Sparsentan is a novel candidate in development for the treatment of focal segmental glomerulosclerosis (FSGS) , a serious kidney disorder that often leads to end-stage renal disease (ESRD). 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.
FSGS is estimated to affect up to 40,000 patients in the U.S., with a similar prevalence in Europe. FSGS is characterized by proteinuria, protein found in the urine due to a breakdown of the normal filtration mechanism in the kidney. Most often, the cause of the disorder is unknown, or “idiopathic”, but it can also be genetic. Less frequently, FSGS is associated with other conditions such as kidney defects from birth (dysplasia), urine backing up into kidneys (kidney reflux), obesity, sleep apnea, viruses, blood disorders and autoimmune disorders. There is no indicated treatment for FSGS. Learn more about FSGS .
IgAN , or Berger’s disease, is estimated to affect more than 100,000 people in the United States and greater numbers in Europe and Asia. The disease is caused by deposits of immunoglobulin A (IgA) in the kidney, which leads to hematuria (blood in the urine), proteinuria (protein in the urine) and progressive kidney failure. There is no indicated treatment for IgAN. Learn more about IgAN .
Sparsentan is a therapeutic candidate for the treatment of FSGS and IgAN. The investigational candidate is designed to be a dual acting angiotensin receptor blocker and endothelin receptor antagonist. Proteinuria, characteristic of both FSGS and IgAN, is seen as a marker of kidney function; lower proteinuria levels are associated with better outcomes. Our investigational approach is to attempt to lower proteinuria levels with sparsentan.
Sparsentan for FSGS
After completing the successful Phase 2 DUET Study, Retrophin initiated a global pivotal Phase 3 clinical trial in 2018 to support potential approval of sparsentan for patients with FSGS in the U.S. and Europe. The DUPLEX Study protocol provides for an unblinded analysis of at least 190 patients performed after 36 weeks of treatment to evaluate the interim efficacy endpoint – the proportion of patients achieving partial remission of proteinuria. The data from this analysis are expected to serve as the basis for submission of a New Drug Application under the Subpart H accelerated approval pathway in the U.S. and Conditional Marketing Authorization in Europe. Top-line efficacy data from the 36-week interim efficacy endpoint are expected in the first half of 2021. The confirmatory endpoint of the DUPLEX Study is the slope of eGFR assessed from week 6 to week 108 at the final analysis.
Sparsentan for IgAN
In 2018, we also initiated the PROTECT Study, a global pivotal Phase 3 clinical trial evaluating the safety and efficacy of sparsentan in patients with IgAN. The primary efficacy endpoint of the PROTECT Study is the change in proteinuria from baseline after 36 weeks of treatment. The study is expected to support submission of a New Drug Application under Subpart H accelerated approval pathway in the U.S., as well as an application for Conditional Marketing Authorization in Europe. Secondary efficacy endpoints include rate of change in eGFR. Top-line efficacy data from the 36-week proteinuria endpoint analysis are expected in the first half of 2022.