ical outcome; however, treatment with elaprase has reduced spleen volume similarly to that of adults and children 5 years of age and older. the safety and efficacy of elaprase have not been established in pediatric patients less than 16 months of age ( 1 ).

f elaprase and consider delaying the elaprase infusion ( 5.3 ). 5.1 hypersensitivity reactions including anaphylaxis serious hypersensitivity reactions, including anaphylaxis, have occurred during and up to 24 hours after infusion. some of these reactions were life-threatening and included respiratory distress, hypoxia, hypotension, urticaria, and angioedema of the throat or tongue, regardless of duration of the course of treatment. if anaphylactic or other acute reactions occur, immediately discontinue the infusion of elaprase and initiate appropriate medical treatment. when severe reactions have occurred during clinical trials, subsequent infusions were managed with antihistamine and/or corticosteroids prior to or during infusions, a slower rate of elaprase infusion, and/or early discontinuation of the elaprase infusion [see adverse reactions (6) ] . in clinical trials with elaprase, 16 of 108 (15%) patients experienced hypersensitivity reactions during 26 of 8,274 infusions (0.3%) that involved adverse events in at least two of the following three body systems: cutaneous, respiratory, or cardiovascular. of these 16 patients, 11 experienced anaphylactic reactions during 19 of 8,274 infusions (0.2%) with symptoms of bronchospasm, cyanosis, dyspnea, erythema, edema (facial and peripheral), flushing, rash, respiratory distress, urticaria, vomiting, and wheezing. in postmarketing reports, patients receiving elaprase experienced anaphylactic reactions up to several years after initiating treatment. some patients were reported to have repeated anaphylactic events over a two- to four-month time period. medical management included treatment with antihistamines, inhaled beta-adrenergic agonists, corticosteroids, oxygen, and vasopressors. treatment was discontinued for some patients, while others continued treatment with premedication and a slower infusion rate. due to the potential for severe reactions, appropriate medical support should be readily available when elaprase is administered. observe patients closely for an appropriate period of time after administration of elaprase, taking into account the time to onset of anaphylaxis seen in premarketing clinical trials and postmarketing reports. inform patients of the signs and symptoms of anaphylaxis, and instruct them to seek immediate medical care should signs and symptoms occur. 5.2 risk of hypersensitivity, serious adverse reactions, and antibody development in hunter syndrome patients with severe genetic mutations in the clinical trial of hunter syndrome patients aged 7 years and younger, patients with complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations experienced a higher incidence of hypersensitivity reactions, serious adverse reactions, and anti-idursulfase antibody development than hunter syndrome patients with missense mutations. eleven of 15 (73%) patients with complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations and five of 12 (42%) patients with missense mutations experienced hypersensitivity reactions. nine of 15 (60%) patients with complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations and two of 12 (17%) patients with missense mutations had serious adverse reactions. all 15 patients with complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations developed anti-idursulfase (elaprase) antibodies, compared to only 3 patients with missense mutations (table 2). thirteen patients with these mutations developed neutralizing antibodies, which interfere with elaprase uptake into the cell or elaprase enzyme activity, compared to only one patient with missense mutation [see warnings and precautions (5.1) , adverse reactions (6.1 , 6.2) , and use in specific populations (8.4) ] . 5.3 risk of acute respiratory complications patients with compromised respiratory function or acute febrile or respiratory illness at the time of elaprase infusion may be at higher risk of life-threatening complications from hypersensitivity reactions. careful consideration should be given to the patient's clinical status prior to administration of elaprase and consider delaying the elaprase infusion. one patient with a tracheostomy, severe airway disease, and acute febrile illness experienced respiratory distress, hypoxia, cyanosis, and seizure with a loss of consciousness during elaprase infusion. 5.4 risk of acute cardiorespiratory failure caution should be exercised when administering elaprase to patients susceptible to fluid overload, or patients with acute underlying respiratory illness or compromised cardiac and/or respiratory function for whom fluid restriction is indicated. these patients may be at risk of serious exacerbation of their cardiac or respiratory status during infusions. appropriate medical support and monitoring measures should be readily available during elaprase infusion, and some patients may require prolonged observation times that should be based on the individual needs of the patient [see adverse reactions (6.1 , 6.3) ] .

m the refrigerator to allow them to reach room temperature. before withdrawing the elaprase solution from the vial, visually inspect each vial for particulate matter and discoloration. the elaprase solution should be clear to slightly opalescent and colorless. do not use if the solution is discolored or if there is particulate matter in the solution. do not shake the elaprase solution. withdraw the calculated volume of elaprase from the appropriate number of vials. add the calculated volume of elaprase solution to a 100 ml bag of 0.9% sodium chloride injection, usp for intravenous infusion. mix gently. do not shake the solution. 2.3 administration instructions administer the diluted elaprase solution to patients using a low-protein-binding infusion set equipped with a low-protein-binding 0.2 micrometer (µm) in-line filter. the total volume of infusion should be administered over a period of 3 hours, which may be gradually reduced to 1 hour if no hypersensitivity reactions are observed. patients may require longer infusion times if hypersensitivity reactions occur; however, infusion times should not exceed 8 hours. the initial infusion rate should be 8 ml per hour for the first 15 minutes. if the infusion is well tolerated, the rate of infusion may be increased by 8 ml per hour increments every 15 minutes. the infusion rate should not exceed 100 ml per hour. the infusion rate may be slowed, temporarily stopped, or discontinued for that visit in the event of hypersensitivity reactions [see warnings and precautions (5.1) ] . elaprase should not be infused with other products in the infusion tubing. 2.4 storage and stability elaprase does not contain preservatives; therefore, after dilution with saline, the infusion bags should be used immediately. if immediate use is not possible, the diluted solution should be stored refrigerated at 2°c to 8°c (36°f to 46 °f) for up to 24 hours. other than during infusion, do not store the diluted elaprase solution at room temperature. any unused product or waste material should be discarded and disposed of in accordance with local requirements.

the following serious adverse reactions are described below and elsewhere in the labeling: hypersensitivity reactions including anaphylaxis [see warnings and precautions (5.1) ] in clinical trials, the most common adverse reactions (>10%) following elaprase treatment were hypersensitivity reactions, and included rash, urticaria, pruritus, flushing, pyrexia, and headache. most hypersensitivity reactions requiring intervention were ameliorated with slowing of the infusion rate, temporarily stopping the infusion, with or without administering additional treatments including antihistamines, corticosteroids, or both prior to or during infusions. in clinical trials, the most frequent serious adverse reactions following elaprase treatment were hypoxic episodes. other notable serious adverse reactions that occurred in the elaprase-treated patients but not in the placebo-treated patients included one case each of: cardiac arrhythmia, pulmonary embolism, cyanosis, respiratory failure, infection, and arthralgia. clinical trials in patients 5 years and older a 53-week, double-blind, placebo-controlled clinical trial of elaprase was conducted in 96 male patients with hunter syndrome, ages 5-31 years old. of the 96 patients, 83% were white, non-hispanic. patients were randomized to three treatment groups, each with 32 patients: elaprase 0.5 mg/kg once weekly, elaprase 0.5 mg/kg every other week, or placebo. hypersensitivity reactions were reported in 69% (22 of 32) of patients who received once-weekly treatment of elaprase. table 1 summarizes the adverse reactions that occurred in at least 9% of patients (≥3 patients) in the elaprase 0.5 mg/kg once weekly group and with a higher incidence than in the placebo group. table 1. adverse reactions that occurred in the placebo-controlled trial 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 (5 years and older) system organ class adverse reaction elaprase (0.5 mg/kg weekly) n=32 n (%) placebo n=32 n (%) gastrointestinal disorder diarrhea 3 (9%) 1 (3%) musculoskeletal and connective tissue disorders musculoskeletal pain 4 (13%) 1 (3%) nervous system disorders headache 9 (28%) 8 (25%) respiratory, thoracic and mediastinal disorders cough 3 (9%) 1 (3%) skin and subcutaneous tissue disorders pruritus 8 (25%) 3 (9%) urticaria 5 (16%) 0 (0%) 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%), tachycardia (9%), and chills (9%). extension trial an open-label extension trial was conducted in patients who completed the placebo-controlled trial. ninety-four of the 96 patients who were enrolled in the placebo-controlled trial consented to participate in the extension trial. all 94 patients received elaprase 0.5 mg/kg once weekly for 24 months. no new serious adverse reactions were reported. approximately half (53%) of patients experienced hypersensitivity reactions during the 24-month extension trial. in addition to the adverse reactions listed in table 1, common hypersensitivity reactions occurring in at least 5% of patients (≥5 patients) in the extension trial included: rash (23%), pyrexia (9%), flushing (7%), erythema (7%), nausea (5%), dizziness (5%), vomiting (5%), and hypotension (5%). clinical trial in patients 7 years and younger a 53-week, open-label, single-arm, safety trial of once weekly elaprase 0.5 mg/kg treatment was conducted in patients with hunter syndrome, ages 16 months to 4 years old (n=20) and ages 5 to 7.5 years old (n=8) at enrollment. patients experienced similar adverse reactions as those observed in clinical trials in patients 5 years and older, with the most common adverse reactions following elaprase treatment being hypersensitivity reactions (57%). a higher incidence of the following common hypersensitivity reactions were reported in this younger age group: pyrexia (36%), rash (32%), and vomiting (14%). the most common serious adverse reactions occurring in at least 10% of patients (≥3 patients) included: bronchopneumonia/pneumonia (18%), ear infection (11%), and pyrexia (11%). twenty-seven patients had results of genotype analysis: 15 patients had complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations and 12 patients had missense mutations. safety results demonstrated that patients with complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations are more likely to experience hypersensitivity reactions and have serious adverse reactions following elaprase administration, compared to patients with missense mutations. table 2 summarizes these findings. table 2. impact of antibody status and genetic mutations on occurrence of serious adverse reactions and hypersensitivity in patients 7 years and younger treated with elaprase anti-idursulfase antibodies (ab) anti-idursulfase neutralizing antibodies (nab) total positive negative positive negative antibody status reported (patients) 28 19 9 15 13 serious adverse reactions serious adverse reactions included: bronchopneumonia/pneumonia, ear infection, and pyrexia [see adverse reactions (6.1) ] . (patients) 13 11 2 9 4 hypersensitivity (patients) 16 12 4 10 6 patients with genotype data 27 m u t a t i o n s missense mutation (n=12) antibody status 12 3 9 1 11 serious adverse reactions 2 0 2 0 2 hypersensitivity reactions 5 1 4 0 5 complete gene deletion, large gene rearrangement, nonsense, frameshift, splice site mutations (n=15) antibody status 15 15 0 13 2 serious adverse reactions 9 9 0 7 2 hypersensitivity reactions 11 11 0 10 1 6.2 immunogenicity clinical trials in patients 5 years and older as with all therapeutic proteins, there is potential for immunogenicity. in clinical trials in patients 5 years and older, 63 of the 64 patients treated with elaprase 0.5 mg/kg once weekly or placebo for 53 weeks, followed by elaprase 0.5 mg/kg once weekly in the extension trial, had immunogenicity data available for analysis. of the 63 patients, 32 (51%) patients tested positive for anti-idursulfase igg antibodies (ab) at least one time (table 2). of the 32 ab-positive patients, 23 (72%) tested positive for ab at three or more different time points (persistent ab). the incidence of hypersensitivity reactions was higher in patients who tested positive for ab than those who tested negative. thirteen of 32 (41%) ab-positive patients also tested positive for antibodies that neutralize idursulfase uptake into cells (uptake neutralizing antibodies, uptake nab) or enzymatic activity (activity nab) at least one time, and 8 (25%) of ab-positive patients had persistent nab. there was no clear relationship between the presence of either ab or nab and therapeutic response. clinical trial in patients 7 years and younger in the clinical trial in patients 7 years and younger, 19 of 28 (68%) patients treated with elaprase 0.5 mg/kg once weekly tested ab-positive. of the 19 ab-positive patients, 16 (84%) tested positive for ab at three or more different time points (persistent ab). in addition, 15 of 19 (79%) ab-positive patients tested positive for nab, with 14 of 15 (93%) nab-positive patients having persistent nab. all 15 patients with complete gene deletion, large gene rearrangement, nonsense, frameshift, or splice site mutations tested positive for ab (table 2). of these 15 patients, neutralizing antibodies were observed in 13 (87%) patients. the nabs in these patients developed earlier (most reported to be positive at week 9 rather than at week 27, as reported in clinical trials in patients older than 5 years of age) and were associated with higher titers and greater in vitro neutralizing activity than in patients older than 5 years of age. the presence of ab was associated with reduced systemic idursulfase exposure [see clinical pharmacology (12.3) ] . the immunogenicity data reflect the percentage of patients whose test results were positive for antibodies to idursulfase in specific assays, and are highly dependent on the sensitivity and specificity of these assays. the observed incidence of positive antibody in an assay may be influenced by several factors, including sample handling, timing of sample collection, concomitant medication, and underlying disease. for these reasons, comparison of the incidence of antibodies to idursulfase with the incidence of antibodies to other products may be misleading. 6.3 postmarketing experience the following adverse reactions have been identified during post-approval use of elaprase. because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. in post-marketing experience, 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 [see warnings and precautions (5.1) ] . a seven year-old male patient with hunter syndrome, who received elaprase at twice the recommended dosage (1 mg/kg weekly) for 1.5 years, experienced two anaphylactic events after 4.5 years of treatment. treatment has been withdrawn [see overdosage (10) ] . serious adverse reactions that resulted in death included cardiorespiratory arrest, respiratory failure, respiratory distress, cardiac failure, and pneumonia.

n clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively. data animal data in a pre- and post-natal development study, idursulfase was administered to pregnant rats twice weekly, intravenously, from gestation day 6 through lactation day 19. no significant adverse effects on pre- and post-natal development of the offspring were observed at twice weekly intravenous doses up to 12.5 mg/kg (about 4 times the recommended human weekly dose of 0.5 mg/kg based on body surface area). 8.2 lactation risk summary there are no data on the presence of idursulfase in human milk, the effects on the breastfed infant, or the effects on milk production. idursulfase was excreted in breast milk of lactating rats ( see data ). when a drug is present in animal milk, it is likely that the drug will be present in human milk. the developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for elaprase and any potential adverse effects on the breastfed child from elaprase or from the underlying maternal condition. data idursulfase was excreted in breast milk of lactating rats at a concentration higher (4- to 5-fold) than the maximum blood concentration, when administered as a single intravenous dose up to 2.5 mg/kg. the concentration of drug in animal milk does not necessarily predict the concentration of drug in human milk. 8.4 pediatric use clinical trials with elaprase were conducted in 96 patients with hunter syndrome, ages 5 to 31 years old, with the majority of the patients in the pediatric age group (median age 15 years old). in addition, an open-label, uncontrolled clinical trial was conducted in 28 patients with hunter syndrome, ages 16 months to 7.5 years old. patients 16 months to 5 years of age demonstrated reduction in spleen volume that was similar to that of adults and children 5 years and older. however, there are no data to support improvement in disease-related symptoms or long term clinical outcome in patients 16 months to 5 years of age [see clinical studies (14) ] . the safety and effectiveness of elaprase have not been established in pediatric patients less than 16 months of age. 8.5 geriatric use clinical studies of elaprase did not include patients older than 31 years of age. it is not known whether older patients respond differently from younger patients.

ncies is 2% to 4% and 15% to 20%, respectively. data animal data in a pre- and post-natal development study, idursulfase was administered to pregnant rats twice weekly, intravenously, from gestation day 6 through lactation day 19. no significant adverse effects on pre- and post-natal development of the offspring were observed at twice weekly intravenous doses up to 12.5 mg/kg (about 4 times the recommended human weekly dose of 0.5 mg/kg based on body surface area).

levels were observed following treatment with elaprase. the responsiveness of urinary gag to dosage alterations of elaprase is unknown, and the relationship of urinary gag to other measures of clinical response has not been established. patients who tested positive for anti-idursulfase antibodies (ab) experienced a less pronounced decrease in urinary gag levels [see adverse reactions (6.2) and clinical studies (14.1 , 14.2) ] . 12.3 pharmacokinetics clinical trials in patients 5 years and older the pharmacokinetic characteristics of idursulfase were evaluated in 59 patients with hunter syndrome. the serum concentration of idursulfase was quantified using an antigen-specific elisa assay. the area under the concentration-time curve (auc) increased in a greater than dose proportional manner as the dose increased from 0.15 mg/kg to 1.5 mg/kg following a single 1-hour infusion of elaprase. the pharmacokinetic parameters at the recommended dose regimen (0.5 mg/kg elaprase administered weekly as a 3-hour infusion) were determined at week 1 and week 27 in 10 patients 7.7 to 27 years of age (table 3). there were no apparent differences in pk parameter values between week 1 and week 27 regardless of the antibody status in these patients. table 3. pharmacokinetic parameters in patients 7.7 to 27 years of age pharmacokinetic parameter week 1 mean (sd) week 27 mean (sd) c max (mcg/ml) 1.5 (0.6) 1.1 (0.3) auc (min•mcg/ml) 206 (87) 169 (55) t 1/2 (min) 44 (19) 48 (21) cl (ml/min/kg) 3.0 (1.2) 3.4 (1.0) v ss (ml/kg) 213 (82) 254 (87) clinical trial in patients 7 years and younger idursulfase pharmacokinetics was evaluated in 27 patients with hunter syndrome 16 months to 7.5 years of age who received elaprase 0.5 mg/kg once weekly as a 3-hour infusion. the presence of anti-idursulfase antibody (ab) was associated with a reduced systemic exposure of idursulfase. eight of the 18 ab-positive patients had no measurable idursulfase concentrations. an additional 9 ab-positive patients had decreased c max , auc, and t 1/2 at week 27 compared to week 1 (table 4). idursulfase pharmacokinetics was similar between week 1 and week 27 in ab-negative patients (table 4). table 4. pharmacokinetic parameters in patients 16 months to 7.5 years of age week 1 week 27 pharmacokinetic parameter (n=27) all patients mean (sd) anti-idursulfase antibodies (ab) positive anti-idursulfase antibody (ab) is defined as having at least one serum specimen with measurable antibody during study duration. (n=9) negative ab mean (sd) (n=10 eight of 18 patients with positive ab had no measurable concentrations at week 27. ) positive ab mean (sd) c max (mcg/ml) 1.33 (0.817) 1.40 (0.389) 0.706 (0.558) auc (min•mcg/ml) 224 (76.9) n=26 281 (81.8) 122 (92.1) n=9 t 1/2 (min) 160 (69) 134 (19) 84 (46) cl (ml/min/kg) 2.4 (0.7) 2.0 (0. 8) 7.4 (6.0) v ss (ml/kg) 394 (423) 272 (112) 829 (636) all patients with the complete gene deletion or large gene rearrangement genotype (n=8) developed ab at week 27. five of these eight patients had no measurable idursulfase concentrations at week 27, and three had a lower systemic exposure at week 27 compared to week 1.

/ml) 206 (87) 169 (55) t 1/2 (min) 44 (19) 48 (21) cl (ml/min/kg) 3.0 (1.2) 3.4 (1.0) v ss (ml/kg) 213 (82) 254 (87) clinical trial in patients 7 years and younger idursulfase pharmacokinetics was evaluated in 27 patients with hunter syndrome 16 months to 7.5 years of age who received elaprase 0.5 mg/kg once weekly as a 3-hour infusion. the presence of anti-idursulfase antibody (ab) was associated with a reduced systemic exposure of idursulfase. eight of the 18 ab-positive patients had no measurable idursulfase concentrations. an additional 9 ab-positive patients had decreased c max , auc, and t 1/2 at week 27 compared to week 1 (table 4). idursulfase pharmacokinetics was similar between week 1 and week 27 in ab-negative patients (table 4). table 4. pharmacokinetic parameters in patients 16 months to 7.5 years of age week 1 week 27 pharmacokinetic parameter (n=27) all patients mean (sd) anti-idursulfase antibodies (ab) positive anti-idursulfase antibody (ab) is defined as having at least one serum specimen with measurable antibody during study duration. (n=9) negative ab mean (sd) (n=10 eight of 18 patients with positive ab had no measurable concentrations at week 27. ) positive ab mean (sd) c max (mcg/ml) 1.33 (0.817) 1.40 (0.389) 0.706 (0.558) auc (min•mcg/ml) 224 (76.9) n=26 281 (81.8) 122 (92.1) n=9 t 1/2 (min) 160 (69) 134 (19) 84 (46) cl (ml/min/kg) 2.4 (0.7) 2.0 (0. 8) 7.4 (6.0) v ss (ml/kg) 394 (423) 272 (112) 829 (636) all patients with the complete gene deletion or large gene rearrangement genotype (n=8) developed ab at week 27. five of these eight patients had no measurable idursulfase concentrations at week 27, and three had a lower systemic exposure at week 27 compared to week 1.

eekly treatment group (once weekly elaprase vs. placebo, p=0.0049). examination of the individual components of the composite score showed that, in the adjusted analysis, the weekly elaprase-treated group experienced a 35 meter greater mean increase in the distance walked in six minutes compared to placebo. the changes in %-predicted fvc were not statistically significant (table 5). table 5. clinical trial results elaprase weekly n=32 one patient in the placebo group and one patient in the elaprase group died before week 53; imputation was by last observation carried forward in the intent-to-treat analysis. placebo n=32 elaprase once weekly – placebo baseline week 53 change change, calculated as week 53 minus baseline baseline week 53 change difference in change results from the 6-minute walk test (meters) mean ± sd 392 ± 108 436 ± 138 44 ± 70 393 ± 106 400 ± 106 7 ± 54 37 ± 16 observed mean ± se 35 ± 14 ancova model based mean ± se, adjusted for baseline disease severity, region, and age. (p=0.01) median 397 429 31 403 412 -4 percentiles (25 th , 75 th ) 316, 488 365, 536 0, 94 341, 469 361, 460 -30, 31 results from the forced vital capacity test (% of predicted) mean ± sd 55.3 ± 15.9 58.7 ± 19.3 3.4 ± 10.0 55.6 ± 12.3 56.3 ± 15.7 0.8 ± 9.6 2.7 ± 2.5 4.3 ± 2.3 (p=0.07) median 54.9 59.2 2.1 57.4 54.6 -2.5 percentiles (25 th , 75 th ) 43.6, 69.3 44.4, 70.7 -0.8, 9.5 46.9, 64.4 43.8, 67.5 -5.4, 5.0 pharmacodynamic assessments included urinary gag levels and changes in liver and spleen size. urinary gag levels were elevated in all patients at baseline. following 53 weeks of treatment, mean urinary gag levels were reduced in the elaprase once weekly group, although gag levels still remained above the upper limit of normal in half of the elaprase-treated patients. urinary gag levels remained elevated and essentially unchanged in the placebo group. sustained reductions in both liver and spleen volumes were observed in the elaprase once weekly group through week 53 compared to placebo. there were essentially no changes in liver and spleen volumes in the placebo group. extension trial patients who participated in the placebo-controlled trial were eligible to continue treatment in an open-label extension trial. during the extension trial, all patients received elaprase 0.5mg/kg once weekly for 24 months. patients who were treated with elaprase once weekly and every other week in the placebo-controlled trial demonstrated improvement in distance walked in the 6-minute walk test for an additional 8 months of treatment in the extension trial. there was no change in mean %-predicted fvc in all hunter syndrome patients after 6 months of treatment in the extension trial; however, a slight decrease in mean %-predicted fvc was demonstrated through to month 24 of the extension trial. the long-term effect of elaprase on pulmonary function in hunter syndrome patients is unclear. there were no further reductions in mean urinary gag levels in patients initially treated with elaprase once weekly; however, the patients treated with elaprase every other week during the placebo-controlled trial experienced further reductions in mean urinary gag levels after changing to a more frequent dosing regimen during the extension trial. the persistence of reduced urinary gag levels did not correlate with the long term effect demonstrated by the 6-minute walk test distance or %-predicted fvc. 14.2 clinical trial in patients 7 years and younger a 53-week, open-label, multicenter, single-arm trial was conducted to assess the safety, pharmacokinetics, and pharmacodynamics of elaprase 0.5 mg/kg once weekly in male hunter syndrome patients aged 7 years and younger. safety results demonstrated that patients with complete gene deletion or large gene rearrangement mutations are more likely to develop antibodies, including neutralizing antibodies, and to experience hypersensitivity reactions with elaprase administration [see adverse reactions (6.1 , 6.2) ] . in patients who remained antibody negative, the pharmacokinetic profile, reduction in urinary gag excretion levels, and reduction in spleen volume were similar to those of adults and children 5 years and older. in patients who were persistently antibody positive, the presence of anti-idursulfase antibody was associated with reduced systemic exposure of idursulfase and a less pronounced decrease in urinary gag levels [see clinical pharmacology (12.2 , 12.3) ] .