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.
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The pharmaceutical industry's focus on rare diseases has intensified, with 57% of all novel drugs approved in 2025 designated as orphan treatments. This is a continued increase from prior years, indicating a strategic shift towards smaller patient populations with high unmet needs, as exemplified by three different drugs for Hereditary Angioedema (HAE) being approved within ten weeks.
The FDA's new pathway for rare disease drugs, based on causal biology, is scientifically promising. However, the name "plausible mechanism" is a critical flaw. The term sounds weak, creating doubt for patients and giving payers powerful leverage to deny coverage by implying a lower standard of evidence.
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 drug's mechanism avoids maximum suppression, instead aiming for a precise balance—"not too much, not too little." This "Goldilocks" approach to intercepting BAF and APRIL cytokines is key to resolving inflammation and stabilizing kidney function without causing excessive immunosuppression, a critical differentiator in autoimmune therapies.
Corvus Pharmaceuticals' ITK inhibitor received FDA encouragement to proceed directly from Phase 1 to a Phase 3 registrational trial for T-cell lymphoma. This was due to the disease's high mortality, lack of effective treatments, and the drug's exceptionally strong early survival data.
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.
Using safety and preliminary efficacy data from its lead drug for MPS1, Immusoft successfully requested an FDA waiver for definitive toxicology studies for its next program in MPS2. This platform approach saves significant time and capital, accelerating the entire pipeline without 'reinventing the wheel'.
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.
The GLORA-IV trial is designed with a dual endpoint, evaluating both patient response rate and overall survival. This structure creates an alternative pathway for regulatory approval based on response rates, which can be assessed faster than survival, strategically de-risking the lengthy and expensive trial process.
