[Role of Complement in Kidney Diseases - New Aspects]. / Die Rolle des Komplementsystems bei Nierenerkrankungen ­ Neue Aspekte.

Complement is a central part of the immune system. In the human body, complement is responsible for recognition of infectious microbes, for coordinating the adaptive immune response, controlling homeotic reactions and for the non-inflammatory removal of modified self-cells and infectious microbes. Complement is also closely linked to another proteolytic cascade, the coagulation system. Defective activation and altered complement regulation drives pathology of several severe human kidney diseases.This manuscript summarizes the latest developments on the role of complement in kidney diseases, on new complement inhibitors and on recent complement targeting therapies. In particular focusing on diseases (1) atypical Hemolytic Uremic Syndrome, (2) C3 Glomerulopathy, (3) Anti Neutrophil Cytoplasmic Antibody Mediated Vasculitis, (4) IgA Nephropathy, (5) Membranous Glomerulopathy, (6) Systemic Lupus Erythematosus, (7) Transplant rejection and (8) COVID 19 Infection-Triggered Kidney Diseases. More excitement is generated in this field, as more and more complement mediated diseases can be treated. Several complement targeting compounds are approved by the EMA and FDA and an increasing number of new candidates are in late phase clinical trials. In addition, clinical guidelines are developed for Diagnosis and Therapy of complement mediated diseases, new biomarkers are evaluated in clinical studies, and diagnostic guidelines are in development. The recent Covid infections showed a clear link of complement in thrombo inflammation, which ultimately results in kidney damage. These aspects have increased further the focus of complement inhibitors in COVID infections.

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

BACKGROUND: Sparsentan is a novel, non-immunosuppressive, single-molecule, dual endothelin and angiotensin receptor antagonist being examined in an ongoing phase 3 trial in adults with IgA nephropathy. We report the prespecified interim analysis of the primary proteinuria efficacy endpoint, and safety. METHODS: PROTECT is an international, randomised, double-blind, active-controlled study, being conducted in 134 clinical practice sites in 18 countries. The study examines sparsentan versus irbesartan in adults (aged ≥18 years) with biopsy-proven IgA nephropathy and proteinuria of 1·0 g/day or higher despite maximised renin-angiotensin system inhibitor treatment for at least 12 weeks. Participants were randomly assigned in a 1:1 ratio to receive sparsentan 400 mg once daily or irbesartan 300 mg once daily, stratified by estimated glomerular filtration rate at screening (30 to <60 mL/min per 1·73 m2 and ≥60 mL/min per 1·73 m2) and urine protein excretion at screening (≤1·75 g/day and >1·75 g/day). The primary efficacy endpoint was change from baseline to week 36 in urine protein-creatinine ratio based on a 24-h urine sample, assessed using mixed model repeated measures. Treatment-emergent adverse events (TEAEs) were safety endpoints. All endpoints were examined in all participants who received at least one dose of randomised treatment. The study is ongoing and is registered with ClinicalTrials.gov, NCT03762850. FINDINGS: Between Dec 20, 2018, and May 26, 2021, 404 participants were randomly assigned to sparsentan (n=202) or irbesartan (n=202) and received treatment. At week 36, the geometric least squares mean percent change from baseline in urine protein-creatinine ratio was statistically significantly greater in the sparsentan group (-49·8%) than the irbesartan group (-15·1%), resulting in a between-group relative reduction of 41% (least squares mean ratio=0·59; 95% CI 0·51-0·69; p<0·0001). TEAEs with sparsentan were similar to irbesartan. There were no cases of severe oedema, heart failure, hepatotoxicity, or oedema-related discontinuations. Bodyweight changes from baseline were not different between the sparsentan and irbesartan groups. INTERPRETATION: Once-daily treatment with sparsentan produced meaningful reduction in proteinuria compared with irbesartan in adults with IgA nephropathy. Safety of sparsentan was similar to irbesartan. Future analyses after completion of the 2-year double-blind period will show whether these beneficial effects translate into a long-term nephroprotective potential of sparsentan. FUNDING: Travere Therapeutics.

New insights into the mucosal immune pathogenesis of IgA nephropathy from the perspective of COVID-19 vaccination.

Large-scale SARS-CoV-2 vaccination is one of the key strategies to curb the COVID-19 pandemic; however, there are increasing reports of IgA nephropathy following COVID-19 vaccination. The clinical manifestation, treatment and prognostic effects are different in IgAN patients who have had an onset after the first and second dose of vaccination, as well as new and recurrent IgAN patients. These conditions bring about a relatively important window for understanding the pathogenesis of IgAN. Gd-IgA1 is the core of the pathogenesis of IgAN. Most IgA is produced at mucosal sites; however, antigen-activated Toll-like receptor activation pathways expressed by antigen-presenting cells and B-cell homing receptors are different in the intestinal and respiratory mucosa, and the link between respiratory and intestinal mucosa is not well understood in the pathogenesis of IgAN. Budesonide treatment of IgAN is thought to inhibit the intestinal immune response by binding to glucocorticoid receptors in the intestinal mucosa or submucosa; however, it is unclear whether there is a therapeutic effect in respiratory mucosa-derived IgA nephropathy. The present review firstly described the relationship between the gut and respiratory mucosa, and the differences in antigen-presenting cell activation pathways and B-cell homing from the perspective of COVID-19 vaccines.

Treatment of Rare Inflammatory Kidney Diseases: Drugs Targeting the Terminal Complement Pathway.

The complement system comprises the frontline of the innate immune system. Triggered by pathogenic surface patterns in different pathways, the cascade concludes with the formation of a membrane attack complex (MAC; complement components C5b to C9) and C5a, a potent anaphylatoxin that elicits various inflammatory signals through binding to C5a receptor 1 (C5aR1). Despite its important role in pathogen elimination, priming and recruitment of myeloid cells from the immune system, as well as crosstalk with other physiological systems, inadvertent activation of the complement system can result in self-attack and overreaction in autoinflammatory diseases. Consequently, it constitutes an interesting target for specialized therapies. The paradigm of safe and efficacious terminal complement pathway inhibition has been demonstrated by the approval of eculizumab in paroxysmal nocturnal hematuria. In addition, complement contribution in rare kidney diseases, such as lupus nephritis, IgA nephropathy, atypical hemolytic uremic syndrome, C3 glomerulopathy, or antineutrophil cytoplasmic antibody-associated vasculitis has been demonstrated. This review summarizes the involvement of the terminal effector agents of the complement system in these diseases and provides an overview of inhibitors for complement components C5, C5a, C5aR1, and MAC that are currently in clinical development. Furthermore, a link between increased complement activity and lung damage in severe COVID-19 patients is discussed and the potential for use of complement inhibitors in COVID-19 is presented.

Hydroxychloroquine safety: A meta-analysis of randomized controlled trials.

BACKGROUND: Hydroxychloroquine (HCQ) is currently being examined for COVID-19. No previous meta-analysis has evaluated its side effects versus placebo. We conducted this meta-analysis to compare the safety of HCQ versus placebo. METHODS: Two authors independently searched PubMed and EMBASE databases for randomized controlled trials (RCTs) of adults comparing the adverse events (AEs) of HCQ versus placebo for any indication. Peto odds ratios (Peto ORs) and 95% confidence intervals (CIs) were calculated based on random-effects models. The heterogeneity (I2) was assessed using Cochran's Q test. RESULTS: Nine RCTs (eight were double-blind) with a total of 916 patients were included. HCQ caused significantly more skin pigmentation than placebo (Peto OR, 4.64; 95% CI, 1.13 to 19.00; P-value = 0.033; I2 = 0%). The increase in other AEs did not reach statistical significance: rash (Peto OR, 1.11; 95% CI, 0.3 to 3.77; P-value = 0.03; I2 = 0%); gastrointestinal AEs (Peto OR, 1.43; 95% CI, 0.55 to 3.72; P-value = 0.46; I2 = 15.17%); headache (Peto OR, 1.94; 95% CI, 0.65 to 5.78; P-value = 0.23; I2 = 9.99%); dizziness (Peto OR, 1.32; 95% CI, 0.49 to 3.52; P-value = 0.58; I2 = 0%); fatigue (Peto OR, 2.13; 95% CI, 0.76 to 5.98; P-value = 0.15; I2 = 0%); and visual AEs (Peto OR, 1.61; 95% CI, 0.76 to 3.41; P-value = 0.22; I2 = 0%). Cardiac toxicity was not reported. CONCLUSIONS: This meta-analysis of RCTs found a significantly higher risk of skin pigmentation in HCQ users versus placebo. More data are needed to evaluate HCQ in the context of COVID-19 treatment.