The U.S. Food and Drug Administration has approved Zycubo, a copper histidinate injection, as the first treatment for children with Menkes disease, a rare inherited disorder that is often fatal in early childhood according to a news release from the agency.

“With today’s action, children with this devastating, degenerative disease will have an FDA-approved treatment option and the potential to live longer,” Christine Nguyen, M.D., Deputy Director of the Office of Rare Diseases, Pediatrics, Urologic and Reproductive Medicine in the FDA’s Center for Drug Evaluation and Research, said in the release. “The FDA will continue to work with the rare disease community to advance drug development for patients with Menkes disease and other rare conditions.”

Per the release, Menkes disease stems from a genetic defect that prevents the body from properly absorbing copper, a mineral needed for brain and nervous system development. The condition leads to seizures and poor growth along with progressive developmental delays and intellectual disability. It can also damage blood vessels, the bladder and bowel as well as bones, muscles and the nervous system. About 90% of patients have the classical form that appears in infancy and most do not live past age 3. The disorder is estimated to affect roughly one in every 100,000 to 250,000 births worldwide and occurs more often in boys.

Zycubo acts as copper replacement therapy administered by subcutaneous injection. It delivers copper in a form that bypasses the intestinal absorption defect so the body can use it.

The FDA said it based its decision on two open-label, single-arm clinical studies in pediatric patients treated for as long as three years. Overall survival was evaluated by comparing 66 treated children with 17 untreated children drawn from contemporaneous external control groups, most in the United States. Children who started therapy within four weeks of birth had a 78% lower risk of death than untreated patients. Nearly half of those early-treated children lived beyond six years and some survived more than 12 years. No untreated patients were alive past six years. Children who began treatment after four weeks of age also showed meaningful survival gains.

Per the release, reported side effects included infections and breathing problems along with seizures, vomiting, fever, anemia and injection site reactions. Because copper can build up in the body, regulators said patients receiving Zycubo should be monitored for toxicity.

“This approval marks an unprecedented advance for children with Menkes disease,” said Tracy Beth Hoeg, M.D., Ph.D., Acting Director of CDER. “The company demonstrated a large improvement in overall survival compared with untreated patients, using an innovative trial design that addressed the challenges of studying an ultra-rare disease.”

The application received Priority Review, Fast Track designation, Breakthrough Therapy designation and Orphan Drug designation the release said. Zycubo was approved for Sentynl Therapeutics.