Sparsentan, a Dual Endothelin Type A and Angiotensin II Subtype 1 Receptor Antagonist for the Treatment of Immunoglobulin A Nephropathy: Latest Trial Results, Pharmacokinetic Considerations, and Binding Profile

Immunoglobulin A nephropathy (IgAN) is one of the most common forms of primary glomerulonephritis. In some patients, it can progress rapidly, leading to proteinuria, kidney failure, and death. Standard of care is traditionally with an angiotensin converting enzyme inhibitor (ACEi), or an angiotensin II (Ang II) receptor blocker (ARB). More recently, drugs targeting both endothelin 1 (ET-1) and Ang II receptors have been developed, as overactivation of such is implicated in IgAN. Sparsentan is a dual ET Type A (ETAR) and Ang II subtype 1 receptor (AT1R) antagonist. The PROTECT study compared sparsentan with the ARB irbesartan, in patients with IgAN and with proteinuria of ≥1 g/day despite stable dose of ACEi/ARB for ≥90 days. Data presented at the 2023 American Society of Nephrology (ASN) Kidney Week showed that use of sparsentan led to sustained (>110 weeks) decreases in proteinuria, and a significantly greater preservation of kidney function, compared with irbesartan. The ongoing SPARTAN study is investigating the use of sparsentan in recently diagnosed, treatment-naïve patients with IgAN. Preliminary data in 12 patients showed rapid and sustained proteinuria reductions, with little change from baseline in estimated glomerular filtration rate (eGFR), body weight, or total body water mean at Week 36. In both studies, sparsentan was generally well-tolerated with, in PROTECT, a comparable safety profile to irbesartan. Data presented at the congress also showed that sparsentan consistently occupies AT1R at levels exceeding ETAR occupancy. This balance is hypothesised to contribute to sparsentan’s limited risk of fluid retention.