STRENSIQ® (asfotase alfa)


STRENSIQ is an innovative enzyme replacement therapy approved for the treatment of patients with perinatal/infantile- and juvenile-onset hypophosphatasia (HPP).1 STRENSIQ is approved in the United States, European Union, Japan, Canada, and other countries.

Strensiq vial

STRENSIQ is the first therapy indicated in patients with perinatal/infantile- and juvenile-onset HPP to treat the underlying cause of HPP—deficient TNSALP. By replacing the deficient ALP, STRENSIQ reduces the elevated enzyme substrate levels and improves bone mineralization. STRENSIQ is administered via subcutaneous injection (injection under the skin).1

The safety and efficacy of STRENSIQ were evaluated in 4 prospective, open-label clinical trials and supporting extension trials comprising 112 patients with HPP (ages 1 day to 66.5 years) who received treatment with STRENSIQ for up to 7.5 years.2-7 At 48 weeks, estimated overall survival was 94% for STRENSIQ-treated patients compared with 42% for untreated historical control patients (hazard ratio [95% CI], 0.174 [0.072, 0.421]).2-5

Patients treated with STRENSIQ also demonstrated radiographic improvement. In patients with perinatal/infantile-onset HPP, 78% (63/81) of patients treated with STRENSIQ were rated as responders on the 7-point Radiographic Global Impression of Change (RGI-C) scale at last assessment (mean time from baseline to last assessment was 35.7 months; range was 2.5 months to 89.4 months).2-4,6 In patients with juvenile-onset HPP, 100% (8/8) of STRENSIQ-treated patients were rated as RGI-C responders by 54 months of treatment compared with 6% (2/32) of untreated historical control patients (mean duration between baseline and last assessment for control patients was 56 months; range was 8 to 95 months).6

The most common adverse reactions (≥10%) are: injection site reactions, lipodystrophy, ectopic calcifications, and hypersensitivity reactions.1

Learn more about treatment with STRENSIQ


Strensiq is a prescription medicine used to treat people with perinatal/infantile- and juvenile-onset hypophosphatasia (HPP).


What are the possible side effects of STRENSIQ?
STRENSIQ may cause serious side effects, including


  • Serious allergic (hypersensitivity) reactions happened in some people who use STRENSIQ. Stop using STRENSIQ and go to the nearest hospital emergency room right away if you or your loved one have any of the signs and symptoms of a serious allergic reaction, including
    • Difficulty breathing
    • Swelling of your eyes, lips, or tongue
    • Hives
    • Feeling faint
    • Nausea or vomiting
    • Dizziness
    • Itching of your lips, tongue, or throat
    • Choking sensation
  • Skin thickening or pits at the injection site (lipodystrophy) has happened several months after using STRENSIQ.
  • Calcium buildup in the eyes and kidneys can occur if you or your loved one have HPP. Your healthcare provider should check the eyes and kidneys while you or your loved one use STRENSIQ.
  • Decreased efficacy. Contact your healthcare provider if you or your loved one notice STRENSIQ is no longer working or experience worsening symptoms of HPP (e.g., increased respiratory support, increased difficulty walking, new fractures).

The most common side effects of STRENSIQ include local skin injection-site reactions (red skin patches, bruising, color change, pain, itching, thinning, swelling, pits, and bumps) and calcium buildup in your eyes and kidneys.

Strensiq may affect other lab test results, therefore it is important that you present your Medical Alert Card to your healthcare team so they are aware that you are being treated with an alkaline phosphatase (ALP) replacement therapy which may cause incorrect results on certain laboratory tests.

Tell your doctor if you are pregnant or plan to become pregnant or are breastfeeding or plan to breastfeed.

These are not all the possible side effects of STRENSIQ. For more information, ask your healthcare provider or pharmacist. Call your healthcare provider for medical advice about side effects. You may report side effects to the US Food and Drug Administration at 1-800-FDA-1088.

Please see STRENSIQ full Prescribing Information, including Patient Information and Instructions for Use.


  1. Strensiq [package insert]. Boston, MA: Alexion Pharmaceuticals, Inc; 2020.
  2. Whyte MP, Greenberg CR, Salman NJ, et al. Enzyme-replacement therapy in life-threatening hypophosphatasia. N Engl J Med. 2012;366(10):904-913.
  3. Whyte MP, Simmons JH, Moseley S, et al. Asfotase alfa for infants and young children with hypophosphatasia: 7 year outcomes of a single-arm, open-label, phase 2 extension trial. Lancet Diabetes Endocrinol. 2018;8587(18):1-12.
  4. Hofmann CE, Harmatz P, Vockley J, et al. Efficacy and safety of asfotase alfa in infants and young children with hypophosphatasia: a phase 2 open-label study. J Clin Endocrinol Metab. 2019;104(7):2735-2747.
  5. Whyte MP, Rockman-Greenberg C, Ozono K, et al. Asfotase alfa treatment improves survival for perinatal and infantile hypophosphatasia. J Clin Endocrinol Metab. 2016;101(1):334-342.
  6. Whyte MP, Madson KL, Phillips D, et al. Asfotase alfa therapy for children with hypophosphatasia. JCI Insight. 2016;1(9):e85971.
  7. Kishnani PS, Rockman-Greenberg C, Rauch F, et al. Five-year efficacy and safety of asfotase alfa therapy for adults and adolescents with hypophosphatasia. Bone. 2019;121:149-162.


Evie, diagnosed with HPP at 2 weeks old, riding a toy car
Her story gives other parents with special needs kids hope that they can be okay, and things can be good.”