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iStock, Andrii Yalanskyi Following several recent initiatives, the FDA’s newest rare disease framework sets out to standardize the agency’s approach to scientific evidence and bring rare disease therapies to patients faster. The FDA revealed a new framework Wednesday for its approach to rare disease drug regulation built to encourage innovation by standardizing the way clinical trial requirements are applied across diseases. To allow for a faster and more systematic path for as many as 10,000 different rare conditions affecting 30 million Americans, the FDA said drug development should account for nuance by approaching each disease based on the evidence that can be realistically generated in small patient populations. “As we learn more about rare diseases and better understand the breadth of suffering they cause, we must ensure that America’s regulatory system remains at the forefront—prepared to respond to emerging science, anticipate the needs of patients and families, and help bring safe and effective therapies to those who need them,” Acting FDA Commissioner Kyle Diamantas said in a prepared statement accompanying the announcement of the Rare Disease Framework Initiative. In a white paper elaborating on the new framework, the agency touted its current rare disease programs, including the FDA Rare Disease Innovation Hub , the Center for Drug Evaluation and Research (CDER)’s Accelerating Rare disease Cures (ARC) program and the Rare Disease Endpoint Advancement (RDEA) pilot program , a collaboration between CDER and the Center for Biologics Evaluation and Research (CBER). “We need to build on, systematize and operationalize these individual efforts into a consistently utilized, cross-center approach that champions the use of cutting-edge science, novel methodologies and innovative statistical approaches,” the FDA wrote. Just 5% of rare diseases currently have an FDA-approved treatment, according to the agency’s announcement. The agency is committed to “providing greater clarity, consistency, and predictability in regulatory decision-making,” incorporating the patient’s voice, bringing in external experts and shared resources and applying risk-based approaches—especially in chemistry, manufacturing, and controls review and pre-approval inspections. The Rare Disease Framework Initiative follows the “ plausible mechanism ” pathway introduced in November 2025 by former FDA Commissioner Marty Makary to expedite treatments for diseases with exceedingly small patient populations, for which a randomized trial would not be feasible. Rare diseases FDA Unwraps ‘Plausible Mechanism Pathway’ for Personalized Therapies The plausible mechanism pathway “could accelerate gene therapy/editing development,” analysts at William Blair said Thursday, while adding that additional clarity is needed. November 13, 2025 · 3 min read · Tristan Manalac Read more While the FDA aims to standardize regulatory action across its divisions, the agency clearly recognizes that rare diseases are unique and must be treated as such. “Americans with rare diseases cannot afford a regulatory system that treats every condition the same,” Health Secretary Robert F. Kennedy Jr. said in the Wednesday announcement. “We will remove unnecessary barriers, embrace cutting-edge science and accelerate promising treatments while upholding FDA’s rigorous standards.” Rare disease organizations lauded the new framework. “NORD particularly welcomes the FDA’s emphasis on strengthening consistency and predictability across review divisions, incorporating patient perspectives throughout development and review, drawing upon external scientific and clinical expertise, and building the institutional knowledge necessary to support sound regulatory decision-making,” Pam Gavin, president and CEO of the National Organization for Rare Disorders (NORD) said in an official statement Wednesday. “What makes this initiative especially important is the opportunity to move beyond case-by-case regulatory accommodations toward a framework designed around the scientific realities of rare diseases,” Gavin added. The Alliance for Regenerative Medicine (ARM) also commended the FDA’s effort to set rare diseases apart, giving them the individual attention they need as opposed to rubber-stamping an ill-fitting regulatory method. “The agency rightly recognizes that a regulatory system built for common diseases cannot simply be repurposed for rare disorders,” ARM wrote in a statement, noting that the framework’s success in the cell and gene therapy space will depend on forthcoming FDA guidance and rulemaking with regard to allowing single-arm trials and natural history data. Indeed, many of the FDA’s highest-pro reversals of guidance have centered around the use of external controls. In November last year, the agency disagreed with previous FDA guidance allowing uniQure’s Phase 1/2 study—which used a natural history external control—to support a regulatory application for its Huntington’s disease gene therapy AMT-130. And the use of an externally controlled study was “one of the major issues” raised in the July 2025 complete response letter for Capricor’s deramiocel, being developed for Duchenne muscular dystrophy cardiomyopathy, CEO Linda Marbán said during a BioSpace webinar in March. The FDA has set an Oct. 28 meeting to discuss the framework, soliciting feedback from patients, advocates and members of the industry. FDA FDA Reversals in Rare Disease Space Highlight Confusion Around External Controls While recent FDA guidance speaks to the agency’s support of innovative trial designs—including the use of external controls—the application of this flexibility appears to be inconsistent. One former regulator says the situation is more nuanced. April 6, 2026 · 6 min read · Heather McKenzie Read more

uniQure’s Huntington’s disease gene therapy has failed to significantly slow disease progression after 48 months, sending the biotech’s stock down 41% when trading began. But mitigating circumstances and the ongoing strength of a secondary endpoint kept analysts optimistic about AMT-130’s path to approval. One year ago, uniQure linked AMT-130 to a 75% slowing of disease progression, as measured by the composite Unified Huntington’s Disease Rating Scale (cUHDRS), at Month 36 of a phase 1/2 trial. Tuesday, the biotech shared updated data on the 12 patients. At month 48, uniQure linked AMT-130 to a 44% slowing of disease progression on cUHDRS. The result fell short of statistical significance. Investors reacted badly to the news. Yet, while the biotech’s share price fell to $23.15 when the market opened, analysts and uniQure executives were more positive about the update. The trends seen in the data “are positive and meaningful” for patients, uniQure CEO Matt Kapusta said on a conference call with investors. Guggenheim Securities analysts voiced optimism about AMT-130 in a note to investors. The optimism reflects questions about the implications of the missed primary endpoint and confidence provided by a secondary endpoint. More than half of the external control data used in the month 48 primary endpoint analysis are missing, Kapusta said. “While missingness is inherent to long-term natural history datasets, the patients who left the control were declining markedly faster than those who remained,” Kapusta said. “Over time, the comparator increasingly reflected a healthier population than at baseline. This bias cuts against AMT-130, not for it. It understates [the] treatment benefit.” The external comparator “may have several methodological flaws,” Guggenheim analysts said. Notably, a single outlier “contributed approximately one third of the overall cUHDRS degradation” between month 36 and month 48, the analysts said. The biotech reported a 54% slowing of cUHDRS disease progression in a post hoc analysis using the prior external control. The impact of the weakening of the cUHDRS data, regardless of external control, was offset by the steady performance of a secondary endpoint. Total functional capacity (TFC) showed a 61% slowing of disease progression at month 48, replicating the 60% result reported at month 36. Kapusta framed TFC, the primary endpoint of uniQure’s confirmatory trial, as a critical measure for Huntington’s patients. “TFC is the most direct measure we have of what patients and families care about,” Kapusta said. “It captures whether someone can hold a job, manage their own finances and perform the daily tasks that allow them to live independently.” uniQure filed for accelerated FDA approval based on month 36 AMT-130 data compared to the prior external control. It is difficult to speculate on whether the FDA will “rerun the analysis with the new data cut or not,” Walid Abi-Saab, M.D., chief medical officer of uniQure, said on the conference call. “That is something that we will deal with if the FDA asks us to run it or if they run it themselves,” Abi-Saab said. AMT-130 has already endured a tumultuous journey to the FDA. In March, the FDA rejected uniQure’s plan to file for accelerated approval based on the phase 1/2 data. Months later, the agency reversed its opposition to the submission, leading uniQure to file for accelerated approval early this month.