Efficacy, Safety, and Tolerability of Encaleret in Participants With Chronic Hypoparathyroidism

NCT07805356 | Recruiting Phase 3 FDA Drug

• 3 other identifiers: CLTX-305-3042026-526140-13U1111-1341-6994
• Study Type: interventional
• Target: 160
• Locations: 2 countries
• Sites: 5

Brief Summary

The aim of the study is to evaluate the efficacy, safety, and tolerability of orally administered encaleret tablets in participants with chronic hypoparathyroidism (HP).

Conditions

Hypoparathyroidism; Chronic Hypoparathyroidism

Keywords

Chronic Hypoparathyroidism; Hypoparathyroidism; Encaleret

Outcome Measures

Primary Outcomes (1)

• Number of Responders who Achieve Both Albumin-Corrected Blood Calcium (cCa) and 24-hour Urine Calcium (UCa) Within the Protocol-defined Target Range

  Week 24

Secondary Outcomes (14)

• Number of Participants With cCa Within Protocol-defined Range

  Week 24

• Change From Baseline to Week 24 in cCa

  Baseline, Week 24

• Absolute Value of cCa at Week 24

  Week 24

• Number of Participants With 24-hour UCa Below the Sex-specific Upper Reference Limits (Protocol-defined Range)

  Week 24

• Change from Baseline to Week 24 in 24-hour UCa

  Baseline, Week 24

Study Arms (2)

Encaleret

EXPERIMENTAL

Participants will receive encaleret during the 24-week double-blind treatment period. Participants will then have the option to enter an open-label long-term extension (LTE) period to continue receiving encaleret for up to 192 weeks.

Drug: Encaleret

Placebo

PLACEBO COMPARATOR

Participants will receive placebo during the 24-week double-blind treatment period. Participants will then have the option to enter an open-label LTE period to receive encaleret for up to 192 weeks.

Drug: Encaleret; Drug: Placebo

Interventions

Encaleret DRUG

Oral tablets

Encaleret; Placebo

Placebo DRUG

Oral tablets

Placebo

Eligibility Criteria

• Age: 16 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• Participants must have had a clinically confirmed diagnosis of chronic HP, with disease duration of at least 26 weeks prior to screening. Cause of chronic HP can be postsurgical, autoimmune or idiopathic.
• For participants with nonsurgical chronic HP etiology, sufficient documentation that the participant does not harbor any variants in calcium-sensing receptor (CASR) or GNA11 that are classified as pathogenic, likely pathogenic, or of uncertain significance, with the exception of benign common polymorphisms (CASR A986S and R990G) is needed.
• Participants must be on stable doses of calcium and active vitamin D supplementation at or above the following minimum thresholds for at least 6 weeks prior to screening.
• For participants enrolled in study sites outside Japan:
• Calcitriol ≥0.5 micrograms (μg)/day or alfacalcidol ≥1.0 μg/day
• Elemental calcium ≥800 milligrams (mg)/day (for example, calcium citrate, calcium carbonate)
• Participants must meet the following criteria during screening: cCa within 7.8 to 9.5 mg/deciliter (dL) and 24-hour UCa ≥300 mg/day (males) or ≥250 mg/day (females).
• Participants have serum 25-hydroxy (OH) vitamin D concentration of 20 to 80 nanograms (ng)/milliliter (mL) (50-200 nanomoles \[nmol\]/liter \[L\]).
• Participants have serum magnesium concentration within the reference range.
• Participants on thiazide or loop diuretics must be able to discontinue them during the first 24 weeks of study (treatment).
• Participants must be capable of giving signed informed consent or assent, which includes compliance with the requirements and restrictions listed in the informed consent form and in this protocol.

You may not qualify if:

• Genetically confirmed diagnosis of autosomal dominant hypocalcemia type 1 (ADH1) or autosomal dominant hypocalcemia type 2 (ADH2) due to activating variants in CASR or GNA11, respectively.
• History of hypocalcemic seizure in the 3 months prior to screening.
• History of cancer (except non-melanoma skin cancer) or bone metastases in the 5 years prior to screening.
• Prior skeletal irradiation, chemotherapy with alkylating agents, or diagnosis of Paget's disease, fibrous dysplasia, chronic osteomyelitis, bone infarcts, benign bone tumors with curettage and grafting, retinoblastoma, or Li-Fraumeni syndrome.
• Presence or history of any disease or condition (for example, drug or alcohol dependence) that, in the view of the investigator, would affect the participant's safety or places the participant at high risk of poor treatment compliance or of not completing the study.

Sponsors & Collaborators

• Calcilytix Therapeutics, Inc., a BridgeBio company: lead

Study Sites (5)

Calcilytix Therapeutics, Inc., a BridgeBio Company, Investigational Site

Reno, Nevada, 89511, United States

RECRUITING

Calcilytix Therapeutics, Inc., a BridgeBio Company, Investigational Site

Greenville, North Carolina, 27834, United States

RECRUITING

Calcilytix Therapeutics, Inc., a BridgeBio Company, Investigational Site

Morehead City, North Carolina, 28557, United States

RECRUITING

Calcilytix Therapeutics, Inc., a BridgeBio Company, Investigational Site

El Paso, Texas, 79935, United States

RECRUITING

Calcilytix Therapeutics, Inc., a BridgeBio Company, Investigational Site

Oakville, Ontario, L6M 1M1, Canada

RECRUITING

MeSH Terms

Conditions

Hypoparathyroidism

Condition Hierarchy (Ancestors)

Parathyroid Diseases; Endocrine System Diseases

Study Officials

• Calcilytix Medical Director

  Calcilytix Therapeutics, Inc., a BridgeBio company

  STUDY DIRECTOR

Central Study Contacts

Medical Information

CONTACT

650-600-3610; MedInfo@bridgebio.com

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Masking Details: The treatment period will be double-blind. The long-term extension period will be open-label.
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: September 1, 2026
• First Posted: September 4, 2026
• Study Start: August 31, 2026
• Primary Completion (Estimated): January 1, 2028
• Study Completion (Estimated): January 1, 2033
• Last Updated: September 16, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

CA (1); US (4)