Complement inhibitors for kidney disease

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.

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.

Urine complement proteins are associated with kidney disease progression of type 2 diabetes in Korean and American cohorts

Background

Mechanisms of progression of diabetic kidney disease (DKD) are not completely understood. This study uses untargeted and targeted mass spectrometry-based proteomics in two independent cohorts on two continents to decipher the mechanisms of DKD in patients with type 2 diabetes.

Methods

We conducted untargeted mass spectrometry on urine samples collected at the time of kidney biopsy from Korean patients with type 2 diabetes and biopsy-proven diabetic nephropathy at Seoul National University Hospital (SNUH-DN cohort; n = 64). These findings were validated using targeted mass spectrometry in urine samples from a Chronic Renal Insufficiency Cohort subgroup with type 2 diabetes and DKD (CRIC-T2D; n = 282). Urinary biomarkers/pathways associated with kidney disease progression (doubling of serum creatinine, ≥50% decrease in estimated glomerular filtration rates, or the development of end-stage kidney disease) were identified.

Results

SNUH-DN patients had an estimated glomerular filtration rate (eGFR) of 55 mL/min/1.73 m 2 (interquartile range [IQR], 44-75) and random urine protein-to-creatinine ratio of 3.1 g/g (IQR, 1.7-7.0). Urine proteins clustered into two groups, with cluster 2 having a 4.6-fold greater hazard (95% confidence interval [CI], 1.9-11.5) of disease progression than cluster 1 in multivariable-adjusted, time-to-event analyses. Proteins in cluster 2 mapped to 10 pathways, four of the top five of which were complement or complement-related. A high complement score, constructed from urine complement protein abundance, was strongly correlated to 4 of 5 histopathologic DN features and was associated with a 2.4-fold greater hazard (95% CI, 1.0-5.4) of disease progression than a low complement score. Targeted mass spectrometry of the CRIC-T2D participants, who had an eGFR of 42 mL/min/1.73 m 2 (IQR, 37-49) and 24-hr urine protein of 0.48 g (IQR, 0.10-1.87), showed that the complement score similarly segregated them into rapid and slow DKD progression groups. In both cohorts, the complement score had a linear association with disease progression.

Conclusions

Urinary proteomic profiling confirms the association between the complement pathway and rapid DKD progression in two independent cohorts. These results suggest a need to further investigate complement pathway inhibition as a novel treatment for DKD.

Urinary complement biomarkers in immune-mediated kidney diseases

The complement system, an important part of the innate system, is known to play a central role in many immune mediated kidney diseases. All parts of the complement system including the classical, alternative, and mannose-binding lectin pathways have been implicated in complement-mediated kidney injury. Although complement components are thought to be mainly synthesized in the liver and activated in the circulation, emerging data suggest that complement is synthesized and activated inside the kidney leading to direct injury. Urinary complement biomarkers are likely a better reflection of inflammation within the kidneys as compared to traditional serum complement biomarkers which may be influenced by systemic inflammation. In addition, urinary complement biomarkers have the advantage of being non-invasive and easily accessible. With the rise of therapies targeting the complement pathways, there is a critical need to better understand the role of complement in kidney diseases and to develop reliable and non-invasive biomarkers to assess disease activity, predict treatment response and guide therapeutic interventions. In this review, we summarized the current knowledge on urinary complement biomarkers of kidney diseases due to immune complex deposition (lupus nephritis, primary membranous nephropathy, IgA nephropathy) and due to activation of the alternative pathway (C3 glomerulopathy, thrombotic microangiography, ANCA-associated vasculitis). We also address the limitations of current research and propose future directions for the discovery of urinary complement biomarkers.

Improving Kidney Disease Care: One Giant Leap for Nephrology

Nephrology is an ever-evolving field of medicine. The importance of such a discipline is related to the high clinical impact of kidney disease. In fact, abnormalities of kidney function and/or structure are common in the general population, reaching an overall prevalence of about 10%. More importantly, the onset of kidney damage is related to a strikingly high risk of cardiovascular events, mortality, and progression to kidney failure which, in turn, compromises quality and duration of life. Attempts to comprehend the pathogenesis and molecular mechanisms involved in kidney disease occurrence have prompted the development and implementation of novel drugs in clinical practice with the aim of treating the 'specific cause' of kidney disease (including chronic kidney disease, glomerular disease, and genetic kidney disorders) and the main immunological complications following kidney transplantation. Herein, we provide an overview of the principal emerging drug classes with proved efficacy in the context of the aforementioned clinical conditions. This can represent a simplified guide for clinical nephrologists to remind them of the vast and heterogeneous armamentarium of drugs that should be used in the present and the future to improve the management of patients suffering from kidney disease.

mRNA-LNP COVID-19 Vaccine Lipids Induce Complement Activation and Production of Proinflammatory Cytokines: Mechanisms, Effects of Complement Inhibitors, and Relevance to Adverse Reactions

A small fraction of people vaccinated with mRNA-lipid nanoparticle (mRNA-LNP)-based COVID-19 vaccines display acute or subacute inflammatory symptoms whose mechanism has not been clarified to date. To better understand the molecular mechanism of these adverse events (AEs), here, we analyzed in vitro the vaccine-induced induction and interrelations of the following two major inflammatory processes: complement (C) activation and release of proinflammatory cytokines. Incubation of Pfizer-BioNTech's Comirnaty and Moderna's Spikevax with 75% human serum led to significant increases in C5a, sC5b-9, and Bb but not C4d, indicating C activation mainly via the alternative pathway. Control PEGylated liposomes (Doxebo) also induced C activation, but, on a weight basis, it was ~5 times less effective than that of Comirnaty. Viral or synthetic naked mRNAs had no C-activating effects. In peripheral blood mononuclear cell (PBMC) cultures supplemented with 20% autologous serum, besides C activation, Comirnaty induced the secretion of proinflammatory cytokines in the following order: IL-1α < IFN-γ < IL-1β < TNF-α < IL-6 < IL-8. Heat-inactivation of C in serum prevented a rise in IL-1α, IL-1β, and TNF-α, suggesting C-dependence of these cytokines' induction, although the C5 blocker Soliris and C1 inhibitor Berinert, which effectively inhibited C activation in both systems, did not suppress the release of any cytokines. These findings suggest that the inflammatory AEs of mRNA-LNP vaccines are due, at least in part, to stimulation of both arms of the innate immune system, whereupon C activation may be causally involved in the induction of some, but not all, inflammatory cytokines. Thus, the pharmacological attenuation of inflammatory AEs may not be achieved via monotherapy with the tested C inhibitors; efficacy may require combination therapy with different C inhibitors and/or other anti-inflammatory agents.

Cadmium-associated protein changes in residents of contaminated areas: Abandoned mine and smelter

Cadmium (Cd), a serious environmental contaminant, is associated with adverse health effects. However, the specific changes that the human body experiences in response to exposure to varying concentrations of cadmium remain unknown. The high levels of heavy metal contamination, especially Cd, in abandoned mines and smelter sites make them ideal locations to investigate the physiological manifestations of Cd exposure. This study found that individuals inhabiting abandoned mine and smelter areas had higher concentrations of Cd in their urine and blood compared to those living outside these areas (i.e., the controls). Furthermore, proteomic profiling of blood samples from all study groups was performed to identify proteomic biomarkers associated with chronic and severe Cd exposure. This analysis showed statistically significant correlations between urine Cd levels and sixteen proteins. Among these proteins, seven exhibited significantly altered expressions in samples from contaminated areas compared with those from control areas. Therefore, these proteins were selected as potential markers representing Cd-related protein alterations. Multiple reaction monitoring analysis was performed to validate the expression patterns of the proteins and four proteins were found to exhibit consistent trends. The findings show that Cd exposure significantly affects the expression of certain proteins in the human body. Understanding the underlying mechanisms and diseases associated with Cd-induced protein alterations can aid in the development of effective preventive and therapeutic strategies for individuals exposed to Cd-linked pollution.

C3 glomerulopathy in a patient with a history of post-infectious glomerulonephritis

Post-infectious glomerulonephritis (PIGN) is an immune complex mediated glomerular injury occurring because of an infection, most commonly with group A beta-hemolytic streptococcus in children. C3 glomerulopathy (C3G) is a distinct clinicopathological entity occurring secondary to dysregulation of alternate complement pathway encompassing both C3 glomerulonephritis (C3GN) and dense deposit disease (DDD). While most patients with PIGN attain complete remission with normalized complement levels by 6-8 weeks after presentation, patients with C3G continue to have hypocomplementemia with high rates of progressive kidney disease. Here, we report a patient diagnosed with dense deposit disease after his initial presentation with PIGN three years prior. While current literature continues to explore the overlapping and distinguishing features of PIGN and C3G, including how underlying defects in the alternate complement pathway may commonly contribute to both diseases, this case further exemplifies the importance of recognizing the clinico-pathogenic features of PIGN and C3G in pediatric patients with glomerulonephritis.

The role of anticomplement therapy in the management of the kidney allograft

As the number of patients living with kidney failure grows, the need also grows for kidney transplantation, the gold standard kidney replacement therapy that provides a survival advantage. This may result in an increased rate of transplantation from HLA-mismatched donors that increases the rate of antibody-mediated rejection (AMR), which already is the leading cause of allograft failure. Plasmapheresis, intravenous immunoglobulin therapy, anti-CD20 therapies (i.e., rituximab), bortezomib and splenectomy have been used over the years to treat AMR as well as to prevent AMR in high-risk sensitized kidney transplant recipients. Eculizumab and ravulizumab are monoclonal antibodies targeting the C5 protein of the complement pathway and part of the expanding field of anticomplement therapies, which is not limited to kidney transplant recipients, and also includes complement-mediated microangiopathic hemolytic anemia, paroxysmal nocturnal hemoglobinuria, and ANCA-vasculitis. In this narrative review, we summarize the current knowledge concerning the pathophysiological background and use of anti-C5 strategies (eculizumab and ravulizumab) and C1-esterase inhibitor in AMR, either to prevent AMR in high-risk desensitized patients or to treat AMR as first-line or rescue therapy and also to treat de novo thrombotic microangiopathy in kidney transplant recipients.

Microangiopathy associated with poor outcome of immunoglobulin A nephropathy: a cohort study and meta-analysis

Background

Microangiopathy (MA) lesions are not rare in immunoglobulin A nephropathy (IgAN) and have been suggested to have a potential role in increasing risk in renal function decline. However, this suggestion has not been universally accepted. We aimed to investigate its role in our cohort and in multiple studies through a systematic meta-analysis.

Methods

This cohort study included 450 IgAN patients, confirmed by renal biopsy, at Tongji Hospital, China, from January 2012 to December 2016. Clinical data were collected and analysed. We systematically searched PubMed and Web of Science for studies investigating the association between MA lesions and IgAN.

Results

In our cohort, IgAN patients with MA were significantly older and had higher blood pressure, more proteinuria, worse kidney function and increased uric acid levels compared with patients without MA. When comparing pathological features with the non-MA group, the MA group exhibited more global glomerulosclerosis and interstitial fibrosis/tubular atrophy. MA lesions were independently associated with a composite kidney outcome in IgAN patients {adjusted hazard ratio 2.115 [95% confidence interval (CI) 1.035-4.320], P = .040}. Furthermore, this relationship was validated in a meta-analysis involving 2098 individuals from five independent cohorts. The combined data showed a 187% adjusted risk of poor renal outcome in IgAN patients with MA compared with patients without MA [adjusted risk ratio 2.87 (95% CI 2.05-4.02; I2 = 53%).

Conclusion

MA lesions could serve as a valuable predictor for disease progression in patients with IgAN, extending beyond the widely recognized Oxford MEST-C score.

C3G and Ig-MPGN-treatment standard

Among the broad spectrum of membranoproliferative glomerulonephritis (MPGN), immunofluorescence distinguishes C3 glomerulopathy (C3G), with predominant C3 deposits, and immunoglobulin-associated MPGN (Ig-MPGN), with combined C3 and Ig. However, there are several intersections between C3G and Ig-MPGN. Primary C3G and Ig-MPGN share the same prevalence of low serum C3 levels and of abnormalities of the alternative pathway of complement, and patients who present a bioptic pattern of Ig-MPGN at onset may show a C3G pattern in a subsequent biopsy. There is no specific therapy for primary C3G and Ig-MPGN and prognosis is unfavourable. The only recommended indications are inhibitors of the renin-angiotensin system, lipid-lowering agents and other renoprotective agents. The other drugs used currently, such as corticosteroids and mycophenolate mofetil, are often ineffective. The anti-C5 monoclonal antibody eculizumab has been tested in several patients, with mixed results. One reason for the uncertainty is the extremely variable clinical course, most likely reflecting a heterogeneous pathogenesis. An unsupervised clustering analysis that included histologic, biochemical, genetic and clinical data available at onset in patients with primary C3G and Ig-MPGN identified four clusters characterized by specific pathogenic mechanisms. This approach may facilitate accurate diagnosis and development of targeted therapies. Several trials are ongoing with drugs targeting different molecules of the complement cascade, however it is important to consider which component of the cascade may be the most appropriate for each patient. We review the current standards of treatment and discuss novel developments in the pathophysiology, diagnosis, outcome prediction and management of C3G and Ig-MPGN.

Complement System and the Kidney: Its Role in Renal Diseases, Kidney Transplantation and Renal Cell Carcinoma

The crosstalk among the complement system, immune cells, and mediators of inflammation provides an efficient mechanism to protect the organism against infections and support the repair of damaged tissues. Alterations in this complex machinery play a role in the pathogenesis of different diseases. Core complement proteins C3 and C5, their activation fragments, their receptors, and their regulators have been shown to be active intracellularly as the complosome. The kidney is particularly vulnerable to complement-induced damage, and emerging findings have revealed the role of complement system dysregulation in a wide range of kidney disorders, including glomerulopathies and ischemia-reperfusion injury during kidney transplantation. Different studies have shown that activation of the complement system is an important component of tumorigenesis and its elements have been proved to be present in the TME of various human malignancies. The role of the complement system in renal cell carcinoma (RCC) has been recently explored. Clear cell and papillary RCC upregulate most of the complement genes relative to normal kidney tissue. The aim of this narrative review is to provide novel insights into the role of complement in kidney disorders.

Role of perivascular cells in kidney homeostasis, inflammation, repair and fibrosis

Perivascular niches in the kidney comprise heterogeneous cell populations, including pericytes and fibroblasts, with distinct functions. These perivascular cells have crucial roles in preserving kidney homeostasis as they maintain microvascular networks by stabilizing the vasculature and regulating capillary constriction. A subset of kidney perivascular cells can also produce and secrete erythropoietin; this ability can be enhanced with hypoxia-inducible factor-prolyl hydroxylase inhibitors, which are used to treat anaemia in chronic kidney disease. In the pathophysiological state, kidney perivascular cells contribute to the progression of kidney fibrosis, partly via transdifferentiation into myofibroblasts. Moreover, perivascular cells are now recognized as major innate immune sentinels in the kidney that produce pro-inflammatory cytokines and chemokines following injury. These mediators promote immune cell infiltration, leading to persistent inflammation and progression of kidney fibrosis. The crosstalk between perivascular cells and tubular epithelial, immune and endothelial cells is therefore a key process in physiological and pathophysiological states. Here, we examine the multiple roles of kidney perivascular cells in health and disease, focusing on the latest advances in this field of research.