FDA Introduces New Framework to Advance Individualized Therapies for Ultra-Rare Diseases

The FDA has issued draft guidance aimed at accelerating the development and approval of individualized therapies for patients with ultra-rare diseases, where conventional randomized controlled trials are often not feasible due to extremely small patient populations.¹

A shift toward mechanism-based evidence

The framework, developed by the Center for Biologics Evaluation and Research (CBER) and the Center for Drug Evaluation and Research (CDER), introduces a “plausible mechanism” approach. It is designed to help sponsors generate substantial evidence of effectiveness and safety using a combination of clinical, nonclinical, and manufacturing data tailored to highly specific therapies.²

“President Trump promised to accelerate cures for American families—and we are delivering, especially for children with ultra-rare diseases who cannot afford to wait,” said Health and Human Services Secretary Robert F. Kennedy, Jr.. “We are cutting unnecessary red tape, aligning regulation with modern biology, and clearing a path for breakthrough treatments to reach the patients who need them most.”

The guidance focuses on therapies that directly target the underlying cause of disease, including genome editing and RNA-based approaches such as antisense oligonucleotides. However, regulators note the framework may extend to other modalities that address a defined genetic, cellular, or molecular abnormality.

Core requirements for demonstrating effectiveness

At its core, the approach emphasizes several foundational elements: identifying the disease-causing mechanism, demonstrating that the therapy directly targets that mechanism, and confirming successful biological engagement. Sponsors are also expected to rely on well-characterized natural history data and show improvements in clinical outcomes or validated biomarkers.

“This guidance is a critical step the FDA is taking to tailor our regulatory approach to patients with ultra-rare conditions,” said FDA Commissioner Marty Makary, MD, MPH. “It is our priority to remove barriers and exercise regulatory flexibility to encourage scientific advances and deliver more cures and meaningful treatments for patients suffering from rare diseases.”

Balancing flexibility with scientific rigor

The agency acknowledged that trials in this space will inherently involve small sample sizes, placing greater emphasis on the robustness of evidence and the ability to rule out chance findings. The framework also incorporates chemistry, manufacturing, and controls considerations to ensure product quality alongside clinical evaluation.

“Designing treatments unique to individual patients has always been the promised goal of personalized medicine,” said Vinay Prasad, MD, MPH, director of CBER and chief medical and scientific officer. “After 25 years the FDA has, for the first time, outlined a framework to facilitate these approvals. The Plausible Mechanism Framework is a revolutionary advance in regulatory science.”

The draft guidance also introduces flexibility in how therapies may be studied and approved. For example, multiple variants of genome editing therapies targeting different mutations within the same gene could potentially be evaluated under a single application using master protocols, with additional variants supported by mechanistic evidence.

“The Plausible Mechanism draft guidance creates a novel framework through which cutting-edge treatments tailor-made for patients with ultra-rare diseases can be used as a basis for FDA approval,” said Tracy Beth Høeg, MD, PhD, acting director of CDER. “We anticipate our Plausible Mechanism draft guidance will inspire industry to place increased focus on individualized therapies, thereby driving innovation, improving safety, lowering costs and offering more patients with ultra-rare diseases a unique shot at a life-saving treatment.”

The guidance is now open for public comment, with stakeholders invited to provide feedback within 60 days of its publication in the Federal Register.

FDA streamlines drug approval process

A related shift from earlier in February signals broader regulatory momentum toward more flexible evidence standards. FDA leadership announced plans to move away from the long-standing expectation of two pivotal trials for drug approvals, instead allowing a single adequate and well-controlled study supported by confirmatory evidence.³

Makary and Prasad argued that advances in biology and trial design justify the change, writing, “In this setting, over-reliance on two trials no longer makes sense.”

The policy is expected to streamline development while placing greater emphasis on study quality, biological plausibility, and overall strength of evidence.

References

1. FDA Launches Framework for Accelerating Development of Individualized Therapies for Ultra-Rare Diseases. News release. FDA. February 23, 2026. Accessed March 2, 2026. https://www.fda.gov/news-events/press-announcements/fda-launches-framework-accelerating-development-individualized-therapies-ultra-rare-diseases

2. Considerations for the use of the Plausible Mechanism Framework to Develop Individualized Therapies that Target Specific Genetic Conditions with Known Biological Cause: Draft Guidance for Industry. FDA. Accessed March 2, 2026. https://www.fda.gov/media/191247/download

3. FDA Removes Two Study Requirement for New Drug Approval Process. Applied Clinical Trials. February 19, 2026. Accessed March 2, 2026. https://www.appliedclinicaltrialsonline.com/view/fda-removes-two-study-requirement-new-drug-approval-process