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Evaluating ALXN1850 for treating children with Hypophosphatasia

A Phase 3, Randomized, Double-blinded, Placebo-controlled, Multicenter Study to Evaluate Efficacy and Safety of ALXN1850 Versus Placebo Administered Subcutaneously in Pediatric (2 to < 12 Years of Age) Participants With Hypophosphatasia Who Have Not Received Previous Treatment With Asfotase Alfa

Phase 3 Interventional Alexion Pharmaceuticals, Inc. · NCT06079359

This study is testing a new drug called ALXN1850 to see if it helps children with Hypophosphatasia feel better compared to a placebo.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment30 (estimated)
Ages2 Years to 11 Years
SexAll
SponsorAlexion Pharmaceuticals, Inc. Industry-sponsored
Locations70 sites (Baltimore, Maryland and 69 other locations)
Trial IDNCT06079359 on ClinicalTrials.gov

What this trial studies

This phase 3 study aims to assess the efficacy of ALXN1850 compared to a placebo in pediatric patients diagnosed with Hypophosphatasia (HPP) who have not received prior treatment with asfotase alfa. Participants will undergo radiographic evaluations to measure the outcomes of the treatment. The study will include children who meet specific diagnostic criteria related to HPP, ensuring a focused approach to understanding the drug's impact on this condition.

Who should consider this trial

Good fit: Ideal candidates are treatment-naïve pediatric patients diagnosed with Hypophosphatasia who meet specific clinical and genetic criteria.

Not a fit: Patients with prior treatment for Hypophosphatasia or those without a confirmed diagnosis of the condition may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly improve bone health and quality of life for children suffering from Hypophosphatasia.

How similar studies have performed: While this approach is focused on a specific treatment for HPP, similar studies have shown promise in treating rare genetic conditions, indicating potential for success.

Eligibility criteria

Show full inclusion / exclusion criteria 
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

Where this trial is running

Baltimore, Maryland and 69 other locations

+20 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions HypophosphatasiaHPPALXN1850
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.