Fayuvi: The $4 Million Gene Therapy That Started With One Family's GoFundMe

Eliza O'Neill is 17 years old.

Her parents, Cara and Glenn O'Neill, received her diagnosis in 2013 when she was three. Medical tests revealed she had Sanfilippo syndrome, a rare inherited disease caused by a faulty gene. The condition prevents the body from breaking down heparin sulfate, a molecule essential for normal cell function. As the molecule accumulates, it causes severe physical and cognitive decline. According to the Cure Sanfilippo Foundation, which the O'Neills founded, children with the disease typically lose the ability to speak and walk and often do not survive past their teens.

Research into a cure had stalled in 2009. Haiyan Fu, a researcher at Nationwide Children's Hospital in Columbus, Ohio, had been developing a gene therapy in mice since the late 1990s. The therapy uses a modified virus to deliver a working copy of the broken gene to patient cells. Fu considered quitting when funding dried up, but eight patient foundations, including Ben's Dream and a Cure for Kirby, intervened. These groups provided the financial support necessary to keep the research alive until it was ready for human trials.

The first human trial began in May 2016, but the clinical work required substantial capital. In the spring of 2014, Glenn O'Neill contacted filmmaker Benjamin Von Wong to create a viral video for a GoFundMe campaign. The video, titled Saving Eliza, broke the platform's record at the time by raising $1 million in a few weeks. The total eventually reached $2 million. This funding helped launch the clinical trial that would test the therapy in humans.

The biotech company Ultragenyx acquired the rights to the therapy in 2022 and continued its development. In September 2026, the Food and Drug Administration approved the one-time infusion, named Fayuvi. Emil Kakkis, the CEO of Ultragenyx, stated that the treatment yields the best results when administered to younger children, specifically those under the age of two or three, because more brain function remains. The company set the price for the therapy at nearly $4 million, making it the second most expensive gene therapy ever, according to the drug price research firm 46brooklyn. Kakkis said the company aims to ensure no logistical or geographic barriers prevent a patient from receiving the treatment.

Eliza O'Neill was the first patient to receive Fayuvi during the 2016 trial. At the time, she was six years old and had already lost her ability to speak. While her speech did not return, she now communicates using picture cards and devices. She attends school and learned to float on a pool noodle while swimming this summer. Fu, the original researcher, received a call from Cara O'Neill immediately after the FDA announcement. Fu noted that while the approval is good news, she feels it took too long to reach this point.