REGENXBIO recently announced positive topline results from the Phase 3 portion of the AFFINITY DUCHENNE trial evaluating RGX-202, an investigational gene therapy for Duchenne muscular dystrophy (DMD). According to the company, the study met its primary endpoint with high statistical significance, while also showing encouraging functional improvements in treated patients.
What Did the AFFINITY DUCHENNE Trial Show?
The most important finding from the press release was that 93 percent of patients achieved more than 10 percent microdystrophin expression at Week 12 after treatment with RGX-202. Researchers also reported an average microdystrophin expression level of 71.1 percent across participants.
- Achieved primary endpoint with high statistical significance; 93 percent of patients achieved microdystrophin expression above 10 percent (p<0.0001)
- Statistically significant correlation between RGX-202 microdystrophin expression and functional improvement (NSAA n=9), supporting validity of surrogate endpoint
- Well-tolerated, differentiated safety profile
- Company preparing for potential accelerated approval in 2027
In addition, interim functional data suggested that patients experienced improvement in NSAA (North Star Ambulatory Assessment) scores and timed functional tests such as:
- Time to Stand
- 10-Meter Walk/Run
- Time to Climb
These results are important because NSAA is one of the most widely used clinical tools for evaluating motor function in boys with Duchenne muscular dystrophy.
Why Is NSAA Improvement Important?
NSAA Measures Real-Life Functional Abilities
The NSAA scale evaluates everyday physical abilities such as standing up, climbing steps, walking, and jumping. In Duchenne muscular dystrophy, NSAA scores typically decline over time as muscle damage progresses.
A stabilization or improvement in NSAA scores may suggest that a therapy is helping preserve muscle function or slow disease progression.
Correlation Between Microdystrophin and Functional Improvement
REGENXBIO also stated that RGX-202 demonstrated a statistically significant correlation between microdystrophin expression and functional improvement at one year. This is particularly important because regulators such as the FDA increasingly want to see evidence that biomarker improvements translate into meaningful clinical benefit for patients. Learn More: NSAA
Microdystrophin Expression Was Observed
93 percent of Patients Exceeded the 10 percent Threshold
One of the headline findings was that 93 percent of participants achieved microdystrophin expression above 10 percent. In the Duchenne field, this threshold is often considered clinically meaningful because higher dystrophin levels may improve muscle stability and reduce degeneration over time.
The company also reported that 80 percent of patients achieved microdystrophin expression above 40 percent, which is considered a remarkably high level for a gene therapy study in DMD.
Find More: AFFINITY DUCHENNE Pivotal Study of RGX-202
However, Important Biomarker Data Were Not Shared
Creatine Kinase (CK), AST, and ALT Data Were Missing
Despite the promising topline results, the press release did not include detailed data on several critical biomarkers, including:
- Creatine Kinase (CK)
- Aspartate Aminotransferase (AST)
- Alanine Aminotransferase (ALT)
This omission is important because these biomarkers are widely used to evaluate muscle damage and liver-related safety concerns in Duchenne muscular dystrophy.
Why Are CK, AST, and ALT So Important in Duchenne?
Creatine Kinase (CK)
CK is one of the most important biomarkers in Duchenne muscular dystrophy. High CK levels indicate ongoing muscle breakdown. If a gene therapy is truly protecting muscle fibers, many experts expect CK levels to decrease over time.
Without CK data, it becomes more difficult to understand whether the therapy is reducing active muscle damage at the biochemical level.
AST and ALT
AST and ALT are commonly known as liver enzymes, but in Duchenne patients they can also rise because of muscle injury. Elevated AST and ALT levels may reflect:
- Ongoing muscle destruction
- Liver inflammation
- Potential treatment-related toxicity
Tracking these biomarkers is especially important in gene therapy trials because liver-related adverse effects remain a major safety concern in the field. Read More: Why CK, AST, and ALT Data Matter
Why Biomarker Transparency Matters
While microdystrophin expression and NSAA improvement are encouraging findings, biomarkers such as CK, AST, and ALT provide another critical layer of evidence regarding how the therapy affects the body biologically.
Families, clinicians, and researchers need transparent biomarker data to better understand:
- Whether muscle damage is truly decreasing
- How durable the therapeutic effect may be
- Whether safety concerns are emerging over time
- How RGX-202 compares with other Duchenne gene therapies
The Duchenne community has waited decades for meaningful therapies. Positive functional data and strong microdystrophin expression are encouraging steps forward, but comprehensive biomarker transparency will be essential for fully evaluating the long-term clinical value and safety profile of RGX-202.
Follow This Page >>> All Clinical Trials for Duchenne
