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

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Strensiq® improved movement in patients with juvenile-onset hypophosphatasia (HPP).1,9



Mobility and gait improved in patients with juvenile-onset hypophosphatasia treated with Strensiq®.1

At 48 months, all treated patients had percent-predicted 6-minute walk test (6MWT) values within the normal range1,a,b

Mean distance walked as measured by 6MWT9,a

Mobility was measured using the 6MWT, an established measure of walking ability12

aMobility was assessed in Study 3 in patients 6 to 12 years of age with juvenile-onset hypophosphatasia using the 6MWT.1

b6MWT results were converted to mean percent-predicted values. Obtained values were expressed as a percentage of those observed in sex-, age-, and height-matched healthy children.9

Patients treated with Strensiq® saw improvements in gait vs untreated historical controls.1,a

75% of patients (6 out of 8) treated with Strensiq® had an improvement in step length while only 17% of the untreated controls (1 out of 6) showed any improvement in step length1

aGait improvements were assessed in Study 3 using the Modified Tinetti Performance-Oriented Mobility Assessment-Gait (MPOMA-G) subtest in 8 patients 6 to 12 years of age treated with Strensiq at 6-month intervals out to 36 months, and were compared with untreated historical controls (n=6).1

Strensiq® Patient Video
6-Minute Walk Test (6MWT)

(6MWT at baseline and 24 months)


The above video shows a patient during the 6MWT at baseline and at 24 months9

Results for the patient at baseline, 24 months, and 48 months are compared to the study mean in the Summary of Results table, below. The patient was 7 years, 3 months of age at study baseline and 9 years, 2 months of age at the 24-month (96-week) follow-up evaluation9

Summary of Results

Baseline 24 Months 48 Months
Patient in Video 217 meters [age 7 years]
(41% of predicted normal distance)a
438 meters [age 9 years]
(76% of predicted normal distance)a
559 meters [age 11 years]
(92% of predicted normal distance)a
Study Mean (SD) n=8
343 meters
(59% of predicted normal distance)a
528 meters
(83% of predicted normal distance)a
588 meters
(89% of predicted normal distance)a

a6-minute walk test results were converted to mean percent-predicted values. Obtained values were expressed as a percentage of those observed in sex-, age-, and height-matched healthy children.9

Results in adult patients with perinatal/infantile- and juvenile-onset hypophosphatasia with Strensiq®.9,17

Median distance walked as measured by the 6MWT9

aBaseline distance includes patients in the control group (n=3) and those treated with Strensiq (n=7) for the first 24 weeks of the study.
At 192 weeks, patients in the control group had not yet reached 192 weeks of therapy and 1 patient did not complete the 6MWT.9

In Study 4, decreases in plasma PPI and PLP were observed at week 24. These differences were not significantly different than those of the control group at 24 weeks.17 Reduction in plasma PPI and PLP did not correlate with clinical outcomes.1

Speed and Agility

Speed and agility improved in patients with juvenile-onset hypophosphatasia treated with Strensiq®.9

The median score for speed and agility was within 1 standard deviation of the normal mean at 192 weeks9

Median speed and agility over time9,a

aSpeed and agility were assessed in patients 6 to 12 years of age in Study 3 using the Bruininks-Oseretsky Test of Motor Proficiency (BOT-2).9 The BOT-2 assesses motor proficiency in normally developing individuals as well as in those with moderate motor deficits. Proficiency is normalized and reported in scaled scores.18



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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