Springfield Girl, 5, Approved for First Gene Therapy Treatment

For nearly six-year-old Lottie Milburn and her family in Springfield, Illinois, a positive antibody test result means something most families take for granted: more time together.

On October 5, Lottie's parents learned she qualified to receive Fayuvi, the first FDA-approved gene therapy for Sanfilippo syndrome type A. The rare genetic disease progressively damages the brain and nervous system, stealing children's cognitive abilities, language skills, and developmental milestones.

"We're hoping that it will slow and possibly stop the progression of the disease," said Lottie's mom, Abby Milburn. The family is now working with their insurance company to get Lottie treated at St. Louis Children's Hospital.

The approval marks a dramatic turn from just a year ago. In July 2024, Illinois Times first covered the Milburns' desperate search for experimental treatment after Lottie's April diagnosis. She also has Down syndrome, which complicated identifying why she was losing skills she had already learned.

Abby knew to ask about Sanfilippo because a cousin had the disease. Without that family connection, she might never have known what to look for. "The regression was the piece that really worried us," she said.

The FDA approved Fayuvi on September 17, offering hope where none existed before. The treatment uses a modified, harmless virus to deliver a working gene into patients' cells, helping them produce an enzyme their bodies lack. That enzyme breaks down harmful substances driving the disease.

The Ripple Effect

U.S. Rep. Nikki Budzinski wrote to the FDA on the Milburns' behalf, urging faster action. Working with the family inspired her to join the House Rare Disease Caucus, expanding her advocacy to help other families facing similar battles.

"The uniqueness of this rare disease is that time is not on our side," Budzinski said. She's now co-sponsoring legislation to expand early identification of rare diseases through newborn screening.

The Milburns are pushing for widespread Sanfilippo screening for newborns. Early diagnosis could give families a chance to start treatment before children lose skills. "To get that added to the newborn screening would be huge," Abby said.

In clinical studies, treated children maintained or improved cognitive function compared with untreated children. Lottie will receive a one-time intravenous infusion followed by months of monitoring, including at least eight weeks of corticosteroid treatment.

Because Lottie is approaching six, her parents remain cautious about expectations. They hope the treatment will help her hold onto her current abilities and give their family more quality time together with Lottie and her three younger siblings.

The family also sees their milestone as encouragement for other rare disease families. While other forms of Sanfilippo will need their own treatments and approvals, the Milburns believe progress is possible.

A year ago, they were fighting just for the chance to try; today, that chance is becoming real, carrying the promise of more childhood for Lottie and more memories for everyone who loves her.