Phase 3 Study of ALXN1850 Versus Placebo in Adolescent and Adult Participants With HPP Who Have Not Previously Been Treated With Asfotase Alfa (HICKORY)

March 11, 2026 updated by: Alexion Pharmaceuticals, Inc.

A Phase 3, Randomized, Double-blinded, Placebo-controlled, Multicenter Study to Evaluate Efficacy and Safety of ALXN1850 (Recombinant Alkaline Phosphatase) Administered Subcutaneously in Adolescent (12 to < 18 Years of Age) and Adult Participants With Hypophosphatasia Who Have Not Previously Been Treated With Asfotase Alfa

The primary objective of this study is to assess the efficacy of ALXN1850 versus placebo on functional outcomes in adolescent and adult participants with HPP who have not previously been treated with asfotase alfa.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Study Type

Interventional

Enrollment (Actual)

124

Phase

  • 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 Locations

  • Argentina
      • Ciudad de Buenos Aires, Argentina, C1199
        • Research Site
  • Australia
      • Clayton, Australia, 3168
        • Research Site
      • Herston, Australia, 4029
        • Research Site
      • Parkville, Australia, 3052
        • Research Site
      • St Leonards, Australia, 2065
        • Research Site
  • Brazil
      • Belo Horizonte, Brazil, 30130-100
        • Research Site
      • Brasília, Brazil, 71625-009
        • 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 7Z4
        • Research Site
      • Edmonton, Alberta, Canada, T6G 2H7
        • Research Site
    • Manitoba
      • Winnepeg, Manitoba, Canada, R3E 3P4
        • Research Site
    • Ontario
      • Oakville, Ontario, Canada, L6M 1M1
        • Research Site
    • Quebec
      • Trois-Rivières, Quebec, Canada, G9A 4P3
        • Research Site
  • China
      • Beijing, China, 100730
        • Research Site
      • Beijing, China, 100039
        • Research Site
      • Changsha, China, 430033
        • Research Site
      • Chengdu, China, 610041
        • Research Site
      • Nanchang, China, 330006
        • Research Site
      • Qingdao, China, 266035
        • Research Site
      • Shanghai, China, 201306
        • Research Site
      • Shenzhen, China, 518053
        • Research Site
  • France
      • Paris, France, 75014
        • Research Site
      • Poitiers, France, 86000
        • Research Site
  • Germany
      • Bad Reichenhall, Germany, 83435
        • Research Site
      • Berlin, Germany, 10117
        • Research Site
      • Bonn, Germany, 53127
        • Research Site
      • Hamburg, Germany, 20251
        • Research Site
      • Würzburg, Germany, 97074
        • Research Site
  • Israel
      • Ashkelon, Israel, 7830604
        • Research Site
      • Ramat Gan, Israel, 52621
        • Research Site
  • Italy
      • Florence, Italy, 50139
        • Research Site
      • Milan, Italy, 20122
        • Research Site
      • Milan, Italy, 20132
        • Research Site
      • Padua, Italy, 35128
        • Research Site
      • Pisa, Italy, 56126
        • Research Site
      • San Giovanni Rotondo, Italy, 71013
        • Research Site
      • Verona, Italy, 37134
        • Research Site
  • Japan
      • Hiroshima, Japan, 734-8551
        • Research Site
      • Iizuka-shi, Japan, 820-8505
        • Research Site
      • Osaka, Japan, 545-8586
        • Research Site
      • Sapporo, Japan, 060-8648
        • Research Site
      • Yaizu-shi, Japan, 425-8505
        • Research Site
  • Poland
      • Lodz, Poland, 93-338
        • Research Site
  • South Korea
      • Seoul, South Korea, 03722
        • Research Site
      • Seoul, South Korea, 07061
        • Research Site
      • Suwon, South Korea, 16499
        • Research Site
  • Spain
      • Barcelona, Spain, 08003
        • Research Site
      • Granada, Spain, 18016
        • Research Site
      • Madrid, Spain, 28046
        • Research Site
      • San Cristóbal de La Laguna, Spain, 38320
        • Research Site
      • Santander, Spain, 39008
        • Research Site
      • Vitoria-Gasteiz, Spain, 01009
        • Research Site
  • Taiwan
      • Taipei, Taiwan, 100
        • Research Site
      • Taoyuan District, Taiwan, 333
        • Research Site
  • Turkey (Türkiye)
      • Ankara, Turkey (Türkiye), 06560
        • Research Site
      • Erzurum, Turkey (Türkiye), 25240
        • Research Site
  • United Kingdom
      • London, United Kingdom, SW170QT
        • Research Site
  • United States
    • Indiana
      • Indianapolis, Indiana, United States, 46202
        • Research Site
    • New York
      • Garden City, New York, United States, 11530
        • Research Site
    • North Carolina
      • Durham, North Carolina, United States, 27705
        • Research Site
    • Ohio
      • Columbus, Ohio, United States, 43203
        • Research Site
    • Tennessee
      • Nashville, Tennessee, United States, 37212
        • 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

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Description

Inclusion Criteria:

  • Diagnosis of HPP documented in the medical records

  • Must meet 1 of the following criteria:

    1. Documented ALPL gene variant (pathogenic, likely pathogenic, or variant of unknown significance) from a Clinical Laboratory Improvement Amendments (CLIA) or ISO 15189 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)

  • Must meet 1 of the following criteria without a probably cause other than HPP:

    1. Serum ALP activity below the age- and sex-adjusted normal range during the screening period as measured by the Central Laboratory
    2. Two 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 CLIA or ISO 15189 certified, or have other local equivalent laboratory certification with Alexion's approval.
  • Two separate 6MWTs at below 85% of the predicted distance (for age, sex, weight, and height) during the Screening Period without a probable cause other than HPP

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 (Table 9)

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
Intervention / Treatment
Placebo Comparator: Placebo Group
During the Randomized Evaluation Period, the placebo group will receive placebo on Day 1, followed by once every 2 weeks (q2w) via SC injection for 24 weeks. Participants will enter the OLE Period and receive bodyweight dependent doses of either 20mg, 35mg, or 50mg of ALXN1850 and continue q2w dosing with ALXN1850 for up to 132 weeks.
Drug: Placebo
Placebo will be administered via SC injection.
Experimental: ALXN1850 Group
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 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
ALXN1850 will be administered via subcutaneous (SC) injection.
Drug: Placebo
Placebo will be administered via SC injection.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Time Frame
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

Secondary Outcome Measures

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
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 Percent Predicted 6MWT 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
Change from Baseline in 30-second Sit to Stand (STS) Test Score at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Baseline, Day 169
Baseline, Day 169
Change from Baseline in Lower Extremity Functional Scale (LEFS) Score at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Baseline, Day 169
Baseline, Day 169
Change from Baseline in Timed Up-and-Go (TUG) at the end of the Randomized Evaluation Period (Day 169)
Time Frame: Baseline, Day 169
Baseline, Day 169
Change from Baseline in BPI-SF pain severity score at the end of the Randomized Evaluation Period (Day 169) (adult cohort only)
Time Frame: Baseline, Day 169
Baseline, Day 169
Change from Baseline in FACIT-Fatigue score at the end of the Randomized Evaluation Period (Day 169) (adult cohort only)
Time Frame: Baseline, Day 169
Baseline, Day 169

Collaborators and Investigators

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

Sponsor

Alexion Pharmaceuticals, Inc.

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

Helpful Links

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)

January 3, 2024

Primary Completion (Actual)

July 9, 2025

Study Completion (Estimated)

March 29, 2028

Study Registration Dates

First Submitted

October 6, 2023

First Submitted That Met QC Criteria

October 6, 2023

First Posted (Actual)

October 12, 2023

Study Record Updates

Last Update Posted (Actual)

March 12, 2026

Last Update Submitted That Met QC Criteria

March 11, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • D8590C00002
  • ALXN1850-HPP-301 (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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