Mobility and Quality of Life in Adults with Paediatric-Onset Hypophosphatasia Treated with Asfotase Alfa: Results from UK Managed Access Agreement.

INTRODUCTION

Hypophosphatasia (HPP) is a rare disease caused by deficient tissue-non-specific alkaline phosphatase (ALP) activity. Asfotase alfa is a tissue-non-specific ALP enzyme-replacement therapy which was reimbursed in the UK under a Managed Access Agreement (MAA). This analysis assessed safety and effectiveness of asfotase alfa in adults with HPP.

METHODS

This prospective, observational data collection included adults with paediatric-onset HPP enroled in the MAA and treated with asfotase alfa for ≥ 6 months to 5 years. Assessments included mobility, pain, and health-related quality of life (HRQoL), each reported at regular intervals through year 3. Analgesic use, fractures, and events of interest (EOIs) were each reported continuously throughout follow-up.

RESULTS

Of 28 enroled treated adults, 24 were assessed for effectiveness. Distance walked in the 6-Minute Walk Test was median (min, max) 172.5 m (0.0, 380.0; n = 24) at baseline and improved by 157.3 m (- 171.0, 479.5; n = 16) at month 6; results were sustained throughout follow-up. Median (min, max) Bleck score was 6.0 (2.0, 9.0; n = 24) at baseline and increased to 6.5 (5.0, 9.0; n = 10) at month 36. Median (min, max) aggregate Brief Pain Inventory Short Form severity score was 8.0 (4.3, 10.0; n = 24) at baseline and improved to 4.4 (1.0, 7.8; n = 10) at month 36. During follow-up, 8 participants (33.3%) decreased or discontinued opioid use throughout follow-up and 4 (16.7%) reported fractures. Median (min, max) EQ-5D-3L utility scores improved from 0.21 (- 0.26, 0.60; n = 24) at baseline by 0.15 (- 0.36, 0.91; n = 24) at month 6 and were similar throughout follow-up. Injection site reactions were the most common treatment-related EOI, reported in 17 participants (60.7%). Three participants reported treatment-related serious adverse events.

CONCLUSION

Asfotase alfa treatment improved mobility, physical function, pain, and HRQoL and was well tolerated. These data show the benefit of asfotase alfa in adults with paediatric-onset HPP.