Clinical Trials

We partner with researchers from around the world to conduct clinical trials studying our investigational therapies.

In late 2016, we announced positive results from the Phase 2 DUET study of sparsentan in which the overall sparsentan treatment group achieved statistical significance in the study's primary efficacy endpoint, reduction of proteinuria.1 Currently, the study is in its open-label phase, and the Company is working with the FDA to find the most expeditious path forward for sparsentan. This investigational therapy could be the first FDA-approved pharmacologic treatment option for patients with focal segmental glomerulosclerosis (FSGS), a rare kidney disorder that often leads to end-stage renal disease.2  

We are working to initiate the Phase 3 FORT study of RE-024, our investigational therapy for pantothenate kinase-associated neurodegeneration (PKAN), and expect to begin dosing patients in the coming months. The study will be conducted according to a Special Protocol Assessment (SPA) agreement with the FDA. As part of this process, Retrophin and the agency have agreed that the design of this pivotal trial is adequate to support a New Drug Application. RE-024 could be the first approved replacement therapy targeting the underlying cause of this rare and life-threatening neurodegenerative condition, as current therapeutic strategies are limited to symptom management.3 In 2015, we completed a Phase 1 single ascending dose study of RE-024 in 40 healthy adult volunteers. The double-blind, placebo-controlled study evaluated five oral dose levels of the compound up to 1,800 mg.

To learn more about our clinical trials, including enrollment and study centers, contact Retrophin at or visit the National Institutes of Health clinical trial registry.


  1. Trachtman H, Nelson P, Radko K on behalf of the DUET Investigators. Efficacy and Safety of Sparsentan, a Dual Angiotensin II and Endothelin Type A Receptor Antagonist, in Patients with Focal Segmental Glomerulosclerosis: A Phase 2 Trial (DUET).  Presented at the American Society of Nephrology Kidney Week Meeting; November 15-20 2016, Chicago, IL.
  2. Middleton, et al. Nephrology Rounds 2007; 5(4).
  3. Gregory, et al. GeneReviews. 2002.