Disease-Specific Treatment For Primary Membranous Nephropathy: The Role of Monoclonal Antibodies

Abstract

Primary Membranous Nephropathy is an autoimmune disease caused by the deposition of Immunoglobulin G and complement components on the subepithelial layer of the glomerular capillary wall. It affects 5-10 patients per million population and is the second cause of nephrotic syndrome in adults after diabetic kidney disease. For decades steroids and non-specific immunosuppressive medications have been advocated as a therapeutic option for patients with membranous nephropathy at increased risk of kidney failure because of persistent nephrotic syndrome. These medications, however, have major and potentially fatal adverse effects that offset their potential benefits and should be abandoned. The discovery of nephritogenic autoantibodies against podocyte M-type phospholipase A2 receptor (PLA2R) and thrombospondin type-1 domain-containing protein 7A (THSD7A) antigens provided a clear pathophysiological rationale for interventions specifically targeting B cell lineages to prevent antibody production and subepithelial deposition. The first-in-class anti-CD20 monoclonal antibody rituximab is safe and achieves remission in approximately two-thirds of patients with nephrotic membranous nephropathy. In PLA2R-related disease, remission is invariably preceded by depletion of anti PLA2R autoantibodies and relapse by their re-emergence into the circulation. Because of its superior risk/benefit profile as compared to non-specific immunosuppressive therapy, rituximab is now first-line therapy for patients with membranous nephropathy at risk of kidney failure. Novel monoclonal antibodies targeting CD20 cells (such as ofatumumab and obinutuzumab) and their differentiation (belimumab) or targeting long-living antibody producing CD38 memory cells (daratumumab, felzartamab) along with proteasome inhibitors such as bortezomib are being evaluated for the treatment of nephrotic patients with membranous nephropathy who are resistant or intolerant to rituximab. Complement inhibitor therapy might serve to stop the glomerular inflammatory process until the benefits of these medications become effective. Thus, major advances in the understanding of the mechanisms of membranous nephropathy have led to novel treatment perspectives. The integrated evaluation of serum autoantibody titer and proteinuria, together with serum albumin levels in patients with overt nephrotic syndrome, could guide diagnosis of membranous nephropathy and individually tailored treatment protocols. The introduction of monoclonal antibodies targeting disease-specific mechanisms will pave the way for a novel therapeutic paradigm based on the principle of precision medicine and personalized therapy.