#272 Sparsentan reduces glomerular dysfunction and proteinuria in a rat model of serum-factor-induced nephrotic syndrome

Abstract Background and Aims Glomerular function is dependent on the three-layer structure of the glomerular filtration barrier (GFB): glomerular endothelial cells and their surface glycocalyx, the glomerular basement membrane and podocytes. Proteinuric kidney diseases are associated with glomerular dysfunction and loss of barrier integrity. Sparsentan is a single-molecule dual endothelin type-A and angiotensin II type 1 receptor antagonist (DEARA) that has received approval in the United States and European Union for the reduction of proteinuria in adults with IgA nephropathy and is under clinical development for FSGS. Using a model of targeted podocyte injury to induce proteinuria, we sought to determine whether sparsentan could prevent the development of proteinuria, by maintaining the GFB. Method Female Lewis rats were given vehicle or sparsentan daily (60 mg/kg or 120 mg/kg, p.o.) from day 0, until sacrifice at day 8. At day 1, mAb 5-1-6 (rat anti-nephrin antibody) was injected (33 mg/kg, i.v.) to induce proteinuria. Ringer perfused kidneys were processed for immunofluorescence and glomeruli were isolated to directly measure albumin permeability (Ps’alb) within individually trapped glomeruli using our validated assay [1]. Urine was collected to analyse urinary albumin: creatinine ratios (uACR). Blood pressure was measured using a tail cuff method. Results In mAb 5-1-6 treated rats, uACR and Ps’alb (expressed as means (±SEM)) were significantly increased compared to control rats (uACR: control, 20 ± 3 mg/mmol; vehicle + mAb 5-1-6, 5,304 ± 986 mg/mmol, P < 0.0001; Ps’alb: control, 6.2 x 10−7 ± 0.2 x 10−7 cm/s; vehicle + mAb 5-1-6, 10.1 x 10−7 ± 0.4 x 10−7 cm/s, P < 0.0001). Sparsentan-treatment of mAb 5-1-6 rats resulted in a significant dose-dependent reduction in uACR and Ps’alb (uACR: sparsentan (60mg/kg) + mAb 5-1-6, 1,410 ± 424 mg/mmol, P < 0.0001; sparsentan (120 mg/kg) + mAb 5-1-6, 1,028 ± 269 mg/mmol, P < 0.0001; Ps’alb: sparsentan (60 mg/kg) + mAb 5-1-6, 8.2 x 10−7 ± 0.3 x 10−7 cm/s, P = 0.0026; sparsentan (120 mg/kg) + mAb 5-1-6, 7.7 x 10−7 ± 0.3 x 10−7 cm/s, P = 0.0002). Nephrin staining in mAb 5-1-6 rats changed from a typical linear pattern to a punctate pattern, and staining intensity was decreased—this change was prevented with sparsentan treatment. These observations were independent of changes in blood pressure and body weight. Conclusion We have shown that the DEARA sparsentan, reduces glomerular permeability and proteinuria in a rat model of serum factor-induced podocytopathy. These findings suggest that the action of sparsentan on the GFB could help maintain barrier integrity in podocytopathic proteinuric kidney diseases. This work was funded by Travere Therapeutics, Inc.