RecruitingNot applicableNCT06921720
Connective Tissue
X-Linked Hypophosphatemia
Also known as XLH, X-linked hypophosphatemic rickets, PHEX mutation, vitamin D-resistant rickets
X-linked hypophosphatemia is the most common hereditary form of rickets, caused by loss-of-function variants in PHEX, a phosphate-regulating endopeptidase that normally suppresses FGF23 production; PHEX deficiency leads to inappropriately e
ORPHA:89936 ↗Gene PHEXPrevalence 1 in 20,000Onset Early childhood (typically age 1–2 when walking begins)Genetic — X-linked dominant
5
studies recruiting now
as of 7 Sept 2026
52
studies registered in total
as of 7 Sept 2026
21
countries with a recruiting site
as of 7 Sept 2026
19 Sept 2025
most recent study posted
among recruiting studies
Recruiting trials
RecruitingNCT03193476
Registry for Patients With X-Linked Hypophosphatemia
RecruitingNCT07183579
Effective Dosing of Burosumab in XLH
RecruitingPhase 1 / Phase 2NCT06525636
A First-in-human Study of KK8123 in Adults With X-linked Hypophosphatemia
RecruitingNCT06065852
National Registry of Rare Kidney Diseases
Showing the 5 most recently updated recruiting studies, as recorded 7 Sept 2026. Live status on each study page.
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Countries with at least one recruiting site among the studies above, 7 Sept 2026. Tap a country to search trials there.
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About X-Linked Hypophosphatemia
X-linked hypophosphatemia is the most common hereditary form of rickets, caused by loss-of-function variants in PHEX, a phosphate-regulating endopeptidase that normally suppresses FGF23 production; PHEX deficiency leads to inappropriately elevated circulating FGF23, renal phosphate wasting, and impaired vitamin D activation. The resulting hypophosphataemia causes defective skeletal mineralisation, bowed legs, growth retardation, dental abscesses from abnormal dentine, and musculoskeletal pain throughout life. Burosumab, an anti-FGF23 monoclonal antibody, represents targeted therapy and has transformed the treatment landscape.
Common clinical features
Bowing of the lower limbs appearing when weight-bearing beginsShort stature and growth retardationRachitic changes on skeletal radiographyDental abscesses without obvious dental caries due to abnormal dentineBone pain and muscle weaknessCraniosynostosis in childhoodEnthesopathy (calcification of tendons and ligaments) in adults
From Orphanet’s phenotype annotations (CC BY 4.0). Not a complete list.
Treatments being studied
2 in clinical development, from Open Targets (CC BY 4.0). Not medical advice.
Phase 3Burosumab (Crysvita)
Phase 1 (early)Calcitriol (Calcijex)
Before you apply
Things trial teams commonly ask about for X-Linked Hypophosphatemia. Not eligibility rules; those are set by each study.
- Serum phosphorus, TRP (tubular reabsorption of phosphate), and FGF23 levels are key biomarkers at screening — ensure these are drawn fasting and that current conventional therapy (phosphate and calcitriol) is documented.
- Prior or current burosumab treatment is a frequent exclusion criterion in investigational trials; confirm last dose date and current treatment regimen with the trial coordinator.
- Wrist and knee radiographs graded for rachitic severity (Thacher score or equivalent) are standard baseline requirements in paediatric trials.
Related conditions
Information, not medical advice. Trial listings are shown as recorded on ClinicalTrials.gov; whether any study is right for you is a decision for you and your clinicians, and eligibility is decided by each research team. Disease information from Orphanet (CC BY 4.0).