A Phase 4 interventional study of Burosumab Injection [Crysvita] in X-linked Hypophosphatemia, sponsored by Yale University. Completed at 1 site in United States. Open to participants aged 18 Years to 65 Years. Per ClinicalTrials.gov, last updated 2023-08-24.
Sponsored by Yale University · Phase 4, Interventional, and Other
Help build ClinicalTrials.gg — short surveys, remote interviews or testing, in your language. Take part →
Among 18 studies testing burosumab in Familial Hypophosphatemic Rickets — none open to participants now, none under way, none of them phase 3. burosumab · Familial Hypophosphatemic Rickets.
Among the 18 studies testing burosumab in Familial Hypophosphatemic Rickets, this one is the 18th largest by enrollment, is one of 2 that started in 2019, is one of 4 in phase 4, and was the 13th registered.
49 studies on the registry are indexed under Familial Hypophosphatemic Rickets; 8 are open to participants now.
Browse Familial Hypophosphatemic Rickets studies →None of the 18 studies testing burosumab in Familial Hypophosphatemic Rickets is open now. The open studies under Familial Hypophosphatemic Rickets, anywhere →
burosumab: first FDA approval 2018 (CRYSVITA), first EMA approval 2018. What it is approved for, and how studies give it, is on its page →
Of the 4 Familial Hypophosphatemic Rickets studies recruiting now, 2 set no upper age limit and 2 stop at 75 or younger; 3 take children under 18; 1 takes healthy volunteers.
This study: 18 Years to 65 Years · all sexes · no healthy volunteers.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
18 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 5 · Phase 2 6 · Phase 3 6 · Phase 4 4
First in 2008; this study’s year is marked. 2 started in 2019.
This study's enrollment of 10 is below the median of 28 across 29 interventional studies indexed under Familial Hypophosphatemic Rickets.
Median enrollment 26 across the 18 interventional studies. Of the 17 that completed or were terminated, 9 (53%) have results posted.
This tab as a report to print or save as PDF → With an account.
15 of 18 have an industry lead sponsor. The 6 most frequent:
Yale University is the lead sponsor of 1,772 studies on the registry; 296 are open to participants now.
Of its 221 completed or terminated interventional studies of FDA-regulated products, 129 (58%) have results posted.
Yale University has 3 studies filed under Familial Hypophosphatemic Rickets — fewer than ten, so there is no comparison to draw.
None of the studies under way reaches primary completion within a year.
Among the 18 studies testing burosumab in Familial Hypophosphatemic Rickets, from their registry updates:
Nothing recorded among them since 2026-09-25.
This tab as a report to print or save as PDF → With an account.
Patients with X-linked hypophosphatemia (XLH) often report symptoms of fatigue and weakness particularly after exertion, in addition to their skeletal complaints. In previous trials using KRN23 (same drug as burosumab/Crysvita®), patients report these symptoms improve. The investigators wish to test this hypothesis directly by measuring muscle energy when patients begin treatment with Crysvita® for the first time.
X-linked hypophosphatemia is a skeletal dysplasia. The mineralized tissue complications of XLH have been the focus of investigative studies seeking to understand its pathogenesis, as well as studies directed at new therapies. However, in addition to their skeletal complaints, patients with XLH have among their most frequent symptoms, fatigue and weakness, which manifest as both a generalized sense of a lack of energy as well as a more specific feeling that their muscular function is impaired. Objectively, patients complain of fatigue after exertion, when otherwise they do not think they should expect to feel so spent. These symptoms occur in individuals who otherwise have good cardiovascular and respiratory health, so co-morbidities are unlikely to explain these pervasive complaints. Anecdotally, the investigators open-label trial data using KRN23 suggest that these symptoms are dramatically ameliorated by treatment with the drug. In a recent study¹, the investigators found that when stressed by a low-phosphate diet, rates of insulin-stimulated myocyte Adenosine triphosphate (ATP) flux were reduced by 50% in an experimental model of systemic hypophosphatemia (the NaPi2a knockout mouse). Moreover, ATP synthetic flux correlated directly with cellular and mitochondrial phosphate uptake in two rodent myocyte cell lines, as well as in freshly isolated myocyte mitochondria. As direct evidence that these preclinical findings are relevant to human hypophosphatemic genetic syndromes we studied a patient with Heredity Hypophosphatemic Rickets with Hypercalciuria (HHRH) who was not being treated at the time of our experiment. In this patient who had a 50% reduction in serum phosphate, muscle ATP content was also significantly reduced ¹. Both of these parameters normalized completely with oral phosphate repletion ¹. These data strongly support the hypothesis that reduced muscle ATP flux may underlie the myopathy seen in patients with XLH. The investigators propose to directly test this hypothesis, in patients about to begin treatment with Crysvita® for the first time.
Muscle tissue phosphorus concentration and ATP flux rates will be assessed in the right gastrocnemius of the lower leg using 31P-NMR (nuclear magnetic resonance) spectroscopy over the course of the 3 month study. The study consists of 5 visits total over 3 months. At visits 1,4 and 5, patients will undergo magnetic resonance (MR) spectroscopy assessments and functional testing along with blood and urine analysis. At visits 1,2 and 3 patients will receive Burosumab/Crysvita® by subcutaneous injection.
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.
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.
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.
Patients will receive Burosumab monthly at visits 1,2 and 3 subcutaneously at a dose of 1.0 mg/kg. Dose may be adjusted as needed.
Drug: Burosumab Injection [Crysvita]
Burosumab/Crysvita SC injection monthly
Also known as: Crysvita
Skeletal Muscle Adenosine Triphosphate (ATP) Synthesis Rate
Rates of mitochondrial phosphorylation activity were assessed in the soleus/gastrocnemius muscle complex of the right calf by 31P magnetic resonance spectroscopy saturation transfer technique (micro-mol/g/min)
Time frame: 2.5 months
Serum Phosphate
measured in mg/dl
Time frame: 2.5 months
Intracellular Phosphate Concentration in Umol/g Muscle
Intracellular phosphorus concentration in skeletal muscle (umol/g muscle)
Time frame: 2.5 months
Six-minute Walk Test
functional testing outcome measured in meters
Time frame: 2.5 months
Sit to Stand
functional testing outcome measured in the number completed in 30 seconds
Time frame: 2.5 months
Timed up and go Test
functional testing outcome measured in seconds
Time frame: 2.5 months
| Milestone | Patients With XLH |
|---|---|
| Started | 10 |
| Completed | 10 |
| Not completed | 0 |
Rates of mitochondrial phosphorylation activity were assessed in the soleus/gastrocnemius muscle complex of the right calf by 31P magnetic resonance spectroscopy saturation transfer technique (micro-mol/g/min)
| umol/g/min | Patients With XLH |
|---|---|
| Skeletal Muscle Adenosine Triphosphate (ATP) Synthesis Rate | 9.41 (8.7827 to 10.0333) |
measured in mg/dl
| mg/dL | Patients With XLH |
|---|---|
| Serum Phosphate | 2.85 (2.4231 to 3.2769) |
Intracellular phosphorus concentration in skeletal muscle (umol/g muscle)
| umol/g muscle | Patients With XLH |
|---|---|
| Intracellular Phosphate Concentration in Umol/g Muscle | 2.31 (1.9654 to 2.6446) |
functional testing outcome measured in meters
| meter | Patients With XLH |
|---|---|
| Six-minute Walk Test | 440.4 (388.06 to 492.74) |
functional testing outcome measured in the number completed in 30 seconds
| repetitions | Patients With XLH |
|---|---|
| Sit to Stand | 14.2 (10.8312 to 17.5688) |
functional testing outcome measured in seconds
| second | Patients With XLH |
|---|---|
| Timed up and go Test | 7.47 (6.4473 to 8.4967) |
Collected over 3 months (time of consent to completion of visit 5). Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Patients With XLH | 0/10 (0%) | 1/10 (10%) | 0/10 (0%) |
| Event | Patients With XLH |
|---|---|
| Partial ureteropelvic junction obstruction by staghorn calculusRenal and urinary disorders | 1/10 |
| Age, Categorical(Participants) | Patients With XLH |
|---|---|
| <=18 years | 0 |
| Between 18 and 65 years | 10 |
| >=65 years | 0 |
| Age, Continuous(years) | Patients With XLH |
|---|---|
| Mean | 39.7 ± 11.2 |
| Sex: Female, Male(Participants) | Patients With XLH |
|---|---|
| Female | 8 |
| Male | 2 |
| Ethnicity (NIH/OMB)(Participants) | Patients With XLH |
|---|---|
| Hispanic or Latino | 0 |
| Not Hispanic or Latino | 10 |
| Unknown or Not Reported | 0 |
| Race (NIH/OMB)(Participants) | Patients With XLH |
|---|---|
| American Indian or Alaska Native | 0 |
| Asian | 0 |
| Native Hawaiian or Other Pacific Islander | 0 |
| Black or African American | 0 |
| White | 0 |
| More than one race | 0 |
| Unknown or Not Reported | 10 |
| Region of Enrollment(Participants) | Patients With XLH |
|---|---|
| United States | 8 |
| Canada | 2 |
| Fasting serum phosphate(mg/dL) | Patients With XLH |
|---|---|
| Mean | 1.74 ± 0.43 |
| Serum calcium(mg/dL) | Patients With XLH |
|---|---|
| Mean | 9.30 ± 0.32 |
6 further baseline measures are reported on the registry.
PDFs hosted by the registry, ClinicalTrials.gov.
Plan to share: No
Ran from Nov 2019 to primary completion in Aug 2022, 33 months.
Results were first posted in Aug 2023, 11 months after primary completion.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Aug 2023. 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: Burosumab
Familial Hypophosphatemic Rickets →