An FDA notice seeking public input is under review at the Office of Management and Budget, according to a Citeline report on October 12, 2026. The notice suggests FDA wants to consolidate its scattered rare disease flexibilities into one structured framework. As of October 13, it had not been published in the Federal Register, so its content, scope and timing are unknown.
For sponsors in rare and genetic disease, the report points to tools they already use being brought into one place. Consolidation could make FDA's expectations more predictable. It also draws attention to evidence that several of these tools, notably RDEP and the plausible mechanism draft, lean on: natural history data and small numbers of well-characterized patients.
CDER and CBER introduced the Rare Disease Evidence Principles (RDEP) in September 2025, generally for known genetic defects affecting fewer than 1,000 US patients. RDEP allows approval based on one adequate and well-controlled study plus robust confirmatory evidence, which can include natural history studies.
On February 23, 2026, FDA released draft guidance on a plausible mechanism framework for individualized genetic therapies. Akin Gump's summary lists reliance on well-characterized natural history in untreated patients among its core elements. Arnold & Porter notes that the framework does not create a new approval pathway.
FDA's revised draft guidance on substantial evidence of effectiveness, published in June 2026, applies across all disease areas. It clarifies how sponsors can rely on one adequate and well-controlled investigation with confirmatory evidence. Its comment period closed on September 22, and we covered what the single-trial effectiveness pathway means for sponsors in an earlier piece.
FDA's Rare Disease Innovation Hub runs the RISE workshop series with Duke-Margolis. The first workshop, in September 2025, covered controls in trials with small and diminishing populations. The START pilot, announced in 2023, gives selected sponsors more frequent FDA advice, including on the choice of patient population.
At the latest RISE workshop, an FDA official said relaxed p-values may suit some randomized rare disease trials, according to Citeline reporting on October 8. The official reportedly framed this as easier to accept than a single-arm trial and noted it may not apply in all situations. These are reported remarks from one official and fall short of stated agency policy.
Natural history data have a defined role in two of these tools. They count as confirmatory evidence under RDEP and form a core element of the plausible mechanism draft guidance.
An analysis of 659 randomized rare disease trials published in PLOS Medicine found that 30.2% of trials registered in 2010–12 were discontinued. Poor patient accrual was the most common reason, accounting for about a third of those discontinuations.
The study dates from 2019 and covers trials registered over a decade ago, so its figures describe a long-standing pattern. Recruitment also depends on diagnosis, which is often slow.
A 2024 European Journal of Human Genetics analysis of the 2022 EURORDIS Rare Barometer survey covered 6,507 people with 1,675 rare diseases living in 41 European countries. Mean time to diagnosis was 4.7 years and the median 0.8 years, figures that EURORDIS's results slides also report.
The mean is pulled up by a long tail of very long delays. These are European data, and they exclude people who remain undiagnosed.
This section is analysis and goes beyond anything FDA has stated. Sano provides patient identification and genetic testing services, so we have a commercial interest in this question.
RDEP and the revised substantial evidence draft allow packages built on one adequate and well-controlled study plus confirmatory evidence, and RDEP lists natural history studies among the forms that confirmatory evidence can take. Packages built this way rest on fewer, better-characterized patients. Each patient's genotype confirmation, phenotyping depth and longitudinal data therefore carries more of the evidentiary load.
A consolidated framework could make FDA's expectations more predictable, which would help sponsors plan. The operational work of finding and characterizing eligible patients stays with sponsors either way, and for programs that use these flexibilities, patient identification and data infrastructure become the limiting factor.
For feasibility, epidemiology estimates indicate how many patients should exist and say little about how many can be found, confirmed and enrolled. A patient-first approach to site selection and feasibility starts from identified individuals who meet genotype and phenotype criteria, then maps site capacity to them.
As we described in the infrastructure gaps biopharma misses in rare and genetic trials, much of the risk is set before recruitment begins. Identification depends on provider-led processes and on how well diagnostic workflows are integrated. Smaller trials remain exposed to these gaps, and each lost or poorly characterized patient removes a larger share of the evidence package.
Our recruitment work on a GBA1 Parkinson's disease gene therapy trial shows what genotype-first identification involves in practice. Over four months, Sano identified 17 confirmed GBA1 participants, 9 from its existing database and 8 through digital outreach. Two participants were dosed, and genetic testing kit volume was projected to exceed the contracted amount by 70%.
Sponsors planning to use these flexibilities should treat identification, genotype confirmation, phenotyping and longitudinal follow-up as protocol-stage design decisions. Natural history collection and recontactable cohorts are easier to build before a pivotal study than after one. We have written about patient-centered approaches to natural history and trial design that support this early work.
The first marker is publication of the notice, which would confirm its title, docket and comment deadline. Until then, every description of the expected framework, including this one, rests on a trade press report.
The second is how the text describes natural history and patient characterization. A framework that sets expectations for genotype confirmation, phenotyping depth or longitudinal follow-up would give sponsors a planning baseline. Leaving those points open would mean each program settles them with FDA separately.
The notice raises questions sponsors can put to FDA directly. One is how much natural history data a program needs before it can rely on a single-study package. Another is whether expectations will differ between ultra-rare populations under RDEP and larger rare disease populations.
A further question is how FDA will weigh data from patients identified outside traditional site networks. Clinical development, regulatory and clinical operations teams see where recruitment and characterization break down. The comment period gives them a direct route to put those operational realities in front of FDA while the framework is still being shaped.
If your team is assessing feasibility for a genotype-defined program under these flexibilities, get in touch.