The FDA's approval of Travere Therapeutics' sparsentan for focal segmental glomerulosclerosis (FSGS), despite the drug failing to show meaningful improvement in actual kidney function, represents more than a single regulatory misstep. It exemplifies a dangerous over-reliance on surrogate endpoints that has become systemic in accelerated approval pathways. While Adam Feuerstein's STAT News report correctly flags the agency's unusual flexibility in this case—contrasting with recent criticism for insufficient flexibility in other rare-disease rejections—it underplays the historical context, the weakness of the supporting evidence, and the broader implications for patient outcomes and public trust.

At the center is the DUPLEX trial (NEJM, 2023), a Phase 3 double-blind RCT involving 371 patients with FSGS. Sponsored by Travere (clear commercial conflict of interest), it demonstrated that sparsentan reduced proteinuria by approximately 50% more than the active control irbesartan at 36 weeks. Proteinuria reduction is an accepted surrogate under FDA guidance for accelerated approval in kidney diseases. However, the trial's interim analysis revealed no statistically significant difference in eGFR slope—the key measure of kidney function decline. Full results at 108 weeks similarly failed to confirm clinical benefit on this hard endpoint. These limitations were known at the time of approval, yet the FDA granted marketing authorization anyway, deferring definitive proof to future confirmatory studies that may never fully materialize or could be years away.

This decision fits a troubling pattern missed by much mainstream coverage. Consider Biogen's aducanumab (Aduhelm) for Alzheimer's, accelerated in 2021 on amyloid-plaque reduction (a surrogate) despite an advisory committee vote against approval and two pivotal trials failing their primary clinical endpoints (JAMA Internal Medicine analysis, 2022). Only 60% of oncology accelerated approvals between 2009-2018 ultimately verified clinical benefit in confirmatory trials (JAMA Oncology, 2022 meta-review of 93 indications, no industry funding). In cardiology, multiple drugs that improved surrogate lipid markers later showed no cardiovascular benefit or increased harm (e.g., torcetrapib's HDL-raising failure in the ILLUMINATE RCT, NEJM 2007, n=15,067). FSGS approvals now join this lineage, prioritizing speed for rare diseases with high unmet need while discounting the risk that surrogates can mislead—especially in heterogeneous, slowly progressing conditions where short-term biomarker changes do not reliably predict avoidance of dialysis or transplant.

What the original STAT coverage also glossed over is the erosion of regulatory credibility. Public trust in the FDA has already been strained by high-profile reversals, pricing scandals (Travere has signaled aggressive orphan-drug pricing likely exceeding $100,000 annually), and post-marketing withdrawals. When regulators approve therapies on biomarkers alone without compelling evidence of slowed disease progression, they shift the burden of uncertainty onto patients and clinicians. Observational follow-up data cannot substitute for well-designed RCTs with hard clinical outcomes. A 2021 Health Affairs analysis of accelerated approvals found that when confirmatory trials are delayed or negative, patients remain exposed to unproven treatments for extended periods.

The solution lies in stricter guardrails: mandating that surrogate validation studies precede—not follow—approval for progressive diseases, requiring independent oversight of post-approval trials, and swift withdrawal mechanisms when benefit is not confirmed. Until then, this FSGS decision risks becoming another case study in how the pursuit of rapid innovation can undermine the very evidence-based foundation that protects patients. Peer-reviewed evidence, not corporate press releases, must remain the north star.