FDA Issues Draft Guidance to Accelerate Individualized Therapies for Rare Diseases
The FDA has issued draft guidance creating a "Plausible Mechanism Framework" to accelerate approval of individualized therapies for ultra-rare diseases where traditional clinical trials are not feasible. The guidance focuses on gene editing and RNA-based treatments targeting specific genetic abnormalities.
The U.S. Food and Drug Administration has issued draft guidance creating a "Plausible Mechanism Framework" — a regulatory pathway designed to accelerate approval of individualized therapies, including gene editing and RNA-based treatments, for conditions where traditional large-scale clinical trials simply are not feasible due to small patient populations.
The guidance focuses on therapies that target a specific genetic, cellular, or molecular abnormality and are designed to correct or modify the underlying cause of disease. Because these treatments are often tailor-made for individual patients, the FDA acknowledges that clinical investigations will involve small sample sizes, but says results must still be sufficiently robust to rule out chance findings.
The draft guidance is open for public comment for 60 days through Regulations.gov.
Researchers at the Broad Institute, Harvard University, and the University of Minnesota have developed a new gene-editing method called PERT that could one day treat a range of rare genetic disorders. PERT uses prime editing to tweak certain genes so the body can make full-length, working proteins—even when there's a glitch in the DNA.
Some rare diseases happen because of "nonsense mutations"—basically, random stop signs in DNA that cut protein-making short. This leads to broken or missing proteins behind diseases like cystic fibrosis and Tay-Sachs. PERT uses prime editing to convert a dispensable endogenous tRNA gene into an optimized suppressor tRNA that reads through those stop signals so cells can finish making the proteins they need.
In lab tests, PERT worked on human cells with up to 80% efficiency and didn't mess with other parts of the genome. It even restored protein activity in models for several tough-to-treat diseases. Since nonsense mutations account for about a quarter of disease-causing changes and the team screened thousands of tRNA variants to identify a small number of optimized suppressor tRNAs, one treatment could help lots of different conditions—which could help make therapies faster and less expensive for more patients.