Sparsentan (RE-021; BMS-346567; PS433540; DARA-a) is a novel candidate in development by Retrophin for the treatment of focal segmental glomerulosclerosis (FSGS), a serious kidney disorder that often leads to end-stage renal disease (ESRD). Sparsentan is a first-in-class, orally active, dual-acting angiotensin receptor blocker (ARB) and highly selective endothelin Type A receptor antagonist. Sparsentan has been used in trials studying the treatment of focal segmental glomerulosclerosis. The FDA and European Commission have granted sparsentan orphan drug designation for FSGS. Retrophin also is advancing sparsentan for the treatment of immunoglobulin A nephropathy (IgAN) , or Berger’s disease, which also can lead to ESRD. Retrophin is examining the ability of sparsentan to slow the decline of kidney function in patients with FSGS and IgAN.