O'Neill family funding drove Sanfilippo gene therapy to FDA approval

The O'Neill family of Columbia, S.C., provided the financial engine that moved a rare disease gene therapy from mouse studies to an FDA approval in September 2026. The therapy, named Fayuvi, treats Sanfilippo syndrome, a genetic condition that causes severe developmental decline in children.

Eliza O'Neill was diagnosed with the disorder at age 3 in 2013 after a routine metabolic test suggested a rule-out. Her mother, Cara O'Neill, a pediatrician, recognized the name from medical school. The diagnosis meant Eliza had a faulty gene preventing her body from breaking down heparin sulfate, a molecule essential for cell function. According to the Cure Sanfilippo Foundation, which the family started, children with the condition typically lose the ability to speak and walk and rarely survive past their teenage years.

Haiyan Fu at Nationwide Children's Hospital in Columbus, Ohio, had been developing a gene therapy for the disease in mice since the late 1990s. The treatment uses a modified virus to deliver a working copy of the broken gene to patient cells. Fu believed early intervention could serve as a cure. However, she nearly abandoned the project in 2009 due to lack of funding. Patient families, including the O'Neills, intervened. Eight patient foundations, such as Ben's Dream and a Cure for Kirby, contributed funds to keep the research active until it was ready for human trials.

To finance the first human trial, Glenn O'Neill, Eliza's father, reached out to filmmaker Benjamin Von Wong in 2014. Von Wong created a video titled Saving Eliza over several days. The campaign broke the then-record on GoFundMe, raising $1 million in a few weeks. The total eventually reached $2 million. These funds directly supported the clinical trial that began in May 2016.

The initial results attracted biotech attention. In 2022, Ultragenyx acquired the rights to the therapy and continued its development. The company submitted data to the Food and Drug Administration for review. The agency approved Fayuvi in September 2026. Emil Kakkis, CEO of Ultragenyx, stated that the treatment yields better results when administered to younger children who have retained more brain function. He noted that patients treated at six months of age have shown strong outcomes.

Ultragenyx priced Fayuvi at nearly $4 million per patient. According to 46brooklyn, a drug price research firm, this ties it for the second most expensive gene therapy ever. Kakkis said the company aims to treat patients regardless of logistical or geographic barriers. "There should be no logistical location, site or state or other kind of rule that stops us from getting the patient treated," he said.

Eliza O'Neill was the first patient to receive the therapy in the 2016 trial. She was six years old at the time and had already lost her ability to speak. The speech capability did not return, but she now communicates using picture cards and electronic devices. She attends school and spent the summer learning to float on a pool noodle. Her father said she is very lucky despite the difficult path she has faced.

Fu received a call from Cara O'Neill immediately after the FDA announcement. Messages also arrived from other families who had funded her research, some of whom had lost children to the disease. Fu described the approval as good news mixed with the realization of how long the process took. "It shouldn't take this long," she said.