Clinical Trials

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

In the second half of 2017, we are planning to initiate a pivotal Phase 3 trial evaluating sparsentan for the treatment of focal segmental glomerulosclerosis (FSGS). Sparsentan could be the first FDA-approved pharmacologic treatment option for patients with this rare kidney disorder that often leads to end-stage renal disease.1  

The trial will include an interim assessment of proteinuria that could serve as the basis for a New Drug Application seeking Subpart H accelerated approval of sparsentan. The confirmatory endpoint of the study will subsequently compare changes from baseline in estimated glomerular filtration rate, or eGFR. In the Phase 2 DUET study, which is currently in its open-label phase, the overall sparsentan treatment group experienced significant reductions in proteinuria. Sparsentan was generally safe and well tolerated in the study.2

We are also planning 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 mid-2017. Detailed information about this pivotal trial can be found at and 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 Clinical


  1. Middleton, et al. Nephrology Rounds 2007; 5(4).
  2. 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.
  3. Gregory, et al. GeneReviews. 2002.