asfotase alfa (Rx)

Brand and Other Names:Strensiq
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

SC injectable solution

  • 80 mg/0.8mL (use for patients who weigh >40kg)

Hypophosphatasia

Indicated for perinatal/infantile- and juvenile-onset hypophosphatasia (HPP)

6 mg/kg/week SC administered as 2 mg/kg given 3 x/week or 1 mg/kg given 6 x/week

Injection site reactions may limit the tolerability of the 6 x/week regimen

Note: For perinatal/infantile-onset HPP, the dose may be increased for lack of efficacy (eg, no improvement in respiratory status, growth, or radiographic findings) up to 9 mg/kg per week administered SC as 3 mg/kg 3 x/week

Dosage Forms & Strengths

SC injectable solution

  • 18mg/0.45mL
  • 28mg/0.7mL
  • 40mg/mL
  • 80 mg/0.8mL (use for patients who weigh >40kg)

Hypophosphatasia

Indicated for perinatal/infantile- and juvenile-onset hypophosphatasia (HPP)

6 mg/kg/week SC administered as 2 mg/kg given 3 x/week or 1 mg/kg given 6 x/week

Injection site reactions may limit the tolerability of the 6 x/week regimen

Note: For perinatal/infantile-onset HPP, the dose may be increased for lack of efficacy (eg, no improvement in respiratory status, growth, or radiographic findings) up to 9 mg/kg per week administered SC as 3 mg/kg 3 x/week

Dosing Considerations

Caution: Do not use the 80-mg/0.8 mL vial in pediatric patients weighing <40 kg because the 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

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Adverse Effects

>10%

Injection site reactions (46-90%)

Lipodystrophy (18-70%)

Ectopic calcifications (5-55%)

1-10%

Vomiting/emesis (3-10%)

Systemic hypersensitivity reactions (2-10%)

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Warnings

Contraindications

None

Cautions

Hypersensitivity reactions (rare) reported in clinical trials; reactions have occurred within minutes after subcutaneous administration and have been observed more than 1 year after treatment initiation; monitor and if severe reaction occurs, discontinue treatment and initiate appropriate medical treatment

Localized lipodystrophy, including lipoatrophy and lipohypertrophy, has been reported at injection sites after several months; monitor for proper injection technique and injection site rotation

Patients with HPP are at increased risk for developing ectopic calcifications; in clinical trials, 14 cases (14%) of ectopic calcification of the eye, including the cornea and conjunctiva, and the kidneys (nephrocalcinosis) were reported; there was insufficient information to determine whether or not the reported events were consistent with the disease or associated with asfotase alfa; ophthalmology examinations and renal ultrasounds are recommended at baseline and periodically during treatment

Studies have shown that there is analytical interference between asfotase alfa and laboratory tests that utilize an alkaline phosphatase (ALP)-conjugated test system, rendering erroneous test results in patients treated; recommended that laboratory assays which do not have ALP- conjugate technology be used when testing samples from patients; inform laboratory personnel that patient is being treated with drug and discuss use of testing platform which does not utilize an ALP-conjugated test system

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Pregnancy

Pregnancy

There are no available human data on asfotase alfa use in pregnant women to inform a drug associated risk

In animal reproduction studies, asfotase alfa administered IV to pregnant rats and rabbits during the period of organogenesis showed no evidence of fetotoxicity, embryo lethality, or teratogenicity at doses causing plasma exposures up to 21 and 24 times, respectively, the exposure at the recommended human dose

Lactation

Unknown if distributed in human breast milk

Pregnancy Categories

A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

NA: Information not available.

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Pharmacology

Mechanism of Action

Enzyme replacement that is a soluble glycoprotein composed of 2 identical polypeptide chains; each chain consists of the catalytic domain of human tissue nonspecific alkaline phosphatase (TNSALP), the human immunoglobulin G1 Fc domain and a deca-aspartate peptide used as a bone targeting domain

HPP is caused by a deficiency in TNSALP enzyme activity, which leads to elevations in several TNSALP substrates, including inorganic pyrophosphate (PPi)

Elevated extracellular levels of PPi block hydroxyapatite crystal growth, which inhibits bone mineralization and causes an accumulation of unmineralized bone matrix, which manifests as rickets and bone deformation in infants and children and as osteomalacia (softening of bones) once growth plates close, along with muscle weakness

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Administration

SC Preparation

Determine the volume needed for the prescribed weight-based dose

  • Total dose (mg) = patient’s weight (kg) x prescribed dose (mg/kg)
  • Total injection volume (mL) = Total dose (mg) divided by concentration (40 mg/mL or 80 mg/0.8 mL)
  • Round total injection volume to the nearest hundredth of a mL
  • Total number of vials = Total injection volume divided by vial volume (mL)
  • If the volume for injection is >1 mL, split the volume equally between 2 syringes, and administer as 2 SC injections (use separate injection sites)
  • See prescribing information for detailed weight-based charts

Prepare the syringe(s)

  • Inspect the solution in the vial(s) for particulate matter and discoloration
  • Should appear as a clear, slightly opalescent or opalescent, colorless to slightly yellow aqueous solution; few small translucent or white particles may be present
  • Discard any vials(s) not consistent with this appearance
  • Assemble injection supplies
  • Administer using sterile disposable 1-mL syringes and 0.5-inch injection needles, from 25- to 29-gauge
  • Remove vial cap, aseptically prepare the vial, and insert the syringe into the vial to withdraw the prescribed dose for administration
  • Remove any air bubbles in the syringe and verify the correct dose

SC Administration

For SC administration only

Administer within 1 hr upon removal of the vial(s) from refrigeration

Rotate the injection from among the following sites to reduce the risk of lipodystrophy: abdominal area, thigh, or deltoid

Do NOT administer injections in areas that are reddened, inflamed, or swollen

Inject SC into the determined site and properly dispose of the needle

Vials are single use only; discard any unused product

Storage

Store refrigerated 2-8°C (36-46°F)

Store unopened vials in the original carton to protect from light

Do not freeze or shake

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Images

No images available for this drug.
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Patient Handout

A Patient Handout is not currently available for this monograph.
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Formulary

FormularyPatient Discounts

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To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

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The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

Tier Description
1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
NC NOT COVERED – Drugs that are not covered by the plan.
Code Definition
PA Prior Authorization
Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
QL Quantity Limits
Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
ST Step Therapy
Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
OR Other Restrictions
Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.