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Burosumab for Fibroblast Growth Factor-23 Mediated Hypophosphatemia in Fibrous Dysplasia | Clinical Trials | Clareo Health

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COMPLETEDPhase 2NCT05509595

Burosumab for Fibroblast Growth Factor-23 Mediated Hypophosphatemia in Fibrous Dysplasia

Background: Fibrous dysplasia (FD) is a disorder that affects bone growth. Affected bone tissue is weakened, and people with FD are prone to deformities, fractures, and other problems. People with FD...

Lead sponsor: National Institute of Dental and Craniofacial Research (NIDCR)•1 U.S. locations•View source on ClinicalTrials.gov

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Lead Sponsor

National Institute of Dental and Craniofacial Research (NIDCR)

Study Description: This will be a phase 2, open-label, single-arm study to evaluate the safety and efficacy of burosumab to normalize serum phosphate levels in subjects with fibrous dysplasia (FD) and fibroblast growth factor 23 (FGF23)-mediated hypophosphatemia. Objectives: Primary Objective: -Evaluate the efficacy of burosumab to normalize serum phosphate levels in subjects with FD and FGF23-mediated hypophosphatemia at 48 weeks. Secondary Objectives: * Evaluate the efficacy of burosumab to normalize serum phosphate levels in subjects with FD and FGF23-mediated hypophosphatemia at 24 weeks. * Evaluate the safety and tolerability of burosumab in patients with FD. * Evaluate the effect of burosumab on increasing serum phosphate and additional mineral markers. * Evaluate the impact of burosumab on FD lesion activity. * Evaluate the effect of burosumab on functional parameters. * Evaluate the effect of burosumab on pain and health-related quality of life. Endpoints: Primary Endpoint: -The proportion of subjects achieving serum phosphate levels within the target range (Z-score -1 to +2) at Week 48. Secondary Endpoints: * Proportion of subjects achieving serum phosphate levels within the target range (Z-score -1 to +2) at Week 24. * Adverse events and clinical safety laboratory tests for up to 4 weeks after the final burosumab dose (48 weeks for adult subjects, 50 weeks for pediatric subjects). * Change and percent change from baseline to post-baseline visits in serum phosphate, serum 1,25(OH)2D, ratio of renal tubular maximum reabsorption rate of phosphate to glomerular filtration rate (TmP/GFR). * Change in FD lesion activity using Fluorine-18 Sodium Fluoride Positron Emission Tomography/Computed Tomography (18F-NaF PET/CT) total lesion activity from baseline to 48 weeks * Change and percent change in serum bone turnover markers, including procollagen 1 N-terminal propeptide (P1NP), beta crosslaps C-telopeptides (CTX), osteocalcin, and bone-specific alkaline phosphatase from baseline to 48 weeks. * Change in FD lesion histology and cell proliferation as assessed by minimally invasive bone biopsies from baseline to 48 weeks (adults with capacity to consent only) from baseline to 48 weeks * Skeletal changes assessed on skeletal survey at baseline and 48 weeks * Change from baseline to 48 weeks in: * Muscle strength * Range-of-motion * Walking speed (9-minute walk) Change from baseline to 48 weeks in patient reported outcomes measures: * Short Form Health Survey 36 (SF-36): adults * Short Form Health Survey 10 (SF-10): children * Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Intensity: Pediatric and Parent Proxy version 1.0, Adult version 2.0 * PROMIS Pain Interference: Pediatric and Parent Proxy v 2.0, Adult v 1.1 * PROMIS Mobility: Pediatric and Parent Proxy version 2.0, Adult Mobility Lower Extremity v 1.0 * PROMIS Fatigue: Pediatric and Parent Proxy v 2.0, Adult FACIT 13a v1.0 * Activities of Daily Living Questions: adults and children

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Data from ClinicalTrials.govLast updated on ClinicalTrials.gov: February 2, 2026Terms

Trial snapshot

StatusCOMPLETED

PhasePHASE2

Enrollment12

Start dateDec 2022

Last updatedFeb 2, 2026

Condition

Fibrous Dysplasia Of Bone

Locations shown

National Institutes of Health Clinical Center

Bethesda, Maryland

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Data Source & Attribution

This clinical trial information is sourced from ClinicalTrials.gov, a service of the U.S. National Institutes of Health.

ClinicalTrials.gov last update: February 2, 2026Data synced to Clareo: May 25, 2026

Modifications: This data has been reformatted for display purposes. Eligibility criteria have been parsed into inclusion/exclusion sections. Location data has been geocoded to enable distance-based search. For the authoritative and most current information, please visit ClinicalTrials.gov.

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