A gene therapy for Duchenne muscular dystrophy has met a critical protein expression goal, clearing the way for its developer to seek U.S. approval as early as 2027. The treatment, RGX-202, produced microdystrophin levels averaging 71 percent across all treated boys, and nearly 42 percent in those over age 8 who are already beginning to decline from the progressive muscle disease.
Duchenne is a fatal genetic condition with no cure, caused by the absence of dystrophin, a protein that acts as a muscular shock absorber. RGX-202 delivers a gene that instructs cells to produce microdystrophin, a shortened but functional version of the protein. Unlike the only approved gene therapy for Duchenne, Sarepta Therapeutics’ Elevidys, RGX-202 uses a different viral carrier and produces a larger form of microdystrophin. It also pairs with a distinct regimen of immune-suppressing drugs, which the company believes will yield a better safety profile.
The company struck an abbreviated approval path with the U.S. Food and Drug Administration after earlier trial hints of benefit. That plan did not require a placebo control group, which other Duchenne gene therapies have struggled to outperform. Instead, Regenxbio expanded a single arm study and set a benchmark of achieving microdystrophin levels at 10 percent of normal. The new data far exceeded that target and showed a statistical impact on disease progression, a milestone other developers have found difficult to reach.
However, the road to approval is not without obstacles. Two serious side effects were reported in the trial, and the FDA has undergone significant leadership changes, including the recent resignation of Commissioner Marty Makary. Several rare disease drugmakers have been surprised by regulatory decisions in this shifting environment. Regenxbio executives acknowledged the uncertainty but said they are waiting for new FDA leadership to settle before filing a formal application. The company is targeting approval in 2027.
“We expect that the new leadership will have a mandate on rare disease flexibility,” said CEO Curran Simpson on a recent analyst call. “Those are the indications that we’re hearing will be more uniformly adopted, and with that environment, we’re in great shape with our data to push for accelerated approval.” If successful, RGX-202 could offer a new option for families affected by Duchenne, potentially with a stronger safety record than the current standard of care.