Mobility and quality of life in children with paediatric-onset hypophosphatasia treated with asfotase alfa: results from UK managed access agreement

Introduction

Hypophosphatasia (HPP) is a rare, inherited metabolic bone disease with a high degree of morbidity and mortality in children. Asfotase alfa is an enzyme replacement therapy for HPP reimbursed in the UK since 2017 under a Managed Access Agreement (MAA). This analysis assessed the effectiveness and safety of asfotase alfa in children < 18 years of age.

Methods

The MAA was a prospective, longitudinal data collection in children with paediatric-onset HPP. Effectiveness outcomes were evaluated in children who were treated with asfotase alfa for ≥ 6 months. Data were collected on respiratory support, growth, mobility, motor development, analgesic use, quality of life, and safety at enrolment and throughout the 5-year MAA.

Results

Twenty-four children enrolled in the MAA and 20 were included in the analysis. Twelve children had received asfotase alfa before enrolment through a clinical trial or compassionate use program. From baseline to month 60, the median (minimum, maximum) change in height and weight Z-scores were 0.20 (− 0.9, 1.2; n = 6) and − 0.5 (− 1.9, 1.5; n = 6), respectively. The median (minimum, maximum) percent of predicted distance walked in the 6-Minute Walk Test increased by 3.8% (− 8.6, 4.3; n = 5) at month 3 and was sustained through follow-up. Median (minimum, maximum) child- and parent-reported Pediatric Quality of Life Inventory scores were 59.2 (15.2, 91.3; n = 11) and 53.4 (16.3, 100.0; n = 18) at baseline and increased by 21.7 (5.4, 37.0; n = 3) and 16.3 (9.8, 45.7; n = 4) at month 60, respectively. Treatment-naïve children had a greater clinical response than treatment-experienced participants, who maintained their status. No deaths occurred in the study. The most common adverse events were injection site reactions, reported in 8/24 participants (33.3%).

Conclusion

This analysis confirmed the clinical benefit of asfotase alfa in children with HPP. Asfotase alfa was well tolerated, with no new safety signals identified.