Phase 3 Study of ALXN1850 in Treatment-Naïve Pediatric Participants With HPP

Phase 3

Recruiting

• Conditions: Hypophosphatasia
• Interventions: Drug: ALXN1850; Drug: Placebo

• Registration Number: NCT06079359
• Lead Sponsor: Alexion Pharmaceuticals, Inc.

Brief Summary

The primary purpose of this study is to evaluate the efficacy of ALXN1850 versus placebo on radiographic outcomes in pediatric participants with HPP who have not previously been treated with asfotase alfa.

Detailed Description

Not available

Study Timeline

• Study First Submitted: 2023-10-06
• Study First Submitted QC: 2023-10-06
• Study First Posted: 2023-10-12
• Study Start: 2024-05-14
• Status Verified: 2025-05
• Last Update Submitted: 2025-05-19
• Last Update Posted: 2025-05-21
• Primary Completion: 2026-01-21
• Study Completion: 2028-08-21

Recruitment & Eligibility

• Status: RECRUITING
• Sex: All
• Target Recruitment: 30

Inclusion Criteria

• Diagnosis of HPP documented in the medical records, and the following criteria fulfilled without other probable cause than HPP:

  1. Presence of HPP-related rickets on skeletal X-rays during the Screening Period, with a minimum Rickets Severity Score (RSS) of 1.0 AND
  2. Serum ALP activity below the age- and sex-adjusted normal range during the Screening Period as measured by the Central Laboratory OR 2 documented serum ALP activity results, at least 15 days apart, below the age- and sex-adjusted local laboratory normal range during the 24 months before the Day 1 Visit. Note: Local laboratories need to be Clinical Laboratory Improvement Amendments (CLIA) or ISO 15189 certified, or have other local equivalent laboratory certification with Alexion's approval.

• Must meet 1 of the following criteria:

  1. Documented ALPL gene variant (pathogenic, likely pathogenic, or variant of unknown significance) from a CLIA certified laboratory (Section 8.7)
  2. Plasma PLP above the upper limit of normal (ULN) during the Screening Period (central or local laboratory results allowed per local regulations)

• Tanner stage 2 or less during the Screening Period

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 ALXN1850 or the placebo comparator

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
ALXN1850	ALXN1850	Starting at Day 1 of the Randomized Evaluation Period, the ALXN1850 group will receive bodyweight dependent doses of either 20mg, 35mg or 50mg of ALXN1850 once every 2 weeks (q2w) via SC injection, for 24 weeks. Participants will enter the OLE Period and continue q2w dosing with ALXN1850 for up to 132 weeks.
ALXN1850	Placebo	Starting at Day 1 of the Randomized Evaluation Period, the ALXN1850 group will receive bodyweight dependent doses of either 20mg, 35mg or 50mg of ALXN1850 once every 2 weeks (q2w) via SC injection, for 24 weeks. Participants will enter the OLE Period and continue q2w dosing with ALXN1850 for up to 132 weeks.
Placebo	Placebo	Starting at Day 1 during the Randomized Evaluation Period, participants will receive placebo q2w for a total of 24 weeks. Participants will enter the OLE Period and continue q2w dosing with ALXN1850 for up to 132 weeks.

Primary Outcome Measures

Name	Time	Method
Radiographic Global Impression of Change (RGI-C) Score at the end of the Randomized Evaluation Period (Day 169)	Day 169

Secondary Outcome Measures

Name	Time	Method
RGI-C Responder at the end of the Randomized Evaluation Period (Day 169)	Day 169
Change from Baseline in Rickets Severity Score (RSS) at the end of the Randomized Evaluation Period (Day 169)	Baseline, Day 169
Change from Baseline in 6-Minute Walk Test (6MWT) at the end of the Randomized Evaluation Period (Day 169)	Baseline, Day 169
Change from Baseline in Percent Predicted 6MWT at the end of the Randomized Evaluation Period (Day 169)	Baseline, Day 169
Change from Baseline in Bruininks Oseretsky Test of Motor Proficiency, Second Edition (BOT2) Score at the end of the Randomized Evaluation Period (Day 169)	Baseline, Day 169
Change from Baseline in Peabody Developmental Motor Scales, Third Edition (PDMS-3) Score at the end of the Randomized Evaluation Period (Day 169)	Baseline, Day 169

Trial Locations

Locations (1)

Research Site; 🇻🇳 Hanoi, Vietnam