CurrentColorado Rocky Mountain Health PlansPolicy N/A

Strensiq (asfotase alfa) prior authorization and medical necessity criteria

Defines prior authorization, initial approval, and reauthorization criteria for Strensiq (asfotase alfa) to treat perinatal/infantile and juvenile-onset hypophosphatasia for members of Colorado Rocky Mountain Health Plans (UnitedHealthcare Pharmacy Clinical Pharmacy Programs).

Policy Summary

PayerColorado Rocky Mountain Health Plans

PolicyStrensiq (asfotase alfa) prior authorization and medical necessity criteria

Policy CodePolicy N/A

Change TypeRevised initial and reauthorization criteria

Effective DateDec 1, 2025

Next Review DateN/A

Key ActionObtain prior authorization; initial approvals are issued for 6 months when all initial therapy criteria are met.

SourceLink

POLICY UPDATE CHANGES

Updated initial and reauthorization criteria and references.

6 monthsInitial authorization duration

12 monthsReauthorization duration

9 mg/kg/wkMax dose (perinatal/infantile)

6 mg/kg/wkMax dose (juvenile)

>=40 kg

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Coverage and Medical Necessity Criteria

Initial Therapy

Covered when ALL of the following are met

Initial Approval

Diagnosis: Submission of medical records documenting diagnosis of perinatal/infantile or juvenile-onset hypophosphatasia
Confirmation of diagnosis: Medical records document confirmation by: (1) presence of clinical signs and symptoms of hypophosphatasia (e.g., skeletal abnormalities, respiratory insufficiency, failure to thrive, hypotonia, dental abnormalities, short stature, rickets, fractures, delayed walking, waddling gait); (2) onset of disease < 18 years of age (if member ≥ 18 at time of request, documentation that onset occurred < 18); and (3) either (a) all of the following: i) persistent serum alkaline phosphatase (ALP) levels below the gender- and age-specific reference range on at least two measurements; ii) elevated tissue non-specific alkaline phosphatase (TNSALP) substrate level (e.g., serum PLP, serum or urine PEA, urinary inorganic PPi); and iii) radiographic imaging demonstrating skeletal abnormalities (e.g., craniosynostosis, rickets, non-traumatic fractures) OR (b) presence of a known pathogenic ALPL gene mutation detected by molecular genetic testing
Prescriber specialty: Prescribed by one of the following: (1) Endocrinologist OR (2) A specialist experienced in the treatment of metabolic bone disorders
Diagnosis-specific dose limits: Either: (A) Diagnosis of perinatal/infantile-onset HPP AND request does not exceed a maximum supply limit of 9 mg/kg/week OR (B) Diagnosis of juvenile-onset HPP AND request does not exceed a maximum supply limit of 6 mg/kg/week
Formulation restrictions: Either: (1) Patient is prescribed Strensiq 18 mg/0.45 mL, 28 mg/0.7 mL, or 40 mg/mL vials OR (2) Patient is prescribed Strensiq 80 mg/0.8 mL vial AND patient weight is greater than or equal to 40 kg

Reauthorization

Reauthorization covered when ALL of the following are met

Clinical response: Documentation of positive clinical response to Strensiq therapy (e.g., improvement in clinical symptoms, improvement in Radiographic Global Impression of Change)
Prescriber specialty: Prescribed by one of the following: (1) Endocrinologist OR (2) A specialist experienced in the treatment of metabolic bone diseases
Diagnosis-specific dose limits: Either: (A) Diagnosis of perinatal/infantile-onset HPP AND request does not exceed a maximum supply limit of 9 mg/kg/week OR (B) Diagnosis of juvenile-onset HPP AND request does not exceed a maximum supply limit of 6 mg/kg/week
Formulation restrictions: Either: (1) Patient is prescribed Strensiq 18 mg/0.45 mL, 28 mg/0.7 mL, or 40 mg/mL vials OR (2) Patient is prescribed Strensiq 80 mg/0.8 mL vial AND patient weight is greater than or equal to 40 kg

Coverage is subject to applicable state mandates, federal regulatory requirements, and the member’s specific benefit plan; these authorities may modify, limit, or supersede the coverage described here. Other UnitedHealthcare policies and utilization management programs (for example, program-specific supply limits or prior authorization rules) may also apply and could affect approval or fulfillment of requests. Automated approval or denial processes that rely on prior claim/medication history, diagnosis codes, and claim logic may be used by the program and can impact decisions independently of the criteria listed below.

Dosing, Administration and Coding Constraints

Maximum dosing/administration thresholds

Perinatal/infantile-onset maximum doseRequests must not exceed 9 mg/kg/week

Juvenile-onset maximum doseRequests must not exceed 6 mg/kg/week

80 mg vial weight requirementUse of the 80 mg/0.8 mL vial is allowed only if patient weight is ≥ 40 kg

Authorization, Documentation and Operational Guidance

Prior Authorization

Prior Authorization Required

Prior authorization required — initial approvals issued for 6 months when initial therapy criteria are met.

Authorization duration: 6 months
Prior authorization required before initiation of Strensiq (as per Initial Therapy criteria)

Note

Automated Processes May Apply

Automated approval/denial processes may be used. Approvals or denials can be determined based on previous claims or medication history, submitted diagnosis codes (ICD-10), and program logic; use of these automated processes varies by program or therapeutic class.

Approvals/denials may be based on prior claim history and diagnosis codes
Program-specific automated logic may apply

Clinical Background

Strensiq (asfotase alfa) is a recombinant tissue-nonspecific alkaline phosphatase indicated for treatment of perinatal/infantile- and juvenile-onset hypophosphatasia (HPP). HPP is a metabolic bone disease characterized by low serum alkaline phosphatase and accumulation of TNSALP substrates (for example, pyridoxal 5′-phosphate, phosphoethanolamine, and inorganic pyrophosphate), and it manifests with skeletal abnormalities and symptoms such as rickets, fractures, respiratory insufficiency, dental abnormalities, hypotonia, and delayed walking. Therapy with Strensiq is intended to replace deficient alkaline phosphatase activity and improve bone mineralization and clinical signs in affected infants and children.

Key Definitions

Hypophosphatasia (HPP) — key clinical and laboratory features

DefinitionHypophosphatasia (HPP) is a metabolic bone disease characterized by low serum alkaline phosphatase and abnormalities of tissue-nonspecific alkaline phosphatase (TNSALP)

Typical biochemical featuresPersistent low serum ALP on ≥2 measurements and elevated TNSALP substrates (e.g., PLP, PEA, urinary PPi)

Clinical and skeletal manifestationsSigns/symptoms include skeletal abnormalities (rickets, non‑traumatic fractures, craniosynostosis), respiratory insufficiency, failure to thrive, hypotonia, dental abnormalities, short stature, delayed walking or waddling gait

Genetic confirmationAlternatively, presence of a known pathogenic ALPL gene mutation detected by molecular genetic testing can confirm diagnosis