In an infusion bay at UPMC Children’s Hospital of Pittsburgh, Billy Ellsworth twists the plastic top off of a bottle of Gatorade. “That was kind of tough, to be honest,” he said. “I wasn’t sure I was going to get it.”

Billy has Duchenne muscular dystrophy, a genetic disease that causes progressive muscle weakness and affects about one in 3,600 boys. That he can still remove the cap from a Gatorade bottle at age 25 is a feat so notable that his mother is videotaping it to inspire others.

It’s a testament to the infusions of the drug eteplirsen that he has received nearly every single week for the last 16 years. Billy was one of 12 original participants in the clinical trial in 2011. Almost exactly a decade ago, it became the first drug ever approved in the U.S. for muscular dystrophy.

Duchenne muscular dystrophy is fatal, and there is still no cure. To this point, however, eteplirsen has worked wonders for Billy. The question is how far it can take him.

“The bottom line is, he’s still defying Duchenne,” said his mother, Terri Ellsworth, of Kennedy. “He still brushes his hair, changes his own clothes, washes himself. He’s still doing these everyday activities. I don’t want to brag about it, but I want to give other families hope that this drug is still working.”

Billy’s story with Duchenne started about two decades ago. In preschool, his parents noticed that he was a little clumsy, but didn’t think much of it: He could walk and climb and keep up with the other kids. However, a preschool teacher suggested getting him evaluated for his gross motor skills; at first, even the evaluators didn’t notice anything unusual. But when one of them asked Billy to climb stairs, Terri could see a look of concern.

Billy began doing more tests, and all signs seemed to point to a diagnosis of Duchenne. Terri remembers her despair when she searched for information on the disease.

“The more you read, the worse it got,” she said. “The heart and lungs are a muscle, so they go into respiratory failure and they need help breathing and they die young. It was just so ugly and sad. I remember crying my eyes out.”

But at the official doctor’s appointment when Billy was diagnosed, she felt a little better. They met with Henry Wessel, who was near retirement age at the time and died in 2019. While it was true that there were no treatments for the disease at that time beyond steroids, he said there were breakthroughs on the horizon. “There are a lot of trials coming down the pike,” he told her. “You’ll want to keep your ears open to something called exon skipping.”

Duchenne muscular dystrophy occurs when babies are born with a genetic glitch that doesn’t allow their bodies to make a protein called dystrophin, which protects muscle fibers.

“Even though babies are born with it, they can still achieve walking,” said Hoda Abdel-Hamid, a pediatric neurologist at Children’s who has been Billy’s doctor since he was 4 years old. “But then, with walking and with any movements and muscle contractions, they actually start losing the muscles and having more damage to the muscles. Usually by a certain age, they lose ambulation, but also they get cardiac and respiratory complications that can be devastating.”

Typically, people with Duchenne muscular dystrophy lose the ability to walk in their late pre-teen or early teen years. In the years after they stopped walking, they would lose strength in their upper bodies as well, and, eventually, in their lungs and hearts. One study found that the average life expectancy for Duchenne patients born between 1990 and 1999 was 24 years old.

Eteplirsen is known as an exon-skipping drug because it works by skipping over the exon, or section of the DNA, that has the genetic glitch, patching the genetic instructions to allow the body to produce a version of dystrophin. The drug doesn’t cure the disease, but it can significantly slow the progressive decline. Studies have found a higher life expectancy, higher age of ambulation and fewer cardiovascular complications in those taking exon skipping drugs.

The Food and Drug Administration initially rejected the drug, and approved it after a massive movement from parents such as Terri Ellsworth. A documentary looking back at those efforts, “The First Stories that Changed Duchenne,” will be released later this fall.

Eteplirsen only treats one genetic variant of Duchenne and, while it is the most common, it is only present in 13% of Duchenne patients. Since FDA approval of eteplirsen a decade ago, several other exon-skipping drugs have become available for different variants, as well as other genetic therapies. “Over the past 10 years, there’s been a kind of explosion in how many treatment options we can offer to our patients,” said Abdel-Hamid.

Billy was walking until past age 21, when he had a couple accidents — slipping on ice and falling on a threshold — that resulted in him breaking both femurs. He has been in a wheelchair since, but still does exercises to maintain his leg strength. His lungs are almost perfect, said his mother, and his upper body strength is still good, though his heart does have signs of disease.

Billy graduated from Montour High School and completed some college courses. He spends his free time playing video games and watching anime, and learning about classic cars.

He’s come a long way since he would hide from Abdel-Hamid when he visited the doctor.

“We had to pretend, ‘Where’s Billy?’” she said, as they would pantomime searching for him. “And then here we are, and he’s 25. It’s hard to believe, but it’s been amazing.”

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