Phase 3 Study of ALXN1850 in Pediatric Participants With HPP Previously Treated With Asfotase Alfa

Participation Requirements

• Sex:

  ALL

• Eligible Ages:

  2 to 11

Participation Criteria

Inclusion Criteria:

* Diagnosis of HPP documented in the medical records
* Presence of open growth plates by X-ray during Screening Period
* Tanner stage 2 or less during the Screening Period
* Must have been treated with 6 mg/kg/ week of asfotase alfa via SC injection administered as either 2mg/kg 3 times per week or 1 mg/kg 6 times per week for ≥ 6 months before Day 1. Note: participants currently treated with 9 mg/kg (eg, 3 mg/kg 3 times per week) will not be allowed in the study.

Exclusion Criteria:

* History or presence of cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrinological, hematological, neurological disorders, or any other disorders that are capable of significantly altering the absorption, metabolism, or elimination of drugs; constituting a risk when taking the study intervention; or interfering with the interpretation of data as determined by the Investigator.
* Diagnosis of primary or secondary hyperparathyroidism
* Hypoparathyroidism, unless secondary to HPP
* Any new fracture within 12 weeks before Day 1 (excluding pseudofractures)
* Planned surgical intervention which may impact the results of study assessments (in the opinion of the Investigator) during the Randomized Evaluation Period
* History of allergy or hypersensitivity to any ingredient contained in asfotase alfa or ALXN1850
* Body weight \< 10 kg during the Screening Period