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Learn more about Strensiq® (asfotase alfa) and HPP.

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By replacing alkaline phosphatase, Strensiq® treats the underlying cause of hypophosphatasia (HPP).1

The underlying cause of hypophosphatasia is deficient tissue-nonspecific alkaline phosphatase (TNSALP) activity.1

Hypophosphatasia is a lifelong disease caused by loss-of-function mutations in the ALPL gene, which encodes the tissue-nonspecific form of alkaline phosphatase (TNSALP).3-5 Deficient TNSALP leads to elevations in several TNSALP substrates (eg, inorganic pyrophosphate), causing rickets and bone deformation in infants and children and osteomalacia (softening of bones) once growth plates close, along with muscle weakness.1

Patients with hypophosphatasia suffer from a variety of skeletal manifestations.3 In a historical cohort of untreated patients with life-threatening perinatal/infantile-onset hypophosphatasia, >50% of patients died by the first year of life. The primary cause of death in the cohort was respiratory complications and/or failure.6 Patients with hypophosphatasia who survive into childhood and adolescence can suffer from skeletal issues, growth delays, and limited mobility.1,3,4,7,8


Strensiq® replaces the deficient TNSALP enzyme and reduces the enzyme substrate levels.1


In Strensiq clinical trials, mean alkaline phosphatase levels varied across populations studied and increased typically well above the upper limit of normal9

  • The levels remained elevated during the treatment period, reflecting ongoing treatment with Strensiq9


Treatment with Strensiq lowered plasma levels of the alkaline phosphatase substrates inorganic pyrophosphate (PPi) and pyridoxal 5’-phosphate (PLP) within 6 to 12 weeks of treatment1

  • Reductions in PPi and PLP did not correlate with clinical outcomes1

Strensiq® improved bone mineralization in patients with perinatal/infantile- and juvenile-onset hypophosphatasia.1

Bone biopsy data indicated that both osteoid volume and thickness decreased during treatment with Strensiq.1

Strensiq® Product Video




STRENSIQ® is indicated for the treatment of patients with perinatal/infantile- and juvenile-onset hypophosphatasia (HPP).


  • Hypersensitivity Reactions, including anaphylaxis, have been reported in STRENSIQ-treated patients. Signs and symptoms consistent with anaphylaxis included difficulty breathing, choking sensation, nausea, periorbital edema, and dizziness. These reactions have occurred within minutes after subcutaneous administration of STRENSIQ and and have been observed more than 1 year after treatment initiation. Other hypersensitivity reactions have also been reported in STRENSIQ-treated patients, including vomiting, fever, headache, flushing, irritability, chills, skin erythema, rash, pruritus and oral hypoesthesia.
    Inform patients and/or caregivers of the signs and symptoms of hypersensitivity reactions and have them seek immediate medical care should signs and symptoms occur. If a severe hypersensitivity reaction occurs, discontinue STRENSIQ treatment and initiate appropriate medical treatment. Consider the risks and benefits of re-administering STRENSIQ to individual patients following a severe reaction. If the decision is made to re-administer the product, monitor patients for a reoccurrence of signs and symptoms of a severe hypersensitivity reaction.
  • Lipodystrophy: Localized lipodystrophy, including lipoatrophy (depression in the skin) and lipohypertrophy (enlargement or thickening of tissue), has been reported at injection sites after several months in patients treated with STRENSIQ in clinical trials. Advise patients to follow proper injection technique and to rotate injection sites.
  • Ectopic Calcifications: Patients with HPP are at increased risk for developing ectopic calcifications. Events of ectopic calcification, including ophthalmic (conjunctival and corneal) and renal (nephrocalcinosis, nephrolithiasis), have been reported in the clinical trial experience with STRENSIQ. There was insufficient information to determine whether or not the reported events were consistent with the disease or due to STRENSIQ. No visual changes or changes in renal function were reported resulting from the occurrence of ectopic calcifications.
    Ophthalmology examinations and renal ultrasounds are recommended at baseline and periodically during treatment with STRENSIQ to monitor for signs and symptoms of ophthalmic and renal ectopic calcifications and for changes in vision or renal function.
  • Possible Immune-Mediated Clinical Effects: In clinical trials, most STRENSIQ-treated patients developed anti-asfotase alfa antibodies and neutralizing antibodies which resulted in reduced systemic exposure of asfotase alfa. In postmarketing reports, some STRENSIQ-treated patients with initial therapeutic response subsequently developed recurrence and worsening in disease-associated laboratory and radiographic biomarkers (some in association with neutralizing antibodies) suggesting possible immune-mediated effects on STRENSIQ’s pharmacologic action resulting in disease progression. The effect of anti-asfotase alfa antibody formation on the long-term efficacy of STRENSIQ is unknown. There are no marketed anti-asfotase alfa antibody tests. If patients experience progression of HPP symptoms or worsening of disease-associated laboratory and imaging biomarkers after a period of initial therapeutic response to STRENSIQ, consider obtaining anti-asfotase alfa antibody testing by contacting STRENSIQ Medical Information at Alexion at 1-888-765-4747 or by email at Close clinical follow up is recommended.

Overall, the most common adverse reactions (≥ 10%) reported were injection site reactions (63%). Other common adverse reactions included lipodystrophy (28%), ectopic calcifications (14%), and hypersensitivity reactions (12%). Possible immune-mediated clinical effects have been identified during post-approval use of STRENSIQ.


Drug Interference with Laboratory Tests:
  • Laboratory tests utilizing alkaline phosphatase (ALP) as a detection reagent could result in erroneous test results for patients receiving treatment due to the presence of asfotase alfa in clinical laboratory samples. Inform laboratory personnel that the patient is being treated with STRENSIQ and discuss use of an alternative testing platform which does not utilize an ALP-conjugated test system.
  • Elevated serum ALP measurements detected through clinical laboratory testing are expected in patients receiving STRENSIQ due to circulating concentrations of asfotase alfa and may be unreliable for clinical decision making.
  • Pregnancy & Lactation: There are no available data on STRENSIQ use in pregnant women, the presence of STRENSIQ in human milk, or the effects on the breastfed infant or on milk production, to inform a drug associated risk.
Please see STRENSIQ (asfotase alfa) full Prescribing Information.

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