State and School Employees' Health Insurance Plan - Crysvita (burosumab-twza)

POLICY NUMBER

S.5.01.541

Crysvita (burosumab-twza)

Please perform a search of the State Health Plan Medical Drug Formulary for drugs administered and billed through the medical setting.

DESCRIPTION

Burosumab is a fibroblast growth factor 23 (FGF23) blocking antibody that binds to and inhibits the biological activity of FGF23, restoring renal phosphate reabsorption and increasing the serum concentration of 1,25 dihydroxy vitamin D. Crysvita (burosumab-twza) is indicated for the treatment of X-linked hypophosphatemia (XLH), also known as vitamin D-resistant rickets, in patients 6 months of age and older, and for the treatment of FGF23-related hypophosphatemia in tumor-induced osteomalacia (TIO) associated with phosphaturic mesenchymal tumors that cannot be curatively resected or localized in adults and pediatric patients 2 years of age and older. 

POLICY

The use of samples by an individual will not be considered current or stable therapy to satisfy Medical Policy requirements.

Initial Evaluation

Crysvita (burosumab-twza) may be considered medically necessary when ALL of the following criteria are met:

1. ONE of the following:

2. 1. The individual is at least 6 months of age AND has a diagnosis of X-linked Hypophosphatemia (XLH) confirmed by at least ONE of the following:

   2. 1. Serum fibroblast growth factor-23 (FGF23) level >30 pg/mL; OR

      2. Mutations in the phosphate regulating gene with homology to endopeptidases located on the X chromosome (PHEX-gene); OR

   3. The individual is at least 2 years of age AND has a diagnosis of tumor-induced osteomalacia (TIO) associated with phosphaturic mesenchymal tumors and BOTH of the following:

   4. 1. Serum fibroblast growth factor (FGF23) level ≥100 pg/mL; AND

      2. The tumor cannot be surgically resected or localized;

3. Baseline fasting serum phosphorus level (see Policy Guidelines) is below the lower limit of the laboratory normal reference range for the individual's age;

4. The individual does not have severe renal impairment (defined as a glomerular filtration rate (GFR) of <30 mL/min);

5. The individual presents with clinical signs and symptoms of the disease (e.g., rickets, growth retardation, musculoskeletal pain, bone fractures, etc.);

6. The individual has not received oral phosphate and/or active vitamin D analogs (e.g. calcitriol, doxercalciferol) within 1 week prior to the start of therapy;

7. The prescriber is a specialist or has consulted with a specialist in an area of the individual’s diagnosis (e.g., nephrologist, endocrinologist, rheumatologist, or oncologist);

8. The individual does not have any contraindication(s) to therapy with the requested agent; AND

9. The prescribed dosage is within the program quantity limits based on FDA approved labeled dosage.

Length of Approval: 6 months

Renewal Evaluation

Crysvita (burosumab-twza) may be approved for RENEWAL when ALL of the following criteria are met:

1. The individual has been previously approved for the requested agent through the BCBSMS review process;

2. The individual has documented clinical improvement (e.g., normalization of serum phosphorus levels, a reduction in serum total alkaline phosphatase activity, improvement in linear growth, improvement in skeletal deformities, reduction of fractures, reduction of generalized bone pain etc.) and/or improvement in radiographic imaging of rickets/osteomalacia;

3. The individual has not experienced unacceptable toxicity from the drug such as severe hypersensitivity reactions, hyperphosphatemia and/or nephrocalcinosis, severe injection site reactions, etc.;

4. The prescriber is a specialist or has consulted with a specialist in an area of the individual’s diagnosis (e.g., nephrologist, endocrinologist, rheumatologist, or oncologist);

5. The individual does not have any FDA-labeled contraindication(s) to therapy with the requested agent; AND

6. The prescribed dosage is within the program quantity limits based on FDA approved labeled dosage.

Length of Approval: 12 months 

Services related to delivery and/or administration of a medication determined to be not medically necessary will also be considered not medically necessary.

POLICY EXCEPTIONS

None

POLICY GUIDELINES

Medical Policy Manual coverage guidelines should not be used in lieu of the Participant's specific benefit plan language outlined in the Mississippi's State and School Employees’ Life and Health Insurance Plan.

Phosphorous Level Measurements:

Phosphorous levels should be obtained fasting 12 hours or more without food or drink except for water and after an adequate washout period after supplements; lab values (i.e. GFR, phosphorous, TmP/GFR) should be obtained within 28 days of the date of administration.

Pediatric Patients with X-linked Hypophosphatemia (1 to less than 18 years of age): After initiation of treatment, fasting serum phosphorus should be measured every four weeks for the first three months of treatment, and thereafter as appropriate.

Adult Patients with X-linked Hypophosphatemia (18 years of age and older): After initiation of treatment, assess fasting serum phosphorus on a monthly basis, measured two weeks post-dose, for the first three months of treatment, and thereafter as appropriate.

Pediatric Patients with Tumor-induced Osteomalacia (2 years to less than 18 years of age): After initiation of treatment, fasting serum phosphorous should be measured on a monthly basis, measured two weeks post-dose, for the first three months of treatment, and thereafter as appropriate.

Adult Patients with Tumor-induced Osteomalacia (18 years of age and older): After initiation of treatment, fasting serum phosphorous should be measured on a monthly basis, measured two weeks post-dose, for the first three months of treatment, and thereafter as appropriate.

Medically Necessary is defined as those services, treatments, procedures, equipment, drugs, devices, items or supplies furnished by a covered Provider that are required to identify or treat a Participant's illness, injury or Mental Health Disorders, and which Company determines are covered under this Benefit Plan based on the criteria as follows in A through D:

A. consistent with the symptoms or diagnosis and treatment of the Participant's condition, illness, or injury; and

B. appropriate with regard to standards of good medical practice; and

C. not solely for the convenience of the Participant, his or her Provider; and

D. the most appropriate supply or level of care which can safely be provided to the Participant. When applied to the care of an Inpatient, it further means that services for the Participant's medical symptoms or conditions require that the services cannot be safely provided to the Participant as an Outpatient.

For the definition of medical necessity, “standards of good medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. BCBSMS makes no payment for services, treatments, procedures, equipment, drugs, devices, items or supplies which are not documented to be Medically Necessary. The fact that a Physician or other Provider has prescribed, ordered, recommended, or approved a service or supply does not in itself, make it Medically Necessary.

Investigative is defined as the use of any treatment procedure, facility, equipment, drug, device, or supply not yet recognized as a generally accepted standard of good medical practice for the treatment of the condition being treated and; therefore, is not considered medically necessary. For the definition of Investigative, “generally accepted standards of medical practice” means standards that are based on credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community, and physician specialty society recommendations, and the views of medical practitioners practicing in relevant clinical areas and any other relevant factors. In order for equipment, devices, drugs or supplies [i.e, technologies], to be considered not investigative, the technology must have final approval from the appropriate governmental bodies, and scientific evidence must permit conclusions concerning the effect of the technology on health outcomes, and the technology must improve the net health outcome, and the technology must be as beneficial as any established alternative and the improvement must be attainable outside the testing/investigational setting.

POLICY HISTORY

07/01/2023: New policy added.

06/03/2025: Policy reviewed and approved by the Pharmacy & Therapeutics (P&T) Committee. Policy description updated regarding indications for Crysvita (burosumab-twza). Policy statement revised to state that the use of samples by an individual will not be considered current or stable therapy to satisfy Medical Policy requirements. Revised criteria for X-linked Hypophosphatemia and tumor-induced osteomalacia. Removed prescriber statement regarding serum phosphorus. Revised statement criteria regarding contraindications to therapy and dose requirements. Renewal criteria updated regarding clinical improvement, contraindications to therapy, and dose requirements. Policy Guidelines updated to remove information regarding dosing and administration (subcutaneously only). Sources updated.

SOURCE(S)

Crysvita prescribing information. Kyowa Kirin, Inc. November 2024. Last accessed March 2025.

CODE REFERENCE

This may not be a comprehensive list of procedure codes applicable to this policy.

The code(s) listed below are ONLY medically necessary if the procedure is performed according to the "Policy" section of this document.

Medically Necessary Codes

CPT copyright American Medical Association. All rights reserved. CPT is a registered trademark of the American Medical Association.