If approved, it would be the first treatment to address the disease’s skeletal and functional impairments regardless of onset, with biweekly dosing, states the company.

The FDA grants Priority Review to applications for medicines that, if approved, would offer significant improvements over existing treatment options through gains in safety, efficacy, or patient compliance, or by preventing serious conditions. The Prescription Drug User Fee Act (PDUFA) date, marking the FDA’s regulatory decision, is expected in the first half of 2027.

HPP

HPP is a rare, chronic, inherited metabolic disease caused by deficient activity of the enzyme alkaline phosphatase (ALP), leading to defective bone mineralization, impaired calcium and phosphate regulation, and functional impairments such as muscle weakness, neurologic symptoms, fatigue, and pain.

“Today’s Priority Review marks an important step forward for the HPP community and reinforces the potential for efzimfotase alfa to redefine treatment outcomes,” says Marc Dunoyer, CEO of Alexion. “Building on Alexion’s pioneering legacy in HPP and shaped by patient insights, efzimfotase alfa was designed to address the skeletal and functional manifestations of this rare metabolic disease, with the convenience of self-administration every two weeks and five times lower annualized rates of injection site reactions compared to Strensiq.”

Phase 3 clinical programme

The Biologics License Application is based on results from the largest Phase 3 clinical programme in HPP, comprising three trials: HICKORY, in treatment-naïve adolescents and adults; MULBERRY, in treatment-naïve children aged 2 to under 12; and CHESTNUT, in children previously treated with Strensiq (asfotase alfa). Efzimfotase alfa showed a favorable safety profile and was generally well tolerated across all three trials, and earlier-line data from MULBERRY and CHESTNUT were recently presented at the International Conference on Children’s Bone Health, with HICKORY results due at the upcoming American Society for Bone and Mineral Research annual meeting.

Regulatory submissions for efzimfotase alfa based on the three trials are also under review in Japan and other markets.