FDA Approved First Gene Therapy for Sanfilippo Syndrome
The newly authorized treatment targets the underlying enzyme deficiency in infants born with the rare, progressive condition.
Updated on Oct. 10, 2026 in Special Needs
In September 2026, federal regulators approved a gene therapy treatment designed to prevent complications from Sanfilippo syndrome. The rare condition, which impacts 1 in 70,000 children, is caused by a genetic change that disrupts vital enzyme production.
Why it matters
This approval marks a significant medical shift by targeting the disease at its source, potentially preventing the degenerative decline common in affected children. However, the therapy is limited to infants and does not provide an option for older children whose disease has already progressed.
While the therapy is a major milestone, it is not approved for children like Mickey Merrill, who was diagnosed at age 3 and requires daily medication. The syndrome affects 1 in 70,000 children, with most diagnosis cases occurring in early childhood.
The players
U.S. Food and Drug Administration
The federal agency responsible for protecting public health by ensuring the safety and efficacy of medical treatments and therapies.
Declan Merrill
A five-year-old boy who received experimental gene therapy for Sanfilippo syndrome as an infant and currently attends kindergarten.
Mickey Merrill
A child diagnosed with Sanfilippo syndrome at age 3 who is currently ineligible for the newly approved gene therapy.
The details
The treatment works by addressing the gene change that prevents the body from producing necessary enzymes. Doctors inject the therapy directly into infants to restore normal enzyme production before significant damage occurs. Because the syndrome is progressive, the therapy was not tested on or approved for older children whose internal damage is already advanced.
Timeline
Five years ago, Declan Merrill received experimental gene therapy in Ohio.
The FDA approved the gene therapy treatment in September 2026.
The Merrill family is hosting the Chefs Unite fundraiser on November 2, 2026.
The Home Front
This development represents a major shift in the medical management of rare genetic disorders, mirroring an increasing regulatory focus on early-intervention gene therapies. It highlights the growing divide in available care options for families based on the child's age at the time of diagnosis.
Families with a recent diagnosis of Sanfilippo syndrome should consult their pediatric specialist to discuss if the newly approved therapy is a viable option based on the child's age. Parents should maintain thorough records of genetic testing and enzyme studies to facilitate discussions with medical professionals.
The takeaway
While the new therapy offers a path for infant treatment, the disease remains a significant challenge for older children who require ongoing daily care. Families currently managing the condition often rely on community-led fundraising efforts, such as the upcoming Chefs Unite event on November 2, 2026.
Further reading
For more information on navigating resources for rare conditions, visit our Special Needs section.
Source note: This article includes information reported by Spotlight Delaware.
