CurrentAnthemPolicy CC-0079

Strensiq (asfotase alfa) — Clinical Criteria for Coverage

Clinical criteria governing medical benefit coverage and prior authorization for Strensiq (asfotase alfa) to treat perinatal/infantile and juvenile-onset hypophosphatasia (HPP) for Anthem members.

Policy Summary

PayerAnthem

PolicyStrensiq (asfotase alfa) — Clinical Criteria for Coverage

Policy CodePolicy CC-0079

Change TypeContinuation criteria revisedHCPCS added

Effective Date01/30/2026

Next Review Date

Key ActionSubmit prior authorization with diagnostic labs, radiographic/genetic or listed clinical findings; document clinically significant improvement for continuation.

SourceLink

POLICY UPDATE CHANGES

Updated continuation criteria to confirm diagnosis; added HCPCS NOC C9399 for Strensiq.

Status revised (document header shows 'Revised').

perinatal/infantile & juvenile-onsetIndicated HPP populations

anaphylaxisBoxed warning

C9399, J3490HCPCS/Unclassified codes

50-100%Reported infant/child mortality

Coverage Criteria for Strensiq (asfotase alfa)

Initial Therapy

Covered when ALL of the following are met for initial requests:

Initial request: 1) Diagnosis of perinatal/infantile hypophosphatasia (HPP) with symptom onset prior to 6 months OR juvenile-onset HPP with onset ≤ 18 years; 2) Total serum alkaline phosphatase below the lower limit of normal for the individual's age and gender at diagnosis; 3) Plasma pyridoxal 5'-phosphate level greater than the upper limit of normal at the time of diagnosis; 4) One of the following: A) Radiographic evidence of poor bone mineralization (eg, flared and frayed metaphyses, severe/generalized osteopenia, widened growth plates) OR B) Genetic test results confirming infantile HPP OR C) One of the listed clinical findings: nontraumatic postnatal fracture healing; history of elevated serum calcium; functional craniosynostosis with decreased head circumference growth; nephrocalcinosis; rachitic chest deformity; respiratory compromise; vitamin B6–responsive seizures; or failure to thrive.

Exact list of clinical findings must be documented.

Continuation Therapy

Covered when ALL of the following are met for continuation requests:

Continuation request:

Policy Summary

PayerAnthem

PolicyStrensiq (asfotase alfa) — Clinical Criteria for Coverage

Policy CodePolicy CC-0079

Change TypeContinuation criteria revisedHCPCS added

Effective Date01/30/2026

Next Review Date

Key ActionSubmit prior authorization with diagnostic labs, radiographic/genetic or listed clinical findings; document clinically significant improvement for continuation.

SourceLink

On This Page

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Codes and Diagnosis

HCPCSHCPCS

C9399	Unclassified drugs or biologicals [when specified as Strensiq (asfotase alfa)]
J3490	Unclassified drugs [when specified as Strensiq (asfotase alfa)]

ICD-10 DiagnosisICD-10

E83.31	Familial hypophosphatemia
E83.39	Other disorders of phosphorus metabolism

inv-07: Age of onset for perinatal/infantile HPP — onset prior to 6 months of age

Perinatal/infantile onset thresholdOnset of HPP symptoms prior to 6 months of age.

Usage contextRequired to qualify as perinatal/infantile hypophosphatasia for Strensiq coverage.

Supporting diagnostic requirementMust be paired with documented low total serum alkaline phosphatase and elevated plasma pyridoxal 5'-phosphate at diagnosis.

inv-08: Age of onset for juvenile-onset HPP — onset ≤ 18 years of age

Juvenile-onset thresholdOnset of HPP at or before 18 years of age (≤18 years).

Usage contextRequired to qualify as juvenile-onset HPP for Strensiq coverage (alternative to perinatal/infantile criteria).

Continuation linkageDiagnosis with onset ≤18 years must be documented for both initial and continuation requests.

Provider Actions and Authorization Requirements

Prior Authorization

Prior Authorization Required

Prior authorization is required for initial and continuation requests for Strensiq (asfotase alfa). Initial requests will be approved only when diagnostic and laboratory criteria plus radiographic, genetic, or specified clinical findings are documented. Continuation requests require documentation of ongoing clinical benefit or stabilization.

Prior authorization required for initial and continuation therapy
Initial approval requires diagnostic, laboratory, and radiographic/genetic/clinical evidence
Continuation approval requires clinically significant improvement or stabilization on therapy

Documentation Required

Required Documentation

Provide documentation of the diagnosis and supporting objective evidence at the time of the initial request or continuation request. Required documentation includes laboratory results, radiographic or genetic evidence, and relevant clinical history.

Diagnosis consistent with perinatal/infantile HPP (onset < 6 months) or juvenile-onset HPP (onset ≤ 18 years)
Total serum alkaline phosphatase below the age- and sex-specific lower limit of normal at diagnosis
Plasma pyridoxal 5'-phosphate (PLP) above the upper limit of normal at diagnosis
Radiographic evidence of poor bone mineralization OR confirmatory genetic test OR one or more specified clinical findings (e.g., nontraumatic fractures, nephrocalcinosis, respiratory compromise, failure to thrive, vitamin B6–responsive seizures, rachitic chest deformity, craniosynostosis, history of elevated serum calcium)

Denial Risk

Requests May Be Denied

Requests may be denied when the specified initial or continuation criteria are not met or when documentation is incomplete. Strensiq will also not be approved for indications other than those listed in the criteria.

Denial risk if diagnosis does not meet perinatal/infantile or juvenile-onset HPP definitions
Denial risk if required laboratory (alkaline phosphatase, PLP) or radiographic/genetic evidence is absent or does not meet thresholds
Denial risk for lack of documented clinical improvement or stabilization on therapy for continuation requests
Not approved for all other indications outside the specified criteria

Definitions and Key Terms

inv-14: Hypophosphatasia (HPP) — definition summarizing ALPL gene mutation and alkaline phosphatase deficiency

Underlying causeHPP is caused by mutations of the alkaline phosphatase (ALPL) gene resulting in deficient alkaline phosphatase activity and low enzyme levels in serum and bone.

PathophysiologyDeficient alkaline phosphatase impairs mineralization, disrupting deposition of calcium and phosphorus into developing bone and teeth.

Clinical spectrumPresents variably from perinatal/infantile to juvenile-onset disease with signs including hypomineralization, rickets, fractures, dental abnormalities, and respiratory compromise.

inv-15: Responder (per trials) — Patients achieving RGI-C score ≥2 indicating substantial healing

Responder definitionPatients achieving a Radiographic Global Impression of Change (RGI-C) score ≥2, corresponding to substantial healing of rickets.

Trial contextRGI-C ≥2 was used in clinical studies to classify responders to asfotase alfa treatment.

Clinical relevanceResponder status indicates radiographic improvements used to assess treatment benefit in juvenile and perinatal/infantile HPP trials.

OpenPayer

Strensiq (asfotase alfa) — Clinical Criteria for Coverage

Coverage Criteria for Strensiq (asfotase alfa)

Codes and Diagnosis

Provider Actions and Authorization Requirements

Background

Definitions and Key Terms