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

May 26, 2026 updated by: Alexion Pharmaceuticals, Inc.

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

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.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
30

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Australia
      • Nedlands, Australia, 6009
        • Research Site
      • Parkville, Australia, 3052
        • Research Site
  • Belgium
      • Brussels, Belgium, 1020
        • Research Site
  • Brazil
      • Brasília, Brazil, 71625-009
        • Research Site
      • Porto Alegre, Brazil, 90610-261
        • Research Site
      • Recife, Brazil, 50740-465
        • Research Site
      • Salvador, Brazil, 40050-410
        • Research Site
      • São Paulo, Brazil, 05403-900
        • Research Site
      • São Paulo, Brazil, 01409-902
        • Research Site
  • Canada
    • Alberta
      • Calgary, Alberta, Canada, T2E 7H7
        • Research Site
    • Manitoba
      • Winnepeg, Manitoba, Canada, R3E 3P4
        • Research Site
  • China
      • Beijing, China, 100045
        • Research Site
      • Guangzhou, China, 510623
        • Research Site
      • Shanghai, China, 2000127
        • Research Site
      • Shenzhen, China, 518053
        • Research Site
  • Finland
      • Helsinki, Finland, 00290
        • Research Site
  • Israel
      • Ashkelon, Israel, 7830604
        • Research Site
  • Mexico
      • Chihuahua City, Mexico, 31238
        • Research Site
  • Poland
      • Lodz, Poland, 93-338
        • Research Site
  • Romania
      • Bucharest, Romania, 011863
        • Research Site
  • Spain
      • Madrid, Spain, 28046
        • Research Site
      • Vitoria-Gasteiz, Spain, 01009
        • Research Site
  • Sweden
      • Stockholm, Sweden, 17176
        • Research Site
  • Taiwan
      • Taipei, Taiwan, 100
        • Research Site
  • Turkey (Türkiye)
      • Ankara, Turkey (Türkiye), 06560
        • Research Site
      • Bursa, Turkey (Türkiye), 16059
        • Research Site
      • Erzurum, Turkey (Türkiye), 25240
        • Research Site
      • Istanbul, Turkey (Türkiye), 34899
        • Research Site
  • United Kingdom
      • Birmingham, United Kingdom, B4 6NH
        • Research Site
  • United States
    • Maryland
      • Baltimore, Maryland, United States, 21287
        • Research Site
    • Missouri
      • Kansas City, Missouri, United States, 64108
        • Research Site
    • North Carolina
      • Durham, North Carolina, United States, 27705
        • Research Site

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Child

Accepts Healthy Volunteers

No

Description

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 Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Treatment
  • Allocation: Randomized
  • Interventional Model: Parallel Assignment
  • Masking: Quadruple

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: 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.
Drug: ALXN1850
Participants will receive a ALXN1850 via subcutaneous (SC) injection.
Drug: Placebo
Participants will receive placebo via SC injection.
Placebo Comparator: 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.
Drug: Placebo
Participants will receive placebo via SC injection.

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Radiographic Global Impression of Change (RGI-C) Score at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Day 169
Day 169

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Change from Baseline in Rickets Severity Score (RSS) at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Baseline, Day 169
Baseline, Day 169
Change from Baseline in 6-Minute Walk Test (6MWT) at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Baseline, Day 169
Baseline, Day 169
Change from Baseline in Percent Predicted 6MWT at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Baseline, 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)
Time Frame: Baseline, 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)
Time Frame: Baseline, Day 169
Baseline, Day 169
RGI-C Responder at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Day 169
Day 169

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Alexion Pharmaceuticals, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
May 14, 2024

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
January 6, 2026

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
August 24, 2028

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 6, 2023

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
October 6, 2023

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
October 12, 2023

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 28, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 26, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • D8590C00003
  • ALXN1850-HPP-305 (Other Identifier: Alexion Pharmaceuticals, Inc.)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

Alexion has a public commitment to allow requests for access to study data and will be supplying a protocol, CSR, and plain language summaries.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • CSR

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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