US-based Ultragenyx Pharmaceutical has started enrolment in the Phase II trial of the human monoclonal anti-FGF23 antibody KRN23 (UX023) in pediatric patients with X-linked hypophosphatemia (XLH).
XLH is an inherited metabolic bone disease characterised by short stature, skeletal deformities, bone pain, fractures and muscle weakness.
The multi-centre, randomised, open-label, dose-finding Phase II trial is designed to assess the safety and efficacy in around 30 prepubertal pediatric XLH patients.
Ultragenyx said that preliminary clinical effects of KRN23 treatment on bone health and deformity as measured by radiographic assessments, growth, muscle strength, and motor function will also be assessed, as well as markers of bone health and patient-reported outcomes of pain, disability, and quality of life.
The trial has been assessed and accepted for conduct by the US Food and Drug Administration (FDA), the UK Medicinal and Health Regulatory Authority (MHRA), and the Dutch Medicines Evaluation Board (CBG-MEB).
Ultragenyx chief executive officer Emil Kakkis said: "Completed studies in adults with XLH show KRN23's effect in increasing phosphate levels and bone remodelling.
"Due to the high rate of growth and bone formation during childhood and the critical role phosphate plays in bone mineralisation, pediatric patients with XLH may have the greatest potential for improvement from treatment with KRN23."
The Phase II trial will include a 16-week individual dose-titration period followed by a 48-week treatment period.
The main aim of the dose-titration period is to identify the individualised dose of KRN23 required to achieve stable serum phosphorus levels in the target range.
In the trial, patients will be divided into three groups of escalating starting dose levels of KRN23 with either monthly or biweekly dosing regimens.
Image: Image showing inheritance of X-linked dominant mutation from an affected mother. Photo: courtesy of PD-USGOV-HHS-NIH.