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Asfotase Alfa

Pronunciation

(AZ fo tase AL fa)

Index Terms

  • Strensiq

Dosage Forms

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.

  • Strensiq

Pharmacologic Category

  • Enzyme

Pharmacology

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

~15 to 21 hours

Half-Life Elimination

~5 days

Use: Labeled Indications

Hypophosphatasia: Treatment of perinatal/infantile- and juvenile-onset hypophosphatasia (HPP)

Contraindications

There are no contraindications listed in the manufacturer’s labeling.

Dosing: Adult

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.

Dosing: Pediatric

Hypophosphatasia (HPP): SubQ: 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. Injection-site reactions may limit the tolerability of the 6 times per week regimen:

Perinatal/infantile-onset HPP: Infants, Children, and Adolescents: 2 mg/kg 3 times weekly or 1 mg/kg 6 times weekly. May increase dose for lack of efficacy (eg, no improvement in respiratory status, growth, or radiographic findings) up to 3 mg/kg 3 times weekly (maximum: 9 mg/kg per week).

Juvenile-onset HPP: Children, Adolescents, and Adults: 2 mg/kg 3 times weekly or 1 mg/kg 6 times weekly.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.

Dosing: Hepatic Impairment

There are no dosage adjustments provided in the manufacturer’s labeling.

Administration

For subcutaneous administration only in the abdominal area, thigh, or deltoid. Administer within 1 hour 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). For doses >1 mL, split the volume equally between 2 syringes, and administer 2 injections using separate injection sites.

Do not use the 80 mg/0.8 mL vial in pediatric patients <40 kg (systemic exposure of asfotase alfa achieved with the 80 mg/0.8 mL vial [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.

Storage

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 1 hour. Do not freeze or shake. Discard any unused product.

Drug Interactions

There are no known significant interactions.

Adverse Reactions

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% (Limited to important or life-threatening): Chronic active hepatitis, hypocalcemia, nephrolithiasis, pyridoxine deficiency

Warnings/Precautions

Concerns related to adverse effects:

• Antibody formation: The presence of antibodies has been reported in 78% of treated patients in clinical trials. Approximately 45% of these patients showed the presence of neutralizing antibodies. Formation of anti-drug antibody results in a reduced systemic exposure of asfotase alfa.

• Ectopic calcifications: Ectopic calcification of the eye, including the cornea and conjunctiva, and the kidneys (nephrocalcinosis) 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 have been reported; symptoms consistent with anaphylaxis, including difficulty breathing, nausea, periorbital edema, and dizziness, have been reported. 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. 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.

Monitoring Parameters

Hypersensitivity reaction; signs and symptoms of ophthalmic and renal ectopic calcifications and for changes in vision or renal function

Pregnancy Considerations

Adverse events have not been observed in animal reproduction studies

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience injection site irritation or skin discoloration at injection site. Have patient report immediately to prescriber nausea, vomiting, eyelid edema, dizziness, passing out, chills, headache, flushing, irritability, numbness or tingling of the mouth, or skin changes (thick or thin) at injection site (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience,and judgment in diagnosing, treating, and advising patients.

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