Crysvita (burosumab-twza) — Medical Mutual

Initial criteria

• Patient has not received oral phosphate and/or active vitamin D analogs within 1 week prior to the start of therapy; AND
• Baseline fasting serum phosphorus level with current hypophosphatemia, defined as a phosphate level below the lower limit of the laboratory normal reference range; AND
• Patient has a reduced tubular resorption of phosphate corrected for glomerular filtration rate (TmP/GFR); AND
• Other causes of hypophosphatemia (e.g., autosomal dominant or recessive hypophosphatemic rickets) have been ruled out; AND
• Must be prescribed by, or in consultation with, a nephrologist or endocrinologist; AND
• Will not be used concomitantly with oral phosphate and/or active vitamin D analogs; AND
• Patient does not have severe renal impairment, defined as a GFR <30 mL/min; AND
• Patient 25-hydroxy vitamin D levels will be monitored at baseline and intermittently and patient will be supplemented with cholecalciferol or ergocalciferol to maintain levels in the normal range for age; AND
• For X-linked Hypophosphatemia (XLH): Patient age ≥ 6 months; AND diagnosis confirmed by either serum FGF23 level >30 pg/mL (children >230 RU/mL, adults >180 RU/mL using EDTA plasma) OR PHEX gene mutation; AND adult patients must have had an inadequate response from oral phosphate and active vitamin D analogs; AND
• For Tumor-induced Osteomalacia (TIO): Patient age ≥ 2 years; AND diagnosis of TIO associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized; AND diagnosis confirmed by serum FGF23 ≥ 100 pg/mL not amenable to cure by surgical excision

Reauthorization criteria

• Patient continues to meet universal and indication-specific relevant criteria; AND
• Absence of unacceptable toxicity from the drug (e.g., severe hypersensitivity reactions, hyperphosphatemia/nephrocalcinosis, severe injection site reactions); AND
• Current serum phosphorus level is not above the upper limit of the laboratory normal reference range; AND
• Demonstrated disease response as indicated by increased serum phosphorus levels, improvement in renal phosphate wasting, reduction in serum alkaline phosphatase activity, improvement in symptoms (e.g., skeletal pain, linear growth), and/or improvement in radiographic imaging of rickets/osteomalacia; AND
• For XLH: Pediatric patients must be re-evaluated at adulthood to determine if continued therapy is necessary (discontinuation/reassessment with oral phosphate and vitamin D analogs); AND
• For TIO: If the patient undergoes treatment of the underlying tumor (surgical excision or radiation), treatment should be interrupted and serum phosphorus reassessed to determine if continued therapy is necessary

Approval duration

initial 6 months, renewal 12 months