Phase 3 Study of ALXN1850 in Pediatric Participants With HPP Previously Treated With Asfotase Alfa (CHESTNUT)

Alexion Pharmaceuticals

Status and phase: Active, not recruiting; Phase 3

Conditions: Hypophosphatasia

Treatments: Drug: ALXN1850; Drug: asfotase alfa

Study type: Interventional

Funder types: Industry

Identifiers

NCT06079372

ALXN1850-HPP-303 (Other Identifier)

D8590C00004

Details and patient eligibility

About

The primary purpose of this study is to assess the safety and tolerability of ALXN1850 versus asfotase alfa in pediatric participants with HPP previously treated with asfotase alfa.

Enrollment: 42 patients

Sex: All

Ages: 2 to 11 years old

Volunteers: No Healthy Volunteers

Inclusion criteria

• Diagnosis of HPP documented in the medical records
• Presence of open growth plates by X-ray during Screening Period
• Tanner stage 2 or less during the Screening Period
• Must have been treated with 6 mg/kg/ week of asfotase alfa via SC injection administered as either 2mg/kg 3 times per week or 1 mg/kg 6 times per week for ≥ 6 months before Day 1. Note: participants currently treated with 9 mg/kg (eg, 3 mg/kg 3 times per week) will not be allowed in the study.

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 asfotase alfa or ALXN1850
• Body weight < 10 kg during the Screening Period

Trial design

Primary purpose: Treatment

Allocation: Randomized

Interventional model: Parallel Assignment

Masking: None (Open label)

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42 participants in 2 patient groups

ALXN1850

Experimental group

Description:

Starting at Day 1 of the Randomized Evaluation Period participants will receive ALXN1850 for a total of 24 weeks. Participants will receive bodyweight dependent doses of either 20mg, 35mg or 50mg of ALXN1850 once q2w via SC injection. During Part A of the OLE Period, participants will have frequent visits over the first 24 weeks; Part B of the OLE Period participants will have visits every 9 months for up to approximately 108 weeks.

Treatment:

Drug: asfotase alfa

Drug: ALXN1850

asfotase alfa

Experimental group

Description:

Starting at Day 1 of the Randomized Evaluation Period, participants will receive asfotase alfa for a total of 24 weeks. Participants will receive 6 mg/kg/week of asfotase alfa via SC injection as either 2 mg/kg 3 times per week or 1 mg/kg 6 times per week. Part A of the OLE Period participants will have frequent visits over the first 24 weeks; Part B will have visits every 9 months for up to approximately 108 weeks.

Treatment:

Drug: asfotase alfa