Regenxbio, Solid report data with Duchenne gene therapies

This week saw both Regenxbio and Solid Bio report new data with their gene therapy candidates for Duchenne muscular dystrophy (DMD), vying to join Sarepta's Elevidys on the market.

Regenxbio gave an update on the phase 2/3 AFFINITY DUCHENNE trial of its RGX-202, reporting interim results that showed it was well tolerated, achieved robust expression of microdystrophin to replace the mutated dystrophin protein in DMD, and led to early functional improvements in ambulatory DMD patients aged one and over.

The data, from seven subjects in the study treated with the target dose of RGX-202, showed that their motor function 12 months later – measured using the North Star Ambulatory Assessment (NSAA) scale and timed function tests – was improved compared to matched external natural history comparisons and predictive modelling.

The results also showed that patients demonstrated cardiac stability at one year post-treatment as measured by MRI endpoints, an important finding as DMD causes progressive cardiac muscle degeneration (cardiomyopathy).

The company is now expecting to report pivotal data from the study in the second quarter of this year, and said it will ask for a meeting with the FDA to look at possible pathways toward filing RGX-202 for accelerated approval while it runs an ongoing confirmatory study.

Solid Bio, meanwhile, reported this week that its SGT-003 candidate had also achieved strong expression of microdystrophin, along with improvements in muscle integrity, including stabilisation and improvement in cardiac function in its phase 1/2 INSPIRE DUCHENNE trial.

For now, the investigators remain blinded to the motor function data in the study, which has now enrolled 40 subjects. Solid Bio said it is hoping to schedule meetings with the FDA in the first half of this year to seek guidance on accelerated approval, and indicated that it already has an agreement with the agency on the design of a phase 3 trial that will be called IMPACT DUCHENNE and is due to start dosing patients before the end of this month.

Both companies are hoping to provide an alternative one-shot treatment to Elevidys, which was launched in 2023, but ran into trouble last year after three fatalities were reported in non-ambulatory DMD recipients, leading to a pause in distribution.

The fatalities, linked to liver toxicity, eventually resulted in Elevidys' label being restricted to ambulatory patients only, but did not stop the product knocking on the door of blockbuster status last year, with sales of $899 million.

Regenxbio and Solid Bio have both pointed to the safety profile of their gene therapies, saying there was no evidence of liver injury in their trial updates. The two studies were presented at the 2026 Muscular Dystrophy Association (MDA) annual meeting earlier this week.