FDA Approves $4 Million Gene Therapy for Rare Disease After Family Funded Research

The Food and Drug Administration approved Fayuvi, a one-time gene therapy for Sanfilippo syndrome, in September. The treatment carries a price tag of nearly $4 million, placing it as the second most expensive gene therapy available, according to the drug price research firm 46brooklyn.

Sanfilippo syndrome is a rare inherited disorder caused by a faulty gene that prevents the body from breaking down heparin sulfate. The molecule builds up in cells, leading to severe neurological decline. Children with the condition typically lose the ability to speak and walk and face a life expectancy that rarely extends past their teenage years.

Eliza O'Neill was diagnosed with the condition at age 3 in 2013. Her mother, Cara O'Neill, a pediatrician in Columbia, S.C., recalled the diagnosis as a moment of deep dread. Her father, Glenn O'Neill, said the family decided immediately to pursue any available options. They connected with Haiyan Fu, a researcher at Nationwide Children's Hospital in Columbus, Ohio, who had been developing a gene therapy in mice since the late 1990s.

Fu’s work stalled in 2009 when funding ran low. She considered leaving the project until families of affected children intervened. Eight patient foundations, including Ben’s Dream and A Cure for Kirby, provided the capital needed to continue the research. Glenn O'Neill later helped secure additional funds by commissioning a viral video from filmmaker Benjamin Von Wong in 2014. The video, titled Saving Eliza, broke GoFundMe’s record at the time, raising $1 million in a few weeks and eventually reaching $2 million.

Those funds supported the first human clinical trial, which began in May 2016. Eliza O'Neill was the first patient to receive the infusion. In 2022, biotech company Ultragenyx acquired the rights to the therapy and continued its development before submitting data to the FDA.

Ultragenyx CEO Emil Kakkis stated that the therapy works best when administered to young children because more brain function remains. He noted that patients treated at six months of age have shown strong results. Kakkis added that the company aims to ensure patients receive treatment regardless of logistical barriers or cost.

Eliza O'Neill was six years old when she received the treatment, meaning she had already lost her speech. While her verbal ability did not return, she now communicates using picture cards and devices. She attends school and learned to float on a pool noodle this summer. Fu, who received calls from the O'Neill family and other supporters immediately after the approval announcement, described the moment as bittersweet, noting that the process took too long.