As Rare Disease Frustration Grows, FDA Flexibility Is Put to the Test
Across the rare disease community, frustration is mounting. It’s not just from families, but from the biotechnology companies developing potential therapies as well.
The U.S. Food and Drug Administration has publicly acknowledged that traditional drug development models do not always fit rare diseases, where patient populations are small and disease progression varies widely. In 2025, the agency unveiled its Rare Disease Evidence Principles to signal a more flexible approach, including the possibility that single-arm trials supported by real-world evidence could serve as pivotal evidence in some rare settings.
Yet in interviews and public comments, both industry leaders and patient advocates say that in practice, those principles have not always translated into predictable decisions.
In candid remarks captured in Endpoints News under the headline “Bat Sh-t Crazy: Biopharma Leaders Unload on Regulatory Chaos,” multiple executives described growing instability in their interactions with regulators, with one saying, “Things are completely unpredictable,” another calling the FDA “a wild card at this point,” and a third adding, “The FDA is just making things up as they go along and not following normal procedures, and we are just stuck on this rollercoaster.”
That frustration cuts across stakeholders. Patients and advocacy groups are raising similar concerns about how evidence is interpreted in cases where conventional trial design is nearly impossible.
When the Standard Model Breaks Down
Modern regulatory science evolved around large randomized trials, clear statistical thresholds and well-validated measures. That model works in common diseases with thousands of potential participants. Rare diseases rarely offer that kind of dataset.
Instead, researchers rely on small cohorts, natural history data, long-term observational signals and patient-reported outcomes. For families living with progressive conditions, even modest stabilization can be meaningful, even if it does not meet traditional endpoints.
That misalignment has surfaced in several high-profile examples.
Just last week, Disc Medicine received a complete response letter (CRL) rejection for bitopertin in the treatment of erythropoietic protoporphyria (EPP). During a company call, management reiterated their belief that the study of bitopertin was well-designed and demonstrated clinical benefit required for full approval. While the study won on the primary endpoint, the FDA took issue with the relationship between the biomarker and the disease.
In spinocerebellar ataxia, a group of ultra-rare neurodegenerative diseases with no approved therapies, Biohaven’s investigational therapy troriluzole was studied for nearly a decade. Real-world evidence suggested that patients treated with trorilzole experienced a slower progression compared with matched external controls. In fact, the 3 year external control study hit statistical significance and achieved its primary endpoint. For many families, the promise of slowing decline carried deep emotional weight.
Despite this, the FDA issued a CRL rejecting the approval application, saying the evidence did not meet its standards. Biohaven had sought approval after extensive engagement with regulators and repeatedly updated its protocol and analysis plan based on feedback. The situation was more than a business setback. Company management described the experience as a barrier to patient access, saying patients were being denied care because of “bureaucratic red tape.”
Similar debates have occurred in other rare disease communities.
In Friedreich’s ataxia, families watched a promising therapy fail to gain approval despite signals of slowed progression. At a recent patient panel discussion, one person said “It should be a patient-centric approach. How can the life of the patient be made the easiest? They are already undergoing too many problems.”
In Duchenne muscular dystrophy, the FDA granted accelerated approval to a therapy based on a surrogate biomarker, demonstrating that the system can adapt. But that decision also prompted debate about evidentiary rigor and the appropriate balance between urgency and certainty.
In amyotrophic lateral sclerosis, patients saw a therapy approved amid intense advocacy only to have it withdrawn after further data did not confirm benefit. And in Down syndrome, an experimental Alzheimer’s study was halted because enrollment proved too difficult, underlining the structural challenge of generating evidence in small or highly specific populations.
Different Views of Risk
The FDA is tasked with ensuring that therapies are safe and effective for the public at large. Regulators must weigh not only individual benefit but population-level risk.
For many patients with progressive rare diseases, the risk of waiting feels greater than the risk of uncertainty. Daily decline is a reality, and many families are willing to accept higher uncertainty when the alternative is continued loss.
That divergence in risk tolerance is structural rather than emotional. It reflects different mandates. But the consequences of regulatory delay are real: expanded access programs can close, insurers may decline coverage for investigational drugs, and clinical trials can end. Patients may lose access to something they and their doctors believe is helping.
For those families, the psychological and physical impact of losing access can be profound.
Policy Proposals and Ongoing Debate
Regulatory science is evolving. Adaptive trial designs, real-world evidence and patient preference studies are increasingly part of regulatory conversations. The FDA’s Rare Disease Evidence Principles reflect that evolution, and in some contexts the agency has shown willingness to adapt its frameworks.
Yet many in the rare disease community question whether policy statements are translating into consistent decision-making.
In November 2025, a coalition of biotechnology leaders, patient advocates, investors and academics sent a letter to the White House urging greater clarity and consistency in rare disease review standards. The letter cited declining orphan drug approvals and a wave of unexpected regulatory setbacks across multiple programs, warning that uncertainty in evidentiary expectations could stall innovation and delay access for patients with no alternatives.
The signatories did not call for weakened science. They called for predictability and transparency.
A Critical Juncture
More than 95 percent of rare diseases still have no approved treatment. As genetic and precision therapies advance, more rare conditions will reach a point where potential therapies exist but evidence remains incomplete.
The FDA faces a formidable task: protect public health, encourage innovation and maintain trust, all while evaluating therapies in populations that may never be large enough to produce textbook levels of statistical certainty.
For patients and families, the cost of delay is not abstract. It is measured in lost time – time they may not have.