Overview

The overall objective of this study is to evaluate the pharmacokinetics (PK), efficacy, and safety of encaleret in pediatric participants from birth to 17 years of age with ADH1.

Eligibility

Key Inclusion Criteria:

• Provide written informed consent (if legally permitted), or have written informed consent from a parent/legal guardian and provide assent (where required and as appropriate per local requirements)
• Have a documented pathogenic or likely pathogenic activating variant, or variant of uncertain significance of the calcium-sensing receptor (CASR), associated with biochemical findings of hypoparathyroidism at screening or a documented history of hypoparathyroidism as manifested by hypocalcemia and intact parathyroid hormone (PTH) \<40 picogram per milliliter (pg/mL) (4.2 picomoles per liter \[pmol/L\])
• Have at least 1 symptom or sign of hypoparathyroidism at screening or a documented history of symptoms or signs of hypoparathyroidism
• Be on ADH1 treatment for at least 6 months before screening for cohorts 1 to 3, or for at least 3 months before screening for cohort 4

Key Exclusion Criteria:

• History of thyroid or parathyroid surgery
• History of renal transplantation
• History of cancer (except thyroid cancer, basal cell skin cancer, or squamous cell skin cancer), skeletal malignancies, bone metastases, irradiation (radiotherapy) to the skeleton, chemotherapy with alkylating agents, Paget disease, fibrous dysplasia, chronic osteomyelitis, bone infarcts, benign bone tumors with curettage and bone grafts, retinoblastoma, or Li-Fraumeni syndrome within 5 years before screening
• Received any investigational medicinal product within 30 days or 5 half-lives before Day 1, whichever is longer, or is in follow-up for another interventional clinical study during screening
• Treatment with a strong P-glycoprotein (P-gp) inhibitor within 300 days before screening for amiodarone or within 30 days before screening for any other strong P-gp inhibitor
• Treatment with cardiac glycosides, or is being breastfed while the participant's nursing mother is treated with cardiac glycosides, within 30 days before screening
• Presence or history of any disease or condition (eg, drug or alcohol dependence) that would affect the participant's safety, treatment compliance, or ability to complete the study, in the opinion of the investigator

Other protocol defined inclusion/exclusion criteria apply.