinuria reduction and a consistent safety profile.

Sparsentan: A First-in-Class Dual Endothelin and Angiotensin II Receptor Antagonist

OBJECTIVE

To provide an overview of the guidelines on the management of immunoglobulin A nephropathy (IgAN) and focal segmental glomerulosclerosis (FSGS), review the evidence for sparsentan, and discuss its place in therapy.

DATA SOURCES

A literature search was conducted using MEDLINE, EMBASE, and clinicaltrials.gov using the search terms "sparsentan" and "RE-021" up to the end of Jun 2023.

STUDY SELECTION AND DATA EXTRACTION

English studies were included if they evaluated the pharmacology, pharmacokinetics, efficacy, and safety of sparsentan in human subjects. Information from the Food and Drug Administration (FDA) and manufacturer's monograph were also extracted.

DATA SYNTHESIS

In comparison with irbesartan, sparsentan reduced urine protein-to-creatinine ratio (UPCR) in both IgAN (-49.8% vs -15.1% at interim 36 weeks) and FSGS (-44.8% vs -18.5% at 8 weeks). Hypotension and edema were the most common adverse events in the sparsentan groups. Hepatotoxicity appears to be comparable between sparsentan and irbesartan in short-term results.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING DRUGS

Sparsentan provides a new option for patients with IgAN who are otherwise at high risk of progressive kidney disease. Continued FDA approval is dependent on long-term study results on renal function decline and safety.

CONCLUSION

Sparsentan reduces proteinuria in IgAN and FSGS, and has expedited approval by the FDA for IgAN in patients at risk of rapid disease progression, generally at urine protein-to-creatinine ratio (UPCR) ≥1.5 g/g. Interim results from PROTECT and results from DUET showed promise for improving proteinuria in IgAN and FSGS. Long-term renal function benefit and safety data are pending.

Sparsentan: the first and only non-immunosuppressive therapy for the reduction of proteinuria in IgA nephropathy

INTRODUCTION

IgA nephropathy is one of the most common forms of glomerular disease. Patients with persistent proteinuria are at increased risk of progression to kidney failure. There is a significant need for safe and effective therapies to lower proteinuria in these patients. Sparsentan is a non-immunosuppressive agent that acts as a dual angiotensin and endothelin receptor antagonist. It lowers proteinuria in experimental models of glomerular disease and in affected patients.

AREAS COVERED

This review covers the immunological and non-immunological actions of sparsentan in glomerular disease. It reviews the clinical trials that evaluated the impact of the drug in pediatric and adult patients with IgA nephropathy. It places the use of sparsentan in an overall treatment paradigm for the full spectrum of patients with IgA nephropathy including nonspecific renoprotective agents such as inhibitors of the renin-angiotensin-aldosterone axis and SGLT2 transporter and immunosuppressive drugs. The review represents a search of the current literature about the effect of the drug on normal physiology and the pathogenesis of IgA nephropathy.

EXPERT OPINION

The safety, tolerability, and therapeutic efficacy of sparsentan have been demonstrated in long-term studies of patients with primary glomerular diseases extending over 5 years. The evidence in support of a beneficial treatment effect of sparsentan is stronger in IgAN than in FSGS. It is anticipated that sparsentan will supplant the use of ACEI or ARB as the first-line therapy to reduce proteinuria prior to the implementation of immunosuppressive agents in patients with IgA nephropathy. It may be combined with other renoprotective drugs like SGLT2 inhibitors. Practice guidelines are needed to promote safe and effective use of this new drug by nephrologists caring for patients with IgAN in all clinical settings.

Causal association of plasma circulating metabolites with nephritis: a Mendelian randomization study

Background

Nephritis is a pivotal catalyst in chronic kidney disease (CKD) progression. Although epidemiological studies have explored the impact of plasma circulating metabolites and drugs on nephritis, few have harnessed genetic methodologies to establish causal relationships.

Methods

Through Mendelian randomization (MR) in two substantial cohorts, spanning large sample sizes, we evaluated over 100 plasma circulating metabolites and 263 drugs to discern their causal effects on nephritis risk. The primary analytical tool was the inverse variance weighted (IVW) analysis. Our bioinformatic scrutiny of GSE115857 (IgA nephropathy, 86 samples) and GSE72326 (lupus nephritis, 238 samples) unveiled anomalies in lipid metabolism and immunological characteristics in nephritis. Thorough sensitivity analyses (MR-Egger, MR-PRESSO, leave-one-out analysis) were undertaken to verify the instrumental variables' (IVs) assumptions.

Results

Unique lipoprotein-related molecules established causal links with diverse nephritis subtypes. Notably, docosahexaenoic acid (DHA) emerged as a protective factor for acute tubulointerstitial nephritis (ATIN) (OR1 = 0.84, [95% CI 0.78-0.90], p1 = 0.013; OR2 = 0.89, [95% CI 0.82-0.97], p2 = 0.007). Conversely, multivitamin supplementation minus minerals notably increased the risk of ATIN (OR = 31.25, [95% CI 9.23-105.85], p = 0.004). Reduced α-linolenic acid (ALA) levels due to lipid-lowering drugs were linked to both ATIN (OR = 4.88, [95% CI 3.52-6.77], p < 0.001) and tubulointerstitial nephritis (TIN) (OR = 7.52, [95% CI 2.78-20.30], p = 0.042). While the non-renal drug indivina showed promise for TIN treatment, the use of digoxin, hydroxocobalamin, and liothyronine elevated the risk of chronic tubulointerstitial nephritis (CTIN). Transcriptome analysis affirmed that anomalous lipid metabolism and immune infiltration are characteristic of IgA nephropathy and lupus nephritis. The robustness of these causal links was reinforced by sensitivity analyses and leave-one-out tests, indicating no signs of pleiotropy.

Conclusion

Dyslipidemia significantly contributes to nephritis development. Strategies aimed at reducing plasma low-density lipoprotein levels or ALA supplementation may enhance the efficacy of existing lipid-lowering drug regimens for nephritis treatment. Renal functional status should also be judiciously considered with regard to the use of nonrenal medications.

A year in pharmacology: new drugs approved by the US Food and Drug Administration in 2023

With 54 new drugs and seven cellular and gene therapy products, the approvals by the US Food and Drug Administration (FDA) recovered 2023 from the 2022 dent back to the levels of 2020-2021. As in previous years of this annual review, we assign these new drugs to one of three levels of innovation: first drug against a condition ("first-in-indication"), first drug using a novel molecular mechanism ("first-in-class"), and "next-in-class," i.e., a drug using an already exploited molecular mechanism. We identify four (7%) "first-in-indication," 22 (36%) "first-in-class," and 35 (57%) "next-in-class" drugs. By treatment area, rare diseases (54%) and cancer drugs (23%) were once again the most prevalent (and partly overlapping) therapeutic areas. Other continuing trends were the use of accelerated regulatory approval pathways and the reliance on biopharmaceuticals (biologics). 2023 marks the approval of a first therapy based on CRISPR/Cas9 gene editing.

Primary IgA Nephropathy: New Insights and Emerging Therapies

Primary IgA nephropathy (IgAN) is a common glomerular disorder defined by predominant mesangial IgA deposition. Once thought to follow a progressive course in 10-20% of those diagnosed, emerging evidence now suggests most will progress to kidney failure over their lifetimes. Although the lack of safe and effective treatments to impede disease progression continues to present a challenge, the landscape of IgAN has dramatically evolved over the last 2 years. Driven by fundamental changes to accepted end points for IgAN clinical trials as well as fascinating new insights into the pathophysiology of IgAN, a swathe of novel and repurposed therapies are currently being evaluated. Already, two novel drugs, targeted-release formulation budesonide and sparsentan, have received conditional approvals for the treatment of IgAN, with sodium glucose co-transporter 2 inhibitors establishing themselves as further options. Soon to join this ensemble are likely to be treatments that modulate the complement system and B-cell activity; several are currently undergoing clinical trials in IgAN with promising interim results. In this review, we provide an overview of evolving epidemiological insights, disease mechanisms, emerging therapies, and contemporary challenges surrounding the management of IgAN.

New therapies for immunoglobulin A nephropathy: what's the standard of care in 2023?

PURPOSE OF REVIEW

As the most common primary glomerulonephritis, immunoglobulin A (IgA) nephropathy (IgAN) is an important cause of kidney failure and mortality. Until recently, therapeutic options were limited. Fortunately, there have been numerous recent clinical trials demonstrating efficacy of new therapies in slowing chronic kidney disease (CKD) progression at varying stages of disease.

RECENT FINDINGS

The TESTING trial has provided high-quality evidence for slowing estimated glomerular filtration rate (eGFR) decline with a reduced-dose glucocorticoid regimen, while demonstrating an improved safety profile. Targeted-release budesonide represents a well tolerated therapy for reducing eGFR decline. Mycophenolate mofetil may reduce CKD progression in some populations, while hydroxychloroquine is efficacious in reducing proteinuria. Sodium-glucose cotransporter (SGLT2) inhibitors and sparsentan are effective therapies for CKD due to IgAN, but should not be used in lieu of disease-modifying immunosuppressive therapy. Many new therapies are approaching readiness for clinical use.

SUMMARY

Numerous therapeutic options now exist and include disease-modifying and nephroprotective drugs. Identifying the right treatment for the right patient is now the clinical challenge and, with new drugs on the horizon, represents the primary unmet research need in this rapidly-developing field.

Sparsentan ameliorates glomerular hypercellularity and inflammatory-gene networks induced by IgA1-IgG immune complexes in a mouse model of IgA nephropathy

IgA nephropathy (IgAN) is characterized by glomerular deposition of immune complexes (ICs) consisting of IgA1 with O-glycans deficient in galactose (Gd-IgA1) and Gd-IgA1-specific IgG autoantibodies. These ICs induce kidney injury, and in the absence of disease-specific therapy, up to 40% of patients with IgAN progress to kidney failure. IgA1 with its clustered O-glycans is unique to humans, which hampered development of small-animal models of IgAN. Here, we used a model wherein engineered ICs (EICs) formed from human Gd-IgA1 and recombinant human IgG autoantibody are injected into nude mice to induce glomerular injury mimicking human IgAN. In this model, we assessed the protective effects of sparsentan, a single-molecule dual endothelin angiotensin receptor antagonist (DEARA) versus vehicle on EIC-induced glomerular proliferation and dysregulation of gene expression in the kidney. Oral administration of sparsentan (60 or 120 mg/kg daily) to mice intravenously injected with EIC attenuated the EIC-induced glomerular hypercellularity. Furthermore, analysis of changes in the whole kidney transcriptome revealed that key inflammatory and proliferative biological genes and pathways that are upregulated in this EIC model of IgAN were markedly reduced by sparsentan, including complement genes, integrin components, members of the mitogen-activated protein kinase family, and Fc receptor elements. Partial overlap between mouse and human differentially expressed genes in IgAN further supported the translational aspect of the immune and inflammatory components from our transcriptional findings. In conclusion, our data indicate that in the mouse model of IgAN, sparsentan targets immune and inflammatory processes leading to protection from mesangial hypercellularity.NEW & NOTEWORTHY The mechanisms by which deposited IgA1 immune complexes cause kidney injury during early phases of IgA nephropathy are poorly understood. We used an animal model we recently developed that involves IgA1-IgG immune complex injections and determined pathways related to the induced mesangioproliferative changes. Treatment with sparsentan, a dual inhibitor of endothelin type A and angiotensin II type 1 receptors, ameliorated the induced mesangioproliferative changes and the associated alterations in the expression of inflammatory genes and networks.