Burosumab-twza

Class: Electrolytic, Caloric, and Water Balance Agents; Miscellaneous
Chemical Name: Disulfide with human monoclonal KRN23 light chain, anti-(human fibroblast growth factor 23) (human monoclonal KRN23 heavy chain), immunoglobulin G1 dimer
Molecular Formula: C₆₃₈₈H₉₉₀₄N₁₇₀₀O₂₀₀₆S₄₆
CAS Number: 1610833-03-8
Brands: Crysvita

Medically reviewed by Drugs.com on Jun 7, 2022. Written by ASHP.

Introduction

Recombinant fully human IgG₁ monoclonal antibody to human fibroblast growth factor 23 (FGF23), a bone-derived hormone that regulates phosphate and vitamin D homeostasis.

Uses for Burosumab-twza

X-linked Hypophosphatemia

Management of X-linked hypophosphatemia (previously known as familial vitamin D-resistant rickets) (designated an orphan drug by FDA for use in this condition).

Improves serum phosphorus concentrations and reduces osteomalacia-related bone lesions (e.g., bone histomorphometric parameters, active fractures) in adults.

Improves serum phosphorus concentrations and radiographic measures of rickets severity in pediatric patients.

Burosumab-twza Dosage and Administration

General

• Discontinue oral phosphate supplements and activated vitamin D analogs (e.g., calcitriol) 1 week prior to initiation of burosumab.

• Initiate burosumab therapy only if fasting serum phosphorus concentration is less than reference range for age; manufacturer states that drug initiation is contraindicated if serum phosphorus is within or exceeds normal range for age.

Restricted Distribution

Available only from a limited network of specialty pharmacies. Contact manufacturer for additional information.

Administration

Sub-Q Administration

A clinician should administer the drug.

Burosumab-twza injection is a clear to slightly opalescent, colorless to pale brown-yellow solution. Discard if solution is discolored or cloudy or if any particles or foreign particulate matter is present.

Inject sub-Q into upper arms, upper thighs, buttocks, or any quadrant of the abdomen; rotate sites. Do not inject into moles, scars, or areas where the skin is tender, bruised, erythematous, hard, or not intact.

If total volume of dose >1.5 mL, divide and administer at 2 separate injection sites; do not administer >1.5 mL at any 1 site.

If a dose is missed, administer missed dose as soon as possible.

Dosage

Pediatric Patients

X-linked Hypophosphatemia

Initial Dosage

Pediatric patients 1 to <18 years of age: 0.8 mg/kg every 2 weeks. Round dose to nearest 10 mg (minimum initial dose 10 mg). Do not exceed 90 mg.

Dosage Titration

Adjust dosage no more frequently than every 4 weeks to maintain fasting serum phosphorus concentrations within reference range for age.

Measure fasting serum phosphorus concentrations every 4 weeks for the first 3 months of therapy, then as clinically appropriate thereafter. Measure fasting serum phosphorus concentrations 4 weeks after dos