Nephrotic Syndrome Due to Idiopathic Membranous Nephropathy

Nephrotic syndrome is a kidney condition that mainly affects children and is characterized by high levels of protein in the urine, low levels of protein in the blood, and swelling. While many children respond well to steroid treatment, a large proportion experience relapses or become dependent on therapy. In some cases, the disease does not respond to standard treatments and may progress to chronic kidney disease. Recent research suggests that, in addition to genetic factors, immune system mechanisms may play a key role in the development and progression of nephrotic syndrome. In particular, some patients produce autoantibodies against nephrin, an essential protein of the kidney filtration barrier. These autoantibodies may be associated with disease activity and treatment response. The aim of this study is to investigate the presence of anti-nephrin autoantibodies in children with nephrotic syndrome and to better understand their role in disease mechanisms and clinical outcomes.The study will also explore the presence of other autoantibodies targeting components of the glomerular filtration barrier. The study will use advanced laboratory techniques, including blood tests and detailed analysis of kidney biopsy samples, to identify these antibodies and their relationship with kidney structure and function. By integrating laboratory findings with clinical data, this study aims to improve the understanding of nephrotic syndrome and support the development of more personalized diagnostic and therapeutic strategies, with the goal of improving patient outcomes and reducing unnecessary or ineffective treatments.

This study is an exploratory, randomized, double-blind, multicenter, placebo-controlled study with repeated doses of AP1189. The study population will consist of patients with idiopathic membranous nephropathy (iMN) and severe proteinuria who are on ACE inhibitor or angiotensin II receptor blocker treatment.