Clinical Policy: Asfotase Alfa (Strensiq)
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Policy governs medical necessity and prior authorization criteria for asfotase alfa (Strensiq) for perinatal/infantile- and juvenile-onset hypophosphatasia across commercial, HIM and Medicaid lines of business.
No material clinical or coverage changes in this revision.
Coverage Criteria
Initial Therapy
Initial therapy covered when ALL of the following are met:
Dose may be administered as 3 mg/kg SC three times per week or equivalent as specified in dosing guidance.
Continuation Therapy
Continuation therapy covered when:
If request is for a dose increase, the new dose must not exceed 9 mg/kg/week for perinatal/infantile-onset or 6 mg/kg/week for juvenile-onset.
Requests for indications that are not FDA-approved and are not specifically addressed in this policy are excluded unless the provider supplies adequate documentation of efficacy and safety in accordance with the applicable off‑label use policies (for example, CP.CPA.09 for commercial, HIM.PA.154 for health insurance marketplace, or CP.PMN.53 for Medicaid) or other evidence of coverage documents.
When there is a conflict between this clinical policy and state Medicaid coverage provisions, the state Medicaid requirements take precedence. Providers must follow applicable state and federal requirements and the member’s evidence of coverage or other plan documents when those documents differ from this policy.
Off‑label use requests for indications not FDA‑approved and not addressed in this policy may be denied if the submission does not include sufficient documentation of efficacy and safety per the payer’s off‑label use policies. Providers should follow the referenced off‑label policies and supply supporting clinical evidence to avoid denial.
Initial Therapy
Initial Therapy
Initial approval criteria and dosing limits
Perinatal/infantile-onset dosing may be administered as up to 3 mg/kg SC three times per week (up to 9 mg/kg/week); juvenile-onset dosing may be administered as 2 mg/kg SC three times per week (6 mg/kg/week) or equivalent regimens noted in dosing guidance.
Continuation / Renewal Criteria
Continuation Therapy
Requirements for renewal/continuation
Coding and Dosing
Provider Actions and Requirements
Prior Authorization Required
Prior authorization is required. Provider must submit documentation (such as office chart notes, laboratory results, genetic testing reports, and other clinical information) supporting the diagnosis and that the member meets all approval criteria. Requests should include prescribing provider specialty and rationale for therapy.
- Include molecular genetic testing results (e.g., ALPL gene) when applicable
- Include baseline laboratory indices (e.g., low serum alkaline phosphatase, elevated substrates such as pyridoxal 5'-phosphate or urinary inorganic pyrophosphate)
- Provide clinical manifestations supporting the diagnosis (seizures, nephrocalcinosis, failure to thrive, skeletal abnormalities, dental findings, etc.)
Provider Guidance
Providers should follow this clinical policy as guidance for coverage determinations but must exercise their professional medical judgment. The clinical policy does not replace provider decision-making; supporting documentation must be submitted to demonstrate medical necessity.
- Clinical policy is a guideline — individualized treatment decisions remain the responsibility of the treating provider
- Submit documentation consistent with medical necessity to support approval requests
Formulary / Off‑Label Routing
For requests for uses that are off‑label or for drugs not on the formulary/PDL, follow the applicable Health Net non‑formulary or off‑label use policies for the member's line of business. Requests for non‑FDA approved indications may be denied without sufficient off‑label documentation per the referenced policies.
- For formulary drugs: refer to no coverage criteria policies — Commercial: CP.CPA.190; Health Insurance Marketplace: HIM.PA.33; Medicaid: CP.PMN.255
- For non‑formulary drugs: refer to non‑formulary policies — Commercial: CP.CPA.190; Health Insurance Marketplace: HIM.PA.103; Medicaid: CP.PMN.16
- For off‑label use documentation requirements: Commercial: CP.CPA.09; Health Insurance Marketplace: HIM.PA.154; Medicaid: CP.PMN.53
Coding Inclusion/Exclusion Disclaimer
Codes referenced in this clinical policy are for informational purposes only. Inclusion or exclusion of any codes does not guarantee coverage. Providers should reference the most up‑to‑date professional coding guidance when submitting claims for reimbursement.
- Inclusion or exclusion of codes does not guarantee coverage
- Verify coding with current coding manuals and payer billing guidance prior to claim submission
Non‑Approved Indications
Requests for indications not FDA‑approved and not addressed in this policy require adequate off‑label documentation of efficacy and safety per the applicable off‑label use policy; lacking sufficient documentation, such requests may be denied.
- Non‑approved indications may be denied without sufficient off‑label documentation (see CP.CPA.09 / HIM.PA.154 / CP.PMN.53)
Required Clinical Documentation
Provider must submit chart notes, lab results, genetic testing, and other clinical information to support that the member meets the stated criteria for approval.
- Office/chart notes documenting clinical manifestations and functional status
- Relevant laboratory data and genetic testing reports
- Treatment history and prescribing provider specialty/consultation notes
Site of Care
Site of care — no explicit restriction stated
No explicit site‑of‑care restriction is stated in this portion of the policy.
Formulary / Step Therapy Routing
| Scenario | Required routing / referenced policies |
|---|---|
| Drug is on the formulary (commercial or health insurance marketplace) or on the PDL (Medicaid) | Follow the no‑coverage / formulary criteria policy for the relevant line of business: CP.CPA.190 (commercial), HIM.PA.33 (health insurance marketplace), or CP.PMN.255 (Medicaid). If the drug recently had a label change not reflected in this policy, follow the referenced policy guidance as applicable. |
| Drug is NOT on the formulary (commercial or health insurance marketplace) or NOT on the PDL (Medicaid) | Follow the non‑formulary policy for the relevant line of business: CP.CPA.190 (commercial), HIM.PA.103 (health insurance marketplace), or CP.PMN.16 (Medicaid). |
| Requested use (diagnosis, age, or dosing regimen) is not listed in this policy and criterion above does not apply | Refer to the off‑label use policy for the relevant line of business: CP.CPA.09 (commercial), HIM.PA.154 (health insurance marketplace), or CP.PMN.53 (Medicaid). |
Background
Hypophosphatasia (HPP) is a rare metabolic bone disease caused by loss‑of‑function mutations in the ALPL gene resulting in deficient tissue nonspecific alkaline phosphatase activity and accumulation of its substrates. The resulting biochemical abnormalities (for example, low serum alkaline phosphatase with elevated substrates such as pyridoxal 5'-phosphate and inorganic pyrophosphate) produce clinical manifestations including impaired bone mineralization, fractures, growth failure, respiratory compromise in severe forms, tooth loss, and neurologic features such as vitamin B6‑dependent seizures. Asfotase alfa (Strensiq) is a targeted enzyme replacement therapy — a tissue nonspecific alkaline phosphatase — approved to treat perinatal/infantile‑ and juvenile‑onset HPP to improve bone mineralization and related clinical outcomes.
Definitions and Purpose
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