An Early Phase 1 interventional study of Calcitriol in X-linked Hypophosphatemia, Hypophosphatemic Rickets and Hypophosphatemic Rickets, X-Linked Dominant, sponsored by Massachusetts General Hospital. Completed at 1 site in United States. Open to participants aged 3 Years to 70 Years. Per ClinicalTrials.gov, last updated 2026-05-07.
Sponsored by Massachusetts General Hospital · Early Phase 1, Interventional, and Treatment
Children and adults with XLH recruited will be treated with calcitriol alone (without phosphate supplementation) for one year, during which the calcitriol dose will be escalated during the first 3 months of therapy. The investigators hypothesize that treatment of adults and children with XLH alone will improve serum phosphate levels and skeletal mineralization without causing an increase in kidney calcifications. The study will also examine if calcitriol therapy will improve growth in children.
49 studies on the registry are indexed under Familial Hypophosphatemic Rickets; 8 are open to participants now.
This study's enrollment of 16 is below the median of 28 across 29 interventional studies indexed under Familial Hypophosphatemic Rickets.
Browse Familial Hypophosphatemic Rickets studies →Massachusetts General Hospital is the lead sponsor of 2,586 studies on the registry; 447 are open to participants now.
Of its 222 completed or terminated interventional studies of FDA-regulated products, 168 (76%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
GFR and eGFR (kidney filtering)
GFR (glomerular filtration rate) is how much blood the kidneys filter each minute. It is usually estimated from a blood test — eGFR, by formulas such as CKD-EPI or MDRD — and some studies ask for it to be measured directly instead. Usually given in mL/min/1.73 m².
Check the method, the units and the minimum the study states. A value of 90 or above is in the normal-or-high range, but kidney damage can show in other tests too.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
DSM diagnostic criteria
The American Psychiatric Association’s manual of mental health diagnoses. DSM-5 (2013, revised as DSM-5-TR in 2022) replaced DSM-IV, and some studies still name the older edition. “Meets DSM criteria for …” means diagnosed by that edition’s diagnostic criteria, usually by a clinician in an interview.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adults with X-linked hypophosphatemia will be treated with optimized doses of calcitriol (without phosphate supplementation) for one year
Drug: Calcitriol
Children (age 3-17) with X-linked hypophosphatemia will be treated with optimized doses of calcitriol (without phosphate supplementation) for one year
Drug: Calcitriol
Adults and children (age 3-17) with X-linked hypophosphatemia will be treated with calcitriol therapy without phosphate supplementation. Doses of calcitriol will be escalated and optimized in the first three months of the study. Calcitriol is an oral medication taken once a day.
Also known as: 1,25 dihydroxyvitamin D
Change in Serum Phosphate in Adults and Children With XLH Between Baseline and 12 Months
serum phosphate
Time frame: baseline and 12 months
Change From Baseline in TmP/GFR in Adults and Children With XLH
a measure of kidney resorption of phosphate
Time frame: baseline and 12 months
Rickets Score for Children With XLH
a score of rickets severity determined by reading x-rays of wrists and knees (10 point Thacher score with 0 being normal and 10 being severe)
Time frame: baseline and 12 months
Change From Baseline in Nephrocalcinosis Grade
determine if there is change in amount of calcifications in the kidneys: graded from grade 0 (normal) to grade IV (stone formation, solitary focus of echos at the tip of the renal pyramid)
Time frame: baseline and 12 months
Growth in Children With XLH
Z-score of growth (this is full name of variable)- number represents standard deviation above or below the known mean of the general population at the corresponding age. Z score that is positive is above the mean, negative is below the mean.
Time frame: baseline and 12 months
6 children with XLH were enrolled - Due to COVID and approval of burosumab, difficult to recruit children with XLH into trial 10 adults with XLH were enrolled
| Milestone | Adults With XLH | Children With XLH |
|---|---|---|
| Started | 10 | 6 |
| Completed | 8 | 6 |
| Not completed | 2 | 0 |
| Withdrew: Lost to follow-up | 1 | 0 |
| Withdrew: Withdrawal by subject | 1 | 0 |
serum phosphate
| mg/dl | Adults With XLH | Children With XLH |
|---|---|---|
| Change in Serum Phosphate in Adults and Children With XLH Between Baseline and 12 Months | 2.6 ± 0.5 | 2.1 ± 0.3 |
a measure of kidney resorption of phosphate
| percent | Adults With XLH | Children With XLH |
|---|---|---|
| Change From Baseline in TmP/GFR in Adults and Children With XLH | 88.49 ± 3.6 | 89.08 ± 5.9 |
a score of rickets severity determined by reading x-rays of wrists and knees (10 point Thacher score with 0 being normal and 10 being severe)
| rickets score | Children With XLH |
|---|---|
| Rickets Score for Children With XLH | 1.6 ± 0.5 |
determine if there is change in amount of calcifications in the kidneys: graded from grade 0 (normal) to grade IV (stone formation, solitary focus of echos at the tip of the renal pyramid)
| nephrocalcinosis score | Adults With XLH | Children With XLH |
|---|---|---|
| Change From Baseline in Nephrocalcinosis Grade | 1.15 ± 0.82 | 1.11 ± 0.97 |
Z-score of growth (this is full name of variable)- number represents standard deviation above or below the known mean of the general population at the corresponding age. Z score that is positive is above the mean, negative is below the mean.
| z score | Children With XLH |
|---|---|
| Growth in Children With XLH | -1.5 ± 1.1 |
Collected over from enrollment visit through 12 months. Non-serious events are listed at a 0% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Adults With XLH | 0/10 (0%) | 0/10 (0%) | 2/10 (20%) |
| Children With XLH | 0/6 (0%) | 1/6 (16.7%) | 5/6 (83.3%) |
| Event | Adults With XLH | Children With XLH |
|---|---|---|
| Tooth abscessMusculoskeletal and connective tissue disorders | 0/10 | 1/6 |
| Event | Adults With XLH | Children With XLH |
|---|---|---|
| HypercalciuriaRenal and urinary disorders | 0/10 | 2/6 |
| bubble in gums that looks like tooth abscess but did not require treatmentMusculoskeletal and connective tissue disorders | 1/10 | 1/6 |
| gingival inflammationMusculoskeletal and connective tissue disorders | 0/10 | 1/6 |
| ConstipationGastrointestinal disorders | 0/10 | 1/6 |
| strep pharyngitisInfections and infestations | 0/10 | 1/6 |
| fatigueGeneral disorders | 0/10 | 1/6 |
| stable fibrous cortical defect in right femurMusculoskeletal and connective tissue disorders | 0/10 | 1/6 |
| elevated LFTsMusculoskeletal and connective tissue disorders | 1/10 | 0/6 |
| Age, Continuous(years) | Adults With XLH | Children With XLH | Total |
|---|---|---|---|
| Mean | 29.2 ± 11.6 | 11.1 ± 3.6 | 22.44 ± 12.31 |
| Sex: Female, Male(Participants) | Adults With XLH | Children With XLH | Total |
|---|---|---|---|
| Female | 9 | 4 | 13 |
| Male | 1 | 2 | 3 |
| Race (NIH/OMB)(Participants) | Adults With XLH | Children With XLH | Total |
|---|---|---|---|
| American Indian or Alaska Native | 0 | 0 | 0 |
| Asian | 0 | 0 | 0 |
| Native Hawaiian or Other Pacific Islander | 0 | 0 | 0 |
| Black or African American | 1 | 0 | 1 |
| White | 9 | 6 | 15 |
| More than one race | 0 | 0 | 0 |
| Unknown or Not Reported | 0 | 0 | 0 |
| Ethnicity (NIH/OMB)(Participants) | Adults With XLH | Children With XLH | Total |
|---|---|---|---|
| Hispanic or Latino | 0 | 0 | 0 |
| Not Hispanic or Latino | 10 | 6 | 16 |
| Unknown or Not Reported | 0 | 0 | 0 |
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No
This study is completed, as verified in Mar 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
Studies of the drug tested here: Calcitriol
Familial Hypophosphatemic Rickets →
Massachusetts General Hospital →