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Study on ALXN1850 and Asfotase Alfa for Children Aged 2-12 with Hypophosphatasia Previously Treated with Asfotase Alfa

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a rare condition called Hypophosphatasia (HPP), which affects the development of bones and teeth. The study involves children aged 2 to under 12 years who have previously been treated for HPP. The trial will compare two treatments: a new medication known as ALXN1850 and an existing treatment called Asfotase Alfa, which is marketed under the name Strensiq. Both medications are given as a solution for injection under the skin, a method known as subcutaneous injection.

The purpose of the study is to evaluate the safety and how well children tolerate ALXN1850 compared to Asfotase Alfa. Participants will be randomly assigned to receive either ALXN1850 or Asfotase Alfa. The study will monitor the children over a period to observe any side effects and how the treatments affect their condition. The trial will also look at various health measures to understand the impact of the treatments on the children's overall health and quality of life.

Throughout the study, researchers will collect information on the children's health and any changes in their condition. This will include regular check-ups and assessments to ensure the safety and effectiveness of the treatments. The study aims to provide valuable insights into the management of Hypophosphatasia in children and potentially improve treatment options for this condition in the future.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, the participant must be between 2 and 12 years old and have a documented diagnosis of hypophosphatasia (HPP).

    The participant must have been previously treated with asfotase alfa for at least 6 months before the study begins.

  2. Step 2

    Initial assessment

    An initial assessment will be conducted to confirm the presence of open growth plates through an X-ray.

    The participant's development stage will be evaluated to ensure it is at Tanner stage 2 or less.

  3. Step 3

    Treatment administration

    Participants will receive either ALXN1850 or asfotase alfa through subcutaneous injections.

    The dosage for asfotase alfa is 6 mg/kg per week, administered as either 2 mg/kg three times per week or 1 mg/kg six times per week.

  4. Step 4

    Monitoring and evaluation

    Throughout the study, the safety and tolerability of the treatments will be assessed.

    Participants will be monitored for any adverse effects or reactions to the medication.

  5. Step 5

    End of evaluation period

    The primary evaluation period concludes on Day 169.

    Various health and function scores will be measured to assess the impact of the treatment.

  6. Step 6

    Completion of study

    The study is estimated to end by December 31, 2027.

    Final assessments will be conducted to evaluate the overall outcomes of the treatment.

Who can join the trial?

7 criteria

  • The participant must be at least 2 years old but younger than 12 years old on the first day of the study.
  • The participant must have a diagnosis of **Hypophosphatasia (HPP)**, which should be documented in their medical records.
  • The participant must have open growth plates, which are areas of growing tissue near the ends of the long bones, as shown by an X-ray during the screening period.
  • The participant must be at **Tanner stage 2** or less during the screening period. Tanner stages are a way to describe physical development during puberty.
  • The participant must have been treated with **asfotase alfa**, a medication, at a dose of 6 mg per kg per week. This should have been given either as 2 mg per kg three times a week or 1 mg per kg six times a week for at least 6 months before the first day of the study.
  • Female participants who can have children and male participants must follow specific birth control requirements as outlined in the study protocol.
  • The participant's legal guardian must be willing and able to provide written informed consent, which is a formal agreement to participate in the study. The participant must also be willing to give written informed assent, which is a similar agreement for children, if applicable. This includes agreeing to follow the study's requirements and restrictions.

Who cannot join the trial?

7 criteria

  • Participants who have not been previously treated with a medication called asfotase alfa.
  • Participants who have any other medical condition that might interfere with the study.
  • Participants who are unable to follow the study procedures or instructions.
  • Participants who are currently participating in another clinical trial.
  • Participants who have had a serious allergic reaction to any medication in the past.
  • Participants who are pregnant or breastfeeding.
  • Participants who have any condition that the study doctors believe would make it unsafe for them to participate.
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Investigated drugs

  • ALXN1850

    is a new medication being studied for its safety and effectiveness in treating children with hypophosphatasia (HPP). This medication is administered through an injection under the skin. The trial aims to see how well children tolerate this new treatment compared to the existing therapy.

  • Asfotase Alfa

    is an existing treatment for hypophosphatasia (HPP) that is also given as an injection under the skin. It is used to help manage the symptoms of HPP in children. In this study, it serves as the comparison treatment to evaluate the new medication, ALXN1850.

What is already known about the treatment

  • ALXN1850

    This medication is administered subcutaneously and is currently being studied in clinical trials for its safety and effectiveness in treating hypophosphatasia, a rare bone disorder. It is in the experimental phase and is being compared to an existing treatment, asfotase alfa, in pediatric patients. The main therapeutic indication is to improve bone health in children with this condition. ALXN1850 works by targeting specific enzymes involved in bone mineralization, helping to correct the underlying enzyme deficiency. It is classified as an enzyme replacement therapy.

  • Asfotase Alfa

    This medication is also administered subcutaneously and is an established treatment for hypophosphatasia, particularly in pediatric patients. It is currently being used as a control in clinical trials to compare its safety and efficacy against ALXN1850. The primary therapeutic use is to enhance bone mineralization and improve symptoms in patients with this condition. Asfotase alfa functions by replacing deficient enzymes that are crucial for bone development. It is classified under enzyme replacement therapies.

Investigated diseases

Hypophosphatasia – Hypophosphatasia is a rare genetic disorder that affects the development of bones and teeth. It is caused by mutations in the gene responsible for producing an enzyme called alkaline phosphatase, which is crucial for bone mineralization. As a result, individuals with this condition may experience soft and weak bones, leading to skeletal abnormalities and frequent fractures. The severity of symptoms can vary widely, ranging from mild dental issues to severe bone deformities and growth problems. In some cases, hypophosphatasia can also affect the respiratory system and lead to muscle weakness. The progression of the disease depends on the specific genetic mutation and the age at which symptoms first appear.
Trial detailsLast updated 7 Oct 2026
Age0-17PhasePhase IIITrial ID2023-505674-15-00Protocol codeALXN1850-HPP-303Estimated enrolment40 patientsSponsorAlexion Pharmaceuticals Inc.

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