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 |
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.
Risk Summary
There are no adequate and well-controlled studies with ELAPRASE use in pregnant women. Available data from a small number of postmarketing cases with ELAPRASE use in pregnancy are insufficient to inform drug-associated risks for major birth defects, miscarriage, or adverse maternal or fetal outcomes. In an animal reproduction study, no evidence of adverse effects on pre- and post-natal development was observed with twice weekly intravenous administration of idursulfase to pregnant rats from gestation day 6 through lactation day 19 at about 4 times the recommended human weekly dose of 0.5 mg/kg based on body surface area (see Data).
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in 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).
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.
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) |
|---|
| Cmax (mcg/mL) | 1.5 (0.6) | 1.1 (0.3) |
| AUC (min•mcg/mL) | 206 (87) | 169 (55) |
| t1/2 (min) | 44 (19) | 48 (21) |
| CL (mL/min/kg) | 3.0 (1.2) | 3.4 (1.0) |
| Vss (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 Cmax, AUC, and t1/2 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) |
|---|
| Cmax (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 |
| t1/2 (min) | 160 (69) | 134 (19) | 84 (46) |
| CL (mL/min/kg) | 2.4 (0.7) | 2.0 (0. 8) | 7.4 (6.0) |
| Vss (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.
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.
Information for Patients
Patients should be advised that life-threatening anaphylactic reactions have occurred in some patients during and up to 24 hours after ELAPRASE therapy. Patients who have experienced anaphylactic reactions may require prolonged observation. Patients with compromised respiratory function or acute respiratory disease may be at risk of serious acute exacerbation of their respiratory compromise due to hypersensitivity reactions.
A Hunter Outcome Survey has been established in order to understand better the variability and progression of Hunter syndrome (MPS II) in the population as a whole, and to monitor and evaluate long-term treatment effects of ELAPRASE. Patients and their physicians are encouraged to participate in this program. For more information, call Takeda Pharmaceuticals at 1-877-825-3327.
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