Medically reviewed by Drugs.com. Last updated on Oct 11, 2020.
(AZ fo tase AL fa)
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Solution, Subcutaneous [preservative free]:
Strensiq: 18 mg/0.45 mL (0.45 mL); 28 mg/0.7 mL (0.7 mL); 40 mg/mL (1 mL); 80 mg/0.8 mL (0.8 mL) [contains mouse (murine) and/or hamster protein]
Brand Names: U.S.
Asfotase alfa is a human recombinant tissue-nonspecific alkaline phosphatase-Fc-deca-aspartate fusion protein with enzymatic activity that promotes bone mineralization in patients with hypophosphatasia.
Onset of Action
Reduction in plasma TNSALP substrates: After 6 to 12 weeks of treatment
Time to Peak
Infants and Children ≤5 years: ~15 hours (range: 0 to 32.2 hours)
Children > 5 to 12 years: ~ 21 hours (range: 12 to 32.2 hours)
~5 days (based on data from 38 patients, ages undefined); in 60 patients aged 1 day to 66 years (n=45 pediatric patients): ~2.3 days
Use: Labeled Indications
Hypophosphatasia: Treatment of perinatal/infantile- and juvenile-onset hypophosphatasia (HPP)
There are no contraindications listed in the manufacturer’s labeling.
Canadian labeling: Additional contraindications (not in US labeling): Hypersensitivity to asfotase alfa or any component of the formulation.
Hypophosphatasia (HPP): SubQ: Note: Round patient weight to the nearest kg when determining dose. Injection-site reactions may limit the tolerability of the 6 times per week regimen:
Juvenile-onset HPP: 2 mg/kg 3 times weekly or 1 mg/kg 6 times weekly.
Note: Round patient weight to the nearest kg when determining dose. Do not administer the 80 mg/0.8 mL concentration vial to pediatric patients weighing <40 kg; exposure is less than what is achieved with lower concentration vials.
Perinatal/infantile-onset hypophosphatasia (HPP): Infants, Children, and Adolescents: SubQ: 6 mg/kg/week administered as either 2 mg/kg/dose 3 times weekly or 1 mg/kg/dose 6 times weekly; may titrate due to lack of efficacy (eg, no improvement in respiratory status, growth, or radiographic findings) up to 9 mg/kg/week administered as 3 mg/kg/dose 3 times weekly; in clinical trials, dose increases were considered after at least 4 weeks of therapy (Whyte 2012; Whyte 2016); maximum total weekly dose: 9 mg/kg/week. Injection-site reactions may limit the tolerability of the 6-times-per-week regimen.
Juvenile-onset hypophosphatasia (HPP): Children and Adolescents: SubQ: 6 mg/kg/week administered as either 2 mg/kg/dose 3 times weekly or 1 mg/kg/dose 6 times weekly. Injection-site reactions may limit the tolerability of the 6-times-per-week regimen.
SubQ: For subcutaneous administration only in the abdominal area, thigh, deltoid, or buttocks. Do not shake. Allow unopened vials to reach room temperature (~15 to 30 minutes) prior to administration; do not warm in microwave or hot water; administer within 3 hours upon removal from refrigerator. Rotate the injection sites to reduce the risk of lipodystrophy. Do not administer injections in areas that are reddened, inflamed, or swollen. Solution is clear, slightly opalescent or opalescent, colorless to slightly yellow; few small translucent or white particles may be present; discard vial(s) not consistent with this appearance. Administer with 1 mL syringe with 1/2 inch needle (25 to 29 gauge). Use of 2 different gauge needles is recommended; 25 gauge to withdraw medication from the vial and 29 gauge for administration. For doses >1 mL, split the volume equally between 2 syringes, and administer 2 injections using separate injection sites.
Store refrigerated at 2°C to 8°C (36°F to 46°F) in original carton and protect from light. Once removed from refrigerator, administer within 3 hours. Do not freeze or shake. Discard any unused product.
There are no known significant interactions.
Asfotase alfa interferes with alkaline phosphatase (ALP)-conjugated test systems (commonly used to measure hormones, bacterial antigens, and antibodies) rendering erroneous test results. Alternative laboratory assays that do not utilize ALP-conjugate technology are recommended in patients receiving asfotase alfa.
Endocrine & metabolic: Ectopic calcification (includes calcification of the cornea, conjunctiva, and kidneys; 55%, juvenile-onset HPP; ≤5% perinatal/infantile-onset HPP), lipodystrophy (≤6%)
Hypersensitivity: Hypersensitivity reaction (10% to 23%)
Immunologic: Immunogenicity (positive for antidrug antibodies: 78%; neutralizing: 45%; presence of antidrug antibodies resulted in reduced systemic exposure of asfotase alfa)
Local: Erythema at injection site (juvenile-onset HPP: 75%; perinatal/infantile-onset HPP: 23% to 44%), atrophy at injection site (juvenile-onset HPP: 40%; perinatal/infantile-onset HPP: 6% to 15%), skin discoloration at injection site (including macules: Juvenile-onset HPP: 35% to 40%; perinatal/infantile-onset HPP: ≤17%), pain at injection site (juvenile-onset HPP: ≤40%; perinatal/infantile-onset HPP: ≤8% to ≤15%), tenderness at injection site (juvenile-onset HPP: ≤40%; perinatal/infantile-onset HPP: ≤15%), itching at injection site (juvenile-onset HPP: 35%; perinatal/infantile-onset HPP: ≤15%), hypertrophy at injection site (juvenile-onset HPP: 30%; perinatal/infantile-onset HPP: ≤8%), swelling at injection site (juvenile-onset HPP: 30%; perinatal/infantile-onset HPP: ≤12%), injection site reaction (≤23%; including rash, nodule, papule, inflammation, hemorrhage, hematoma, calcification, mass, scar, cellulitis, or not otherwise defined), bruising at injection site (juvenile-onset HPP: 20%; perinatal/infantile-onset HPP: ≤9%), induration at injection site (8% to 15%)
<1%, postmarketing, and/or case reports: Chronic active hepatitis, hypocalcemia, nephrolithiasis, pyridoxine deficiency
Concerns related to adverse effects:
• Antibody formation/immune-mediated effects: The presence of antibodies has been reported in 89% of treated patients in clinical trials; 57% of these patients showed the presence of neutralizing antibodies. Formation of anti-drug antibody results in a reduced systemic exposure of asfotase alfa and suggests possible immune-mediated effects resulting in disease progression (effect of antibody formation on long-term efficacy is unknown). Consider anti-asfotase alfa antibody testing in patients with progression of symptoms or worsening of disease associated laboratory and imagining biomarkers after a period of initial therapeutic response (contact Strensiq Medical Information at 1-888-765-4747 or email@example.com).
• Ectopic calcifications: Ectopic calcification of the eye, including the cornea and conjunctiva, and the kidneys (nephrocalcinosis, nephrolithiasis) have been reported; there is insufficient information to determine if these events were consistent with the disease (patients with hypophosphatasia are at increased risk for developing ectopic calcifications) or due to asfotase alfa. No visual changes or changes in renal function were reported resulting from the occurrence of ectopic calcifications. Eye exams and renal ultrasounds are recommended at baseline and periodically during treatment.
• Hypersensitivity reactions: Hypersensitivity reactions, including anaphylaxis, have been reported; symptoms consistent with anaphylaxis, including difficulty breathing, choking sensation, nausea, periorbital edema, and dizziness, have been reported. Reactions may occur within minutes after administration or in patients on treatment for >1 year. Other hypersensitivity reactions (eg, vomiting, fever, headache, flushing, irritability, chills, skin erythema, rash, pruritus, oral hypoesthesia) have also been reported. If a severe hypersensitivity reaction occurs, discontinue treatment and initiate appropriate medical treatment. If the decision is made to re-administer, monitor patients for a reoccurrence of signs and symptoms of a severe hypersensitivity reaction.
• Lipodystrophy: Localized lipodystrophy, including lipoatrophy and lipohypertrophy, has been reported at injection sites after several months. Ensure proper injection technique and rotate injection sites.
• Elevated alkaline phosphatase: High serum alkaline phosphatase (ALP) levels are expected and reflect circulating asfotase alfa; serum ALP measurements should not be used to make clinical decisions during asfotase alfa treatment.
Hypersensitivity reaction; signs and symptoms of ophthalmic and renal ectopic calcifications and for changes in vision or renal function
Adverse events have not been observed in animal reproduction studies.
What is this drug used for?
• It is used to treat a health problem that leads to bone and teeth growth that is not normal called hypophosphatasia.
All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
• Injection site irritation or skin discoloration
WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:
• Upset stomach
• Throwing up
• Eye or eyelid swelling
• Dizziness or passing out
• Feeling irritable
• Numbness or tingling of the mouth
• Injection site thick skin, pits, or lumps
• Vision changes
• Not able to pass urine or change in amount of urine passed
• Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
Note: This is not a comprehensive list of all side effects. Talk to your doctor if you have questions.
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