Sparsentan is a novel small-molecule candidate in Phase 3 development for the treatment of focal segmental glomerulosclerosis (FSGS) , a serious kidney disorder that often leads to end-stage renal disease (ESRD). The US Food and Drug Administration (FDA) and European Medicines Agency (EMA) 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 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 are no medications approved specifically for the treatment of 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 single molecule designed to be a dual endothelin receptor type A (ETA) and angiotensin II receptor type 1 (AT1) antagonist. Our investigational approach is to attempt to reduce proteinuria, a characteristic marker of kidney injury in both FSGS and IgAN, with sparsentan. Lowering proteinuria levels is associated with better outcomes.
Sparsentan for FSGS
After completing the 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 surrogate efficacy endpoint – the proportion of patients achieving modified 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 quarter 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, Retrophin 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. Top-line efficacy data from the 36-week proteinuria endpoint analysis are expected in the first half of 2022. Secondary efficacy endpoints include rate of change in eGFR.
RESOURCES: MEDICAL JOURNAL ARTICLES
- Early Change in Urine Protein as a Surrogate End Point in Studies of IgA Nephropathy: An Individual-Patient Meta-analysis, American Journal of Kidney Disease, September 2016
- Efficacy and Safety of Sparsentan Compared with Irbesartan in Patients with Primary Focal Segmental Glomeruloscerosis: Randomized Controlled Trial Design (DUET), Kidney International Reports, March 2017
- An Outcomes-Based Definition of Proteinuria Remission in Focal Segmental Glomerulosclerosis, Clinical Journal of the American Society of Nephrology, March 2018
- DUET: A Phase 2 Study Evaluating the Efficacy and Safety of Sparsentan in Patients with FSGS, Journal of the American Society of Nephrology, November 2018
- Performance of GFR Slope as a Surrogate End Point for Kidney Disease Progression in Clinical Trials: A Statistical Simulation, Clinical Journal of the American Society of Nephrology, March 2019
- Evaluating Glomerular Filtration Rate Slope as a Surrogate End Point for ESKD in Clinical Trials: An Individual Participant Meta-Analysis of Observational Data, Journal of American Society of Nephrology, September 2019
- GFR Slope as a Surrogate End Point for Kidney Disease Progression in Clinical Trials: A Meta-Analysis of Treatment Effects of Randomized Controlled Trials, Journal of the American Society of Nephrology, September 2019
- Implementing the Kidney Health Initiative Surrogate Efficacy Endpoint in Patients With IgA Nephropathy (the PROTECT Trial), Kidney International Reports, November 2019