FSGS Drug Development No Longer a ‘Graveyard’: What Comes After Sparsentan’s Approval

The recent US Food and Drug Administration (FDA) approval of sparsentan (Filspari) for focal segmental glomerulosclerosis (FSGS) may mark more than the arrival of a new therapy, and could signal a turning point in how drugs are developed and evaluated in the disease.

In an interview with HCPLive, Howard Trachtman, MD, an adjunct clinical professor of pediatrics at the University of Michigan and a DUPLEX study investigator, emphasized that the decision reflects both scientific progress and a shift in regulatory clarity that could accelerate future innovation.

Previous Limitations In Therapeutic Options For FSGS

“FSGS has been like a graveyard for drug development. It’s a difficult disease, its outcomes are bad, and there’s been really marginal understanding of the pathophysiology of the disease,” said Trachtman.

Historically, limited understanding of disease mechanisms and a lack of validated endpoints discouraged pharmaceutical investment, particularly as research efforts concentrated on more prevalent conditions such as diabetic kidney disease. As Trachtman noted, despite being relatively uncommon, the overall burden of FSGS remains substantial, with few reliable treatment options available to clinicians.

The approval of sparsentan may begin to change that dynamic, in part because it establishes a clearer regulatory pathway for future therapies.

The Future of FSGS Treatment

“The approval was based on an endpoint that really opens the door to engagement with pharmaceutical companies, so that they know they have a measure of efficacy that can be considered by regulators,” he explained.

By anchoring efficacy to proteinuria reduction, the decision provides drug developers with a more predictable framework for clinical trial design. This, Trachtman suggested, could encourage broader investment and accelerate the entry of new therapies into clinical testing.

“As we really accelerate the scientific understanding of the heterogeneity of FSGS, clearly more drugs are going to come to the clinic for testing. And this trial really sets a standard that it can be done.”

Beyond expanding the pipeline, Trachtman pointed to a growing emphasis on better characterizing the disease itself. FSGS is increasingly understood as a heterogeneous condition driven by multiple underlying mechanisms, including genetic, immunologic, and metabolic factors.

According to Trachtman, clinicians need to target the right drug to the right patient with FSGS, knowing that they’re not all the same—they’re subtypes.

This shift toward more precise classification may ultimately enable a more personalized approach to treatment, aligning specific therapies with distinct disease pathways.

At the same time, Trachtman emphasized that continued progress will depend on sustained collaboration across the nephrology community, including clinicians, researchers, patients, and industry stakeholders.

“These are hard diseases to study, and cooperation and collaboration is going to be key to really move the ball forward consistently.”

As post-marketing data collection and longer-term follow-up continue, the full clinical impact of sparsentan remains to be defined. However, its approval may already be influencing the trajectory of research in FSGS—transforming a field once marked by limited progress into one poised for renewed therapeutic development.