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Strensiq Prior Authorization Program Summary
Policy Number: PH-1073
This program applies to Blue Partner, Commercial, GenPlus, NetResults A series, SourceRx, and Health Insurance Marketplace formularies.
POLICY REVIEW CYCLE
Effective Date |
Date of Origin |
1/1/2024 |
|
FDA APPROVED INDICATIONS AND DOSAGE
Agent(s) |
FDA Indication(s) |
Notes |
Ref# |
Strensiq® (asfotase alfa) Injection |
Treatment of patients with perinatal/infantile-onset and juvenile-onset hypophosphatasia (HPP) |
|
1 |
See package insert for FDA prescribing information: https://dailymed.nlm.nih.gov/dailymed/index.cfm
CLINICAL RATIONALE
Hypophosphatasia |
Hypophosphatasia (HPP) is a rare genetic disease caused by mutations in the tissue non-specific alkaline phosphatase (TNSALP) gene, which reduce its activity. This causes disruption of mineralization, a process in which calcium and phosphorous are deposited in developing bones and teeth.(5) TNSALP controls skeletal and dental mineralization by hydrolyzing inorganic pyrophosphate, an inhibitor of hydroxyapatite crystal growth. Insufficient activity can lead to chest wall instability and respiratory complications in perinatal and infantile forms. Natural substrates of TNSALP that accumulate in hypophosphatasia include inorganic pyrophosphate (PPi), phosphoethanolamine (PEA), and pyridoxal 5’-phosphate (PLP), the principal circulating form of vitamin B6.(4)
Perinatal HPP features extreme skeletal disease obvious at birth; survival beyond birth is rare. Infantile HPP develops prior to 6 months of age and has an estimated 50% mortality during infancy typically due to respiratory complications. Patients with infantile HPP develop rickets, failure to thrive, hypotonia, myopathy, and the condition is often complicated by hypercalcemia, nephrocalcinosis, craniosynostosis, and vitamin B6-dependent seizures. Although spontaneous improvement sometimes occurs in infantile hypophosphatasia, substantial bone disease and weakness often persist. Skeletal deterioration typically results in death from respiratory insufficiency. In both forms, hypomineralization leads to thoracic instability, fractures, and deformities, and sometimes even pulmonary hypoplasia in perinatal HPP.(3)
Juvenile HPP tends to be less severe than those that appear in infancy. Affected children may have short stature, bowed legs, enlarged wrist and ankle joints (metaphyseal flares that appear as “swollen joints”), muscle weakness, and abnormal skull shape.(3)
Although the disease spectrum is a continuum, six clinical forms are usually recognized based on age at diagnosis and severity of features:(3)
A diagnosis of HPP is based upon identification of characteristic signs and symptoms, a detailed patient history, a thorough clinical evaluation, and a variety of laboratory tests including routine x-ray and biochemical studies. Proper diagnosis of HPP is easy for physicians who are familiar or experienced with this disorder. However, most physicians have little or no knowledge of HPP. Consequently, affected individuals and families may face a frustrating delay in diagnosis. Molecular genetic testing can support a diagnosis of HPP. Molecular genetic testing can detect mutations in the ALPL gene known to cause the disorder, but it is only available as a diagnostic service at specialized laboratories.(4) The range of serum alkaline phosphatase (ALP) activity varies by age and healthy children normally have higher ALP levels than healthy adults. Individuals with HPP have reduced serum ALP activity for their age, except for the extremely rare individual with pseudohypophosphatasia who has normal activity levels. Identification of deficient alkaline phosphatase activity is consistent with HPP, but not conclusive since other conditions can result in this finding. Additionally, some individuals who are genetic carriers of HPP, but who do not develop any symptoms of the disorder, may also have low blood ALP levels.(4) A suspected diagnosis of HPP can be further supported by measuring the serum level of vitamin B6. Individuals with HPP have elevated levels of pyridoxal 5’-phosphate (PLP: the active form of vitamin B6) in the blood because PLP is normally broken down by TNSALP. PLP is elevated even in individuals with mild HPP. However, some genetic carriers of HPP who do not develop any symptoms can have an elevated PLP level as well. In the past, blood or urine was tested for increased amounts of phosphoethanolamine (PEA), another chemical normally broken down by TNSALP. However, elevated PEA is not specific to HPP and can be associated with other metabolic bone diseases. Additionally, some individuals with HPP have normal PEA levels. Screening for elevated PLP is preferred over screening for PEA because it is more sensitive, more precise, and less expensive. In the most severe cases of HPP, specifically the perinatal and infantile forms, x-ray studies can reveal diagnostic changes within the bones. However, these changes may not be recognized as being associated with HPP, except by radiologists familiar with the disorder.(4,6) Periodic assessments should be performed to monitor the safety and effectiveness of Strensiq. Assessment includes the monitoring of symptoms, growth, radiographs, and laboratory tests, e.g., PEA, PLP, or PPi. Other than asfotase alpha, the primary way to manage HPP is through supportive care.(4,6) |
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Efficacy (1) |
Strensiq is the first approved therapy for perinatal, infantile and juvenile-onset HPP. Strensiq is a formulation of asfotase alfa, which is a soluble glycoprotein composed of two identical polypeptide chains. Strensiq is a tissue nonspecific alkaline phosphatase produced by recombinant DNA technology in a Chinese hamster ovary cell line. |
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Safety (1) |
The 80 mg/0.8 mL vial of Strensiq should not be used in pediatric patients weighing less than 40 kg because the systemic exposure of asfotase alfa achieved with the 80 mg/0.8 mL (higher concentration) is lower than that achieved with the other strength vials (lower concentration). A lower exposure may not be adequate for this subgroup of patients. Patients with HPP are at increased risk for developing ectopic calcifications. Events of ectopic calcification, including ophthalmic and renal, have been reported in clinical trials experience with Strensiq. Although there was insufficient information to determine whether or not the reported events were consistent with the disease or due to Strensiq, ophthalmology examinations and renal ultrasounds are recommended at baseline and periodically during treatment to monitor for signs and symptoms of ectopic calcifications and for changes in vision or renal function. |
REFERENCES
Number |
Reference |
1 |
Strensiq prescribing information. Alexion. March 2023. |
2 |
|
3 |
Mornet, E. Hypophosphatasia. Orphanet J Rare Dis. 2007;2:40 |
4 |
National Organization for Rare Disorders (NORD). Hypophosphatasia. https://rarediseases.org/rare-diseases/hypophosphatasia/ |
5 |
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 |
6 |
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. |
POLICY AGENT SUMMARY PRIOR AUTHORIZATION
Target Brand Agent(s) |
Target Generic Agent(s) |
Strength |
Targeted MSC |
Available MSC |
Final Age Limit |
Preferred Status |
|
||||||
Strensiq |
asfotase alfa subcutaneous inj |
18 MG/0.45ML ; 28 MG/0.7ML ; 40 MG/ML ; 80 MG/0.8ML |
M ; N ; O ; Y |
N |
|
|
CLIENT SUMMARY – PRIOR AUTHORIZATION
Target Brand Agent Name(s) |
Target Generic Agent Name(s) |
Strength |
Client Formulary |
Strensiq |
asfotase alfa subcutaneous inj |
18 MG/0.45ML ; 28 MG/0.7ML ; 40 MG/ML ; 80 MG/0.8ML |
Blue Partner ; Commercial ; GenPlus ; Health Insurance Marketplace ; NetResults A Series ; SourceRx |
PRIOR AUTHORIZATION CLINICAL CRITERIA FOR APPROVAL
Module |
Clinical Criteria for Approval |
|
Initial Evaluation Target Agent(s) will be approved when ALL of the following are met:
Length of Approval: 6 months
Renewal Evaluation Target Agent(s) will be approved when ALL the following are met:
Length of Approval: 12 months |
This pharmacy policy is not an authorization, certification, explanation of benefits or a contract. Eligibility and benefits are determined on a case-by-case basis according to the terms of the member’s plan in effect as of the date services are rendered. All pharmacy policies are based on (i) information in FDA approved package inserts (and black box warning, alerts, or other information disseminated by the FDA as applicable); (ii) research of current medical and pharmacy literature; and/or (iii) review of common medical practices in the treatment and diagnosis of disease as of the date hereof. Physicians and other providers are solely responsible for all aspects of medical care and treatment, including the type, quality, and levels of care and treatment.
The purpose of Blue Cross and Blue Shield of Alabama’s pharmacy policies are to provide a guide to coverage. Pharmacy policies are not intended to dictate to physicians how to practice medicine. Physicians should exercise their medical judgment in providing the care they feel is most appropriate for their patients.
Neither this policy, nor the successful adjudication of a pharmacy claim, is guarantee of payment.
Commercial _ PS _ Strensiq _PA _ProgSum_ 1/1/2024