About ELAPRASE (idursulfase)

ELAPRASE is targeted to replace iduronate-2-sulfatase (I2S), the enzyme that is deficient or absent in people with Hunter syndrome.


Some patients have experienced serious allergic reactions (including life threatening anaphylactic reactions) during and up to 24 hours after treatment, regardless of how long they were taking ELAPRASE. Anaphylactic reactions are immediate and include breathing problems, low oxygen levels, low blood pressure, hives and/or swelling of the throat or tongue. If a patient (you or your child) has experienced an anaphylactic reaction, the patient may require an extended period of observation by the patient’s healthcare team. If you or your child has breathing problems, a fever, or a respiratory illness, you or your child may be at risk of life-threatening worsening of those conditions due to allergic reactions from ELAPRASE. Your healthcare team should be advised of those conditions before treatment with ELAPRASE because the information may affect the timing of ELAPRASE treatment.

The risk of anaphylaxis is not the only warning or precaution for Elaprase. Additional warnings and precautions are the risks of: hypersensitivity, serious adverse reactions, and antibody development in patients with severe genetic mutations; acute respiratory complications; and, acute cardiorespiratory failure. Please see the Important Safety Information below and the full Prescribing Information.

Adverse Reactions

Clinical Trial in Patients ≥ 5 Years of Age

In clinical trials with 96 male patients age 5 and older with Hunter Syndrome, the most common adverse reactions (occurring in more than 10% of patients) following ELAPRASE treatment were hypersensitivity (allergic) reactions, and included rash, hives, itching, flushing, fever, and headache. The most frequent serious adverse reactions were episodes of insufficient oxygen supply, called hypoxia.

Adverse reactions that occurred in at least 9% of patients in the ELAPRASE 0.5 mg/kg once-weekly group and with a higher incidence than in the placebo group were:

Adverse Reaction ELAPRASE (0.5 mg/kg weekly) N=32 n (%) Placebo N=32 n (%)
Headache 9 (28%) 8 (25%)
Itching (Pruritis) 8 (25%) 3 (9%)
Hives (Urticaria) 5 (16%) 0 (0%)
Musculoskeletal Pain 4 (13%) 1 (3%)
Cough 3 (9%) 1 (3%)
Diarrhea 3 (9%) 1 (3%)

Hypersensitivity reactions were reported in 69% of patients who received once-weekly treatment with ELAPRASE.

Additional adverse reactions that occurred in at least 9% of patients (≥3 patients) in the ELAPRASE 0.5 mg/kg every other week group and with a higher incidence than in the placebo group included: rash (19%), flushing (16%), fatigue (13%), rapid heart rate (9%), and chills (9%).

Adverse Reactions Reported Since Approval of ELAPRASE

Late-emergent symptoms and signs of anaphylactic reactions have occurred up to 24 hours after initial treatment and recovery from an initial anaphylactic reaction. In addition, patients experienced repeated anaphylaxis over a two- to four-month period, up to several years after initiating ELAPRASE treatment.

Serious adverse reactions that resulted in death included cardiorespiratory arrest, respiratory failure, respiratory distress, cardiac failure, and pneumonia.

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