FDA clears $4 million Sanfilippo gene therapy

COLUMBUS. The U.S. Food and Drug Administration approved a new gene therapy for Sanfilippo syndrome on September 30, 2026. The one-time infusion, named Fayuvi, treats children with a rare inherited disorder that destroys brain tissue. The approval follows clinical trials that began at Nationwide Children's Hospital in 2016.

Haiyan Fu, a researcher at Nationwide, developed the therapy using a modified virus to deliver a working gene to patients. She began working on the treatment in mice in the late 1990s. Fu stated that early treatment could potentially act as a cure. She faced funding challenges in 2009 but continued the work after patient families provided financial support.

The therapy was funded by eight patient foundations, including Ben's Dream and a Cure for Kirby. Glenn O'Neill, father of the first patient, helped raise the capital needed for the human trial. In 2014, the family launched a viral video campaign with filmmaker Benjamin Von Wong. The effort broke GoFundMe's record at the time, raising $1 million in weeks before reaching $2 million.

Eliza O'Neill was the first person to receive the gene therapy in May 2016. She was 6 years old at the time. Eliza was diagnosed with Sanfilippo syndrome at age 3. The disease prevents the body from breaking down heparin sulfate, causing seizures and loss of speech and mobility. Most children with the condition do not live past their teens, according to the Cure Sanfilippo Foundation.

Eliza's mother, Cara O'Neill, is a pediatrician in Columbia, S.C. She said the diagnosis brought back memories of the disease from her medical school days. Glenn O'Neill said the family decided to act immediately after understanding the speed of the degeneration. He noted that the treatment was a long road for his daughter, but she is now almost 17 years old.

Biotech company Ultragenyx acquired the rights to the therapy in 2022. The company submitted data to the FDA for review before the recent approval. Ultragenyx CEO Emil Kakkis said the treatment works best in younger children because more brain tissue remains. He noted that patients treated at 6 months of age showed strong results.

Ultragenyx priced Fayuvi at nearly $4 million. A drug price research firm named 46brooklyn listed this as the second most expensive gene therapy ever approved. Kakkis said the company will treat every eligible patient regardless of location or state rules. He emphasized that logistical barriers should not stop patients from receiving care.

Eliza lost her ability to speak before receiving the treatment in 2016. The speech did not return, but she communicates using picture cards and devices. She attends school and learned to float on a pool noodle this summer. Fu received a call from Cara O'Neill moments after the FDA announcement. Fu said the approval brings mixed emotions because the process took too long.