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Home › Conditions › X-linked hypophosphatemia

X-linked hypophosphatemia

Part of Malnutrition

2 published articles · Updated continuously

Clinical Trial Landscape

Clinical Trials for X-linked hypophosphatemia

10 trials tracked for X-linked hypophosphatemia: 4 in phase 3 or 4 and 3 with published results. The most-cited published study has 370 citations.

10Trials tracked
4Phase 3 & 4
0Recruiting
3With published results
Phase distribution
Phase 4 1 Phase 3 3 Phase 2 5 Phase 1 1
  1. Phase 3 Efficacy and Safety of Burosumab Versus Oral Phosphate and Active Vitamin D Treatment in Pediatric Patients With XLH Completed · 370 cited
  2. Phase 3 Study of KRN23 in Adults With X-linked Hypophosphatemia (XLH) Completed · 345 cited
  3. Phase 3 Open Label Study of KRN23 on Osteomalacia in Adults With X-linked Hypophosphatemia (XLH) Completed · 17 cited
  4. Phase 4 Examining the Effect of Burosumab on Muscle Function Completed
  5. Phase 2 A Repeated Study of KRN23 in Adults With X-Linked Hypophosphatemia Completed
  6. Phase 2 Study of the Safety, Pharmacodynamics (PD) and Efficacy of KRN23 in Children From 1 to 4 Years Old With X-linked Hypophosphatemia (XLH) Completed
Show 4 more trials
  1. Phase 2 An Extension Study of KRN23 in Adults With X-Linked Hypophosphatemia Completed
  2. Phase 2 Long-Term Extension Study of KRN23 in Adult Subjects With X-Linked Hypophosphatemia (XLH) Completed
  3. Phase 2 Study of KRN23 (Burosumab), a Recombinant Fully Human Monoclonal Antibody Against Fibroblast Growth Factor 23 (FGF23), in Pediatric Subjects With X-linked Hypophosphatemia (XLH) Completed
  4. Phase 1 Calcitriol Monotherapy for X-Linked Hypophosphatemia Completed

Showing the 10 most-cited and recently-updated of 10 trials. Browse the full registry →

Trial data sourced from ClinicalTrials.gov. Counts describe the research landscape and are not a treatment recommendation. Informational only — not medical advice.

What the trials found Updated — new results For clinicians

X-linked hypophosphatemia: what the trials found

Burosumab (KRN23) consistently improves serum phosphate levels in patients with X-linked hypophosphatemia (XLH). In multiple phase 2 and 3 trials, burosumab significantly increased serum phosphorus to above the lower limit of normal (LLN) in the majority of patients (92.6% at week 24 in 4; 92.9% in 5; 100% in 8; p<0.0001 for all). These improvements were sustained over time, with significant increases in serum phosphorus at various time points (p<0.0001) 8910. Additionally, burosumab significantly improved radiographic outcomes, as measured by the Radiographic Global Impression of Change (RGI-C) global score at week 40 (p<0.0001) 3 and week 64 (p=0.0002) 3, and reduced rickets severity (RSS total score, p<0.0001) 9. Bone histology also improved, with significant reductions in osteoid volume/bone volume (OV/BV) and osteoid thickness (O.Th) at week 48 (p<0.0001) 5.

Burosumab also showed benefits in patient-reported outcomes. In a phase 3 trial, burosumab significantly improved stiffness as measured by the WOMAC stiffness score (p=0.0106) 4, although the improvement in worst pain (BPI Q3) did not reach statistical significance (p=0.0919) 4. In a phase 2 trial, burosumab reduced serum iPTH levels, though the change was not statistically significant (p=0.1366) 8. Notably, a phase 4 trial found that burosumab did not significantly affect skeletal muscle ATP synthesis rate (p=0.4147) or intracellular phosphate concentration in muscle (p=0.6957), despite significantly increasing serum phosphate (p<0.0001) 2.

Recent results — preliminary, needs further review

  • A phase 1 trial of calcitriol in adults and children with XLH showed no significant changes in serum phosphate (p=0.318), TmP/GFR (p=0.114), or rickets score (p=0.215) at 12 months 1. These findings are not yet corroborated by other trials.

For the clinician treating this condition

  • Burosumab is effective in raising serum phosphate levels and improving radiographic outcomes in XLH, with consistent benefits across multiple trials.
  • Burosumab may improve stiffness but did not show significant pain reduction in one trial; muscle ATP synthesis was not significantly affected.
  • Calcitriol showed no significant benefit in a small phase 1 trial, but this requires further investigation.

AI synthesis of 8 cited trials, updated Jun 29, 2026. Informational only — not medical advice; trial data sourced from ClinicalTrials.gov. How we use AI.

HCP Mode — summaries include clinical detail, trial data, and statistical outcomes.
Patient Mode — summaries use plain language, avoiding clinical jargon.
FDA Approves Crysvita (burosumab) for X-Linked Hypophosphatemia and Tumor-Induced Osteomalacia
Pediatrics FDA Approval
FDA Approves Crysvita (burosumab) for X-Linked Hypophosphatemia and Tumor-Induced Osteomalacia FDA approves new drug Crysvita for rare bone diseases in children and adults
FDA approved Crysvita (burosumab) for X-linked hypophosphatemia (XLH) in patients 6 months and older and for tumor-induced osteomalacia (TIO…
The FDA approved Crysvita (burosumab) for X-linked hypophosphatemia (XLH) and tumor-induced osteomalacia (TIO).
FDA Apr 29, 2026
Substudy of Phase 3 trials: Nonfasting burosumab phosphorus levels in XLH patients remain stable after meals
Drug Pipeline
Substudy of Phase 3 trials: Nonfasting burosumab phosphorus levels in XLH patients remain stable after meals Burosumab Patients May Skip Fasting Before Blood Tests
This abstract describes a substudy of Phase 3 clinical trials evaluating burosumab in adults and children with X-linked hypophosphatemia.
Imagine rushing your child to a morning blood draw, stomach empty, hungry and fussy—only to find out the results might not even require fast…
Apr 24, 2026