A one-time gene therapy for Duchenne muscular dystrophy has met the main goal of the large, final stage of its trial, according to results presented at the Child Neurology Society meeting in Montreal, held October 14-171. The therapy, called RGX-202 and made by the US company Regenxbio, got muscles in treated boys making a shortened version of a missing protein above a preset target level 12 weeks after a single infusion1.
Duchenne is a rare inherited disease caused by changes in the gene for dystrophin, a protein that helps keep muscles intact. Without it, muscles steadily weaken and break down2. The company first announced headline results in May 20262, and the fuller picture shown at the October meeting adds details on safety and early physical function1.
What happened
The final stage of the trial, known as AFFINITY DUCHENNE, treated 31 boys aged 1 and older who could still walk. Each received a single drip into a vein1. The trial is open-label, meaning everyone knew who got the therapy, and there is no placebo (dummy treatment) group3.
The therapy uses a harmless virus shell, called AAV8, to carry a shortened version of the dystrophin gene into muscle cells4. That shortened protein is called microdystrophin. Regenxbio’s version keeps a part of the natural protein called the C-terminal domain, which the company says sets it apart32.
The main goal was simple to state: does the muscle make microdystrophin at 10% or more of normal levels by week 12? Muscle samples (biopsies) were available for 30 boys. Average levels topped 10%, meeting the goal with statistical significance, and 93% of boys with usable samples passed the 10% mark1.
The evidence so far
In its May announcement, Regenxbio reported that average microdystrophin levels reached 71.1% of normal across all participants and 41.6% in boys older than 8. It also said 80% of boys reached levels above 40%2.
Protein in muscle is not the same as stronger muscles, so the trial also looked at function. Nine boys had reached one year after treatment. Their results on the North Star Ambulatory Assessment, a standard score of everyday movements like standing and climbing, and on timed tests such as rising from the floor, a 10-meter walk or run and climbing stairs, favored treatment over outside comparison groups1. Those comparison groups were built from records of untreated boys, weighted to resemble the treated boys1.
Boys with higher protein levels at week 12 tended to show more improvement on the movement score at one year, according to the company’s announcement1.
Earlier, smaller stages pointed the same way. At the dose now used in the final stage, seven boys had movement scores at one year about 3.7 points higher than outside controls1. In a 2025 update on five boys aged about 6 to 12, the company reported an average gain of 4.5 points from their starting score at 12 months among the four who had reached that point5.
Safety
The trial report described the therapy as well tolerated. The most common side effects linked to the drug were vomiting (19 boys), tiredness (11) and nausea (10)1.
Two serious side effects were linked to the drug. An 8-year-old developed heart muscle inflammation (subacute myocarditis), and a 10-year-old had a liver injury without symptoms. Both resolved without lasting harm, according to the abstract. The company said the latest heart scan of the boy with myocarditis showed no scarring and no change in how well the heart pumps1. Boys also receive medicine to calm the immune system as part of the treatment plan, which the company describes as “proactive”2.
What it does not show yet
- No head-to-head comparison. With no placebo group, the function results rest on comparisons with records of other, untreated boys1. Such comparisons can differ from treated patients in ways that are hard to fully adjust for.
- Few boys with function data. Only 9 of 31 had reached one year when these results were shown1.
- Short follow-up. The main goal was measured at 12 weeks3. How long the protein lasts, and whether any benefit holds over years, is not yet known from this stage.
- Not yet peer reviewed in full. The results come from a conference presentation and company announcements12, and the trial registry shows no results posted yet3.
Who is behind it
The trial is sponsored and paid for by Regenxbio3. The analysis presented at the meeting was led by Jahannaz Dastgir, the company’s clinical development lead for the program1. The company’s chief medical officer, Steve Pakola, is also among the authors15.
Aravindhan Veerapandiyan of Arkansas Children’s Hospital is the trial’s principal investigator. In the company’s May press release he said:
“It’s encouraging to see robust microdystrophin expression, correlation with functional outcomes, and a manageable safety profile.”2
Pat Furlong, founding president of the patient group Parent Project Muscular Dystrophy, said in the same release that “today’s news gives us renewed optimism”2.
How it fits the field
Many gene therapy efforts for Duchenne take the same basic approach: delivering a shortened dystrophin gene in the hope of keeping muscles working2. At least one such gene therapy is already approved in the US, as Regenxbio noted in 2025 when it pointed to a measure the FDA had cited in that approval5.
Regenxbio argues its version differs in three ways: the extra C-terminal piece in its protein, the immune-calming regimen, and a manufacturing method it says improves purity2. Whether those differences lead to better results for boys has not been tested directly against other therapies.
What to watch next
Regenxbio says the results support filing for accelerated approval, a faster US route based on early signs of benefit, in 20272. That is later than the mid-2026 filing the company had planned in 20255.
A second, confirmatory part of the trial is under way. The company said in May that more than 20 boys had enrolled in it, with dosing of all 60 patients across both parts expected by mid-20262. The registry lists the study as no longer recruiting, with an estimated 65 participants3. The company says more data will come at future scientific meetings and in its filings to regulators2. Key things to look for are one-year function results in more boys, longer safety follow-up, and how the FDA responds to the filing.
