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The FDA approved Travere's drug for the kidney disease FSGS based on the surrogate endpoint of proteinuria, despite the drug failing on the traditional eGFR endpoint. This decision, following a company-backed effort to validate proteinuria, suggests increased regulatory flexibility and creates a new pathway for kidney disease drug approvals.
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For its leptomeningeal cancer drug, Plus Therapeutics found the FDA receptive to clinical trial endpoints beyond overall survival. The agency was open to "compartmental based endpoints" measuring efficacy within the targeted CNS area—a significant regulatory shift for non-systemic treatments with no established approval pathway.
The FDA issued Complete Response Letters for both REGENXBIO's gene therapy and DISC Medicine's oral drug, signaling high scrutiny for accelerated approvals. The agency specifically cited concerns over the relevance of surrogate endpoints and required more robust clinical trial data, highlighting the risks of relying on non-traditional approval pathways.
Running an unusually long, two-year Phase 2 trial allowed Vera to demonstrate stabilization of GFR, a hard kidney function endpoint. This robust, long-term data was crucial for de-risking their Phase 3 program and ultimately securing a coveted Breakthrough Therapy Designation from the FDA, accelerating their path to market.
For its alpha-1 antitrypsin deficiency program, Beam aligned with the FDA on an accelerated approval pathway based on a surrogate endpoint: restored alpha-1 protein levels. This strategy allows for faster market entry, with a longer-term confirmatory trial measuring clinical outcomes like lung and liver function running in parallel.
The FDA issued guidance supporting minimal residual disease (MRD) as an approval endpoint in multiple myeloma. This directly contradicts the CBER division’s recent rejections of drugs based on single-arm response rates, creating a "schizophrenic" and unpredictable regulatory landscape for developers.
After a decade on the market and multiple shifts in endpoints, Sarepta's definitive Phase 3 study for its DMD drugs failed. This outcome casts doubt on the entire accelerated approval framework for slowly progressive diseases, where surrogate endpoints may not translate to clinical benefit, leaving regulators and patients in a difficult position.
The successful use of a surrogate endpoint (proteinuria reduction) for IgA nephropathy approvals has created a clear regulatory pathway. This blueprint is now being leveraged by developers to advance therapies for other previously untreatable renal diseases like FSGS, de-risking their clinical programs.
The FDA's current leadership appears to be raising the bar for approvals based on single-arm studies. Especially in slowly progressing diseases with variable endpoints, the agency now requires an effect so dramatic it's akin to a parachute's benefit—unmistakable and not subject to interpretation against historical data.
While depth of response strongly predicts survival for an individual patient, the FDA analysis concludes it cannot yet be used as a surrogate endpoint to replace overall survival in pivotal clinical trials. It serves as a measure of drug activity, similar to response rate, but is not sufficient for drug approval on its own.
Following public pressure, the FDA seems to be entering a "kinder, gentler" era for orphan drugs. Reports indicate agency leaders are proactively meeting with companies post-rejection to find a path forward. This suggests a potential shift towards more flexibility for therapies in rare diseases with high unmet need, even with imperfect data.