Phase 2 Study of the PTH-Independent Effects of Encaleret on Mineral Homeostasis in Subjects With Post-Surgical Hypoparathyroidism (PSH)
Phase: PHASE2
Conditions: Post-Surgical Hypoparathyroidism
Sponsor: National Institute of Dental and Craniofacial Research (NIDCR)

Abbreviated Title: PTH-Independent Effects of Encaleret               PI: Iris Hartley, M.D.
Version: 10MAR2025                                                                      Page 1
Abbreviated Title: PTH-Independent Effects of Encaleret
NIH IRB #: 001085
Version Date: 10MAR2025
Title: Phase 2 study of the PTH-independent Effects of Encaleret on Mineral Homeostasis in 
subjects with post-surgical hypoparathyroidism (PSH)  
Principal Investigator: 
NIH Principal Investigator:
Iris Hartley, MD
Skeletal Disorders and Mineral Homeostasis Section
NIDCR
Building 30, Rm 228 30  Convent Dr.
Bethesda, MD 20892
Phone: 301-814-5715
E-mail: iris.hartley@nih.gov
Investigational Agents (if applicable):
Drug Name:
Encaleret
IND Number:
163887
Sponsor:
NIDCR
Manufacturer:
Calcilytix Therapeutics, Inc., 
a BridgeBio Company

Abbreviated Title: PTH-Independent Effects of Encaleret               PI: Iris Hartley, M.D.
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TABLE OF CONTENTS 
TABLE OF CONTENTS ..........................................................................................................2
STATEMENT OF COMPLIANCE ......................................................................................6
1
PROTOCOL SUMMARY.................................................................................................7
1.1
Synopsis...................................................................................................................7
1.2
Schema ..................................................................................................................11
1.3
Schedule of Activities (SOA)................................................................................12
2
INTRODUCTION ...........................................................................................................17
2.1
Study Rationale .....................................................................................................17
2.2
Background ...........................................................................................................18
2.3
Risk/Benefit Assessment.......................................................................................22
2.3.1
Known Potential Risks.......................................................................................22
2.3.2
Known Potential Benefits ..................................................................................25
2.3.3
Assessment of Potential Risks and Benefits......................................................25
3
OBJECTIVES AND ENDPOINTS.................................................................................25
4
STUDY DESIGN ............................................................................................................29
4.1
Overall Design.......................................................................................................29
4.2
Scientific Rationale for Study Design...................................................................29
4.3
Justification for Dose.............................................................................................30
5
STUDY POPULATION..................................................................................................30
5.1
Inclusion Criteria...................................................................................................30
5.2
Exclusion Criteria..................................................................................................31
5.3
Inclusion of Vulnerable Participants .....................................................................34
5.3.1
Participation of NIH Staff or family members of study team members............34
5.4
Inclusion of Pregnant Women, fetuses, or neonates .............................................34
5.5
Lifestyle Considerations........................................................................................34
5.6
Screen Failures ......................................................................................................35
5.7
Strategies for Recruitment and Retention .............................................................35
5.7.1
Compensation ....................................................................................................35
6
STUDY INTERVENTION .............................................................................................36
6.1
Study Interventions(s) Administration ..................................................................36
6.1.1
Study Intervention Description..........................................................................36

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6.1.2
Dosing and Administration................................................................................36
6.2
Preparation/Handling/Storage/Accountability ......................................................38
6.2.1
Acquisition and Accountability .........................................................................38
6.2.2
Formulation, Appearance, Packaging, and Labeling.........................................38
6.2.3
Product Storage and Stability.............................................................................38
6.2.4
Preparation.........................................................................................................38
6.3
Measures to Minimize Bias: Randomization and Blinding...................................38
6.4
Study Intervention Compliance.............................................................................38
6.5
Concomitant Therapy............................................................................................39
7
STUDY INTERVENTION DISCONTINUATION AND PARTICIPANT 
DISCONTINUATION/WITHDRAWAL ...............................................................................39
7.1
Discontinuation of Study Intervention ..................................................................39
7.2 Participant Discontinuation/Withdrawal from the Study ..............................................39
7.3
Lost to Follow-up ..................................................................................................40
8
STUDY ASSESSMENTS AND PROCEDURES...........................................................40
8.1
Screening Procedures ............................................................................................40
8.1.1
Screening activities performed prior to obtaining informed consent.................40
8.1.2
Screening activities performed after a consent for screening has been signed..41
8.2
Study Evaluation & Procedures ............................................................................41
8.2.1
Biospecimen Evaluations...................................................................................42
8.2.2
Correlative Studies for Research/Pharmacokinetic Studies...............................43
8.3
Adverse Events and Serious Adverse Events........................................................44
8.3.1
Definition of Adverse Event..............................................................................44
8.3.2
Definition of Serious Adverse Events (SAE) ....................................................45
8.3.3
Classification of an Adverse Event....................................................................45
8.3.5
Time Period and Frequency for Event Assessment and Follow-Up..................46
8.3.6
Adverse Event Reporting...................................................................................47
8.3.7
Serious Adverse Event Reporting......................................................................47
8.3.8
NIH Intramural IRB Reporting of IND Safety Reports.....................................48
8.3.9
Events of Special Interest...................................................................................48
8.3.10
Reporting of Pregnancy .....................................................................................50
8.4
Unanticipated Problems ........................................................................................50
8.4.1
Definition of Unanticipated Problems (UP) ......................................................50

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8.4.2
Unanticipated Problem Reporting......................................................................50
9
STATISTICAL CONSIDERATIONS ............................................................................51
9.1
Statistical Hypothesis ............................................................................................51
9.2
Sample Size Determination...................................................................................51
9.3
Populations for Analyses.......................................................................................51
9.3.1
Evaluable for toxicity.........................................................................................52
9.3.2
Evaluable for objective response .......................................................................52
9.3.3
Evaluable Non-Target Disease Response..........................................................52
9.4
Statistical Analyses................................................................................................52
9.4.1
General Approach..............................................................................................52
9.4.2
Analysis of the Primary Endpoints ....................................................................52
9.4.3
Analysis of the Secondary Endpoint(s)..............................................................52
9.4.4
Safety Analyses..................................................................................................52
9.4.5
Baseline Descriptive Statistics...........................................................................53
9.4.6
Planned Interim Analyses ..................................................................................53
9.4.7
Sub-Group Analyses..........................................................................................53
9.4.8
Tabulation of individual Participant Data..........................................................53
9.4.9
Exploratory Analyses.........................................................................................53
10
REGULATORY AND OPERATIONAL CONSIDERATIONS....................................53
10.1
Informed Consent Process.....................................................................................53
10.1.1
Consent Procedures and Documentation ...........................................................53
10.1.2
Consent for minors when they reach the age of majority..................................54
10.1.3
Considerations for Consent of NIH staff, or family members of study team 
members...........................................................................................................................54
10.1.4
Consent of Participants who are, or become, decisionally impaired.................54
10.2
Study Discontinuation and Closure.......................................................................55
10.3
Confidentiality and Privacy...................................................................................55
10.4
Future use of Stored Specimens and Data.............................................................56
10.5
Safety Oversight....................................................................................................57
10.6
Clinical Monitoring ...............................................................................................57
10.7
Quality Assurance and Quality Control ................................................................58
10.8
Data Handling and Record Keeping......................................................................58
10.8.1
Data Collection and Management Responsibilities...........................................58

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10.8.2
Study Records Retention....................................................................................58
10.9
Protocol Deviations and Non-Compliance............................................................59
10.9.1
NIH Definition of Protocol Deviation ...............................................................59
10.10
Publication and Data Sharing Policy.....................................................................59
10.10.1 Human Data Sharing Plan..................................................................................59
10.10.2 Genomic Data Sharing Compliance...................................................................59
10.11
Collaborative Agreements.....................................................................................59
10.11.1 Agreement Type.................................................................................................59
10.12
Conflict of Interest Policy .....................................................................................60
11
ABBREVIATIONS .........................................................................................................60
12
REFERENCES ................................................................................................................61

Abbreviated Title: PTH-Independent Effects of Encaleret               PI: Iris Hartley, M.D.
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STATEMENT OF COMPLIANCE
The trial will be carried out in accordance with International Council for Harmonisation Good 
Clinical Practice (ICH GCP) and the following: 
• United States (US) Code of Federal Regulations (CFR) applicable to clinical studies (45 
CFR Part 46, 21 CFR Part 50, 21 CFR Part 56, 21 CFR Part 312, and/or 21 CFR Part 
812) 
National Institutes of Health (NIH)-funded investigators and clinical trial site staff who are 
responsible for the conduct, management, or oversight of NIH-funded clinical trials have 
completed Human Subjects Protection and ICH GCP Training.
The protocol, informed consent form(s), recruitment materials, and all participant materials 
will be submitted to the Institutional Review Board (IRB) for review and approval.  Approval 
of both the protocol and the consent form must be obtained before any participant is enrolled.  
Any amendment to the protocol will require review and approval by the IRB before the changes 
are implemented to the study.  In addition, all changes to the consent form will be IRB-
approved; an IRB determination will be made regarding whether a new consent needs to be 
obtained from participants who provided consent, using a previously approved consent form.

Abbreviated Title: PTH-Independent Effects of Encaleret               PI: Iris Hartley, M.D.
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1
PROTOCOL SUMMARY
1.1
Synopsis
Title:
Phase 2 study of the PTH-independent Effects of Encaleret on 
Mineral Homeostasis in subjects with post-surgical 
hypoparathyroidism (PSH)  
Study Description:
This will be a single-site, proof-of-principle, open-label study to 
explore the PTH-independent effects of encaleret on calcium 
homeostasis in participants with low or undetectable PTH levels 
as a result of neck surgery (PSH). 
Objectives:
Primary Objective: 
•
Evaluate the PTH-independent effects of encaleret on renal 
calcium handling in participants with PSH. 
Secondary Objectives: 
•
Evaluate the ability of encaleret to normalize blood 
calcium while maintaining a normal urinary calcium in 
participants with PSH.
Tertiary/Exploratory Objectives:
•
Evaluate the ability of encaleret to increase serum iPTH 
levels in participants with PSH. 
•
Evaluate the effect of encaleret on 1-alpha hydroxylase 
action by measuring 1,25-(OH)2 Vitamin D levels.
•
Explore the dynamic effect of encaleret on blood and 
urinary calcium, iPTH, cAMP, 1,25-(OH)2 Vitamin D, 
and urinary citrate.
•
Evaluate the effect of encaleret on bone turnover in 
participants with PSH. 
•
Evaluate the effect of encaleret on phosphate, magnesium, 
and FGF23 levels.
•
Explore the effects of encaleret on 24-hour urine markers 
that impact stone formation 
•
Examine the PK of encaleret in participants with PSH and 
explore PK-PD interactions.
•
Explore the effect of encaleret on bone and mineral 
homeostasis in the following sub-groups, as defined in 
Section 9.3:
o
Permanent hypoparathyroidism (Cohort 1)
o
Recent hypoparathyroidism (Cohort 2)
o
“PTH-Clamp” cohort
o
“Aparathyroid” cohort 
o
Hyperthyroid cohort
o
Normothyroid cohort
o
Thyroid cancer cohort

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2
Primary Endpoint: 
•
Percent change in Fractional Excretion of Calcium (FECa) 
from baseline (Day -1) to the final day of treatment (Day 6 
or the last measurement while on encaleret). FECa 
calculated using fasting blood levels and spot urine 
collection. 
Secondary Endpoints: 
•
Proportion of participants who achieve a concomitant 
normal or elevated fasting blood calcium (albumin-
corrected calcium >8.5 mg/dL) and a normal 24-hour 
urinary calcium level (<250 mg/24 hours for women, <300 
mg/24 hours for men) on encaleret at any point between 
day 1 and day 5.
Tertiary/Exploratory Endpoints: 
•
Percent change in Fractional Excretion of Calcium (FECa) 
from baseline (Screening visit) to the final day of 
treatment (Day 6 or the last measurement while on 
encaleret). FECa calculated using fasting blood levels and 
spot urine collection. 
•
Change in blood iPTH comparing average baseline iPTH 
to average peak iPTH on encaleret. The average baseline 
iPTH will include all baseline iPTH levels from the 
screening visit, Day -1, and pre-dose on Day 1. The 
average peak iPTH will average the peak iPTH levels on 
every day the patient is on encaleret (days 1 to 5). An 
increase in iPTH will be considered clinically significant if 
there is an increase both by 50% AND by more than 10 
pg/dL. 
•
Change in 1,25-(OH)2 Vitamin D on encaleret comparing 
the maximal level prior to receiving calcitriol (On Days 3-
5) to baseline (Average of Day 1 Pre-dose levels). Increase 
will be considered significant if there is an increase of 
more than 50%. Participants who receive calcitriol prior to 
Day 3 will be excluded.
•
Pharmacodynamic endpoints measured over 5 days of 
encaleret therapy:

Abbreviated Title: PTH-Independent Effects of Encaleret               PI: Iris Hartley, M.D.
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o
Blood iPTH – Absolute levels and change from 
baseline  
o
Albumin-corrected blood calcium – Absolute 
levels and change from baseline
o
Ionized Calcium – Absolute levels and change 
from baseline
o
Urinary calcium clearance (fractional excretion and 
24-hour total excretion) – Absolute levels and 
change from baseline
o
Serum levels of 1,25-(OH)2 Vitamin D – Absolute 
levels and change from baseline
o
Blood intact FGF23 (iFGF23) and C-terminal 
FGF23 (cFGF23) – Absolute levels and change 
from baseline
o
Urine cAMP and citrate – Absolute levels and 
change from baseline
o
Blood bone resorption marker, collagen cross-
linked C-telopeptide (CTx) – Absolute levels and 
change from baseline
o
Blood bone formation marker, blood procollagen 
type 1 N-propeptide (P1NP) – Absolute levels and 
change from baseline
•
PK parameters such as maximum plasma concentration 
Cmax), time to maximum plasma concentration (tmax), 
apparent terminal half-life (t½). 
•
Change in components of urine including: supersaturation, 
sodium, potassium, calcium, magnesium, chloride, 
phosphorus, sulfate, citrate excretion, oxalate, pH, uric 
acid, creatinine, osmolality, ammonium, urea nitrogen, 
protein catabolic rate
Study Population:
Enrollment up to 30 male or female participants to achieve 15 to 
enter the treatment phase. Two cohorts: 
Cohort 1: Permanent PSH (>1 year after surgery) with minimum 
of 7 and up to 10 participants
Cohort 2: Recent PSH (<1 year after surgery) with up to 5 
participants
Phase:
Phase 2
Description of 
Sites/Facilities 
Enrolling 
Participants:
National Institutes of Health (NIH) Clinical Center (CC) 
Description of Study 
Intervention:
Encaleret will be provided as an oral film-coated tablet. Each 
tablet contains 54 mg of encaleret as 60 mg of encaleret sulfate 
(CLTX-305). Participants will receive 3 tablets twice a day (BID). 

Abbreviated Title: PTH-Independent Effects of Encaleret               PI: Iris Hartley, M.D.
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Study Duration:
Estimated time from when the study opens to enrollment until 
completion of data analyses is approximately 12 months.
Participant 
Duration:
Total duration of study participation will be 101 to 277days for 
each subject including between 4 and180 days between the 
screening visit and initiation of therapy, and 90 day follow up 
after discontinuation of the study drug.

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1.2
Schema
Figure 1: Overall Study Schematic 
PP = post-prandial
Figure 2: Treatment Schematic
SOC = Standard of care, BID = twice a day; TID = three times a day; PRN = as needed. 
Rescue calcium and calcitriol and encaleret discontinuation per Table D.

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1.3
Schedule of Activities (SOA)
Table A Schedule of Activities
NIH CC Inpatient 
Treatment Visit
Screening
Admission
BID Dosing
Discharge
FU 
Lab7
Lab 
Phone  
FU8
30-
Day 
Phone 
FU9
90-Day 
Phone 
FU10
Days
-180 to -2
-2 OR
 -1
-1
1
2
3
4
5
6
8-12
9-15
30 ± 7
90 ± 7
Informed 
Consent
X
Admission 
to clinic/
inpatient 
floor1
X
X
Demographi
cs, Medical 
history
X
Eligibility 
assessment 
X
Height
X
Weight
X
X
X
Vital signs2
X
X
X
X
X
X
X
X
Physical 
examination
X
X
X
Aes and 
SAEs, Prior/
Concomitant 
meds
X
X
X
X
X
X
X
X
X
X
X
X
NPO at 
midnight for 
morning 
fasting labs; 
water and 
medications 
ok 
X
X
X
X
X
X
X
Encaleret 
162 mg q12h
X
X
X
X
X
Calcium 
Carbonate, 
individualize
d dosages
X
X
X
X
X
X
Nutritionist 
Visit
X
Quantify 
dietary 
calcium 
intake 
X
X
X
X
X
X

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Stop 
magnesium 
and 
potassium 
citrate (last 
doses on day 
-3)
X
X
Stop 
activated 
vitamin D 
and baseline 
calcium 
supplements 
(last doses 
on day -2)3
X
Start 
calcitriol if 
cCa < 8.5 
mg/dL3
X
X
X
Discharge, 
resume 
conventional 
therapy
X
Telephone 
Contact
X
X
X
Screening 
Lab Tests4
X
Safety 
laboratory 
testing5
X
Evening 
mineral 
panel (Ca, 
Mg, PO4, 
albumin)
X
Blood β-
HCG 
pregnancy 
test 
(WOCBP 
only)
X
X
X
BloodSampli
ng6
X
X
X
X
X
X
24-hour 
Urine (Ca, 
Mg, PO4, 
Cr, Na, K, 
Citrate, pH)
X
X
X
X
X
X
X
Timed 
interval 
urine 
collections7
X
X
X
X
X
Renal 
Ultrasound
X
ECG, 12-
lead
X
X
X
X
X
X
X

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Abbreviations: Adverse Event = AE; Albumin = Alb; Electrocardiogram = ECG; BID = Twice daily; Blood Pressure = BP; 
Calcium = Ca; Chloride = Cl; Concomitant Medication = Con. Meds; Creatinine = Cr; Early Termination = (ET); End of 
Treatment = EoT. 
Follow-up = FU; Heart Rate = HR; Lactate Dehydrogenase = LDH; Intact Parathyroid Hormone = iPTH; Magnesium = Mg; 
NPO = Nothing by mouth; National Institute of Health Clinical Center = NIH CC; Parathyroid Hormone = PTH; Phosphate = 
PO4; Phosphorus = P; Potassium = K; Prothrombin Time/ Prothrombin Time = PT/INR; Red Blood Cell Count = RBC; 
Thromboplastin Time = PTT; Serious Adverse Event = SAE; Women of Childbearing Potential = WOCBP
1 Participants may complete the Screening Visit as outpatients or be housed overnight at NIH CC. 
Participants who complete the screening visit midweek have the option to stay overnight at NIH 
CC (or at local housing) during the intervening days prior to the start of Day -1. Participants also 
have the option of travel to be local to the NIH on day -2 and stay at NIH housing (e.g., The 
Edmond J. Safra Family Lodge) if available. Participants have the option of being admitted on 
Day -2 or Day -1. 
2 Vital signs include supine or sitting blood pressure (BP) by automated cuff, heart rate (HR), and 
respiratory rate, to be collected q8 hours during in-patient days. 
3 Algorithm for calcium/calcitriol titration and encaleret stopping criteria found in Table D 
4 Screening lab tests: CBC, Acute care panel, ionized calcium, eGFR, Liver Function Panel, mineral 
panel, iPTH, 25-OH Vitamin D, Lipid panel, CK, LDH, amylase, lipase, uric acid, Coagulation 
(PT/PTT/INR), urinalysis, HIV, Viral Hepatitis panel, FSH level test (postmenopausal women), 
spot urine: calcium, magnesium, phosphate, creatinine, and cAMP. TSH, Free T4
5 Safety lab tests: BMP, calcium, albumin, magnesium, phosphate, iPTH.
6 See Table B and C. Note attempts will be made to collect fasting calcium levels prior to the morning 
calcium dosage, however, calcium will be given to participants if clinically indicated (for 
example, in the setting of hypocalcemia). 
7 Participants instructed to obtain outpatient laboratory testing, approximately 3-7 days after discharge 
from NIH CC. 
8 Research team will contact the subject to review test results and provide guidance regarding clinical 
management as they transition to prior clinical care providers. 
9 All participants will receive a FU call within 30 ± 7 days after last dose of the encaleret. If subject 
discontinues from the study early (ET), they will resume prior medication regimen, and study team 
will arrange FU labs within 3-7 days and FU calls at 30 ± 7 days and 90 ± 7 days after the last dose of 
encaleret as long as subject agrees.
10 Final close out phone call will assess for any unintended pregnancies in either the patient or a 
sexual partner. 

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Table B: Urine Assays
Day 1-5 Timepoints relative to AM dose +/- 20 min. 
PM dose given at +12 hrs +/- 30 min, given after 12 hr 
timepoint lab draw
 
Daily Urine Assays
Spot Urine Measurement
Ca, Mg, PO4, Cr, cAMP
Day -1 (fasting) 
Day 1, Time 0
Osmolality, cAMP
Day 1, Time 0
Day 1-5: 16-24 hr
   Timed Interval Urine
   Ca, Mg, PO4, Crvolume
Day 1-5: 
0-4 hr, 4-12 hr, 12-16 hr, 16-24 hr
   24-Hour urine: 
Days -1 to 5
0-24 hrs
Ca, Mg, PO4, Cr, Na, 
K, pH, Citrate
(Start collection after first morning void and end 24 hours 
later)
Supersaturation Panel
Day -1 and Day 5

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Table C: Blood Sampling Days -1 to 5
Day -1:  Baseline fasting labs including CBC, acute care panel, intact PTH, Ca, PO4, Mg, Cr, 
albumin, K, CK, Research blood, Bone turnover markers (CTX, P1NP), 25-(OH) Vitamin D, 
1,25-(OH)2 Vitamin D, cAMP, ionized calcium, TSH, FT4
a

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2
INTRODUCTION
2.1
Study Rationale
This study will explore the PTH-independent effects of encaleret on calcium homeostasis in 
patients with low or undetectable PTH levels as a result of neck surgery (post-surgical 
hypoparathyroidism; PSH). 
Hypoparathyroidism is characterized by an inappropriately low level of PTH which results in 
hypocalcemia. Inadequate PTH-secretion results in lower levels of endogenous 1,25-(OH)2 
Vitamin D (decreasing calcium absorption from the gut), lower levels of calcium reabsorption 
in the kidney (leading to hypercalciuria), and decreased PTH-mediated bone resorption 
(decreasing calcium release from the bone). 
Conventional therapy with oral calcium and calcitriol, often causes hypercalciuria, which is 
associated with long-term morbidity including nephrolithiasis, nephrocalcinosis and chronic 
kidney disease (Khan et al 2018, Li et al 2018). Managing patients with hypoparathyroidism 
is a challenging balance between increasing blood calcium while minimizing hypercalciuria 
(Gafni and Collins, 2019). 
To avert symptoms of hypocalcemia, patients with PSH usually require a blood calcium in the 
normal range. This often results in hypercalciuria and renal calcification, which in some cases 
leads to loss of renal function, including the need for dialysis and transplantation. As such, 
there is a significant unmet need in treating patients with PSH.
Encaleret is a negative allosteric modulator of the calcium-sensing receptor (CaSR), also 
known as a calcilytic, which decreases the sensitivity of the CaSR to calcium, resulting in 
decreased renal calcium excretion, and in patients with intact parathyroid glands, increased 
PTH secretion. Pre-clinical studies have showed that calcilytics shift the IC50 of the calcium-
PTH curve to the right (See IB Section 4.2.3 In Vivo Studies). In cellular and animal models 
of both post-surgical and genetic forms of hypoparathyroidism due to CaSR gain-of-function 
variants, calcilytics have been shown to shift the CaSR ‘set-point’ so as to increase renal 
reabsorption and PTH secretion (in animals with intact parathyroid glands), resulting in 
increased blood calcium (Loupy et al, 2012; Dong et al, 2015; Hannan et al, 2015). 
Recent and ongoing phase 2 studies of encaleret in Autosomal Dominant Hypocalcemia type 
1 (ADH1) due to gain-of-function variants in the CaSR, confirm the ability of encaleret to 
decrease urinary calcium and raise blood calcium. However, the net effect of encaleret on 
urinary and blood calcium in this situation is a result of the combined effect of both renal CaSR 
inactivation and increased PTH signaling. Patients with ADH1 have intact and functional 
parathyroid glands, so there is a rapid and robust increase in PTH secretion with encaleret 
therapy. To understand the PTH-independent effects of encaleret on calcium homeostasis, we 
will study patients with PSH treated with encaleret. The results of this study may also inform 
the potential role of encaleret in treating patients with PSH.
While it is predicted that calcilytics will act primarily at the kidneys in PSH to increase calcium 
reabsorption, this study also has the potential to inform the PTH-independent effects of 
encaleret on other aspects of bone and mineral homeostasis, such as active vitamin D (1,25 
dihydroxyvitamin D) generation from action on 1-α hydroxylase, and/or bone turnover.

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There is also the theoretical possibility that encaleret may have the ability to increase PTH 
secretion in patients with PSH with residual but clinically insufficient parathyroid function. If 
this occurs, it may even be the case that encaleret treatment could restore a normal level of 
parathyroid function over time. 
In this exploratory proof-of-principle study, patients with PSH will be treated with encaleret 
in order to further our understanding of the PTH-independent effects of CaSR modulation. In 
addition, this study may provide clinically relevant information about how encaleret could be 
used as either an independent or adjuvant therapy for patients with PSH.  
Our primary analyses will include all participants who received at least one dose of the study 
drug. However, because patients with PSH have variable residual parathyroid tissue, we will 
also perform sub-group analyses on a “PTH-Clamp” population defined as those whose iPTH 
do not increase more than 10 pg/mL on encaleret and a “Aparathyroid” population defined as 
those whose absolute iPTH level are less than 10 pg/dl throughout the study. The biochemical 
response of these subpopulations may more accurately reflect the PTH-independent effects of 
CaSR modulation.
A small cohort of patients who developed PSH within the last year, and have not proven to 
have permanent PSH, will also be included in this study. These patients may have reversible 
parathyroid gland damage. They are included to explore whether maximal PTH stimulation 
by a calcilytic can transiently increase PTH secretion in healing parathyroid glands.
2.2
Background 
Encaleret (known previously as CLTX-305, JTT-305 or MK-5442), is an oral calcium-sensing 
receptor (CaSR) antagonist (calcilytic), currently in phase 2 study for the treatment of 
autosomal dominant hypocalcemia type 1 (ADH1). 
Encaleret was initially developed as a treatment for osteoporosis by Japan Tobacco Inc., (JTI) 
and Merck, Sharp & Dohme Corp., (Merck); Healthy volunteers and postmenopausal women 
with osteoporosis participated in a 1,766-subject program of which 1,280 were exposed to 
encaleret in eight phase 1 and four phase 2 studies including exposures up to 52 weeks. No 
specific safety issues or signals were seen with acute dosing of encaleret sulfate up to 100 mg 
and chronic dosing up to 15 mg QD. Despite early data demonstrating a potential net benefit 
on bone formation, late phase trials failed to demonstrate efficacy on endpoints of bone mineral 
density (BMD) in postmenopausal women with osteoporosis and the drug was abandoned as a 
therapy for osteoporosis.
Hypercalcemia was identified as an on-target, dose-limiting side effect in the osteoporosis 
program. Increases in blood calcium that led to hypercalcemia were a safety issue in the 
osteoporosis program. However, increases in blood calcium would be therapeutic for patients 
with hypoparathyroidism. A recent phase 2 clinical trial of 13 patients with ADH1 over 24 
weeks, followed by a 2-year long-term extension phase that is ongoing, has shown encaleret 
can increase blood PTH and calcium, and decrease urinary calcium excretion. In PSH, deficient 
parathyroid glands should limit the ability of encaleret to increase PTH. Thus, the primary 
therapeutic effect of encaleret in PSH is expected to be an increase in renal calcium 
reabsorption, although other effects on residual PTH secretion, activation of 25-hydroxy 
Vitamin D, and bone turnover, may also occur and are questions to be addressed in this study.

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The goal of this proof-of-principle study is to directly study the physiologic effects of the 
negative allosteric modulator of the CaSR, encaleret on mineral homeostasis in the absence of 
a significant PTH effect. The results will inform whether negative modulation of the CaSR by 
encaleret is able to raise blood calcium while decreasing urinary calcium in patients with PSH. 
The results will inform the possibility that encaleret may be an effective standalone or adjuvant 
drug in the treatment of postsurgical hypoparathyroidism. 
Pharmacokinetics and Product Metabolism
Encaleret (molecular formula (C29H33ClFNO4)2·H2SO4·H2O, molecular weight 1144.15) 
is formulated as 4.5, 9, 27 and 54 mg film-coated tablets. Each tablet contains 5, 10, 30, and 
60 mg of encaleret sulfate (CLTX-305), respectively. The active agent inhibits the CaSR, via 
allosteric modulation, with an IC50 of 86.2 + 6.2 nM (in cell-based assays at 2 mM 
extracellular calcium). In humans, two major glucuronide metabolites (M1 and M3) occur. M1 
(IC50 > 3000 nM) is inactive and M3 (IC50 67.3 + 6.6 nM) is active.
Encaleret is rapidly absorbed in humans (tmax median 1.5 hr. (range 0.75–3 h at most single 
doses or at steady-state). The elimination half-life (t1/2) was approximately 6.5 hours after 
single doses and 11-14 hours at steady state (14 days). Dose-proportional increases in plasma 
encaleret concentrations were documented over the encaleret sulfate dose range (5, 15, 30, 50 
and 100 mg) in the fasted state without significant food effect. Encaleret showed minimal 
accumulation when administered once daily (QD) for two weeks in Japanese postmenopausal 
women. Based on non-clinical data, fecal excretion was the main route of elimination. In 
humans, excretion of unchanged encaleret and metabolites into urine was minimal (< 5% as 
total of parent and metabolite).
The two major glucuronide metabolites showed similar pharmacokinetics as the parent drug, 
with M1 median tmax approximately 2 hr. and M3 median tmax approximately 1.5 hr. For M1 
(inactive), concentrations in plasma were approximately 2-fold higher than those of parent 
drug; M3 (active) concentrations were low (10% compared to parent). Neither M1 nor M3 
showed prolonged elimination.
No significant age-related or race differences (US population vs. Japanese subjects) were 
observed in encaleret pharmacokinetics. AUC and Cmax values may be approximately 37% 
and 30% higher in females but these differences were not significant when body weight was 
taken into account. Hepatic and renal impairment studies have not been conducted. In a drug 
interaction study, co-administration with ketoconazole, a potent CYP3A4 inhibitor, resulted in 
approximately 1.67x increase in Cmax and approximately 2x increase in AUC0-24 with 
slightly less effect on M1 and M3. 
For additional information see Investigator’s Brochure (IB), Section 4.3 and Section 5.2. 
Mineral Effects of Encaleret in Prior Clinical Trials
During the prior development program in osteoporosis, dose-related increases of endogenous 
serum parathyroid hormone (PTH) and blood calcium (Ca) were observed in subjects with 
presumed normal CaSR function (i.e., healthy volunteers and postmenopausal women with 
osteoporosis). 
In healthy postmenopausal women, repeat encaleret sulfate doses of 15 or 20 mg resulted in 
consistent elevations in intact PTH (iPTH) over 3-4 hours after single daily dosing. Encaleret 

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sulfate dosing in phase 2 studies of normocalcemic subjects was limited to 15 mg once daily 
(QD) to minimize hypercalcemia. 
With chronic once-daily dosing of encaleret sulfate up to 15 mg, albumin-corrected blood 
calcium (cCa) levels reached a plateau with up to 30% of subjects registering an elevated blood 
calcium above the upper limit of the laboratory reference range during long-term trials in 
postmenopausal women with normal systemic calcium homeostasis (normal CaSR sensitivity, 
normal parathyroid tissue). Such hypercalcemia was asymptomatic, modifiable by decreasing 
calcium/vitamin D supplementation, and/or resolved after stopping encaleret dosing. No 
serious adverse events (SAEs) related to either hyper- or hypocalcemia were observed in the 
encaleret program for osteoporosis in postmenopausal women (See IB Section 5.2). 
In phase 1 osteoporosis trials, urinary calcium excretion decreased rapidly with encaleret, 
however, the effect only persisted for the first 12 hours. With once daily doses of 5 mg to 30 
mg, 24-hour urinary calcium after 14 days of therapy was overall slightly increased (See IB 
Table 15 & 16, Figure 34). However, fractional excretion of calcium was lower than placebo 
at the 0-6 hour and 6-12 hour timepoints but elevated at the 12-24 hour timepoint. This suggests 
that the urinary calcium effect only persists for up to 12 hours and supports the use of every 
12-hour dosing for maximal and sustainable urinary calcium effect. On the highest dosage of 
encaleret of 30 mg daily, despite blood calcium elevation above 11 mg/dL, urinary fractional 
excretion of calcium during the first 12 hours was suppressed. This suggests that encaleret may 
reduce urinary calcium excretion even during concomitant elevated blood calcium, supporting 
the hypothesis that encaleret has promise as a treatment for postsurgical hypoparathyroidism. 
In period 1 of a phase 2 clinical trial of 13 individuals with ADH1, the dose of encaleret was 
escalated from 27 mg daily to 162 mg BID. In period 2, it was given at doses ranging between 
4.5 mg to 171 mg BID based on individual patient response. Individualized dosing resulted in 
a rise in iPTH, normalization of mean blood calcium, and a decreased urinary calcium 
excretion in all patients (See IB Section 5.1.4). During this trial, mild transient hypocalcemia, 
hypercalcemia, and hypophosphatemia occurred during dose titration, however no moderate 
or severe electrolyte disturbances occurred. No serious adverse events (SAEs) occurred over 6 
months of therapy. No participants discontinued the drug early, and all participants opted to 
enroll in the long-term extension of the trial. 
In summary, data from the prior osteoporosis development program showed that once daily 
encaleret increases iPTH and blood calcium, but only transiently decreased urinary calcium 
excretion suggesting that 12-hour dosing is necessary to reduce overall renal calcium excretion. 
The Phase 2B trial in ADH1 showed that BID dosing can effectively decrease urinary calcium 
excretion and normalize blood calcium in patients with confirmed activating mutations of the 
calcium sensing receptor. In both patient cohorts (ADH1 and osteoporosis) the changes in 
blood and urinary calcium were due to a combined effect of increased blood iPTH levels, and 
direct modulation of CaSR at the kidney. 
Subjects with PSH have inadequate parathyroid tissue, so encaleret’s effect on PTH will likely 
be minimal; The primary effect will be through renal CaSR modulation, which is expected to 
decrease renal calcium excretion, resulting in an increase in blood calcium. Using encaleret in 
PSH will allow us to reveal PTH-independent mineral effects of CaSR action. 
PSH: Clinical considerations

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Hypoparathyroidism has a prevalence of approximately 77,000 adults in the United States with 
the most common cause, approximately 75%, due to complications from neck surgery 
(Mannstadt et al, 2017). PSH can be classified as transient (lasting <6 months) or permanent 
(lasting longer than 6 months). The true incidence of PSH is difficult to determine as it depends 
on numerous factors including the experience of the surgeon, extent of surgery, patient risk 
factors, and diagnosis criteria. Nevertheless, it is estimated that transient PSH affects up to 25-
30% of patients undergoing total thyroidectomy, while permanent PSH occurs in up to 3% of 
patients (Mannstadt et al, 2018). 
Hypoparathyroidism is characterized by an inappropriately low level of parathyroid hormone 
(PTH), hypocalcemia and hyperphosphatemia. Inadequate PTH-secretion results in lower 
levels of endogenous 1,25-(OH)2 Vitamin D (decreasing calcium absorption from the gut), 
lower levels of calcium reabsorption in the kidney (leading to hypercalciuria), and decreased 
PTH-mediated bone resorption (decreasing calcium release from the bone). Symptoms of 
hypocalcemia include paresthesias, muscle spasms, tetany, cramps, seizures, laryngospasm, 
neuromuscular irritability, cognitive impairment, personality disturbances, and prolonged QT 
intervals. 
Conventional therapy with oral calcium and calcitriol, which includes a high pill burden and 
is cumbersome for patients, often causes hypercalciuria, which is associated with long-term 
morbidity including nephrolithiasis, nephrocalcinosis and chronic kidney disease (Khan et al 
2018, Li et al 2018). Managing patients with hypoparathyroidism is a challenging balance 
between increasing blood calcium while minimizing hypercalciuria (Gafni and Collins, 2019). 
Practically, this is done by targeting the lowest blood calcium that still relieves symptoms of 
hypocalcemia to avoid hypercalciuria.  
Recombinant human PTH 1-84 (Natpara, Takeda Inc.) was approved for the treatment of 
hypoparathyroidism, however, the effect on hypercalciuria, renal calcifications, and renal 
insufficiency is unclear (Gafni et al, 2018; Rubin et al, 2016) It is also currently unavailable in 
the US due to a prolonged recall. Long-acting PTH preparations are being developed and show 
promise, but will continue to require injections, which patients are often opposed to if 
comparable effective orally administered treatment is available.
Encaleret has the potential to fill the unmet need of an oral medication that can maintain 
eucalcemia without increasing the risk of renal calcification. By protecting patients from the 
main complications of conventional therapy (hypercalciuria, nephrolithiasis, nephrocalcinosis, 
and chronic kidney disease), encaleret could simplify the safe treatment of hypoparathyroidism 
and allow for higher serum calcium levels without higher iatrogenic risk.
PTH-Independent Mineral Effects of CaSR Modulation
The primary actions of the CaSR and PTH are closely interrelated. Because increased CaSR 
activity results in increased PTH production, identifying PTH-independent effects of CaSR 
activity is challenging. Patients with PSH, who are  PTH-deficient, are the ideal group of 
patients to unravel this complicated physiology. 
In rodents, the effect of CaSR modulation using calcilytics in PSH has been observed in a pre-
clinical study of parathyroidectomized rats, in which a calcilytic NPS2143 increased blood 
calcium levels and decreased renal calcium excretion (Loupy et al. 2012). The same small 
study, using parathyroidectomized rats on stable supplemental PTH, suggested that, in rats at 

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least, dietary intake, 1,25D levels, fecal calcium excretion, and bone resorption were 
unchanged by the calcilytic, suggesting that the effect was primarily renal. Another pre-clinical 
study focused on surgical hypoparathyroid rats with remnant parathyroid tissue from hemi-
parathyroidectomy or total parathyroidectomy with auto-transplantation (Lim et al, 2020). The 
calcilytic AXT914 increased iPTH and improved hypocalcemia, hyperphosphatemia, and 
hypercalciuria in both models. 
2.3
Risk/Benefit Assessment
2.3.1
Known Potential Risks
Encaleret has been generally well tolerated in humans during chronic treatment up to and 
beyond 12 months. In a prior osteoporosis development program, encaleret was administered 
to over 1300 healthy men and post-menopausal women; no specific safety issues or signals 
were seen with acute dosing of encaleret sulfate up to 100 mg and chronic dosing up to 15 mg 
QD. No distinct patterns of adverse events (Aes) to suggest intolerance nor evidence of toxicity 
(on- or off-target) were seen with encaleret, except for its known, on-target pharmacological 
effect to stimulate endogenous PTH hormone release and dose-related hypercalcemia (in 
euparathyroid subjects) as described above. 
In the ongoing phase 2 trial of encaleret in ADH1, encaleret was administered to 13 individuals 
with hypoparathyroidism at doses ranging from 4.5 mg to 171 mg BID for 24 weeks followed 
by an ongoing long-term extension. From the preliminary safety data (data cutoff date 27-
OCT-2021), there have been no reported serious or severe Aes or discontinuations due to Aes. 
Seventeen Aes were considered related to study treatment by the Investigator which included 
mild hypophosphatemia (n=10), mild hypercalcemia (n=6), and mild hypocalcemia (n=2). 
Treatment-related Aes of hypophosphatemia, hypercalcemia, and hypophosphatemia were 
transient and resolved either spontaneously or with adjustment of the encaleret dose. 
Hypophosphatemia and hypercalcemia were due to on-target stimulation of PTH hormone 
release, while hypocalcemia was due to the patient’s underlying hypoparathyroidism. 
Details for all previous non-clinical and clinical studies with encaleret can be found in the 
encaleret Investigator’s Brochure. 
The most common adverse events reported in early phase trials included constipation, 
headache, dizziness, nausea, vomiting, abdominal pain, back pain, and dermatitis in addition 
to increased blood calcium concentrations. None of these adverse events occurred with 
differential frequency in the larger phase 2 trials where no specific pattern of adverse events 
or clear differences were evident in Aes by System, Organ, Class between encaleret and 
placebo or comparator arms (other than differences in calcium levels).
A thorough QT study in healthy subjects showed no clinically meaningful QTc prolongation 
following a single oral dose of up to 100 mg encaleret at any of the examined timepoints. In 
patients with ADH1, who are hypocalcemic at baseline, QTc decreased towards normal on 
encaleret, in parallel with normalization of calcium and magnesium level. Of note, although 
pre-encaleret cCa levels in this population ranged from 6.4 to 9 mg/dL, no subjects had QTcF 
or QTcB interval >480 msec.
In preclinical safety and toxicology studies, the dose-limiting effects of encaleret were related 
to mechanism-based elevations in serum calcium concentrations and effects on calcium 

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homeostasis. In contrast, no off-target or other tissue or organ-specific toxicities were 
identified.
The metabolism and elimination of encaleret in preclinical studies has been conducted.   Based 
on non-clinical data, fecal excretion was the main route of elimination. In humans, excretion 
of unchanged encaleret and metabolites into urine was minimal (< 5% as total of parent and 
metabolite). The two major glucuronide metabolites (M1, M3) showed similar 
pharmacokinetics as the parent drug, with M1 median tmax ~2 hr. and M3 median tmax ~1.5 
hr. For M1 (inactive), concentrations in plasma were approximately 2-fold higher than those 
of parent drug; M3 (active) concentrations were low (10% compared to parent). Neither M1 
nor M3 showed prolonged elimination (see Investigator Brochure for details). Encaleret has 
not been formally studied in patients with severe to moderate renal impairment but significant 
dose adjustments in this population are not expected given elimination pathway and in the 
setting of the protocol dose escalation safety review process.  
In a human drug interaction study, encaleret co-administration with ketoconazole, a potent 
CYP3A4 inhibitor, resulted in ~1.67x increase in Cmax and ~2x increase in AUC0-24 with 
slightly less effect on M1 and M3.
The potential for skin phototoxicity in humans is expected to be minimal based on the tissue 
distribution in rats and estimated human dosage, but participants may be at increased risk to 
natural or artificial sunlight (tanning beds or ultraviolet A/B light (UVA/B) treatment). 
Participants at increased risk to UV injury are encouraged to minimize or avoid exposure to 
natural or artificial sunlight (tanning beds or UVA/B treatment), wear sun-protective clothing, 
and use sunscreen that strongly absorbs ultraviolet A light (UVA). A carcinogenicity rat study 
showed an increased risk of osteosarcoma in rats receiving the highest exposure of encaleret 
(80 mg/kg/day) for more than a year. 360 rats were exposed to daily encaleret for up to 2 years 
during this study. No osteosarcoma was observed in the 10 mg/kg/day or 30 mg/kg/day dosage 
groups. In these wild-type rats, high encaleret doses resulted in excessive PTH secretion. 
To put this in context, it’s important to note that PTH analogs have also been shown to increase 
the incidence of osteosarcomas in rats in a dose-dependent manner (Vahle et al, 2002). A long-
term study of PTH 1-34 in cynomolgus monkeys showed no evidence of bone tumors (Vahle 
et al, 2008). On the basis of the preclinical rat studies, pharmacologic PTH and PTH-like 
products included a black box warning about risk of osteosarcoma. A 15-year Osteosarcoma 
Surveillance Study did not identify an increase in osteosarcoma associated with use of PTH 1-
34 (Gilsenan et al, 2021). The FDA removed the black box warning for teriparatide (PTH 1-
34) and abaloparatide (a PTH-related drug) in 2021 and 2022 respectively. Nevertheless, due 
to the pre-clinical rat studies and the limitations of post-marketing studies, ‘potential risk of 
osteosarcoma’ is still included in the safety information for all PTH analogs. 
Risk to participants in this study is likely very low. Participants in this study have insufficient 
parathyroid tissue, so encaleret is not expected to substantially increase PTH levels. In the 
first 6 participants with PSH exposed to encaleret, PTH remained in the low or low-normal 
range on encaleret. Participants are also exposed to encaleret for only 5 days in this study, 
much less than in the rat study (more than a year). Participants in this protocol will also 
receive an encaleret dose of 162 mg BID, a substantially lower exposure than the rats who 
developed osteosarcoma.  

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Furthermore, bone physiology in rats and humans are fundamentally different. Importantly, 
rats have open growth plates and experience longitudinal growth for most of their lives while 
human growth plates close prior to adulthood. Open growth plates are presumed to be a risk 
factor for the development of osteosarcomas. All participants in our study are adults with 
closed growth plates. 
It is not possible to know conclusively whether bone cancer in rats was caused by encaleret or 
high PTH. It is also difficult to know if the findings in rats are relevant to humans because of 
differences between the bones of rats and humans. At this time, it is not known if there is truly 
an increased risk for osteosarcoma in humans treated with encaleret. In this study, the lower 
dose and duration of encaleret decreases the possible risk. As a precaution, this study does not 
allow people with an increased risk of osteosarcoma to participate.
It is not known if encaleret could have an effect on pregnancy or breastfeeding in humans. 
Encaleret may have potential teratogenic effects in humans based on the results of a 
reproductive toxicity study in rabbits where the incidence of skeletal anomalies (fusion of the 
sternebra) was increased in the fetuses at 30 mg/kg and above. Currently, Women of 
Childbearing Potential (WOCBP) will be consented to receive pregnancy testing at screening 
and at intervals throughout the trial and required to utilize contraception and agree to avoid 
pregnancy during the experimental treatment. 
During this week-long inpatient study, hypoparathyroid participants on encaleret may 
experience fluctuations in their blood calcium levels including the potential for hypocalcemia 
and/or hypercalcemia. The long-term risk of such fluctuations with encaleret are not expected 
to be larger than the risk of current therapy, however it is possible such fluctuations may be 
more frequent during this proof-of-principle study. Notably, because these patients have 
insufficient functional parathyroid tissue, the risk for hypercalcemia is expected to be 
significantly less than the risk was in the previous studies of patients with ADH1 or 
premenopausal women. Similarly, hypophosphatemia that was induced by increased iPTH 
secretion in the previous study in patients with ADH1, is unlikely in this patient population. 
This study is designed to minimize the risk of untoward fluctuations in blood calcium and 
related serum chemistries: Participants will be supervised with frequent monitoring of blood 
calcium levels multiple times per day and may receive treatment for hypocalcemia or 
hypercalcemia, including oral or IV calcium and calcitriol as needed. To reduce the risk of 
symptomatic hypocalcemia or hypercalcemia, participants will be given a personalized robust 
calcium load based on their home calcium dosages and a starting dietary calcium of 1000 mg 
per day. Doses will be determined by an endocrinologist familiar with treating 
hypoparathyroidism and will be based on each participant’s baseline requirements and blood 
calcium levels. Additional ‘rescue’ calcium and calcitriol will be added if the patients 
experience significant symptoms of hypocalcemia or an albumin-corrected blood calcium < 7 
mg/dL (Table D). On day 3, if the albumin-corrected blood calcium continues to be persistently 
<8.5 mg/dL, calcitriol will be added at a dose determined by the investigators and based on the 
patient’s pretreatment dosages and current blood calcium. Calcium and dietary calcium will be 
adjusted as need by physician investigators trained in endocrinology. 
Additional risks and potential discomforts related to the frequent blood and urine sampling 
procedures in the supervised setting of the inpatient stays are addressed in the Informed 
Consent Document and include medical history, physical examination, renal ultrasound, and 

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ECG. During test days multiple blood and urine collections will occur introducing known 
common risks (discomfort, bruising) for blood draws and/or intravenous catheter placement 
introducing smaller risks of complications including fainting (usually a vasovagal response to 
sight or insertion of needles) or inflammation of the insertion site (including potentially pain 
and swelling) and the potential for infection or venous thrombosis. Central catheters (inserted 
via the arm or the neck) may be used to reduce subject burden during intensive sampling 
requirements. Blood sampling volumes will remain below the limits outlined in the NIH 
Guidelines for Blood Draw Limits for Research Purposes (M95-9, June 2009).
Based on the totality of the evidence acquired to date, no other organ-specific or adverse safety 
signals of potential clinical concern have been identified. Clinical trials in the new target 
population of patients with PSH will closely evaluate dose-related effects on calcium 
homeostasis and otherwise employ routine safety monitoring (For details on encaleret safety 
data, see IB Section 5.3). 
2.3.2
Known Potential Benefits
There are no definitive currently known benefits of encaleret in the target population of PSH. 
However, this proof-of-principle study could possibly identify a novel therapeutic class for 
PSH, one which might allow patients with PSH maintain eucalcemia without increasing the 
risk of renal calcification. This study may possibly identify the PTH-independent effect of 
CaSR on renal calcium reabsorption, thereby contributing the greater body of knowledge and 
could inspire future therapeutic studies. 
2.3.3
Assessment of Potential Risks and Benefits
This study is designed to minimize known potential risks (as described above) while allowing 
for the examination of the PTH-independent effect of CaSR on renal calcium reabsorption. 
This study will also address, in a proof-of-principle manner, the potential utility of encaleret 
as a therapy in patients with postsurgical hypoparathyroidism. 
The primary known risk to patients of being enrolled in this study is the risk of hypercalcemia 
or hypocalcemia. To mitigate these risks, the study is entirely inpatient, calcium will be closely 
monitored, and supplementation will be adjusted as required. An algorithm for response to 
hyper/hypocalcemia is detailed in Table D including stopping criteria for Encaleret. 
The risks of participation are reasonable relative to the medical knowledge that may be 
achieved.
3
OBJECTIVES AND ENDPOINTS
OBJECTIVES
ENDPOINTS
JUSTIFICATION 
FOR ENDPOINTS
Primary
Evaluate the PTH-
independent effects of 
encaleret on renal calcium 
Percent change in Fractional 
Excretion of Calcium (FECa) from 
baseline (Day -1) to the final day 
FECa reflects the 
relationship between 
blood calcium and 

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OBJECTIVES
ENDPOINTS
JUSTIFICATION 
FOR ENDPOINTS
handling in participants with 
PSH. 
of treatment (Day 6 or the last 
measurement while on encaleret). 
FECa calculated using fasting 
blood levels and spot urine 
collections. 
urinary calcium. 
CaSR modulation by 
encaleret is expected 
to directly affect 
FECa. If a patient 
stops encaleret early 
prior to Day 6, the 
last fasting FECa on 
encaleret 162 mg 
BID will be used for 
this endpoint.
Secondary
Evaluate the ability of 
encaleret to normalize blood 
calcium while maintaining a 
normal urinary calcium in 
participants with PSH. 
Proportion of participants who 
achieve a concomitant normal or 
elevated fasting blood calcium 
(albumin-corrected calcium >8.5 
mg/dL) and a normal 24-hour 
urinary calcium level (<250 mg/24 
hours for women, <300 mg/24 
hours for men) on encaleret at any 
point between day 1 and day 5.
Clinically relevant 
endpoint to 
determine if 
encaleret can allow 
PSH to have both 
normal blood and 
urinary calcium.  
Tertiary/Exploratory 
Evaluate the ability of 
encaleret to increase serum 
iPTH levels in participants 
with PSH. 
Change in blood iPTH comparing 
average baseline iPTH to average 
peak iPTH on encaleret. The 
average baseline iPTH will include 
all baseline iPTH levels from the 
screening visit, Day -1, and pre-
dose on Day 1. The average peak 
iPTH will average the peak iPTH 
levels on every day the patient is 
on encaleret (days 1 to 5). An 
increase in iPTH will be 
Averaging iPTH will 
prevent spurious 
excursions from 
impacting outcomes

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OBJECTIVES
ENDPOINTS
JUSTIFICATION 
FOR ENDPOINTS
considered clinically significant if 
there is an increase both by 50% 
AND by more than 10 pg/dL.
Evaluate the effect of 
encaleret on 1-alpha 
hydroxylase action by 
measuring 1,25-(OH)2 
Vitamin D levels. 
Change in 1,25-(OH)2 Vitamin D 
on encaleret comparing the 
maximal level prior to receiving 
calcitriol (On Days 3-5) to baseline 
(Average of Day 1 Pre-dose 
levels). Increase will be considered 
significant if there is an increase of 
more than 50%. Participants who 
receive calcitriol prior to Day 3 
will be excluded. 
Explore the dynamic effect 
of encaleret on blood and 
urinary calcium and citrate, 
iPTH, cAMP, and 1,25-
(OH)2 Vitamin D.
Evaluate the effect of 
encaleret on bone turnover in 
participants with PSH. 
Evaluate the effect of 
encaleret on phosphate, 
magnesium, and FGF23 
levels.
Percent change in Fractional 
Excretion of Calcium (FECa) from 
baseline (Screening visit) to the 
final day of treatment (Day 6 or the 
last measurement while on 
encaleret). FECa calculated using 
fasting blood levels and spot urine 
collection. 
Pharmacodynamic endpoints 
measured over time over 5 days of 
encaleret therapy: 
•
Blood iPTH – Absolute levels 
and change from baseline  
•
Albumin-corrected blood 
calcium - Absolute levels and 
change from baseline in cCa 
•
Ionized Calcium – Absolute 
levels and change from 
baseline
•
Urinary calcium clearance 
(fractional excretion and 24-
These endpoints will 
allow us to further 
explore the effect of 
encaleret on other 
markers of bone and 
mineral metabolism 
and identify areas for 
future study. 

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OBJECTIVES
ENDPOINTS
JUSTIFICATION 
FOR ENDPOINTS
Explore the effects of 
encaleret on 24-hour urine 
markers that impact stone 
formation
hour total excretion) - 
Absolute levels and change 
from baseline
•
Serum levels of 1,25-(OH)2 
Vitamin D - Absolute levels 
and change from baseline
•
Blood iFGF23 and cFGF23 - 
Absolute levels and change 
from baseline
•
Urine cAMP and citrate - 
Absolute levels and change 
from baseline
•
Bone resorption markers 
collagen cross-linked C-
telopeptide (CTx) - Absolute 
levels and change from 
baseline
•
Bone formation markers – 
blood procollagen type 1 N-
propeptide (P1NP) - Absolute 
levels and change from 
baseline
•
Change in components of 
urine including: 
supersaturation, sodium, 
potassium, calcium, 
magnesium, chloride, 
phosphorus, sulfate, citrate 
excretion, oxalate, pH, uric 
acid, creatinine, osmolality, 
ammonium, urea nitrogen, 
protein catabolic rate
•
Examine the PK of 
encaleret in 
participants with PSH 
and explore PK-PD 
interactions. 
•
PK parameters such as 
maximum plasma 
concentration Cmax), time to 
maximum plasma 
concentration (tmax), apparent 
terminal half-life (t½)

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OBJECTIVES
ENDPOINTS
JUSTIFICATION 
FOR ENDPOINTS
Explore the effect of 
encaleret on bone and 
mineral homeostasis in the 
following sub-groups, as 
defined in Section 9.3 
Populations for analysis:
•
Permanent 
hypoparathyroid 
(Cohort 1)
•
Recent Hypoparathyroid 
(Cohort 2)
•
“PTH-Clamp” population
•
“Aparathyroid” 
population
•
Hyperthyroid cohort
•
Normothyroid cohort
•
Thyroid cancer cohort
•
Subgroup analysis of other 
primary, secondary, and 
tertiary endpoints
Primary analysis of 
all endpoints will be 
performed on the 
entire population, but 
subgroup analysis 
will also be 
performed for 
exploratory and 
hypothesis-
generating purposes.
4
STUDY DESIGN
4.1
Overall Design
This will be a single-site, open-label, phase 2, proof-of-principle study to evaluate the PTH-
independent effects of encaleret on renal calcium handling in participants with hypocalcemia 
due to PSH. 
Up to 30 participants may be enrolled to support up to 15 participants entering the treatment 
phase of the study. Two main cohorts are planned:
Cohort 1: Permanent PSH with neck surgery ≥12 months ago (minimum 7, up to 10 
participants)
Cohort 2: Recent PSH with neck surgery <12 months ago (up to 5 participants)
4.2
Scientific Rationale for Study Design
The current clinical trial is a small proof-of-principle trial designed to explore PTH-
independent effects of encaleret on calcium homeostasis and to determine the ability of a 
calcilytic to decrease urinary calcium excretion and raise blood calcium in patients with PSH. 
Encaleret has the potential to fill the unmet need of an oral medication for PSH that can 
maintain eucalcemia without increasing the risk of hypercalciuria and renal calcifications. 
Our primary analyses will include all participants who received at least one dose of the study 
drug. However, sub-group analysis will also be performed on patients with recent PSH (cohort 
2) to explore whether maximal PTH stimulation by a calcilytic can transiently increase PTH 
secretion in healing parathyroid glands. Patients with recent PSH have the potential to either 

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have resolution of their hypoparathyroidism or progression to permanent hypoparathyroidism. 
They will likely respond to encaleret at the kidney level very similarly to cohort 1 in terms of 
the primary endpoint, FECa, because their kidneys presumably function the same. However, 
since these patients may have reversible parathyroid gland damage, they may be more likely 
to increase PTH secretion in response to maximal stimulation by encaleret. It should be noted 
that the dose of encaleret that is being used will be biologically sensed as profound 
hypocalcemia to a degree that would never be experienced by a patient with PSH and as such 
may function as a much more potent stimulator of PTH secretion.
Furthermore, because patients with PSH have variable residual parathyroid tissue, we will also 
perform exploratory sub-group analyses on a “PTH-Clamp” population whose iPTH did not 
increase more than 10 pg/mL on encaleret and a “Aparathyroid” population whose absolute 
iPTH level was less than 10 pg/dl throughout the study. The biochemical response of these 
subpopulations will likely more accurately reflect PTH-independent effects of CaSR 
modulation.
4.3
Justification for Dose
The current study proposes to initiate first-in-patient dosing in the new target population of 
participants with PSH with encaleret 162 mg BID over a 5-day inpatient admission.
Twice a day dosing is necessary to maximize and sustain the effect on renal calcium excretion. 
In previous studies in euparathyroid patients, once daily dosing did not normalize 24-hour 
urinary calcium excretion, however, calcium excretion was suppressed for the first 12 hours. 
In the ongoing Phase 2B study of patients with ADH1 due to activating CASR mutations, 
encaleret needed to be given twice daily to maintain 24-hour effects on blood and urine 
calcium. 
The present PSH cohort is expected to be protected from hypercalcemia experienced by 
previous cohorts on encaleret (normal controls or patients with osteoporosis or ADH1). This 
is because patients with PSH, who have insufficient parathyroid tissue, are unlikely to have a 
robust PTH response to encaleret. On the other hand, because of the lack of functional 
parathyroids in this patient population, these patients may be at increased risk of symptomatic 
hypocalcemia during the course of the study. Thus, maximizing the encaleret dose in this 
population is both important for the safety of the patients, to reduce risk of hypocalcemia, as 
well as increasing the probability of establishing a definitive proof-of-principle which is the 
goal of this study. 
A primary concern in this proof-of-principle study is to not make a type 2 error (not see an 
effect when one exists). Thus, we chose the highest dose that has been safely used previously 
in patients with hypoparathyroidism/ADH1 to increase the likelihood that we will see our 
predicted effect. 
5
STUDY POPULATION
5.1
Inclusion Criteria
Participants must meet the following criteria for inclusion during screening:
1. Be able to understand and sign a written informed consent form, which must be 
obtained prior to initiation of study procedures.

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2. Age ≥ 18 years 
3. Postmenopausal women are allowed to participate in this study:  
a.
Women are considered postmenopausal and not of childbearing potential if 
they have had 12 months of natural (spontaneous) amenorrhea with an 
appropriate clinical profile (e.g., age appropriate, history of vasomotor 
symptoms) or have had surgical bilateral oophorectomy (with or without 
hysterectomy) or tubal ligation at least 6 weeks prior to start of the study. In 
the case of oophorectomy alone, only when the reproductive status of the 
woman has been confirmed by follow up hormone level assessment, shall she 
be considered not of childbearing potential.
4. Body mass index (BMI) ≥ 18.5 to < 39 kg/m2
5. Have a diagnosis of PSH, either permanent PSH (Cohort 1, surgery >= 12 months 
ago) or recent PSH (Cohort 2, surgery < 12 months ago).
6. Participants must have achieved an albumin-corrected blood calcium level of 7.8-10.2 
mg/dL on conventional therapy without significant symptoms of hypocalcemia or 
hypercalcemia. 
7. Participants being treated with thiazide diuretics may be enrolled if they are willing 
and able to discontinue thiazides for at least 5 half-lives prior to initiation of encaleret 
and remain off during the study treatment period. (5 half-lives of hydrochlorothiazide 
= 75 hours; chlorothiazide = 10 hours; chlorthalidone = 12.5 days). If the thiazide is 
being used as an antihypertensive, as opposed to use as a urine calcium-lowering 
drug, alternative therapy will be offered.
8. Participants being treated with strong CYP3A4 inhibitors (including clarithromycin, 
telithromycin, nefazodone, itraconazole, ketoconazole, atazanavir, darunavir, 
indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, tipranavir) may be enrolled if 
they are willing and able to discontinue these medications for at least 5 half-lives 
prior to initiation of encaleret and remain off during the study treatment period. 
9. Participants being treated with magnesium or potassium citrate supplements should 
discontinue such treatment starting on Day -2. 
10. Participants being treated with medications that have impacts on mineral metabolism 
which investigators believe may impact study endpoints may be enrolled if they are 
willing and safely able to discontinue the medication for at least 5 half-lives prior to 
initiation of encaleret and remain off during the study treatment period
5.2
Exclusion Criteria
Participants who meet any of the following criteria during Screening will not be eligible to 
participate in the study:
1. History of treatment with any PTH analog (i.e., PTH 1-84, PTH 1-34, TransCon PTH, 
etc.) within the previous 3 months
2. History of prior treatment with encaleret
3. History of hypocalcemic seizure within the past 3 months

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4. Blood 25-OH Vitamin D level <25 or >60 ng/mL 
a.
If subject has a blood 25-OH Vitamin D level < 25 ng/mL at the screening visit, 
they will be prescribed cholecalciferol or ergocalciferol supplementation. Once 
the 25-OH Vitamin D level is >= 25 ng/mL, the subject will be eligible to 
continue to the treatment phase of the study. 
b. If a subject has a blood 25-OH Vitamin D level >60 ng/mL at the screening visit, 
their vitamin D supplementation will be adjusted. Once the 25-OH Vitamin D 
level is <=60 ng/mL, the subject will be eligible to continue to the treatment phase 
of the study. 
5. Participants with hemoglobin (Hgb) lower than the lower limit of normal. 
a. If subject has a low Hgb at the screening visit due to iron, B12, or folate 
deficiency, they will be prescribed supplementation. Once the Hgb level within 
the normal range, the subject will be eligible to continue to the treatment phase of 
the study. 
6. Abnormal laboratory values which in the opinion of the investigator, would make the 
subject not suitable for participation in the study 
7. Estimated glomerular filtration rate (eGFR) < 50 mL/minute/1.73 m2 using CKD-EPI. 
8.  Insufficient hepatic function defined as one of the following: 
- Total Bilirubin > 1.5 x ULN OR
- Aspartate transaminase (AST) > 2x ULN OR
- Alanine transaminase (ALT) > 2x ULN 
9. 12-lead resting electrocardiogram (ECG) with clinically significant abnormalities. 
Participants with screening QTcF (using the Frederica equation) > 450 milliseconds 
(ms) will not be eligible for the treatment phase of the study. 
– If a participant has a prolonged QTcF during screening due to a reversible cause of long 
QT (for example hypocalcemia or QT-prolonging medications), the subject may be 
eligible for the treatment phase of the study if the reversible cause can be addressed, and 
repeat ECG shows QTcF ≤450 milliseconds. 
10. Clinically significant cardiac disease including any of the following: 
– Congestive heart failure requiring treatment (NY Heart Association grade >= 2)
- History of clinically significant cardiac arrythmias including ventricular arrhythmias, 
atrial fibrillation, or conduction abnormalities
– History of unstable angina pectoris or acute myocardial infarction
11. Participants with positive hepatitis B surface antigen (HBsAg) or Hepatitis A 
immunoglobulin M (IgM) at the Screening Visit. Participants who are in complete 
remission from Hepatitis C as evidence by sensitive assay ≥12 weeks after completion 
of HCV therapy are allowed to participate in the study. Participants with human 
immunodeficiency virus (HIV) infection on a stable dose of anti-retroviral therapy 
who have an undetectable viral load are allowed to participate in the study.

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12. Pregnant or nursing (lactating) women, where pregnancy is defined as the state of a 
female after conception and until the termination of gestation, confirmed by a positive 
serum hCG laboratory test
13. Clinically significant abnormalities in thyroid function tests. This does not include 
participants with non-clinically significant or treated thyroid diseases (e.g. subclinical 
hypothyroidism, hypothyroidism on treatment, etc). Participants on TSH-suppression 
therapy for thyroid cancer are allowed to participate in this study regardless of TSH 
level.
14. Women of child-bearing potential, defined as all women physiologically capable of 
becoming pregnant, unless they are using highly effective methods of contraception 
during dosing and for 3 months following the discontinuation of study treatment. 
Highly effective contraception methods include:
•
Total abstinence (when this is in line with the preferred and usual lifestyle of the 
subject). Periodic abstinence (e.g., calendar, ovulation, symptothermal, post-
ovulation methods) and withdrawal are not acceptable methods of contraception.
•
Female sterilization (have had surgical bilateral oophorectomy with or without 
hysterectomy) or tubal ligation at least six weeks before taking study treatment. 
In case of oophorectomy alone, only when the reproductive status of the woman 
has been confirmed by follow up hormone level assessment.
•
Male sterilization (at least 6 months prior to screening). For female participants 
on the study the vasectomized male partner should be the sole partner for that 
subject.
•
Combination of the following (a+c or b+c):
a.
Use of oral, injected or implanted hormonal methods of contraception or 
other forms of hormonal contraception that have comparable efficacy 
(failure rate <1%), for example hormone vaginal ring or transdermal 
hormone contraception
b. Placement of an intrauterine device (IUD) or intrauterine system (IUS)
c.
Barrier method of contraception: Condom or Occlusive cap (diaphragm 
or cervical/vault caps) with spermicidal foam/gel/film/cream/vaginal 
suppository
15. Sexually active male participants who are unwilling to use a condom during vaginal 
intercourse while taking the encaleret (study drug) and for 3 months after the last dose of 
the study drug. Participants should not father a child during active participation in the 
study starting with the first encaleret dose. Condoms are not required if the subject is 
vasectomized or if the subject’s partner is not a woman of child-bearing potential.
16. Hypersensitivity to any active substance or excipient of encaleret 
17. History of drug or alcohol dependency within 12 months preceding the Screening Visit
18. Current participation in other investigational drug studies

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19. Unwillingness to refrain from blood donation within 12 weeks prior to admission visit 
through one year after the last dose of the study drug. If subject donated blood within 12 
weeks of the screening visit, they will need to wait until 12 weeks have passed since 
blood donation for the admission visit. 
20. Participants who have a history of diseases of mineral metabolism other than 
hypoparathyroidism or hyperparathyroidism which investigators believe may impact 
study endpoints (for example, X-linked hypophosphatemia, rickets, etc).
21. Participants with history of the following :
•
Any cancer except for thyroid cancer, basal cell skin cancer or squamous 
cell cancer in the last 5 years. Subjects with history of thyroid, basal cell 
or squamous cell cancers should have received definitive treatment for 
their malignancies prior to enrollment.
•
Skeletal malignancies
•
Bone metastases
•
Irradiation (radiotherapy) to the skeleton
•
Any other disease that increases the likelihood for osteosarcoma (ex. 
Paget’s disease). 
•
Unexplained elevations of alkaline phosphatase
5.3
Inclusion of Vulnerable Participants
5.3.1
Participation of NIH Staff or family members of study team members
NIH staff and family members of study team members may be enrolled in this study as this 
population meets the study entry criteria.  Neither participation nor refusal to participate as a 
subject in the research will have an effect, either beneficial or adverse, on the participant’s 
employment or position at NIH.
Every effort will be made to protect participant information, but such information may be 
available in medical records and may be available to authorized users outside of the study team 
in both an identifiable an unidentifiable manner.
The NIH Frequently Asked Questions (FAQs) for Staff Who are Considering Participation in 
NIH Research will be made available.  Please see section 10.1.3 for consent of NIH Staff.
5.4
Inclusion of Pregnant Women, fetuses, or neonates
Not applicable
5.5
Lifestyle Considerations
During this study, participants are asked to: 
•
Consume approximately 1000 mg of daily calcium from their diet, with assistance 
from a nutritionist. 
•
Refrain from donating blood at least 12 weeks prior to the admission visit to one year 
after the last dose of the drug.

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•
Refrain from eating food from midnight until the next morning during the admission 
visit
5.6
Screen Failures
Screen failures are defined as participants who consent to participate in the clinical trial but are 
not subsequently started on treatment. A minimal set of screen failure information is required 
to ensure transparent reporting of screen failure participants, to meet the Consolidated 
Standards of Reporting Trials (CONSORT) publishing requirements and to respond to queries 
from regulatory authorities. Minimal information includes demography, screen failure details, 
eligibility criteria, and any serious adverse event (SAE).
Individuals who do not meet the criteria for participation in this trial because of failing to meet 
criteria may be rescreened to reassess the specific criteria that led to screen failure. Only the 
relevant criteria need to be repeated during rescreening. Rescreened participants should be 
assigned the same participant number as for the initial screening.  
Individuals who meet criteria for participation in this trial but are unable to schedule an 
admission visit within 180 days of the screening visit, may be rescreened. Rescreened 
participants should be assigned the same participant number as for the initial screening. 
5.7
Strategies for Recruitment and Retention
Hypoparathyroidism has an estimated prevalence of 77,000 adults in North America, with 
approximately 75% of which are from PSH (Mannstadt et al, 2017). Initial recruitment will 
include contacting participants with PSH known to NIH investigators. Additional recruitment 
may proceed through referrals from worldwide clinical and research experts involved in 
parathyroid surgery and hypoparathyroidism who may be contacted by investigators using a 
recruitment flier. Finally, outreach through patient advocacy organizations worldwide may 
also be pursued.
Up to 30 participants may be enrolled to support up to 15 participants entering the treatment 
phase of the study.
Potential participants will undergo the informed consent process and be screened during an 
admission or outpatient appointment at the NIH, when they will receive explanation of the 
clinical trial procedures and requirements. Participants will receive expert clinical oversight of 
their outpatient therapeutic regimen and management from NIH investigators during the period 
from screening to the in-house admission and throughout the clinical trial. 
Participants will not be billed for any research or related clinical care that participants will 
receive at the NIH Clinical Center for this study.
5.7.1
Compensation
Participants will be compensated for participation in this clinical trial. 
Maximum compensation will be $885 at the completion of the study with compensation 
broken down as follows: 
Screening visit: $135
Admission visit: $720 ($120 per day x 6 days)

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Telephone visits: $30 ($10 x 3 telephone visits)
If subject is unable to finish the study, he/she will receive adjusted compensation for part(s) 
completed also in accordance with NIH HRPP policy 3014-302 Subject Recruitment and 
Compensation.
Air/train/bus travel will be arranged by the NIH travel agency unless there are extenuating 
circumstances requiring the subject to book his/her own travel. Miscellaneous out-of-pocket 
travel expenses (e.g., baggage receipts, airport parking, taxis) will be reimbursed if a receipt is 
provided. Participants traveling by car from > 50 miles will be reimbursed mileage per NIH 
policies. Subject copays or co-insurance for local laboratories will be paid or reimbursed if an 
invoice or receipt is provided.
6
STUDY INTERVENTION
6.1
Study Interventions(s) Administration
6.1.1
Study Intervention Description
The investigational medicinal product (IMP), encaleret, will be provided as film-coated tablets 
containing the active ingredient encaleret provided in 54 mg dosage strength. Participants will 
receive encaleret 162 mg (3 tablets) BID per protocol with water.
6.1.2
Dosing and Administration
On Day -1/-2, participants who met eligibility criteria at the screening visit will be admitted to 
the NIH CC. Participants will not take their magnesium and potassium citrate starting on the 
morning of Day -2. Participants will not take their standard-of-care calcium or calcitriol 
starting on the morning of Day -1, and will instead start a personalized calcium 
supplementation, determined by investigators from their baseline calcium requirements and 
levels. They will start on a dietary daily calcium intake of approximately 1000 mg per day, 
which may be adjusted if needed.
Encaleret 162 mg twice a day will be administered to participants on Day 1 to 5. Additional 
calcium and/or calcitriol will be administered per algorithm (Table D) if required. 
Calcium and calcitriol supplementation will be adjusted following the algorithm delineated in 
Table D with the primary goal of safety. Mild to moderate symptomatic hypocalcemia at any 
calcium level, cCa < 7 mg/dL, or borderline QT prolongation, would cause investigators to 
give oral calcium and/or calcitriol. Doses will be determined at the discretion of experienced 
investigator’s understanding of the patient’s prior supplement requirements and severity of 
hypocalcemia. IV calcium may be used for participants with severe hypocalcemic symptoms 
or QTcF > 500 ms. If a patient develops mild hypercalcemia, then calcium and calcitriol will 
be held until cCa is less than 9 mg/dL. If cCa has not trended down by 12 hours (or earlier per 
investigator discretion), encaleret will be stopped. If cCa is > 12 mg/dL, encaleret will be 
discontinued and calcium and calcitriol will be held until cCa is < 9 mg/dL, when home 
regimen is restarted.  
On Day 3, investigators will add calcitriol supplementation if the albumin-corrected calcium 
remains < 8.5 mg/dL. The calcitriol dose will be determined by investigators, taking into 
account the current calcium level and the subject’s baseline requirements. 

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The last dose of encaleret will be given on the night of Day 5. The patient will then resume 
calcium and calcitriol and be discharged home. If the patient is hypercalcaemic or 
hypocalcemic, their baseline calcium and calcitriol may be adjusted at discharge. If needed, 
they may remain at the NIH clinical center until their labs have stabilized to a safe level. 
Table D: Titration algorithm:
Drug Discontinuation
Encaleret will only be given at the 162 mg BID dosage during this study, but may be 
discontinued early in the setting of hypercalcemia per the algorithm in Table D.  
Participants who develop abnormal clinical or laboratory assessments that indicate 
continuation of the treatment may put the subject at risk, may have their encaleret dosing 
interrupted at the discretion of the principal investigator.
Participants who met specific achievement thresholds for both the primary and secondary 
endpoints may be eligible for early drug discontinuation at the discretion of the principal 
investigator. The defined thresholds are as follows: The primary endpoint will be considered 
achieved if the fasting FECa has decreased by >40%. The secondary endpoint will be 
considered achieved if the participant has achieved concomitant normal or high blood calcium 
and normal urinary calcium. This approach aims to facilitate the evaluation of the PK-PD 
relationship (exploratory endpoint) during encaleret withdrawal. 

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Calcium and calcitriol supplementation and encaleret dose will be adjusted following the 
algorithm delineated in Table D with the primary goal of safety. 
Drug Administration
Encaleret will be dispensed by the NIH Pharmacy. It will be provided as film-coated tablets 
containing the active ingredient encaleret provided in 54 mg dosage strength. Participants will 
receive encaleret 162 mg (3 tablets) every 12 hours per protocol with water. 
6.2
Preparation/Handling/Storage/Accountability 
6.2.1
Acquisition and Accountability
The encaleret tablets used in this study will be supplied under a collaborative agreement with 
the manufacturer, Calcilytix Therapeutics, Inc. This drug will be received by the NIH 
pharmacy and dispensed to the study participants by NIH clinical center staff while participants 
are admitted at the NIH clinical center. The NIH pharmacy in collaboration with the PI is 
responsible for keeping accurate records of the amount of drug dispensed, returned, and 
remaining at the conclusion of the study.
6.2.2
Formulation, Appearance, Packaging, and Labeling
The encaleret will be provided as film-coated tablets containing the active ingredient encaleret 
provided in 54 mg tablets.
The tablets contain the following excipients: mannitol, microcrystalline cellulose, colloidal 
silicon dioxide, croscarmellose sodium, sucrose fatty acid esters, hydroxypropyl 
methylcellulose, magnesium stearate, macrogol, and titanium oxide.
6.2.3
Product Storage and Stability
Industry Partner and manufacturer, Calcilytix Therapeutics, Inc., will provide the study center 
with encaleret under a collaborative agreement. Encaleret will be stored at controlled room 
temperature between 20°C and 25°C with excursions permitted between 15°C and 30°C in the 
manufacturer-provided bottles.
All participants will receive encaleret only as dispensed and administered by staff at the NIH 
CC. All unused encaleret must be returned to the Industry Partner or destroyed on-site with 
approval by the Industry Partner, after a final encaleret accountability has been completed. If 
unused encaleret is not returned to the Industry Partner, proof of destruction must be provided 
to the Industry Partner.
6.2.4
Preparation
Not applicable
6.3
Measures to Minimize Bias: Randomization and Blinding
Not Applicable.
6.4
Study Intervention Compliance
Encaleret will be administered by NIH CC staff and recorded. The time of encaleret 
administration will be documented in the appropriate Case Report Form (CRF). Scheduled oral 
administration of study drug will occur at the study site under observation by study staff or 
designee, thus ensuring study drug compliance.

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6.5
Concomitant Therapy
At Screening, the study staff at NIH will question each subject specifically on the use of all 
concomitant medications and record the medication and dosage in the appropriate CRF. In 
general, upon admission and throughout the study, NIH CC staff will monitor, record, and 
administer all concomitant medications during the inpatient stay. 
Participants being treated with thiazide diuretics may be enrolled if they are willing and able 
to discontinue thiazides for 5 half-lives prior to initiation of encaleret and during the study 
treatment period. When the thiazide is being used an antihypertensive, alternative therapy will 
be offered.
Participants being treated with strong CYP3A4 inhibitors (including clarithromycin, 
telithromycin, nefazodone, itraconazole, ketoconazole, atazanavir, darunavir, indinavir, 
lopinavir, nelfinavir, ritonavir, saquinavir, tipranavir) must discontinue these medications 
during the screening period at least 5 half-lives prior to initiation of encaleret and during the 
study treatment period. 
Participants being treated with magnesium or potassium citrate will be instructed to stop these 
at least 2 days prior to the treatment period (Day -2). 
Participants being treated with medications (other than those used for treatment of 
hypoparathyroidism) that have strong impacts on mineral metabolism may need to stop these 
medications to continue in the study, if, in the expert opinion of the study investigators, these 
medications could influence the endpoints of the study. 
7
STUDY INTERVENTION DISCONTINUATION AND PARTICIPANT 
DISCONTINUATION/WITHDRAWAL 
7.1
Discontinuation of Study Intervention
Discontinuation of the drug encaleret does not mean discontinuation from the study, and 
remaining study procedures should be completed as indicated by the study protocol. If a 
clinically significant finding is identified, the investigator or qualified designee will determine 
if any change in participant management is needed. Any new clinically relevant finding will 
be reported as an adverse event (AE). 
When encaleret is discontinued, participants will be converted back to oral calcium and active 
Vitamin D. Serial blood and urine sampling may be continued for the remainder of the inpatient 
visit, at the discretion of the investigator. Additional blood or urine sampling may be obtained 
at the discretion of the investigator for safety monitoring and/or observation of PK/PD of 
encaleret withdrawal. Follow up laboratory testing within 1 week of discontinuing encaleret 
and the three follow up telephone contacts should be completed as indicated by the study 
protocol.  
7.2 Participant Discontinuation/Withdrawal from the Study
Participants are free to withdraw from participation in the study at any time upon request.
An investigator may discontinue or withdraw a participant from the study for the following 
reasons:
•
AEs

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•
Protocol violation
•
If it is discovered that the subject did not meet protocol entry criteria, and continued 
participation would present unacceptable risk to subject’s health
•
Non-compliance with administration of the investigational medicinal product 
encaleret (IMP)
•
Withdrawal of consent: Participants may withdraw consent at any time for any reason 
without prejudice to future treatment. In the event of study withdrawal, the subject 
will be encouraged to undergo ET procedures as a final visit. 
•
Lost to follow-up
•
Pregnancy at any time after signing the ICF. 
•
Study terminated by Sponsor
•
Site closed by Sponsor
•
PI’s decision based on subject’s safety
If participants discontinue participation or are terminated early from the study, and have 
received a dose of encaleret, they should have all follow up safety assessments as listed in the 
Schedules of Assessments (including one outpatient follow up laboratory assessment and three 
telephone contacts) if the subject agrees. 
When participants are discontinued from study medication, they should be converted back to 
oral calcium and active Vitamin D. Participants will be instructed to undergo outpatient 
laboratory testing of their blood calcium within 1 week of discontinuing study medication and 
to have those results sent to NIH investigators for review. A telephone contact should be 
arranged for the investigative staff to review the blood results and advise on optimizing their 
outpatient clinical management.
All dosed participants who early terminate from the study, regardless of cause, should undergo 
a 30-day (± 7 days) and 90-day (± 7 days) follow-up telephone call after the last dose of 
encaleret. The reason for early termination from the study will be reflected in the CRF. If a 
subject early terminates from the study because of an AE, the PI/study staff must record the 
AE as the reason for subject discontinuation. 
7.3
Lost to Follow-up
Lost to follow-up is an unlikely occurrence in this study because the treatment phase is entirely 
inpatient. Prior to admission, participants that are no longer able to be contacted will be 
considered screen failures. After discharge from the treatment phase, laboratory and telephone 
follow up encounters are for safety purposes. The investigator or designee will make every 
effort to regain contact with the participant following discharge from the treatment phase of 
the study for the patient’s safety. Should the participant continue to be unreachable, he or she 
will be considered to have withdrawn from the study with a primary reason of lost to follow 
up. 
8
STUDY ASSESSMENTS AND PROCEDURES
8.1
Screening Procedures
8.1.1
Screening activities performed prior to obtaining informed consent
Prior to obtaining informed consent, prospective participants may be contacted via email, 
written, in person, video or telephone communications. With prospective subject’s permission, 

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investigators may also review existing medical records including clinical notes, laboratory 
studies, imaging, photographs/video, pathology specimens/reports, or other relevant records.
8.1.2
Screening activities performed after a consent for screening has been signed
The following activities will be performed only after the subject has signed the consent this 
study: lab assessments, imaging, physical exam. Assessments performed at outside facilities 
or on another NIH protocol within the timeframes below may also be used to determine 
eligibility once a participant has signed the consent form.
8.2
 Study Evaluation & Procedures
The following procedures and imaging assessments will occur according to Section 1.3 
Schedule of Activities.
All participants must sign the informed Consent Form (ICF) prior to any study-related 
procedures. Screening must be completed within 180 days prior to admission to the NIH CC 
(See Table A for Schedule of Activities).
Screening Visit: The first screening visit will be conducted at the NIH CC to determine subject 
eligibility, document current metabolic status, and assess dietary calcium intake. Participants 
may complete the screening assessments as outpatients or be housed overnight at NIH CC. 
Participants who complete the screening visit midweek have the option to stay overnight at 
NIH CC during the intervening days prior to Day -1. Each subject’s current treatment regimen 
will be assessed by NIH investigators in relation to presence/absence and control of 
hypocalcemia-related complaints and symptoms, and assessment of blood and urine analytes 
including blood and urine calcium and phosphate. NIH investigators may recommend 
adjustments to a subject’s outpatient regimen during the screening period, in accordance with 
the accepted goals of achieving cCa in the low normal range, while minimizing hypercalciuria. 
Unscheduled outpatient laboratory assessments, if required, will be arranged through 
outpatient laboratories with results transmitted to and reviewed by the investigators as standard 
of care. Participants who complete the screening process and meet inclusion/exclusion criteria, 
may be scheduled for admission for the treatment period of the protocol. 
Procedures/evaluations planned as part of the screening visit include: 
•
History and Physical examination
•
Height and Weight
•
Vital Signs
•
Nutritionist Assessment
•
Blood laboratory assessment 
•
Electrocardiogram (ECG)
•
24-hour urine collection (may be performed after the visit if more convenient for the 
patient)

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•
Renal Ultrasound
After completing screening assessments, any AE/SAE reported by a subject, whether or not 
study drug has been administered, will be recorded by the investigators. Any AE/SAE prior to 
dosing will be categorized as “Baseline” and any AE/SAE after dosing will be categorized as 
“treatment-emergent.”
Treatment Period: 
Day -2 or Day -1 (Admission): Participants will be admitted to the NIH CC either the day 
prior to dosing or two days prior to dosing based on subject convenience. All participants will 
be instructed to stop taking calcitriol and home calcium dosage, with last doses on Day -2. 
Participants on magnesium or potassium citrate will be instructed to stop these supplements, 
with last doses on Day -3. Calcium supplementation with calcium carbonate(500 mg elemental 
calcium) three times a day will start on Day -1. Baseline 24-hour urine will be opened the 
morning of Day -1, and fasting laboratory assessment will be obtained. Attempts will be made 
to collect fasting calcium levels prior to the morning calcium dosage, however, calcium will 
be given to participants if clinically indicated (for example, in the setting of hypocalcemia).
Days 1 to 5: Encaleret 162 mg BID will be taken orally by the patient. Detailed summary of 
planned calcium and calcitriol therapy is presented in Figure 2 and a dosing algorithm is 
presented in Table D. Frequent blood and urine sampling for 24-hours will be performed for 
safety and outcome measures (see Table A and Table B). Encaleret will be administered in the 
morning and evening with water approximately 12 hours between each dose. The last dose of 
study medication will occur on the evening of Day 5. Daily ECG will be performed for 
monitoring of QT interval.
Day 6 (Discharge): After the blood sampling is collected on the morning of Day 6 and the 24-
hour urine is closed, all participants will resume their prior conventional treatment regimen. 
During Day 6, cCa levels will be monitored until the patient is discharged. This admission can 
be extended if additional monitoring or treatment (e.g., to stabilize calcium) is needed prior to 
discharge.
Follow-up: 
Outpatient testing done on day 8-12 (Less than 7 days after expected discharge from the NIH 
clinical center) will be collected either at the NIH CC or local laboratory. Blood samples 
collected will be evaluated for blood creatinine, albumin, calcium, magnesium, phosphate, and 
PTH. A telephone contact to the patient will be conducted once calcium results are available 
to be reviewed with investigative team. Additional outpatient testing to follow up safety issues 
will be performed as needed. 
An additional two telephone contacts will be performed at 30-days (± 7 days) and 90-days (± 
7 days) after the last encaleret dose for screening of AEs and pregnancies, respectively. 
8.2.1
Biospecimen Evaluations
Screening visit and inpatient blood samples except for research samples and PK samples will 
be managed by the NIH Clinical Center laboratory. Urine samples will be either managed by 
the NIH laboratory or sent to LabCorp. Only exploratory end points, for example FGF23, will 

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be performed in non-CLIA certified labs on research samples. The primary endpoint 
assessments include evaluations of urinary excretion of calcium. The times for collection of 
these samples are detailed in the Schedule of Activities in Section 1.3. 
All PK blood samples will be analyzed by a CRO contracted by the manufacturer. Details for 
sample processing and handling will be provided in a written SOP. The times for collection of 
these samples are detailed in the Table B and C. 
The total blood volume collected for each subject will be less than the blood volume limits per 
subject as per NIH Guidelines for Blood Draw Limits for Research Purposes (M95-9, June 
2009). If a subject has a low body weight (<50 kg for adults), the blood volume taken will be 
reduced to remain within the NIH guidelines of 10.5mL/kg/8w. 
In order to characterize both the pre-study calcemic status as well as changes associated with 
experimental interventions, the protocol will rely on frequent measurement of albumin-
corrected blood calcium concentrations. Assays will be conducted according to specifications 
of the NIH Clinical Center Laboratory, Bethesda, MD. The main indicator of normal versus 
abnormal blood calcium levels will be based on the correction for serum or plasma albumin 
according to the formula corrected calcium (cCa) = measured total calcium (mg/dL) + 0.8(4 –
albumin (g/dL)) OR measured total calcium (mmol/L) + 0.2(4 –albumin (g/dL)), recognizing 
that the total calcium reported in SI units (mmol/L) can be converted to conventional units 
(mg/dL) by multiplying by 4. Given that enrolled participants are expected to have both normal 
and stable albumin levels, the measures of total calcium and cCa are likely to be similar 
throughout the time course of this study. Ionized calcium assays will also be measured at the 
NIH Clinical Center and can be used to assess calcium status for dose adjustment decisions on 
a case by case basis in addition to the albumin corrected-calcium.
8.2.2
Correlative Studies for Research/Pharmacokinetic Studies
Not applicable 
8.2.3 Description of how privacy and confidentiality of medical information/biological 
specimens will be maximized
Subject samples will be de-identified using a designated subject number and initials. 
The clinical trial database, which may be shared with appropriate regulatory agencies, in 
addition to access from the NIDCR, NIDCR PI, and investigators, will contain 
clinical/demographic data on participants’ age, ethnicity, sex, diagnosis, treatment, response 
to treatment, adverse events as per the standards of human clinical research. All shared data 
outside of the EDC will be de-identified without any link to individual identifying information. 
Safety and Other Assessments
Physical Examinations
At the times detailed in the Schedule of Activities in Section 1.2, participants will undergo a 
complete physical examination (PE), which is to be completed by a physician or an 
appropriately trained health professional. Any abnormal physical examination finding that is 
deemed clinically important (i.e., is associated with symptoms and/or requires medical 
intervention) will be recorded as an AE.
Vital Signs

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Vital signs will be assessed in accordance to times and details indicated in the Schedule of 
Activities Table A, Section 1.2. Any abnormal vital sign that is deemed clinically significant 
(i.e., is associated with symptoms and/or requires medical intervention) will be recorded as an 
AE.
Clinical Laboratory Determinations
Blood and urine samples for clinical laboratory tests will be collected at the times detailed in 
the Schedule of Activities. At Screening, the samples will be collected at the NIH Clinical 
Center. Additional testing during the Screening period may be conducted at an outpatient 
laboratory near the subject. All laboratory tests during the Treatment Period will be measured 
at the NIH Clinical Center. 
Outpatient testing done on days 8-12 (Less than 7 days after expected discharge from the NIH 
clinical center) will be collected either at the NIH CC or local laboratory. Blood samples 
collected will be evaluated for blood creatinine, albumin, calcium, magnesium, phosphate, and 
PTH. This will allow for evaluation of calcium homeostasis after cessation of encaleret. 
A telephone contact to the patient will be conducted once calcium results are available to be 
reviewed with investigative team.
At any time during the study, abnormal laboratory parameters which are clinically relevant 
(e.g., require dose interruption of study treatment, lead to clinical symptoms or signs, or require 
therapeutic intervention), whether specifically requested in the protocol or not, will be recorded 
on the Adverse Events eCRF page. 
The investigator will assess the clinical significance of values outside the reference ranges 
provided by the laboratory. 
Samples will be collected, processed, and stored according to the instructions provided in the 
Laboratory Manual.
The investigator or qualified sub-investigator will review all laboratory results for clinical 
significance. Any laboratory result deemed clinically significant (i.e., is associated with signs 
and symptoms and/or requires medical intervention) will be recorded as an AE.
Electrocardiograms
A standard 12-lead ECG will be assessed at the times detailed in the Schedule of Activities, 
Section 1.3. ECGs will be performed in the supine position after a 5-minute rest. The 
investigator or qualified sub-investigator will review all ECG interpretations and interval 
duration measurements for clinical significance. Any ECG interpretation deemed to be 
clinically significant (i.e., is associated with symptoms and/or requires medical intervention) 
will be reported as an AE.
Dietary Calcium
At screening visit participants will be educated by trained nutrition staff on aiming for dietary 
intake of 1000 mg calcium during inpatient admission. Throughout the inpatient admission at 
the clinical center, daily dietary intake of calcium will be assessed.
8.3
Adverse Events and Serious Adverse Events
8.3.1
Definition of Adverse Event

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Adverse event means any untoward medical occurrence associated with the use of an 
intervention in humans, whether or not considered intervention-related (21 CFR 312.32 (a)).
8.3.2
Definition of Serious Adverse Events (SAE)
An adverse event (AE) or suspected adverse reaction is considered "serious" if, in the view of 
either the investigator or sponsor, it results in any of the following outcomes: death, an 
immediately life-threatening adverse event, inpatient hospitalization or prolongation of 
existing hospitalization, a persistent or significant incapacity or substantial disruption of the 
ability to conduct normal life functions, or a congenital anomaly/birth defect. Important 
medical events that may not result in death, be life-threatening, or require hospitalization may 
be considered serious when, based upon appropriate medical judgment, they may jeopardize 
the participant and may require medical or surgical intervention to prevent one of the outcomes 
listed in this definition. Examples of such medical events include allergic bronchospasm 
requiring intensive treatment in an emergency room or at home, blood dyscrasias or 
convulsions that do not result in inpatient hospitalization, or the development of drug 
dependency or drug abuse.
Emergency room visits that do not result in hospitalization should be evaluated for one of the 
other seriousness outcomes to determine whether they qualify as SAEs.
Preplanned hospitalizations (e.g., elective procedures for preexisting conditions that did not 
worsen) are excluded from SAE reporting.
Note that death is an outcome of an AE and not an AE in itself. The event that was the 
proximate cause of death should be reported as the AE term.
8.3.3
Classification of an Adverse Event
Severity of Event
The investigator will provide an assessment of the severity of each AE by recording a severity 
rating on the appropriate AE reporting page of the subject’s CRF. Severity, which is a 
description of the intensity of manifestation of the AE, is distinct from seriousness, which 
implies a subject outcome or AE-required treatment measure associated with a threat to life or 
functionality. Severity will be assessed according to the following scale:
Mild: A type of AE that is usually transient and may require only minimal treatment or 
therapeutic intervention. The event does not generally interfere with usual activities of daily 
living.
Moderate: A type of AE that is usually alleviated with additional specific therapeutic 
intervention. The event interferes with usual activities of daily living, causing discomfort but 
poses no significant or permanent risk of harm to the research subject.
Severe: A type of AE that interrupts usual activities of daily living, or significantly affects 
clinical status, or may require intensive therapeutic intervention.
Relationship to Study Intervention
All adverse events (AEs) must have their relationship to study intervention assessed by the 
investigator who examines and evaluates the participant based on temporal relationship and 

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his/her clinical judgment. The degree of certainty about causality will be graded using the 
categories below. In a clinical trial, the study product must always be suspect. 
•
Related – The AE is known to occur with the study intervention, there is a reasonable 
possibility that the study intervention caused the AE, or there is a temporal 
relationship between the study intervention and event. Reasonable possibility means 
that there is evidence to suggest a causal relationship between the study intervention 
and the AE.
•
Not Related – There is not a reasonable possibility that the administration of the 
study intervention caused the event, there is no temporal relationship between the 
study intervention and event onset, or an alternate etiology has been established.
The PI may change the causality assessment at any time based on new accumulated 
information.
8.4.4 Expectedness 
The investigator will be responsible for determining whether an adverse event (AE) is expected 
or unexpected.  An AE will be considered unexpected if the nature, severity, or frequency of 
the event is not consistent with the risk information previously described in the Investigator’s 
Brochure for the study intervention. If an AE is considered unexpected, the sponsor will 
evaluate the available information and decide whether there is a reasonable possibility that the 
drug caused the adverse event and, therefore, that the event meets the definition of a suspected 
adverse reaction. The suspected adverse reaction will then be reported expeditiously in an IND 
safety report if it also meets the definitions of serious and unexpected (21 CFR 312.32(c)(1)(i)).
8.3.5
Time Period and Frequency for Event Assessment and Follow-Up
The occurrence of an adverse event (AE) or serious adverse event (SAE) may come to the 
attention of study personnel during study visits and interviews of a study participant presenting 
for medical care, or upon review by a study monitor.
All AEs including local and systemic reactions not meeting the criteria for SAEs will be 
captured on the appropriate case report form (CRF). Information to be collected includes event 
description, time of onset, clinician’s assessment of severity, relationship to study product 
(assessed only by those with the training and authority to make a diagnosis), and time of 
resolution/stabilization of the event. All AEs occurring while on study must be documented 
appropriately regardless of relationship. All AEs will be followed to adequate resolution.
Any medical condition that is present at the time that the participant is screened will be 
considered as baseline and not reported as an AE. However, if the study participant’s condition 
deteriorates at any time during the study, it will be recorded as an AE. 
Changes in the severity of an AE will be documented to allow an assessment of the duration 
of the event at each level of severity to be performed. AEs characterized as intermittent require 
documentation of onset and duration of each episode.
Investigators will record all reportable events with start dates occurring any time after informed 
consent is obtained until 30 ± 7 days after the last dose of encaleret.  
Participants are to be queried regarding any AEs or SAEs at the time of each vital sign 
assessment, as well as at each visit, according to the Schedule of Activities (Section 1.3). 

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Participants will be asked to volunteer information with a nonleading question such as, “How 
do you feel?” Study center personnel will then record all pertinent information in the subject’s 
CRF.
All AEs and SAEs reported by the subject (or subject representative) or observed or otherwise 
identified by the investigator (or other study center personnel) at a defined study visit or during 
any communication with the subject (or subject representative) occurring outside a defined 
study visit (from the time the subject signs the ICF to 30 ± 7 days after the last dose of encaleret 
must be documented. Any spontaneously reported SAE identified beyond 30 ± 7 days after the 
last dose of encaleret that is assessed as related to study treatment will be documented.
Events will be followed for outcome information until resolution or stabilization.
8.3.6
Adverse Event Reporting 
Any untoward event that is reported from the time that the subject signs the ICF until study 
completion must be collected. Thus, any untoward medical occurrences or unfavorable and 
unintended signs, symptoms, or diseases that occur in the pretreatment, treatment, or 
posttreatment period are to be considered AEs (and SAEs if appropriate), and consequently 
recorded and reported as such.
Participants are to be queried regarding any AEs or SAEs at the time of each vital sign 
assessment, as well as at each visit, according to the Schedule of Activities (Section 1.3). 
Participants will be asked to volunteer information with a nonleading question such as, “How 
do you feel?” Study center personnel will then record all pertinent information in the subject’s 
CRF.
All AEs and SAEs reported by the subject or guardian or observed or otherwise identified by 
the investigator (or other study center personnel) at a defined study visit or during any 
communication with the subject (or subject’s legal representative) occurring outside a defined 
study visit (from the time the subject signs the ICF to study completion) must be documented.
All AEs must be recorded on the appropriate AE reporting page of the subject’s CRF whether 
or not they are considered causally related to encaleret.
For every AE, the investigator must:
•
Provide an assessment of the severity, causal relationship to encaleret, and 
seriousness of the event (i.e., whether it is a SAE)
•
Document all actions taken with regard to encaleret
•
Detail any other treatment measures taken for the AE
•
Document resolution of the AE (with or without sequelae); ongoing; or lost to 
follow-up.
Reportable events will be tracked and submitted to the IRB as outlined in Policy 801.
8.3.7
Serious Adverse Event Reporting 
In consultation with the PI, a trained member of the study team will be responsible for 
conducting an evaluation of all adverse events and shall report the results of such evaluation 
to the NIH Institutional Review Board (IRB) as per Policy 801. All SAEs will be reported to 
the DSMC at routine intervals or as indicated by the DSMC. 

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All SAEs, whether or not considered study intervention related, will be reported to the NIDCR 
Office of the Clinical Director within 7 days of investigator awareness. The study sponsor will 
be responsible for notifying the Food and Drug Administration (FDA) of any unexpected fatal 
or life-threatening suspected adverse reaction as soon as possible, but in no case later than 7 
calendar days after the sponsor's initial receipt of the information.  In addition, the sponsor 
must notify FDA and all participating investigators in an Investigational New Drug (IND) 
safety report of potential serious risks, from clinical trials or any other source, as soon as 
possible, but in no case later than 15 calendar days after the sponsor determines that the 
information qualifies for reporting.
All SAEs will also be reported to Calcilytix within 1 business day in order that Calcilytix may 
fulfill cross reporting requirements to the Calcilytix IND and all participating investigators 
under thaIND (21 CFR 312.32(c)(1)).
All serious adverse events (SAEs) will be followed until satisfactory resolution or until the site 
investigator deems the event to be chronic or the participant is stable. 
8.3.8
NIH Intramural IRB Reporting of IND Safety Reports
An IND annual safety report will be provided to the regulatory authorities and IRB. Only IND 
Safety Reports that meet the definition of an unanticipated problem (UP) or is new information 
that might affect the willingness of participants on the NIH study to enroll or remain in the 
study will need to be reported separately to the NIH Intramural IRB.
8.3.9
Events of Special Interest 
Hypocalcemia in PSH
Hypocalcemia is not an expected side-effect of treatment with encaleret, but it is a complication 
of the underlying disease being treated. As such, hypocalcemia may develop whenever the 
underlying disease is inadequately treated and might occur due to either inadequate or missed 
doses of a specific, effective medication. 
The current study involves reducing the dose of current maintenance medications or 
suspending their use entirely (i.e., oral calcium supplements and calcitriol), to facilitate 
evaluation of encaleret and potentially establishing clinical proof-of-principle. Under these 
circumstances there is a risk that participants could experience symptoms of hypocalcemia 
prior to reaching encaleret maximal effect. In order to mitigate this risk, the study design 
emphasizes safety foremost. All changes to oral maintenance medications in conjunction with 
encaleret dosing will be conducted with participants in residence at the Clinical Center, with 
multiple daily measurements of blood calcium and close supervision by health professionals 
with experience caring for individuals with hypoparathyroidism. In addition to these 
precautions, monitoring for and capture of events suggestive of or consistent with 
hypocalcemia will be reviewed as an AE of special interest as described below.
Adverse Events of Hypocalcemia: Symptomatic and Asymptomatic
Adverse events consistent with hypocalcemia will be classified as either symptomatic or 
asymptomatic, and assessed for severity, recognizing that there is a spectrum of clinical 
manifestations. Symptomatic hypocalcemia will be based on identification of new or 
worsening symptoms consistent with hypocalcemia such as numbness/tingling of hands, feet 

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or lips, muscle cramps/spasms/twitching, other weakness or lightheadedness and/or new or 
worsening anxiety, including anger or depression and neurocognitive signs of 
confusion/hallucinations accompanied by laboratory evidence of a drop in cCa. Many patients 
with PSH maintained on conventional therapy may have intermittent mild hypocalcemic 
symptoms on baseline therapy because of the need to balance blood calcium levels while 
minimizing urine calcium. In this case, symptomatic hypocalcemia will only be recorded if the 
symptoms are new or worse than the patient’s baseline.   Relevant symptoms will be 
documented as blood calcium levels are checked to confirm calcium status. A Case Report 
Form (CRF) for symptomatic hypocalcemia as an AE of special interest will capture the details 
of each hypocalcemic event including but not limited to symptoms, concomitant cCa 
concentrations, precipitating factors, treatment, resolution, and action taken regarding study 
medication.
Asymptomatic hypocalcemia will also be captured as an AE of special interest based on 
defining a threshold value for cCa < 7 mg/dL.  Since cCa levels are sampled frequently 
throughout the inpatient period, asymptomatic low cCa results will be identified during routine 
cCa monitoring. 
Clinical Evaluation and Treatment of Hypocalcemia:
Hypocalcemia can range in symptom severity from asymptomatic to life-threatening. 
Appropriate treatment and action regarding study medication and/or other interventions (e.g., 
urgent calcium supplementation) will primarily be based on clinical evaluation of severity and 
acuity. Cases of hypocalcemia in this trial, if they occur, are expected to be manageable with 
supportive treatment. 
Different patients may have different sensitivities to low calcium levels but one advantage of 
conducting this initial proof-of-principle trial at the NIH is that the expert investigators have 
significant experience in managing these patients.  The investigators performing the current 
study have decades of accumulated and institutional experience caring for these patients 
including management of hypocalcemia that is a consequence of the underlying disorder. This 
includes experience managing outpatient regimens of oral calcium and calcitriol to ensure 
patient functioning, well-being, and quality of life, based on outpatient laboratory monitoring 
and assessment of symptoms.
Appropriate evaluations may include serial cCa measures, initial, daily, and follow-up ECG as 
appropriate based on clinical assessment (bradycardia e.g.) and/or if cCa is persistently < 7 
mg/dL. 
Graded interventions according to the expert judgment of the NIH investigators will include 
standard measures such as oral calcium and/or calcitriol supplementation (see Table D) for 
mild-moderate events. In the case of unresolving or worsening hypocalcemia with more acute 
clinical manifestations including worsening neurocognitive deficits, seizures, tetany, 
hypotension, or cardiac dysfunction, for example, appropriate urgent intervention, also 
according with standards of care, will be undertaken by the site, including administration of 
intravenous calcium gluconate (See Table D).
Osteosarcoma as an Adverse Event of Special Interest: 
The risk to participants in this study for developing osteosarcoma is very low. However, 
because a carcinogenicity study suggested high-dose, long-term encaleret increased the risk of 

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osteosarcoma in rats with intact parathyroid glands, we will also record any development of 
osteosarcoma in our participants as an adverse event of special interest.
8.3.10 Reporting of Pregnancy 
Pregnancies in participants or partners at any time during the study will be reported. Study 
personnel must report every pregnancy from the time subject signs the ICF until 90 ± 7 days 
after the last dose of encaleret. Pregnancies in participants or partners will be reported to the 
NIDCR Office of the Clinical Director and Calcilytix within 7 days of investigator awareness.  
The study team will make every effort to follow the pregnancy to its conclusion and report the 
outcome on the follow-up Clinical Trial Pregnancy Form. If the pregnancy is associated with 
an SAE (e.g., if the female subject is hospitalized for hemorrhage), a separate SAE Form must 
be completed (in addition to the Pregnancy Form), with the appropriate serious criterion (e.g., 
hospitalization) indicated. The subject may also be asked to enroll on a research study to enable 
the collection of pregnancy related outcome data (for example, the NIH Intramural Research 
Program’s Pregnancy Registry and/or an amended version of this protocol). 
If a subject becomes pregnant, administration of the study drug(s) must be discontinued 
immediately.
If the partner of a male subject becomes pregnant after initiation of encaleret and within 90 ± 7 
days of the last dose, the study team will inform the Sponsor, Calcilytix, and the medical 
monitor. If the pregnant partner agrees to be contacted, she may be asked to enroll on a research 
study to enable the collection of pregnancy related outcome data (for example, the NIH 
Intramural Research Program’s Pregnancy Registry and/or an amended version of this 
protocol) with the intention of following the pregnancy to its conclusion and reporting the 
outcome on the follow-up Clinical Trial Pregnancy Form. 
8.4
Unanticipated Problems
8.4.1
Definition of Unanticipated Problems (UP)
Any incident, experience, or outcome that meets all of the following criteria:
•
Unexpected in terms of nature, severity, or frequency given (a) the research 
procedures that are described in the protocol-related documents, such as the 
Institutional Review Board (IRB)-approved research protocol and informed consent 
document; and (b) the characteristics of the participant population being studied; and
•
Related or possibly related to participation in the research (“possibly related” means 
there is a reasonable possibility that the incident, experience, or outcome may have 
been caused by the procedures involved in the research); and
•
Suggests that the research places participants or others (which many include research 
staff, family members or other individuals not directly participating in the research) at 
a greater risk of harm (including physical, psychological, economic, or social harm) 
than was previously known or expected.
8.4.2
 Unanticipated Problem Reporting 

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The investigator will report unanticipated problems (UPs) to the NIH Institutional Review 
Board (IRB) as per Policy 801.
9
STATISTICAL CONSIDERATIONS
9.1
Statistical Hypothesis
Encaleret in PSH will decrease the fractional excretion of calcium comparing baseline (Day -
1) to the last 24-hour period a patient was taking encaleret 162 mg BID. FECa will be 
calculated using 24-hour urine and 4-hour post-prandial blood levels.  
9.2
Sample Size Determination
The proposed clinical trial is primarily exploratory and preliminary data is limited. The primary 
study endpoint is the percent decrease in FECa using the entire Treatment Population (all 
participants who received at least one dose of study drug). Participants withdrawing for any 
reason any time after receiving their first dose of the study drug will remain in the Treatment 
Population, and the final FECa used will be the last fasting timepoint during which the patient 
was taking encaleret 162 mg BID. 
Power calculations were based on the prior experience with encaleret in ADH1. In the ADH1 
cohort, during a 5-day dosage escalation study (period 1), when 6 subjects were on the maximal 
dose of 162 mg BID for 3 days, the Mean (Standard deviation) of the Day 6 change in fasting 
FECa from baseline was -66 (20) % (unpublished data). Using a two-tailed 0.05 level paired t-
test, we found that 15 participants yielded 80% power to detect a percent change of 16%; 10 
participants yielded 80% power to detect a percent change of 20% and 5 participants yielded 
80% to detect a percent change of 34%. Given the mean reduction in FECa was 66% in the 
ADH1 cohort (and the kidneys of participants with PSH might be expected to respond even 
more robustly to encaleret), we anticipate even a sample size of 5 would be sufficient to 
confirm the proof-of-principle effect on FECa. 
Nevertheless, we plan to enroll up to 15 participants in this study in order to increase the 
likelihood that we include participants with a range of residual parathyroid tissue and to include 
participants with recent hypoparathyroidism. This will allow for sub-group analysis (see 
Section 9.3), which will be exploratory and hypothesis generating. 
Of note, we plan to enroll only 5 participants with recent PSH (Cohort 2), because we anticipate 
some challenges in enrolling this population. More than 5 participants may be impractical to 
enroll in a reasonable amount of time. 
9.3
Populations for Analyses
•
Treatment Population: All participants who received at least one dose of study drug
•
Permanent hypoparathyroidism (Cohort 1): Participants with long-standing 
hypoparathyroidism who received at least one dose of study drug
•
Recent Hypoparathyroid population (Cohort 2): Participants with recent 
hypoparathyroidism who received at least one dose of study drug
•
“PTH-Clamp” Population: Participants whose iPTH did not increase more than 10 
pg/mL on encaleret

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•
“Aparathyroid” Population: Participants whose absolute iPTH level was less than 
10 pg/dL throughout the study
•
Hyperthyroid Population: Participants whose TSH is less than the lower limit of 
normal for the assay during the treatment phase of the study
•
Normothyroid Population: Participants whose TSH is in the normal range during the 
treatment phase of the study
•
Thyroid Cancer Population: Participants with a history of thyroid cancer
9.3.1
Evaluable for toxicity 
All participants will be evaluable for toxicity from the time of their first treatment with 
encaleret.
9.3.2
Evaluable for objective response 
Not applicable. 
9.3.3
Evaluable Non-Target Disease Response
Not applicable.
9.4
Statistical Analyses
9.4.1
General Approach
Categorical variables will be summarized by counts and percentages. Continuous variables 
will be summarized with descriptive statistics (n, mean, standard deviation, median, inter-
quartile range etc.).  All analyses will be performed using SAS 9.4 (the SAS Institute, Cary 
NC). 
9.4.2
Analysis of the Primary Endpoints
The primary endpoint is the percent change in FECa from baseline to the last day on encaleret 
162 mg BID. If a subject stops encaleret early or decreases the dose, the FECa will be 
calculated using the last fasting labs when the patient was on encaleret 162 mg BID. For this 
primary endpoint, if the normality assumption holds, one-sample t-test will be used to analyze 
the data. Otherwise, the nonparametric alternative, the Wilcoxon signed-rank test will be used. 
The primary endpoint analysis will be conducted in the Treatment Population. 
9.4.3
Analysis of the Secondary Endpoint(s)
To analyze the proportion of participants who achieve a concomitant normal or elevated fasting 
blood calcium (albumin-corrected calcium >8.5 mg/dL) and a normal 24-hour urinary calcium 
level on encaleret (<250 mg/24 hours for women, <300 mg/24 hours for men) at any point 
between day 1 and day 5, the proportion along with its 95% confidence interval will be 
calculated using the exact binomial distribution. 
9.4.4
Safety Analyses
Adverse events will be coded as per the Common Terminology Criteria for Adverse Events 
(CTCAE) Version 5.0 and each AE will be counted once only for a given participant. The 

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severity, frequency, and relationship of AEs to study intervention will be presented by System 
Organ Class (SOC) and preferred term groupings. Each AE reported will include start date, 
stop date, severity, relationship, expectedness, outcome, and duration. Adverse events leading 
to premature discontinuation from the study intervention and serious treatment-emergent AEs 
will be presented in a separate table. 
9.4.5
Baseline Descriptive Statistics
Descriptive statistics will be provided to summarize the characteristics of the participants at 
baseline.
9.4.6
Planned Interim Analyses
There is no planned interim analysis for this study. 
9.4.7
Sub-Group Analyses
Due to small sample size and because this is a proof-of-principle study, primary and secondary 
endpoints will not be analyzed based on age, sex, race/ethnicity, or other demographic 
characteristics. Primary and secondary endpoints will be analyzed in each of the analysis 
populations listed in Section 9.3.  
9.4.8
Tabulation of individual Participant Data
Individual participant data may be presented descriptively or graphically over time.
9.4.9
Exploratory Analyses
The pharmacodynamics variables will be analyzed in different analysis populations. 
Potentially linear mixed effects models may be used to analyze the repeated measures data if 
assumptions warrant. 
10 REGULATORY AND OPERATIONAL CONSIDERATIONS
10.1 Informed Consent Process
10.1.1 Consent Procedures and Documentation
Standard Consent Procedures: The informed consent document will be provided as a physical 
or electronic document to the subject or consent designee(s) as applicable for review prior to 
consenting. A designated study investigator will carefully explain, either in-person or remotely 
(e.g., via telephone or other NIH approved remote platforms used in compliance with policy, 
including HRPP Policy 303) the procedures and tests involved in this study, and the associated 
risks, discomforts, and benefits. In order to minimize potential coercion, as much time as is 
needed to review the document will be given, including an opportunity to discuss it with 
friends, family members and/or other advisors, and to ask questions of any designated study 
investigator. A signed informed consent document will be obtained prior to entry onto the 
study.
The initial consent process as well as re-consent, when required, may take place in person or 
remotely (e.g., via telephone or other NIH approved remote platforms used in compliance with 
policy, including HRPP Policy 303) per discretion of the designated study investigator and 
with the agreement of the subject/consent designee(s). Whether in person or remote, the 
privacy of the subject will be maintained. When in person, consenting investigators and 
subject/consent designee, will be located in a private area (e.g., clinic consult room or private 

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inpatient room). When consent is conducted remotely, the subject/consent designee will be 
informed of the private nature of the discussion and will be encouraged to relocate to a more 
private setting if needed.  If consent is obtained remotely, participants and investigators will 
view individual copies of the approved consent document at their respective locations. 
For electronic consent: The study team will confirm with the participant that they are 
comfortable using the electronic consenting before proceeding with obtaining consent. If not, 
other methods will be utilized. When an electronic document with a digital signature is used 
for the documentation of consent, this study will use the iMedConsent™ platform which is 21 
CFR, Part 11 compliant to obtain the required signatures. During the consent process, 
participants/LARs and investigators will view the same approved consent document 
simultaneously in their respective locations. The identity of the participant will be determined 
by verifying a government issued identification card via the telehealth platform, prior to 
obtaining the signature. iMedConsent will capture electronic signatures via the methods listed 
below:
• Using a smartphone: participants will be registering their signatures using their finger.  
Participants will receive a secure link that leads them to secure “web pages” that will capture 
their electronic signatures using their finger.
• Using a computer/tablet/laptop: participants will be registering their signatures using a 
computer mouse or their finger/stylus (for touch/stylus enabled tablets and computer screens).
Participants will receive a secure link that leads them to secure “web pages” that will capture 
their electronic signatures using the aforementioned methods. Once the completed consent has 
been saved, it will post to CRIS within a few minutes. All consents completed in 
iMedConsent™ will post to both the Documents tab and the Consents tab in CRIS. If the 
research participant has a FollowMyHealth™ account a copy of the completed consent will be 
posted to their account within two business days. The study team will provide the research 
participant with a printed copy of the signed document.
10.1.2 Consent for minors when they reach the age of majority 
Not applicable.
10.1.3 Considerations for Consent of NIH staff, or family members of study team 
members
Consent for NIH staff will be obtained as detailed above with following additional protections:
Consent from staff members will be obtained by an individual independent of the staff 
member’s team whenever possible.  Otherwise, the consent procedure will be independently 
monitored by the CC Department of Bioethics Consultation Service in order to minimize the 
risk of undue pressure on the staff member.
10.1.4 Consent of Participants who are, or become, decisionally impaired
Adults unable to provide consent are excluded from enrolling in the protocol. However, it is 
possible that participants enrolled in the protocol may permanently lose the capacity to consent 
for themselves during the course of this study.  In the event this occurs, the participants will be 
withdrawn from the study. 

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10.2 Study Discontinuation and Closure
This study may be temporarily suspended or prematurely terminated if there is sufficient 
reasonable cause.  Written notification, documenting the reason for study suspension or 
termination, will be provided by the suspending or terminating party to study participants, 
investigator, funding agency, the Investigational New Drug (IND) sponsor and regulatory 
authorities.  If the study is prematurely terminated or suspended, the Principal Investigator (PI) 
will promptly inform study participants, the Institutional Review Board (IRB), and sponsor 
and will provide the reason(s) for the termination or suspension.  Study participants will be 
contacted, as applicable, and be informed of changes to study visit schedule and encaleret 
discontinuation procedures.
If a participant experiences severely symptomatic hypocalcemia (e.g., seizures, QTcF > 500 
ms, IV calcium requirement) during the study, or severely symptomatic hypercalcemia (e.g., 
lethargy/stupor), recruitment will be paused and the DSMC will be consulted. At that time the 
DSMC will review the data to determine whether there is sufficient cause to terminate the 
study. The investigators may additionally propose amendments to the protocol to prevent 
recurrence of the event. 
If three participants experience a Grade 3 or greater adverse event that is related to study 
treatment, recruitment will be paused and the DSMC will be consulted. At that time the DSMC 
will review the data to determine whether there is sufficient cause to terminate the study.
Additional circumstances that may warrant termination or suspension include, but are not 
limited to:
•
Determination of unexpected, significant, or unacceptable risk to participants
•
Demonstration of efficacy that would warrant stopping   
•
Insufficient compliance to protocol requirements
•
Data that are not sufficiently complete and/or evaluable
•
Determination that the primary endpoint has been met
•
Determination of futility
Study may resume once concerns about safety, protocol compliance, and data quality are 
addressed, and satisfy the sponsor, IRB and the Food and Drug Administration (FDA).
10.3 Confidentiality and Privacy
Participant confidentiality and privacy is strictly held in trust by the participating investigators, 
their staff, and the sponsor(s). This confidentiality is extended to cover testing of biological 
samples and genetic tests in addition to the clinical information relating to participants. 
Therefore, the study protocol, documentation, data, and all other information generated will be 
held in strict confidence. No information concerning the study or the data will be released to 
any unauthorized third party without prior written approval of the sponsor. 
All research activities will be conducted in as private a setting as possible.
The study monitor, other authorized representatives of the sponsor, representatives of the 
Institutional Review Board (IRB), and/or regulatory agencies may inspect all documents and 
records required to be maintained by the investigator, including but not limited to, medical 

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records (office, clinic, or hospital) and pharmacy records for the participants in this study. The 
clinical study site will permit access to such records.
All participants’ records will only be identified by subject number. The investigator will keep 
a master subject list on which the subject number and the full name, address, and telephone 
number of each subject are listed. The subject’s contact information will be securely stored at 
NIH Clinical Center for internal use during the study. At the end of the study, all records will 
continue to be kept in a secure location for as long a period as dictated by the reviewing IRB, 
Institutional policies, or the Sponsor requirements.
Data collection will involve the use of a 21 CFR part 11 compliant EDC system, only 
authorized personnel will have access to the EDC system. All data collected in the context of 
this study will be stored in a secure location and evaluated according to regulatory 
requirements and applicable guidance for electronic records. Data will be stored and evaluated 
in such a way as to guarantee subject confidentiality in accordance with the legal stipulations 
applying to confidentiality of data. Study records (e.g., copies of CRFs, regulatory documents) 
will be retained at the NIH Clinical Center, along with adequate source documentation, 
according to local regulatory requirements and ICH requirements. 
The investigator must retain a copy of all records that support CRFs for this study (e.g., ICFs, 
clinical laboratory reports, source documents, drug dispensing records) for a period of at least 
15 years after study completion unless local regulations or NIH Clinical Center policies require 
a longer retention period.
If the investigator retires, relocates, or for other reasons withdraws from the responsibility of 
keeping the study records, custody must be transferred to a suitable alternate custodian 
employee of the study center or to a suitably qualified and responsible third party.
To further protect the privacy of study participants, a Certificate of Confidentiality has been 
issued by the National Institutes of Health (NIH).  This certificate protects identifiable research 
information from forced disclosure. It allows the investigator and others who have access to 
research records to refuse to disclose identifying information on research participation in any 
civil, criminal, administrative, legislative, or other proceeding, whether at the federal, state, or 
local level. By protecting researchers and institutions from being compelled to disclose 
information that would identify research participants, Certificates of Confidentiality help 
achieve the research objectives and promote participation in studies by helping assure 
confidentiality and privacy to participants.
10.4 Future use of Stored Specimens and Data
A unique subject code will be used on the CRFs, and in the study database. A subject code log 
that links the names to identification numbers will be securely maintained at the NIH.
Data collected for this study will be analyzed and transmitted to Calcilytix via a secure, 
encrypted Internet connection and stored on a secure server. 
All stored samples are coded and do not have personal identifiers. The codes for identifiers are 
contained in a subject code log that is maintained in secure research files at the NIH. Additional 
research samples collected for FGF23 and mid-molecule PTH may be stored at the NIH for 
use in future studies, with the participants’ consent.

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With the participant’s approval and as approved by local Institutional Review Boards (IRBs), 
de-identified biological samples will be stored at the NIH. These samples could be used to 
research the causes of PSH, its complications and other conditions for which individuals with 
PSH are at increased risk, and to improve treatment. 
During the conduct of the study, an individual participant can choose to withdraw consent to 
have biological specimens stored for future research. However, withdrawal of consent with 
regard to biological sample storage may not be possible after the study is completed. If 
participants are concurrently enrolled another NIH study (for example, the natural history 
protocol 01-D-0184), samples and data collected from this study may be transferred to the 
other study if the participant has consented for future use of their samples/data in both 
protocols.
10.5 Safety Oversight
The PI will be responsible for monitoring the data and accruing safety information. Serious 
adverse event (SAE) monitoring will be supported by an independent medical monitor in 
collaboration with the Office of Clinical Director and the Office of Clinical Trial Operations 
and Management (OCTOM), NIDCR.
The investigator will be responsible for monitoring the data and accruing safety information. 
The investigator is responsible for monitoring the study progress and study data. The 
investigator will also maintain responsibility for ensuring the accuracy, completeness, 
timeliness, and legibility of the data. The investigator and associate investigators are also 
required to keep accurate and timely records to ensure that the conduct of the study is fully 
documented. The investigator will review individual study participant data upon each patient 
encounter. Trends will be discussed to ensure subject safety, study compliance, and recruitment 
goals are met.
This study will be monitored by the NIDCR Division of Intramural Research Data and Safety 
Monitoring Committee (DSMC). Assessment and recommendations by the DSMC in relation 
to the study will be made to the NIDCR Clinical Director. The DSMC will include members 
with expertise in a broad range of areas, including human participants’ protection, research 
ethics, clinical trial implementation, and medical bone and mineral metabolism. The PI and 
NIDCR OCD will receive assessments and recommendations from the DSMC following 
interval meetings. These assessments and recommendations will be submitted to the IRB at the 
time of Continuing Review, or as needed if safety concerns arise. 
An independent study monitor on contract with NIDCR OCD DIR, NIH will review data and 
safety parameter of the study. Independent study monitors are qualified by training and 
experience to monitor the progress and safety of clinical trials. Personnel monitoring this study 
will not be affiliated in any way with the trial conduct. The PI and NIDCR OCD will receive 
reports from the independent study monitor following interim monitoring visits. The results 
will be summarized for the DSMC at interval meetings and for the IRB at Continuing Review, 
or as needed if safety concerns arise.
10.6 Clinical Monitoring
Before the first subject is dosed in the study, designees from the Office of Clinical Director 
and the Office of Clinical Trial Operations and Management (OCTOM) will meet with the 
investigator and the investigator’s staff to review the procedures for conducting the study. The 

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independent study monitor will routinely monitor the progress of the study by conducting on-
site or virtual/remote visits thereafter. The monitor will also be able to review query statuses 
remotely, which may warrant more frequent communication with the NIH investigator and 
study staff. The investigator will make available to the study monitor the source documents, 
the signed consent forms, and all other study-related documents. The investigator will be 
responsible for reviewing eCRFs, resolving data queries generated by the study monitor via 
the system, providing missing or corrected data, approving all changes performed on the data, 
and endorsing the participants data within the EDC system.
Additional details of the process and procedures for clinical study research site monitoring will 
be documented in the Clinical Monitoring Plan (CMP).
10.7 Quality Assurance and Quality Control
Following written Standard Operating Procedures (SOPs), the clinical trial monitors will verify 
that the clinical trial is conducted, data are generated, biological specimens are collected, 
documented (recorded), and reported in compliance with the protocol, International Council 
for Harmonisation Good Clinical Practice (ICH GCP), and applicable regulatory requirements 
(e.g., Good Laboratory Practices (GLP), Good Manufacturing Practices (GMP)). Additional 
details of monitoring (including Clinical, Safety, Data, Quality, and overall Trial monitoring) 
will be available in designated monitoring plan documents.
Quality control (QC) procedures will be implemented beginning with the data entry system 
and data QC checks that will be run on the database will be generated. Any missing data or 
data anomalies will be communicated to the site(s) for clarification/resolution.
10.8 Data Handling and Record Keeping
10.8.1 Data Collection and Management Responsibilities
Data collection is the responsibility of the clinical trial staff at the site under the supervision of 
the site investigator. The investigator is responsible for ensuring the accuracy, completeness, 
legibility, and timeliness of the data reported.
All source documents should be completed in a neat, legible manner to ensure accurate 
interpretation of data.
Hardcopies or electronic copies of the study visit and outpatient lab results will be provided 
for use as source document worksheets for recording data for each subject enrolled in the study. 
Data recorded in the electronic case report form (eCRF), derived from source documents, 
should be consistent with the data recorded on the source documents.
Clinical data (including adverse events (AEs), concomitant medications, and expected adverse 
reactions data) and clinical laboratory data will be entered into CTDB, an electronic data 
capture system that is 21 CFR Part 11-compliant developed by NICHD for data collection, 
query management, and data analysis for NIH clinical studies. The data system includes 
password protection and internal quality checks, such as automatic range checks, to identify 
data that appear inconsistent, incomplete, or inaccurate. Clinical data will be entered into the 
electronic data capture system directly from the source documents.
10.8.2 Study Records Retention

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Study documents should be retained for a minimum of 2 years after the last approval of a 
marketing application in an International Council for Harmonisation (ICH) region and until 
there are no pending or contemplated marketing applications in an ICH region or until at least 
2 years have elapsed since the formal discontinuation of clinical development of the study 
intervention, and as per the NIH Intramural Records Retention Schedule. 
10.9 Protocol Deviations and Non-Compliance
It is the responsibility of the investigator to use continuous vigilance to identify and report 
deviations and/or non-compliance to the NIH Institutional Review Board as per Policy 801.  
All deviations must be addressed in study source documents.  The investigator is responsible 
for knowing and adhering to the reviewing IRB requirements.
10.9.1 NIH Definition of Protocol Deviation
A protocol deviation is any changed, divergence, or departure from the IRB-approved research 
protocol. 
•
Major deviations: Deviations from the IRB approved protocol that have, or may have 
the potential to, negatively impact the rights, welfare or safety of the subject, or to 
substantially negatively impact the scientific integrity or validity of the study.
•
Minor deviations: Deviations that do not have the potential to negatively impact the 
rights, safety or welfare of participants or others, or the scientific integrity or validity 
of the study.
10.10 Publication and Data Sharing Policy
10.10.1Human Data Sharing Plan
This study will be conducted in accordance with the following publication and data sharing 
policies and regulations:
National Institutes of Health (NIH) Public Access Policy, which ensures that the public has 
access to the published results of NIH funded research. It requires scientists to submit final 
peer-reviewed journal manuscripts that arise from NIH funds to the digital archive PubMed 
Central upon acceptance for publication.
This study will comply with the NIH Data Sharing Policy and Policy on the Dissemination of 
NIH-Funded Clinical Trial Information and the Clinical Trials Registration and Results 
Information Submission rule. As such, this trial will be registered at ClinicalTrials.gov, and 
results information from this trial will be submitted to ClinicalTrials.gov. In addition, every 
attempt will be made to publish results in peer-reviewed journals. Investigators will consider 
requests from qualified researchers for access to anonymized clinical data.
Results from this study may also be shared at scientific conferences.
10.10.2Genomic Data Sharing Compliance
Not applicable.
10.11 Collaborative Agreements 
10.11.1Agreement Type

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A Materials Cooperative Research and Development Agreement (MCRADA), between 
NIDCR and Calcilytix Therapeutics, Inc., the pharmaceutical company that produces Encaleret 
will be established. Calcilytix Therapeutics, Inc. will provide Encaleret for this study. They 
will also provide financial support for the protocol as detailed in the MCRADA. Calcilytix 
Therapeutics, Inc. is permitted to review manuscript(s) prior to publication.
10.12 Conflict of Interest Policy
The independence of this study from any actual or perceived influence, such as by the 
pharmaceutical industry, is critical.  Therefore, any actual conflict of interest of persons who 
have a role in the design, conduct, analysis, publication, or any aspect of this trial will be 
disclosed and managed. Furthermore, persons who have a perceived conflict of interest will be 
required to have such conflicts managed in a way that is appropriate to their participation in 
the design and conduct of this trial.  The study leadership in conjunction with the NIDCR has 
established policies and procedures for all study group members to disclose all conflicts of 
interest and will establish a mechanism for the management of all reported dualities of interest.
11 ABBREVIATIONS
ADH1
Autosomal dominant hypocalcemia type 1 (ADH1)
AE
Adverse Event
Alb
Albumin
ALT
Alanine aminotransferase
AST
Aspartate aminotransferase
AUC
Area under the curve
AUC(0-24)
Area under the concentration-time curve from time 0 to 24 hours
BID
Twice daily
BMI
Body mass index
CaSR
Calcium-sensing receptor
cCa
Albumin-corrected blood calcium
CFR
Code of Federal Regulations
CLIA
Clinical Laboratory Improvement Amendments
Cmax
Maximum plasma concentration
CMP
Clinical Monitoring Plan
CONSORT
Consolidated Standards of Reporting Trials
Cr
Creatinine
CRF
Case Report Form
CTx
Collagen cross-linked C-telopeptide
DCC
Data Coordinating Center
DSMC   
Data and Safety Monitoring Committee
ECG
Electrocardiogram
eCRF
Electronic Case Report Forms
eGFR
Estimated glomerular filtration rate
ET
Early termination
EoT
End of Treatment 
FDA
Food and Drug Administration

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FGF23
Fibroblast growth factor-23
FSH
Follicle stimulating hormone
FU
Follow-up
GCP
Good Clinical Practice
GLP
Good Laboratory Practices
GMP
Good Manufacturing Practices
HBsAg
Hepatitis B surface antigen
HIV
Human immunodeficiency virus
IB
Investigator’s Brochure
ICF
Informed consent form
ICH
International Council for Harmonisation 
IgM
Immunoglobulin M
IMP
Investigational medicinal product (encaleret)
iPTH
Intact PTH
IRB
Institutional Review Board
IRB
Institutional Review Board
M1
Metabolite of encaleret, ether glucuronide of the parent drug
M3
Metabolite of encaleret, acyl glucuronide of the parent drug
MedDRA
Medical Dictionary for Regulatory Activities
NIH 
National Institutes of Health
P1NP
Procollagen type 1 N-pro-peptide
PD
Pharmacodynamic
PI
Principal Investigator
PK
Pharmacokinetic
PTH
Parathyroid hormone
QC
Quality Control
QD
Once daily
QTc
QT interval corrected for changes in the heart rate
SAE
Serious Adverse Event
SMC
Safety Monitoring Committee
SOA
Schedule of Activities
SOC
Standard of Care
SOP
Standard Operating Procedure
TEAE
Treatment-emergent adverse event
tmax
Time to maximum plasma concentration
UP
Unanticipated Problem
WOCBP
Women of childbearing potential
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