Strensiq (asfotase alfa)

POLICY NUMBER

L.5.01.517

Strensiq (asfotase alfa)

Please perform a formulary drug search on your patient’s member ID to ensure the prescription drug is covered under their benefit plan. The medication(s) in this medical policy may not be covered under a specific member’s benefit plan.

DESCRIPTION

Strensiq (asfotase alfa) is a tissue nonspecific alkaline phosphatase approved for the treatment of patients with perinatal/infantile- and juvenile-onset hypophosphatasia (HPP).

Hypophosphatasia (HPP) is caused by a deficiency in tissue-nonspecific alkaline phosphatase (TNSALP) enzyme activity, which leads to elevations in many TNSALP substrates, including inorganic pyrophosphate (PPi). Elevated levels of PPi block hydroxyapatite crystal growth, which in turn inhibits bone mineralization and causes an accumulation of unmineralized bone matrix. The unmineralized bone matrix manifests as rickets and bone deformation in infants and children. It can then manifest as osteomalacia once growth plates close, along with muscle weakness. Replacement of the TNSALP enzyme upon Strensiq treatment reduces the enzyme substrate levels.

Hallmark manifestations of HPP include skeletal and/or dental issues. Skeletal manifestations include: rickets, osteomalacia, non-healing fractures, osteopenia, osteoporosis, and craniosynostosis. Dental manifestations include: premature tooth loss or periodontal disease. These manifestations combined with a low age adjusted alkaline phosphatase steer in the direction of a HPP diagnosis.

POLICY

Prior authorization is required.

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

Initial Review

Strensiq (asfotase alfa) may be considered medically necessary for individuals who meet ALL of the following criteria:

1. The individual has a documented diagnosis of either perinatal/infantile- OR juvenile onset hypophosphatasia (HPP) evidenced by ALL of the following:

   1. The individual was ≤18 years of age at onset;

   2. The individual is experiencing active disease (e.g. bone pain, fractures, gait problems);

   3. The individual has/had clinical manifestations consistent with hypophosphatasia at the age of onset prior to age 18 (e.g. vitamin B6-dependent seizures, fractures, lost teeth with roots, skeletal abnormalities, such as rachitic chest deformity leading to respiratory problems or bowed arms/legs, “failure to thrive”);

   4. Molecular genetic testing has been completed confirming mutations in the ALPL gene that encodes the tissue nonspecific isoenzyme of ALP (TNSALP);

   5. The individual has/had radiographic imaging confirming the diagnosis of hypophosphatasia at the age of onset prior to age 18 (e.g., infantile rickets, alveolar bone loss, craniosynostosis)

   6. The individual has reduced activity of unfractionated serum alkaline phosphatase (ALP) in the absence of bisphosphonate therapy (i.e., below the normal lab reference range for age and sex); AND

   7. ONE of the following

      1. Elevated serum concentration of pyridoxal 5'-phosphate (PLP) in the absence of vitamin supplements within one week prior to the test;

      2. Elevated urine concentration of phosphoethanolamine (PEA); OR

      3. Elevated urinary inorganic pyrophosphate (PPi);

2. The prescriber is a specialist in the area of the individual's diagnosis or has consulted with a specialist in the area of the individual's diagnosis (e.g. endocrinologist, geneticist);

3. The individual has had an ophthalmology examination and renal ultrasound at baseline (prior to starting therapy with the requested agent);

4. The individual does NOT have any FDA labeled contraindications to the requested agent;

   AND

5. The requested quantity is within FDA labeled weight-based dosing for the requested indication based on the individual’s current weight.

Length of Approval: 6 months

Renewal Criteria

Strensiq (asfotase alfa) 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 PA process;

2. The prescriber is a specialist or has consulted with a specialist in the area of the individual's disease/diagnosis (e.g., endocrinologist, geneticist);

3. The individual has had documented clinical improvement from baseline (prior to starting therapy with the requested agent) in at least ONE of the following:

   1. Respiratory status (e.g., level of respiratory support is required);

   2. Growth (e.g., an improvement in length/height, weight, or head circumference as measured by z-scores);

   3. Radiographic findings (e.g., improvement in skeletal manifestations as measured by RSS or RGI-C or a decrease in fractures); OR

   4. Level of activity (e.g., improvement in motor function or activities in daily living);

4. The individual has been monitored for signs and symptoms of ophthalmic and renal calcifications and for changes in vision or renal function;

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

6. The requested quantity is within FDA labeled dosing for the requested indication based on the individual’s weight.

Length of Approval: 12 months

POLICY EXCEPTIONS

State Health Plan (State and School Employees): The prescription drug(s) in this medical policy may be covered under a prescription drug benefit plan administered by the State Health Plan’s Pharmacy Benefit Manager. Please perform a formulary drug search at https://www.dfa.ms.gov/cvs-caremark and submit any required Prior Authorization Requests for coverage determination to the Plan’s Pharmacy Benefit Manager. Services related to delivery and/or administration of a medication determined to be not medically necessary will also be considered not medically necessary. Services related to delivery and/or administration of a self-administered drug are not covered.

POLICY GUIDELINES

The coverage guidelines outlined in the Medical Policy Manual should not be used in lieu of the Member's specific benefit plan language.

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 Member'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 Member'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 Member, his or her Provider; and

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

For the definition of Medically Necessary, “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.

POLICY HISTORY

02/01/2018: New policy added.

03/27/2018: Policy reviewed and approved by Pharmacy & Therapeutics (P&T) Committee.

03/26/2019: Policy reviewed and approved by Pharmacy & Therapeutics (P&T) Committee. Initial and renewal criteria updated to change "FDA labeled dosing" to "FDA labeled weight-based dosing." Sources updated.

11/01/2020: Policy reviewed and approved by Pharmacy & Therapeutics (P&T) Committee. Added drug name to the top of the policy. Policy section updated to add the following statements: 1) Prior authorization is required. 2) The use of samples by a Member will not be considered current or stable therapy for purposes of Medical Policy review. Policy Guidelines updated to change "Nervous/Mental Conditions" to "Mental Health Disorders." Sources updated. Code Reference section updated to add HCPCS codes C9399 and J3590.

02/01/2023: Policy Exceptions updated to add the following: State Health Plan (State and School Employees): The prescription drug(s) in this medical policy may be covered under a prescription drug benefit plan administered by the State Health Plan’s Pharmacy Benefit Manager. Please perform a formulary drug search at https://www.dfa.ms.gov/cvs-caremark and submit any required Prior Authorization Requests for coverage determination to the Plan’s Pharmacy Benefit Manager. Services related to delivery and/or administration of a medication determined to be not medically necessary will also be considered not medically necessary. Services related to delivery and/or administration of a self-administered drug are not covered.

03/31/2025: Effective 06/01/2025 - Policy reviewed and approved by the Pharmacy & Therapeutics (P&T) Committee. 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. Medically necessary criteria revised regarding active disease, clinical manifestations consistent with hypophosphatasia, requirement of ophthalmology examination and renal ultrasound, and FDA labeled weight-based dosing. Removed statement that Approved members must be followed by Blue Cross & Blue Shield of Mississippi Case Management and subject to provisions of the member’s Benefit Plan. Added statement that Strensiq (asfotase alfa) may be approved for RENEWAL when ALL of the criteria are met. Added renewal criteria regarding documented clinical improvement, symptoms of ophthalmic and renal calcifications, and FDA labeled dosing. Sources updated. Policy update effective 06/01/2025.

SOURCE(S)

1. Kishani PS, Rush ET, Arundel P, et al. Monitoring guidance for patients with hypophosphatasia treated with asfotase alfa. Molecular Genetics and Metabolism 112 (2017) 4-17.

2. Mornet, E. Hypophosphatasia. Orphanet J Rare Dis. 2007;2:40

3. National Institute for Health and Care Excellence (NICE). Asfotase alfa for treating paediatric-onset hypophosphatasia. Published date: 01 March 2023. https://www.nice.org.uk/guidance/hst23.

4. National Organization for Rare Disorders (NORD). Hypophosphatasia. https://rarediseases.org/rarediseases/hypophosphatasia/

5. Strensiq prescribing information. Alexion Pharmaceuticals, Inc. July 2024. Last accessed January 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.