Autosomal Dominant Hypocalcemia (ADH)Phase 3CALIBRATENCT05680818
Efficacy and Safety of Encaleret Compared to Standard of Care in Participants With ADH1
A Phase 3 study testing Encaleret in people with Autosomal Dominant Hypocalcemia (ADH), run by Calcilytix Therapeutics, Inc., a BridgeBio company at 25 sites in 10 countries.
Trial summary
The primary purpose of the study is to understand the effectiveness, safety, and tolerability of encaleret when compared to standard of care (SoC) treatment in participants with Autosomal Dominant Hypocalcemia Type 1 (ADH1). Read more about this study
- Who is it for?
- Ages 16 years and older
- Conditions the study is for
- Autosomal Dominant Hypocalcemia (ADH)
- What is being tested?
- Encaleret
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 67 participants
- Where
- 25 sitesin 10 countries
- Study dates
- 6 Jan 2023to Aug 2029
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 16 years and older
- All sexes
- No healthy volunteers
- Child, Adult, Older adult
Who may be able to join
- Participants must have a documented pathogenic or likely pathogenic activating variant, or variant of uncertain significance, of the calcium sensing receptor (CASR) gene associated with biochemical findings of hypoparathyroidism.
- Participants must have a documented history of symptoms or signs of ADH1.
- Participants 16 to <18 years old must have closed growth plates on hand radiograph.
- Participants treated with thiazide diuretics must discontinue thiazides for at least 14 days prior to SoC Optimization Visit 1 through Week 24 (Period 3). When the thiazide is being used as an antihypertensive, alternative therapy will be prescribed by the Investigator as needed.
- Participants treated with phosphate binders (other than calcium salts) must discontinue the phosphate binders at least one day prior to the SoC Optimization Visit 1.
- Participants treated with magnesium or potassium supplements must be willing to discontinue such treatment prior to the first dose of encaleret.
- Participants treated with potassium-sparing diuretics must be willing to discontinue such treatment prior to the first dose of encaleret.
- Participants must meet SoC Optimization criteria as defined in the protocol.
Who cannot join
- History of hypocalcemic seizure within the past 3 months preceding Screening.
- History of thyroid or parathyroid surgery.
- History of renal transplantation.
- Pregnant or nursing (lactating) women, where pregnancy is confirmed by a positive beta-human chorionic gonadotropin (β-hCG) laboratory test.
- History of treatment with parathyroid hormone (PTH) 1-84 or 1-34 within the 2 months preceding Screening and requiring SoC doses exceeding >1.2× their pre-PTH treatment total daily doses or bone turnover markers, Collagen cross-linked C-telopeptide (CTx )and Procollagen type 1 N-propeptide (P1NP), > upper limit of normal for sex, age (men only) and menopausal status (women only).
- Blood 25-OH Vitamin D level <25 nanograms (ng)/milliliter (mL).
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- Estimated glomerular filtration rate (eGFR) <30 mL/minute/1.73 m^2 using chronic kidney disease-EPI creatinine equation refit without the race variable (chronic kidney disease-EPI creatinine equation refit without the race variable [CKD-EPIcr_R]) (for participants <18 years old the Bedside Schwartz equation should be used).
- Participants with positive Hepatitis B surface antigen (HBsAg), Hepatitis A immunoglobulin M (IgM), or human immunodeficiency virus (HIV) viral serology test at the Screening Visit. Participants who are in complete remission from Hepatitis C virus (HCV) as evidenced by sensitive assay ≥12 weeks after completion of HCV therapy may participate in the study.
- Note: Other protocol defined Inclusion/Exclusion criteria may apply.
Trial locations and contacts
25 sites in 10 countries.
25 sites in 10 countries
United States11 sites
Children's Hospital Colorado
Aurora, Colorado, 80045
NIH
Bethesda, Maryland, 20892
Massachusetts General Hospital
Boston, Massachusetts, 02114
Ohio State University Medical Center
Columbus, Ohio, 43203
Physicians East
Greenville, North Carolina, 27834
Houston Methodist Hospital
Houston, Texas, 77030
Indiana University Health University Hospital
Indianapolis, Indiana, 46202
Columbia University Irving Medical Center
New York, New York, 10032
UCSF Benioff Children's Hospital, Oakland
Oakland, California, 94609
The Children's Hospital of Philadelphia
Philadelphia, Pennsylvania, 19104
Mayo Clinic - Rochester
Rochester, Minnesota, 55905
Italy3 sites
IRCCS Ospedale San Raffaele
Milan, 20132
University Hospital of Pisa
Pisa, 56124
Fondazione Policlinico Universitario Campus Bio-Medico
Roma, 00128
Australia2 sites
Royal Brisbane and Women's Hospital
Herston, Queensland, 4029
Royal North Shore Hospital
Saint Leonards, New South Wales, 2065
France2 sites
CHU Bicetre
Le Kremlin-Bicêtre, Le Kremlin-Bicêtre, 94270
Hôpital Edouard Herriot - HCL
Lyon, 69003
United Kingdom2 sites
Freeman Hospital
Newcastle upon Tyne, NE7 7DN
Norfolk and Norwich University Hospital
Norwich, NR4 7UY
About this study
Official title: CALIBRATE: A Phase 3, Randomized, Open-Label Study Evaluating the Efficacy and Safety of Encaleret Compared to Standard of Care in Participants With Autosomal Dominant Hypocalcemia Type 1 (ADH1)
The primary purpose of the study is to understand the effectiveness, safety, and tolerability of encaleret when compared to standard of care (SoC) treatment in participants with Autosomal Dominant Hypocalcemia Type 1 (ADH1).
- Conditions
- Autosomal Dominant Hypocalcemia (ADH)
- Being tested
- Encaleret, Standard of Care
- Keywords
- Autosomal Dominant Hypocalcemia Type 1 (ADH1), Hypocalcemia, Musculoskeletal Diseases, Muscular Diseases, Musculoskeletal Abnormalities, Calcium Metabolism Disorders, Metabolic Diseases, Hypoparathyroidism, Hypocalcemic Seizures, Hypercalciuria, Nephrocalcinosis, Nephrolithiasis, Calcium Sensing Receptor, Encaleret, Hypopara
- Medical subject headings
- Hypercalciuric Hypocalcemia, Familial, Hypocalcemia, Musculoskeletal Diseases, Muscular Diseases, Musculoskeletal Abnormalities, Calcium Metabolism Disorders, Metabolic Diseases, Hypoparathyroidism
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
EncaleretDrug
Also called CLTX-305, Encaleret Sulfate
Administered as film-coated tablet for oral use
Standard of CareDietary supplement
Calcium supplements and/or active Vitamin D (calcitriol, alfacalcidol, falecalcitriol, etc.)
| Study group | Role | What they receive |
|---|---|---|
| Encaleret | Experimental | Participants will receive encaleret at a dose as needed based on calcium levels. Receives: Drug: Encaleret |
| Standard of Care (SoC) | Other | Participants will continue receiving calcium supplements and/or active Vitamin D (calcitriol, alfacalcidol, falecalcitriol, etc.) Receives: Dietary Supplement: Standard of Care |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Responders who Achieve Both Albumin-Corrected Blood Calcium (cCa) and 24-hour Urinary Calcium (UCa) Within the Target Range
- cCa within 8.3-10.7 mg/dL (2.08-2.68 millimoles per liter [mmol/L])
- 24-hr UCa within the reference range (< 300 mg/day for men [7.5 mmol/day], < 250 mg/day for women [6.25 mmol/day])
Measured: Up to Week 24
Secondary outcomes (13)
Number of Participants With Intact Parathyroid Hormone (iPTH) Within or Greater than the Reference Range
Measured: Up to Week 24
Number of Participants who Achieve Blood Magnesium Within the Reference Range
Measured: Up to Week 24
Number of Participants who Achieve Blood Phosphate Within the Reference Range
Measured: Up to Week 24
Change From Baseline in Blood 1,25-(OH)2 Vitamin D
Measured: Baseline to Week 24
Change From Baseline in cCa
Measured: Baseline to Week 24
Change From Baseline in 24-hour UCa
Measured: Baseline to Week 24
Change From Baseline in iPTH
Measured: Baseline to Week 24
Change From Baseline in Blood Phosphate and Blood Magnesium
Measured: Baseline to Week 24
Change From Baseline in Urine Magnesium, Phosphate, Sodium, and Citrate Handling
Measured: Baseline to Week 24
Change From Baseline in QT Interval Corrected for Changes in the Heart Rate With Fridericia Formula (QTcF) as Assessed by Electrocardiogram (ECG)
Measured: Baseline to Week 24
Change from Baseline in 36-Item Short Form Health Survey (SF-36) Physical Component Score and Mental Component Score and Each of the Sub-Domains
Measured: Baseline to Week 24
Number of Participants in the Encaleret Arm Receiving Calcium and/or Vitamin D Supplements
Measured: Up to Week 24
Steady State Encaleret Trough Concentration (Ctrough)
Measured: Up to Week 24
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Jan 2023
- Study start6 Jan 2023
- Primary completion22 Aug 2025
- Study completionAug 2029 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Autosomal Dominant Hypocalcemia (ADH)Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Enrolment
- 67 participants (actual)
Sponsor and investigators
- Lead sponsor
- Calcilytix Therapeutics, Inc., a BridgeBio company
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Calcilytix Medical Director, Study director, Calcilytix Therapeutics, Inc., a BridgeBio company
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05680818
- Sponsor's protocol ID
- CLTX-305-302
- Acronym
- CALIBRATE
- Status last verified
- Jul 2026
- First submitted
- 12 Dec 2022
- Last updated
- 29 Jul 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 29 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- CALIBRATE: A Phase 3, Randomized, Open-Label Study Evaluating the Efficacy and Safety of Encaleret Compared to Standard of Care in Participants With Autosomal Dominant Hypocalcemia Type 1 (ADH1)
- ClinicalTrials.gov ID
- NCT05680818
- Acronym / sponsor ID
- CALIBRATE / CLTX-305-302
- Conditions
- Autosomal Dominant Hypocalcemia (ADH)
- Keywords
- Autosomal Dominant Hypocalcemia Type 1 (ADH1), Hypocalcemia, Musculoskeletal Diseases, Muscular Diseases, Musculoskeletal Abnormalities, Calcium Metabolism Disorders, Metabolic Diseases, Hypoparathyroidism
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Active, not recruiting
- Enrolment
- 67 participants (actual)
- Lead sponsor
- Calcilytix Therapeutics, Inc., a BridgeBio companyIndustry (pharma, biotech, devices)
- Study start
- 6 Jan 2023 (actual)
- Primary completion
- 22 Aug 2025 (actual)
- Study completion
- Aug 2029 (estimated)
- First posted
- 11 Jan 2023 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The primary purpose of the study is to understand the effectiveness, safety, and tolerability of encaleret when compared to standard of care (SoC) treatment in participants with Autosomal Dominant Hypocalcemia Type 1 (ADH1).
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
| Arm | Type | Receives |
|---|---|---|
| Encaleret | Experimental | Drug: EncaleretParticipants will receive encaleret at a dose as needed based on calcium levels. |
| Standard of Care (SoC) | Other | Dietary Supplement: Standard of CareParticipants will continue receiving calcium supplements and/or active Vitamin D (calcitriol, alfacalcidol, falecalcitriol, etc.) |
Who may qualify
- Ages
- 16 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Child, Adult, Older adult
Key inclusion criteria (8 listed)
- Participants must have a documented pathogenic or likely pathogenic activating variant, or variant of uncertain significance, of the calcium sensing receptor (CASR) gene associated with biochemical findings of hypoparathyroidism.
- Participants must have a documented history of symptoms or signs of ADH1.
- Participants 16 to <18 years old must have closed growth plates on hand radiograph.
- Participants treated with thiazide diuretics must discontinue thiazides for at least 14 days prior to SoC Optimization Visit 1 through Week 24 (Period 3). When the thiazide is being used as an antihypertensive, alternative therapy will be prescribed by the Investigator as needed.
- Participants treated with phosphate binders (other than calcium salts) must discontinue the phosphate binders at least one day prior to the SoC Optimization Visit 1.
Key exclusion criteria (9 listed)
- History of hypocalcemic seizure within the past 3 months preceding Screening.
- History of thyroid or parathyroid surgery.
- History of renal transplantation.
- Pregnant or nursing (lactating) women, where pregnancy is confirmed by a positive beta-human chorionic gonadotropin (β-hCG) laboratory test.
- History of treatment with parathyroid hormone (PTH) 1-84 or 1-34 within the 2 months preceding Screening and requiring SoC doses exceeding >1.2× their pre-PTH treatment total daily doses or bone turnover markers, Collagen cross-linked C-telopeptide (CTx )and Procollagen type 1 N-propeptide (P1NP), > upper limit of normal for sex, age (men only) and menopausal status (women only).
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| EncaleretAlso: CLTX-305, Encaleret SulfateAdministered as film-coated tablet for oral use | Drug | Encaleret |
| Standard of CareCalcium supplements and/or active Vitamin D (calcitriol, alfacalcidol, falecalcitriol, etc.) | Dietary supplement | Standard of Care (SoC) |
Primary outcome
Number of Responders who Achieve Both Albumin-Corrected Blood Calcium (cCa) and 24-hour Urinary Calcium (UCa) Within the Target Range
Time frame: Up to Week 24
* cCa within 8.3-10.7 mg/dL (2.08-2.68 millimoles per liter [mmol/L]) * 24-hr UCa within the reference range (< 300 mg/day for men [7.5 mmol/day], < 250 mg/day for women [6.25 mmol/day])
13 secondary outcomes
Number of Participants With Intact Parathyroid Hormone (iPTH) Within or Greater than the Reference Range
Time frame: Up to Week 24
Number of Participants who Achieve Blood Magnesium Within the Reference Range
Time frame: Up to Week 24
Number of Participants who Achieve Blood Phosphate Within the Reference Range
Time frame: Up to Week 24
Change From Baseline in Blood 1,25-(OH)2 Vitamin D
Time frame: Baseline to Week 24
Change From Baseline in cCa
Time frame: Baseline to Week 24
Change From Baseline in 24-hour UCa
Time frame: Baseline to Week 24
Change From Baseline in iPTH
Time frame: Baseline to Week 24
Change From Baseline in Blood Phosphate and Blood Magnesium
Time frame: Baseline to Week 24
Change From Baseline in Urine Magnesium, Phosphate, Sodium, and Citrate Handling
Time frame: Baseline to Week 24
Change From Baseline in QT Interval Corrected for Changes in the Heart Rate With Fridericia Formula (QTcF) as Assessed by Electrocardiogram (ECG)
Time frame: Baseline to Week 24
Change from Baseline in 36-Item Short Form Health Survey (SF-36) Physical Component Score and Mental Component Score and Each of the Sub-Domains
Time frame: Baseline to Week 24
Number of Participants in the Encaleret Arm Receiving Calcium and/or Vitamin D Supplements
Time frame: Up to Week 24
Steady State Encaleret Trough Concentration (Ctrough)
Time frame: Up to Week 24
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Jul 2026.
- Individual participant dataSharing planned: No
Related trials for Autosomal Dominant Hypocalcemia (ADH)
RecruitingObservational study
National Registry of Rare Kidney Diseases
Adenine Phosphoribosyltransferase Deficiency, AH Amyloidosis
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
Calcilytix Medical Director study director
Calcilytix Therapeutics, Inc., a BridgeBio company
25 sites in 10 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing Encaleret in people with Autosomal Dominant Hypocalcemia (ADH), run by Calcilytix Therapeutics, Inc., a BridgeBio company at 25 sites in 10 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 9 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: under way, not looking for participants, as of the sponsor's last update on 29 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 25 sites in United States, Italy, Australia, France, United Kingdom and 5 more countries. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of Responders who Achieve Both Albumin-Corrected Blood Calcium (cCa) and 24-hour Urinary Calcium (UCa) Within the Target Range (time frame: Up to Week 24). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Jul 2026.