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

NCT05509595 | Completed Phase 2 Results FDA Drug

• 2 other identifiers: 10000798000798-D
• Study Type: interventional
• Target: 12
• Locations: 1 country
• Sites: 1

Brief Summary

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 may also have low blood phosphate levels. This can make bones even weaker. Better treatments are needed. Objective: To test a study drug (burosumab) in people with FD who have low blood phosphate levels. Eligibility: People aged 1 year or older who have FD and low blood phosphate levels. Design: Participants will visit the NIH 3 times in 48 weeks. Each visit will last 5 to 7 days. Participants will self-inject burosumab under the skin in their belly, upper arm, or thigh. They (or a caregiver) will do this at home 1 or 2 times a month. They will be trained in person on how to inject the drug. Home injections will be guided via telehealth. During NIH visits, participants will have a physical exam with blood and urine tests. They will have x-rays of different parts of their body. They will have a radioactive tracer injected into their vein; then they will have a bone scan. They will have tests to assess their strength, walking, and movement. They will complete questionnaires about their pain, mobility, and fatigue levels. Adult participants may have bone biopsies. These will be done under anesthesia with sedation. Small samples of FD-affected bone will be removed for study. Between NIH visits, participants will go to a local laboratory for blood and urine tests. Child participants will have an additional follow-up visit 2 weeks after the final NIH visit.

Conditions

Fibrous Dysplasia Of Bone

Keywords

McCune-Albright Syndrome; Rickets; Osteomalacia; Metabolic Bone Disorders

Outcome Measures

Primary Outcomes (1)

• Proportion of Participants With Serum Phosphate Levels Within the Target Range at Week 48

  The proportion of participants who achieved serum phosphate levels within the target range (Z-score -1 to +2) at week 48. Analysis was done by dividing the number of number of participants who achieved serum level by the number of participants analyzed.

  Week 48

Secondary Outcomes (34)

• Participants With Adverse Event by Grade

  48 weeks for adult participants; 50 weeks for pediatric participants

• Participants With Related Adverse Event

  48 weeks for adult participants; 50 weeks for pediatric participants

• Proportion of Participants With Serum Phosphate Levels Within the Target Range at Week 24

  Week 24

• Proportion of Participants With Serum Phosphate Levels Above the Target Range (Z-score >+2)

  Between baseline and week 48

• Change in Serum Phosphate Level

  Week 48 minus baseline

Study Arms (1)

Treatment with burosumab

EXPERIMENTAL

Participants with Fibrous dysplasia/McCune-Albright syndrome (FD/MAS) and hypophosphatemia receive burosumab subcutaneously dosed to the nearest 10mg. Pediatric participants receive 0.8mg/kg subcutaneously every two weeks for 48 weeks. Adult participants receive 0.5mg/kg subcutaneously every four weeks, with the option to receive dose every two weeks, for 48 weeks. All participants receive a minimum dose of 10mg/dose and a maximum of 90mg/dose.

Drug: Burosumab

Interventions

Burosumab DRUG

Human recombinant monoclonal antibody to fibroblast growth factor-23 (FGF23)

Treatment with burosumab

Eligibility Criteria

• Age: 1 Year - 99 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64), Older Adult (65+)

You may qualify if:

• In order to be eligible to participate in this study, an individual must meet all of the following criteria:
• Confirmed diagnosis of fibrous dysplasia
• Serum phosphate \<10th percentile for age and sex, AND intact serum FGF23 \>=30 pg/mL
• Age \>=1 year
• Provision of signed and dated informed consent/assent form
• Stated willingness of subject or Legally Authorized Representative (LAR) to comply with all study procedures and availability for the duration of the study
• For females of reproductive potential: agreement to use highly effective contraception for during study participation. Highly effective contraception methods include:
• Total abstinence (when this is in line with the preferred and usual lifestyle of the participant). Periodic abstinence (e.g., calendar, ovulation, symptothermal, postovulation methods) and withdrawal are not acceptable methods of contraception
• Female sterilization (have had surgical bilateral oophorectomy with or without hysterectomy) or tubal ligation at least six weeks before taking study treatment.
• Male sterilization (at least 6 months prior to screening). For female participants on the study the vasectomized male partner should be the sole partner for that participant.
• Combination of the following (a+b or a+c, or b+c):
• Use of oral, injected or implanted hormonal methods of contraception or other forms of hormonal contraception that have comparable efficacy (failure rate \<1%), for example hormone vaginal ring or transdermal hormone contraception
• Placement of an intrauterine device (IUD) or intrauterine system (IUS)
• Barrier methods of contraception: Condom or Occlusive cap (diaphragm or cervical/vault caps) with spermicidal foam/gel/film/cream/vaginal suppository
• For males of reproductive potential: use of condoms or other methods described above to ensure effective contraception with partner

You may not qualify if:

• An individual who meets any of the following criteria will be excluded from participation in this study:
• Pregnancy or lactation
• Known allergic reactions to burosumab or drug component
• Treatment with another investigational drug within 30 days of screening
• Treatment with burosumab within 30 days of screening
• Have any condition which in the opinion of the PI could present a concern for subject safety or difficulty with data interpretation
• Severe renal impairment or end stage renal disease, defined as: pediatric patients with estimated glomerular filtration rate (eGFR) 15 mL/min/1.73m2 to 29 mL/min/1.73m2 or end stage renal disease (eGFR \< 15 mL/min/1.73m2), adult patients with creatinine clearance (CLcr) 15 mL/min to 29 mL/min or end stage renal disease (CLcr \< 15 mL/min)

Sponsors & Collaborators

• National Institute of Dental and Craniofacial Research (NIDCR): lead

Study Sites (1)

National Institutes of Health Clinical Center

Bethesda, Maryland, 20892, United States

Location

Related Links

• NIH Clinical Center Detailed Web Page

MeSH Terms

Conditions

Fibrous Dysplasia of Bone; Fibrous Dysplasia, Polyostotic; Rickets; Osteomalacia; Bone Diseases, Metabolic

Interventions

burosumab

Condition Hierarchy (Ancestors)

Osteochondrodysplasias; Bone Diseases, Developmental; Bone Diseases; Musculoskeletal Diseases; Metabolic Diseases; Nutritional and Metabolic Diseases; Calcium Metabolism Disorders; Vitamin D Deficiency; Avitaminosis; Deficiency Diseases; Malnutrition; Nutrition Disorders

Results Point of Contact

• Title: Dr. Alison Boyce
• Organization: National Institute of Dental and Craniofacial Research

alison.boyce@nih.gov

+1 301 827 4802

Study Officials

• Alison M Boyce, M.D.

  National Institute of Dental and Craniofacial Research (NIDCR)

  PRINCIPAL INVESTIGATOR

Publication Agreements

• PI is Sponsor Employee: Yes

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: NA
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: SINGLE GROUP
• Sponsor Type: NIH
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 19, 2022
• First Posted: August 22, 2022
• Study Start: December 7, 2022
• Primary Completion: November 18, 2024
• Study Completion: November 18, 2024
• Last Updated: February 2, 2026
• Results First Posted: February 2, 2026

Record last verified: 2026-01-15

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, SAP, ICF, CSR
• Time Frame: Results from this trial will be made available 12 months after the primary study completion date
• Access Criteria: Investigators from NIH and Ultragenyx and Kyowa Kirin will consider requests from qualified researchers for access to clinical data.

Locations

US (1)