Clinical Trial Updates from the USA on Becker Muscular Dystrophy and Duchenne Muscular Dystrophy

A lot has happened recently regarding clinical trials for Duchenne Muscular Dystrophy, and Becker Muscular Dystrophy (Hereafter referred to as Duchenne and Becker). All of these updates are from the American Muscular Dystrophy Association Clinical & Scientific Conference in Orlando that took place from March 8th - 11th let’s start with an update from a Becker Trial.

Edgewise Announces Positive Long-Term Sevasemten Data Demonstrating Sustained Functional Stabilisation in Becker Muscular Dystrophy Through 3.5 Years of Follow-Up

Edgewise Therapeutics has presented long-term data from its MESA open-label extension study of sevasemten. The data show participants on sevasemten experienced stabilisation of function over 3.5 years in marked contrast to the functional decline expected from Becker natural history data.

Over 3.5 years: North Star Ambulatory Assessment (NSAA) functional scores of participants treated with sevasemten remained stable after 3.5 years and 2 years, respectively. The participants on placebo who rolled into the MESA study also had NSAA functional scores that trended upward during the first year after switching to sevasemten.

Sevasemten is an investigational fast skeletal myosin inhibitor designed to protect muscle from contraction-induced damage, continued to show a favourable safety profile in MESA with long-term exposure for 3+ years

Joanne Donovan, M.D., Ph.D., Chief Medical Officer of Edgewise Therapeutics Stated: "For the first time with an investigational agent, we are seeing long-term data where individuals with Becker are stable in the face of a disease that we have seen would otherwise lead to a significant functional decline,"

REGENXBIO announced new positive interim data from the Phase I/II AFFINITY DUCHENNE trial of RGX-202,

In the interim functional results from seven participants treated at the pivotal dose level (2x1014 GC/kg), aged approximately 6 to 12 years at dosing, RGX-202 continues to demonstrate evidence of positively impacting disease trajectory on North Star Ambulatory Assessment (NSAA) and all timed function tests (Time to Stand, 10 Meter Walk-run, Time to Climb) at one year.

Functional outcomes were analysed using multiple validated methods to estimate expected disease progression without treatment, including a disease progression model and external control comparisons. The pivotal dose participants demonstrated improved performance across all timed function tests and NSAA when compared to external control.

Steve Pakola, M.D., Chief Medical Officer of REGENXBIO, stated: "Today's new Phase I/II interim data demonstrates continued positive impact on function, stable cardiac health, and a favorable safety profile, highlighting the potential of RGX-202 to be a differentiated gene therapy option for Duchenne,"

Solid Biosciences Shares Interim Positive Update on Phase 1/2 INSPIRE DUCHENNE Trial

Solid Biosciences has shared updated positive interim data from the ongoing Phase 1/2 INSPIRE DUCHENNE clinical trial of SGT-003. The new data, including additional muscle biopsy, serum biomarker, cardiac function, and safety analyses, add to a growing dataset that suggests the potential of the biological activity of SGT-003 microdystrophin therapy.

INSPIRE DUCHENNE is a Phase 1/2 first-in-human, open-label, single-dose, multicenter trial designed to evaluate the safety, tolerability and efficacy of SGT-003 in pediatric participants with Duchenne, SGT-003 is administered as a one-time IV. The interim clinical data reported in this release are as of a February 23, 2026, data cutoff date.

SGT-003 has been generally well tolerated in the 40 participants dosed as of March 11, 2026. The trial is being conducted at 15 clinical sites across the US, Canada, Italy and the United Kingdom and participant dosing remains ongoing.

Bo Cumbo, President and CEO of Solid Biosciences stated: “These data continue to suggest that SGT-003 may be having a disease-relevant treatment effect… Together with the promising safety and tolerability profile, these interim results reinforce our confidence in the potential of SGT-003 to meaningfully impact the disease course of Duchenne. Our focus remains on urgently advancing SGT-003 to provide the Duchenne community with an additional therapeutic choice.”

Genethon confirms two-year efficacy in patients treated with its drug candidate GNT0004 at therapeutic dose in the first phase of its clinical trial.

Genethon, a pioneer and leader in gene therapy for rare diseases, unveiled results at the confirming the long-term efficacy of its GNT0004 gene therapy in Duchenne muscular dystrophy in patients treated at therapeutic doses in the first phase of an international multicenter clinical trial it is sponsoring.

The clinical trial, conducted by Genethon, includes boys aged 6 to 10 with Duchenne muscular dystrophy who can still walk. In the phase before the ongoing pivotal phase, five patients were treated with GNT0004, four in France and one in the United Kingdom, including two patients at the first dose and three at the second dose level.

The data presented, based on long-term follow-up of the three patients treated at the second dose level, confirm the maintenance of clinical efficacy at two years across various parameters.

This included a significant gain in motor function as measured by the North Star Ambulatory Assessment (NSAA), Clinical benefit maintained at 2 years, with improvement across all timed tests, A significant and sustained reduction in CPK levels (a biomarker of muscle damage) by an average of 70% at 2 years (compared to the patient's baseline condition before treatment), and A slowdown in disease progression, as demonstrated by imaging,

Most of these trials are years away from being available to people with Duchenne and Becker, and hopefully, the European and Irish Goverments fast track these treatments once they are available in the UK and US.