New Drug Options Abound for Duchenne Muscular Dystrophy

SAVANNAH, Ga. — When Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, pediatric neurologist Nancy L. Kuntz, MD, was a fellow about 45 years ago, there were few more devastating diagnoses than Duchenne muscular dystrophy (DMD).

“The rule of thumb was that they would stop walking by age 10 and probably die around age 20, and there was not much we could do,” Kuntz told colleagues at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) 2024.

Now, the landscape of DMD therapy is transforming at a rapid pace. “In the last 8 years, we’ve seen eight different therapies that are FDA-approved specifically for Duchenne, and many more are in the pipeline,” said session moderator Kathryn Mosher, MD, a pediatric physical medicine and rehabilitation physician at Akron Children’s Hospital, Akron, Ohio.

This is both good news and a new challenge for clinicians: Which of these treatments are best for which patients? Kuntz said the traditional therapy of corticosteroids is still crucial. However, “there are still families begging to not use steroids, or refusing to use steroids, just not filling the prescriptions,” she said.

Beware of Parents Who Reject Steroids

The failure to use steroids “breaks your heart” because data show their impact on “really important functions like walking and being able to get up from the ground,” she said. “You can add months and years to life with this treatment.”

However, “while we have shown that using corticosteroids makes a difference, I don’t think that we’ve really worked out the best age at which to start the steroids, or the dosing schedule, or even the type of steroids,” she cautioned.

In an accompanying presentation about therapy for DMD, pediatric neurologist Craig M. Zaidman, MD, of Washington University in St. Louis, St. Louis, Missouri, cautioned that “daily steroids make a big impact on your growth and particularly on your height.”

In particular, the corticosteroid deflazacort has been linked to more cataracts than prednisone and less weight gain and height growth. “They really don’t grow, they don’t get taller, and they also don’t gain weight. They look like little boys when they’re 13 years old.”

Deflazacort or Vamorolone?

Vamorolone (Agamree) is a cheaper corticosteroid alternative to deflazacort (Emflaza), and a 2024 study showed no difference in functional outcomes over 48 weeks, he said. Also, daily vamorolone does a better job of preserving height growth than daily prednisone, he said, and he’s seen less risk for vertebral fractures.

Where do newer drugs fit in? One crucial thing to know about the new generation of targeted therapies is that they’re often mutation-dependent, Kuntz said. They may only work in patients with certain mutations, or mutations may lead to more side effects.

“You should have the exact mutation of your patient, and then you can look and see what they’re eligible for,” she said.

$700,000 a Year for Givinostat

Zaidman highlighted the newly approved givinostat (Duvyzat), a histone deacetylase inhibitor approved for boys 6 years or older. The cost is $700,000 a year, he said, and it’s been linked to less decline in four-stair climb per a double-blind, placebo-controlled, phase 3 trial.

The drug can cause side effects such as reducing platelets, boosting triglycerides, and inducing gastrointestinal problems. “When you drop the dose, these problems go away,” he said.

Does givinostat work? While trial data are challenging to interpret, it does suggest that patients “will lose skill, but they might not lose two or three skills they otherwise would have,” Zaidman said. “To me, that’s quite compelling.”

As for exon-skipping therapies, another new-generation option for DMD, he noted that “these drugs are on the market based on their accelerated approval. We will never have the perfect phase 3, randomized, controlled, long-term trial for these. It’s just not going to come. This is what we get.”

Mosher disclosed the advisory board (Sarepta Therapeutics, Pfizer, Reata Pharmaceuticals, and PTC). Kuntz disclosed advisory board (Astellas Pharma, Inc., argenx, Catalyst, Entrada Therapeutics, Genentech, and Novartis), exchange expert on-demand program (Sarepta Therapeutics), speaker (Genentech, Sarepta Therapeutics, and Solid), and research funding (Astellas Pharma, Inc., argenx, Biogen, Catalyst, Genentech, Novartis, and Sarepta Therapeutics). Zaidman disclosed speaking/advisor/consulting (Sarepta Therapeutics and Optum) and research funding (Novartis and Biogen).