Burosumab

Burosumab Brand Name– CRYSViTA

What is Burosumab

Burosumab is a fibroblast growth factor 23 (FGF23) blocking antibody. It is indicated for the treatment of X-linked hypophosphatemia (XLH) in adult and pediatric patients 6 months of age and older.

Burosumab is also indicated for the treatment of tumor-induced osteomalacia (TIO) in adult and pediatric patients 2 years of age and older.

In a placebo-controlled study involving 134 adult patients with XLH, 94% of adults receiving burosumab once a month achieved normal phosphorus concentrations compared to 8% of those receiving placebo.

In pediatric studies, 94% to 100% of patients treated with burosumab every 2 weeks achieved normal phosphorus concentrations. Additionally, there was an improvement in X-ray findings associated with XLH in both children and adults receiving burosumab therapy.

In 2 single-arm, phase 2 trials (n = 14 and n = 13), the mean serum phosphorus levels increased to above the lower limit of normal (LLN) following 24 weeks of burosumab therapy in 50% and 69% of adult patients with TIO.

The safety and efficacy of burosumab in pediatric patients 2 years and older with TIO were extrapolated from adult TIO study data and study and pharmacokinetic data in adults and pediatric patients with XLH.

The use of oral phosphate and active vitamin D analogs is contraindicated during burosumab treatment; discontinue these products 1 week prior to the initiation of burosumab.

Ensure serum phosphorous concentrations are below the reference range for age prior to treatment initiation; monitor serum phosphorus monthly for the first 3 months of treatment and periodically thereafter.

Indications

• hypophosphatemia
• osteomalacia

Side Effects

1. antibody formation
2. back pain
3. constipation
4. cough
5. dental caries
6. dental pain
7. diarrhea
8. dizziness
9. fever
10. headache
11. hyperphosphatemia
12. infection
13. injection site reaction
14. maculopapular rash
15. muscle cramps
16. myalgia
17. nausea
18. rash
19. restless legs syndrome (RLS)
20. spinal cord compression
21. urticaria
22. vitamin D deficiency
23. vomiting

Monitoring Parameters

• serum phosphate

Contraindications

• breast-feeding
• hyperphosphatemia
• pregnancy
• radiation therapy
• renal failure
• renal impairment
• surgery

Interactions

• Calcifediol
• Calcitriol
• Calcium Phosphate, Supersaturated
• Dihydrotachysterol
• Doxercalciferol
• Erdafitinib
• Ibritumomab Tiuxetan
• Paricalcitol
• Potassium Phosphate
• Potassium Phosphate; Sodium Phosphate
• Sodium Phosphate Monobasic Monohydrate; Sodium Phosphate Dibasic Anhydrous
• Vitamin D analogs

Mechanism of Action

• X-linked hypophosphatemia (XLH) is caused by excess fibroblast growth factor 23 (FGF23), which suppresses renal tubular phosphate reabsorption and the renal production of 1,25 dihydroxy vitamin D.
• Burosumab, a human monoclonal immunoglobulin G1 antibody, binds to and inhibits the biological activity of FGF23 restoring renal phosphate reabsorption and increasing the serum concentration of 1,25 dihydroxy vitamin D.⁶³⁰⁸³

Monitoring Parameters

• serum phosphate

Classifications

• Antineoplastic and Immunomodulating Agents
  • Immunomodulating Agents
    • Immunomodulators, Monoclonal Antibodies