A study of an investigational treatment for focal segmental glomerulosclerosis, sparsentan, demonstrated a greater than two-fold reduction of proteinuria after the eight-week, double-blind treatment period, compared to irbesartan. Retrophin Inc. announced the top-line results from the Phase 2 DUET earlier this month.

“We are very pleased with the robust top-line results from DUET, which suggest sparsentan could be a significant advancement in the treatment of FSGS,” said Stephen Aselage, chief executive officer of Retrophin. “FSGS patients today face poor outcomes with limited medical options; we look forward to working with the FDA to find the most expeditious path forward that would deliver the first approved pharmacologic treatment to the FSGS community.”

In the DUET study, the mean reduction of proteinuria from baseline after eight weeks of treatment for all patients treated with 200, 400, and 800 mg/day of sparsentan (n=64) was 44.8%, compared to a mean reduction of proteinuria for all patients receiving 300 mg/day of irbesartan (n=32) of 18.5% (p=0.006).

The mean reduction of proteinuria from baseline after eight weeks of treatment for all patients treated with 400 mg and 800 mg doses of sparsentan (n=51) was 47.4%, compared to a mean proteinuria reduction of 19% for patients receiving 300 mg of irbesartan (n=25) in these two dose cohorts (p=0.011). The comparison of individual sparsentan dose cohorts to irbesartan showed clear signals of relative improvement, but did not reach statistical significance.

“The results from DUET serve as proof of concept for sparsentan’s novel approach of combining endothelin receptor type A blockade with angiotensin II inhibition for the treatment of FSGS,” said Alvin Shih, MD, executive vice president and head of research & development for Retrophin. “Significant reductions in proteinuria, along with a well-tolerated preliminary safety profile have us excited about being one step closer to providing a new treatment option for patients with FSGS.”

The company said it plans to present detailed study results, including data from the open label extension, at an upcoming medical meeting or in a peer-reviewed publication.