Randomized Double-blind Placebo-controlled Trial Assessing the Efficacy of Standard and Low Dose Hydrochlorothiazide Treatment in the Prevention of Recurrent Nephrolithiasis
Phase: PHASE3
Conditions: Nephrolithiasis
Sponsor: Insel Gruppe AG, University Hospital Bern

Hydrochlorothiazide for Kidney Stone Recurrence Prevention 
(NOSTONE trial; NCT03057431)
Study Protocol (last version 28. November 2019)
Statistical Analysis Plan (last version 11. November 2021)
For details see next page.

I.
Study protocols
1.
First/original trial protocol (version 1.0; Aug 30th, 2016)
2.
Last/final protocol (version 1.7; Nov 28th, 2019)
3.
Revision history
II.
Statistical Analysis Plans (SAP)
1.
First/original SAP (version 1.0; Nov 6th, 2018)
2.
Last/final SAP (version 4.0; Nov 11th, 2021)
3.
Revision history
Note: The protocol version control employed a two-level system (#.#) whereas the version control of the 
Statistical Analysis Plan actually only used a one-level system, although versions where formally named with 
two levels. 

 
 
 
 
 
 
 
 
 
First/original trial protocol 
Version 1.0 
August 30th, 2016 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
Page 1 of 46 
 
 
Clinical Study Protocol 
Randomized double-blind placebo-controlled trial assessing the efficacy of 
standard and low dose hydrochlorothiazide treatment 
in the prevention of recurrent nephrolithiasis 
 
NOSTONE TRIAL 
 
 
Study Type: 
Clinical trial with Investigational Medicinal Product (IMP)  
 
Study Categorisation: 
 
Risk category B 
 
Study Registration: 
 
ClinicalTrials.gov, Swiss National Clinical Trials Portal (SNCTP) 
 
Study Identifier: 
Swiss National Science Foundation # 33IC30_166785/ 1 
 
Sponsor-Investigator: 
 
Prof. Dr. med. Daniel Fuster 
Leitender Arzt 
Division of Nephrology, Hypertension and Clinical Pharmacology 
Bern University Hospital, Bern, Switzerland 
Phone: +41 (0)31 632 31 44 
Email: daniel.fuster@insel.ch 
 
Investigational Product: 
 
Hydrochlorothiazide 
 
Protocol Version and Date: 
 
Version 1, 30.08.2016 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CONFIDENTIAL 
The information contained in this document is confidential and the property of the sponsor. The 
information may not - in full or in part - be transmitted, reproduced, published, or disclosed to others 
than the applicable Competent Ethics Committee(s) and Regulatory Authority(ies) without prior written 
authorisation from the sponsor except to the extent necessary to obtain informed consent from those 
who will participate in the study. 
 
 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
Page 3 of 46 
 
 
Local Principal Investigator at study site: 
 
I have read and understood this trial protocol and agree to conduct the trial as set out in this study 
protocol, the current version of the World Medical Association Declaration of Helsinki, ICH-GCP 
guidelines and the local legally applicable requirements. 
 
Site: 
 
Principal Investigator: 
 
 
 
Place/ Date 
 
Signature 
 
 
 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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Table of Contents 
 
STUDY SYNOPSIS .............................................................................................................................. 6 
STUDY SUMMARY IN LOCAL LANGUAGE ....................................................................................... 9 
ABBREVIATIONS .............................................................................................................................. 10 
STUDY SCHEDULE 1 – PARTICIPANTS RECRUITED IN THE FIRST 12 MONTHS OF THE 
RECRUITMENT PERIOD ................................................................................................................... 11 
STUDY SCHEDULE 2 – PARTICIPANTS RECRUITED ≥ 12 MONTHS AFTER RECRUITMENT 
START ................................................................................................................................................ 13 
1. 
STUDY ADMINISTRATIVE STRUCTURE .................................................................................. 15 
1.1 
Sponsor-Investigator .................................................................................................................. 15 
1.2 
Principal Study Investigator ....................................................................................................... 15 
1.3 
Statistician ("Biostatistician") ...................................................................................................... 15 
1.4 
Laboratory ................................................................................................................................. 15 
1.5 
Monitoring institution .................................................................................................................. 15 
1.6 
Data Safety Monitoring Committee ............................................................................................ 15 
1.7 
Any other relevant Committee, Person, Organisation, Institution ............................................... 15 
2. 
ETHICAL AND REGULATORY ASPECTS ................................................................................. 16 
2.1 
Study registration ....................................................................................................................... 16 
2.2 
Categorisation of study .............................................................................................................. 16 
2.3 
Competent Ethics Committee (CEC) ......................................................................................... 16 
2.4 
Competent Authorities (CA) ....................................................................................................... 16 
2.5 
Ethical Conduct of the Study ...................................................................................................... 16 
2.6 
Declaration of interest ................................................................................................................ 16 
2.7 
Patient Information and Informed Consent ................................................................................ 16 
2.8 
Participant privacy and confidentiality ........................................................................................ 17 
2.9 
Early termination of the study .................................................................................................... 17 
2.10 Protocol amendments ................................................................................................................ 17 
3. 
BACKGROUND AND RATIONALE ............................................................................................ 17 
3.1 
Background and Rationale ........................................................................................................ 17 
3.2 
Investigational Product (treatment, device) and Indication ......................................................... 22 
3.3 
Preclinical Evidence ................................................................................................................... 23 
3.4 
Clinical Evidence to Date ........................................................................................................... 23 
3.5 
Dose Rationale: Rationale for the intended purpose in study .................................................... 23 
3.6 
Explanation for choice of comparator (or placebo) ..................................................................... 23 
3.7 
Risks/ Benefits ........................................................................................................................... 24 
3.8 
Justification of choice of study population .................................................................................. 24 
4. 
STUDY OBJECTIVES ................................................................................................................. 24 
4.1 
Overall Objective ....................................................................................................................... 24 
4.2 
Primary Objective ...................................................................................................................... 25 
4.3 
Secondary Objectives ................................................................................................................ 25 
4.4 
Safety Objectives ....................................................................................................................... 25 
5. 
STUDY OUTCOMES ................................................................................................................... 25 
5.1 
Primary Outcome ....................................................................................................................... 25 
5.2 
Secondary Outcomes ................................................................................................................ 25 
5.3 
Other Outcomes of Interest........................................................................................................ 25 
5.4 
Safety Outcomes ....................................................................................................................... 25 
6. 
STUDY DESIGN .......................................................................................................................... 26 
6.1 
General study design and justification of design ........................................................................ 26 
6.2 
Methods of minimizing bias ........................................................................................................ 27 
6.3 
Unblinding Procedures (Code break) ......................................................................................... 27 
7. 
STUDY POPULATION ................................................................................................................ 27 
7.1 
Eligibility criteria ......................................................................................................................... 28 
7.2 
Recruitment and screening ........................................................................................................ 28 
7.3 
Assignment to study groups ....................................................................................................... 29 
7.4 
Criteria for withdrawal/ discontinuation of participants ............................................................... 29 
8. 
STUDY INTERVENTION ............................................................................................................. 30 
8.1 
Identity of Investigational Products ............................................................................................ 30 
8.2 
Administration of experimental and control interventions ........................................................... 30 
8.3 
Dose modifications .................................................................................................................... 30 

 
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8.4 
Compliance with study intervention............................................................................................ 31 
8.5 
Data Collection and Follow-up for withdrawn participants .......................................................... 32 
8.6 
Trial-specific preventive measures ............................................................................................ 32 
8.7 
Concomitant Interventions (treatments) ..................................................................................... 32 
8.8 
Study Drug Accountability .......................................................................................................... 32 
8.9 
Return or Destruction of Study Drug/ Medical Device ................................................................ 32 
9. 
STUDY ASSESSMENTS ............................................................................................................ 33 
9.1 
Study flow chart(s)/ table of study procedures and assessments ............................................... 33 
9.2 
Assessments of outcomes ......................................................................................................... 33 
9.3 
Procedures at each visit ............................................................................................................ 34 
10. SAFETY ...................................................................................................................................... 37 
10.1 Definition and assessment of (serious) adverse events and other safety related events ........... 37 
10.2 Reporting of serious adverse events (SAE) and other safety-related events ............................. 38 
10.3 Follow up of (serious) adverse events ....................................................................................... 39 
11. STATISTICAL METHODS .......................................................................................................... 39 
11.1 Hypothesis ................................................................................................................................. 39 
11.2 Determination of Sample Size ................................................................................................... 39 
11.3 Statistical criteria of termination of trial ...................................................................................... 40 
11.4 Planned Analyses ...................................................................................................................... 40 
11.5 Handling of missing data and drop-outs ..................................................................................... 41 
12. QUALITY ASSURANCE AND CONTROL .................................................................................. 41 
12.1 Data handling and record keeping/ archiving ............................................................................. 41 
12.2 Data management ..................................................................................................................... 41 
12.3 Monitoring .................................................................................................................................. 42 
12.4 Audits and Inspections ............................................................................................................... 42 
12.5 Confidentiality, Data Protection .................................................................................................. 42 
12.6 Storage of biological material and related health data ............................................................... 42 
13. PUBLICATION AND DISSEMINATION POLICY ........................................................................ 42 
14. FUNDING AND SUPPORT ......................................................................................................... 43 
14.1 Funding ..................................................................................................................................... 43 
14.2 Other Support ............................................................................................................................ 43 
15. INSURANCE ............................................................................................................................... 43 
16. REFERENCES ............................................................................................................................ 43 
17. APPENDICES ............................................................................................................................. 46 
 
 
 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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STUDY SYNOPSIS 
 Sponsor/ Sponsor-
Investigator: 
Inselspital Bern (Sponsor) represented by Prof. Dr. med. Daniel Fuster 
(Sponsor-Investigator) 
Study Title: 
Randomized double-blind placebo-controlled trial assessing the efficacy 
of standard and low dose hydrochlorothiazide treatment in the prevention 
of recurrent nephrolithiasis 
Short Title/ Study ID: 
NOSTONE Trial 
Protocol Version and 
Date: 
Version 1, 30.08.2016 
Trial registration: 
ClinicalTrials.gov, Swiss national clinical trials portal (SNCTP) 
Study category and 
Rationale: 
Risk category B 
Clinical trial with an IMP authorized in Switzerland that is not used in 
accordance with its prescribing information.  
Clinical Phase: 
Therapeutic use 
Background and 
Rationale: 
Nephrolithiasis is a global healthcare problem with a current lifetime risk 
of 18.8% in men and 9.4% in women. Without specific treatment, 5- and 
20-year recurrence rates are 40% and 75%, respectively. Given the high 
cost of medical treatments and surgical interventions as well as the 
morbidity related to symptomatic stone disease, medical prophylaxis for 
stone recurrence is an attractive approach.  
About 80–90% of stones are composed of calcium oxalate with various 
admixtures of calcium phosphate. Increased excretion of calcium in the 
urine, hypercalciuria, is the most common metabolic abnormality 
encountered in patients with recurrent nephrolithiasis. Thiazide diuretics 
have been the cornerstone of pharmacologic metaphylaxis for more than 
40 years. The effect of thiazides to reduce the risk of stone recurrence 
has been attributed to their ability to decrease urinary calcium excretion. 
However, other factors, such as reduction of urinary pH and urinary 
oxalate excretion, probably contribute to this effect. Efficacy of thiazides 
on recurrence prevention of calcareous nephrolithiasis was tested in 11 
randomized controlled trials (RCTs). With the exception of two trials, 
thiazides significantly reduced stone recurrence. Most of these trials are 
from the 1980’s and 90’s and the cumulative number of patients studied 
is remarkably low for such a prevalent disease. Our systematic review of 
these RCTs revealed major methodological deficiencies in all trials, 
including: lack of double-blinding and intention-to-treat analysis, unclear 
allocation concealment, lack of adverse event and drop out reporting and 
unknown baseline risk of disease severity. Furthermore, high doses of 
thiazides were employed in all trials, in the case of the best studied 
thiazide, hydrochlorothiazide (HCTZ), up to 100 mg daily. At such high 
doses, side effects occur frequently. Nowadays, thiazides are widely 
used in the treatment of recurrent nephrolithiasis and arterial 
hypertension, but at significantly lower doses. In the case of recurrent 
nephrolithiasis, however, this practice is not supported by randomized 
evidence and consequently, we do not know whether the currently 
employed low dose thiazide regimens are effective in reducing the risk 
for stone recurrence. 
Thus, evidence for benefits and harms of thiazide diuretics in the 
prevention of calcium-containing kidney stones in general remains 
unclear. In addition, the efficacy of the currently employed low dose 
thiazide regimens to prevent stone recurrence is not known. 
Objective(s): 
We plan to assess the efficacy of standard and low dose HCTZ 
treatment in the recurrence prevention of calcium-containing kidney 
stones. More specifically, we aim to assess the dose-response 
relationship for three different dosages of HCTZ. 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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Outcome(s): 
Primary: relationship of the incidence of stone recurrences (a composite 
of symptomatic or radiologic recurrence) during study treatment and 
dose group.  
Secondary: individual components of the composite primary outcome, 
changes in urinary biochemistry elicited by HCTZ treatment and impact 
of baseline disease severity, biochemical abnormalities and stone 
composition on treatment response. 
Study design: 
Multicenter, randomized, placebo-controlled, double-blind, parallel-group 
trial.  
Inclusion/ Exclusion 
criteria: 
Main inclusion criteria:  
 
Informed Consent as documented by signature 
 
Age 18 years or older 
 
Recurrent kidney stone disease (≥ 2 stone events within the last 10 
years prior to randomization) 
 
Any past kidney stone containing 50% or more of calcium oxalate, 
calcium phosphate or a mixture of both 
 
Main exclusion criteria: 
 
Subjects with secondary causes of recurrent calcareous 
nephrolithiasis 
 
Subjects with the following medications: Thiazide or loop diuretics, 
carbonic anhydrase inhibitors, xanthine oxidase inhibitors, alkali, 
active Vitamin D, calcium supplementation, bisphosphonates, 
denusomab, teriparatide, glucocorticoids 
 
Known allergy to the study drug 
Measurements and 
procedures: 
An overview on the study measurements and procedures is provided in 
the study schedules. 
The main measurements and procedures performed are the following:  
Screening: medical history, vital signs, clinical laboratory tests 
Efficacy: symptomatic stone recurrence, low-dose renal-limited 
computed tomography for radiologic stone recurrence. 
Safety: vital signs, complete physical examination, SAEs and selected 
AEs, clinical laboratory tests. 
Study Product/ 
Intervention:  
HCTZ 12.5 mg, 25 mg or 50 mg once daily per os for 24 or 36 months. In 
addition, all patients in HCTZ treatment arms will receive state-of-the-art 
non-pharmacologic recommendations for stone prevention according to 
current guidelines. 
Control Intervention 
(if applicable): 
Placebo once daily per os for 24 to 36 months. In addition, all patients in 
the placebo arm will receive state-of-the-art non-pharmacologic 
recommendations for stone prevention according to current guidelines. 
Number of 
Participants with 
Rationale: 
416 patients in total, 104 patients per study arm. 
Study Duration: 
01/2017 – 02/2021  
Study Schedule: 
Month/Year of First-Participant-In: 01/2017 
Month/Year of Last-Participant-Out: 02/2021 
Investigator(s): 
Principal Study Investigator: 
Prof. Dr. med. Daniel Fuster, Leitender Arzt 
Division of Nephrology, Hypertension and Clinical Pharmacology, Bern 
University Hospital 
Freiburgstrasse 11, 3010 Bern, Switzerland 
Email: daniel.fuster@insel.ch 
Phone: +41 (0)31 632 31 44 
Study Centre(s): 
8 sites in Switzerland including University Hospitals of Basel, Bern, 
Geneva, Lausanne and Zürich as well as Cantonal Hospitals of Aarau, 
Lugano and St. Gallen. 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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Statistical 
Considerations: 
Sample size: Calculation was based on the primary objective i.e. to 
assess the dose-response relationship and the primary outcome i.e. 
recurrence with the following assumptions: 
 
Uniform recruitment over 24 months with allocation ratio fixed at 1 
across all arms. 
 
A maximum and minimum follow-up time of 36 and 24 months, 
respectively. 
 
Cumulative drop-out rate of 10% at 24 months after study start. 
 
Risk of recurrence in the placebo group of 0.20 and 0.45 at 12 and 
36 months after study start, respectively. 
 
Hazard ratios for the 12.5, 25 and 50 mg HCTZ doses of 0.90, 0.65 
and 0.50, respectively.  
 
Power was set to be at least 80% and alpha was fixed at a two-sided 
level of 0.05. 
 
An unweighted log-rank test for linear trend with local alternatives. 
 
Primary efficacy analysis: On the intention-to-treat analysis set by a 
stratified log-rank test for linear trend with the hazard ratio as primary 
effect measure. The test addresses the primary objective of the trial i.e. 
test for any dose-response relationship. Comparisons between placebo 
and the three active trial arms will be considered exploratory as the trial 
is not powered to detect differences there. Missing data will be handled 
by multiple imputation. All statistical analyses will be presented as effect 
measure plus 95% confidence interval. 
Secondary efficacy analysis: Analysis will follow principles as described 
for primary efficacy analysis. Continuous outcomes (laboratory values) 
will be analyzed using linear regression. 
GCP Statement: 
This study will be conducted in compliance with the protocol, the current 
version of the Declaration of Helsinki, the ICH-GCP as well as all 
national legal and regulatory requirements.  
 
 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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STUDY SUMMARY IN LOCAL LANGUAGE  
Titel des Forschungsprojektes: 
Randomisierte plazebokontrollierte Doppelbindstudie über die Wirksamkeit von normal- und 
tiefdosiertem Hydrochlorothiazid zur Vorbeugung von Rückfällen kalziumhaltiger Nierensteine: die 
NOSTONE-Studie 
 
Lead:  
In dieser klinischen Studie wird die Wirksamkeit des Medikaments Hydrochlorothiazid zur Vorbeugung 
von Rückfällen kalziumhaltiger Nierensteine getestet. 
 
Inhalt und Ziele des Forschungsprojektes:  
Nierensteine sind ein weltweites Gesundheitsproblem, etwa 10% aller Menschen sind mindestens 
einmal im Leben davon betroffen. Nierensteine sind äusserst schmerzhaft, treten wiederholt auf und 
verursachen hohe direkte und indirekte Kosten. Eine effektive und kostengünstige Vorbeugung gegen 
Rückfälle von Nierensteinen ist deshalb äusserst wünschenswert.  
Etwa 80-90% aller Nierensteine enthalten Kalzium, eine vermehrte Ausscheidung von Kalzium im Urin 
ist die häufigste Stoffwechselstörung bei Patienten mit Nierensteinen. Thiazide reduzieren die 
Kalziumausscheidung im Urin und werden daher seit Jahrzehnten zur Vorbeugung von Rückfällen 
kalziumhaltiger Nierensteine eingesetzt. Deren Wirksamkeit wurde in den letzten 30 Jahren in 
mehreren Studien getestet. Leider war die Durchführung dieser Studien mangelhaft, die Gesamtzahl 
der untersuchten Patienten klein, und es wurden hohe Medikamentendosen getestet, welche häufig 
Nebenwirkungen verursachen. Zur Zeit ist daher der Stellenwert der Thiazide in der Behandlung von 
Patienten mit Nierensteinen unklar. Ziel dieser Studie ist es, die Wirksamkeit von normal- und 
tiefdosiertem Hydrochlorothiazid zur Vorbeugung von Rückfällen kalziumhaltiger Nierensteine zu 
testen. 
 
Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts:  
Das Nierensteinleiden gehört zu den häufigsten menschlichen Erkrankungen. Mit dieser klinischen 
Studie soll eine grosse Wissenslücke in der Nierensteinbehandlung geschlossen werden. Die 
Resultate dieser Studie werden die Behandlung von Nierensteinpatienten weltweit beeinflussen. 

 
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ABBREVIATIONS 
AE 
Adverse Event  
BMI 
Body Mass Index 
CA 
Competent Authority (Swissmedic) 
CEC 
Competent Ethics Committee 
CI 
Confidence Interval 
CRF 
Case Report Form  
eCRF 
Electronic Case Report Form  
CT 
Computed Tomography 
CTCAE 
Common Terminology Criteria for Adverse Events 
EOS 
End of Study 
EOT 
End of Treament 
GCP 
Good Clinical Practice  
HCTZ 
Hydrochlorothiazide 
IMP 
Investigational Medicinal Product 
IVU 
Intravenous Urography 
NIH 
National Institute of Health 
RCT 
Randomized Controlled Trial 
SAE 
Serious Adverse Event 
SNCTP 
Swiss National Clinical Trials Portal 
SUSAR 
Suspected Unexpected Serious Adverse Reaction  
 
 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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1. STUDY ADMINISTRATIVE STRUCTURE  
1.1 
Sponsor-Investigator 
Prof. Dr. med. Daniel Fuster, Leitender Arzt 
Division of Nephrology, Hypertension and Clinical Pharmacology, Bern University Hospital 
Freiburgstrasse 11, 3010 Bern, Switzerland 
Email: daniel.fuster@insel.ch 
Phone: +41 (0)31 632 31 44 
1.2 
Principal Study Investigator 
Prof. Dr. med. Daniel Fuster, Leitender Arzt 
Division of Nephrology, Hypertension and Clinical Pharmacology, Bern University Hospital 
Freiburgstrasse 11, 3010 Bern, Switzerland 
 
Email: daniel.fuster@insel.ch 
Phone: +41 (0)31 632 31 44 
1.3 
Statistician ("Biostatistician")  
PD Dr. med. Sven Trelle 
CTU Bern, Department of Clinical Research, University of Bern 
Finkelhubelweg 11, 3012 Bern, Switzerland 
Email: sven.trelle@ctu.unibe.ch 
Phone: +41 (0)31 631 35 04 
1.4 
Laboratory 
The address of the central laboratory is documented elsewhere. 
1.5 
Monitoring institution 
CTU Bern, Department of Clinical Research, University of Bern 
Finkelhubelweg 11, 3012 Bern, Switzerland 
Phone: +41 (0)31 631 33 72 
1.6 
Data Safety Monitoring Committee  
Not applicable. 
1.7 
Any other relevant Committee, Person, Organisation, Institution  
1.7.1 
Study Steering Committee 
The study steering committee will be responsible for the overall supervision of the trial and will 
regularly meet to discuss scientific and logistic aspects of the trial. Information on the composition of 
the committee is available in a separate document. 
 
 

 
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2. ETHICAL AND REGULATORY ASPECTS  
Before the study will be conducted, the protocol, the proposed patient information and consent form, 
as well as other study-specific documents shall be submitted to a properly constituted Competent 
Ethics Committee (CEC) and competent authority (CA, Swissmedic) in agreement with local legal 
requirements, for formal approval. Any amendment to the protocol must as well be approved (if legally 
required) by these institutions. 
The decision of the CEC and CA concerning the conduct of the study will be made in writing to the 
Sponsor-Investigator before commencement of this study. The clinical study can only begin once 
approval from all required authorities has been received. Any additional requirements imposed by the 
authorities shall be implemented. 
2.1 
Study registration  
The study will be registered in the Clinical Trials Registry Platform of the National Institute of Health 
(NIH) – ClinicalTrials.gov. In addition, the trial will be registered in the Swiss National Clinical Trials 
Portal (SNCTP). 
2.2 
Categorisation of study  
Risk category B. Clinical trial with an investigational medicinal product (IMP) authorized in Switzerland 
that is not used in accordance with its prescribing information.  
2.3 
Competent Ethics Committee (CEC)  
Responsible investigators at each study site will ensure that approval from the appropriate constituted 
CEC is sought for the clinical study. Yearly intermediary reports (annual safety reports) will be 
forwarded to the CEC. Changes in the research activity and all unanticipated problems involving risks 
to humans will be reported to the CEC within 15 days. No changes will be made to the protocol without 
prior Sponsor and CEC approval, except where necessary to eliminate apparent immediate hazards to 
study participants. 
Premature study end or interruption of the study will be reported to the CEC within 15 days. The 
regular end of the study will be reported to the CEC within 90 days, the final study report shall be 
submitted within one year after study end. Amendments will be reported according to section 2.10. 
2.4 
Competent Authorities (CA)  
The Sponsor-Investigator will obtain approval from the CA (Swissmedic) before the start of the clinical 
trial. Yearly intermediary reports (annual safety reports) will be forwarded to the CA. Premature study 
end or interruption of the study will be reported to the CA within 15 days. The regular end of the study 
will be reported to the CA within 90 days, the final study report shall be submitted within one year after 
study end. Amendments are reported according to section 2.10. Non-substantial amendments shall be 
reported as soon as possible. 
2.5 
Ethical Conduct of the Study  
The study will be carried out in accordance to the protocol and with principles enunciated in the 
current version of the Declaration of Helsinki, the guidelines of Good Clinical Practice (GCP) issued by 
ICH, the Swiss Law and Swiss regulatory authority’s requirements. The CEC and regulatory 
authorities will receive annual safety and interim reports and be informed about study stop/ end in 
agreement with local requirements.  
2.6 
Declaration of interest  
There are no conflicts of interest. 
2.7 
Patient Information and Informed Consent 
All participants included in the trial are adults with recurrent kidney stone disease. No vulnerable 
individuals will be included in the trial. The participation in the trial is voluntary. The investigators will 
explain to each participant the nature of the study, its purpose, the procedures involved, the expected 
duration, the potential risks and benefits and any discomfort it may entail. Each participant will be 
informed that the participation in the study is voluntary and that he/she may withdraw from the study at 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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any time and that withdrawal of consent will not affect his/her subsequent medical assistance and 
treatment. The participant will be informed that his/her medical records may be examined by 
authorised individuals other than their treating physician. All study participants will be provided with a 
participant information sheet and a consent form describing the study and providing sufficient 
information for the participant to make an informed decision about their participation in the study. 
Participants willing to participate will sign and date the informed consent form. The consent form will 
also be signed and dated by the investigator (or his designee) and it will be retained as part of the 
study records. A copy of the signed document will be given to the participants. Only after obtaining 
formal consent with the approved consent form, participants will be submitted to any study procedure. 
No compensation is foreseen and informed consent for general and further use of data and/ or 
biological samples will not be sought. 
2.8 
Participant privacy and confidentiality  
The investigator affirms and upholds the principle of the participant's right to privacy and that they 
shall comply with applicable privacy laws. Especially, anonymity of the participants shall be 
guaranteed when presenting the data at scientific meetings or publishing them in scientific journals. 
Individual subject medical information obtained as a result of this study is considered confidential and 
disclosure to third parties is prohibited. Subject confidentiality will be further ensured by utilising 
subject identification code numbers to correspond to treatment data in the computer files. For data 
verification purposes, authorised representatives of the Sponsor (-Investigator), the CA, or CEC may 
require direct access to parts of the medical records relevant to the study, including participants’ 
medical history. 
2.9 
Early termination of the study  
The Steering Committee may terminate the study prematurely according to certain circumstances, for 
example: 
- 
ethical concerns, 
- 
financial issues, 
- 
insufficient participant recruitment, 
- 
when the safety of the participants is doubtful or at risk, respectively, 
- 
alterations in accepted clinical practice that make the continuation of a clinical trial unwise,  
- 
early evidence of benefit or harm of the experimental intervention,  
- 
or any other reason that would prevent the project execution according to the research plan. 
 
Premature study end or interruption of the study will be reported to the CEC and CA within 15 days. 
2.10 Protocol amendments 
The Steering Committee will decide on protocol amendments. Any investigator, CEC or CA will be 
able to provide suggestions for a protocol amendment. Important protocol modifications will be 
communicated by the Sponsor-Investigator to relevant parties (CEC, CA, trial participants, trial 
registries and the Swiss National Science Foundation). 
Substantial amendments will only be implemented after approval of the CEC and CA, respectively. 
Under emergency circumstances, deviations from the protocol to protect the rights, safety and well-
being of human subjects may proceed without prior approval of the sponsor and the CEC/ CA. Such 
deviations shall be documented and reported to the sponsor and the CEC/ CA as soon as possible. All 
non-substantial amendments are communicated to the CA as soon as possible if applicable and to the 
CEC within the Annual Safety Report (ASR). 
3. BACKGROUND AND RATIONALE  
3.1 
Background and Rationale  
Introduction: 
Nephrolithiasis is a worldwide healthcare problem with a current lifetime risk of ~18.8% in men and 
~9.4% in women in Western civilizations [1]. Incidence and prevalence of renal stone disease are 

 
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increasing globally, irrespective of age, sex and race [1, 2]. Without a specific treatment, 5- and 20-
year recurrence rates are ~40% and ~75%, respectively [3, 4]. In the United States, hospitalizations, 
surgery and lost work time associated with kidney stones cost more than 5 billion US Dollars annually 
[5]. Thus, given the high cost and the morbidity related to recurrent kidney stone disease, medical 
prophylaxis seems to be an attractive approach [6, 7]. Indeed, apart from its benefits to patients in 
terms of reduced morbidity and risk from procedures, medical prevention of nephrolithiasis is clearly 
cost effective [8].  
Although various inherited and systemic diseases are associated with kidney stones, most stones are 
idiopathic [3]. Despite this, nephrolithiasis needs to be considered as a systemic disease. Chronic 
kidney disease (CKD), arterial hypertension, obesity, diabetes mellitus and low bone mass are much 
more prevalent in stone formers than in non-stone formers and contribute significantly to stone-related 
morbidity and mortality [9-15]. It is, however, currently unclear if stone disease is a cause of this co-
morbidity or if it is a consequence of the same underlying conditions that lead to these disorders and 
renal stone disease. 
80-90% of stones are composed of calcium oxalate, calcium phosphate or a mixture of both [16, 17]. 
Increased excretion of calcium in the urine, hypercalciuria, is the most frequent metabolic abnormality 
encountered in patients with recurrent idiopathic nephrolithiasis [17, 18]. Depending on the stone 
subtype, hypercalciuria is present in up to 87% of patients with calcium-containing kidney stones [17]. 
Other urinary factors frequently encountered in recurrent calcareous stone formers that contribute to 
the development of stones are hypocitraturia, hyperoxaluria, hyperuricosuria and low urinary volume 
[19]. Supersaturation of urinary calcium oxalate and calcium phosphate, expressed as the ratio of 
concentration to its solubility, is the driving force for stone formation. At a supersaturation < 1, crystals 
dissolve, at a supersaturation > 1, crystals form. Hypercalciuria increases supersaturation both for 
calcium oxalate and calcium phosphate and thus increases the risk for both calcium oxalate and 
calcium phosphate stones [3]. Urinary supersaturations calculated from ambulatory 24 hour urine 
collections are highly correlated with the type of kidney stones encountered in the individual stone 
former, with notable rare exceptions in patients with very high or very low urinary volumes [20]. The 
hypercalciuria encountered in recurrent stone formers is often familial and strongly influenced by diet 
but in most cases of unknown origin and hence designated “idiopathic” [3]. Gut absorption of calcium 
is enhanced in idiopathic hypercalciuria, but serum calcium remains typically normal because 
intestinally absorbed calcium is promptly excreted by the kidneys [21]. Despite intestinal calcium 
hyperabsorption, patients with idiopathic hypercalciuria are often in negative calcium balance because 
of excessive renal calcium losses, especially under a low calcium diet [19, 22]. The source of calcium 
in these circumstances is the skeleton, the largest repository of calcium in the body [19]. Not 
surprising therefore, low bone mass is a frequent finding in normo- and especially hypercalciuric stone 
formers [9]. At the moment, thiazide diuretics are the only drugs known to reduce urinary calcium 
excretion. This peculiar property is employed in the prevention of recurrent calcareous nephrolithiasis 
but also in the prevention of bone loss in patients with recurrent nephrolithiasis and/ or arterial 
hypertension [9, 23]. Observational data and evidence from prospective trials indicate that chronic 
thiazide therapy preserves bone mineral density and reduces fracture risk [24-27]. 
Clinical work-up of patients with recurrent nephrolithiasis includes a detailed history and physical 
examination as well as blood and urine analysis to detect potential causes of stones but also possible 
associated conditions [23]. Spot urine analysis is performed to search for crystalluria and rule out 
infection [23]. Paramount for the metabolic work-up are 24 h urine collections, which are typically 
performed twice, since mineral excretions have considerable day-to-day variations [23, 28, 29]. 
Metabolic work-up for stone disease is done at least 3 months after a symptomatic stone event in 
patients which have resumed their usual diet and activity [30]. All passed stones need to be analyzed 
for classification purposes but also to detect possible treatment related conversions of one stone type 
to another (e.g. calcium oxalate to calcium phosphate by citrate-induced urinary alkalinization) [3, 31]. 
Computed tomography (CT) without the use of contrast material is the most sensitive method to detect 
renal and ureteral stones and should, according to current guidelines, be preferred to plain abdominal 
X-ray imaging (KUB radiography) or intravenous urography (IVU) in the case of a symptomatic stone 
event [23, 31-33]. Modern low-dose CT protocols cause greatly reduced radiation exposure while 
preserving a high sensitivity of 96.6% and specificity of 94.9% [34]. Current radiation exposure of low 
dose CT protocols for the detection of urolithiasis is in the range of 0.97-1.9 mSV and thus similar to 
KUB radiography (0.5 – 1 mSv) but significantly lower than IVU (1.3 -3.5 mSv) or regular dose CT (4.5 
– 5 mSv) [23, 35, 36]. 
Follow-up studies are necessary in patients taking preventive measures for stone recurrence [23, 37]. 
American and European guidelines recommend a first follow-up 24 hour urine collection 8-12 weeks 
after initiation of therapy to adjust drug dosage [23, 31]. Also, periodic blood testing in patients on 

 
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pharmacological treatment to assess for adverse events (AEs) are recommended [31]. In the case of 
thiazide diuretics, a repeat blood draw with serum electrolytes is typically done within the first few 
weeks of treatment initiation to rule out electrolyte abnormalities, especially hypokalemia. In the case 
of the latter, oral potassium supplementation or a potassium-sparing diuretic like spironolactone or 
amiloride can be additionally prescribed [31]. Once urinary parameters have been normalized and 
blood parameters are stable, yearly blood and urine analysis is recommended [23, 31]. In addition to 
metabolic studies, periodic follow-up imaging studies, preferably with low dose CT, are equally 
recommended to assess for stone growth or new stone formation [23, 31]. A one-year imaging interval 
is currently recommended for stable patients on medical stone prevention [23, 31].  
 
Current knowledge on the efficacy of thiazides in recurrent nephrolithiasis: 
The first thiazide diuretic chlorothiazide was synthesized in 1957 by Sprague and Novello [38]. In 1959, 
Lamberg and Kuhlbäck reported the observation that the thiazides chlorothiazide and 
hydrochlorothiazide (HCTZ) reduce urinary calcium excretion [39]. Soon thereafter, Lichtwitz and 
colleagues suggested that this peculiar property might be exploited to prevent recurrence of calcium-
containing kidney stones [40]. In 1970, Yendt et al. reported initial observations of an uncontrolled 
series of 72 recurrent calcium stone formers treated with HCTZ in doses from 100 mg to 200 mg daily 
[41]. The treatment seemed highly effective: compared to pretreatment, HCTZ at such doses reduced 
stone episodes from 0.57 to 0.03 per patient year in patients without radiologic evidence of stone 
disease at treatment start and from 1.1 to 0.53 per patient year in patients with residual stone load at 
treatment initiation. Similar findings were reported by the same group in a follow up publication several 
years later with a total of 346 patients [42]. Based on these publications, despite the absence of 
randomized controlled trials (RCTs), thiazide rapidly became a cornerstone of medical stone 
prevention.  
In August 2015, we conducted a systematic database search for RCTs that tested the efficacy of 
thiazides in the prevention of recurrent nephrolithiasis. Our search covered MEDLINE, the Cochrane 
Database, Google Scholar and the Web of Science for English language trials that had clinical 
endpoints (symptomatic or radiologic stone recurrence) and at least 1 year of follow-up. We also 
searched for unpublished trials at the World Health Organization’s International Clinical Trials Registry 
Platform (www.who.int/trialsearch), the NIH funded site ClinicalTrials.gov (https//:clinicaltrials.gov) and 
on internet databases provided by the US Food and Drug Administration and by the European 
Medicines Agency [42]. Our search revealed 11 published RCTs [43-53] and no unpublished trials. All 
11 RCTs identified are depicted in Table 3.1-1. The first RCT for stone prevention with thiazide 
diuretics was published in 1981. At total of seven trials were conducted in the 1980’s, three in the 
1990’s and only one trial was conducted after the year 2000. As shown in Table 1, with the exception 
of two trials [51, 53], which were the first two RCTs conducted in the field, thiazides significantly 
reduced stone recurrence compared to placebo or control, in average by about 50% (Table 1). The 
thiazides employed in the two negative trials were bendroflumethiazide at the dosage of 2.5 mg three 
times daily and HCTZ at the dosage of 25 mg twice daily. Follow-up duration of the two negative trials 
was very short (1 and 1.6 years, respectively) compared to 2 – 5 years in the positive trials, which may 
explain the lack of benefit observed. All trials were small and only one trial included > 100 patients [47]. 
The 11 trials included 693 patients in total (Table 1). In three trials, the outcome was symptomatic 
stone recurrence, in the other eight trials the outcome was a composite of symptomatic and radiologic 
recurrence (Table 3.1-1). In all trials, radiologic recurrence was studied with the low sensitivity and 
specificity imaging modalities, KUB or IVU. A consistent finding in these thiazide RCTs was that stone-
formation rate between treated and control groups did not begin to diverge until after at least one year 
of therapy [54]. As detailed in Table 3.1-1, our review indicates that all thiazide RCTs thus far 
conducted have significant methodological deficiencies including unclear allocation concealment, lack 
of double-blinding, no intention-to-treat analysis and lack of AE and drop out reporting.  
Interestingly, in only three of 11 RCTs hypercalciuria was an inclusion criterion and thiazides seem to 
be effective in reducing stone recurrence regardless of the presence or absence of hypercalciuria 
(Table 3.1-1). There are at least two possible explanations for this observation: first, Curhan et al. 
demonstrated in a large epidemiological study that calciuria is a gradual risk factor for the 
development of kidney stones [55]. An increase in the relative risk for kidney stone formation was 
observed when urinary calcium excretion exceeded 2.5 mmol/d, which is far below the current 
definition of hypercalciuria on a random outpatient diet (> 7.5 mmol/d). Second, thiazides, in addition 
to reducing calciuria, have favorable effects on other urinary constituents that may reduce stone risk. 
The latter include reduction of urinary pH and oxalate excretion and an increase of urinary magnesium 
and zinc excretion [56, 57]. 
HCTZ was used in five of the 11 thiazide trials and thus is currently the best studied thiazide in the 

 
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prevention of stone recurrence [45, 48, 50, 52, 53]. However, bendroflumethazide, chlorthalidone, 
trichlormethiazide and indapamide also reduced stone recurrence in one or more trial and seem to be 
effective as well (Table 3.1-1). In all trials, high thiazide doses were employed, in the case of HCTZ, 
50 - 100 mg daily. In four of the five trials where HCTZ was employed, the diuretic was given twice 
daily, whereas in the treatment of arterial hypertension, HCTZ is given once daily [54]. Apart from 
reducing blood pressure, once daily HCTZ at 50 mg, 25 mg or 12.5 mg daily also reduced calciuria, a 
surrogate marker for stone prevention [58]. Twice daily HCTZ increases the frequency of side effects 
and augments diuresis at night and thereby likely affects compliance [54, 58].  
A recent study showed that thiazide diuretics are often not used in an evidence-based fashion for the 
prevention of stone recurrence [59]. In that study, 107 patients with a filled prescription for thiazide 
diuretics that underwent a 24-hour urine stone risk factor analysis and had medical record 
documentation that the thiazide was prescribed for calcium-containing kidney stone recurrence were 
analyzed. Only 35% of HCTZ-treated patients received ≥50 mg/ d, a dose previously shown to 
reduce stone recurrence in RCTs. 52% of patients were prescribed 25 mg daily and 13% 12.5 mg 
daily, doses which were not studied in RCTs. The tendency to prescribe lower doses of thiazides in 
patients with recurrent nephrolithiasis was likely triggered by a paradigm shift in prescribing practices 
for thiazides used for the treatment of arterial hypertension. Starting in the 1980’s, lower doses of 
HCTZ (12.5–25 mg daily) were increasingly employed [60]. While clinical and biochemical side effects 
were noted to be dose dependent, the antihypertensive effects remained robust, even at lower doses 
[60, 61]. If this is also true for recurrent calcareous nephrolithiasis is currently unknown. 
Fink et al. recently conducted a systematic review of RCTs for the medical management to prevent 
recurrent nephrolithiasis [62]. RCTs involving dietary or pharmacologic treatments to prevent recurrent 
kidney stones in adults that reported clinical outcomes or harms were included in the meta-analysis. 
The search of the authors covered MEDLINE, the Cochrane Database, Google Scholar and the Web 
of Science for English-language studies published from 1948 through 2011. Using criteria developed 
by the Cochrane Collaboration, individual study quality was rated good, fair or poor on the basis of 
adequacy of allocation concealment, blinding, reporting reasons for attrition and how analyses 
accounted for incomplete data. Following methods developed by the Agency for Healthcare Research 
and Quality (AHRQ)’s Effective Health Care Program [63], strength of evidence (SOE) for the efficacy 
of each treatment was graded on the basis of risk of bias, consistency, directness and precision. The 
review was nominated to the AHRQ by the American Urological Association but was funded by the 
AHRQ. A total of 28 trials (8 dietary and 20 pharmacologic) were included in the meta-analysis. Six of 
the 11 thiazide trials we identified in our own database search were included in the meta-analysis 
(Table 3.1-1) [43-45, 50, 52, 53]. Patients enrolled in the selected thiazide trials had two or more stone 
events prior to study inclusion, mean treatment duration was 35 months with a cumulative number of 
365 patients. Patients were assigned to thiazide and either placebo [44, 45, 53] or control [43, 50, 52]. 
The authors concluded that AEs were inconsistently reported but that compared with participants in 
the placebo and control groups, those randomly assigned to receive thiazides were statistically 
significantly more likely to withdraw for any reason or because of AEs [62]. Only one of the selected 
trials assessed symptomatic stone recurrence (treatment versus placebo RR 1.04, 95% CI 0.39 – 2.8) 
[53] and no trial reported radiologic outcomes separately. The other five trials with a cumulative 
number of 300 patients reported a composite endpoint with radiologic and symptomatic stone 
recurrence. Treatment with thiazides decreased the risk for this composite outcome (26 vs. 55%; RR 
0.52, 95% CI 0.39 – 0.69; NNT 3.4). Fink et al. stated in their review that the meta-analysis was 
greatly limited by the available data and that additional trials are warranted [62]. Critical points raised 
were i) the low amount of trials available and the small sample sizes, ii) lack of data on treatment 
harms, iii) the fact that all trials included only adults with idiopathic calcium stones, iv) lack of 
symptomatic stone recurrence reporting as an isolated outcome, v) the fact that only one trial recruited 
patients from a primary care setting and vi) inconsistent reporting and categorization of baseline 
biochemistry measures. 
Overall, the authors concluded that all six thiazide trials included in their meta-analysis were of fair 
quality and that there was moderate SOE for the composite end point of symptomatic and radiologic 
stone recurrence but that there was insufficient SOE for the individual outcomes symptomatic or 
radiologic stone recurrence [62]. 

 
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Rationale: 
We and others [62] identified major issues in design, conduct, analysis and reporting in thiazide RCTs 
conducted thus far for the prevention of stone recurrence.  
 
Major issues encountered include: 
- 
Lack of double-blinding 
- 
Lack of intention-to-treat analysis 
- 
Unclear allocation concealment 
- 
Lack of AE and drop out reporting 
- 
Unknown baseline risk of disease severity or biochemical abnormalities 
- 
Lack of patients stratification based on stone composition 
- 
Lack of outcome uniformity 
- 
Absence of data on the impact of pharmacological interventions on disease risk factors 
- 
Low overall number of patients studied 
- 
Use of high dose thiazide treatments 
- 
Inadequate dietary measures in control and treatment groups 
- 
Use of low sensitivity and low specificity imaging for radiologic outcomes 
- 
Use of outdated dietary recommendations in placebo or control groups 
 
The methodological deficiencies are of great concern. Review of the trials reveals that none of the 11 
trials fulfills the quality standards expected of a randomized, placebo-controlled, double-blind trial. 
While the methodological deficiencies of the trials are obvious for anyone concerned with clinical 
research, several points peculiar to kidney stone disease deserve further explanation:  
 
Drug dosing: High doses of thiazides were employed in these trials, in the case of the best studied 
thiazide, HCTZ, 50 - 100 mg daily. At such high doses, side effects occur in 30 – 40% of patients and 
include electrolyte disturbances, muscle cramps, orthostatic hypotension, gastrointestinal symptoms, 
hypocitraturia, gout, impaired glucose tolerance, skin rashes and erectile dysfunction [52, 56]. Since 
AE and drop out reporting in all trials was very poor, tolerability and harms of high dose thiazide 
treatments remain largely unknown. Nowadays, thiazides are widely used in the treatment of arterial 
hypertension and recurrent nephrolithiasis, but at significantly lower doses [54, 58, 59]. However, this 
practice is not supported by randomized evidence in the case of recurrent nephrolithiasis and 
consequently, we do not know whether the currently employed low dose thiazide regimens are 
effective in reducing the risk for stone recurrence.  
Dietary interventions: Non-pharmacologic interventions for recurrence prevention are very effective 
[62]. Several landmark trials investigating the effect of dietary measures to prevent stone recurrence 
were published after the thiazide trials had been completed [64, 65]. In idiopathic recurrent calcareous 
stone formers, high fluid intake or a diet restricted in animal protein and salt combined with a normal 
calcium intake each reduce stone recurrence by ~50% [64, 65]. In fact, the thiazide trials were 
conducted at a time when recurrent calcareous stone formers were given the advice to limit dietary 
calcium intake, a long-held opinion that has since been refuted both by observational data and a 
prospective RCT [65, 66]. Thus, the added benefit of thiazides to current state-of-the non-
pharmacologic measures in stone prevention remains unknown. 
Imaging modality for radiologic outcomes: Some patients with “recurrent” stones in past thiazide RCTs 
may have already harbored the stones at baseline and experienced stone passage rather than 
progression of disease. The latter is also the most likely explanation for the repeated observation 
made in past RCTs (beyond thiazides) concerned with recurrence prevention of renal stones that 
stone incidence in treatment and control groups are diverting only after one year of treatment or later, 
although most patients were considered “stone free” at study initiation, based on KUB or IVU imaging. 
Although CT is by far the most sensitive and most specific imaging modality for renal stone disease, 
no thiazide trial (or any other RCT concerned with kidney stone prevention) thus far used this imaging 
modality to monitor progression of stone disease. As outlined earlier, modern low-dose CT protocols 
cause greatly reduced radiation exposure while preserving a high sensitivity and specificity, making 
low-dose CT the kidney stone imaging modality of choice to monitor disease progression.  
Thus, in summary, benefits and harms of thiazide treatments in general for the prevention of stone 
recurrence are still unclear. In addition, the efficacy of the currently employed low dose thiazide 
regimens to prevent stone recurrence is not known. 
3.2 
Investigational Product (treatment, device) and Indication  
HCTZ belongs to the group of thiazide diuretics. Thiazide diuretics inhibit the sodium/ chloride co-

 
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transporter (NCC or SLC12A3) in the distal tubule of the kidney. Inhibition of NCC causes an 
increased excretion of sodium, chloride and water in the urine and thereby lowering of blood pressure. 
At the same time, thiazide diuretics reduce renal calcium excretion by a still ill-defined intrarenal 
mechanism. In Switzerland, HCTZ as monosubstance is marketed exclusively as Esidrex® by 
Novartis Pharma Schweiz AG in divisible tablets of 25 mg. The approved indications include: arterial 
hypertension, edemas, heart failure and recurrence prevention of calcium-containing kidney stones. 
For the treatment of arterial hypertension, Esidrex® is recommended in doses of 12.5 - 50 mg, once or 
twice daily. For the recurrence prevention of calcareous nephrolithiasis, Esidrex® is recommended in 
doses of 25 or 50 mg twice daily (Esidrex® summary of product characteristics, November 2014). In 
addition to the monosubstance, HCTZ is currently available in 78 different galenic formulations in 
Switzerland as combination with ACE-inhibitors, angiotensin II receptor blockers or non-thiazide 
diuretics (www.swissmedicinfo.ch, last accessed on 11.08.2016).  
Detailed information to pharmacokinetics, side effects and interaction profile of HCTZ can be found at 
www.swissmedicinfo.ch. 
3.3 
Preclinical Evidence  
There is no animal model, which recapitulates the pathophysiology of calcareous nephrolithiasis in 
humans. Hence, there is no supportive preclinical evidence for this trial. However, there is ample 
evidence that thiazide diuretics reduce calciuria, a surrogate marker for calcareous nephrolithiasis, in 
a wide variety of mammals. 
3.4 
Clinical Evidence to Date  
The clinical evidence on the efficiency of HCTZ in recurrence prevention of calcareous nephrolithiasis 
has been reviewed in detail in section 3.1. 
3.5 
Dose Rationale: Rationale for the intended purpose in study 
Our systematic review of thiazide trials in the prevention of recurrent nephrolithiasis in section 3.1 
reveals that the type of thiazide used and the dose regimens employed varied widely. Although the 
evidence is currently very limited, no thiazide seems to be superior for stone prevention. As outlined 
earlier, a common theme of all trials was that very high doses of thiazides were employed. Only in one 
trial more than one dose of thiazide was tested [45]. In that trial, chlorthalidone 25 mg and 50 mg daily 
were equally effective in preventing the primary outcome stone recurrence compared to placebo. 
While the reduction in calciuria compared to placebo was also not different between the two dose 
regimens, 25 mg chlorthalidone daily reduced oxaluria significantly whereas 50 mg chlorthalidone 
daily did not. In contrast, however, 50 mg chlorthalidone daily caused more frequent and more 
pronounced hypokalemia than 25 mg chlorthalidone daily. HCTZ is by far the best studied thiazide 
diuretic for both currently recognized indications, arterial hypertension and recurrent calcareous 
nephrolithiasis [55]. In addition, HCTZ (once daily) is the thiazide most commonly found in 
combination drugs prescribed for the treatment of arterial hypertension. Based on these facts, we 
decided to use HCTZ for the NOSTONE trial. To improve compliance and reduce side effects, we plan 
to compare 12.5 mg or 25 mg or 50 mg HCTZ once daily to placebo. As is the case for all thiazides, 
HCTZ has an excellent bioavailability and thus will be given per os. 
3.6 
Explanation for choice of comparator (or placebo)  
Dietary and lifestyle interventions are highly effective in preventing recurrence in calcareous 
nephrolithiasis and are thus always the basis of stone prevention [63]. As such, any trial assessing 
pharmacologic interventions for the prevention of stone recurrence must compare the efficacy of the 
drug treatment to the state-of-the-art non-pharmacologic interventions. On the basis of RCT evidence, 
current American [31] and European [23] nephrolithiasis guidelines recommend the following non-
pharmacologic measures in adult patients with recurrent calcareous nephrolithiasis: increased fluid 
intake with circadian drinking to ensure daily urinary volumes of at least 2 – 2.5 L, a balanced diet rich 
in vegetables and fibers with normal calcium content (1-1.2 g/day) but limited NaCl (4-5 g/day) and 
animal protein (0.8-1 g/kg/day) content. Furthermore, patients must be advised to retain a normal body 
mass index (BMI), have adequate physical activity and balance excessive fluid loss. All patients in the 
placebo and treatment arms of our planned study will receive these current non-pharmacologic 
recommendations for stone prevention. Since the added benefit of thiazides to current state-of-the 
non-pharmacologic measures in stone prevention remains unknown, as outlined in detail in section 3.1, 
a placebo arm needs to be part of this trial. 

 
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3.7 
Risks/ Benefits 
Calcareous nephrolithiasis is a disease with high recurrence rates that causes high morbidity in 
affected individuals with repeated exposures to urological procedures. The risk a patient is willing to 
accept is a personal decision based on his/ her individual and familial experience with the disease. 
HCTZ potentially lowers the recurrence risk of the disease, although in the dosages applied in the 
study it has not yet been approved for this indication. HCTZ has been used for the treatment of arterial 
hypertension in the dosages tested in this study for over 40 years. Thus, the treatment risks by HCTZ 
are well characterized, manageable and must be weighed against the consequences of no treatment. 
The most common AEs of HCTZ therapy include those arising from saluresis including reduction of 
blood pressure, polyuria, dehydration and electrolyte abnormalities. Therefore, appropriate patient 
monitoring and management will be implemented to mitigate this potential risk in the kidney stone 
population. These AEs should be considered in light of the benefits of a reduced risk of stone 
recurrence, including pain, urinary tract infection and need for urological interventions. With sufficient 
knowledge of the benefits and risks and risk mitigation strategies, patients and their physicians may 
make informed decisions about HCTZ treatment. In the final assessment, the overall benefit-risk 
profile of HCTZ for the recurrence prevention of calcareous nephrolithiasis appears favourable, 
offering a real opportunity to fill a longstanding unmet medical need. 
The results of the study, will yield important clinical information for the care of patients with recurrent 
calcareous nephrolithiasis, which is one of the most frequent human diseases (~10% of worldwide 
population affected). Study participants who finished the trial or stopped the IMP during the trial will be 
seen in the different ambulatory stone clinics of the participating centers at least annually, if medical 
condition warrants, more frequently. 
Because the detection rate of plain abdominal X-ray imaging (KUB radiography) for urinary stones is 
far inferior to the detection rate of CT or IVU, and because often several KUBs in different angles have 
to be performed for a better detection of kidney stones, the international guidelines recommend low-
dose CT for the detection and follow-up of urinary stone patients [23, 31-33]. Modern low-dose CT 
protocols cause greatly reduced radiation exposure while preserving a high sensitivity of up to 98% 
[69] and specificity of up to 97% [34, 35, 69]. Current radiation exposure of low dose CT protocols for 
the detection of urolithiasis is in the range of 0.5-1.9 mSV, and thus similar to (single) KUB 
radiography (0.5 – 1.1 mSv) but lower than IVU (1.3 -3.93 mSv) [20, 23, 35, 36, 70]. The international 
guidelines recommend imaging of recurrent stone formers at least once a year [31]. Thus, yearly 
imaging with low dose CT is in line with the international guidelines [31] and with our daily practice 
(usually 6-monthly to yearly imaging). It is a rather conservative imaging strategy compared to other 
centers, and leads to a relatively low radiation exposure which does not exceed the standard radiation 
dose for recurrent stone formers during regular follow-up. Even more, the radiation exposure of our 
patients is far lower than the 50 mSv throughout a single year or the 20 mSv per year over a 5-year 
period as accepted as the threshold levels for “safe” exposure by the International Commission on 
Radiological Protection (ICRP) [71]. 
3.8 
Justification of choice of study population 
For the trial, thiazide naïve adult individuals with recurrent calcareous nephrolithiasis will be recruited. 
80 – 90% of patients with recurrent nephrolithiasis belong into this group. Hence, the study population 
will be representative of the far most common type of renal stone former encountered in clinical 
routine. Recurrent is defined as two or more stone episodes in the last 10 years, calcareous is defined 
as 50% or more calcium oxalate, calcium phosphate or a mixture of both in a previous stone analysis. 
No vulnerable individuals will be included in the study. 
4. STUDY OBJECTIVES  
4.1 
Overall Objective 
The study aims to describe an efficacy and safety profile of HCTZ for the recurrence prevention of 
calcareous nephrolithiasis. 

 
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4.2 
Primary Objective 
Dose-response relationship for three different dosages of HCTZ using incidence of stone recurrence 
(a composite of symptomatic or radiologic recurrence) as the primary outcome. 
4.3 
Secondary Objectives 
Efficacy of the different dosages of HCTZ in terms of the primary outcome as well as the individual 
components of the composite primary outcome, i.e. incidence of symptomatic stone recurrence and 
incidence of radiologic stone recurrence. Effects of different dosages of HCTZ on urinary biochemistry 
(efficacy and safety aspects) and the impact of different baseline characteristics on the effects of the 
different dosages (effect modification). 
4.4 
Safety Objectives 
Long-term safety and tolerability of HCTZ compared to placebo. 
5. STUDY OUTCOMES  
5.1 
Primary Outcome 
5.1.1 
Primary outcome at patient level 
The primary outcome at the patient level is the incidence of stone recurrences during study treatment. 
Stone recurrence is the composite of symptomatic or radiological recurrences. 
 
Symptomatic stone recurrence is defined as visible passage of a stone with accompanying typical 
symptoms such as flank/ loin pain and hematuria or a symptomatic or asymptomatic stone requiring 
urological intervention for stone removal. 
 
Radiological stone recurrence as assessed by low-dose non-intravenous (iv) contrast CT imaging is 
defined as the appearance of new caliculi or enlargement of preexisting caliculi with reference to the 
baseline CT performed at visit 3. Renal CTs for the assessment of stone recurrences are performed 
whenever there is a suspicion of symptomatic recurrence (standard procedure in symptomatic patients 
irrespective of the study) and at the end of study treatment. 
5.1.2 
Primary outcome at study level 
Relationship of the incidence of stone recurrences during study treatment and dose group. 
5.2 
Secondary Outcomes 
Secondary outcomes are the following: 
- 
The individual components of the composite primary outcome, i.e. number of symptomatic stone 
recurrences and number of radiologic stone recurrences 
- 
Changes in urinary biochemistry elicited by HCTZ or placebo 
- 
Impact of baseline disease severity (incidence of stone recurrence during life time prior to 
randomisation) and biochemical abnormalities on stone recurrence 
- 
Impact of stone composition on stone recurrence 
 
Given the high prevalence of the disease [1, 2], the morbidity, pain and costs associated with 
symptomatic stone disease [5] as well as the high likelihood of asymptomatic stones to become 
symptomatic [67], our chosen outcomes are clinically highly relevant. 
5.3 
Other Outcomes of Interest 
None. 
5.4 
Safety Outcomes 
Safety endpoints to be analyzed include a descriptive summary of the following parameters: 

 
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6.2 
Methods of minimizing bias  
6.2.1 
Randomization  
We will use stratified randomization to assign participants to the different trial arms with the number of 
previous stone events as stratification factors: stratification group 1: 2 or 3 stone events within 10 
years prior to randomization; stratification group 2: ≥ 4 stone events within 10 years prior to 
randomisation. Allocation will be concealed using sequentially coded drug packs that are otherwise 
identical. Preparation and handling of the unblinded drug packs will be done at a facility otherwise not 
involved in the trial. Randomization lists at CTU Bern will be stored electronically with no access for 
persons directly involved in the trial. Allocation to the trial arms will be done using numbered drug 
packs. Randomization lists will be generated by a statistician at CTU Bern otherwise not involved in 
the trial following dedicated standard operating procedures. The statistician will communicate directly 
with the facility, which prepares the drug packs (Grosse Apotheke Dr. G. Bichsel AG, Interlaken, 
Switzerland). Investigators at each site will assign the drug pack with the next sequential number to 
the next patient (consecutive). Content of the drug packs is based on randomization lists as described 
above. 
6.2.2 
Blinding procedures  
All trial personnel but the statistician generating the list and the personnel at the facility preparing the 
drug packs (Grosse Apotheke Dr. G. Bichsel AG, Interlaken, Switzerland) will be blinded to the 
assigned treatment. Blinding will be upheld until all analyses will have been completed. HCTZ and 
placebo will be provided in identically looking blistered capsules in drug packs. Besides the 
consecutive number, packs and pack content will look identical. Therefore, all trial personnel that is 
involved in recruitment and care of patients, trial assessment, monitoring and analyses will be blinded 
to the assigned trial arm. 
6.2.3 
Other methods of minimising bias  
To minimize referral bias, we plan to collaborate with external Nephrologists, Urologists, Internists and 
Family practitioners. 
To minimize bias of primary outcome assessment for radiological recurrence, all renal CTs will be 
assessed centrally at Inselspital Bern. 
6.3 
Unblinding Procedures (Code break)  
HCTZ is an established drug with a well-known safety profile. Although extremely rare, there are 
reports of allergic reactions either directly or because of sulfonamide cross-sensitivity. Unblinding will 
only be allowed in situations where knowledge of the allocation is needed for the care of a patient. 
Because there is no antidote and the allergic reactions as described in the literature as well as other 
serious adverse reactions such as aplastic anemia or angioedema are treated independently from any 
knowledge of treatment assignment, we do not expect any emergency unblinding. Nevertheless, all 
trial sites will get tamper-proof, sealed, opaque envelopes to allow for emergency unblinding. The 
integrity of the envelopes will be checked at monitoring visits. Opening of an envelope will need to be 
notified to the Sponsor-Investigator within 24 hours. 
Note that a break of the randomization code per se is not a reason to stop study treatment or to 
withdraw the participant from the study. 
7. STUDY POPULATION  
This trial will include adult individuals with recurrent calcareous nephrolithiasis. Outpatients newly 
referred to stone clinics for metabolic stone work-up will be recruited for the trial at 3 Cantonal 
Hospitals (Aarau, Lugano, St. Gallen) and 5 University Hospitals (Basel, Bern, Geneva, Lausanne, 
Zürich) in Switzerland. If enrolment goals are not met, we will 1) try to enhance referrals to trial sites 
by contacting local Urologists and Nephrologists 2) extend recruitment to outpatients with recurrent 
calcareous nephrolithiasis that have already undergone metabolic work-up for stone disease but are 

 
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seen for regular follow-up visits at the trial sites.  
In order to maximize power and minimize the possibility of a Type II error, trial enrollment will continue 
until at least 416 individuals are randomized. 
7.1 
Eligibility criteria  
Individuals fulfilling all of the following inclusion criteria are eligible for the study: 
1. Informed Consent as documented by signature 
2. Age 18 years or older 
3. Recurrent kidney stone disease (≥ 2 stone events within the last 10 years prior to 
randomization) 
4. Any past kidney stone containing 50% or more of calcium oxalate, calcium phosphate or a 
mixture of both 
 
The presence of any one of the following exclusion criteria will lead to exclusion of the individual: 
1. Pharmacologic prevention for stone recurrence less than 3 months prior to randomization 
2. Patients with secondary causes of recurrent calcareous nephrolithiasis including: 
- 
Severe eating disorders (anorexia or bulimia) 
- 
Chronic bowel disease, intestinal or bariatric surgery 
- 
Sarcoidosis 
- 
Primary hyperparathyroidism 
- 
Hyperthyroidism 
- 
Complete distal tubular acidosis 
- 
Active malignancy 
3. Patients with the following medications:  
- 
Thiazide or loop diuretics 
- 
Carbonic anhydrase inhibitors (including topiramate) 
- 
Xanthine oxidase inhibitors (febuxostat or allopurinol) 
- 
Alkali, including potassium citrate or sodium bicarbonate 
- 
Treatment with 1,25-OH Vitamin D (calcitriol) 
- 
Calcium supplementation 
- 
Bisphosphonates 
- 
Denusomab 
- 
Teriparatide 
- 
Glucocorticoids 
4. Obstructive uropathy, if not treated successfully 
5. Urinary tract infection, if not treated successfully  
6. Chronic kidney disease (defined as CKD-EPI eGFR < 60 mL/min per 1,73 m2 body surface 
area 
7. Patients with a kidney transplant 
8. > 3 gout arthritis episodes within one year prior to randomisation or gout arthritis requiring uric 
acid lowering therapy 
9. Cystinuria at screening 
10. Hypokalemia (blood potassium level < 3 mmol/L) at screening 
11. Hyponatremia (blood sodium level < 125 mmol/L) at screening 
12. Pregnant and lactating women [pregnancy test to be performed for women of child-bearing 
potential (defined as women who are not surgically sterilized/ hysterectomized, and/ or who 
are postmenonpausal for less than 12 months)] 
13. Previous (within 3 months prior to randomization) or concomitant participation in another 
interventional clinical trial 
14. Inability to understand and follow the protocol 
15. Known allergy to the study drug 
7.2 
Recruitment and screening  
Target population of the study are individuals who suffer from recurrent calcareous nephrolithiasis. 
Two different groups of individuals will be screened and recruited in the study by local investigators: 1) 
individuals newly referred for metabolic work-up for recurrent stone disease to study sites and 2) 
individuals who already underwent work-up for recurrent stone disease and are currently undergoing 
regular follow-up for recurrent stone disease at the study sites. After approval by the CEC and CA, the 
study will be announced to the Nephrology and Urology staff at the 8 study sites. We will also inform 

 
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external Nephrologists, Urologists, Internists and Family practitioners by emails and kick-off meetings 
upon approval by the CEC and CA. 
If available medical history indicates that an individual may be eligible for study participation, the 
individual will be informed in detail about the study by local investigators. Inclusion in the study will 
take place only upon receipt of written informed consent and if all eligibility criteria are fulfilled. 
No payment or compensation will be given to study participants.  
7.3 
Assignment to study groups  
Stratified randomization will be used to assign participants to the different trial arms with the number of 
previous stone events as stratification factors (see section 6.2.1). Allocation will be concealed using 
sequentially coded drug packs that are otherwise identical. Randomization lists will be generated by a 
statistician at CTU Bern otherwise not involved in the trial following dedicated standard operating 
procedures. The statistician will communicate directly with the facility, which prepares the drug packs 
(Grosse Apotheke Dr. G. Bichsel AG, Interlaken, Switzerland). Investigators at each site will assign 
the drug pack with the next sequential number to the next patient (consecutive). Content of the drug 
packs is based on randomization lists as described above. Preparation and handling of the unblinded 
drug packs will be done at a facility otherwise not involved in the trial. Randomization lists at CTU Bern 
will be stored electronically with no access for persons directly involved in the trial. 
7.4 
Criteria for withdrawal/ discontinuation of participants  
7.4.1 
Discontinuation of study IMP  
Study IMP must be permanently discontinued if any of the following occurs: 
- 
If any exclusion criterion applies during the trial 
- 
If the responsible study investigator feels that treatment with the study regimen is harmful to the 
participant’s well-being 
- 
If patient is non-compliant with the study intervention as judged by the investigator and/ or the 
sponsor 
- 
Pregnancy in a study participant 
- 
Hypokalemia (blood potassium level < 3 mmol/L) not responsive to supplementation therapy 
- 
Profound hyponatremia (blood sodium level < 125 mmol/L) recurring after normalization upon 
temporary suspension of IMP 
- 
Blood creatinine > 150% of creatinine value at screening (visit 2) 
- 
Gouty arthritis recurring > 3 times per year or requiring uric acid lowering therapy. 
- 
Allergic reaction of skin as judged by the investigator 
- 
> 2 recurrences of symptomatic stone events during the trial 
 
Participants who permanently discontinue the IMP are expected to continue in the follow-up period 
and to attend all protocol-specified study visits. If study visits are not possible, a telephone 
consultation will be performed to determine if relevant health events/ endpoints have occurred. 
7.4.2 
Discontinuation of study 
Study participants must be withdrawn from the study if the following occurs: 
- 
At the participants own request 
- 
If, in the investigator's opinion, continuation of the study would be harmful to the subject’s well-
being 
 
A study participant who discontinues study participation prematurely for any reason is defined as 
dropout if the participant has already been randomized. A study participant who terminates the study 
before randomization is regarded as a screening failure. 
 
No replacement of participants discontinuing study treatment or study participation is foreseen. 

 
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8. STUDY INTERVENTION  
8.1 
Identity of Investigational Products 
8.1.1 
Experimental Intervention  
Identical looking gelatin capsules containing 12.5 mg or 25 mg or 50 mg HCTZ will be supplied by 
Grosse Apotheke Dr. G. Bichsel AG, Interlaken, Switzerland according to applicable regulations. 
8.1.2 
Control Intervention  
Placebo gelatin capsules indistinguishable from HCTZ capsules will be supplied by Grosse Apotheke 
Dr. G. Bichsel AG, Interlaken, Switzerland according to applicable regulations. 
8.1.3 
Packaging, Labelling and Supply (re-supply)  
IMP capsules will be provided as bulk supply in bottles labelled with trial-specific labels according to 
Annex 13, "Manufacturing of investigational medicinal products" to Volume IV of the EU guideline to 
Good Manufacturing Practice: 
 
- 
Name, address and telephone number of the sponsor-investigator 
- 
Pharmaceutical dosage form (capsules), route of administration (per os), number of capsules 
- 
Batch number, Lot number 
- 
Trial acronym (Nostone-trial) 
- 
Trial subject identification number 
- 
Storage conditions 
- 
Expiry date 
- 
Safety warning “Keep out of reach of children” 
 
8.1.4 
Storage Conditions  
All IMPs will be stored in a securely locked cabinet or enclosure. Access will be limited to investigators 
and their designees. Neither investigators nor any designees may provide IMP to any subject not 
participating in this protocol. The IMP will be stored according to the conditions specified in the IMP 
label. The clinical site staff will maintain a temperature log in the drug storage area recording the 
temperature using (at minimum) a Min/ Max thermometer at least weekly. 
8.2 
Administration of experimental and control interventions 
8.2.1 
Experimental Intervention  
HCTZ capsules will be administered once daily per os in the morning. HCTZ has excellent 
bioavailability and thus per os administration is chosen for this trial (www.swissmedicinfo.ch). The 
rationale for AM dosing is the fact that HCTZ induces a diuresis that starts 1-2 hours after ingestion, 
peaks 4-6 hours after ingestion and lasts until 10-12 hours after ingestion (www.swissmedicinfo.ch). 
Thus, HCTZ-induced diuresis potentially disturbs sleep of participants when PM dosing is chosen. 
Minimal effective dose for HCTZ-induced diuresis and blood pressure reduction in humans is 12.5 mg 
per os once daily, maximal effective dose 50 mg per os once daily (www.swissmedicinfo.ch). Hence, 
12,5 mg, 25 mg and 50 mg per os once daily were chosen as HCTZ doses for this trial. 
8.2.2 
Control Intervention 
Placebo capsules will be administered once daily per os in the morning, identical to HCTZ capsules. 
8.3 
Dose modifications  
8.3.1 
Electrolyte Disturbances 
Hypokalemia, hyponatremia and hypomagnesemia can occur in patients with HCTZ treatment. In the 
case of hypokalemia (< 3 mmol/L), supplementation with oral potassium chloride or co-administration 
of the potassium-sparing diuretic is recommended. In the case of hypomagnesemia (< 0.5 mmol/L), 
supplementation with oral magnesium aspartate is recommended. Potassium citrate or potassium 

 
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bicarbonate may affect stone recurrence and are not allowed during the trial. If hypokalemia or 
hypomagnesemia are not responsive to the above recommendations, the IMP will be withdrawn from 
the patient. In the case of profound hyponatremia (< 125 mmol/L), temporary suspension of the IMP 
until normalization of the blood sodium concentration is recommended. The IMP can then be 
restarted. If profound hyponatremia recurs, the IMP will be withdrawn from the patient. 
8.3.2 
Renal function impairment 
Because of blood pressure lowering and volume depletion, therapy with HCTZ may worsen renal 
function. If blood creatinine equals or exceeds 150% of the baseline creatinine, the IMP will be 
withdrawn from the patient. 
8.3.3 
Gout arthritis 
HCTZ may increase blood uric acid levels which can cause gout arthritis. An acute gout flare should 
be treated symptomatically with analgesics. Xanthine oxidase inhibitors to lower blood and urine uric 
acid levels may affect stone recurrence and are not allowed during the trial. If gouty arthritis recurs > 3 
times/ year or a uric acid lowering therapy is needed, the IMP will be withdrawn from the patient. 
8.3.4 
Diabetes 
HCTZ may worsen glucose tolerance or induce diabetes mellitus. If overt diabetes mellitus develops 
during the trial (fasting glucose > 7 mmol/L, random glucose > 11 mmol/L or hemoglobin A1c > 7%), 
the patient will be referred to a diabetologist. 
8.3.5 
Allergic reactions 
Occasionally allergic reactions of the skin have been observed in patients with HCTZ treatment. If this 
is suspected, the IMP will be withdrawn from the patient. 
8.3.6 
Symptomatic stone recurrence during the trial 
Patients will remain on study treatment with up to two symptomatic stone events. If a third 
symptomatic stone event occurs during the trial, the IMP will be withdrawn from the patient. 
 
For additional criteria for discontinuing study IMP treatment or study discontinuation see section 7.4. 
8.4 
Compliance with study intervention 
At initial product dispensing and the follow-up visits, including the three-monthly telephone contacts, 
the participants will be reminded about the following: 
- 
The importance of following the study guidelines, including the non-pharmaceutical preventive 
measures and taking the study product once daily  
- 
Instructions about IMP administration including dose, importance of taking the IMP as a whole, 
timing, and noting done any missed dose, and instructions about proper IMP storage 
- 
Notification that there will be IMP counts performed during the trial 
- 
To keep all medication containers, including any unused capsules and to return them to the study 
site at the next scheduled on-site visit 
- 
That IMP may be HCTZ or placebo 
- 
Importance of calling the clinic if experiencing problems possibly related to the study product such 
as symptoms or lost IMP 
 
At the follow-up visits and three-monthly telephone calls, the participants will be asked about any 
problems with regard to taking the IMP using a structured and open-ended questionnaire. There will 
be a discussion of reasons for missed doses and simple strategies for enhancing adherence, e.g. 
linking IMP taking to meals or other daily activities. Participants will have an opportunity to ask 
questions and key messages from the initial session will be reviewed as needed. 
 
Participants will return used, partially used and unused IMP containers at each follow-up visit at the 
study sites and IMP counts will be performed to assess medication adherence and thus enhance data 
validity. 
Depending on the circumstances leading to non-compliance, the subject may be discontinued from 
IMP administration by the investigator and/ or sponsor. A subject who proactively wishes to 
discontinue IMP administration, or has IMP discontinued by the investigator, will be encouraged to 
continue limited participation in the trial, as described in section 7.4. 

 
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8.5 
Data Collection and Follow-up for withdrawn participants  
Participants who permanently discontinue the study treatment are expected to continue in the follow-
up period and to attend all protocol-specified study visits. If study visits are not possible, a telephone 
consultation will be performed to determine if relevant health events/ endpoints have occurred. 
Participants who are withdrawn from further study participation are invited to attend a final visit at 
which the assessments of the End of Treatment visit are performed. 
8.6 
Trial-specific preventive measures 
Dietary and lifestyle interventions are highly effective in preventing recurrence in calcareous 
nephrolithiasis and are the basis of stone prevention [63]. Any trial assessing pharmacologic 
interventions for the prevention of stone recurrence must compare the efficacy of the drug treatment to 
the state-of-the-art non-pharmacologic interventions. Thus, all patients will receive state-of-the-art 
non-pharmacologic recommendations for stone prevention according to current American [31] and 
European [23] nephrolithiasis guidelines including: increased fluid intake with circadian drinking to 
ensure daily urinary volumes of at least 2 – 2.5 L, a balanced diet rich in vegetables and fibers with 
normal calcium content (1-1.2 g/day) but limited NaCl (4-6 g/day) and animal protein (0.8-1 g/kg/day) 
content. Furthermore, patients must be advised to retain a normal BMI, have adequate physical 
activity and balance excessive fluid loss.  
 
The following medications will be prohibited during the trial (reason given in brackets): 
- 
Thiazide diuretics (pharmacodynamic interference with IMP) 
- 
Loop diuretics (pharmacodynamics interference with IMP) 
- 
Carbonic anhydrase inhibitors (increase risk for stone recurrence) 
- 
Xanthine oxidase inhibitors (potentially decrease risk of stone recurrence) 
- 
Alkali, including potassium citrate or sodium bicarbonate (potentially decrease risk of stone 
recurrence) 
- 
Treatment with 1,25-OH Vitamin D (increases risk of stone recurrence) 
- 
Calcium supplementation (increases risk of stone recurrence) 
- 
Bisphosphonates (potentially decreases risk of stone recurrence) 
- 
Denusomab (potentially decreases risk of stone recurrence) 
- 
Teriparatide (increases risk of stone recurrence) 
- 
Glucocorticoids (increases risk of stone recurrence) 
8.7 
Concomitant Interventions (treatments)  
Active recurrence prevention for calcareous nephrolithiasis with thiazide diuretics, alkali or xanthine 
oxidase inhibitors will have to be stopped at least 3 months before an individual can be enrolled 
(randomized) in the study. All medications not listed in section 8.6 will be allowed before and during 
the study as concomitant treatments. The use of concomitant medications will be recorded in the 
eCRF. There are no restrictions to medications or treatments after the study. 
All urological interventions related to symptomatic and asymptomatic stone disease are permitted 
during the trial. Generally, it is recommended to follow patients with asymptomatic stones and wait 
until stones become symptomatic. However, the likelihood for the eventual need of an urological 
intervention depends on the stone diameter. Ureteral stones with a diameter > 7 mm have a likelihood 
of 99% to require a urological intervention in the future [68]. Thus, kidney stones with a diameter > 7 
mm are often removed, even if asymptomatic. In patients with a high risk of complications, including 
those with a solitary kidney or in patients with certain professions (e.g. pilots), even elective removal of 
asymptomatic stones with a diameter ≤ 7 mm may be indicated. Interventional treatment of 
asymptomatic stones of patients enrolled in the trial will be left to the discretion of the treating 
urologists. Removal of an asymptomatic stone will be considered as symptomatic stone event in this 
trial. 
8.8 
Study Drug Accountability  
The investigator or designee must maintain an inventory record of IMP at the site level (received from 
the sponsor, returned to the sponsor) and at the patient level (dispensed to the patient, returned by the 
patient). 
8.9 
Return or Destruction of Study Drug/ Medical Device  
Upon completion or termination of the trial, all unused IMP must be destructed on site following the 

 
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site’s standard procedures for medication destruction and the destruction documented. Documentation 
on IMP destruction must be provided to the sponsor-investigator for filing in the trial master file. 
9. STUDY ASSESSMENTS  
9.1 
Study flow chart(s)/ table of study procedures and assessments 
For work-up and follow-up of participants, the NOSTONE protocol strictly adheres to 
recommendations of the American and European guidelines on nephrolithiasis [23, 31] with regard to 
scheduling of patient visits, lab analyses and imaging. 
For the schedule of assessments refer to “Study Schedule” table at the beginning of this document. 
9.2 
Assessments of outcomes  
In accordance with recommendations of the American and European guidelines on nephrolithiasis [23, 
31], only study participants undergoing first-time work-up for stone disease will be scheduled for Visit 4 
(V4). Participants with past work-up for stone disease that are currently undergoing regular follow-up 
will omit V4, all other Visits (including numbering of Visits) are identical to participants with first-time 
work-up for stone disease. 
9.2.1 
Assessment of primary outcome 
Symptomatic recurrence (for definition see section 5.1.1) will be assessed at the follow-up visits 3, 4, 5 
and 6 as well as at the three-monthly phone calls in between the visits. 
Radiologic recurrence (for definition see section 5.1.1) will be assessed by low-dose, renal-limited 
non-iv contrast CT imaging at visit 2 (defined as reference for stone recurrence during the study), if a 
stone recurrence is suspected during the treatment phase (standard procedure in symptomatic 
patients irrespective of the study), and at treatment end (visit 7 for participants recruited in the first 12 
months of the recruitment period and visit 6 for participants recruited in the remainder of the 
recruitment period). At treatment end, a renal CT is performed only if no other non-iv contrast renal CT 
was performed within 3 months prior to the visit. 
9.2.2 
Assessment of secondary outcomes 
Individual components of the composite primary outcome, i.e. incidence of symptomatic stone 
recurrence and incidence of radiologic stone recurrence will be assessed as described for the primary 
outcome. Changes in urinary biochemistry elicited by the IMP compared to baseline (visit 2) will be 
assessed by chemical analysis of urine samples collected immediately prior to visits 4, 5, 6 and 7 (one 
24 hour collection immediately prior to visit 4; two 24 hours collections within 48 hours immediately 
prior to visits 5, 6 and 7). Impact of baseline disease severity and biochemical abnormalities on stone 
recurrence will be assessed by baseline blood and urine analysis and baseline medical history and 
assessment of the primary outcome as described. Impact of stone composition on stone recurrence 
will be assessed by baseline medical history and assessment of the primary outcome as described. 
9.2.3 
Assessment of other outcomes of interest 
No other outcome assessments are planned. 
9.2.4 
Assessment of safety outcomes 
9.2.4.1 
Serious adverse events (SAEs) 
SAEs will be collected, fully investigated and documented in the source documents and the eCRF for 
all participants from the date of ICF signature until the last protocol-specific procedure has been 
completed, including a safety follow-up period of 30 days. 
9.2.4.2 
Adverse events (AEs) of special interest 
For this trial, (non-serious) AEs will not be documented in the eCRF with exception of the following 
events “of special interest” occurring from the date of randomizatzion (visit 2) until visit 7: 
- 
Hypokalemia, defined as blood potassium level < 3 mmol/L 
- 
Hyponatremia, defined as blood sodium level < 125 mmol/L 

 
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- 
Hypomagnesemia, defined as blood magnesium level < 0.5 mmol/L 
- 
Blood creatinine > 150% of baseline creatinine 
- 
Gouty arthritis if recurrence > 3 times per year or requiring Uric acid lowering therapy 
- 
Newly developed overt diabetes mellitus (defined as fasting glucose level > 7 mmol/L or random 
Glucose > 11 mmol/L or hemoglobin A1c > 7%) 
- 
Allergic reaction of skin if considered by the local investigator to be potentially related to the study 
medication 
9.2.4.3 
Vital signs 
Heart rate, systolic and diastolic blood pressure at the right arm in sitting position after at least 5 
minutes rest will be recorded at visits 1, 4, 5, 6 and 7. 
9.2.5 
Assessments in participants who prematurely stop the study 
Participants who permanently discontinue the study treatment will undergo all protocol-specified study 
visits and assessments. If study visits are not possible, a telephone consultation will be performed to 
determine if relevant health events/ endpoints have occurred. 
9.3 
Procedures at each visit 
9.3.1 
Visit 1 (screening day 1*; -14 days to day -1) 
- 
Patient information and delivery of written study information to subject 
- 
Pre-assessment of eligibility (based on data available per routine) 
- 
Demographics 
- 
Medical history 
- 
Stone composition (all stones analyzed prior to randomization as available) 
- 
General physical examination, including body weight, height 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Concomitant medication 
 
* For participants with first time work-up for kidney stone disease (new referrals), screening 
assessments are performed at visits 1 and 2. For participants in current follow-up for past stone 
disease, all assessments of visit 1 are performed at visit 2. 
9.3.2 
Visit 2 (screening day 2; day 0) 
- 
Written informed consent (if not obtained earlier). Note: In order to give subjects in current follow-
up for past stone disease sufficient time for the decision on study participation, initial patient 
information may be done via phone and the written study information provided to the subject via 
normal post prior to the visit 
- 
Assessment of eligibility 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit; analyzed 
centrally): sodium, potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, 
urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Pregnancy test (performed locally, from blood or urine) for women of child-bearing potential 
(defined as women who are not surgically sterilized/ hysterectomized, and/ or who are 
postmenonpausal for less than 12 months)  
- 
Assessment of SAEs 
- 
Concomitant medication 
9.3.3 
Visit 3 (+2 weeks, visit window ±2 weeks) 
- 
Re-assessment of eligibility 
- 
Randomisation 
- 
Baseline low-dose non-iv contrast renal CT (analyzed centrally; if a routine non-iv contrast renal 
CT was performed within 2 months prior to this visit, the CT does not have to be repeated) 
- 
Collection of information on composition of any new kidney stone since last visit 
- 
Instruction of participant on non-pharmacologic recommendations for stone prevention 
- 
Dispense of IMP (first intake of IMP on the day after visit 3) 

 
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- 
Assessment of SAEs 
- 
Concomitant medication 
- 
If at visit 2, blood sodium was in the range from 125 to 130 mmol/L and/or potassium in the range 
from 3 to 3.5 mmol/L (or if deemed necessary by the responsible principal investigator for any 
other reason), blood sodium and/or potassium level(s) must be re-checked within 1 month after 
visit 3. 
9.3.4 
Visit 4 (+3 months, visit window ±2 weeks) 
Participants with first-time work-up of stone disease: 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Collection of information on composition of any new kidney stone since last visit 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (one 24 hour collections in the 48 hours immediately prior to the visit; analyzed 
centrally): sodium, potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, 
urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Screening for criteria for interrupting or discontinuing study intervention 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Dispense of IMP and collection of used/ unused IMP packs from participant 
Participants in current follow-up for past kidney stone disease: 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last visit and regarding the potential occurrence of events of special interest as far as known to the 
participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Dispense of IMP via normal post 
9.3.5 
In between Visits 4 and 5 (+6 and +9 months, visit window ±4 weeks) 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last contact and regarding the potential occurrence of AEs of special interest as far as known to 
the participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Dispense of IMP via normal post 
9.3.6 
Visit 5 (+12 months, visit window ±4 weeks) 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit; analyzed 
centrally): sodium, potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, 
urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Screening for criteria for interrupting or discontinuing study intervention 

 
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- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Dispense of IMP and collection of used/ unused IMP packs from participant 
9.3.7 
In between Visits 5 and 6 (+15, +18 and +21 months, visit window ±4 weeks) 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last contact and regarding the potential occurrence of AEs of special interest as far as known to 
the participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Dispense of IMP via normal post 
9.3.8 
Visit 6 (+24 months, visit window ±4 weeks) 
Participants recruited during the first 12 months of the recruitment period: 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit; analyzed 
centrally): sodium, potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, 
urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Screening for criteria for interrupting or discontinuing study intervention 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Dispense of IMP and collection of used/ unused IMP packs from participant 
 
Participants recruited ≥ 12 months after start of the recruitment period: 
This visit corresponds to the end of treatment visits for participants who were recruited ≥ 12 months 
after start of the recruitment period. This visit is followed by the safety follow-up telephone call (see 
section 9.3.11) 
 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit; analyzed 
centrally): sodium, potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, 
urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Low-dose non-iv contrast renal CT (analyzed centrally; if a routine non-iv contrast renal CT was 
performed within 3 months prior to this visit, the CT does not have to be repeated) 
- 
Assessment of symptomatic stone recurrence 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Collection of used/ unused IMP packs from participant 
9.3.9 
In between Visits 6 and 7 (+27, +30 and +33 months, visit window ±4 weeks) 
Only for participants recruited during the first 12 months of the recruitment period: 
 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last contact and regarding the potential occurrence of AEs of special interest as far as known to 
the participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 

 
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stone prevention) 
- 
Dispense of IMP via normal post 
9.3.10 Visit 7 (+36 months, visit window ±4 weeks) 
Only for participants recruited during the first 12 months of the recruitment period: 
 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit; analyzed 
centrally): sodium, potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, 
urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Low-dose non-iv contrast renal CT (analyzed centrally; if a routine non-iv contrast renal CT was 
performed within 2 months prior to this visit, the CT does not have to be repeated) 
- 
Assessment of symptomatic stone recurrence 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Collection of used/ unused IMP packs from participant 
9.3.11 Safety follow-up (30 days after end of treatment, visit window ±2 weeks) 
- 
Assessment of SAEs (telephone call) 
9.3.12 Study-specific procedures 
The following procedures are study-specific: 
- 
Pregnancy test for women of child-bearing potential at visit 2 
- 
Baseline low-dose non-iv contrast renal CT at visit 3 
- 
Re-assessment of blood sodium and potassium within one month after visit 3 if required (see 
section 9.3.3) 
- 
Telephone call at visit 4 for patients in routine follow-up for past kidney stone disease 
- 
3-monthly telephone calls in between on-site visits and telephone call at 30 days after end of 
treatment 
- 
Administration of IMP 
 
All other procedures are part of the routine assessments in kidney stone patients. 
10. SAFETY  
During the entire duration of the study, all SAEs are collected, fully investigated and documented in 
source documents and eCRF. Study duration encompassed the time from when the participant signs 
the informed consent until the last protocol-specific procedure has been completed, including a safety 
follow-up period of 30 days. 
Non-serious AEs are not collected with the exception of AEs of special interest (see section 9.2.4.2) 
occurring from the time point of randomization until the end of treatment visit.  
10.1 Definition and assessment of (serious) adverse events and other safety related 
events 
An adverse event (AE) is any untoward medical occurrence in a patient or a clinical investigation 
participant who administered a pharmaceutical product and which does not necessarily have a causal 
relationship with the study procedure. An AE can therefore be any unfavourable and unintended sign 
(including an abnormal laboratory finding), symptom, or disease temporally associated with the use of 
a medicinal (investigational) product, whether or not related to the medicinal (investigational) product. 
ICH E6 1.2 

 
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The Sponsor-Investigator will re-evaluate the SAE and return the form to the site. 
SAEs resulting in death will be reported to the coordinating and, if applicable, to the local Ethics 
Committee within 7 days. 
 
Non-serious Events that require discontinuation of IMP 
Non-serious events that require discontinuation of IMP (including laboratory abnormalities – see 
section 7.4.1) should be reported to the Sponsor-Investigator within 3 days. 
 
Reporting of SUSARs 
A SUSAR needs to be reported to the local Ethics Committee (local event via local Investigator) and to 
Swissmedic (via Sponsor-Investigator) within 7 days, if the event is fatal, or within 15 days (all other 
events). 
The Sponsor-Investigator must inform all Investigators participating in the clinical study of the 
occurrence of a SUSAR. All in the trial involved Ethics Committees will be informed about SUSARs in 
Switzerland via Sponsor-Investigator according to the same timelines. 
 
Reporting of Safety Signals 
All suspected new risks and relevant new aspects of known adverse reactions that require safety-
related measures, i.e. so called safety signals, must be reported to the Sponsor-Investigator within 24 
hours. The Sponsor-Investigator must report the safety signals within 7 days to the local Ethics 
Committee and to Swissmedic. The Sponsor-Investigator must immediately inform all participating 
Investigators about all safety signals. The other in the trial involved Ethics Committees will be informed 
about safety signals in Switzerland via the Sponsor-Investigator. 
 
Reporting and Handling of Pregnancies 
Pregnant participants must immediately discontinue IMP. Any pregnancy during the treatment phase 
of the study and within 30 days after discontinuation of IMP must be reported to the Sponsor-
Investigator within 24 hours. The course and outcome of the pregnancy will be followed up carefully 
and any abnormal outcome regarding the mother or the child should be documented and reported. 
 
Periodic reporting of safety 
An annual safety report will be prepared and submitted once a year to the local Ethics Committees 
and to Swissmedic by the Sponsor-Investigator. The annual safety report will contain information from 
all study sites. 
10.3 Follow up of (serious) adverse events 
Participants with any reported ongoing SAE at the last scheduled study contact will be followed until 
resolution of the event or a stabilized condition of the subject has been achieved or until the subject is 
lost to follow-up. 
Any new SAEs the Investigator gets aware of that occur after the last scheduled study contact and are 
determined by the Investigator to be reasonably associated with the use of the IMP, should be 
reported to the Sponsor-Investigator. The Investigator should follow potentially IMP-related SAEs 
identified after the last scheduled contact (and report any significant follow-up information to the 
Sponsor-Investigator) until the events are resolved or stabilized, or the subject is lost to follow-up. 
11. STATISTICAL METHODS  
11.1 Hypothesis 
The null hypothesis that there is no linear trend between dose and the survival function for the primary 
outcome (i.e. recurrence) will be tested against the alternative that there is a linear trend. 
11.2 Determination of Sample Size  
The sample size calculation was based on the primary objective i.e. to assess the dose-response 
relationship and the primary outcome i.e. recurrence with the following assumptions: 

 
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 
Uniform recruitment over 24 months with allocation ratio fixed at 1 across all arms. 
 
A maximum and minimum follow-up time of 36 and 24 months, respectively. 
 
A cumulative drop-out rate of 10% at 24 months after study start. 
 
Based on the available literature we assumed a risk of recurrence in the placebo group of 0.20 
and 0.45 at 12 and 36 months after study start, respectively. 
 
Hazard ratios for the 12.5, 25 and 50 mg HCTZ doses of 0.90, 0.65 and 0.50, respectively. These 
effects were based on the literature review presented in Table 3.1-1. 
 
Power was set to be at least 80% and alpha was fixed at a two-sided level of 0.05.  
 
An unweighted log-rank test for linear trend with local alternatives. 
 
Using the command artsurv in Stata we calculated that we will need to recruit 416 patients i.e. 104 in 
each arm. 
11.3 Statistical criteria of termination of trial  
Not applicable as no formal interim analysis is planned. 
11.4 Planned Analyses  
The statistical analysis of the trial will be done at CTU Bern by a statistician blinded to the allocation. 
This process is defined in standard operating procedures. After start of the trial but before recruitment 
ends, a statistical analysis plan will be written. The plan will determine all necessary data preparation 
steps (e.g. additional validations, generation of new variables), definitions (e.g. analysis sets), and 
statistical analyses (e.g. models, outputs such as tables and graphs).  
All statistical analyses will be presented as effect measure plus 95% confidence interval. A 
significance level of 5% will be used. 
11.4.1 Datasets to be analysed, analysis populations 
All analyses will be done on the intention-to-treat analysis set whereby all randomized patients will be 
analyzed in the allocated group regardless of any protocol violations such as cross-overs (which can 
only happen accidently in this trial) or early treatment discontinuations. 
11.4.2 Primary Analysis 
The primary outcome will be analyzed using a stratified log-rank test for linear trend with the hazard 
ratio as primary effect measure. The test addresses the primary objective of the trial i.e. test for any 
dose-response relationship. We will start with testing for a linear relationship but will also consider 
more complex relationships by using fractional polynomials. Kaplan-Meier curves will be used to 
present results on the primary outcome graphically. In case of a relevant number of multiple events 
within patients we will consider a model for recurrent events. 
Components of the primary outcome measure (clinical and radiological recurrence) will be analyzed 
similar to the primary analysis 
Continuous secondary outcomes (changes in urinary biochemistry) will be analyzed using linear 
regression. Comparisons between placebo and the three active trial arms will be considered 
exploratory as the trial is not powered to detect differences there. 
11.4.3 Secondary Analyses 
The following baseline characteristics were identified to potentially modify the expected treatment 
effect: 
- 
Baseline disease severity (Highest vs. lowest tertile in stone frequency prior to study entry)  
- 
Biochemical abnormalities (Hypercalciuria vs. no hypercalciuria) 
- 
Stone composition (pure CaOx vs. pure CaP vs. mixed CaOx/ CaP vs. mixed CaOx/ UA) 
These characteristics will be used for stratified analyses. All stratified analyses will be accompanied by 
tests for interaction. 
11.4.4 Interim analyses 
No formal interim analysis is planned. 
11.4.5 Safety analysis 
Safety endpoints to be analyzed include a descriptive summary of pre-specified AEs of special interest 
and vital signs. No formal statistical testing will be applied. 

 
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11.4.6 Deviation(s) from the original statistical plan  
Deviations from the statistical analysis plan will be stated and justified in the final analysis report.. 
11.5 Handling of missing data and drop-outs  
For the primary outcome, drop-outs will be censored at the last available visit. Missing data for 
continuous outcomes will be handled by multiple imputation. 
12. QUALITY ASSURANCE AND CONTROL  
12.1 Data handling and record keeping/ archiving  
The Investigators will maintain appropriate medical and research records for this trial, in compliance 
with ICH-GCP and regulatory and institutional requirements for the protection of confidentiality of 
subjects. The Principal Investigator, Sub-investigator, and Clinical Research Nurses or Coordinators 
will have access to the records. The Principal Investigators will permit authorized representatives of 
the Sponsor and regulatory agencies to examine clinical records for the purposes of quality assurance 
reviews, audits, and evaluation of the study safety and progress.  
12.1.1 Case Report Forms  
The CRF will be electronic. All data requested on the eCRF must be recorded and the recorded data 
should be consistent with the source documents or the discrepancies should be explained. The 
Investigator should ensure the accuracy, completeness, and timeliness of the data reported in the 
eCRF and all other required reports. Generally, the eCRF should be completed within one week of 
completion of a participant’s visit/ follow-up phone call. 
12.1.2 Specification of source documents  
Source documents must be available at the site to document the existence of the study participants 
and must include the original documents relating to the study, as well as the medical treatment and 
medical history of the participant. 
For all data captured in the eCRF, the location of the source should be documented on a list of source 
documents (source data location list), which will be stored in the investigator site file at each study site. 
If certain data are directly entered into the eCRF (and are thus considered as source data) this must 
be specified on the source data location list accordingly. 
Any change or correction to source data should be dated, initialed, and explained (if necessary) and 
should not obscure the original entry.  
12.1.3 Record keeping/ archiving  
All study data (written and electronic), including any images, must be retained for a period of at least 
10 years from the completion or premature termination of the trial. The Investigators should take 
measures to prevent accidental or premature destruction of these documents. 
12.2 Data management  
12.2.1 Data Management System  
The CRFs in this trial are implemented electronically using a dedicated electronic data capturing 
(EDC) system (secuTrial®). The EDC system is activated for the trial only after successfully passing a 
formal test procedure. All data entered in the eCRF are stored on a Linux server in a dedicated Oracle 
database. 
Responsibility for hosting the EDC system and the database lies with Inselspital Bern. 
12.2.2 Data security, access and back-up  
The server hosting the EDC system and the database is kept in a locked server-room. Only the 
system administrators have direct access to the server. A role concept with personal passwords (site 
investigator, statistician, monitor, administrator etc.) regulates permission for each user to use the 
system and database as he/ she requires. 

 
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All data entered into the eCRF are transferred to the database using Secure Sockets Layer (SSL) 
encryption. Each data point has attributes attached to it identifying the user who entered it with the 
exact time and date. Retrospective alterations of data in the database are recorded in an audit table. 
Time, table, data field and altered value, and the person are recorded (audit trail). A multi-level back-
up system is implemented.  
12.2.3 Analysis and archiving 
At interim (if applicable) and final analyses, data files will be extracted from the database into 
statistical packages to be analyzed. The status of the database at this time is recorded in special 
archive tables. 
The study database with all archive tables will be securely stored by Inselspital Bern. The sponsor 
also keeps the Trial Master File and interim and final reports both in electronic and in hard copy form 
for at least 10 years. 
12.2.4 Electronic and central data validation  
Data is checked by the EDC system for completeness and plausibility. Furthermore, selected data 
points are cross-checked for plausibility with previously entered data for that participant. In addition (if 
applicable), central data reviews will be performed on a regular basis to ensure completeness of the 
data collected and accuracy of the primary outcome data. 
12.3 Monitoring  
For quality control of the study conduct and data retrieval, all study sites will be visited on-site by 
appropriately trained and qualified Monitors. Any findings and comments will be documented in site 
visit reports and communicated to the local Investigator and to the Sponsor as applicable. 
Investigators at the participating study sites will support the Monitor in his/ her activities. Prior to study 
start (first participant enrolled) a plan detailing all monitoring-related procedures will be developed. 
All source data and relevant documents will be accessible to Monitors and questions of Monitors are 
answered during site visits.  
12.4 Audits and Inspections  
Source data/ documents must be available to audits by the Sponsor or designee or to inspections by 
health authorities. The CA (Swissmedic) or CEC may wish to conduct an inspection (during the study 
or after its completion). If an inspection is requested, the Investigator must inform the Sponsor 
immediately that this request has been made. The Investigators at the participating sites will support 
the inspectors in their activities and will answer questions from inspectors as needed. All involved 
parties must keep the participant data strictly confidential. 
12.5 Confidentiality, Data Protection  
The Investigator ensures anonymity of the patients; patients will not be identified by names in any 
documents. Signed informed consent forms and patient enrollment log will be kept strictly confidential 
to enable patient identification at the site. 
12.6 Storage of biological material and related health data  
All baseline and follow-up CTs for central analysis will be coded and uploaded into the picture 
archiving and communication system (PACS) of the Inselspital. A secure exchange platform will be 
used for file exchange. 
13. PUBLICATION AND DISSEMINATION POLICY  
The trial protocol will be published in an open access journal. Study results will be presented at 
national and international meetings and will be submitted for publication to high impact, peer reviewed 
journals. Upon completion of the analysis, trial results will be communicated to all participants. Public 
reporting will be done through patient organizations and via the communication Departments at the 
individual Universities and Hospitals.  

 
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Once results have been published, trial data will be accessible to external researchers and 
anonymized datasets corresponding to each publication will be made available. Investigators wishing 
to replicate the analyses or to do an individual patient meta-analysis may request the data from the 
steering committee. Access to data will be granted in an unbureaucratic way. 
14. FUNDING AND SUPPORT  
14.1 Funding 
This trial trial is financed by the Swiss National Science Foundation via the “Investigator-initiated 
clinical trials – IICT” grant # 33IC30_166785. 
14.2 Other Support 
The trial will also receive intramural support of the Bern University Hospital. 
15. INSURANCE  
Insurance will be provided by the Sponsor. A copy of the certificate is filed in each investigator site file 
and the trial master file. 
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profilaxis de la litiasis cálcica recidivante. Actas Urológicas Españolas. 2006;30:305-309. 
51. 
Brocks P, Dahl C, Wolf H, et al. Do thiazides prevent recurrent idiopathic renal calcium 
stones? The Lancet. 1981;318:124-125. 
52. 
Ahlstrand C, Sandvall K, Tiselius HG. Prophylactic treatment of calcium stone formers with 
hydrochlorothiazide and magnesium. Edsbruk, Sweden: Akademitryck. 1996. 
53. 
Scholz D, Schwille PO, Sigel A. Double-blind study with thiazide in recurrent calcium lithiasis. 
The Journal of urology. 1982;128:903-907. 
54. 
Reilly RF, Peixoto AJ, Desir GV. The evidence-based use of thiazide diuretics in hypertension 
and nephrolithiasis. Clin J Am Soc Nephrol. 2010;5:1893-1903. 
55. 
Curhan GC, Willett WC, Speizer FE, et al. Twenty-four–hour urine chemistries and the risk of 
kidney stones among women and men. Kidney international. 2001;59:2290-2298. 
56. 
Yendt ER, Cohanim M. Thiazides and calcium urolithiasis. Can Med Assoc J. 1978;118:755-
758. 
57. 
Bergsland KJ, Worcester EM, Coe FL. Role of proximal tubule in the hypocalciuric response 
to thiazide of patients with idiopathic hypercalciuria. Am J Physiol Renal Physiol. 
2013;305:F592-599. 
58. 
Martins MC, Meyers AM, Whalley NA, et al. Indapamide (Natrilix): the agent of choice in the 
treatment of recurrent renal calculi associated with idiopathic hypercalciuria. Br J Urol. 
1996;78:176-180. 
59. 
Vigen R, Weideman RA, Reilly RF. Thiazides diuretics in the treatment of nephrolithiasis: are 
we using them in an evidence-based fashion? Int Urol Nephrol. 2011;43:813-819. 
60. 
Flack JM, Cushman WC. Evidence for the efficacy of low-dose diuretic monotherapy. Am J 
Med. 1996;101:53S-60S. 
61. 
Huen SC, Goldfarb DS. Adverse metabolic side effects of thiazides: implications for patients 
with calcium nephrolithiasis. J Urol. 2007;177:1238-1243. 
62. 
Fink HA, Wilt TJ, Eidman KE, et al. Medical management to prevent recurrent nephrolithiasis 
in adults: a systematic review for an American College of Physicians Clinical Guideline. Ann 
Intern Med. 2013;158:535-543. 
63. 
Owens DK, Lohr KN, Atkins D, et al. AHRQ series paper 5: grading the strength of a body of 
evidence when comparing medical interventions--agency for healthcare research and quality 
and the effective health-care program. J Clin Epidemiol. 2010;63:513-523. 
64. 
Borghi L, Meschi T, Amato F, et al. Urinary volume, water and recurrences in idiopathic 
calcium nephrolithiasis: a 5-year randomized prospective study. J Urol. 1996;155:839-843. 
65. 
Borghi L, Schianchi T, Meschi T, et al. Comparison of two diets for the prevention of recurrent 
stones in idiopathic hypercalciuria. N Engl J Med. 2002;346:77-84. 
66. 
Curhan GC, Willett WC, Speizer FE, et al. Comparison of dietary calcium with supplemental 
calcium and other nutrients as factors affecting the risk for kidney stones in women. Ann 
Intern Med. 1997;126:497-504. 

 
NOSTONE Trial, Protocol Version 1, 30.08.2016 
 
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67. 
Glowacki LS, Beecroft ML, Cook RJ, et al. The natural history of asymptomatic urolithiasis. J 
Urol. 1992;147:319-321. 
68. 
Papadoukakis S, Stolzenburg J-U, Truss MC. Treatment strategies of ureteral stones. eau-
ebu update series. 2006;4:184-190. 
69. 
Kwon JK, Chang IH, Moon YT, et al. Usefulness of low-dose nonenhanced computed 
tomography with iterative reconstruction for evaluation of urolithiasis: diagnostic performance 
and agreement between the urologist and the radiologist. Urology. 2015 Mar;85(3):531-8.  
70. 
1990 Recommendations of the International Commission on Radiological Protection. 
Ann ICRP. 1991; 21:1-201. 
71. 
Knöpfle E, Hamm M, Wartenberg S, et al. CT in ureterolithiasis with a radiation dose equal to 
intravenous urography: results in 209 patients. Rofo. 2003;175:1667–1672. 
 
17. APPENDICES 
Not applicable. 

 
 
 
 
 
 
 
 
 
Last/final trial protocol 
Version 1.7 
November 28th, 2019 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
Page 1 of 46 
 
 
Clinical Study Protocol 
Randomized double-blind placebo-controlled trial assessing the efficacy of 
standard and low dose hydrochlorothiazide treatment 
in the prevention of recurrent nephrolithiasis 
 
NOSTONE TRIAL 
 
 
Study Type: 
Clinical trial with Investigational Medicinal Product (IMP)  
 
Study Categorisation: 
 
Risk category B 
 
Study Registration: 
 
ClinicalTrials.gov, Swiss National Clinical Trials Portal (SNCTP) 
 
Study Identifier: 
Swiss National Science Foundation # 33IC30_166785/ 1 
 
Sponsor-Investigator: 
 
Prof. Dr. med. Daniel Fuster 
Leitender Arzt 
Division of Nephrology and Hypertension  
Bern University Hospital, Bern, Switzerland 
Phone: +41 (0)31 632 31 44 
Email: daniel.fuster@insel.ch 
 
Investigational Product: 
 
Hydrochlorothiazide 
 
Protocol Version and Date: 
 
Version 1.7, 28.11.2019 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CONFIDENTIAL 
The information contained in this document is confidential and the property of the sponsor. The 
information may not - in full or in part - be transmitted, reproduced, published, or disclosed to others 
than the applicable Competent Ethics Committee(s) and Regulatory Authority(ies) without prior written 
authorization from the sponsor except to the extent necessary to obtain informed consent from those 
who will participate in the study. 
 
 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
Page 3 of 46 
 
 
Local Principal Investigator at study site: 
 
I have read and understood this trial protocol and agree to conduct the trial as set out in this study 
protocol, the current version of the World Medical Association Declaration of Helsinki, ICH-GCP 
guidelines and the local legally applicable requirements. 
 
Site: 
 
Principal Investigator: 
 
 
 
Place/ Date 
 
Signature 
 
 
 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
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Table of Contents 
 
STUDY SYNOPSIS .............................................................................................................................. 6 
STUDY SUMMARY IN LOCAL LANGUAGE ....................................................................................... 9 
ABBREVIATIONS .............................................................................................................................. 10 
STUDY SCHEDULE 1 – PARTICIPANTS RECRUITED IN THE FIRST 12 MONTHS OF THE 
RECRUITMENT PERIOD ................................................................................................................... 11 
STUDY SCHEDULE 2 – PARTICIPANTS RECRUITED ≥ 12 MONTHS AFTER RECRUITMENT 
START ................................................................................................................................................ 13 
1. 
STUDY ADMINISTRATIVE STRUCTURE .................................................................................. 15 
1.1 
Sponsor-Investigator ................................................................................................................. 15 
1.2 
Principal Study Investigator ...................................................................................................... 15 
1.3 
Statistician ("Biostatistician") ..................................................................................................... 15 
1.4 
Laboratory ................................................................................................................................ 15 
1.5 
Monitoring institution ................................................................................................................. 15 
1.6 
Data Safety Monitoring Committee ........................................................................................... 15 
1.7 
Any other relevant Committee, Person, Organisation, Institution .............................................. 15 
2. 
ETHICAL AND REGULATORY ASPECTS ................................................................................. 16 
2.1 
Study registration ...................................................................................................................... 16 
2.2 
Categorisation of study ............................................................................................................. 16 
2.3 
Competent Ethics Committee (CEC) ........................................................................................ 16 
2.4 
Competent Authorities (CA) ...................................................................................................... 16 
2.5 
Ethical Conduct of the Study ..................................................................................................... 16 
2.6 
Declaration of interest ............................................................................................................... 16 
2.7 
Patient Information and Informed Consent ............................................................................... 16 
2.8 
Participant privacy and confidentiality ....................................................................................... 17 
2.9 
Early termination of the study ................................................................................................... 17 
2.10 Protocol amendments ............................................................................................................... 17 
3. 
BACKGROUND AND RATIONALE ............................................................................................ 17 
3.1 
Background and Rationale ....................................................................................................... 17 
3.2 
Investigational Product (treatment, device) and Indication ........................................................ 22 
3.3 
Preclinical Evidence .................................................................................................................. 23 
3.4 
Clinical Evidence to Date .......................................................................................................... 23 
3.5 
Dose Rationale: Rationale for the intended purpose in study ................................................... 23 
3.6 
Explanation for choice of comparator (or placebo) .................................................................... 23 
3.7 
Risks/ Benefits .......................................................................................................................... 24 
3.8 
Justification of choice of study population ................................................................................. 24 
4. 
STUDY OBJECTIVES ................................................................................................................. 24 
4.1 
Overall Objective ...................................................................................................................... 24 
4.2 
Primary Objective ..................................................................................................................... 25 
4.3 
Secondary Objectives ............................................................................................................... 25 
4.4 
Safety Objectives ...................................................................................................................... 25 
5. 
STUDY OUTCOMES ................................................................................................................... 25 
5.1 
Primary Outcome ...................................................................................................................... 25 
5.2 
Secondary Outcomes ............................................................................................................... 25 
5.3 
Other Outcomes of Interest....................................................................................................... 26 
5.4 
Safety Outcomes ...................................................................................................................... 26 
6. 
STUDY DESIGN .......................................................................................................................... 26 
6.1 
General study design and justification of design ....................................................................... 26 
6.2 
Methods of minimizing bias ....................................................................................................... 27 
6.3 
Unblinding Procedures (Code break) ........................................................................................ 27 
7. 
STUDY POPULATION ................................................................................................................ 28 
7.1 
Eligibility criteria ........................................................................................................................ 28 
7.2 
Recruitment and screening ....................................................................................................... 29 
7.3 
Assignment to study groups ...................................................................................................... 29 
7.4 
Criteria for withdrawal/ discontinuation of participants .............................................................. 29 
8. 
STUDY INTERVENTION ............................................................................................................. 30 
8.1 
Identity of Investigational Products ........................................................................................... 30 
8.2 
Administration of experimental and control interventions .......................................................... 31 
8.3 
Dose modifications ................................................................................................................... 31 

 
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8.4 
Compliance with study intervention........................................................................................... 31 
8.5 
Data Collection and Follow-up for withdrawn participants ......................................................... 32 
8.6 
Trial-specific preventive measures ........................................................................................... 32 
8.7 
Concomitant Interventions (treatments) .................................................................................... 33 
8.8 
Study Drug Accountability ......................................................................................................... 33 
8.9 
Return or Destruction of Study Drug/ Medical Device ............................................................... 33 
9. 
STUDY ASSESSMENTS ............................................................................................................ 33 
9.1 
Study flow chart(s)/ table of study procedures and assessments .............................................. 33 
9.2 
Assessments of outcomes ........................................................................................................ 33 
9.3 
Procedures at each visit ........................................................................................................... 34 
10. SAFETY ...................................................................................................................................... 38 
10.1 Definition and assessment of (serious) adverse events and other safety related events .......... 38 
10.2 Reporting of serious adverse events (SAE) and other safety-related events ............................ 39 
10.3 Follow up of (serious) adverse events ...................................................................................... 40 
11. STATISTICAL METHODS .......................................................................................................... 40 
11.1 Hypothesis ................................................................................................................................ 40 
11.2 Determination of Sample Size .................................................................................................. 40 
11.3 Statistical criteria of termination of trial ..................................................................................... 40 
11.4 Planned Analyses ..................................................................................................................... 40 
11.5 Handling of missing data and drop-outs .................................................................................... 41 
12. QUALITY ASSURANCE AND CONTROL .................................................................................. 41 
12.1 Data handling and record keeping/ archiving ............................................................................ 41 
12.2 Data management .................................................................................................................... 42 
12.3 Monitoring ................................................................................................................................. 42 
12.4 Audits and Inspections .............................................................................................................. 43 
12.5 Confidentiality, Data Protection ................................................................................................. 43 
12.6 Storage of biological material and related health data .............................................................. 43 
13. PUBLICATION AND DISSEMINATION POLICY ........................................................................ 43 
14. FUNDING AND SUPPORT ......................................................................................................... 43 
14.1 Funding .................................................................................................................................... 43 
14.2 Other Support ........................................................................................................................... 43 
15. INSURANCE ............................................................................................................................... 44 
16. REFERENCES ............................................................................................................................ 44 
17. APPENDICES ............................................................................................................................. 46 
 
 
 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
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STUDY SYNOPSIS 
 Sponsor/ Sponsor-
Investigator: 
Inselspital Bern (Sponsor) represented by Prof. Dr. med. Daniel Fuster 
(Sponsor-Investigator) 
Study Title: 
Randomized double-blind placebo-controlled trial assessing the efficacy 
of standard and low dose hydrochlorothiazide treatment in the prevention 
of recurrent nephrolithiasis 
Short Title/ Study ID: 
NOSTONE Trial 
Protocol Version and 
Date: 
Version 1.7, 28.11.2019 
Trial registration: 
ClinicalTrials.gov, Swiss national clinical trials portal (SNCTP) 
Study category and 
Rationale: 
Risk category B 
Clinical trial with an IMP authorized in Switzerland that is not used in 
accordance with its prescribing information.  
Clinical Phase: 
Therapeutic use 
Background and 
Rationale: 
Nephrolithiasis is a global healthcare problem with a current lifetime risk 
of 18.8% in men and 9.4% in women. Without specific treatment, 5- and 
20-year recurrence rates are 40% and 75%, respectively. Given the high 
cost of medical treatments and surgical interventions as well as the 
morbidity related to symptomatic stone disease, medical prophylaxis for 
stone recurrence is an attractive approach.  
About 80–90% of stones are composed of calcium oxalate with various 
admixtures of calcium phosphate. Increased excretion of calcium in the 
urine, hypercalciuria, is the most common metabolic abnormality 
encountered in patients with recurrent nephrolithiasis. Thiazide diuretics 
have been the cornerstone of pharmacologic metaphylaxis for more than 
40 years. The effect of thiazides to reduce the risk of stone recurrence 
has been attributed to their ability to decrease urinary calcium excretion. 
However, other factors, such as reduction of urinary pH and urinary 
oxalate excretion, probably contribute to this effect. Efficacy of thiazides 
on recurrence prevention of calcareous nephrolithiasis was tested in 11 
randomized controlled trials (RCTs). With the exception of two trials, 
thiazides significantly reduced stone recurrence. Most of these trials are 
from the 1980’s and 90’s and the cumulative number of patients studied 
is remarkably low for such a prevalent disease. Our systematic review of 
these RCTs revealed major methodological deficiencies in all trials, 
including: lack of double-blinding and intention-to-treat analysis, unclear 
allocation concealment, lack of adverse event and drop out reporting and 
unknown baseline risk of disease severity. Furthermore, high doses of 
thiazides were employed in all trials, in the case of the best studied 
thiazide, hydrochlorothiazide (HCTZ), up to 100 mg daily. At such high 
doses, side effects occur frequently. Nowadays, thiazides are widely 
used in the treatment of recurrent nephrolithiasis and arterial 
hypertension, but at significantly lower doses. In the case of recurrent 
nephrolithiasis, however, this practice is not supported by randomized 
evidence and consequently, we do not know whether the currently 
employed low dose thiazide regimens are effective in reducing the risk 
for stone recurrence. 
Thus, evidence for benefits and harms of thiazide diuretics in the 
prevention of calcium-containing kidney stones in general remains 
unclear. In addition, the efficacy of the currently employed low dose 
thiazide regimens to prevent stone recurrence is not known. 
Objective(s): 
We plan to assess the efficacy of standard and low dose HCTZ 
treatment in the recurrence prevention of calcium-containing kidney 
stones. More specifically, we aim to assess the dose-response 
relationship for three different dosages of HCTZ. 

 
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Outcome(s): 
Primary: relationship of the incidence of stone recurrences (a composite 
of symptomatic or radiologic recurrence) during study treatment and 
dose group.  
Secondary: individual components of the composite primary outcome, 
changes in urinary biochemistry elicited by HCTZ treatment and impact 
of baseline disease severity, biochemical abnormalities and stone 
composition on treatment response. 
Study design: 
Multicenter, randomized, placebo-controlled, double-blind, parallel-group 
trial.  
Inclusion/ Exclusion 
criteria: 
Main inclusion criteria:  
 
Informed Consent as documented by signature 
 
Age 18 years or older 
 
Recurrent kidney stone disease (≥ 2 stone events within the last 10 
calendar years prior to randomization) 
 
Any past kidney stone containing 50% or more of calcium oxalate, 
calcium phosphate or a mixture of both 
 
Main exclusion criteria: 
 
Subjects with secondary causes of recurrent calcareous 
nephrolithiasis 
 
Subjects with the following medications: Thiazide or loop diuretics, 
carbonic anhydrase inhibitors, xanthine oxidase inhibitors, alkali, 
active Vitamin D, calcium supplementation, bisphosphonates, 
denusomab, teriparatide, glucocorticoids 
 
Known allergy to the study drug 
Measurements and 
procedures: 
An overview on the study measurements and procedures is provided in 
the study schedules. 
The main measurements and procedures performed are the following:  
Screening: medical history, vital signs, clinical laboratory tests 
Efficacy: symptomatic stone recurrence, low-dose renal-limited 
computed tomography for radiologic stone recurrence. 
Safety: vital signs, complete physical examination, SAEs and selected 
AEs, clinical laboratory tests. 
Study Product/ 
Intervention:  
HCTZ 12.5 mg, 25 mg or 50 mg once daily per os for 24 or 36 months. In 
addition, all patients in HCTZ treatment arms will receive state-of-the-art 
non-pharmacologic recommendations for stone prevention according to 
current guidelines. 
Control Intervention 
(if applicable): 
Placebo once daily per os for 24 to 36 months. In addition, all patients in 
the placebo arm will receive state-of-the-art non-pharmacologic 
recommendations for stone prevention according to current guidelines. 
Number of 
Participants with 
Rationale: 
416 patients in total, 104 patients per study arm. 
Study Duration: 
03/2017 – 08/2021 
Study Schedule: 
Month/Year of First-Participant-In: 03/2017 
Month/Year of Last-Participant-Out: 08/2021 
Investigator(s): 
Principal Study Investigator: 
Prof. Dr. med. Daniel Fuster, Leitender Arzt 
Division of Nephrology, Hypertension and Clinical Pharmacology, Bern 
University Hospital 
Freiburgstrasse 11, 3010 Bern, Switzerland 
Email: daniel.fuster@insel.ch 
Phone: +41 (0)31 632 31 44 
Study Centre(s): 
12 sites in Switzerland including University Hospitals of Basel, Bern, 
Geneva, Lausanne and Zurich as well as Cantonal Hospitals of Aarau, 
Bellinzona, Chur, Lugano, Sion, Lucerne and St. Gallen. 

 
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Statistical 
Considerations: 
Sample size: Calculation was based on the primary objective i.e. to 
assess the dose-response relationship and the primary outcome i.e. 
recurrence with the following assumptions: 
 
Uniform recruitment over 24 months with allocation ratio fixed at 1 
across all arms. 
 
A maximum and minimum follow-up time of 36 and 24 months, 
respectively. 
 
Cumulative drop-out rate of 10% at 24 months after study start. 
 
Risk of recurrence in the placebo group of 0.20 and 0.45 at 12 and 
36 months after study start, respectively. 
 
Hazard ratios for the 12.5, 25 and 50 mg HCTZ doses of 0.90, 0.65 
and 0.50, respectively.  
 
Power was set to be at least 80% and alpha was fixed at a two-sided 
level of 0.05. 
 
An unweighted log-rank test for linear trend with local alternatives. 
 
Primary efficacy analysis: On the intention-to-treat analysis set by a 
stratified log-rank test for linear trend with the hazard ratio as primary 
effect measure. The test addresses the primary objective of the trial i.e. 
test for any dose-response relationship. Comparisons between placebo 
and the three active trial arms will be considered exploratory as the trial 
is not powered to detect differences there. Missing data will be handled 
by multiple imputation. All statistical analyses will be presented as effect 
measure plus 95% confidence interval. 
Secondary efficacy analysis: Analysis will follow principles as described 
for primary efficacy analysis. Continuous outcomes (laboratory values) 
will be analyzed using linear regression. 
GCP Statement: 
This study will be conducted in compliance with the protocol, the current 
version of the Declaration of Helsinki, the ICH-GCP as well as all 
national legal and regulatory requirements.  
 
 

 
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STUDY SUMMARY IN LOCAL LANGUAGE  
Titel des Forschungsprojektes: 
Randomisierte plazebokontrollierte Doppelblindstudie über die Wirksamkeit von normal- und 
tiefdosiertem Hydrochlorothiazid zur Vorbeugung von Rückfällen kalziumhaltiger Nierensteine: die 
NOSTONE-Studie 
 
Lead:  
In dieser klinischen Studie wird die Wirksamkeit des Medikaments Hydrochlorothiazid zur Vorbeugung 
von Rückfällen kalziumhaltiger Nierensteine getestet. 
 
Inhalt und Ziele des Forschungsprojektes:  
Nierensteine sind ein weltweites Gesundheitsproblem, etwa 10% aller Menschen sind mindestens 
einmal im Leben davon betroffen. Nierensteine sind äusserst schmerzhaft, treten wiederholt auf und 
verursachen hohe direkte und indirekte Kosten. Eine effektive und kostengünstige Vorbeugung gegen 
Rückfälle von Nierensteinen ist deshalb äusserst wünschenswert.  
Etwa 80-90% aller Nierensteine enthalten Kalzium und eine vermehrte Ausscheidung von Kalzium im 
Urin ist die häufigste Stoffwechselstörung bei Patienten mit Nierensteinen. Thiazide reduzieren die 
Kalziumausscheidung im Urin und werden daher seit Jahrzehnten zur Vorbeugung von Rückfällen 
kalziumhaltiger Nierensteine eingesetzt. Deren Wirksamkeit wurde in den letzten 30 Jahren in mehreren 
Studien getestet. Leider war die Durchführung dieser Studien mangelhaft, die Gesamtzahl der 
untersuchten Patienten klein, und es wurden hohe Medikamentendosen getestet, welche häufig 
Nebenwirkungen verursachen. Zur Zeit ist daher der Stellenwert der Thiazide in der Behandlung von 
Patienten mit Nierensteinen unklar. Ziel dieser Studie ist es, die Wirksamkeit von normal- und 
tiefdosiertem Hydrochlorothiazid zur Vorbeugung von Rückfällen kalziumhaltiger Nierensteine zu testen. 
 
Wissenschaftlicher und gesellschaftlicher Kontext des Forschungsprojekts:  
Das Nierensteinleiden gehört zu den häufigsten menschlichen Erkrankungen. Mit dieser klinischen 
Studie soll eine grosse Wissenslücke in der Nierensteinbehandlung geschlossen werden. Die Resultate 
dieser Studie werden die Behandlung von Nierensteinpatienten weltweit beeinflussen. 
 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
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ABBREVIATIONS 
AE 
Adverse Event  
BMI 
Body Mass Index 
CA 
Competent Authority (Swissmedic) 
CEC 
Competent Ethics Committee 
CI 
Confidence Interval 
CRF 
Case Report Form  
eCRF 
Electronic Case Report Form  
CT 
Computed Tomography 
CTCAE 
Common Terminology Criteria for Adverse Events 
EOS 
End of Study 
EOT 
End of Treament 
GCP 
Good Clinical Practice  
HCTZ 
Hydrochlorothiazide 
IMP 
Investigational Medicinal Product 
IVU 
Intravenous Urography 
NIH 
National Institute of Health 
RCT 
Randomized Controlled Trial 
SAE 
Serious Adverse Event 
SNCTP 
Swiss National Clinical Trials Portal 
SUSAR 
Suspected Unexpected Serious Adverse Reaction  
 
 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
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1. STUDY ADMINISTRATIVE STRUCTURE  
1.1 
Sponsor-Investigator 
Prof. Dr. med. Daniel Fuster, Leitender Arzt 
Division of Nephrology and Hypertension, Bern University Hospital 
Freiburgstrasse 11, 3010 Bern, Switzerland 
Email: daniel.fuster@insel.ch 
Phone: +41 (0)31 632 31 44 
1.2 
Principal Study Investigator 
Prof. Dr. med. Daniel Fuster, Leitender Arzt 
Division of Nephrology and Hypertension, Bern University Hospital 
Freiburgstrasse 11, 3010 Bern, Switzerland 
 
Email: daniel.fuster@insel.ch 
Phone: +41 (0)31 632 31 44 
1.3 
Statistician ("Biostatistician")  
PD Dr. med. Sven Trelle 
CTU Bern, Department of Clinical Research, University of Bern 
Mittelstrasse 43, 3012 Bern, Switzerland 
Email: sven.trelle@ctu.unibe.ch 
Phone: +41 (0)31 631 35 04 
1.4 
Laboratory 
The address of the central laboratory is documented elsewhere. 
1.5 
Monitoring institution 
CTU Bern, Department of Clinical Research, University of Bern 
Mittelstrasse 43, 3012 Bern, Switzerland 
Phone: +41 (0)31 631 33 72 
1.6 
Data Safety Monitoring Committee  
Not applicable. 
1.7 
Any other relevant Committee, Person, Organisation, Institution  
1.7.1 
Study Steering Committee 
The study steering committee will be responsible for the overall supervision of the trial and will regularly 
meet to discuss scientific and logistic aspects of the trial. Information on the composition of the 
committee is available in a separate document. 
 
 

 
NOSTONE Trial, Protocol Version 1.7, 28.11.2019 
 
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2. ETHICAL AND REGULATORY ASPECTS  
Before the study will be conducted, the protocol, the proposed patient information and consent form, as 
well as other study-specific documents shall be submitted to a properly constituted Competent Ethics 
Committee (CEC) and competent authority (CA, Swissmedic) in agreement with local legal requirements, 
for formal approval. Any amendment to the protocol must as well be approved (if legally required) by 
these institutions. 
The decision of the CEC and CA concerning the conduct of the study will be made in writing to the 
Sponsor-Investigator before commencement of this study. The clinical study can only begin once 
approval from all required authorities has been received. Any additional requirements imposed by the 
authorities shall be implemented. 
2.1 
Study registration  
The study will be registered in the Clinical Trials Registry Platform of the National Institute of Health 
(NIH) – ClinicalTrials.gov. In addition, the trial will be registered in the Swiss National Clinical Trials 
Portal (SNCTP). 
2.2 
Categorisation of study  
Risk category B. Clinical trial with an investigational medicinal product (IMP) authorized in Switzerland 
that is not used in accordance with its prescribing information.  
2.3 
Competent Ethics Committee (CEC)  
Responsible investigators at each study site will ensure that approval from the appropriate constituted 
CEC is sought for the clinical study. Yearly intermediary reports (annual safety reports) will be forwarded 
to the CEC. All unanticipated problems involving risks to humans will be reported to the CEC within 7 
days. No changes will be made to the protocol without prior Sponsor and, in case of substantial 
amendments, CEC approval, except where necessary to eliminate apparent immediate hazards to study 
participants. Amendments will be reported according to section 2.10. 
Premature study end or interruption of the study will be reported to the CEC within 15 days. The regular 
end of the study will be reported to the CEC within 90 days, the final study report shall be submitted 
within one year after study end. 
2.4 
Competent Authorities (CA)  
The Sponsor-Investigator will obtain approval from the CA (Swissmedic) before the start of the clinical 
trial. Yearly intermediary reports (annual safety reports) will be forwarded to the CA. Premature study 
end or interruption of the study will be reported to the CA within 15 days. The regular end of the study 
will be reported to the CA within 90 days, the final study report shall be submitted within one year after 
study end. Amendments are reported according to section 2.10. Non-substantial amendments shall be 
reported as soon as possible. 
2.5 
Ethical Conduct of the Study  
The study will be carried out in accordance to the protocol and with principles enunciated in the current 
version of the Declaration of Helsinki, the guidelines of Good Clinical Practice (GCP) issued by ICH, the 
Swiss Law and Swiss regulatory authority’s requirements. The CEC and regulatory authorities will 
receive annual safety and interim reports and be informed about study stop/ end in agreement with local 
requirements.  
2.6 
Declaration of interest  
There are no conflicts of interest. 
2.7 
Patient Information and Informed Consent 
All participants included in the trial are adults with recurrent kidney stone disease. No vulnerable 
individuals will be included in the trial. The participation in the trial is voluntary. The investigators will 
explain to each participant the nature of the study, its purpose, the procedures involved, the expected 
duration, the potential risks and benefits and any discomfort it may entail. Each participant will be 
informed that the participation in the study is voluntary and that he/she may withdraw from the study at 

 
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any time and that withdrawal of consent will not affect his/her subsequent medical assistance and 
treatment. The participant will be informed that his/her medical records may be examined by authorised 
individuals other than their treating physician. All study participants will be provided with a participant 
information sheet and a consent form describing the study and providing sufficient information for the 
participant to make an informed decision about their participation in the study. Participants willing to 
participate will sign and date the informed consent form. The consent form will also be signed and dated 
by the investigator (or his designee) and it will be retained as part of the study records. A copy of the 
signed document will be given to the participants. Only after obtaining formal consent with the approved 
consent form, participants will be submitted to any study procedure. No compensation is foreseen and 
informed consent for general and further use of data and/ or biological samples will not be sought. 
Patients must sign an additional patient informed consent for the NOSTONE biobank. 
2.8 
Participant privacy and confidentiality  
The investigator affirms and upholds the principle of the participant's right to privacy and that they shall 
comply with applicable privacy laws. Especially, anonymity of the participants shall be guaranteed when 
presenting the data at scientific meetings or publishing them in scientific journals. Individual subject 
medical information obtained as a result of this study is considered confidential and disclosure to third 
parties is prohibited. Subject confidentiality will be further ensured by utilising subject identification code 
numbers to correspond to treatment data in the computer files. For data verification purposes, 
authorised representatives of the Sponsor (-Investigator), the CA, or CEC may require direct access to 
parts of the medical records relevant to the study, including participants’ medical history. 
2.9 
Early termination of the study  
The Steering Committee may terminate the study prematurely according to certain circumstances, for 
example: 
- 
ethical concerns, 
- 
financial issues, 
- 
insufficient participant recruitment, 
- 
when the safety of the participants is doubtful or at risk, respectively, 
- 
alterations in accepted clinical practice that make the continuation of a clinical trial unwise,  
- 
early evidence of benefit or harm of the experimental intervention,  
- 
or any other reason that would prevent the project execution according to the research plan. 
 
Premature study end or interruption of the study will be reported to the CEC and CA within 15 days. 
2.10 Protocol amendments 
The Steering Committee will decide on protocol amendments. Any investigator, CEC or CA will be able 
to provide suggestions for a protocol amendment. Important protocol modifications will be 
communicated by the Sponsor-Investigator to relevant parties (CEC, CA, trial participants, trial registries 
and the Swiss National Science Foundation). 
Substantial amendments will only be implemented after approval of the CEC and CA, respectively. 
Under emergency circumstances, deviations from the protocol to protect the rights, safety and well-
being of human subjects may proceed without prior approval of the sponsor and the CEC/ CA. Such 
deviations shall be documented and reported to the sponsor and the CEC/ CA as soon as possible. All 
non-substantial amendments are communicated to the CA as soon as possible if applicable and to the 
CEC within the Annual Safety Report (ASR). 
3. BACKGROUND AND RATIONALE  
3.1 
Background and Rationale  
Introduction: 
Nephrolithiasis is a worldwide healthcare problem with a current lifetime risk of ~18.8% in men and 
~9.4% in women in Western civilizations [1]. Incidence and prevalence of renal stone disease are 
increasing globally, irrespective of age, sex and race [1, 2]. Without a specific treatment, 5- and 20-year 

 
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recurrence rates are ~40% and ~75%, respectively [3, 4]. In the United States, hospitalizations, surgery 
and lost work time associated with kidney stones cost more than 5 billion US Dollars annually [5]. Thus, 
given the high cost and the morbidity related to recurrent kidney stone disease, medical prophylaxis 
seems to be an attractive approach [6, 7]. Indeed, apart from its benefits to patients in terms of reduced 
morbidity and risk from procedures, medical prevention of nephrolithiasis is clearly cost effective [8].  
Although various inherited and systemic diseases are associated with kidney stones, most stones are 
idiopathic [3]. Despite this, nephrolithiasis needs to be considered as a systemic disease. Chronic kidney 
disease (CKD), arterial hypertension, obesity, diabetes mellitus and low bone mass are much more 
prevalent in stone formers than in non-stone formers and contribute significantly to stone-related 
morbidity and mortality [9-15]. It is, however, currently unclear if stone disease is a cause of this co-
morbidity or if it is a consequence of the same underlying conditions that lead to these disorders and 
renal stone disease. 
80-90% of stones are composed of calcium oxalate, calcium phosphate or a mixture of both [16, 17]. 
Increased excretion of calcium in the urine, hypercalciuria, is the most frequent metabolic abnormality 
encountered in patients with recurrent idiopathic nephrolithiasis [17, 18]. Depending on the stone 
subtype, hypercalciuria is present in up to 87% of patients with calcium-containing kidney stones [17]. 
Other urinary factors frequently encountered in recurrent calcareous stone formers that contribute to the 
development of stones are hypocitraturia, hyperoxaluria, hyperuricosuria and low urinary volume [19]. 
Supersaturation of urinary calcium oxalate and calcium phosphate, expressed as the ratio of 
concentration to its solubility, is the driving force for stone formation. At a supersaturation < 1, crystals 
dissolve, at a supersaturation > 1, crystals form. Hypercalciuria increases supersaturation both for 
calcium oxalate and calcium phosphate and thus increases the risk for both calcium oxalate and calcium 
phosphate stones [3]. Urinary supersaturations calculated from ambulatory 24 hour urine collections are 
highly correlated with the type of kidney stones encountered in the individual stone former, with notable 
rare exceptions in patients with very high or very low urinary volumes [20]. The hypercalciuria 
encountered in recurrent stone formers is often familial and strongly influenced by diet but in most cases 
of unknown origin and hence designated “idiopathic” [3]. Gut absorption of calcium is enhanced in 
idiopathic hypercalciuria, but serum calcium remains typically normal because intestinally absorbed 
calcium is promptly excreted by the kidneys [21]. Despite intestinal calcium hyperabsorption, patients 
with idiopathic hypercalciuria are often in negative calcium balance because of excessive renal calcium 
losses, especially under a low calcium diet [19, 22]. The source of calcium in these circumstances is the 
skeleton, the largest repository of calcium in the body [19]. Not surprising therefore, low bone mass is a 
frequent finding in normo- and especially hypercalciuric stone formers [9]. At the moment, thiazide 
diuretics are the only drugs known to reduce urinary calcium excretion. This peculiar property is 
employed in the prevention of recurrent calcareous nephrolithiasis but also in the prevention of bone 
loss in patients with recurrent nephrolithiasis and/ or arterial hypertension [9, 23]. Observational data 
and evidence from prospective trials indicate that chronic thiazide therapy preserves bone mineral 
density and reduces fracture risk [24-27]. 
Clinical work-up of patients with recurrent nephrolithiasis includes a detailed history and physical 
examination as well as blood and urine analysis to detect potential causes of stones but also possible 
associated conditions [23]. Spot urine analysis is performed to search for crystalluria and rule out 
infection [23]. Paramount for the metabolic work-up are 24 h urine collections, which are typically 
performed twice, since mineral excretions have considerable day-to-day variations [23, 28, 29]. 
Metabolic work-up for stone disease is done at least 3 months after a symptomatic stone event in 
patients which have resumed their usual diet and activity [30]. All passed stones need to be analyzed 
for classification purposes but also to detect possible treatment related conversions of one stone type 
to another (e.g. calcium oxalate to calcium phosphate by citrate-induced urinary alkalinization) [3, 31]. 
Computed tomography (CT) without the use of contrast material is the most sensitive method to detect 
renal and ureteral stones and should, according to current guidelines, be preferred to plain abdominal 
X-ray imaging (KUB radiography) or intravenous urography (IVU) in the case of a symptomatic stone 
event [23, 31-33]. Modern low-dose CT protocols cause greatly reduced radiation exposure while 
preserving a high sensitivity of 96.6% and specificity of 94.9% [34]. Current radiation exposure of low 
dose CT protocols for the detection of urolithiasis is in the range of 0.97-1.9 mSV and thus similar to 
KUB radiography (0.5-1 mSv) but significantly lower than IVU (1.3 -3.5 mSv) or regular dose CT (4.5-5 
mSv) [23, 35, 36]. 
Follow-up studies are necessary in patients taking preventive measures for stone recurrence [23, 37]. 
American and European guidelines recommend a first follow-up 24 hour urine collection 8-12 weeks 
after initiation of therapy to adjust drug dosage [23, 31]. Also, periodic blood testing in patients on 
pharmacological treatment to assess for adverse events (AEs) are recommended [31]. In the case of 
thiazide diuretics, a repeat blood draw with serum electrolytes is typically done within the first few weeks 

 
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of treatment initiation to rule out electrolyte abnormalities, especially hypokalemia. In the case of the 
latter, oral potassium supplementation or a potassium-sparing diuretic like spironolactone or amiloride 
can be additionally prescribed [31]. Once urinary parameters have been normalized and blood 
parameters are stable, yearly blood and urine analysis is recommended [23, 31]. In addition to metabolic 
studies, periodic follow-up imaging studies, preferably with low dose CT, are equally recommended to 
assess for stone growth or new stone formation [23, 31]. A one-year imaging interval is currently 
recommended for stable patients on medical stone prevention [23, 31].  
 
Current knowledge on the efficacy of thiazides in recurrent nephrolithiasis: 
The first thiazide diuretic chlorothiazide was synthesized in 1957 by Sprague and Novello [38]. In 1959, 
Lamberg and Kuhlbäck reported the observation that the thiazides chlorothiazide and 
hydrochlorothiazide (HCTZ) reduce urinary calcium excretion [39]. Soon thereafter, Lichtwitz and 
colleagues suggested that this peculiar property might be exploited to prevent recurrence of calcium-
containing kidney stones [40]. In 1970, Yendt et al. reported initial observations of an uncontrolled series 
of 72 recurrent calcium stone formers treated with HCTZ in doses from 100 mg to 200 mg daily [41]. 
The treatment seemed highly effective: compared to pretreatment, HCTZ at such doses reduced stone 
episodes from 0.57 to 0.03 per patient year in patients without radiologic evidence of stone disease at 
treatment start and from 1.1 to 0.53 per patient year in patients with residual stone load at treatment 
initiation. Similar findings were reported by the same group in a follow up publication several years later 
with a total of 346 patients [42]. Based on these publications, despite the absence of randomized 
controlled trials (RCTs), thiazide rapidly became a cornerstone of medical stone prevention.  
In August 2015, we conducted a systematic database search for RCTs that tested the efficacy of 
thiazides in the prevention of recurrent nephrolithiasis. Our search covered MEDLINE, the Cochrane 
Database, Google Scholar and the Web of Science for English language trials that had clinical endpoints 
(symptomatic or radiologic stone recurrence) and at least 1 year of follow-up. We also searched for 
unpublished trials at the World Health Organization’s International Clinical Trials Registry Platform 
(www.who.int/trialsearch), the NIH funded site ClinicalTrials.gov (https//:clinicaltrials.gov) and on 
internet databases provided by the US Food and Drug Administration and by the European Medicines 
Agency [42]. Our search revealed 11 published RCTs [43-53] and no unpublished trials. All 11 RCTs 
identified are depicted in Table 3.1-1. The first RCT for stone prevention with thiazide diuretics was 
published in 1981. At total of seven trials were conducted in the 1980’s, three in the 1990’s and only 
one trial was conducted after the year 2000. As shown in Table 1, with the exception of two trials [51, 
53], which were the first two RCTs conducted in the field, thiazides significantly reduced stone 
recurrence compared to placebo or control, in average by about 50% (Table 1). The thiazides employed 
in the two negative trials were bendroflumethiazide at the dosage of 2.5 mg three times daily and HCTZ 
at the dosage of 25 mg twice daily. Follow-up duration of the two negative trials was very short (1 and 
1.6 years, respectively) compared to 2 – 5 years in the positive trials, which may explain the lack of 
benefit observed. All trials were small and only one trial included > 100 patients [47]. The 11 trials 
included 693 patients in total (Table 1). In three trials, the outcome was symptomatic stone recurrence, 
in the other eight trials the outcome was a composite of symptomatic and radiologic recurrence (Table 
3.1-1). In all trials, radiologic recurrence was studied with the low sensitivity and specificity imaging 
modalities, KUB or IVU. A consistent finding in these thiazide RCTs was that stone-formation rate 
between treated and control groups did not begin to diverge until after at least one year of therapy [54]. 
As detailed in Table 3.1-1, our review indicates that all thiazide RCTs thus far conducted have significant 
methodological deficiencies including unclear allocation concealment, lack of double-blinding, no 
intention-to-treat analysis and lack of AE and drop out reporting.  
Interestingly, in only three of 11 RCTs hypercalciuria was an inclusion criterion and thiazides seem to 
be effective in reducing stone recurrence regardless of the presence or absence of hypercalciuria (Table 
3.1-1). There are at least two possible explanations for this observation: first, Curhan et al. demonstrated 
in a large epidemiological study that calciuria is a gradual risk factor for the development of kidney 
stones [55]. An increase in the relative risk for kidney stone formation was observed when urinary 
calcium excretion exceeded 2.5 mmol/d, which is far below the current definition of hypercalciuria on a 
random outpatient diet (> 7.5 mmol/d). Second, thiazides, in addition to reducing calciuria, have 
favorable effects on other urinary constituents that may reduce stone risk. The latter include reduction 
of urinary pH and oxalate excretion and an increase of urinary magnesium and zinc excretion [56, 57]. 
HCTZ was used in five of the 11 thiazide trials and thus is currently the best studied thiazide in the 
prevention of stone recurrence [45, 48, 50, 52, 53]. However, bendroflumethazide, chlorthalidone, 
trichlormethiazide and indapamide also reduced stone recurrence in one or more trial and seem to be 
effective as well (Table 3.1-1). In all trials, high thiazide doses were employed, in the case of HCTZ, 50 
- 100 mg daily. In four of the five trials where HCTZ was employed, the diuretic was given twice daily, 

 
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whereas in the treatment of arterial hypertension, HCTZ is given once daily [54]. Apart from reducing 
blood pressure, once daily HCTZ at 50 mg, 25 mg or 12.5 mg daily also reduced calciuria, a surrogate 
marker for stone prevention [58]. Twice daily HCTZ increases the frequency of side effects and 
augments diuresis at night and thereby likely affects compliance [54, 58].  
A recent study showed that thiazide diuretics are often not used in an evidence-based fashion for the 
prevention of stone recurrence [59]. In that study, 107 patients with a filled prescription for thiazide 
diuretics that underwent a 24-hour urine stone risk factor analysis and had medical record 
documentation that the thiazide was prescribed for calcium-containing kidney stone recurrence were 
analyzed. Only 35% of HCTZ-treated patients received ≥50 mg/ d, a dose previously shown to reduce 
stone recurrence in RCTs. 52% of patients were prescribed 25 mg daily and 13% 12.5 mg daily, doses 
which were not studied in RCTs. The tendency to prescribe lower doses of thiazides in patients with 
recurrent nephrolithiasis was likely triggered by a paradigm shift in prescribing practices for thiazides 
used for the treatment of arterial hypertension. Starting in the 1980’s, lower doses of HCTZ (12.5–25 
mg daily) were increasingly employed [60]. While clinical and biochemical side effects were noted to be 
dose dependent, the antihypertensive effects remained robust, even at lower doses [60, 61]. If this is 
also true for recurrent calcareous nephrolithiasis is currently unknown. 
Fink et al. recently conducted a systematic review of RCTs for the medical management to prevent 
recurrent nephrolithiasis [62]. RCTs involving dietary or pharmacologic treatments to prevent recurrent 
kidney stones in adults that reported clinical outcomes or harms were included in the meta-analysis. 
The search of the authors covered MEDLINE, the Cochrane Database, Google Scholar and the Web of 
Science for English-language studies published from 1948 through 2011. Using criteria developed by 
the Cochrane Collaboration, individual study quality was rated good, fair or poor on the basis of 
adequacy of allocation concealment, blinding, reporting reasons for attrition and how analyses 
accounted for incomplete data. Following methods developed by the Agency for Healthcare Research 
and Quality (AHRQ)’s Effective Health Care Program [63], strength of evidence (SOE) for the efficacy 
of each treatment was graded on the basis of risk of bias, consistency, directness and precision. The 
review was nominated to the AHRQ by the American Urological Association but was funded by the 
AHRQ. A total of 28 trials (8 dietary and 20 pharmacologic) were included in the meta-analysis. Six of 
the 11 thiazide trials we identified in our own database search were included in the meta-analysis (Table 
3.1-1) [43-45, 50, 52, 53]. Patients enrolled in the selected thiazide trials had two or more stone events 
prior to study inclusion, mean treatment duration was 35 months with a cumulative number of 365 
patients. Patients were assigned to thiazide and either placebo [44, 45, 53] or control [43, 50, 52]. The 
authors concluded that AEs were inconsistently reported but that compared with participants in the 
placebo and control groups, those randomly assigned to receive thiazides were statistically significantly 
more likely to withdraw for any reason or because of AEs [62]. Only one of the selected trials assessed 
symptomatic stone recurrence (treatment versus placebo RR 1.04, 95% CI 0.39 – 2.8) [53] and no trial 
reported radiologic outcomes separately. The other five trials with a cumulative number of 300 patients 
reported a composite endpoint with radiologic and symptomatic stone recurrence. Treatment with 
thiazides decreased the risk for this composite outcome (26 vs. 55%; RR 0.52, 95% CI 0.39 – 0.69; 
NNT 3.4). Fink et al. stated in their review that the meta-analysis was greatly limited by the available 
data and that additional trials are warranted [62]. Critical points raised were i) the low amount of trials 
available and the small sample sizes, ii) lack of data on treatment harms, iii) the fact that all trials included 
only adults with idiopathic calcium stones, iv) lack of symptomatic stone recurrence reporting as an 
isolated outcome, v) the fact that only one trial recruited patients from a primary care setting and vi) 
inconsistent reporting and categorization of baseline biochemistry measures. 
Overall, the authors concluded that all six thiazide trials included in their meta-analysis were of fair 
quality and that there was moderate SOE for the composite end point of symptomatic and radiologic 
stone recurrence but that there was insufficient SOE for the individual outcomes symptomatic or 
radiologic stone recurrence [62]. 

 
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Rationale: 
We and others [62] identified major issues in design, conduct, analysis and reporting in thiazide RCTs 
conducted thus far for the prevention of stone recurrence.  
 
Major issues encountered include: 
- 
Lack of double-blinding 
- 
Lack of intention-to-treat analysis 
- 
Unclear allocation concealment 
- 
Lack of AE and drop out reporting 
- 
Unknown baseline risk of disease severity or biochemical abnormalities 
- 
Lack of patients stratification based on stone composition 
- 
Lack of outcome uniformity 
- 
Absence of data on the impact of pharmacological interventions on disease risk factors 
- 
Low overall number of patients studied 
- 
Use of high dose thiazide treatments 
- 
Inadequate dietary measures in control and treatment groups 
- 
Use of low sensitivity and low specificity imaging for radiologic outcomes 
- 
Use of outdated dietary recommendations in placebo or control groups 
 
The methodological deficiencies are of great concern. Review of the trials reveals that none of the 11 
trials fulfills the quality standards expected of a randomized, placebo-controlled, double-blind trial. While 
the methodological deficiencies of the trials are obvious for anyone concerned with clinical research, 
several points peculiar to kidney stone disease deserve further explanation:  
 
Drug dosing: High doses of thiazides were employed in these trials, in the case of the best studied 
thiazide, HCTZ, 50 - 100 mg daily. At such high doses, side effects occur in 30 – 40% of patients and 
include electrolyte disturbances, muscle cramps, orthostatic hypotension, gastrointestinal symptoms, 
hypocitraturia, gout, impaired glucose tolerance, skin rashes and erectile dysfunction [52, 56]. Since AE 
and drop out reporting in all trials was very poor, tolerability and harms of high dose thiazide treatments 
remain largely unknown. Nowadays, thiazides are widely used in the treatment of arterial hypertension 
and recurrent nephrolithiasis, but at significantly lower doses [54, 58, 59]. However, this practice is not 
supported by randomized evidence in the case of recurrent nephrolithiasis and consequently, we do not 
know whether the currently employed low dose thiazide regimens are effective in reducing the risk for 
stone recurrence.  
Dietary interventions: Non-pharmacologic interventions for recurrence prevention are very effective [62]. 
Several landmark trials investigating the effect of dietary measures to prevent stone recurrence were 
published after the thiazide trials had been completed [64, 65]. In idiopathic recurrent calcareous stone 
formers, high fluid intake or a diet restricted in animal protein and salt combined with a normal calcium 
intake each reduce stone recurrence by ~50% [64, 65]. In fact, the thiazide trials were conducted at a 
time when recurrent calcareous stone formers were given the advice to limit dietary calcium intake, a 
long-held opinion that has since been refuted both by observational data and a prospective RCT [65, 
66]. Thus, the added benefit of thiazides to current state-of-the non-pharmacologic measures in stone 
prevention remains unknown. 
Imaging modality for radiologic outcomes: Some patients with “recurrent” stones in past thiazide RCTs 
may have already harbored the stones at baseline and experienced stone passage rather than 
progression of disease. The latter is also the most likely explanation for the repeated observation made 
in past RCTs (beyond thiazides) concerned with recurrence prevention of renal stones that stone 
incidence in treatment and control groups are diverting only after one year of treatment or later, although 
most patients were considered “stone free” at study initiation, based on KUB or IVU imaging. Although 
CT is by far the most sensitive and most specific imaging modality for renal stone disease, no thiazide 
trial (or any other RCT concerned with kidney stone prevention) thus far used this imaging modality to 
monitor progression of stone disease. As outlined earlier, modern low-dose CT protocols cause greatly 
reduced radiation exposure while preserving a high sensitivity and specificity, making low-dose CT the 
kidney stone imaging modality of choice to monitor disease progression.  
Thus, in summary, benefits and harms of thiazide treatments in general for the prevention of stone 
recurrence are still unclear. In addition, the efficacy of the currently employed low dose thiazide 
regimens to prevent stone recurrence is not known. 
3.2 
Investigational Product (treatment, device) and Indication  
HCTZ belongs to the group of thiazide diuretics. Thiazide diuretics inhibit the sodium/ chloride co-

 
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transporter (NCC or SLC12A3) in the distal tubule of the kidney. Inhibition of NCC causes an increased 
excretion of sodium, chloride and water in the urine and thereby lowering of blood pressure. At the same 
time, thiazide diuretics reduce renal calcium excretion by a still ill-defined intrarenal mechanism. In 
Switzerland, HCTZ as monosubstance is marketed exclusively as Esidrex® by Medius AG, 4132 
Muttenz in divisible tablets of 25 mg. The approved indications include: arterial hypertension, edemas, 
heart failure and recurrence prevention of calcium-containing kidney stones. For the treatment of arterial 
hypertension, Esidrex® is recommended in doses of 12.5-50 mg, once or twice daily. For the recurrence 
prevention of calcareous nephrolithiasis, Esidrex® is recommended in doses of 25 or 50 mg twice daily 
(Esidrex® summary of product characteristics, November 2018). In addition to the monosubstance, 
HCTZ is currently available in 78 different galenic formulations in Switzerland as combination with ACE-
inhibitors, angiotensin II receptor blockers or non-thiazide diuretics (www.swissmedicinfo.ch, last 
accessed on 11.08.2016).  
Detailed information to pharmacokinetics, side effects and interaction profile of HCTZ can be found at 
www.swissmedicinfo.ch. 
3.3 
Preclinical Evidence  
There is no animal model, which recapitulates the pathophysiology of calcareous nephrolithiasis in 
humans. Hence, there is no supportive preclinical evidence for this trial. However, there is ample 
evidence that thiazide diuretics reduce calciuria, a surrogate marker for calcareous nephrolithiasis, in a 
wide variety of mammals. 
3.4 
Clinical Evidence to Date  
The clinical evidence on the efficiency of HCTZ in recurrence prevention of calcareous nephrolithiasis 
has been reviewed in detail in section 3.1. 
3.5 
Dose Rationale: Rationale for the intended purpose in study 
Our systematic review of thiazide trials in the prevention of recurrent nephrolithiasis in section 3.1 
reveals that the type of thiazide used and the dose regimens employed varied widely. Although the 
evidence is currently very limited, no thiazide seems to be superior for stone prevention. As outlined 
earlier, a common theme of all trials was that very high doses of thiazides were employed. Only in one 
trial more than one dose of thiazide was tested [45]. In that trial, chlorthalidone 25 mg and 50 mg daily 
were equally effective in preventing the primary outcome stone recurrence compared to placebo. While 
the reduction in calciuria compared to placebo was also not different between the two dose regimens, 
25 mg chlorthalidone daily reduced oxaluria significantly whereas 50 mg chlorthalidone daily did not. In 
contrast, however, 50 mg chlorthalidone daily caused more frequent and more pronounced hypokalemia 
than 25 mg chlorthalidone daily. HCTZ is by far the best studied thiazide diuretic for both currently 
recognized indications, arterial hypertension and recurrent calcareous nephrolithiasis [55]. In addition, 
HCTZ (once daily) is the thiazide most commonly found in combination drugs prescribed for the 
treatment of arterial hypertension. Based on these facts, we decided to use HCTZ for the NOSTONE 
trial. To improve compliance and reduce side effects, we plan to compare 12.5 mg or 25 mg or 50 mg 
HCTZ once daily to placebo. As is the case for all thiazides, HCTZ has an excellent bioavailability and 
thus will be given per os. 
3.6 
Explanation for choice of comparator (or placebo)  
Dietary and lifestyle interventions are highly effective in preventing recurrence in calcareous 
nephrolithiasis and are thus always the basis of stone prevention [63]. As such, any trial assessing 
pharmacologic interventions for the prevention of stone recurrence must compare the efficacy of the 
drug treatment to the state-of-the-art non-pharmacologic interventions. On the basis of RCT evidence, 
current American [31] and European [23] nephrolithiasis guidelines recommend the following non-
pharmacologic measures in adult patients with recurrent calcareous nephrolithiasis: increased fluid 
intake with circadian drinking to ensure daily urinary volumes of at least 2 – 2.5 L, a balanced diet rich 
in vegetables and fibers with normal calcium content (1-1.2 g/day) but limited NaCl (4-5 g/day) and 
animal protein (0.8-1 g/kg/day) content. Furthermore, patients must be advised to retain a normal body 
mass index (BMI), have adequate physical activity and balance excessive fluid loss. All patients in the 
placebo and treatment arms of our planned study will receive these current non-pharmacologic 
recommendations for stone prevention. Since the added benefit of thiazides to current state-of-the non-
pharmacologic measures in stone prevention remains unknown, as outlined in detail in section 3.1, a 
placebo arm needs to be part of this trial. 

 
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3.7 
Risks/ Benefits 
Calcareous nephrolithiasis is a disease with high recurrence rates that causes high morbidity in affected 
individuals with repeated exposures to urological procedures. The risk a patient is willing to accept is a 
personal decision based on his/ her individual and familial experience with the disease. HCTZ potentially 
lowers the recurrence risk of the disease, although in the dosages applied in the study it has not yet 
been approved for this indication. HCTZ has been used for the treatment of arterial hypertension in the 
dosages tested in this study for over 40 years. Thus, the treatment risks by HCTZ are well characterized, 
manageable and must be weighed against the consequences of no treatment. The most common AEs 
of HCTZ therapy include those arising from saluresis including reduction of blood pressure, polyuria, 
dehydration and electrolyte abnormalities. Therefore, appropriate patient monitoring and management 
will be implemented to mitigate this potential risk in the kidney stone population. These AEs should be 
considered in light of the benefits of a reduced risk of stone recurrence, including pain, urinary tract 
infection and need for urological interventions. With sufficient knowledge of the benefits and risks and 
risk mitigation strategies, patients and their physicians may make informed decisions about HCTZ 
treatment. In the final assessment, the overall benefit-risk profile of HCTZ for the recurrence prevention 
of calcareous nephrolithiasis appears favourable, offering a real opportunity to fill a longstanding unmet 
medical need. 
The results of the study, will yield important clinical information for the care of patients with recurrent 
calcareous nephrolithiasis, which is one of the most frequent human diseases (~10% of worldwide 
population affected). Study participants who finished the trial or stopped the IMP during the trial will be 
seen in the different ambulatory stone clinics of the participating centers at least annually, if medical 
condition warrants, more frequently. 
Because the detection rate of plain abdominal X-ray imaging (KUB radiography) for urinary stones is far 
inferior to the detection rate of CT or IVU, and because often several KUBs in different angles have to 
be performed for a better detection of kidney stones, the international guidelines recommend low-dose 
CT for the detection and follow-up of urinary stone patients [23, 31-33]. Modern low-dose CT protocols 
cause greatly reduced radiation exposure while preserving a high sensitivity of up to 98% [69] and 
specificity of up to 97% [34, 35, 69]. Current radiation exposure of low dose CT protocols for the 
detection of urolithiasis is in the range of 0.5-1.9 mSV, and thus similar to (single) KUB radiography (0.5 
– 1.1 mSv) but lower than IVU (1.3 -3.93 mSv) [20, 23, 35, 36, 70]. The international guidelines 
recommend imaging of recurrent stone formers at least once a year [31]. Thus, yearly imaging with low 
dose CT is in line with the international guidelines [31] and with our daily practice (usually 6-monthly to 
yearly imaging). It is a rather conservative imaging strategy compared to other centers, and leads to a 
relatively low radiation exposure which does not exceed the standard radiation dose for recurrent stone 
formers during regular follow-up. Even more, the radiation exposure of our patients is far lower than the 
50 mSv throughout a single year or the 20 mSv per year over a 5-year period as accepted as the 
threshold levels for “safe” exposure by the International Commission on Radiological Protection (ICRP) 
[71]. 
3.8 
Justification of choice of study population 
For the trial, thiazide naïve adult individuals with recurrent calcareous nephrolithiasis will be recruited. 
80 – 90% of patients with recurrent nephrolithiasis belong into this group. Hence, the study population 
will be representative of the far most common type of renal stone former encountered in clinical routine. 
Recurrent is defined as two or more stone episodes in the last 10 calendar years, calcareous is defined 
as 50% or more calcium oxalate, calcium phosphate or a mixture of both in a previous stone analysis. 
No vulnerable individuals will be included in the study. 
4. STUDY OBJECTIVES  
4.1 
Overall Objective 
The study aims to describe an efficacy and safety profile of HCTZ for the recurrence prevention of 
calcareous nephrolithiasis. 

 
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4.2 
Primary Objective 
Dose-response relationship for three different dosages of HCTZ using incidence of stone recurrence (a 
composite of symptomatic or radiologic recurrence) as the primary outcome. 
4.3 
Secondary Objectives 
Efficacy of the different dosages of HCTZ in terms of the primary outcome as well as the individual 
components of the composite primary outcome, i.e. incidence of symptomatic stone recurrence and 
incidence of radiologic stone recurrence. Effects of different dosages of HCTZ on urinary biochemistry 
(efficacy and safety aspects) and the impact of different baseline characteristics on the effects of the 
different dosages (effect modification). 
4.4 
Safety Objectives 
Long-term safety and tolerability of HCTZ compared to placebo. 
5. STUDY OUTCOMES  
5.1 
Primary Outcome 
5.1.1 
Primary outcome at patient level 
The primary outcome at the patient level is the incidence of stone recurrences during study treatment. 
Stone recurrence is the composite of symptomatic or radiological recurrences. 
 
Symptomatic stone recurrence is defined as visible passage of a stone with or without accompanying 
typical symptoms such as flank/ loin pain and hematuria or a symptomatic or asymptomatic stone 
requiring urological intervention for stone removal. In case of potential stone passages without visible 
stones, it will be up to the local investigators to evaluate patients’ symptoms and determine whether a 
stone passage occurred or the symptoms were rather due to a different cause. 
 
Baseline stone recurrence includes all stone events that occurred in the 10 calendar years preceding 
the year of randomization and until randomization. For the report of stone events, if the exact month a 
stone event occurred is not known, the first day of the month will be conventionally reported as date of 
the event, if only the calendar year is known, the first of January of the same year will be used as 
conventional date for the event. Several events occurring at unknown dates within a known period of 
time will be distributed throughout the period of interest at regular intervals for the purpose of reporting. 
 
Radiological stone recurrence as assessed by low-dose non-intravenous (iv) contrast CT imaging is 
defined as the appearance of new calculi or enlargement of preexisting calculi with reference to the 
baseline CT performed at visit 3 to the end of study treatment. The processing and evaluation of the CT 
images is described in a specific SOP (SOP_CT_V1.3). 
 
Stone events during the first six weeks after randomization will not be considered for analysis. 
5.1.2 
Primary outcome at study level 
Relationship of the incidence of stone recurrences during study treatment and dose group. 
5.2 
Secondary Outcomes 
Secondary outcomes are the following: 
- 
The individual components of the composite primary outcome, i.e. number of symptomatic stone 
recurrences and number of radiologic stone recurrences 
- 
Changes in urinary biochemistry elicited by HCTZ or placebo 
- 
Impact of baseline disease severity (incidence of stone recurrence during the last 10 calendar 
years prior to and until randomization) and biochemical abnormalities on stone recurrence 
- 
Impact of stone composition on stone recurrence 
 

 
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Given the high prevalence of the disease [1, 2], the morbidity, pain and costs associated with 
symptomatic stone disease [5] as well as the high likelihood of asymptomatic stones to become 
symptomatic [67], our chosen outcomes are clinically highly relevant. 
5.3 
Other Outcomes of Interest 
During one of the scheduled follow up visits, the investigators will collect a DNA sample from the patients. 
DNA will be stored in the NOSTONE Biobank at the Bern University Hospital (Abteilung für 
Humangenetik), Switzerland. Patients must sign a separate patient informed consent for the NOSTONE 
Biobank. The rules and procedures of the NOSTONE biobank are described in a specific booklet 
(NOSTONE Biobank Reglement). 
5.4 
Safety Outcomes 
Safety endpoints to be analyzed include a descriptive summary of the following parameters: 
- 
SAEs 
- 
Pre-specified AEs of special interest (defined in section 9.2.4.2) 
- 
Vital signs 
6. STUDY DESIGN  
6.1 
General study design and justification of design  
 
 
 
Figure 6.1-1: NOSTONE trial design schematic 

 
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This is a multicenter, randomized, placebo-controlled, observer-, clinician- and patient-blinded, parallel-
group study to compare the efficacy and safety of HCTZ in the recurrence prevention of calcareous 
nephrolithiasis. 
Eligible patients will be randomized in equal proportions between 12.5 mg, 25 mg or 50 mg HCTZ or 
placebo. All subjects will be given the IMP (HCTZ or placebo) once daily in the morning. Placebo will be 
administered to subjects randomized to that treatment in a form identical to the HCTZ capsules. The 
first dose of the IMP will be administered the day after the randomization. 
A total of 416 participants, 104 in each group, will be included in the study. Recruitment of participants 
is planned to occur over a period of 30 months at all 12 study sites. Recruitment in Bern will be extended 
for another 2 months. Study treatment will be 36 months for subjects enrolled in the first 12 months of 
the recruitment period and for a minimum of 24 months and maximum of 36 months for subjects 
recruited in the remainder of the recruitment period. 
 
6.2 
Methods of minimizing bias  
6.2.1 
Randomization  
We will use stratified randomization to assign participants to the different trial arms with the number of 
previous stone events as stratification factors: stratification group 1: 2 or 3 stone events within 10 
calendar years prior to randomization; stratification group 2: ≥ 4 stone events within 10 calendar years 
prior to randomization. Allocation will be concealed using sequentially coded drug packs that are 
otherwise identical. Preparation and handling of the unblinded drug packs will be done at a facility 
otherwise not involved in the trial. Randomization lists at CTU Bern will be stored electronically with no 
access for persons directly involved in the trial. Allocation to the trial arms will be done using numbered 
drug packs. Randomization lists will be generated by a statistician at CTU Bern otherwise not involved 
in the trial following dedicated standard operating procedures. The statistician will communicate directly 
with the facility, which prepares the drug packs (Grosse Apotheke Dr. G. Bichsel AG, Interlaken, 
Switzerland). Investigators at each site will assign the drug pack with the next sequential number to the 
next patient (consecutive). Content of the drug packs is based on randomization lists as described above. 
6.2.2 
Blinding procedures  
All trial personnel but the statistician generating the list and the personnel at the facility preparing the 
drug packs (Grosse Apotheke Dr. G. Bichsel AG, Interlaken, Switzerland) will be blinded to the assigned 
treatment. Blinding will be upheld until all analyses will have been completed. HCTZ and placebo will be 
provided in identically looking blistered capsules in drug packs. Besides the consecutive number, packs 
and pack content will look identical. Therefore, all trial personnel that is involved in recruitment and care 
of patients, trial assessment, monitoring and analyses will be blinded to the assigned trial arm. 
Blinding will remain in place until the statistician codes the primary analysis of the primary and secondary 
outcomes and produces a dummy report of the primary analysis using a randomly generated group 
variable. The true group variable becomes open after the completion of the dummy report and gives 
place to the final report of all the analysis as well as the quality control by the independent statistician. 
 
6.2.3 
Other methods of minimising bias  
To minimize referral bias, we plan to collaborate with external Nephrologists, Urologists, Internists and 
Family practitioners. 
To minimize bias of primary outcome assessment for radiological recurrence, all renal CTs will be 
assessed centrally at Inselspital Bern. 
6.3 
Unblinding Procedures (Code break)  
HCTZ is an established drug with a well-known safety profile. Although extremely rare, there are reports 
of allergic reactions either directly or because of sulfonamide cross-sensitivity. Unblinding will only be 
allowed in situations where knowledge of the allocation is needed for the care of a patient. Because 
there is no antidote and the allergic reactions as described in the literature as well as other serious 
adverse reactions such as aplastic anemia or angioedema are treated independently from any 
knowledge of treatment assignment, we do not expect any emergency unblinding. Note that a break of 
the randomization code per se is not a reason to stop study treatment or to withdraw the participant from 

 
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the study. 
Unblinding will be managed centrally for all the centers at the pharmacy of the Inselspital. Dedicated 
instructions will be provided to the centers. 
7. STUDY POPULATION  
This trial will include adult individuals with recurrent calcareous nephrolithiasis. Outpatients newly 
referred to stone clinics for metabolic stone work-up will be recruited for the trial at 7 Cantonal Hospitals 
(Aarau, Bellinzona, Chur, Lugano, Lucerne, Sion, St. Gallen) and 5 University Hospitals (Basel, Bern, 
Geneva, Lausanne, Zurich) in Switzerland. If enrolment goals are not met, we will 1) try to enhance 
referrals to trial sites by contacting local Urologists and Nephrologists 2) extend recruitment to 
outpatients with recurrent calcareous nephrolithiasis that have already undergone metabolic work-up 
for stone disease but are seen for regular follow-up visits at the trial sites.  
In order to maximize power and minimize the possibility of a Type II error, trial enrollment will continue 
until at least 416 individuals are randomized. 
7.1 
Eligibility criteria  
Individuals fulfilling all of the following inclusion criteria are eligible for the study: 
1. Informed Consent as documented by signature 
2. Age 18 years or older 
3. Recurrent kidney stone disease (≥ 2 stone events within the last 10 calendar years prior to 
randomization, i.e. during the 10 calendar years preceding the year of randomization and until 
randomization) 
4. Any past kidney stone containing 50% or more of calcium oxalate, calcium phosphate or a 
mixture of both 
 
The presence of any one of the following exclusion criteria will lead to exclusion of the individual: 
1. Pharmacologic prevention for stone recurrence less than 3 months prior to randomization 
2. Patients with secondary causes of recurrent calcareous nephrolithiasis including: 
- 
Severe eating disorders (anorexia or bulimia) 
- 
Chronic inflammatory bowel disease, bariatric surgery, intestinal surgery with 
malabsorbtion or chronic diarrheal status 
- 
Sarcoidosis 
- 
Primary hyperparathyroidism 
- 
Complete distal tubular acidosis 
- 
Active malignancy 
3. Patients with the following medications:  
- 
Thiazide or loop diuretics 
- 
Carbonic anhydrase inhibitors (including topiramate) 
- 
Xanthine oxidase inhibitors (febuxostat or allopurinol) 
- 
Alkali, including potassium citrate or sodium bicarbonate 
- 
Treatment with 1,25-OH Vitamin D (calcitriol) 
- 
Calcium supplementation 
- 
Bisphosphonates 
- 
Denusomab 
- 
Teriparatide 
- 
Glucocorticoids 
4. Obstructive uropathy, if not treated successfully 
5. Urinary tract infection, if not treated successfully  
6. Chronic kidney disease (defined as CKD-EPI eGFR < 30 mL/min per 1,73 m2 body surface 
area for more than 3 months) 
7. Patients with a kidney transplant 
8. > 3 gout arthritis episodes within one year prior to randomization or gout arthritis requiring uric 
acid lowering therapy 
9. Cystinuria at screening 
10. Hypokalemia (blood potassium level < 3 mmol/L) at screening 

 
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11. Hyponatremia (blood sodium level < 125 mmol/L) at screening 
12. Pregnant and lactating women [pregnancy test to be performed for women of child-bearing 
potential (defined as women who are not surgically sterilized/ hysterectomized, and/ or who 
are postmenopausal for less than 12 months)] 
13. Previous (within 3 months prior to randomization) or concomitant participation in another 
interventional clinical trial 
14. Inability to understand and follow the protocol 
15. Known allergy to the study drug 
7.2 
Recruitment and screening  
Target population of the study are individuals who suffer from recurrent calcareous nephrolithiasis. Two 
different groups of individuals will be screened and recruited in the study by local investigators: 1) 
individuals newly referred for metabolic work-up for recurrent stone disease to study sites and 2) 
individuals who already underwent work-up for recurrent stone disease and are currently undergoing 
regular follow-up for recurrent stone disease at the study sites. After approval by the CEC and CA, the 
study will be announced to the Nephrology and Urology staff at the 12 study sites. We will also inform 
external Nephrologists, Urologists, Internists and Family practitioners by emails and kick-off meetings 
upon approval by the CEC and CA. 
If available medical history indicates that an individual may be eligible for study participation, the 
individual will be informed in detail about the study by local investigators. Inclusion in the study will take 
place only upon receipt of written informed consent and if all eligibility criteria are fulfilled. 
No payment or compensation will be given to study participants.  
7.3 
Assignment to study groups  
Stratified randomization will be used to assign participants to the different trial arms with the number of 
previous stone events as stratification factors (see section 6.2.1). Allocation will be concealed using 
sequentially coded drug packs that are otherwise identical. Randomization lists will be generated by a 
statistician at CTU Bern otherwise not involved in the trial following dedicated standard operating 
procedures. The statistician will communicate directly with the facility, which prepares the drug packs 
(Grosse Apotheke Dr. G. Bichsel AG, Interlaken, Switzerland). Investigators at each site will assign the 
drug pack with the next sequential number to the next patient (consecutive). Content of the drug packs 
is based on randomization lists as described above. Preparation and handling of the unblinded drug 
packs will be done at a facility otherwise not involved in the trial. Randomization lists at CTU Bern will 
be stored electronically with no access for persons directly involved in the trial. 
7.4 
Criteria for withdrawal/ discontinuation of participants  
7.4.1 
Discontinuation of study IMP  
Study IMP must be permanently discontinued if any of the following occurs: 
- 
If any exclusion criterion applies during the trial, except the incompatible medications. The IMP will 
be discontinued only if the patient took the medications listed in the exclusion criteria for more 
than 4 months* 
- 
If the responsible study investigator feels that treatment with the study regimen is harmful to the 
participant’s well-being 
- 
If patient is non-compliant with the study intervention as judged by the investigator and/ or the 
sponsor 
- 
Pregnancy in a study participant 
- 
Hypokalemia (blood potassium level < 3 mmol/L) not responsive to supplementation therapy 
- 
Profound hyponatremia (blood sodium level < 125 mmol/L) recurring after normalization upon 
temporary suspension of IMP 
- 
Gouty arthritis recurring > 3 times per year or requiring uric acid lowering therapy. 
- 
Allergic reaction of skin as judged by the investigator 
- 
> 3 recurrences of symptomatic stone events during the trial 
 
*The patients are either contacted via phone or visited every 3 months (+/- 1 month). If a patient is taking 
a medication from the prohibited list, the prescription will be discussed with the family practitioner 
(Hausarzt) and it will be evaluated if it is possible to stop the prohibited medication or if the IMP needs 
to be suspended. 
 

 
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Participants who permanently discontinue the IMP are expected to continue in the follow-up period and 
to attend all protocol-specified study visits. If study visits are not possible, a telephone consultation will 
be performed to determine if relevant health events/ endpoints have occurred. 
7.4.2 
Discontinuation of study 
Study participants must be withdrawn from the study if the following occurs: 
- 
At the participants own request 
- 
If, in the investigator's opinion, continuation of the study would be harmful to the subject’s well-
being 
 
A study participant who discontinues study participation prematurely for any reason is defined as 
dropout if the participant has already been randomized. A study participant who terminates the study 
before randomization is regarded as a screening failure. 
 
No replacement of participants discontinuing study treatment or study participation is foreseen. 
 
Any samples and data collected until study withdrawal will remain coded for the analysis. It is not 
possible to anonymize the data and samples upon withdrawal.  
 
8. STUDY INTERVENTION  
8.1 
Identity of Investigational Products 
8.1.1 
Experimental Intervention  
Identical looking gelatin capsules containing 12.5 mg or 25 mg or 50 mg HCTZ will be supplied by 
Grosse Apotheke Dr. G. Bichsel AG, Interlaken, Switzerland according to applicable regulations. 
8.1.2 
Control Intervention  
Placebo gelatin capsules indistinguishable from HCTZ capsules will be supplied by Grosse Apotheke 
Dr. G. Bichsel AG, Interlaken, Switzerland according to applicable regulations. 
8.1.3 
Packaging, Labelling and Supply (re-supply)  
IMP capsules will be provided as bulk supply in bottles labelled with trial-specific labels according to 
Annex 13, "Manufacturing of investigational medicinal products" to Volume IV of the EU guideline to 
Good Manufacturing Practice: 
 
- 
Name, address and telephone number of the sponsor-investigator 
- 
Pharmaceutical dosage form (capsules), route of administration (per os), number of capsules 
- 
Batch number, Lot number 
- 
Trial acronym (Nostone-trial) 
- 
Trial subject identification number 
- 
Storage conditions 
- 
Expiry date 
- 
Safety warning “Keep out of reach of children” 
 
8.1.4 
Storage Conditions  
All IMPs will be stored in a securely locked cabinet or enclosure. Access will be limited to investigators 
and their designees. Neither investigators nor any designees may provide IMP to any subject not 
participating in this protocol. The IMP will be stored according to the conditions specified in the IMP 
label. The clinical site staff will maintain a temperature log in the drug storage area recording the 
temperature using (at minimum) a Min/ Max thermometer at least weekly. 

 
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8.2 
Administration of experimental and control interventions 
8.2.1 
Experimental Intervention  
HCTZ capsules will be administered once daily per os in the morning. HCTZ has excellent bioavailability 
and thus per os administration is chosen for this trial (www.swissmedicinfo.ch). The rationale for AM 
dosing is the fact that HCTZ induces a diuresis that starts 1-2 hours after ingestion, peaks 4-6 hours 
after ingestion and lasts until 10-12 hours after ingestion (www.swissmedicinfo.ch). Thus, HCTZ-
induced diuresis potentially disturbs sleep of participants when PM dosing is chosen. Minimal effective 
dose for HCTZ-induced diuresis and blood pressure reduction in humans is 12.5 mg per os once daily, 
maximal effective dose 50 mg per os once daily (www.swissmedicinfo.ch). Hence, 12,5 mg, 25 mg and 
50 mg per os once daily were chosen as HCTZ doses for this trial. 
8.2.2 
Control Intervention 
Placebo capsules will be administered once daily per os in the morning, identical to HCTZ capsules. 
8.3 
Dose modifications  
8.3.1 
Electrolyte Disturbances 
Hypokalemia, hyponatremia and hypomagnesemia can occur in patients with HCTZ treatment. In the 
case of hypokalemia (< 3 mmol/L), supplementation with oral potassium chloride or co-administration 
of the potassium-sparing diuretic is recommended. In the case of hypomagnesemia (< 0.5 mmol/L), 
supplementation with oral magnesium aspartate is recommended. Potassium or magnesium citrate or 
bicarbonate salts may affect stone recurrence and are not allowed during the trial. If hypokalemia or 
hypomagnesemia are not responsive to the above recommendations, the IMP will be withdrawn from 
the patient. In the case of profound hyponatremia (< 125 mmol/L), temporary suspension of the IMP 
until normalization of the blood sodium concentration is recommended. The IMP can then be restarted. 
If profound hyponatremia recurs, the IMP will be withdrawn from the patient. 
8.3.2 
Renal function impairment 
Because of blood pressure lowering and volume depletion, therapy with HCTZ may worsen renal 
function. The IMP will be withdrawn if CKD-EPI eGFR drops below 30 mL/min per 1,73 m2 body surface 
area for more than 3 months. 
8.3.3 
Gout arthritis 
HCTZ may increase blood uric acid levels which can cause gout arthritis. An acute gout flare should be 
treated symptomatically with analgesics. Xanthine oxidase inhibitors to lower blood and urine uric acid 
levels may affect stone recurrence and are not allowed during the trial. If gouty arthritis recurs > 3 times/ 
year or a uric acid lowering therapy is needed, the IMP will be withdrawn from the patient. 
8.3.4 
Diabetes 
HCTZ may worsen glucose tolerance or induce diabetes mellitus. If overt diabetes mellitus develops 
during the trial (fasting glucose ≥ 7 mmol/L, random glucose ≥ 11 mmol/L or hemoglobin A1c ≥ 6.5%), 
the patient will be asked to see his general practitioner to initiate appropriate treatment. 
8.3.5 
Allergic reactions 
Occasionally allergic reactions of the skin have been observed in patients with HCTZ treatment. If this 
is suspected, the IMP will be withdrawn from the patient. 
8.3.6 
Symptomatic stone recurrence during the trial 
Patients will remain on study treatment with up to three symptomatic stone events. If a fourth 
symptomatic stone event occurs during the trial, the IMP will be withdrawn from the patient. 
 
For additional criteria for discontinuing study IMP treatment or study discontinuation see section 7.4. 
8.4 
Compliance with study intervention 
At initial product dispensing and the follow-up visits, including the three-monthly telephone contacts, the 
participants will be reminded about the following: 
- 
The importance of following the study guidelines, including the non-pharmaceutical preventive 

 
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measures and taking the study product once daily  
- 
Instructions about IMP administration including dose, importance of taking the IMP as a whole, 
timing, and noting done any missed dose, and instructions about proper IMP storage 
- 
Notification that there will be IMP counts performed during the trial 
- 
To keep all medication containers, including any unused capsules and to return them to the study 
site at the next scheduled on-site visit 
- 
That IMP may be HCTZ or placebo 
- 
Importance of calling the clinic if experiencing problems possibly related to the study product such 
as symptoms or lost IMP 
 
At the follow-up visits and three-monthly telephone calls, the participants will be asked about any 
problems with regard to taking the IMP using a structured and open-ended questionnaire. There will be 
a discussion of reasons for missed doses and simple strategies for enhancing adherence, e.g. linking 
IMP taking to meals or other daily activities. Participants will have an opportunity to ask questions and 
key messages from the initial session will be reviewed as needed. 
 
Participants will be asked to return used, partially used and unused IMP containers at each follow-up 
visit at the study sites. 
Depending on the circumstances leading to non-compliance, the subject may be discontinued from IMP 
administration by the investigator and/ or sponsor. A subject who proactively wishes to discontinue IMP 
administration, or has IMP discontinued by the investigator, will be encouraged to continue limited 
participation in the trial, as described in section 7.4.  
8.5 
Data Collection and Follow-up for withdrawn participants  
Participants who permanently discontinue the study treatment are expected to continue in the follow-up 
period and to attend all protocol-specified study visits. If study visits are not possible, a telephone 
consultation will be performed to determine if relevant health events/ endpoints have occurred. 
Participants who are withdrawn from further study participation are invited to attend a final visit at which 
the assessments of the End of Treatment visit are performed. 
8.6 
Trial-specific preventive measures 
Dietary and lifestyle interventions are highly effective in preventing recurrence in calcareous 
nephrolithiasis and are the basis of stone prevention [63]. Any trial assessing pharmacologic 
interventions for the prevention of stone recurrence must compare the efficacy of the drug treatment to 
the state-of-the-art non-pharmacologic interventions. Thus, all patients will receive state-of-the-art non-
pharmacologic recommendations for stone prevention according to current American [31] and European 
[23] nephrolithiasis guidelines including: increased fluid intake with circadian drinking to ensure daily 
urinary volumes of at least 2 – 2.5 L, a balanced diet rich in vegetables and fibers with normal calcium 
content (1-1.2 g/day) but limited NaCl (4-6 g/day) and animal protein (0.8-1 g/kg/day) content. 
Furthermore, patients must be advised to retain a normal BMI, have adequate physical activity and 
balance excessive fluid loss.  
 
The following medications will be prohibited during the trial (reason given in brackets)*: 
- 
Thiazide diuretics (pharmacodynamic interference with IMP) 
- 
Loop diuretics (pharmacodynamics interference with IMP) 
- 
Carbonic anhydrase inhibitors (increase risk for stone recurrence) 
- 
Xanthine oxidase inhibitors (potentially decrease risk of stone recurrence) 
- 
Alkali, including potassium citrate or sodium bicarbonate (potentially decrease risk of stone 
recurrence) 
- 
Treatment with 1,25-OH Vitamin D (increases risk of stone recurrence) 
- 
Calcium supplementation (increases risk of stone recurrence) 
- 
Bisphosphonates (potentially decreases risk of stone recurrence) 
- 
Denusomab (potentially decreases risk of stone recurrence) 
- 
Teriparatide (increases risk of stone recurrence) 
- 
Glucocorticoids (increases risk of stone recurrence) 
 
*a grace period of maximal 4 months will be tolerated (see section 7.4.1) 

 
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8.7 
Concomitant Interventions (treatments)  
Active recurrence prevention for calcareous nephrolithiasis with thiazide diuretics, alkali or xanthine 
oxidase inhibitors will have to be stopped at least 3 months before an individual can be enrolled 
(randomized) in the study. All medications not listed in section 8.6 will be allowed before and during the 
study as concomitant treatments. The use of concomitant medications will be recorded in the eCRF. 
There are no restrictions to medications or treatments after the study. 
All urological interventions related to symptomatic and asymptomatic stone disease are permitted during 
the trial. Generally, it is recommended to follow patients with asymptomatic stones and wait until stones 
become symptomatic. However, the likelihood for the eventual need of an urological intervention 
depends on the stone diameter. Ureteral stones with a diameter > 7 mm have a likelihood of 99% to 
require a urological intervention in the future [68]. Thus, kidney stones with a diameter > 7 mm are often 
removed, even if asymptomatic. In patients with a high risk of complications, including those with a 
solitary kidney or in patients with certain professions (e.g. pilots), even elective removal of asymptomatic 
stones with a diameter ≤ 7 mm may be indicated. Interventional treatment of asymptomatic stones of 
patients enrolled in the trial will be left to the discretion of the treating urologists. Removal of an 
asymptomatic stone will be considered as symptomatic stone event in this trial. 
8.8 
Study Drug Accountability  
The investigator or designee must maintain an inventory record of IMP at the site level (received from 
the sponsor, returned to the sponsor) and at the patient level (dispensed to the patient, returned by the 
patient). 
8.9 
Return or Destruction of Study Drug/ Medical Device  
Upon completion or termination of the trial, all unused IMP must be destructed on site following the site’s 
standard procedures for medication destruction and the destruction documented. Documentation on 
IMP destruction must be provided to the sponsor-investigator for filing in the trial master file. 
9. STUDY ASSESSMENTS  
9.1 
Study flow chart(s)/ table of study procedures and assessments 
For work-up and follow-up of participants, the NOSTONE protocol strictly adheres to recommendations 
of the American and European guidelines on nephrolithiasis [23, 31] with regard to scheduling of patient 
visits, lab analyses and imaging. 
For the schedule of assessments refer to “Study Schedule” table at the beginning of this document. 
9.2 
Assessments of outcomes  
In accordance with recommendations of the American and European guidelines on nephrolithiasis [23, 
31], study participants undergoing first-time work-up for stone disease will be scheduled for Visit 4 (V4), 
unless they are unable to attend the visit in person. Participants with past work-up for stone disease that 
are currently undergoing regular follow-up will omit V4, all other Visits (including numbering of Visits) 
are identical to participants with first-time work-up for stone disease. 
9.2.1 
Assessment of primary outcome 
Symptomatic recurrence (for definition see section 5.1.1) will be assessed at the follow-up visits 3, 4, 5 
and 6 as well as at the three-monthly phone calls in between the visits. 
Radiologic recurrence (for definition see section 5.1.1) will be assessed by low-dose, renal-limited non-
iv contrast CT imaging at visit 3 (defined as reference for stone recurrence during the study), if a stone 
recurrence is suspected during the treatment phase (standard procedure in symptomatic patients 
irrespective of the study), and at treatment end (visit 7 for participants recruited in the first 12 months of 
the recruitment period and visit 6 for participants recruited in the remainder of the recruitment period). 
Stone events occurring during the first 6 weeks after randomization will not be considered as events for 
the analysis. At treatment end, a renal CT is performed only if no other non-iv contrast renal CT was 
performed within 3 months prior to the visit. 

 
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9.2.2 
Assessment of secondary outcomes 
Individual components of the composite primary outcome, i.e. incidence of symptomatic stone 
recurrence and incidence of radiologic stone recurrence will be assessed as described for the primary 
outcome. Changes in urinary biochemistry elicited by the IMP compared to baseline (visit 2) will be 
assessed by chemical analysis of urine samples collected immediately prior to visits 4, 5, 6 and 7 (one 
24 hour collection immediately prior to visit 4; two 24 hours collections within 48 hours immediately prior 
to visits 5, 6 and 7). Impact of baseline disease severity and biochemical abnormalities on stone 
recurrence will be assessed by baseline blood and urine analysis and baseline medical history and 
assessment of the primary outcome as described. If the collection of 48 hour urines is difficult for the 
patient, a single, 24 hour urine collection (with added paraffin/ thymol) can be taken into consideration. 
Chemical blood and urine analysis are only performed at visits 4, 5, 6 and 7 with the explicit (unwritten) 
approval of the patient. If these visits are replaced by a phone call, blood and urine analysis is not 
performed. Impact of stone composition on stone recurrence will be assessed by baseline medical 
history and assessment of the primary outcome as described. 
Given the average stability over time of urine and blood composition in this patients population, the time 
windows outlined in “Study schedule 1” and “Study schedule 2” (pages 11-14) are meant to be indicative, 
not restrictive. 
9.2.3 
Assessment of other outcomes of interest 
Genetic data generated from the DNA stored in the biobank will be used in different biomedical projects 
(e.g genetic markers vs urine/blood analysis; genetic markers vs stone incidence; genetic markers vs. 
treatment response).  
9.2.4 
Assessment of safety outcomes 
9.2.4.1 
Serious adverse events (SAEs) 
SAEs will be collected, fully investigated and documented in the source documents and the eCRF for 
all participants from the date of ICF signature until the last protocol-specific procedure has been 
completed, including a safety follow-up period of 30 days. 
9.2.4.2 
Adverse events (AEs) of special interest 
For this trial, (non-serious) AEs will not be documented in the eCRF with exception of the following 
events “of special interest” occurring from the date of randomizatzion (visit 3) until visit 7: 
- 
Hypokalemia, defined as blood potassium level < 3 mmol/L 
- 
Hyponatremia, defined as blood sodium level < 125 mmol/L 
- 
Hypomagnesemia, defined as blood magnesium level < 0.5 mmol/L 
- 
Gouty arthritis if recurrence > 3 times per year or requiring Uric acid lowering therapy 
- 
Newly developed overt diabetes mellitus (defined as fasting glucose level ≥ 7 mmol/L or random 
Glucose ≥ 11 mmol/L or hemoglobin A1c ≥ 6.5%) 
- 
Allergic reaction of skin if considered by the local investigator to be potentially related to the study 
medication 
9.2.4.3 
Vital signs 
Heart rate, systolic and diastolic blood pressure at the right arm in sitting position after at least 5 minutes 
rest will be recorded at visits 1, 4, 5, 6 and 7. 
9.2.5 
Assessments in participants who prematurely stop the study 
Participants who permanently discontinue the study treatment will undergo all protocol-specified study 
visits and assessments. If study visits are not possible, a telephone consultation will be performed to 
determine if relevant health events/ endpoints have occurred. 
9.3 
Procedures at each visit 
9.3.1 
Visit or phone call 1 (screening day 1*; -1month to day -14) 
- 
Patient information and delivery of written study information to subject 
- 
Pre-assessment of eligibility (based on data available per routine) 
- 
Demographics 
- 
Medical history 
- 
Stone composition (all stones analyzed prior to randomization as available) 
- 
General physical examination, including body weight, height 

 
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- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Concomitant medication 
 
* For participants in current follow-up for past stone disease, all assessments of visit 1 are performed at 
visit 2. For participants with first time work-up for kidney stone disease (new referrals), screening 
assessments should be performed at visits 1 and 2, unless the distribution over 2 visits is impracticable, 
in which case the same procedure as for participants in current follow-up applies. 
9.3.2 
Visit 2 (screening day 2; -14 days to -1 day; window ±2 weeks) 
- 
Written informed consent (if not obtained earlier). Note: In order to give subjects in current follow-
up for past stone disease sufficient time for the decision on study participation, initial patient 
information may be done via phone and the written study information provided to the subject via 
normal post prior to the visit; same for new referrals if they are unable to come extra for Visit 1 
- 
Assessment of eligibility 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit or one 24 hour 
collection in case of impediment; analyzed centrally): sodium, potassium, chloride, calcium, 
magnesium, inorganic phosphate, creatinine, urea, uric acid, protein, albumin, oxalate, citrate, 
ammonium, pH, volume 
- 
Pregnancy test (performed locally, from blood or urine) for women of child-bearing potential 
(defined as women who are not surgically sterilized/ hysterectomized, and/ or who are 
postmenopausal for less than 12 months)  
- 
Assessment of SAEs 
- 
Concomitant medication 
9.3.3 
Visit 3 (day 0) 
- 
Re-assessment of eligibility 
- 
Randomization 
- 
Baseline low-dose non-iv contrast renal CT (analyzed centrally; if a routine non-iv contrast renal 
CT was performed within 2 months prior to this visit, the CT does not have to be repeated) 
- 
Collection of information on composition of any new kidney stone since last visit 
- 
Instruction of participant on non-pharmacologic recommendations for stone prevention 
- 
Dispense of IMP (first intake of IMP on the day after visit 3) 
- 
Assessment of SAEs 
- 
Concomitant medication 
- 
Collection of an additional 2.0 ml of EDTA blood for the NOSTONE biobank. 
9.3.4 
Visit or phone call 4 (+3 months, visit window ±2 weeks) 
Participants with first-time work-up of stone disease: 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Collection of information on composition of any new kidney stone since last visit 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (one 24 hour collection (with added paraffin/ thymol) in the 48 hours immediately 
prior to the visit; analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, protein, albumin, oxalate, citrate, ammonium, pH, volume 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Screening for criteria for interrupting or discontinuing study intervention 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
If not done before, collection of an additional 2.0 ml of EDTA blood for the NOSTONE biobank. 

 
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Participants in current follow-up for past kidney stone disease or participants with first-time work-up of 
stone disease that are unable to come to Visit 4: 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last visit and regarding the potential occurrence of events of special interest as far as known to the 
participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
 
9.3.5 
In between Visits 4 and 5 (+6 and +9 months, visit window ±4 weeks) 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last contact and regarding the potential occurrence of AEs of special interest as far as known to 
the participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Dispense of IMP via normal post 
9.3.6 
Visit or phone call 5 (+12 months, visit window ±4 weeks) 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit or one 24 hour 
collection (with added paraffin/ thymol) in case of impediment; analyzed centrally): sodium, 
potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, urea, uric acid, protein, 
albumin, oxalate, citrate, ammonium, pH, volume 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Screening for criteria for interrupting or discontinuing study intervention 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Dispense of IMP and collection of used/ unused IMP packs from participant 
9.3.7 
If not done before, collection of an additional 2.0 ml of EDTA blood for the NOSTONE 
biobank. In between Visits 5 and 6 (+15, +18 and +21 months, visit window ±4 weeks) 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last contact and regarding the potential occurrence of AEs of special interest as far as known to 
the participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
9.3.8 
Visit or phone call 6 (+24 months, visit window ±4 weeks) 
Participants recruited ≥ 12 months after start of the recruitment period: 
Patients recruited ≥ 12 months after start can stay in the trial up to 36 months same as for the patients 
enrolled during the first 12 months. They will follow the regular schedule as the participants enrolled 
during the first 12 months. However, the end of treatment visit (V7) is flexible and will take place between 
the months 24 and 36.  
 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit or one 24 hour 

 
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collection (with added paraffin/ thymol) in case of impediment; analyzed centrally): sodium, 
potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, urea, uric acid, protein, 
albumin, oxalate, citrate, ammonium, pH, volume 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
- 
Screening for criteria for interrupting or discontinuing study intervention 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Dispense of IMP and collection of used/ unused IMP packs from participant 
- 
If not done before, collection of an additional 2.0 ml of EDTA blood for the NOSTONE biobank. 
For participants that terminate their treatment period with visit 6 (“Study schedule 2”, p.13-14): if 
this visit is replaced by a phone call, the patient must receive an appointment for the CT scan 
anyway (unless this has been performed within 2 months prior to this visit), and the stone 
assessment must be performed by phone.  
 
Participants recruited ≥ 12 months of the recruitment period that stop treatment after 24 months: 
- 
Low-dose non-iv contrast renal CT (analyzed centrally; if a routine non-iv contrast renal CT was 
performed within 2 months prior to this visit, the CT does not have to be repeated) 
 
9.3.9 
In between Visits 6 and 7 (+27, +30 and +33 months, visit window ±4 weeks) 
 
- 
Telephone call to ask participant about possible trial-related problems (including any SAEs since 
last contact and regarding the potential occurrence of AEs of special interest as far as known to 
the participant) and answer any questions from participant 
- 
Assessment of symptomatic stone recurrence 
- 
Compliance reminder (intake of IMP and adherence to non-pharmacologic recommendations for 
stone prevention) 
9.3.10 Visit or phone call 7 (+36 months, visit window ±4 weeks) 
 
- 
General physical examination, including body weight 
- 
Vital signs (heart rate, systolic and diastolic blood pressure at the right arm after at least 5 minutes 
at rest) 
- 
Blood analysis (analyzed centrally): sodium, potassium, chloride, calcium, magnesium, inorganic 
phosphate, creatinine, urea, uric acid, bicarbonate, PTH, 25-OH Vitamin D, 1,25-OH Vitamin D, 
glucose (fasting), hemoglobin A1c, cholesterol, alkaline phosphatase) 
- 
Urine analysis (two 24 hour collections in the 48 hours immediately prior to the visit or one 24 hour 
collection (with added paraffin/ thymol) in case of impediment; analyzed centrally): sodium, 
potassium, chloride, calcium, magnesium, inorganic phosphate, creatinine, urea, uric acid, protein, 
albumin, oxalate, citrate, ammonium, pH, volume 
- 
Low-dose non-iv contrast renal CT (analyzed centrally; if a routine non-iv contrast renal CT was 
performed within 2 months prior to this visit, the CT does not have to be repeated) 
- 
Assessment of symptomatic stone recurrence 
- 
Assessment of SAEs and AEs of special interest 
- 
Concomitant medication 
- 
Collection of used/ unused IMP packs from participant 
- 
If not done before, collection of an additional 2.0 ml of EDTA blood for the NOSTONE biobank. 
- 
If this visit is replaced by a phone call, the patient must receive an appointment for the CT scan 
anyway (unless this has been performed within 2 months prior to this visit), and the stone 
assessment must be performed by phone. 
 
9.3.11 Safety follow-up (30 days after end of treatment, visit window ±2 weeks) 
- 
Assessment of SAEs (telephone call) 
9.3.12 Study-specific procedures 
The following procedures are study-specific: 
- 
Pregnancy test for women of child-bearing potential at visit 2 

 
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Probably 
Temporal relationship 
Improvement after dechallenge 
No other cause evident 
Possibly 
Temporal relationship 
Other cause possible 
Unlikely 
Any assessable reaction that does not fulfil the above conditions 
Not related 
Causal relationship can be ruled out 
*Improvement after dechallenge only taken into consideration, if applicable to reaction 
 
10.1.2 Unexpected Adverse Drug Reaction 
An “unexpected” adverse drug reaction is an adverse reaction, the nature or severity of which is not 
consistent with the applicable product information (e.g. Investigator’s Brochure for drugs that are not yet 
approved and Product Information for approved drugs, respectively). ICH E2A 
10.1.3 Suspected unexpected serious adverse reactions (SUSARs) 
The Sponsor-Investigator evaluates any SAE that has been reported regarding seriousness, causality 
and expectedness. If the event is related to the investigational product and is both serious and 
unexpected, it is classified as a SUSAR. Unblinding will be needed in order to determine a SUSAR. 
10.1.4 Assessment of Severity 
Classification and severity grading scale of SAEs and AEs of special interest (see section 9.2.4.2) in 
this study will be performed in accordance with “Common Terminology Criteria for Adverse Events 
CTCAE Version 4.03” terminology. 
10.2 Reporting of serious adverse events (SAE) and other safety-related events  
Reporting of SAEs 
All SAEs must be reported immediately and within a maximum of 24 hours of learning of its occurrence 
to the Sponsor-Investigator of the study via the SAEreport form on secuTrial. 
 
The Sponsor-Investigator will re-evaluate the SAE on secuTrial. 
SAEs resulting in death will be reported to the coordinating and, if applicable, to the local Ethics 
Committee within 7 days. 
 
Non-serious Events that require discontinuation of IMP 
Non-serious events that require discontinuation of IMP (including laboratory abnormalities – see section 
7.4.1) should be reported to the Sponsor-Investigator within 3 days. 
 
Reporting of SUSARs 
A SUSAR needs to be reported to the local Ethics Committee (via Sponsor-Investigator) and to 
Swissmedic (via Sponsor-Investigator) within 7 days, if the event is fatal, or within 15 days (all other 
events). 
The Sponsor-Investigator must inform all Investigators participating in the clinical study of the 
occurrence of a SUSAR. All in the trial involved Ethics Committees will be informed about SUSARs in 
Switzerland via Sponsor-Investigator according to the same timelines. 
 
Reporting of Safety Signals 
All suspected new risks and relevant new aspects of known adverse reactions that require safety-related 
measures, i.e. so called safety signals, must be reported to the Sponsor-Investigator within 24 hours. 
The Sponsor-Investigator must report the safety signals within 7 days to the local Ethics Committee and 
to Swissmedic. The Sponsor-Investigator must immediately inform all participating Investigators about 
all safety signals. The other in the trial involved Ethics Committees will be informed about safety signals 
in Switzerland via the Sponsor-Investigator. 
 
Reporting and Handling of Pregnancies 
Pregnant participants must immediately discontinue IMP. Any pregnancy during the treatment phase of 
the study and within 30 days after discontinuation of IMP must be reported to the Sponsor-Investigator 
within 24 hours. The course and outcome of the pregnancy will be followed up carefully and any 
abnormal outcome regarding the mother or the child should be documented and reported. 

 
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Periodic reporting of safety 
An annual safety report will be prepared and submitted once a year to the local Ethics Committees and 
to Swissmedic by the Sponsor-Investigator. The annual safety report will contain information from all 
study sites. 
10.3 Follow up of (serious) adverse events 
Participants with any reported ongoing SAE at the last scheduled study contact will be followed until 
resolution of the event or a stabilized condition of the subject has been achieved or until the subject is 
lost to follow-up. 
Any new SAEs the Investigator gets aware of that occur after the last scheduled study contact and are 
determined by the Investigator to be reasonably associated with the use of the IMP, should be reported 
to the Sponsor-Investigator. The Investigator should follow potentially IMP-related SAEs identified after 
the last scheduled contact (and report any significant follow-up information to the Sponsor-Investigator) 
until the events are resolved or stabilized, or the subject is lost to follow-up. 
11. STATISTICAL METHODS  
11.1 Hypothesis 
The null hypothesis that there is no linear trend between dose and the survival function for the primary 
outcome (i.e. recurrence) will be tested against the alternative that there is a linear trend. 
11.2 Determination of Sample Size  
The sample size calculation was based on the primary objective i.e. to assess the dose-response 
relationship and the primary outcome i.e. recurrence with the following assumptions: 
 
Uniform recruitment over 24 months with allocation ratio fixed at 1 across all arms. 
 
A maximum and minimum follow-up time of 36 and 24 months, respectively. 
 
A cumulative drop-out rate of 10% at 24 months after study start. 
 
Based on the available literature we assumed a risk of recurrence in the placebo group of 0.20 
and 0.45 at 12 and 36 months after study start, respectively. 
 
Hazard ratios for the 12.5, 25 and 50 mg HCTZ doses of 0.90, 0.65 and 0.50, respectively. These 
effects were based on the literature review presented in Table 3.1-1. 
 
Power was set to be at least 80% and alpha was fixed at a two-sided level of 0.05.  
 
An unweighted log-rank test for linear trend with local alternatives. 
 
Using the command artsurv in Stata we calculated that we will need to recruit 416 patients i.e. 104 in 
each arm. 
11.3 Statistical criteria of termination of trial  
Not applicable as no formal interim analysis is planned. 
11.4 Planned Analyses  
The statistical analysis of the trial will be done at CTU Bern by a statistician blinded to the allocation. 
This process is defined in standard operating procedures. After start of the trial but before recruitment 
ends, a statistical analysis plan will be written. The plan will determine all necessary data preparation 
steps (e.g. additional validations, generation of new variables), definitions (e.g. analysis sets), and 
statistical analyses (e.g. models, outputs such as tables and graphs).  
All statistical analyses will be presented as effect measure plus 95% confidence interval. A significance 
level of 5% will be used. 
11.4.1 Datasets to be analysed, analysis populations 
All analyses will be done on the intention-to-treat analysis set whereby all randomized patients will be 
analyzed in the allocated group regardless of any protocol violations such as cross-overs (which can 

 
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only happen accidently in this trial) or early treatment discontinuations. 
11.4.2 Primary Analysis 
The primary outcome (time to stone event) will be analyzed using a stratified log-rank test for linear 
trend with the hazard ratio as primary effect measure. The test addresses the primary objective of the 
trial i.e. test for any dose-response relationship. We will start with testing for a linear relationship but will 
also consider more complex relationships by using fractional polynomials. Kaplan-Meier curves will be 
used to present results on the primary outcome graphically. In case of a relevant number of multiple 
events within patients we will consider a model for recurrent events. 
Components of the primary outcome measure (clinical and radiological recurrences represented by the 
number of stones during the trial or time to exclusion from study due to too many stones) will be analyzed 
similar to the primary analysis (for counts using frailty (count) or marginal count model). 
Continuous secondary outcomes (changes in urinary biochemistry) will be analyzed using mixed effects 
model. Comparisons between placebo and the three active trial arms will be considered exploratory as 
the trial is not powered to detect differences there. 
11.4.3 Secondary Analyses 
The following baseline characteristics were identified to potentially modify the expected treatment 
effect: 
- 
Baseline disease severity (Highest vs. lowest tertile in stone frequency prior to study entry)  
- 
Biochemical abnormalities (Hypercalciuria vs. no hypercalciuria) 
- 
Stone composition (pure CaOx vs. pure CaP vs. mixed CaOx/ CaP vs. mixed CaOx/ UA) 
These characteristics will be used for stratified analyses. All stratified analyses will be accompanied by 
tests for interaction. 
11.4.4 Interim analyses 
No formal interim analysis is planned. 
11.4.5 Safety analysis 
Safety endpoints to be analyzed include a descriptive summary of pre-specified AEs of special interest 
and vital signs. No formal statistical testing will be applied. 
11.4.6 Deviation(s) from the original statistical plan  
Deviations from the statistical analysis plan will be stated and justified in the final analysis report. 
11.5 Handling of missing data and drop-outs  
For the primary outcome, drop-outs will be censored at the last available visit. Missing data for 
continuous outcomes will be handled by multiple imputation. 
12. QUALITY ASSURANCE AND CONTROL  
12.1 Data handling and record keeping/ archiving  
The Investigators will maintain appropriate medical and research records for this trial, in compliance 
with ICH-GCP and regulatory and institutional requirements for the protection of confidentiality of 
subjects. The Principal Investigator, Sub-investigator, and Clinical Research Nurses or Coordinators will 
have access to the records. The Principal Investigators will permit authorized representatives of the 
Sponsor and regulatory agencies to examine clinical records for the purposes of quality assurance 
reviews, audits, and evaluation of the study safety and progress.  
12.1.1 Case Report Forms  
The CRF will be electronic. All data requested on the eCRF must be recorded and the recorded data 
should be consistent with the source documents or the discrepancies should be explained. The 
Investigator should ensure the accuracy, completeness, and timeliness of the data reported in the eCRF 
and all other required reports. Generally, the eCRF should be completed within two weeks of completion 

 
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of a participant’s visit/ follow-up phone call. 
12.1.2 Specification of source documents  
Source documents must be available at the site to document the existence of the study participants and 
must include the original documents relating to the study, as well as the medical treatment and medical 
history of the participant. 
For all data captured in the eCRF, the location of the source should be documented on a list of source 
documents (source data location list), which will be stored in the investigator site file at each study site. 
If certain data are directly entered into the eCRF (and are thus considered as source data) this must be 
specified on the source data location list accordingly. 
Any change or correction to source data should be dated, initialed, and explained (if necessary) and 
should not obscure the original entry.  
12.1.3 Record keeping/ archiving  
All study data (written and electronic), including any images, must be retained for a period of at least 10 
years from the completion or premature termination of the trial. The Investigators should take measures 
to prevent accidental or premature destruction of these documents. 
12.2 Data management  
12.2.1 Data Management System  
The CRFs in this trial are implemented electronically using a dedicated electronic data capturing (EDC) 
system (secuTrial®). The EDC system is activated for the trial only after successfully passing a formal 
test procedure. All data entered in the eCRF are stored on a Linux server in a dedicated Oracle database. 
Responsibility for hosting the EDC system and the database lies with Inselspital Bern. 
12.2.2 Data security, access and back-up  
The server hosting the EDC system and the database is kept in a locked server-room. Only the system 
administrators have direct access to the server. A role concept with personal passwords (site 
investigator, statistician, monitor, administrator etc.) regulates permission for each user to use the 
system and database as he/ she requires. 
All data entered into the eCRF are transferred to the database using Secure Sockets Layer (SSL) 
encryption. Each data point has attributes attached to it identifying the user who entered it with the exact 
time and date. Retrospective alterations of data in the database are recorded in an audit table. Time, 
table, data field and altered value, and the person are recorded (audit trail). A multi-level back-up system 
is implemented.  
12.2.3 Analysis and archiving 
At interim (if applicable) and final analyses, data files will be extracted from the database into statistical 
packages to be analyzed. The status of the database at this time is recorded in special archive tables. 
The study database with all archive tables will be securely stored by Inselspital Bern. The sponsor also 
keeps the Trial Master File and interim and final reports both in electronic and in hard copy form for at 
least 10 years. 
12.2.4 Electronic and central data validation  
Data is checked by the EDC system for completeness and plausibility. Furthermore, selected data points 
are cross-checked for plausibility with previously entered data for that participant. In addition (if 
applicable), central data reviews will be performed on a regular basis to ensure completeness of the 
data collected and accuracy of the primary outcome data. 
12.3 Monitoring  
For quality control of the study conduct and data retrieval, all study sites will be visited on-site by 
appropriately trained and qualified Monitors. Any findings and comments will be documented in site visit 
reports and communicated to the local Investigator and to the Sponsor as applicable. Investigators at 
the participating study sites will support the Monitor in his/ her activities. Prior to study start (first 
participant enrolled) a plan detailing all monitoring-related procedures will be developed. 
All source data and relevant documents will be accessible to Monitors and questions of Monitors are 
answered during site visits.  

 
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12.4 Audits and Inspections  
Source data/ documents must be available to audits by the Sponsor or designee or to inspections by 
health authorities. The CA (Swissmedic) or CEC may wish to conduct an inspection (during the study 
or after its completion). If an inspection is requested, the Investigator must inform the Sponsor 
immediately that this request has been made. The Investigators at the participating sites will support the 
inspectors in their activities and will answer questions from inspectors as needed. All involved parties 
must keep the participant data strictly confidential. 
12.5 Confidentiality, Data Protection  
The Investigator ensures anonymity of the patients; patients will not be identified by names in any study 
documents leaving the study site. Subject confidentiality will be ensured by utilizing subject identification 
codes consisting of three random letters and three random numbers, such as toj838. Signed informed 
consent forms and patient enrollment log will be kept strictly confidential to enable patient identification 
at the site. 
12.6 Storage of biological material and related health data  
All baseline and follow-up CTs for central analysis will be coded and uploaded into the picture archiving 
and communication system (PACS) of the Inselspital. A secure exchange platform will be used for file 
exchange. 
DNA collected from patients will be stored indefinitely in the NOSTONE Biobank at the Bern University 
Hospital. The samples will not be destroyed at the end of the study. Patient’s samples and genetic data 
will be stored only after a separate informed consent is signed. 
The procedures and rules of the NOSTONE biobank are described in a specific booklet (NOSTONE 
Biobank Reglement). 
 
 
13. PUBLICATION AND DISSEMINATION POLICY  
The trial protocol will be published in an open access journal. Study results will be presented at national 
and international meetings and will be submitted for publication to high impact, peer reviewed journals. 
Upon completion of the analysis, trial results will be communicated to all participants. Public reporting 
will be done through patient organizations and via the communication Departments at the individual 
Universities and Hospitals.  
Once results have been published, trial data will be accessible to external researchers and anonymized 
datasets corresponding to each publication will be made available. Investigators wishing to replicate the 
analyses or to do an individual patient meta-analysis may request the data from the steering committee. 
Access to data will be granted in an unbureaucratic way. 
14. FUNDING AND SUPPORT  
14.1 Funding 
This trial trial is financed by the Swiss National Science Foundation via the “Investigator-initiated clinical 
trials – IICT” grant # 33IC30_166785. 
14.2 Other Support 
The trial will also receive intramural support of the Bern University Hospital. 

 
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15. INSURANCE  
Insurance will be provided by the Sponsor. A copy of the certificate is filed in each investigator site file 
and the trial master file. 
16. REFERENCES 
1. 
Scales CD, Jr., Smith AC, Hanley JM, et al. Prevalence of kidney stones in the United States. 
Eur Urol. 2012;62:160-165. 
2. 
Romero V, Akpinar H, Assimos DG. Kidney stones: a global picture of prevalence, incidence, 
and associated risk factors. Rev Urol. 2010;12:e86-96. 
3. 
Worcester EM, Coe FL. Clinical practice. Calcium kidney stones. N Engl J Med. 2010;363:954-
963. 
4. 
Uribarri J, Oh MS, Carroll HJ. The first kidney stone. Ann Intern Med. 1989;111:1006-1009. 
5. 
Saigal CS, Joyce G, Timilsina AR. Direct and indirect costs of nephrolithiasis in an employed 
population: opportunity for disease management? Kidney Int. 2005;68:1808-1814. 
6. 
Lotan Y, Cadeddu JA, Roerhborn CG, et al. Cost-effectiveness of medical management 
strategies for nephrolithiasis. J Urol. 2004;172:2275-2281. 
7. 
Parks JH, Worcester EM, Coe FL, et al. Clinical implications of abundant calcium phosphate in 
routinely analyzed kidney stones. Kidney Int. 2004;66:777-785. 
8. 
Parks JH, Coe FL. The financial effects of kidney stone prevention. Kidney Int. 1996;50:1706-
1712. 
9. 
Sakhaee K, Maalouf NM, Kumar R, et al. Nephrolithiasis-associated bone disease: 
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10. 
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11. 
Rule AD, Bergstralh EJ, Melton LJ, 3rd, et al. Kidney stones and the risk for chronic kidney 
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12. 
Taylor EN, Stampfer MJ, Curhan GC. Diabetes mellitus and the risk of nephrolithiasis. Kidney 
Int. 2005;68:1230-1235. 
13. 
Taylor EN, Stampfer MJ, Curhan GC. Obesity, weight gain, and the risk of kidney stones. Jama. 
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14. 
Madore F, Stampfer MJ, Willett WC, et al. Nephrolithiasis and risk of hypertension in women. 
Am J Kidney Dis. 1998;32:802-807. 
15. 
Madore F, Stampfer MJ, Rimm EB, et al. Nephrolithiasis and risk of hypertension. Am J 
Hypertens. 1998;11:46-53. 
16. 
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17. 
Daudon M, Bouzidi H, Bazin D. Composition and morphology of phosphate stones and their 
relation with etiology. Urol Res. 2010;38:459-467. 
18. 
Pak CY, Britton F, Peterson R, et al. Ambulatory evaluation of nephrolithiasis. Classification, 
clinical presentation and diagnostic criteria. Am J Med. 1980;69:19-30. 
19. 
Worcester EM, Coe FL. New insights into the pathogenesis of idiopathic hypercalciuria. Semin 
Nephrol. 2008;28:120-132. 
20. 
Coe FL, Evan A, Worcester E. Kidney stone disease. J Clin Invest. 2005;115:2598-2608. 
21. 
Worcester EM, Gillen DL, Evan AP, et al. Evidence that postprandial reduction of renal calcium 
reabsorption mediates hypercalciuria of patients with calcium nephrolithiasis. Am J Physiol 
Renal Physiol. 2007;292:F66-75. 
22. 
Coe FL, Favus MJ, Crockett T, et al. Effects of low-calcium diet on urine calcium excretion, 
parathyroid function and serum 1,25(OH)2D3 levels in patients with idiopathic hypercalciuria 
and in normal subjects. Am J Med. 1982;72:25-32. 
23. 
European Association of U, Turk C, Knoll T, et al.: EUA Guidelines on Urolithiasis, in, 2014 
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Reid IR, Ames RW, Orr-Walker BJ, et al. Hydrochlorothiazide reduces loss of cortical bone in 
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25. 
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26. 
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27. 
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28. 
Parks JH, Goldfisher E, Asplin JR, et al. A single 24-hour urine collection is inadequate for the 
medical evaluation of nephrolithiasis. J Urol. 2002;167:1607-1612. 
29. 
Nayan M, Elkoushy MA, Andonian S. Variations between two 24-hour urine collections in 
patients presenting to a tertiary stone clinic. Can Urol Assoc J. 2012;6:30-33. 
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31. 
Pearle MS, Goldfarb DS, Assimos DG, et al. Medical management of kidney stones: AUA 
guideline. The Journal of urology. 2014;192:316-324. 
32. 
Kennish SJ, Bhatnagar P, Wah TM, et al. Is the KUB radiograph redundant for investigating 
acute ureteric colic in the non-contrast enhanced computed tomography era? Clin Radiol. 
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33. 
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versus intravenous pyelography in the diagnosis of suspected acute urolithiasis: a meta-
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34. 
Niemann T, Kollmann T, Bongartz G. Diagnostic performance of low-dose CT for the detection 
of urolithiasis: a meta-analysis. AJR Am J Roentgenol. 2008;191:396-401. 
35. 
Kluner C, Hein PA, Gralla O, et al. Does ultra-low-dose CT with a radiation dose equivalent to 
that of KUB suffice to detect renal and ureteral calculi? J Comput Assist Tomogr. 2006;30:44-
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36. 
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37. 
Assimos DG, Chew BEN, Hatch M, et al. Evaluation of the stone former. Stone Disease. 
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42. 
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indapamide, in preventing calcium stone recurrences. J Cardiovasc Pharmacol. 1993;22 Suppl 
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45. 
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idiopathic kidney stones. Int Urol Nephrol. 1986;18:265-269. 
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patients with idiopathic hypercalciuria. Br J Urol. 1992;69:571-576. 
48. 
Wilson DR, Strauss AL, Manuel MA: Comparison of medical treatments for the prevention of 
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SCIENCE INC 350 MAIN ST, MALDEN, MA 02148, 1984, pp 994-994 
49. 
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51. 
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17. APPENDICES 
Not applicable. 

 
 
 
 
 
 
 
 
 
Revision history 

NOSTONE Protocol Amendments 
 
Revision history 
Protocol 
version 
Justification  
Timing  
1.0 
First (original) version 
30.08.2016 
1.1 
− 
Revision of the handling of collected data and 
samples upon participant withdrawal §7.4.2 
− 
Revision of confidentiality and data protection 
§12.5  
26.09.2016 
1.2 
− 
Addition of 4 new clinical sites (Synopsis) 
− 
Revision of unblinding procedures §6.3 
− 
Revision of exclusion criteria (inflammatory 
bowel disease and intestinal surgery) §7.1 
− 
Harmonization of number of recurrences for 
IMP stop (= 3) for consistency within the text 
§7.4.1 
− 
Adaptation of the blood parameters for diabetes 
mellitus diagnosis §8.3.4 & 9.2.4.2 
− 
Investigational Medicinal Product (IMP) count 
eliminated §8.4 
− 
IMP dispensing specifications eliminated §9.3 
− 
Revision of kidney stone hospitalization within 
the SAE definition §10.1 
− 
SAE reporting changed from email/fax to 
electronic §10.2 
− 
Margin for eCRF completion extended from 1 
to 2 weeks §12.1.1 
20.2.2017 
1.3 
− 
Hyperthyroidism eliminated from exclusion 
criteria §7.1 
− 
CKD-EPI eGFR definition for CKD changed to 
“< 30 mL/min per 1,73 m2 body surface area 
for more than 3 months” §7.1 
− 
Revision of conditions for IMP discontinuation 
upon concomitant forbidden medication intake 
§7.4.1 
12.5.2017 
1.4 
− 
Revision of conditions for discontinuation of 
study IMP/ discontinuation of forbidden 
medications §7.4.1 
− 
Grace period of maximal 4 months for 
forbidden medications introduced §8.6 
14.08.2017 
1.5 
− 
Study duration and study schedule adapted 
(Synopsis) 
18.04.2018 

− 
Revision of follow-up duration (Study 
schedule, §6.1, §§9.3.8 - 9.3.10, ) 
− 
Revision of unblinding procedure (no 
unblinding envelopes at study sites) §6.1 
1.6 
− CTU Bern, address change §1.3, §1.5 
− Introduction of sampling for DNA biobank: 
• 
Informed consent DNA biobank §2.7 
• 
Other outcomes of interest §5.3 
• 
Assessment of other outcomes of interest 
§9.2.3 
• 
Visits procedures §9.3 
− Unblinding procedures clarified §6.2.2 
− Condition “Blood creatinine > 150% of 
creatinine value at screening (visit 2) for IMP 
discontinuation eliminated §7.4.1 
− Condition for IMP withdraw “The IMP will be 
withdrawn if CKD-EPI eGFR drops below 30 
mL/min per 1,73 m2 body surface area for more 
than 3 months ” introduced in §8.3.2 
− Condition “Stone events occurring during the 
first 6 weeks after randomization will not be 
considered as events for the analysis” 
introduced in §9.2.1 
− “Blood creatinine > 150% of baseline 
creatinine” eliminated from AE of special 
interest §9.2.4.2 
02.06.2018 
1.7 
• 
Revision of inclusion criteria “Recurrent kidney 
stone disease (≥ 2 stone events within the last 
10 calendar years prior to randomization)” 
(Synopsis, §3.8, §6.1.1, §7.1) 
− 
Extension of study duration to 08/2021 
(Synopsis) 
− 
Revision of study schedule  
• 
Possibility to substitute Visit 1 with a 
phone call (Synopsis, §9.2, §9.3); 
• 
Possibility to merge Visit 1 and Visit 2 also 
for new referrals (Synopsis, §9.2, §9.3); 
• 
Possibility to skip lab analysis at Visit 4, 
Visit 5, Visit 6 and Visit 7 on patient’s 
request (Synopsis, §9.2, §9.3); 
• 
Possibility to replace Visits 4-7 with a 
phone call, provided the final CT scan is 
done on site (Synopsis, §9.2, §9.3) 
− 
Adaptation Esidrex® patent owner address §3.2 
− 
Revision of the definition of the primary and 
secondary outcome §3.1 & §3.2 
28.11.2019 

− 
Revision of recruitment timeline §6.1 
− 
“Magnesium” implemented in forbidden 
medications for electrolyte disturbances §8.3.1 
− 
Revision of action to take in case of new onset 
diabetes §8.3.4 
− 
Harmonization of rules for “Symptomatic stone 
recurrence during the trial” §8.3.6 
 

 
 
 
 
 
 
 
 
 
First/original SAP 
Version 1.0 
November 6th, 2018 

 
 
 
 
 
 
 
 
 
Last/final SAP 
Version 4.0 
November 11th, 2021 

 
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SAP for: NOSTONE 
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Valid from: 06.11.2018  
Page 3 of 30 
 
− 
Radiologic recurrence will be analyzed both as 
a binary outcome (i.e. yes/no) as well as a 
count outcome, but not as a time to event out-
come. 
− 
Changes in urinary biochemistry : If the timing 
of urinary analysis is highly variable among pa-
tients, we will not consider time as a discrete 
but as a continuous variable. 
3.0 
Definition of the PP population 
The following issues are not considered anymore 
as major protocol deviations: 
 
− 
Failure to perform primary endpoint assess-
ment, i.e. assessment not done.  
We will only remove patients who didn’t perform 
any visit/call: patients for whom neither the oc-
currence of symptomatic events nor the occur-
rence of radiological stone events have been 
assessed. 
 
− 
Missing treatment doses: we will use inverse 
probability censoring weighting methods to deal 
with non-compliance. 
3.5.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
 
 
 
3.0 up-
dated in 
4.0 
Derivation & analysis of the primary outcome 
1. Derivation  
Symptomatic events occurring more than 3 months 
after the end-of-study CT, will not be considered for 
the analysis 
Radiological results will only be used for analysis 
when the baseline CT was performed in a window 
of +/- 3 months around the randomization date, and 
the end-of-study CT less than 3 months after the 
last visit. 
In case of radiological recurrence, we will assume 
the date of the event to be equal to the date of the 
last performed visit or, if earlier, to the date of the 
end-of-study CT+3 months.  
In cases where no symptomatic stone events are 
reported and the radiological stone recurrence is 
not assessed (e.g. because of no CT performed at 
the end of study) we will use different strategies.  
- 
For the main analysis we will assume that, 
at the time of censoring no radiological 
stone occurred  
- 
In a first sensitivity analysis, we will assume 
the occurrence of a radiological stone 1h 
before censoring (i.e., worst case scenario)  
3.5.2021 updated on 9.11.21 
Data still blinded; change imple-
mented without inspection of 
data 

 
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Page 4 of 30 
 
- 
In a second sensitivity analysis we will re-
move all the patients without a radiological 
stone assessment. 
3.0 
2. Analysis  
Instead of reporting the hazard ratios between dos-
age groups using the Cox proportional hazards 
model, we will calculate rate ratios with the Mantel–
Cox method.  
3.5.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
4.0 
 
Derivation of the secondary outcomes 
Radiological results will only be used for analysis 
when the baseline CT was performed in a window 
of +/- 3 months around the randomization date, and 
the end-of-study CT less than 3 months after the 
last visit. 
Symptomatic events occurring more than 3 months 
after the end-of-study CT, will not be considered for 
the analysis 
The number of radiologic stone recurrence will be 
approximated by the number of new radiological 
stones. 
For the biochemical outcomes, we will use the re-
sults of the 24 h urines collected with thymol and 
paraffin oil (i.e., oil measurements). 
9.11.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
3.0 
Sensitivity analysis  
The primary outcome (i.e., occurrence of any symp-
tomatic or radiologic stone recurrence yes/no) will 
be analyzed as a binary outcome in a sensitivity 
analysis. 
3.5.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
4.0 
For the primary outcome as well as for the number 
of symptomatic stone events we will present a 
Kaplan-Meier curve including the events occurring 
in the first 6 weeks of the study and perform a land-
mark analysis at the 6 weeks landmark point. 
9.11.2021 
Data still blinded; change imple-
mented without inspection of 
data 
4.0 
Definition 
Diabetes is defined as the occurrence of HbA1c 
6.5% or higher; or treated (oral or sc antidiabetic or 
insulin). 
9.11.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
 
 
 

 
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Contents 
1 
Introduction ....................................................................................................................... 9 
1.1 
Background and rationale ................................................................................................... 9 
1.2 
Objectives ......................................................................................................................... 10 
1.2.1 
Primary objective ............................................................................................................... 10 
1.2.2 
Secondary objectives ........................................................................................................ 10 
1.2.3 
Safety objectives ............................................................................................................... 10 
2 
Study methods ................................................................................................................ 10 
2.1 
Trial design ........................................................................................................................ 10 
2.2 
Randomization .................................................................................................................. 10 
2.3 
Sample size ....................................................................................................................... 11 
2.4 
Framework ........................................................................................................................ 11 
2.5 
Statistical interim analyses and stopping guidance ........................................................... 11 
2.6 
Timing of final analysis ...................................................................................................... 11 
2.7 
Timing of outcome assessments ....................................................................................... 12 
2.7.1 
Participants recruited in the first 12 months of the recruitment period .............................. 12 
2.7.2 
Participants recruited ≥ 12 months after recruitment start ................................................. 12 
2.8 
Blinding ............................................................................................................................. 12 
3 
Data management ........................................................................................................... 13 
3.1 
Data export ........................................................................................................................ 13 
3.2 
Data validation .................................................................................................................. 13 
3.3 
Data preparation ............................................................................................................... 13 
3.3.1 
Categorization of data ....................................................................................................... 13 
3.4 
Outcome derivation ........................................................................................................... 14 
3.5 
Data sharing (if applicable) ............................................................................................... 16 
4 
Statistical principles ....................................................................................................... 16 
4.1 
Confidence intervals and P values ..................................................................................... 16 

 
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4.2 
Analysis populations ......................................................................................................... 16 
4.2.1 
Full analysis set (FAS) ...................................................................................................... 16 
4.2.2 
Per-protocol (PP) .............................................................................................................. 16 
4.2.3 
Dealing with non-compliance: ........................................................................................... 16 
4.2.4 
Safety population .............................................................................................................. 17 
4.3 
Estimands.......................................................................................................................... 17 
4.3.1 
Treatment policy estimand ................................................................................................ 17 
4.3.2 
Additional estimands ......................................................................................................... 18 
5 
Trial Population ............................................................................................................... 18 
5.1 
Screening data .................................................................................................................. 18 
5.2 
Eligibility ............................................................................................................................ 18 
5.3 
Recruitment ....................................................................................................................... 19 
5.4 
Baseline patient characteristics ......................................................................................... 20 
5.5 
Adherence and protocol deviations ................................................................................... 21 
5.6 
Withdrawal/follow-up ......................................................................................................... 22 
6 
Analysis ........................................................................................................................... 22 
6.1 
Outcome definitions........................................................................................................... 22 
6.1.1 
Primary outcome ............................................................................................................... 22 
6.1.2 
Secondary outcomes ......................................................................................................... 23 
6.1.3 
Assessment of safety outcomes ........................................................................................ 24 
6.1.4 
Assessments in participants who prematurely stop the study ........................................... 24 
6.2 
Analysis methods .............................................................................................................. 24 
6.2.1 
Primary analysis ................................................................................................................ 24 
6.2.1.1 Secondary outcomes ......................................................................................................... 25 
6.2.2 
Secondary analyses .......................................................................................................... 25 
6.2.3 
Sensitivity analyses ........................................................................................................... 26 
6.2.4 
Subgroup analyses ............................................................................................................ 26 
6.2.5 
Additional analyses ........................................................................................................... 26 

 
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6.2.6 
Causal inferences for PP analysis ..................................................................................... 27 
6.2.7 
Assessment of statistical assumptions .............................................................................. 27 
6.3 
Interim analyses ................................................................................................................ 28 
6.4 
Missing data ...................................................................................................................... 28 
6.5 
Harms ................................................................................................................................ 28 
6.6 
Statistical software ............................................................................................................ 28 
6.7 
Quality control ................................................................................................................... 28 
6.8 
Changes from the protocol ................................................................................................ 29 
6.9 
References ........................................................................................................................ 30 
 
 
 
 

 
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1 
Introduction  
1.1 
Background and rationale  
Background: Nephrolithiasis is a global healthcare problem with a current lifetime risk of 18.8% in men 
and 9.4% in women. Without specific treatment, 5- and 20-year recurrence rates are 40% and 75%, 
respectively. About 80–90% of stones are composed of calcium oxalate with various admixtures of cal-
cium phosphate. Increased excretion of calcium in the urine, hypercalciuria, is the most common meta-
bolic abnormality encountered in patients with recurrent nephrolithiasis. Thiazide diuretics have been 
the cornerstone of pharmacologic metaphylaxis for more than 40 years. The effect of thiazides to reduce 
the risk of stone recurrence has been attributed to their ability to decrease urinary calcium excretion. 
However, other factors, such as reduction of urinary pH and urinary oxalate excretion, probably contrib-
ute to this effect. Efficacy of thiazides on recurrence prevention of calcareous nephrolithiasis was tested 
in 11 randomized controlled trials (RCTs). With the exception of two trials, thiazides significantly reduced 
stone recurrence. Most of these trials are from the 1980’s and 90’s and the cumulative number of pa-
tients studied is remarkably low for such a prevalent disease. Our systematic review of these RCTs 
revealed major methodological deficiencies in all trials, including: lack of double-blinding and intention-
to-treat analysis, unclear allocation concealment, lack of adverse event and drop out reporting and un-
known baseline risk of disease severity. Furthermore, high doses of thiazides were employed in all trials, 
in the case of the best studied thiazide, hydrochlorothiazide (HCTZ), up to 100 mg daily. At such high 
doses, side effects occur frequently. Nowadays, thiazides are widely used in the treatment of recurrent 
nephrolithiasis and arterial hypertension, but at significantly lower doses. In the case of recurrent neph-
rolithiasis, however, this practice is not supported by randomized evidence and consequently, we do not 
know whether the currently employed low dose thiazide regimens are effective in reducing the risk for 
stone recurrence. Thus, evidence for benefits and harms of thiazide diuretics in the prevention of cal-
cium-containing kidney stones in general remains unclear. In addition, the efficacy of the currently em-
ployed low dose thiazide regimens to prevent stone recurrence is not known. 
Aim of the study: The aim of the study is to compare the efficacy and safety of standard and low dose 
HCTZ treatment in the recurrence prevention of kidney stones. More specifically, the study aims to 
describe the dose-response relationship for placebo and three different dosages of HCTZ. 
Hypothesis: HCTZ significantly reduces stone recurrence compared to placebo. There is a significant 
dose-response relationship.  
Design of the study: This is a multicenter, randomized, placebo-controlled, double blind, parallel-group 
trial.  
Outcomes: The primary outcome as measured on the individual patient-level is stone recurrence dur-
ing study treatment.  
The primary outcome of the trial is the relationship between treatment group and stone recurrence during 
study treatment. 
Secondary outcomes include: 
- The individual components of the composite primary outcome: 
. 
symptomatic stone recurrence  
. 
radiologic stone recurrence  
- Changes in urinary biochemistry from baseline to visits 4 (3 months), 5 (12 months), 6 (24 months) 
and 7 (36 months):  
. 
calcium,  
. 
citrate,  
. 
oxalate,  

 
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. 
sodium,  
. 
total urine volume per 24 hours, 
. 
pH.  
1.2 
Objectives 
1.2.1 
Primary objective 
The primary objective is to assess the dose-response relationship between placebo and the three dif-
ferent dosages of HCTZ and stone recurrence. 
1.2.2 
Secondary objectives 
Secondary objectives are to assess the efficacy of the different dosages of HCTZ in terms of the primary 
outcome as well as the individual components of the composite primary outcome, i.e. symptomatic stone 
recurrence and radiologic stone recurrence. Further objectives are to study effects of different dosages 
of HCTZ on urinary biochemistry (efficacy and safety aspects) and the impact of different baseline char-
acteristics on stone recurrence and on the effects of the different dosages on stone recurrence (effect 
modification). 
1.2.3 
Safety objectives 
The safety objective is to assess the long-term safety and tolerability of HCTZ compared to placebo. 
2 
Study methods 
2.1 
Trial design 
NOSTONE is a randomized, placebo-controlled, observer-, clinician- and patient-blinded, parallel-group 
study. 
Eligible patients will be randomized in equal proportions between 12.5 mg, 25 mg or 50 mg HCTZ or 
placebo. All subjects will be given the IMP (HCTZ or placebo) once daily in the morning. Placebo will be 
administered to subjects randomized to that treatment in a form identical to the HCTZ capsules. The 
first dose of the IMP will be administered the day after the randomization. 
A total of 416 participants, 104 in each group, will be included in the study. Recruitment of participants 
is planned to occur over a period of 24 months at all 12 study sites. Study treatment will be 36 months 
for subjects enrolled in the first 12 months of the recruitment period and 24 months for subjects recruited 
in the remainder of the recruitment period. 
2.2 
Randomization 
Stratified randomization is used to assign participants to the different trial arms with the number of pre-
vious stone events as stratification factors:  
− 
Stratification group 1: 2 or 3 stone events within 10 years prior to randomization 
− 
Stratification group 2: ≥ 4 stone events within 10 years prior to randomization.  
Allocation is concealed using sequentially coded drug packs that are otherwise identical. Randomization 
lists were generated by a statistician at CTU Bern following dedicated standard operating procedures. 
The statistician communicated directly with the facility, which prepared the drug packs (Grosse Apotheke 
Dr. G. Bichsel AG, Interlaken, Switzerland). Investigators at each site assign the drug pack with the next 
sequential number to the next patient (consecutive). Content of the drug packs is based on randomiza-
tion lists as described above.  

 
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To ensure allocation concealment, the statistician preparing the randomization list as well as the facility 
handling of the un-blinded drug packs are otherwise not involved in the trial; randomization lists are 
stored electronically at CTU Bern with no access for persons directly involved in the trial. 
2.3 
Sample size  
A total of 416 patients, i.e. 104 in each arm, will be included in this study.  
The sample size was calculated using the artsurv command in Stata and was based on the primary 
objective i.e. to assess the dose-response relationship between treatment group and the primary out-
come, based on the following assumptions:  
− 
Uniform recruitment over 24 months with allocation ratio fixed at 1 across all arms 
− 
A maximum and minimum follow-up time of 36 and 24 months, respectively 
− 
A cumulative drop-out rate of 10% at 24 months after study start 
− 
Based on the available literature we assumed a risk of recurrence in the placebo group of 0.20 
and 0.45 at 12 and 36 months after study start, respectively. 
− 
Hazard ratios for the 12.5, 25 and 50 mg HCTZ doses of 0.90, 0.65 and 0.50, respectively. 
These effects were based on the literature review presented in Table 3.1-1 in the study protocol. 
− 
Power was set to be at least 80% and alpha was fixed at a two-sided level of 0.05 
− 
An unweighted log-rank test for linear trend with local alternatives. 
2.4 
Framework 
The null hypothesis that there is no linear trend between dose and the survival function for the primary 
outcome (i.e. recurrence) will be tested against the alternative that there is a linear trend.  
2.5 
Statistical interim analyses and stopping guidance 
There is no interim analysis planned. 
2.6 
Timing of final analysis 
Analysis will start after completion of data export, preparation and validation as described in the para-
graphs 3.1, 3.2 and 3.3 of the present document. Data validation starts at the beginning of the trial and 
goes on continuously until the validation of the last follow-up of the last patient.  
The analysis will use all outcomes except for the dosage group variable as explained further in the 
paragraph 2.8.  
 
 

 
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3 
Data management 
3.1 
Data export 
Clinical study data are provided by the CTU Bern (University of Bern) in a database format (secuTrial®) 
and will be imported into R by the trial statistician for data preparation, validation and analysis. 
3.2 
Data validation 
First line data validation is performed by the online eCRF system at real-time as defined in the data 
dictionary. Second line data validation and cleaning will be performed according to the SOP for data 
validation [3] with trimestrial Data Quality Review meetings during the data collection; and additionally 
after the completion of overall data collection, before database export for the final analysis.  
3.3 
Data preparation 
We will derive the primary and the secondary outcomes from the data. Time will be calculated as days 
since randomization. 
When recorded, calcium, citrate, oxalate, sodium and pH are measured in one (pH) or two (calcium, 
citrate, oxalate and sodium) 24-hour urine samples: 1 oil collection, 1 native collection. For the analysis, 
only the oil results are considered  When recorded, heart rate, systolic and diastolic blood pressures are 
measured three times; the exact value will be approximated by the mean of these three measurements.  
3.3.1 
Categorization of data  
3.3.1.1 
Treatment groups:  
Four treatment groups are considered, 12.5 mg, 25 mg or 50 mg HCTZ, or placebo.  
3.3.1.2 
Treatment centers:  
There are twelve treatment centers in Switzerland:  
− 
7 Cantonal Hospitals: Aarau, Bellinzona, Chur, Lugano, Luzern, Sion and St. Gallen 
− 
and 5 University Hospitals: Basel, Bern, Geneva, Lausanne, Zürich 
3.3.1.3 
Other 
. 
Stratification group 1: 2 or 3 stone events within 10 years prior to randomization; stratification 
group 2: ≥ 4 stone events within 10 years prior to randomization.  
. 
Baseline disease severity approximated by the number of stones within the last 10 years prior 
to randomization. The variable will be categorized into three groups using the first and the sec-
ond tertiles as cut-offs.  Patients with values below or equal to the first, second and third tertiles 
will be defined as patients with low, moderate disease and severe disease severity, respectively.   
. 
Biochemical abnormality is defined as the occurrence of hypercalciuria. 
. 
Hypercalciuria is defined as above 6.25 mmol/d (=250 mg/d) in women and above 7.5 mmol/d 
(=300 mg/d) in men. 
. 
Biochemical abnormalities at baseline - hypercalciuria vs. no hypercalciuria in the baseline 
urine analysis.  
. 
Hypertension is considered occurring when the systolic blood pressure exceeds 89 mmHg or 
when the diastolic blood pressure exceeds 139 mmHg or when the subject is treated by anti-
hypertensive medication. 

 
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3.5 
Data sharing (if applicable) 
Data will be shared as described in the Protocol: “Once results have been published, trial data will 
be accessible to external researchers and anonymized datasets corresponding to each publication 
will be made available. Investigators wishing to replicate the analyses or to do an individual patient 
meta-analysis may request the data from the steering committee. Access to data will be granted in 
an unbureaucratic way.”  
 
4 
Statistical principles 
4.1 
Confidence intervals and P values 
All confidence intervals will be two-sided and relate to the 95% level and the two-sided significance level 
will be set at α = 0.05. 
4.2 
Analysis populations 
4.2.1 
Full analysis set (FAS) 
The full analysis set consists of all randomized patients regardless of whether they actually received the 
allocated intervention or not or any other protocol deviations. Patients will be analysed in the group they 
were randomized regardless of any cross-overs or loss to follow-up (intention-to-treat principle). 
4.2.2 
Per-protocol (PP) 
The per-protocol population consists of all subjects in the FAS who did not have any protocol deviations 
that could confound the interpretation of analyses conducted on the FAS. The following are common 
major protocol deviations: 
- 
Not receiving the allocated treatment.  
- 
Not fulfilling the eligibility criteria.Failure to perform primary endpoint assessment, i.e. no 
visit/call performed 
4.2.3 
Dealing with non-compliance:  
4.2.3.1 
Definition of non-compliance 
We will use two different definitions of non-compliance: 
. 
First, we will consider as non-compliant participants who missed more than 20% of 
IMP during their study period (period when they were followed in the study).  
. 
Second, we will only consider participants as non-compliant who missed more than 
20% of IMP voluntary (i.e., without a medical indication as defined by the protocol) 
during their study period (period when they were followed in the study).  
If the frequency of non-compliant patients exceeds 10%, additional per-protocol analyses that allow for 
more informative causal inferences [4] will be explored. 
4.2.3.2 
Assessment of non-compliance  
Reasons for IMP stopping  

 
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Reasons for long temporary (more than 7 days in a row) and permanent IMP stops will be adjudicated 
and categorized as medical vs. voluntary. Short temporary stops (i.e., less than 7 days in a row) will be 
assumed to be voluntary. 
 
Number of missed capsules 
When a stopping period is reported (for long temporary & permanent stop), patients will be assumed 
to have missed 1 capsule/day.  
In case of a short temporary stop, patients indicate the number of missed capsules in a categorical 
fashion. From this answer we will estimate the number of missed capsules since the last performed 
visit/call as follows: 
Number of missed capsules, as reported by the pa-
tient 
Estimated number of missed capsules since the last 
visit/call 
1-5 tablets 
3 
6-10 tablets 
8 
11-20 tablets 
16 
more than 20  
10 per each month since the last visit/call. 
Capsules are assumed to be missing in a continuous period around the mid-point of the reporting period 
(i.e., [last visit/call – current visit]) with 1 missed capsule/day. 
4.2.4 
Safety population 
In the safety analysis data set, patients will be included in the treatment group they actually received (at 
least one dose). 
4.3 
Estimands 
The ICH E9 (R1) addendum on estimands and sensitivity analyses [1] defines different treatment esti-
mators that are of interest in clinical trials. An estimand is the target of estimation to address the scientific 
question of interest posed by the trial objective. Attributes of an estimand include the population of in-
terest, the outcome of interest, the specification of how intercurrent events such as cross-overs and non-
compliance are reflected in the scientific question of interest, and the population-level summary for the 
outcome. 
4.3.1 
Treatment policy estimand 
The estimand that addresses the main objective of this trial is based on the treatment policy strategy 
and resembles a classical intention-to-treat analysis.  
We define the estimand with following attributes: 
- 
Population: Full-Analysis Set 
- 
Outcome:  
o 
The primary outcome i.e. stone recurrence defined as the composite of symptomatic 
and radiological recurrence 
o 
All secondary outcomes 
- 
Effect measure:  
o 
Primary outcome: hazard ratio (odds ratio if needed, see section 6.1.1) 
o 
Secondary outcomes 
▪ 
Time-to-event: hazard ratio 
▪ 
Binary: odds ratio 
▪ 
Continuous: mean difference 

 
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- 
Handling of intercurrent events: cross-overs, drop-outs, non-adherence, or premature treat-
ment stops are ignored 
4.3.2 
Additional estimands 
Moreover, we will assess two additional estimands based on the per-protocol analysis sets: 
- 
While-on-treatment estimand where medically justified treatment changes are ignored i.e. con-
sidered as part of the intended treatment  
o 
Population: per-protocol set according to definition 2 (see section 4.2.2) 
o 
Outcome:  
▪ 
The primary outcome i.e., stone recurrence defined as the composite of 
symptomatic and radiological recurrence 
▪ 
symptomatic stone recurrence 
o 
Effect measure: rate ratio 
o 
Handling of intercurrent events: subjects will be censored if they become non-compli-
ant for a non-medically indicated, voluntary reason 
- 
Hypothetical estimand where non-adherence is envisaged to not occur i.e. it reflects a sce-
nario with perfect i.e. continuous treatment 
o 
Population: per-protocol set according to definition 1 (see section 4.2.2) 
o 
Outcome:  
▪ 
The primary outcome i.e., stone recurrence defined as the composite of 
symptomatic and radiological recurrence 
▪ 
symptomatic stone recurrence 
o 
Effect measure: rate ratio 
o 
Handling of intercurrent events: subjects will be censored if they become non-compli-
ant for any reason 
5 
Trial Population 
5.1 
Screening data 
No screening data were collected and the representativeness of trial sample cannot be described. 
5.2 
Eligibility 
Individuals fulfilling all of the following inclusion criteria are eligible for the study:  
− 
Informed Consent as documented by signature  
− 
Age 18 years or older  
− 
Recurrent kidney stone disease (≥ 2 stone events within the last 10 years prior to randomiza-
tion)  
− 
Any past kidney stone containing 50% or more of calcium oxalate, calcium phosphate or a 
mixture of both  
The presence of any one of the following exclusion criteria will lead to exclusion of the individual:  
1. Pharmacologic prevention for stone recurrence less than 3 months prior to randomization.  
2. Patients with secondary causes of recurrent calcareous nephrolithiasis including:  
. 
Severe eating disorders (anorexia or bulimia);  
. 
Chronic inflammatory bowel disease, bariatric surgery, intestinal surgery with malab-
sorbtion or chronic diarrheal status; 
. 
Sarcoidosis; 

 
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. 
Primary hyperparathyroidism; 
. 
Hyperthyroidism;  
. 
Complete distal tubular acidosis; 
. 
Active malignancy. 
3. Patients with the following medications. According to the Protocol’ criteria for withdrawal/ dis-
continuation of participants, the “IMP will be discontinued only if the patient took the medica-
tions listed in the exclusion criteria for more than 4 months”:  
. 
Thiazide or loop diuretics;  
. 
Carbonic anhydrase inhibitors (including topiramate) ;  
. 
Xanthine oxidase inhibitors (febuxostat or allopurinol);  
. 
Alkali, including potassium citrate or sodium bicarbonate; 
. 
Treatment with 1,25-OH Vitamin D (calcitriol); 
. 
Calcium supplementation; 
. 
Bisphosphonates; 
. 
Denusomab; 
. 
Teriparatide; 
. 
Glucocorticoids. 
4. Obstructive uropathy, if not treated successfully.  
5. Urinary tract infection, if not treated successfully.  
6. Chronic kidney disease (defined as CKD-EPI eGFR < 30 mL/min per 1,73 m2 body surface 
area for more than 3 months). 
7. Patients with a kidney transplant.  
8. > 3 gout arthritis episodes within one year prior to randomisation or gout arthritis requiring uric 
acid lowering therapy.  
9. Cystinuria at screening. 
10. Hypokalemia (blood potassium level < 3 mmol/L) at screening.  
11. Hyponatremia (blood sodium level < 125 mmol/L) at screening.  
12. Pregnant and lactating women [pregnancy test to be performed for women of child-bearing 
potential (defined as women who are not surgically sterilized/ hysterectomized, and/ or who 
are postmenonpausal for less than 12 months)]. 
13. Previous (within 3 months prior to randomization) or concomitant participation in another inter-
ventional clinical trial. 
14. Inability to understand and follow the protocol. 
15. Known allergy to the study drug.  
5.3 
Recruitment 
A CONSORT patient flow diagram will be completed following the CONSORT 2010 standards 
(http://www.consort-statement.org/consort-2010). 
The flow chart will consider specifically: 
- 
Ns assessed for eligibility 
- 
Ns eligible and not included into the trial 
- 
Ns randomized 
- 
Ns allocated to intervention 
- 
Ns receiving allocated intervention 
- 
Ns not receiving allocated intervention (with reasons) 
- 
Ns discontinued intervention (with reasons) 

 
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- 
Ns lost to follow up (with reasons) 
- 
Ns analyzed 
- 
Ns excluded from primary analysis 
5.4 
Baseline patient characteristics 
The patient characteristics of the FAS at baseline will be presented in a table, stratified by treatment 
arm, as number and percentage or mean and standard deviation for categorical and normally distributed 
continuous variables, respectively. For data severely deviating from a normal distribution, we will present 
median and interquartile ranges. No statistical comparisons of patient characteristics at baseline will be 
performed. 
  
Placebo 
12.5mg 
HCTZ 
25mg 
HCTZ 
50 mg 
HCTZ 
Total 
n= 
n= 
n= 
n= 
  
  
  
  
  
DEMOGRAPHICS 
  
  
  
  
Age, years (mean + SD) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Sex (Female, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
DISEASE SEVERITY AND STONE COMPOSITION 
  
  
  
  
Number of previous stone events within the 10 years prior to 
randomization 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
− 
[2,3] stones 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
− 
≥4 stones 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Number of previous stone events within the 10 years prior to 
randomization 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
− 
First tertile 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
− 
Second tertile 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
− 
Third tertile 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Stone composition: 
 
 
 
 
− 
calcium oxalate (i.e. > 50% ca-ox) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
− 
calcium phosphate (i.e. > 50% ca-p) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
− 
other. 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
PHYSICAL EXAMINATION & VITAL SIGNS 
  
  
  
  
BMI  
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Systolic blood pressure 2  
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Diastolic blood pressure2 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Heart rate2 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
HABITS & CARDIOVASCULAR RISK FACTORS 
  
  
  
  
Smoking  
  
  
  
  
− 
Never 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
− 
Current 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
 
2 Values averaged over 3 measurements 

 
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− 
Former 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Alcohol consumption (unit/day) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Hypertension 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Treated for hypertension (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Diabetes (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Treated for diabetes (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Gout arthritis (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
RENAL SYSTEM 
  
  
  
  
Lower urinary tract infection(s) in the past  (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Upper urinary tract infection(s) in the past   (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
Kidney malformations/Urinary tract malformations   (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
BLOOD ANALYSIS (SERUM) 
 
 
 
 
Potassium (K) (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Sodium (Na) (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Calcium (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Magnesium (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Bicarbonate (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Haemoglobin A1c (%) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Creatinine (umol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Uric acid ( μmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Total Cholesterol (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
HDL Cholesterol (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
LDL Cholesterol (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Triglycerides (mmol/l) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
URINE ANALYSIS (FIRST 24 HR COLLECTION, with oil and paraf-
fin ) 
  
  
  
  
Urine volume (l /24 h) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Calcium (mmol/24 h) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Sodium (mmol/24 h) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Citrate (mmol/24 h)  
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
Oxalate (mmol/24 h) 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
pH 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
xx.x + xx.x 
BIOCHEMICAL ABNORMALITIES (urine based) 
 
 
 
 
Hypercalciuria (urine calcium > 7.5 mmol/d in men or > 6.25 
mmol/d in women)  (yes, n [%]) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
xx (xx.x) 
5.5 
Adherence and protocol deviations 
At each follow-up visit, participants are asked whether they were able to take their study medication 
every day. For each visit, we will present the number and percentage of patients who were or were not 
able to take their study medication every day. Among the patients who were not able to take their study 
medication every day, we will present the percentages of the following categories: missed 1-5 capsules, 
6-10 capsules, 11-20 capsules, more than 20 capsules of the 91 expected in the last 3 months.   
The common major protocol deviations are listed in the paragraph 4.2.2 above. The number of patients 
presenting each of these deviations will be summarized in a table. 

 
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5.6 
Withdrawal/follow-up 
The number of withdrawal and loss to follow-up at each visit in the control and in the treatment arm will 
be presented in a CONSORT patient flow diagram (for details see 5.3 above). 
6 
Analysis 
6.1 
Outcome definitions 
6.1.1 
Primary outcome 
The primary outcome of the trial is the relationship between dose group and stone recurrence during 
study treatment (up to 36 months). We will analyze stone recurrence as time to event outcome. 
The primary outcome at the patient level is stone recurrence during study treatment. Stone recurrence 
is the composite of symptomatic and radiological recurrence.  
Symptomatic stone recurrence is defined as visible passage of a stone with or without accompanying 
typical symptoms such as flank/ loin pain and hematuria or a symptomatic or asymptomatic stone re-
quiring urological intervention for stone removal. In case of potential stone passages without visible 
stones, it will be up to the local investigators to evaluate patients’ symptoms and determine whether a 
stone passage occurred or the symptoms were rather due to a different cause. 
Radiological stone recurrence as assessed by low-dose non-intravenous (iv) contrast CT imaging is 
defined as the appearance of new caliculi or enlargement of preexisting caliculi with reference to the 
baseline CT performed at visit 3 (2 weeks) to the end of study treatment. The processing and evaluation 
of the CT images is described in a specific SOP (SOP_CT_V1.3). 
6.1.1.1 
Outcome derivation:  
Stone events:  
Radiological stone recurrence will be assessed by comparing baseline to end of study CT. CT must be 
performed in a time window of three months.  
When the CT are performed on time, we will consider (i) the time under observation as the interval 
[randomization, last performed visit], (ii) the date of (eventual) radiological event(s) as the date of the 
last performed visit.  
In case of deviation from the study plan we will adopt different strategies: 
- 
when the baseline CT was performed more than three months before or after the randomiza-
tion: the radiological assessment will be considered as missing. 
- 
when the end of study CT was performed more than three months after the last visit: the radio-
logical assessment will be considered as missing. 
- 
when the end of study CT was performed more than three months before the last visit: the 
time under observation will be calculated as = (date of end of study CT + 3 months) – random-
ization date. In case of a radiological event, we will consider the date of the event to be equal 
to the date of end of study CT + 3 months). Every symptomatic event occurring after (date of 
end of study CT + 3 months) will not be considered for the analysis.  
According to protocol (v1.7), stone events occurring during the first 6 weeks after randomization will not 
be considered as events for the analysis.  
In case of multiple stones events occurring on the same day, we will assume the events to be separated 
by 1h each.  
 

 
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Missing data 
In cases where no symptomatic stone is reported and the radiological stone recurrence is not assessed 
(e.g. because of missing or not-on time CT) we will use different strategies.  
- 
For the main analysis we will assume that, at the time of censoring no radiological stone oc-
curred.  
- 
In a first sensitivity analysis, we will assume the occurrence of radiological stone 1h before 
censoring (i.e., worst case scenario).  
- 
In a second sensitivity analysis we will remove all the patients without a radiological stone as-
sessment regardless of the occurrence (or not) of symptomatic stones. 
6.1.2 
Secondary outcomes  
Secondary outcomes include: 
- 
The number of stone recurrence(s) 
- 
The individual components of the composite primary outcome: 
. 
Symptomatic stone recurrence (assessed as described for the primary outcome) 
. 
Number of symptomatic stone recurrence(s) 
. 
Radiologic stone recurrence(s) 
. 
Number of radiologic stone recurrence(s)  
-  
Changes in urinary biochemistry: urinary volume3, calcium, citrate, oxalate, sodium and pH at visits 
4 (3 months), 5 (12 months), 6 (24 months) and 7 (36 months). 
6.1.2.1 
Outcome derivation: 
As for the primary outcome: 
- 
Radiological results will only be considered as missing when the baseline CT was not per-
formed in a window of +/- 3months around the randomization date, and/or the end-of-study CT 
was performed more than 3months after the last visit. 
- 
Symptomatic stones occurring during the first 6 weeks after randomization or more than three 
months after the end of study CT, will not be considered for the analysis of number of stone 
recurrence, symptomatic stone recurrence and number of symptomatic stone recurrence(s).  
Because of technical limitations, the number of radiologic stone recurrence could not be assessed di-
rectly, we will use the number of new radiological stone as a proxy of this outcome. 
The total number of stone recurrence will be assessed as: N(symptomatic stones) + N(new radiologic 
stones). 
For the biochemical outcomes we will use the urine collected with addition of thymol and paraffin oil 
(i.e., oil measurements). 
 
3 Urinary volume per se is not biochemistry, however it is an absolute prerequisite for properly evaluating the eventual biochemistry 
changes as for equal microelement excretions per 24 hours its urinary concentrations might differ depending on volume.  

 
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6.1.3 
Assessment of safety outcomes  
6.1.3.1 
Serious adverse events (SAEs)  
SAEs will be collected, fully investigated and documented in the source documents and the eCRF for 
all participants from the date of ICF signature until the last protocol-specific procedure has been com-
pleted, including a safety follow-up period of 30 days.  
Adverse events (AEs) of special interest  
For this trial, (non-serious) AEs will not be documented in the eCRF with exception of the following 
events “of special interest” occurring from the date of randomization (visit 2) until visit 7 (36 months):  
- Hypokalemia, defined as blood potassium level < 3 mmol/L;  
- Hyponatremia, defined as blood sodium level < 125 mmol/L;  
- Hypomagnesemia, defined as blood magnesium level < 0.5 mmol/L; 
- Blood creatinine > 150% of baseline creatinine;  
- Newly developed overt diabetes;  
- Allergic reaction of skin if considered by the local investigator to be potentially related to the 
study medication; 
- Gouty arthritis if recurrence > 3 times per year or requiring Uric acid lowering therapy. 
To assess the AEs of special interest the following blood biochemistry parameters are collected as 
safety outcome:  potassium, sodium, magnesium, creatinine, glucose (fasting), HbA1c at visits 4 (3 
months), 5 (12 months), 6 (24 months) and 7 (36 months). These parameters will be assessed according 
to the protocol. Moreover, we will perform the additional analysis as below in the paragraph 6.2.5. 
6.1.4 
Assessments in participants who prematurely stop the study  
Participants who permanently discontinue the study treatment will undergo all protocol-specified study 
visits and assessments. If study visits are not possible, a telephone consultation will be performed to 
determine if relevant health events/ endpoints have occurred. 
6.2 
Analysis methods 
6.2.1 
Primary analysis 
The CTU Bern statistician will perform the analysis of the study. The statistician will be first blinded to 
the group allocation, then un-blinded as described in the paragraph 2.8. In the primary analysis, all pa-
tients will be analysed using the FAS according to the intention-to-treat principle. All effect measures 
will be accompanied by 95% confidence intervals and all p-values will be two-sided without adjustment 
for multiple testing.  
 
Primary outcome 
Using the below approach, we will address the primary objective of the trial, i.e. test for any dose-re-
sponse relationship between dosage group and stone recurrence.  
Investigate the treatment effect on the occurrence (or not) of stone recurrence. 

 
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We will test for a linear trend using a log-rank test stratified for the number of stones (<4 vs. ≥ 4 within 
10 years prior to randomization) and present Kaplan-Meier curves by treatment dose. We will then cal-
culate rate ratios between dosage groups using the Mantel–Cox method, stratified for number of 
stones at baseline (<4 vs. ≥ 4).  
In a sensitivity analysis we will analyze the primary outcome as a binary outcome (i.e. occurrence of 
any symptomatic or radiologic stone recurrence yes/no, see section 6.2.3). We will consider the com-
parisons between placebo and each of the three active trial arms as exploratory, because the trial size 
does not provide enough statistical power to detect differences between each active arm and the pla-
cebo group. 
6.2.1.1 
Secondary outcomes  
The total number of stone recurrence will be analysed using a generalized linear model including the 
treatment dose as categorical variable and adjusted for the number of stone events at baseline (<4 vs. 
≥ 4). Depending on the distribution of the number of stones, we will use a negative binomial or a zero 
inflated negative binomial regression. In case of zero inflation we will investigate the effect of treatment 
on both the count and the logit part of the model. 
Symptomatic recurrence will be analyzed as the primary outcome.  
Number of symptomatic stone recurrence(s) will be analyzed as the total number of stone recurrence(s) 
(see above) 
Radiologic recurrence will analyzed both as a binary outcome (i.e. yes/no) and then as a count variable 
using the methodology described for the total number of stone recurrence(s).  
Changes in urinary biochemistry from baseline to visits 4 (3 months), 5 (12 months), 6 (24 months) and 
7 (36 months):  
. 
urine volume, 
. 
calcium,  
. 
citrate,  
. 
oxalate,  
. 
sodium,  
. 
pH, 
will be analysed using a repeated-measures random-effects linear regression model in order to assess 
differences between treatment groups over time. Models will include fixed effects for the intervention 
group (continuous), the baseline value (continuous), the time point (categorical), an interaction term 
between group and time point, and an indicator for number of stones (<4 vs. ≥ 4), and a random intercept 
for the patient. 
𝑂𝑈𝑇𝐶𝑂𝑀𝐸𝑖𝑗 ~ 𝑂𝑈𝑇𝐶𝑂𝑀𝐸0𝑗+ 𝐴𝑅𝑀𝑗+ 𝑇𝐼𝑀𝐸𝑖+ 𝐴𝑅𝑀𝑗∗𝑇𝐼𝑀𝐸𝑖+ 𝑆𝑇𝑅𝐴𝑇𝑗+ (1|𝑗), 
where j is for subject and i is for visit number, i=0 being screening visit. 
If the timing of urinary analysis is highly variable among patients, we will not consider time as a discrete 
but as a continuous variable. 
6.2.2 
Secondary analyses 
In a secondary per-protocol analysis, we will evaluate primary and secondary outcomes based on the  
PP analysis set. 
We will use a multivariable Cox-model to assess the impact of baseline disease severity (<4 vs. ≥ 4 
within 10 years prior to randomization) on stone recurrence; the impact of biochemical abnormalities on 

 
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stone recurrence; and the impact of stone composition on stone recurrence using the categorization of 
exploratory variables from the paragraph 3.3.1. 
6.2.3 
Sensitivity analyses 
In case of undetermined results for the primary outcome (i.e., no symptomatic stone and no radiologic 
assessment), the primary analysis will be done by  
(I) 
Assuming occurrence of a radiological stone 1h before censoring  
(II) 
Removing patients with a missing radiologic assessment, regardless of the occurrence (or 
not) of symptomatic stones 
For the primary outcome as well as for the number of symptomatic stone we will present a Kaplan-Meier 
curve including the events occurring in the first 6 weeks of the study and perform a landmark analysis 
at the 6 weeks landmark point.  
We will analyze the primary outcome as a binary outcome (i.e. occurrence of any symptomatic or radi-
ologic stone recurrence yes/no). To do so we will use a logistic regression model including the treatment 
dose as categorical variable and adjusted for the number of stone events at baseline (<4 vs. ≥ 4) and 
the time under observation. 
We will compare the FAS and PP analysis based on multiple imputations with the analysis of all available 
cases. 
We will assess the sensitivity of time-to-first-event approach (log-rank test, Kaplan-Meier curves and the 
Mantel-Cox rate ratios) comparing it with multiple event models or frailty (count) models or marginal 
count models.  
6.2.4 
Subgroup analyses 
The following baseline characteristics may modify the expected treatment effect:  
- Baseline disease severity (defined by cut-offs at highest, middle and lowest tertiles in stone frequencies 
within the last 10 years prior to randomization.)  
- Biochemical abnormalities (hypercalciuria vs. no hypercalciuria)  
- Stone composition of the last analyzed stone at baseline (calcium oxalate, calcium phosphate and 
other). 
Although power may be too low for the definitive results, we will perform subgroup analyses for the 
primary outcome as well as for the occurrence of symptomatic stone outcomes according to the sub-
populations above defined. All subgroup analyses will be accompanied by tests for interactions.  
6.2.5 
Additional analyses 
- 
In the secondary analysis of the paragraph 6.2.2 in case of a relevant number of patients with mul-
tiple symptomatic stone events (i.e. more than 5% of patients with more than one event), we will 
consider a shared-frailty Cox model for multiple recurrent events. 
- 
 We will additionally address the primary objective of the trial, i.e. the dose-response relationship 
for dosage groups and the stone recurrence hazard during the study by considering treatment 
dose as continuous variable and fitting a Cox proportional hazards model stratified for the number 
of stone (<4 vs. ≥ 4). In this model, we will assess the linear versus non-linear dependence of the 
dosage by introducing fractional polynomial dosage terms and evaluating their significance.   
- 
In order to assess differences between treatment groups and occurrence of adverse events of spe-
cial interest over time we will additionally analyze the changes in continuous safety outcomes from 
baseline to discharge (visits 4, 5, 6 and 7) using a repeated-measures linear random-effects model. 

 
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Models will include fixed effects for the intervention group (continuous), the baseline value (contin-
uous), the time point (categorical or continuous), an interaction term between group and time point, 
and baseline stratification for the number of stones (<4 vs. ≥ 4), and a random intercept for the 
patient: 
𝑂𝑈𝑇𝐶𝑂𝑀𝐸𝑖𝑗 ~ 𝑂𝑈𝑇𝐶𝑂𝑀𝐸0𝑗+ 𝐴𝑅𝑀𝑗+ 𝑇𝐼𝑀𝐸𝑖+ 𝐴𝑅𝑀𝑗∗𝑇𝐼𝑀𝐸𝑖+ 𝑆𝑇𝑅𝐴𝑇𝑗+ (1|𝑗), 
where 𝑗 is for subject and 𝑖 is for visit number, 𝑖= 0 being screening visit. The following variables from 
blood serum will be subject to this analysis: sodium, potassium, magnesium, creatinine, glucose (fast-
ing), HbA1c, total cholesterol, LDL and HDL cholesterol, and triglycerides - In repeated-measures ran-
dom-effects models of continuous secondary outcomes, we will also consider to use the treatment group 
categorical and the time point continuous, and will assess different relationships between the continuous 
variables and the outcome of interest using fractional polynomial functions. 
6.2.6 
Causal inferences for PP analysis 
Analysis will be conducted separately for the first and second definition of compliance (see section 
4.2.3). 
Subject will be regarded as dependently censored at the day a subject withdraws, is lost to FUP or at 
the first time a subject becomes non-compliant. We will structure our dataset into time intervals. At each 
time interval a subject will be considered as non-compliant if he or she was non-compliant before or if 
the cumulative number of (voluntary) missed capsules reached 20% of the cumulative number of ex-
pected number of taken capsules. If possible, we will use all the observed event or treatment censoring 
times in the sample to define the intervals. Otherwise we will consider three months intervals. 
We will then use the inverse probability of  censoring  weighting  technique  (IPCW)  to  recreate  an  
unbiased  scenario  where   
- 
subjects remain on their therapy always (using definition 1 of non-compliance), i.e. subjects 
will be censored if they become non-compliant for any reason  
- 
subjects remain on their therapy until discountinuation of the therapy becomes medically 
indicated (using definition 2 of non-compliance), i.e. subjects will only be censored if they 
become non-compliant for a non-medically indicated, voluntary reason 
IPCW weights corresponding to the inverse probability of censoring, will be calculated separately for the 
first and second definition of non-adherence. Depending on the frequency and pattern of censoring the 
probability of censoring will be calculated either as the product of the probability of being censored for 
“classical reasons” (i.e., lost to FUP, withdraw) and the probability of being “non-compliant”; or as the 
probability of being censored for whatever reason (i.e., lost to FUP, withdraw or non-adherence). 
We will use a logistic model or a Cox proportional hazards model for censoring to calculate the proba-
bilities. This model will include baseline and time-dependent prognostic factors as covariates. Baseline 
predictors will include the randomization group as well as baseline variables (as described in the BL 
table section 5.4). Time dependent covariates will notably include the blood and urine values, urinary 
biochemistry (i.e., urinary volume, calcium, citrate, oxalate, sodium and pH), blood pressure and values, 
heart rate, number of AE and SAE event. 
6.2.7 
Assessment of statistical assumptions 
For all models, we will perform model validation i.e. check for the goodness-of-fit. In case of deviations 
from the applied models, to achieve a good fit to the data we will apply 1) common transformations and 
2) non-parametric models.  

 
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6.3 
Interim analyses 
No formal interim analysis is planned. 
6.4 
Missing data 
For the primary outcome, drop-outs will be censored at the last available visit. 
For count data assessed over time (i.e., number of symptomatic, and total stone recurrence), we will 
adjust observation time if patients drop out.  
For changes in urinary biochemistry from baseline to visits 4 (3 months), 5 (12 months), 6 (24 months) 
and 7 (36 months) we will use repeated-measures models that implicitly account for missing data as 
long as the baseline and at least one follow-up value is available.  
If missing data are problematic for the primary analyses of primary or secondary outcomes, multiple 
imputation will be used as sensitivity analysis. Missing data will be considered as problematic where 
their proportions for individual variables exceed 10%. 
Missing data will be handled by multiple imputation including the primary outcome in the multiple impu-
tation model besides other baseline and follow-up characteristics.  
We will assume missingness at random. Each outcome will be imputed separately. We will use relevant 
baseline variables, the respective outcome measure and relevant variables at all time-points as well as 
the treatment indicator as predictors in the imputation models. Age, BMI, systolic and diastolic blood 
pressure, heart rate, alcohol consumption, blood analysis values (i.e. potassium, magnesium, glucose, 
creatinine, uric acid and cholesterol) and urine analysis values (i.e. calcium, creatinine, citrate, oxalate 
and PH) will be used as continuous, the other variables will be treated as categorical. Binary variables 
with a frequency of less than 5% will be omitted. We will use multiple imputation by chained equation. 
In total, fifty imputed data sets will be generated, which will be analyzed as described by van Buuren [2]. 
6.5 
Harms 
Safety analysis will include a descriptive summary of pre-specified AEs of special interest, all SAEs, and 
vital signs. All safety endpoints will be reported separately for each treatment group based on the safety 
analysis data set. 
No formal statistical testing will be applied. 
6.6 
Statistical software 
We will use the R statistical software to calculate outcome and co-variate values, and to perform all 
analyses. We will list the R version and all used packages in the statistical report. 
6.7 
Quality control 
A second statistician will double code the primary analysis from the raw data. 
 
 
 

 
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6.8 
Changes from the protocol 
The SAP is consistent with principle features of the statistical methods described in the protocol. Any 
deviation from the protocol is detailed hereunder with reason. 
 
 
 
Header 
Change 
Reason 
Additional second-
ary outcomes 
Overall, symptomatic and radiologic 
stone recurrence will be analyzed as 
count outcomes. 
The total number of stone recurrence 
will be assessed as: N(symptomatic 
stones)  + N(radiologic stones) and an-
alyzed using a generalized linear 
model. 
The total number of stone is a measure of 
interest. 
Change in second-
ary outcomes 
Radiologic recurrence will be analyzed 
both as a binary outcome (i.e. yes/no) 
as well as a count outcome, but not as 
a time to event outcome. 
Radiological recurrence is assessed by 
scan at the end of the study: we don’t 
know the exact time of each event. 
Change 
in 
the 
analysis of the 
primary outcome 
 
Instead of reporting the hazard ratios be-
tween dosage groups using the Cox pro-
portional hazards model, we will calculate 
the rate ratios with Mantel–Cox method  
 
Proportional hazard assumption will prob-
ably not be fulfilled, and rate ratio is the 
statistics corresponding to the log-rank 
test (i.e., test used for testing the occur-
rence of a linear trend) 
Change in diabe-
tes definition 
 
Diabetes is defined as the occurrence of 
HbA1c 6.5% or higher; or treated (oral or 
sc antidiabetic or insulin). 
Fasting status during blood draw was not 
consistently reported during study visits. 
Hence glucose measurements will not be 
suitable for diabetes definition.  
Change in deriva-
tion of secondary 
outcome 
The number of radiologic stone recurrence 
will be approximated by the number of new 
radiological stones. 
 
The number of radiological stone recur-
rence cannot be assessed 

 
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6.9 
References 
1. 
European Medicines Agency, C.f.H.M.P., Draft ICH E9 (R1) addendum on estimands and 
sensitivity analysis in clinical trials to the guideline on statistical principles for clinical trials, step 
2b. 2017. 
2. 
Rubin, D.B., Multiple imputation for nonresponse in surveys. Wiley series in probability and 
mathematical statistics Applied probability and statistics. 1987, New York etc.: John Wiley. 
3.          SOP Statistical data validation, CS_STA_SOP_02, version 03, 11.09.2018 
4.  
https://arxiv.org/abs/1911.06030 

 
 
 
 
 
 
 
 
 
Revision history 

 
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Authored by  
Name 
Affiliation 
SAP Role  
Marie Roumet, PhD 
CTU Bern 
Author 
Andreas Limacher, PhD 
CTU Bern 
Author 
Irina Irincheeva 
CTU Bern 
Author 
Sven Trelle, MD 
CTU Bern 
Reviewer 
Prof. Dr. med. Daniel Fuster 
 
Reviewer 
 
Revision history 
 
 
 
Revision 
Justification  
Timing  
1.0 
First version 
06.11.2018 
2.0 
Definition: 
Definitions of symptomatic and radiologic stone re-
currence updated according to the last version of 
the protocol (i.e. 1.7). 
Derivation & analysis of the primary outcome 
1.  According to protocol (v1.7), stones occurring 
during the first 6 weeks after randomization will not 
be considered as events for the analysis.  
2. Time to event analysis:  
In case of radiological recurrence, we will assume 
the date of the event to be equal to the date of the 
end of study CT. In case of multiple radiological 
stones, we will consider them as multiple events 
separated by 1h each. 
In case of a violation of the proportional hazard as-
sumption, we will analyze the outcome as a binary 
outcome (i.e. occurrence of any symptomatic or ra-
diologic stone recurrence yes/no).  
Secondary outcomes  
− 
Stone recurrence will be analyzed as a count 
outcome. 
The total number of stone recurrence will be as-
sessed as: N(symptomatic stones)  + N(radio-
logic stones) and analyzed using a generalized 
linear model. 
− 
Symptomatic recurrence will be analyzed as 
time to event as well as count outcome.  
27.04.2020 
Data still blinded; change imple-
mented without inspection of 
data 
 

 
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− 
Radiologic recurrence will be analyzed both as 
a binary outcome (i.e. yes/no) as well as a 
count outcome, but not as a time to event out-
come. 
− 
Changes in urinary biochemistry : If the timing 
of urinary analysis is highly variable among pa-
tients, we will not consider time as a discrete 
but as a continuous variable. 
3.0 
Definition of the PP population 
The following issues are not considered anymore 
as major protocol deviations: 
 
− 
Failure to perform primary endpoint assess-
ment, i.e. assessment not done.  
We will only remove patients who didn’t perform 
any visit/call: patients for whom neither the oc-
currence of symptomatic events nor the occur-
rence of radiological stone events have been 
assessed. 
 
− 
Missing treatment doses: we will use inverse 
probability censoring weighting methods to deal 
with non-compliance. 
3.5.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
 
 
 
3.0 up-
dated in 
4.0 
Derivation & analysis of the primary outcome 
1. Derivation  
Symptomatic events occurring more than 3 months 
after the end-of-study CT, will not be considered for 
the analysis 
Radiological results will only be used for analysis 
when the baseline CT was performed in a window 
of +/- 3 months around the randomization date, and 
the end-of-study CT less than 3 months after the 
last visit. 
In case of radiological recurrence, we will assume 
the date of the event to be equal to the date of the 
last performed visit or, if earlier, to the date of the 
end-of-study CT+3 months.  
In cases where no symptomatic stone events are 
reported and the radiological stone recurrence is 
not assessed (e.g. because of no CT performed at 
the end of study) we will use different strategies.  
- 
For the main analysis we will assume that, 
at the time of censoring no radiological 
stone occurred  
- 
In a first sensitivity analysis, we will assume 
the occurrence of a radiological stone 1h 
before censoring (i.e., worst case scenario)  
3.5.2021 updated on 9.11.21 
Data still blinded; change imple-
mented without inspection of 
data 

 
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- 
In a second sensitivity analysis we will re-
move all the patients without a radiological 
stone assessment. 
3.0 
2. Analysis  
Instead of reporting the hazard ratios between dos-
age groups using the Cox proportional hazards 
model, we will calculate rate ratios with the Mantel–
Cox method.  
3.5.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
4.0 
 
Derivation of the secondary outcomes 
Radiological results will only be used for analysis 
when the baseline CT was performed in a window 
of +/- 3 months around the randomization date, and 
the end-of-study CT less than 3 months after the 
last visit. 
Symptomatic events occurring more than 3 months 
after the end-of-study CT, will not be considered for 
the analysis 
The number of radiologic stone recurrence will be 
approximated by the number of new radiological 
stones. 
For the biochemical outcomes, we will use the re-
sults of the 24 h urines collected with thymol and 
paraffin oil (i.e., oil measurements). 
9.11.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
3.0 
Sensitivity analysis  
The primary outcome (i.e., occurrence of any symp-
tomatic or radiologic stone recurrence yes/no) will 
be analyzed as a binary outcome in a sensitivity 
analysis. 
3.5.2021 
Data still blinded; change imple-
mented without inspection of 
data 
 
4.0 
For the primary outcome as well as for the number 
of symptomatic stone events we will present a 
Kaplan-Meier curve including the events occurring 
in the first 6 weeks of the study and perform a land-
mark analysis at the 6 weeks landmark point. 
9.11.2021 
Data still blinded; change imple-
mented without inspection of 
data 
4.0 
Definition 
Diabetes is defined as the occurrence of HbA1c 
6.5% or higher; or treated (oral or sc antidiabetic or 
insulin). 
9.11.2021 
Data still blinded; change imple-
mented without inspection of 
data