FSGS Payer Policy: Aligning Coverage with the Sparsentan Label

"FSGS Payer Policy: Aligning Coverage with the Sparsentan Label" takes up the gap between DUPLEX's enrollment criteria and the broader population the FDA label actually covers.

Dr. Campbell clarifies the FDA's approved label: sparsentan is indicated to reduce proteinuria in patients age 8 and older with FSGS who do not have nephrotic syndrome, defined either by documented history or by the concurrent presence of substantial proteinuria, low serum albumin, and edema. He notes the label doesn't set a minimum UPCR threshold and doesn't exclude any FSGS subtype, meaning primary, secondary, genetic, and undetermined-cause patients are all technically eligible for treatment. Breaking down the DUPLEX population, Dr. Campbell explains that non-nephrotic patients made up 68% of the trial and showed a clear treatment effect, with a 48% proteinuria reduction on sparsentan versus 27% on irbesartan, alongside a meaningful eGFR advantage. Among the 32% of patients who did have nephrotic syndrome, however, sparsentan showed no real advantage over irbesartan, 39% versus 37% proteinuria reduction, essentially indistinguishable results between the two arms.

Dr. Trachtman is asked to clarify the confusion some clinicians have around this distinction, since it's easy to assume a histologic FSGS subtype, rather than the nephrotic syndrome criteria themselves, determines eligibility. He traces the term nephrotic syndrome back to nephrologists recognizing that glomerular disease could present along a nephritic-to-nephrotic spectrum, and notes the FDA's definition required all three classic criteria together, not any single feature. He points out that average proteinuria was still in the nephrotic range across both trial arms, so proteinuria level alone doesn't explain the split in outcomes. Instead, Dr. Trachtman raises the possibility that patients with edema in the trial may simply have had more clinically active, less stable disease at enrollment, which could account for the muted treatment effect, rather than nephrotic syndrome itself blunting the drug's underlying biology.

Up next, in "Communicating with Payers: Practical Guidance for Sparsentan Access in FSGS," the experts close the series with practical guidance for aligning payer coverage with the evidence.