Treatment of FSGS in Children

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.

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.

Focal Segmental Glomerulosclerosis Patient Baseline Characteristics in the Sparsentan Phase 3 DUPLEX Study

Introduction

The phase 3 DUPLEX trial is evaluating sparsentan, a novel, nonimmunosuppressive, single-molecule dual endothelin angiotensin receptor antagonist, in patients with focal segmental glomerulosclerosis (FSGS).

Methods

DUPLEX (NCT03493685) is a global, multicenter, randomized, double-blind, parallel-group, active-controlled study evaluating the efficacy and safety of sparsentan 800 mg once daily versus irbesartan 300 mg once daily in patients aged 8 to 75 years (USA/UK) and 18 to 75 years (ex-USA/UK) weighing ≥20 kg with biopsy-proven FSGS or documented genetic mutation in a podocyte protein associated with FSGS, and urine protein-to-creatinine ratio (UP/C) ≥1.5 g/g. Baseline characteristics blinded to treatment allocation are reported descriptively.

Results

The primary analysis population includes 371 patients (336 adult, 35 pediatric [<18 years]) who were randomized and received study drug (median age, 42 years). Patients were White (73.0%), Asian (13.2%), Black/African American (6.7%), or Other race (7.0%); and from North America (38.8%), Europe (36.1%), South America (12.7%), or Asia Pacific (12.4%). Baseline median UP/C was 3.0 g/g; 42.6% in nephrotic-range (UP/C >3.5 g/g [adults]; >2.0 g/g [pediatrics]). Patients were evenly distributed across estimated glomerular filtration rate (eGFR) categories corresponding to chronic kidney disease (CKD) stages 1 to 3b. Thirty-three patients (9.4% of 352 evaluable samples) had pathogenic or likely pathogenic (P/LP) variants of genes essential to podocyte structural integrity and function, 27 (7.7%) had P/LP collagen gene (COL4A3/4/5) variants, and 14 (4.0%) had high-risk APOL1 genotypes.

Conclusions

Patient enrollment in DUPLEX, the largest interventional study in FSGS to date, will enable important characterization of the treatment effect of sparsentan in a geographically broad and clinically diverse FSGS population.

Idiopathic Nephrotic Syndrome in Children in Chad: Epidemiology and Clinical Outcomes

INTRODUCTION

Nephrotic syndrome (NS) remains the most common presentation of glomerular diseases in children. Moreover, NS is primarily idiopathic, accounting for 90% of cases, with an average onset age between 2 and 10 years. The objective of our study was to describe the characteristics and outcomes of NS in children from three major hospitals in one of the world's poorest countries, Chad.

PATIENTS AND METHODS

This observational, cross-sectional, descriptive, and multicenter study took place over a period of 36 months (1 January 2019-31 December 2021) and was carried out in three hospitals in N'Djamena, Chad. Children aged 1-15 years presenting with NS were included in the study.

RESULTS

Out of 16,776 children hospitalized or followed up with in outpatient clinics, 24 cases of NS were identified, yielding a prevalence of 0.14%. The median age at presentation was 6.16 years (1-10). Nineteen children were male (sex ratio 3.8). Eight cases were classified as impure NS (33.3%). Edema was present in all patients, while oliguria was present in 29.16% (n = 7), and arterial hypertension was present in 20.83% (n = 5) of cases. Mean proteinuria, albuminemia, and total proteins were 2.86g/L, 19.13g/L and 30.41g/L, respectively. The median serum creatinine was 87.3 µmol/L (75-1375 µmol/L). Three patients experienced acute renal failure upon admission. Four patients had secondary NS. All idiopathic NS patients (n = 20) who had received corticosteroid therapy had a 90% response rate to steroids. Non-responsive or relapsed patients underwent kidney biopsy (n = 7), revealing focal segmental glomerulosclerosis (FSGS; n = 4) as the most common histological lesion, followed by minimal change disease (n = 2) and membranoproliferative glomerulonephritis (n = 1). The median length of hospitalization stay was 10.67 (5-27) days. None of the patients with idiopathic NS died. At the last follow-up, sixteen patients (80%) achieved long-term complete remission with normal renal function; however, four of those had subsequent relapses. One patient with secondary NS died.

CONCLUSION

In Chad, childhood idiopathic nephrotic syndrome predominantly affects young males; steroid sensitivity is as high as 95%, and in the long-term, 80% of patients achieve remission with normal renal function.

Implications of Complete Proteinuria Remission at any Time in Focal Segmental Glomerulosclerosis: Sparsentan DUET Trial

Introduction

Focal segmental glomerulosclerosis (FSGS) is a rare glomerular disease with high unmet clinical need. Interest in proteinuria as a surrogate end point for regulatory approval of novel treatments has increased. We assessed the relationship between achieving complete remission (CR) of proteinuria at least once during follow-up and long-term kidney outcomes.

Methods

This post hoc analysis included all patients enrolled in the DUET trial of sparsentan in FSGS and the open-label extension (OLE). Evaluations occurred every 12 weeks, including blood pressure (BP), edema, proteinuria, and kidney function. CR was defined as a urine protein/creatinine ratio ≤0.3g/g in a first morning urine sample.

Results

A total of 108 patients who received ≥1 sparsentan dose were included in this study. During a median follow-up of 47.0 months, 46 patients (43%) experienced ≥1 CR, 61% occurring within 12 months of starting sparsentan. There was an increased likelihood of CR with a higher sparsentan dose or baseline subnephrotic-range proteinuria. Achieving ≥1 CR was associated with significantly slower rate of estimated glomerular filtration rate (eGFR) decline versus non-CR patients (P < 0.05). Use of immunosuppressive agents was more frequent in patients who achieved a CR. However, the antiproteinuric effect of sparsentan was additive to that achieved with concomitant immunosuppressive treatment. No unanticipated adverse events occurred.

Conclusion

We conclude that sparsentan can be safely administered for extended periods and exerts a sustained antiproteinuric effect. Achievement of CR at any time during follow-up, even if it is not sustained, may be an indicator of a favorable response to treatment and a predictor of improved kidney function outcomes.

STAT-3 signaling role in an experimental model of nephropathy induced by doxorubicin

The focal segmental glomerulosclerosis (FSGS) is one of the most frequent glomerulopathy in the world, being considered a significative public health problem worldwide. The disease is characterized by glomerular loss mainly due to inflammation process and collagen fibers deposition. STAT-3 is a transcription factor associated with cell differentiation, migration and proliferation and in renal cells it has been related with fibrosis, acting on the progression of the lesion. Considering this perspective, the present study evaluated the involvement of STAT-3 molecule in an experimental model of FSGS induced by Doxorubicin (DOX). DOX mimics primary FSGS by causing both glomerular and tubular lesions and the inhibition of the STAT3 pathway leads to a decrease in fibrosis and attenuation of kidney damage. We described here a novel FSGS experimental model in a strain of genetically heterogeneous mice which resembles the reality of FSGS patients. DOX-injected mice presented elevated indices of albuminuria and glycosuria, that were significantly reduced in animals treated with a STAT-3 inhibitor (STATTIC), in addition with a decrease of some inflammatory molecules. Moreover, we detected that SOCS-3 (a regulator of STAT family) was up-regulated only in STATTIC-treated mice. Finally, histopathological analyzes showed that DOX-treated group had a significant increase in a tubulointerstitial fibrosis and tubular necrosis, which were not identified in both control and STATTIC groups. Thus, our results indicate that STAT-3 pathway possess an important role in experimental FSGS induced by DOX and may be an important molecule to be further investigated.

Angiotensin II type-2-receptor stimulation ameliorates focal and segmental glomerulosclerosis in mice

Podocyte damage and loss are the early event in the development of focal segmental glomerulosclerosis (FSGS). Podocytes express angiotensin II type-2-receptor (AT2R), which may play a key role in maintaining kidney integrity and function. Here, we examined the effects of AT2R deletion and AT2R agonist compound 21 (C21) on the evolution of FSGS. FSGS was induced by adriamycin (ADR) injection in both male wild-type (WT) and AT2R knockout (KO) mice. C21 was administered to WT-FSGS mice either one day before or 7 days after ADR (Pre-C21 or Post-C21), using two doses of C21 at either 0.3 (low dose, LD) or 1.0 (high dose, HD) mg/kg/day. ADR-induced FSGS was more severe in AT2RKO mice compared with WT-FSGS mice, and included profound podocyte loss, glomerular fibrosis, and albuminuria. Glomerular cathepsin L expression increased more in AT2RKO-FSGS than in WT-FSGS mice. C21 treatment ameliorated podocyte injury, most significantly in the Pre C21-HD group, and inhibited glomerular cathepsin L expression. In vitro, Agtr2 knock-down in mouse podocyte cell line given ADR confirmed the in vivo data. Mechanistically, C21 inhibited cathepsin L expression, which protected synaptopodin from destruction and stabilized actin cytoskeleton. C21 also prevented podocyte apoptosis. In conclusion, AT2R activation by C21 ameliorated ADR-induced podocyte injury in mice by the inhibition of glomerular cathepsin L leading to the maintenance of podocyte integrity and prevention of podocyte apoptosis.

Nephrotic Syndrome

Nephrotic syndrome (NS) encompasses a variety of disease processes leading to heavy proteinuria and edema. Minimal change disease (MCD) remains the most common primary cause of NS, as well as the most responsive to pharmacologic treatment with often minimal to no chronic kidney disease. Other causes of NS include focal segmental glomerulosclerosis, which follows MCD, and secondary causes, including extrarenal or systemic diseases, infections, and drugs. Although initial diagnosis relies on clinical findings as well as urine and blood chemistries, renal biopsy and genetic testing are important diagnostic tools, especially when considering non-MCD NS. Moreover, biomarkers in urine and serum have become important areas for research in this disease. NS progression and prognosis are variable and depend on etiology, with corticosteroids being the mainstay of treatment. Other alternative therapies found to be successful in inducing and maintaining remission include calcineurin inhibitors and rituximab. Disease course can range from recurrent disease relapse with or without acute kidney injury to end-stage renal disease in some cases. Given the complex pathogenesis of NS, which remains incompletely understood, complications are numerous and diverse and include infections, electrolyte abnormalities, acute kidney injury, and thrombosis. Pediatricians must be aware of the presentation, complications, and overall long-term implications of NS and its treatment.

Focal Segmental Glomerulosclerosis in Paediatric Population of South Punjab Pakistan: A Tertiary Care Hospital Experience

Objectives:

To find out frequency, clinicopathological features, response of treatment and outcome among children with primary focal segmental glomerulosclerosis (FSGS).

Methods:

This retrospective, non-interventional medical charts review study was conducted from a period of January 2011 to January 2020 at Pediatric Department of Nishtar Medical University Hospital, Multan, Pakistan. During the nine years study period, children of both genders, aged less than 16 years, with renal biopsies proven FSGS were included. Patient’s demographic along with clinical and laboratory data, urine dipstick for proteinuria, renal functions, 24 hours urinary protein and ultrasonography findings of kidneys, ureters and bladder (KUB) were noted from case records. Response rates of various treatment options and their outcome like remission, partial remission, no remission with stable kidney disease & no remission with progression of kidney disease were noted.

Results:

During the study duration, out of 307 renal biopsies performed in glomerulonephritis cases, 124 (40.4%) had primary FSGS. In 124 primary FSGS cases, mean age was 8.83±3.05 years while most of the children, 70 (56.5%) were above 10 years of age. Majority of the cases, 64 (51.6%) were male. Mean follow up duration was noted to be 28.35+18.47 months. Most of the cases, 68 (54.8%) were found to have complete remission, 22 (17.7%) partial remission while 11 (8.9%) progressed to ESKD.

Conclusions:

Among children, frequency of primary FSGS was high at our setting. Most of the cases achieved sustained remission rates with the help of immunosuppressive drugs. Cyclosporine and tacrolimus were found to be the most effective drugs.

Emerging drugs for treatment of focal segmental glomerulosclerosis

BACKGROUND

Glomerulosclerosis represents the final stage of glomerular injury during the course of kidney disease and can result from a primary disturbance in disorders like focal segmental glomerulosclerosis or a secondary response to tubulointerstitial disease. Overall, primary focal glomerulosclerosis (FSGS), the focus of this review, accounts for 10-20% of patients of all ages who progress to end stage kidney disease. There are no FDA approved therapeutic options that effectively prevent or delay the onset of kidney failure.

AREAS COVERED

Current immunosuppressive therapy and conservative management including inhibitors of the renin-angiotensin-aldosterone axis and sodium-glucose cotransporter are reviewed. FSGS is now recognized to represent a heterogeneous entity with multiple underlying disease mechanisms. Therefore, novel approaches targeting the podocyte cytoskeleton, immunological, inflammatory, hemodynamic and metabolic pathways are highlighted.

EXPERT OPINION

A number of factors are driving the development of drugs to treat focal segmental glomerulosclerosis in particular and glomerulosclerosis in general including growing awareness of the burden of chronic kidney disease, improved scientific understanding of the mechanism of injury, and the development of noninvasive profiles to identify subgroups of patients with discrete mechanisms of glomerular injury.

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.

Ofatumumab in post-transplantation recurrence of focal segmental glomerulosclerosis in a child

FSGS is a potentially devastating form of nephrotic syndrome. Treatment of SRNS can be difficult, especially post-transplantation. The current therapy of post-transplant SRNS includes plasmapheresis, ACE-I, CNI, and monoclonal antibodies (rituximab). Patients who are refractory to these interventions have limited therapeutic alternatives. We present a case of a patient with SRNS secondary to FSGS. He did not respond to immunosuppressive medications prior to transplant, progressed to ESRD, and was started on chronic hemodialysis. He received a DDKT which was complicated by post-transplant FSGS recurrence. A course of plasmapheresis, rituximab, and CNI were administered with some response. Ofatumumab was then given to the patient. As a result, the patient achieved partial remission. Ofatumumab may be a safe and effective option for post-transplant recurrence of FSGS.

DUET: A Phase 2 Study Evaluating the Efficacy and Safety of Sparsentan in Patients with FSGS

BACKGROUND

We evaluated and compared the effects of sparsentan, a dual endothelin type A (ET_A) and angiotensin II type 1 receptor antagonist, with those of the angiotensin II type 1 receptor antagonist irbesartan in patients with primary FSGS.

METHODS

In this phase 2, randomized, double-blind, active-control Efficacy and Safety of Sparsentan (RE-021), a Dual Endothelin Receptor and Angiotensin Receptor Blocker, in Patients with Focal Segmental Glomerulosclerosis (FSGS): A Randomized, Double-blind, Active-Control, Dose-Escalation Study (DUET), patients aged 8-75 years with biopsy-proven FSGS, eGFR>30 ml/min per 1.73 m², and urinary protein-to-creatinine ratio (UP/C) ≥1.0 g/g received sparsentan (200, 400, or 800 mg/d) or irbesartan (300 mg/d) for 8 weeks, followed by open-label sparsentan only. End points at week 8 were reduction from baseline in UP/C (primary) and proportion of patients achieving FSGS partial remission end point (FPRE) (UP/C: ≤1.5 g/g and >40% reduction [secondary]).

RESULTS

Of 109 patients randomized, 96 received study drugs and had baseline and week 8 UP/C measurements. Sparsentan-treated patients had greater reductions in UP/C than irbesartan-treated patients did when all doses (45% versus 19%; P=0.006) or the 400 and 800 mg doses (47% versus 19%; P=0.01) were pooled for analysis. The FSGS partial remission end point was achieved in 28% of sparsentan-treated and 9% of irbesartan-treated patients (P=0.04). After 8 weeks of treatment, BP was reduced with sparsentan but not irbesartan, and eGFR was stable with both treatments. Overall, the incidence of adverse events was similar between groups. Hypotension and edema were more common among sparsentan-treated patients but did not result in study withdrawals.

CONCLUSIONS

Patients with FSGS achieved significantly greater reductions in proteinuria after 8 weeks of sparsentan versus irbesartan. Sparsentan was safe and well tolerated.

Diagnosis and primary care management of focal segmental glomerulosclerosis in children

Focal segmental glomerulosclerosis (FSGS) is a pattern of kidney damage that can occur in individuals at any age, including children. Pediatric patients with FSGS require medication monitoring, growth, and psychological health. This article discusses the NP's role in the clinical presentation, diagnostic workup, and treatment of FSGS in pediatric patients.

Investigational drugs in development for focal segmental glomerulosclerosis

INTRODUCTION

Focal segmental glomerulosclerosis is an important cause of end stage kidney disease and is a paradigm for the study of glomerular scarring. There are no FDA approved treatments for this condition. Current therapies, assessed based on reduction in proteinuria, are generally effective in a subset of patients which suggests that FSGS is a heterogeneous group of glomerular disorders or podocytopathies that converge on a common histopathological phenotype. Areas covered: We searched for investigational drugs agents that target different pathophysiological pathways using the key words 'FSGS' and 'podocyte' in American and European clinical trial registers (clinicaltrials.gov; clinicaltrialsregister.eu). Published articles were searched in PubMed, Medline, the Web of Science and the Cochrane Central Register of Controlled Trials Library. Expert opinion: Progress is being made in defining the mechanism of action of subtypes of FSGS. Current and investigational therapies for FSGS target these different pathways of injury. It is anticipated that advances in systems biology will further refine the classification of FSGS by subdividing the disease based on the primary mechanism of glomerular injury, identify biomarkers to discriminate between different subtypes, and enable appropriate selection of appropriate therapy for each individual in accordance with the goals of precision medicine.

Role of alpha-lipoic acid in ameliorating Cyclosporine A-induced pancreatic injury in albino rats: A structural, ultrastructural, and morphometric study

The aim of this study was to investigate the effectiveness of alpha-lipoic acid (α-LA) against cyclosporine A (CsA)-induced pancreatic toxicity in rats. Thirty-two male albino rats were divided into four equal groups. Group I treated orally (per os, p.o.) with vehicles and served as control; Group II received α-LA (100 mg/kg b.w. /day, p.o.) for 21 days; Group III received CsA (25 mg/kg b.w./day, p.o.) for 21 days; and Group IV received α-LA 1 hr before oral treatment by CsA for 21 days. Histological examination of the pancreas of CsA-treated rats showed marked changes represented by wide interlobular septae that contained congested blood vessels, cytoplasmic vacuolation of some acinar cells, and distortion of the other cells. Most of the islets of Langerhans showed vacuolation, degenerative changes, and loss of uniform cellular distribution. Some of the islets appeared shrunken with few cells. In the CsA group, the immunohistochemical and morphometric study demonstrated a decrease in the number of insulin-secreting β-cells and also a reduction in islet diameters, with statistically significant difference (p < 0.001 and p = 0.004), respectively, compared with the control group. Ultrastructure of the exocrine and endocrine pancreatic cells of the CsA-treated group confirmed the light microscopic observation and showed dilated rough endoplasmic reticulum, decreased zymogen and secretory granules, damaged mitochondria, and abnormal nuclei. However, α-LA administration simultaneously with CsA resulted in some sort of regression of the previously mentioned effects.

CONCLUSION

α-LA attenuated CsA-induced structural and ultrastructural changes in pancreatic cells, which were nearly reverted to their normal structure.

Focal Segmental Glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is a leading cause of kidney disease worldwide. The presumed etiology of primary FSGS is a plasma factor with responsiveness to immunosuppressive therapy and a risk of recurrence after kidney transplant-important disease characteristics. In contrast, adaptive FSGS is associated with excessive nephron workload due to increased body size, reduced nephron capacity, or single glomerular hyperfiltration associated with certain diseases. Additional etiologies are now recognized as drivers of FSGS: high-penetrance genetic FSGS due to mutations in one of nearly 40 genes, virus-associated FSGS, and medication-associated FSGS. Emerging data support the identification of a sixth category: APOL1 risk allele-associated FSGS in individuals with sub-Saharan ancestry. The classification of a particular patient with FSGS relies on integration of findings from clinical history, laboratory testing, kidney biopsy, and in some patients, genetic testing. The kidney biopsy can be helpful, with clues provided by features on light microscopy (e.g, glomerular size, histologic variant of FSGS, microcystic tubular changes, and tubular hypertrophy), immunofluorescence (e.g, to rule out other primary glomerulopathies), and electron microscopy (e.g., extent of podocyte foot process effacement, podocyte microvillous transformation, and tubuloreticular inclusions). A complete assessment of renal histology is important for establishing the parenchymal setting of segmental glomerulosclerosis, distinguishing FSGS associated with one of many other glomerular diseases from the clinical-pathologic syndrome of FSGS. Genetic testing is beneficial in particular clinical settings. Identifying the etiology of FSGS guides selection of therapy and provides prognostic insight. Much progress has been made in our understanding of FSGS, but important outstanding issues remain, including the identity of the plasma factor believed to be responsible for primary FSGS, the value of routine implementation of genetic testing, and the identification of more effective and less toxic therapeutic interventions for FSGS.

Efficacy and Safety of Sparsentan Compared With Irbesartan in Patients With Primary Focal Segmental Glomerulosclerosis: Randomized, Controlled Trial Design (DUET)

Introduction

Primary focal segmental glomerulosclerosis (FSGS) is a leading cause of nephrotic syndrome and end-stage renal disease. There are no US Food and Drug Administration−approved therapies for FSGS, and treatment often fails to reduce proteinuria. Endothelin is an important factor in the pathophysiology of podocyte disorders, including FSGS. Sparsentan is a first-in-class, orally active, dual-acting angiotensin receptor blocker (ARB) and highly selective endothelin Type A receptor antagonist. This study is designed to evaluate whether sparsentan lowers proteinuria compared with an ARB alone and has a favorable safety profile in patients with FSGS.

Methods

DUET is a phase 2, randomized, active-control, dose-escalation study with an 8-week, fixed-dose, double-blind period followed by 136 weeks of open-label sparsentan treatment. Patients aged 8 to 75 years with primary FSGS will be randomized to treatment with sparsentan or irbesartan for 8 weeks.

Results

The primary efficacy objective is to test the hypothesis that sparsentan over the dose range (200 mg, 400 mg, or 800 mg daily) is superior to irbesartan (300 mg daily) in decreasing the urinary protein-to-creatinine ratio (UPC) from baseline to 8 weeks postrandomization. As secondary objectives, the trial will evaluate the proportion of patients who achieve prespecified targets of UPC reduction, changes in laboratory and quality-of-life indices, and detailed safety analysis. Analyses will be conducted at the end of the double-blind (week 8) and open-label (week 144) periods.

Discussion

This study will provide important evidence on whether dual ARB and endothelin blockade may be an effective therapeutic strategy for FSGS and may provide the rationale for next-phase trials.

Calpain-Mediated Cleavage of Calcineurin in Puromycin Aminonucleoside-Induced Podocyte Injury

The calcineurin inhibitors cyclosporine A (CsA) and tacrolimus are widely used in the treatment of proteinuria diseases. As the direct target of these drugs, calcineurin has previously been demonstrated to play a role in proteinuria diseases. However, aside from its immune-related effects, the local status of calcineurin in renal inherent cells has not been fully explored in the settings of proteinuria disease and podocyte injury. In this study, calcineurin activity and protein expression in the well-known puromycin aminonucleoside (PAN)-induced podocyte injury model were examined. Interestingly, we found that calcineurin activity was abnormally increased in PAN-treated podocytes, whereas the expression of the full-length 60-kDa calcineurin protein was decreased. This result suggests that there may be another activated form of calcineurin that is independent of the full-length phosphatase. To investigate whether calpain is involved in regulating calcineurin, we exposed PAN-treated podocytes to both pharmacological inhibitors of calpain and specific siRNAs against calpain. Calpain blockade reduced the enhanced calcineurin activity and restored the down-regulated expression of 60-kDa calcineurin. In addition, purified calpain protein was incubated with podocyte extracts, and a 45-kDa fragment of calcineurin was identified; this finding was confirmed in PAN-induced podocyte injury and calpain inhibition experiments. We conclude that calcineurin activity is abnormally increased during PAN-induced podocyte injury, whereas the expression of the full-length 60-kDa calcineurin protein is down-regulated due to over-activated calpain that cleaves calcineurin to form a 45-kDa fragment.

Recent Advances in Treatments of Primary Focal Segmental Glomerulosclerosis in Children

Focal segmental glomerulosclerosis (FSGS) is a nephrotic syndrome. Up to around 80% of cases of primary FSGS are resistant to steroid treatment. A large proportion of patients with steroid-resistant FSGS progress to end-stage renal disease. The purpose of treatment is to obtain a complete remission of proteinuria, a necessary step that precedes improved renal survival and reduces the risk of progression to chronic kidney disease. When this is not possible, the secondary goal is a partial remission of proteinuria. Reduction or remission of proteinuria is the most important factor predictive of renal survival. We will review the current updated strategies for treatment of primary FSGS in children, including traditional therapies consisting of corticosteroids and calcineurin inhibitors and novel therapies such as rituximab, abatacept, adalimumab, and fresolimumab.

Efficacy of galactose and adalimumab in patients with resistant focal segmental glomerulosclerosis: report of the font clinical trial group

BACKGROUND

Patients with resistant focal segmental glomerulosclerosis (FSGS) who are unresponsive to corticosteroids and other immunosuppressive agents are at very high risk of progression to end stage kidney disease. In the absence of curative treatment, current therapy centers on renoprotective interventions that reduce proteinuria and fibrosis. The FONT (Novel Therapies for Resistant FSGS) Phase II clinical trial (NCT00814255, Registration date December 22, 2008) was designed to assess the efficacy of adalimumab and galactose compared to standard medical therapy which was comprised of lisinopril, losartan, and atorvastatin.

METHODS

Key eligibility criteria were biopsy confirmed primary FSGS or documentation of a causative genetic mutation, urine protein:creatinine ratio >1.0 g/g, and estimated glomerular filtration rate (eGFR) >40 ml/min/1.73 m(2). The experimental treatments - adalimumab, galactose, standard medical therapy-- were administered for 26 weeks. The primary endpoint was a 50 % reduction in proteinuria with stable eGFR.

RESULTS

Thirty-two subjects were screened and 21 were assigned to one of the three study arms. While none of the adalimumab-treated subjects achieved the primary outcome, 2 subjects in the galactose and 2 in the standard medical therapy arm had a 50 % reduction in proteinuria without a decline in eGFR. The proteinuria response did not correlate with serial changes in the serum glomerular permeability activity measured by the Palb assay or soluble urokinase plasminogen activator receptor (suPAR). There were no serious adverse effects related to treatments in the study.

CONCLUSIONS

Recruitment into this trial that addressed patients with resistant FSGS fell short of the enrollment goal. Our findings suggest that future studies of novel therapies for rare glomerular diseases such as FSGS may benefit from enrollment of patients earlier in the course of their disease. In addition, better identification of patients who are likely to respond to a new treatment based on biomarkers suggesting involvement of the disease pathway targeted by the experimental agent may reduce the required sample size and increase the likelihood of a favorable outcome.

Novel therapies for FSGS: preclinical and clinical studies

Focal segmental glomerulosclerosis (FSGS) is a rare but important cause of end-stage kidney disease in children and adults. Current therapy, consisting of corticosteroids and calcineurin inhibitors, fails to achieve a sustained remission in most patients. Therefore, there is a pressing need to develop new treatments for this glomerulopathy. Traditional approaches have focused on agents that modulate the immune system. In this review, we summarize preclinical and clinical data with newer agents that may ameliorate FSGS. We focus on drugs that inhibit immune injury or inflammation, such as abatacept, rituximab, adalimumab, and stem cells. The potential of agents that block the glomerular action of circulating permeability factors such as soluble urokinase receptor is reviewed. Finally, because fibrosis represents the final common pathway of glomerular damage in FSGS, the experience with a wide range of antifibrotic agents is presented. Despite extensive research on the podocyte dysfunction in the pathogenesis of FSGS, there are few agents that directly target podocyte structure or viability. We conclude that FSGS is a heterogeneous disorder and that intensified translational research is vital to improve our understanding of distinct subtypes that have a defined prognosis and predictable response to targeted therapeutic interventions.

Nephrotic syndrome

On the basis of observational studies, the most common cause of nephrotic syndrome in school-aged children is minimal change disease. On the basis of research evidence and consensus, corticosteroids are considered first-line therapy for treatment of nephrotic syndrome. On the basis of consensus, prednisone therapy should be initiated at doses of 60 mg/m2 per day (2 mg/kg per day) administered for 4 to 6 weeks, followed by 40 mg/m2 per dose (1.5 mg/kg) every other day for at least 6 to 8 weeks. On the basis of consensus and expert opinion, it is important to recognize and manage the complications that can arise in patients with nephrotic syndrome, such as dyslipidemia, infection, and thrombosis. On the basis of research evidence, consensus, and expert opinion, several alternative therapies have been observed to have variable efficacy in children with both corticosteroid-dependent and corticosteroid-resistant nephrotic syndrome, although caution must be exercised in the administration of these corticosteroid-sparing medications secondary to toxic adverse effects. On the basis of observational studies, the course of nephrotic syndrome in most patients is that of relapse and remission.