Kidney StonesEarly Phase 1NCT07903961
Phosphate & Kidney Stones
A Early Phase 1 study testing Neutral Phosphate in people with Kidney Stones and Calcium Oxalate Kidney Stones, run by University of Chicago at 1 site in United States.
Trial summary
Kidney stones are common and often come back. One reason may be that some people with calcium stones have low phosphate levels in the blood and lose too much phosphate through the kidneys. They may also have high calcium in the urine, which raises the chance of forming stones. Read more about this study
- Who is it for?
- Ages 18 to 70 years
- Conditions the study is for
- Kidney Stones, Calcium Oxalate Kidney Stones, Hypophosphatemia
- What is being tested?
- Neutral Phosphate
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 5 participants
- Where
- 1 siteUnited States
- Study dates
- 31 Oct 2026to 31 Jan 2028
- Phase
- Early Phase 1
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 70 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Age 18-70
- History of at least one calcium oxalate stone
- Hypercalciuria (>250mg/day)
- Hypophosphatemia (<3mg/dL)
Who cannot join
- History of primarily brushite, uric acid, cysteine, or struvite stones.
- History of severe acid-base abnormality, very low (less than 100mg/day) or very high (greater than 1500mg/day) urine phosphate.
- Any participants who cannot stop diuretic medication or alkali supplementation for the course of the study period.
- Use of drugs that can directly affect proximal tubule function (i.e. topiramate).
- Diagnosis of complete distal renal tubular acidosis.
- Diagnosis of chronic kidney disease (defined as eGFR less than 60 ml/min/1.73m2).
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
United States1 site
University of Chicago
Chicago, Illinois, 60637
Megan Prochaska, MD, 773-702-1000 ext. 45488, mprocha2@medicine.bsd.uchicago.edu
About this study
Official title: Pilot Study of Low-Dose Neutral Phosphate Supplementation for Reducing Urine Calcium and Supersaturation in Patients With Recurrent Calcium Oxalate Kidney Stones and Hypophosphatemia
Kidney stones are common and often come back. One reason may be that some people with calcium stones have low phosphate levels in the blood and lose too much phosphate through the kidneys. They may also have high calcium in the urine, which raises the chance of forming stones. In older studies, high doses of phosphate supplements lowered urine calcium and appeared to reduce stone formation, but they sometimes caused stomach and bowel side effects, and phosphate is no longer used for stone prevention. This small pilot study will test a much lower dose of neutral phosphate (250 mg twice daily) for 2 weeks in adults with recurrent calcium oxalate kidney stones, high urine calcium, and low blood phosphate. Participants will collect a 24-hour urine sample and have blood drawn before and after the 2-week period. The study will look at whether the low dose reduces urine calcium and the risk of stone formation in urine. The results will help decide whether a larger study is warranted.
Read the detailed description
Patients who form kidney stones often have lower serum phosphate and higher kidney phosphate losses, largely due to reduced tubular reabsorption. Earlier trials of high-dose phosphate supplementation in patients with idiopathic hypercalciuria reduced urine calcium, and several showed fewer stones. Use of phosphate for stone prevention later declined after a randomized trial of acid phosphate found no difference in stone formation despite lower urine calcium. Studies of neutral or alkaline phosphate, in contrast, did show benefit. Higher doses can also cause gastrointestinal side effects. This pilot tests whether a lower dose can reduce urine calcium while avoiding those negative effects. It is exploratory and will provide preliminary data for a larger grant-funded trial.
This is a single-group, open-label pilot in which all participants receive the same intervention. Before each collection, participants hold certain medications and supplements that could affect urine chemistry, in discussion with their treating physician. Participants complete a baseline 24-hour urine collection at home, followed by a fasting baseline visit at the University of Chicago Medicine Clinical Research Center with vital signs and a blood draw. A coordinator calls at one week to check for side effects and adherence. Participants then repeat the 24-hour urine collection and a fasting visit with vital signs, a blood draw, and a side effect and adherence assessment at 2 weeks.
Urine collections are analyzed by Litholink lab for a full set of stone risk chemistries, and supersaturation values are calculated. Serum is analyzed in the University of Chicago General Chemistry laboratory. Urine and serum samples are frozen and stored for possible later assays. Basic clinical variables are taken from the electronic health record and confirmed by interview. Analysis is descriptive, looking at the change in each participant from baseline to 2 weeks, and no formal hypothesis testing is planned.
- Being tested
- Neutral Phosphate
- Keywords
- Phosphate & Kidney Stones, Kidney stones and hypophosphatemia, Urine Calcium and Supersaturation, Recurrent Calcium Oxalate Kidney Stones
- Medical subject headings
- Kidney Calculi, Hypophosphatemia
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Neutral PhosphateDrug
250 mg of oral neutral phosphate taken twice daily for 2 weeks (500 mg total per day). The study drug is dispensed by the University of Chicago Investigational Drug Service. Participants take it at home and are assessed for side effects and adherence by a 1-week phone call and again at the 2-week study visit.
| Study group | Role | What they receive |
|---|---|---|
| Neutral Phosphate 250 mg Twice Daily | Experimental | Participants receive 250 mg of oral neutral phosphate twice daily for 2 weeks, dispensed by the University of Chicago Investigational Drug Service. Urine calcium and related stone risk measures are collected by 24-hour urine collection and compared before and after the 2-week course. A coordinator calls at 1 week to check for side effects and adherence, and these are assessed again at the final study visit. Receives: Drug: Neutral Phosphate |
What is being measured
The primary outcome is the main question the study is designed to answer.
Change in from urine calcium from baseline (time 0) and 2-weeks (completion) after oral phosphate (250mg twice daily) supplementation
Change in 24-hour urine calcium (mg/day) from baseline to the end of 2 weeks of oral neutral phosphate (250 mg twice daily). Urine is collected over 24 hours at home before the baseline visit and again at 2 weeks, and calcium is measured by Litholink (Labcorp). The change is calculated for each participant as the 2-week value minus the baseline value.
Measured: 2 weeks
Secondary outcomes (2)
Change in Urine Calcium Oxalate Supersaturation
Change in 24-hour urine calcium oxalate supersaturation from baseline to the end of 2 weeks of oral neutral phosphate (250 mg twice daily). Supersaturation is calculated with the EQUIL2 program from the 24-hour urine chemistries measured by Litholink (Labcorp). The change is the 2-week value minus the baseline value for each participant.
Measured: 2 weeks
Change in Urine Calcium Phosphate Supersaturation
Change in 24-hour urine calcium phosphate supersaturation from baseline to the end of 2 weeks of oral neutral phosphate (250 mg twice daily). Supersaturation is calculated with EQUIL2 from the 24-hour urine chemistries measured by Litholink (Labcorp). The change is the 2-week value minus the baseline value for each participant.
Measured: 2 weeks
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted29 Oct 2026
- Study start31 Oct 2026 (estimated)
- Primary completion31 Dec 2027 (estimated)
- Study completion31 Jan 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Kidney StonesStudies of the same condition, open and under way.
- More trials run by University of ChicagoThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Early Phase 1
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 5 participants (estimated)
Sponsor and investigators
- Lead sponsor
- University of Chicago
- Sponsor type
- University, hospital or other
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07903961
- Sponsor's protocol ID
- IRB26-0303
- Status last verified
- Oct 2026
- First submitted
- 22 Oct 2026
- Last updated
- 29 Oct 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
Study at a glance
From the registry record, last updated by the sponsor on 29 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Pilot Study of Low-Dose Neutral Phosphate Supplementation for Reducing Urine Calcium and Supersaturation in Patients With Recurrent Calcium Oxalate Kidney Stones and Hypophosphatemia
- ClinicalTrials.gov ID
- NCT07903961
- Acronym / sponsor ID
- IRB26-0303
- Keywords
- Phosphate & Kidney Stones, Kidney stones and hypophosphatemia, Urine Calcium and Supersaturation, Recurrent Calcium Oxalate Kidney Stones
- Phase
- Early Phase 1
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 5 participants (estimated)
- Lead sponsor
- University of ChicagoUniversity, hospital or other
- Study start
- 31 Oct 2026 (estimated)
- Primary completion
- 31 Dec 2027 (estimated)
- Study completion
- 31 Jan 2028 (estimated)
- First posted
- 29 Oct 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Kidney stones are common and often come back. One reason may be that some people with calcium stones have low phosphate levels in the blood and lose too much phosphate through the kidneys. They may also have high calcium in the urine, which raises the chance of forming stones. In older studies, high doses of phosphate supplements lowered urine calcium and appeared to reduce stone formation, but they sometimes caused stomach and bowel side effects, and phosphate is no longer used for stone prevention. This small pilot study will test a much lower dose of neutral phosphate (250 mg twice daily) for 2 weeks in adults with recurrent calcium oxalate kidney stones, high urine calcium, and low blood phosphate. Participants will collect a 24-hour urine sample and have blood drawn before and after the 2-week period. The study will look at whether the low dose reduces urine calcium and the risk of stone formation in urine. The results will help decide whether a larger study is warranted.
Detailed description
Patients who form kidney stones often have lower serum phosphate and higher kidney phosphate losses, largely due to reduced tubular reabsorption. Earlier trials of high-dose phosphate supplementation in patients with idiopathic hypercalciuria reduced urine calcium, and several showed fewer stones. Use of phosphate for stone prevention later declined after a randomized trial of acid phosphate found no difference in stone formation despite lower urine calcium. Studies of neutral or alkaline phosphate, in contrast, did show benefit. Higher doses can also cause gastrointestinal side effects. This pilot tests whether a lower dose can reduce urine calcium while avoiding those negative effects. It is exploratory and will provide preliminary data for a larger grant-funded trial.
This is a single-group, open-label pilot in which all participants receive the same intervention. Before each collection, participants hold certain medications and supplements that could affect urine chemistry, in discussion with their treating physician. Participants complete a baseline 24-hour urine collection at home, followed by a fasting baseline visit at the University of Chicago Medicine Clinical Research Center with vital signs and a blood draw. A coordinator calls at one week to check for side effects and adherence. Participants then repeat the 24-hour urine collection and a fasting visit with vital signs, a blood draw, and a side effect and adherence assessment at 2 weeks.
Urine collections are analyzed by Litholink lab for a full set of stone risk chemistries, and supersaturation values are calculated. Serum is analyzed in the University of Chicago General Chemistry laboratory. Urine and serum samples are frozen and stored for possible later assays. Basic clinical variables are taken from the electronic health record and confirmed by interview. Analysis is descriptive, looking at the change in each participant from baseline to 2 weeks, and no formal hypothesis testing is planned.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Neutral Phosphate 250 mg Twice Daily | Experimental | Drug: Neutral PhosphateParticipants receive 250 mg of oral neutral phosphate twice daily for 2 weeks, dispensed by the University of Chicago Investigational Drug Service. Urine calcium and related stone risk measures are collected by 24-hour urine collection and compared before and after the 2-week course. A coordinator calls at 1 week to check for side effects and adherence, and these are assessed again at the final study visit. |
Who may qualify
- Ages
- 18 to 70 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- Age 18-70
- History of at least one calcium oxalate stone
- Hypercalciuria (>250mg/day)
- Hypophosphatemia (<3mg/dL)
Key exclusion criteria (6 listed)
- History of primarily brushite, uric acid, cysteine, or struvite stones.
- History of severe acid-base abnormality, very low (less than 100mg/day) or very high (greater than 1500mg/day) urine phosphate.
- Any participants who cannot stop diuretic medication or alkali supplementation for the course of the study period.
- Use of drugs that can directly affect proximal tubule function (i.e. topiramate).
- Diagnosis of complete distal renal tubular acidosis.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Neutral Phosphate250 mg of oral neutral phosphate taken twice daily for 2 weeks (500 mg total per day). The study drug is dispensed by the University of Chicago Investigational Drug Service. Participants take it at home and are assessed for side effects and adherence by a 1-week phone call and again at the 2-week study visit. | Drug | Neutral Phosphate 250 mg Twice Daily |
Primary outcome
Change in from urine calcium from baseline (time 0) and 2-weeks (completion) after oral phosphate (250mg twice daily) supplementation
Time frame: 2 weeks
Change in 24-hour urine calcium (mg/day) from baseline to the end of 2 weeks of oral neutral phosphate (250 mg twice daily). Urine is collected over 24 hours at home before the baseline visit and again at 2 weeks, and calcium is measured by Litholink (Labcorp). The change is calculated for each participant as the 2-week value minus the baseline value.
2 secondary outcomes
Change in Urine Calcium Oxalate Supersaturation
Time frame: 2 weeks
Change in Urine Calcium Phosphate Supersaturation
Time frame: 2 weeks
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 29 Oct 2026.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Early Phase 1 study testing Neutral Phosphate in people with Kidney Stones and Calcium Oxalate Kidney Stones, run by University of Chicago at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 6 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 29 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Early Phase 1 (sometimes called Phase 0) studies give a very small amount of a treatment to a few people, mainly to see how the body handles it.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Megan Prochaska, MD ((773) 702-1000 ext. 45488, mprocha2@medicine.bsd.uchicago.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change in from urine calcium from baseline (time 0) and 2-weeks (completion) after oral phosphate (250mg twice daily) supplementation (time frame: 2 weeks). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 29 Oct 2026.