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When Eliza O'Neill was little, she was one of those kids who always needed to have an accessory, like a hat or a scarf.
"She would always go get my high heels from the closet and clop around in those — which she scared us to death," says her mom, Cara O'Neill, a pediatrician in Columbia, S.C.
But by the time Eliza turned 3, her parents noticed she was falling behind on developmental milestones. She was diagnosed with a pragmatic speech delay, meaning she had learned a lot of words, for example, but she wasn't using them in a typical way in social situations.
In 2013, one of Cara's colleagues suggested testing Eliza for a group of metabolic disorders — just to rule them out.
But the test came back positive for something called Sanfilippo syndrome.
Cara remembered learning about the rare inherited disease back in medical school.
"When they said the word, it all kind of came rushing back," she says. "And it was just this bale of dread, like, oh, my goodness, this is horrific."
Children with Sanfilippo have a faulty gene that leaves them unable to break down heparin sulfate, a molecule critical to normal cell function. As it builds up in the body, it causes severe complications.
Kids with Sanfilippo lose their ability to speak and walk. They have seizures, and they usually don't live past their teens, according to the Cure Sanfilippo Foundation, which the O'Neills started and continue to run.
For Eliza's dad, Glenn O'Neill, it took a little while after learning Eliza's test results for the diagnosis to sink in.
"It wasn't really until I got home that I realized how quickly the degeneration happened," he says. "And that was really the point where we said, 'Gosh. Whatever we need to do, we need to do it now.'"
Researching a treatment
At Nationwide Children's Hospital in Columbus, Ohio, researcher Haiyan Fu had been working on a gene therapy in mice for Sanfilippo since the late-1990s.
The therapy used a modified virus to deliver a working copy of the broken gene to patients' cells.
Fu realized the experimental therapy was promising. "And if we treat early, it could be potentially a cure," she says. "So I can't give up."
Keeping it going – and funded – was challenging, though. She thought she would have to quit in 2009. But the families of kids with Sanfilippo stopped her.
"They said, 'You can't leave. Can we give you some of the funds for you to, you know, carry on?'" Fu recalls, explaining that these families had helped her from the beginning and didn't want to see her work stop.
In all, eight patient foundations, including Ben's Dream and a Cure for Kirby, kept Fu's work going until the research was ready for the first human trial.
Raising the money
But a clinical trial would be expensive. Glenn O'Neill had an idea for how to raise the money.
"We reached out on a whim to some strangers that we found on the internet about making a viral video," he says, referring to filmmaker Benjamin Von Wong, who made them a video over a few days in 2014.
It worked.
In the spring of 2014, the Saving Eliza video helped the O'Neills break GoFundMe's record at the time, raising a million dollars in just a few weeks. Soon, it hit $2 million.
The money raised helped fund the first human trial, which started in May 2016.
The experiments were promising enough for the biotech industry to take notice.
Ultimately, a biotech company called Ultragenyx acquired the rights to the gene therapy in 2022 and kept studying it. A few years later, the company submitted data to the Food and Drug Administration for review.
The FDA approved the gene therapy in September. The one-time infusion is called Fayuvi.
"The treatment will work best the younger the child is because the more brain is remaining," says Ultragenyx CEO Emil Kakkis. "By the time they're 2 or 3 or 4 years old diagnosed, getting figured out, they've lost a lot of ground. And we have treated a few kids that were in the 6-month age that have done really well. And our view is that when you treat them really young, you actually get better gene therapy results."
Ultragenyx set the price for the treatment at nearly $4 million, tying it for the second most expensive gene therapy ever, according to 46brooklyn, a drug price research firm.
Kakkis says Ultragenyx is committed to making sure every patient is treated, regardless of the price. "There should be no logistical location, site or state or other kind of rule that stops us from getting the patient treated. We understand what [we've] got to do."
Moments after the FDA approval was announced, Fu got a call from Cara O'Neill — and messages from other families that funded her research. Some had lost a child along the way.
Fu says Fayuvi's approval is good news, but it brings mixed emotions for her: "It shouldn't take this long."
As for Eliza, she's almost 17 now. She was the very first patient to get the gene therapy as part of a clinical trial back in 2016.
Because she was 6 years old when she was treated with the gene therapy, she had already lost her ability to speak. It never returned, but she can communicate with picture cards and devices. Eliza goes to school. And this summer, she swam and learned to float on a pool noodle.
"I just feel proud of my girl. You know?" Glenn O'Neill says. "I feel proud of her. It's been a rough road for her, but we also know she's very lucky."
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