HEMLIBRA restores the tenase cofactor activity of missing activated factor VIII (FVIIIa). Coagulation laboratory tests based on intrinsic clotting (i.e., aPTT) measure the total clotting time including time needed for activation of FVIII to FVIIIa by thrombin. Such intrinsic pathway-based tests will yield overly shortened clotting times with HEMLIBRA, which does not require activation by thrombin. The overly shortened intrinsic clotting time will then disturb all single-factor assays based on aPTT, such as the one-stage FVIII activity assay; however, single-factor assays utilizing chromogenic or immuno-based methods are unaffected by HEMLIBRA and may be used to monitor coagulation parameters during treatment, with specific considerations for FVIII chromogenic activity assays as described below.
Chromogenic FVIII activity tests may be manufactured with either human or bovine coagulation proteins. Assays containing human coagulation factors are responsive to HEMLIBRA but may overestimate the clinical hemostatic potential of HEMLIBRA. In contrast, assays containing bovine coagulation factors are insensitive to HEMLIBRA (no activity measured) and can be used to monitor endogenous or infused FVIII activity, or to measure anti-FVIII inhibitors.
HEMLIBRA remains active in the presence of inhibitors against FVIII, so it will produce a false-negative result in clotting-based Bethesda assays for functional inhibition of FVIII. Instead, a chromogenic Bethesda assay utilizing a bovine-based FVIII chromogenic test that is insensitive to HEMLIBRA may be used.
Due to the long half-life of HEMLIBRA, effects on coagulation assays may persist for up to 6 months after the last dose [see Clinical Pharmacology (12.3)].
There are no available data on HEMLIBRA use in pregnant women to inform a drug-associated risk of major birth defects and miscarriage. Animal reproduction studies have not been conducted with emicizumab-kxwh. It is not known whether HEMLIBRA can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. HEMLIBRA should be used during pregnancy only if the potential benefit for the mother outweighs the risk to the fetus.
All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. The estimated background risk of major birth defects and miscarriage for the indicated populations is unknown. In the U.S. general population, the estimated background risk of major birth defect and miscarriage in clinically recognized pregnancies is 2 – 4% and 15 – 20%, respectively.
There is no information regarding the presence of emicizumab-kxwh in human milk, the effects on the breastfed child, or the effects on milk production. Human IgG is known to be present in human milk. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for HEMLIBRA and any potential adverse effects on the breastfed child from HEMLIBRA or from the underlying maternal condition.
Women of childbearing potential should use contraception while receiving HEMLIBRA.
The safety and efficacy of HEMLIBRA have been established in pediatric patients. Use of HEMLIBRA in pediatric patients with hemophilia A is supported by two randomized trials (HAVEN 1 and HAVEN 3) and two single-arm trials (HAVEN 2 and HAVEN 4). All clinical trials included pediatric patients in the following age group: 47 adolescents (12 years up to less than 18 years). Only HAVEN 2 included pediatric patients in the following age groups: 55 children (2 years up to less than 12 years) and five infants (1 month up to less than 2 years). No differences in efficacy were observed between the different age groups [see Clinical Studies (14)].
The steady-state plasma trough concentrations of emicizumab-kxwh were comparable in adult and pediatric patients older than 6 months at equivalent weight-based doses. Lower concentrations of emicizumab-kxwh were predicted in pediatric patients less than 6 months old [see Clinical Pharmacology (12.3)].
In general, the adverse reactions in HEMLIBRA-treated pediatric patients were similar in type to those seen in adult patients with hemophilia A [see Adverse Reactions (6.1)].
Clinical studies of HEMLIBRA did not include a sufficient number of patients aged 65 and over to determine whether they respond differently from younger patients. Other reported clinical experience has not identified differences in responses between the elderly and younger patients.
Emicizumab-kxwh is a humanized monoclonal modified immunoglobulin G4 (IgG4) bispecific antibody binding factor IXa and factor X. Emicizumab-kxwh has an approximate molecular weight of 145.6 kDa and is produced in genetically engineered mammalian (Chinese hamster ovary) cells. Emicizumab-kxwh has no structural relationship or sequence homology to FVIII and, as such, does not induce or enhance the development of direct inhibitors to FVIII.
HEMLIBRA (emicizumab-kxwh) injection is a sterile, preservative-free, colorless to slightly yellow solution for subcutaneous injection supplied in single-dose vials containing emicizumab-kxwh at 30 mg/mL, 60 mg/0.4 mL, 105 mg/0.7 mL, or 150 mg/mL.
Each single-dose 30 mg vial contains a 1 mL solution of emicizumab-kxwh (30 mg), L-arginine (26.1 mg), L-histidine (3.1 mg), and poloxamer 188 (0.5 mg), adjusted to pH 6.0 with L-aspartic acid.
Each single-dose 60 mg vial contains a 0.4 mL solution of emicizumab-kxwh (60 mg), L-arginine (10.5 mg), L-histidine (1.2 mg), and poloxamer 188 (0.2 mg), adjusted to pH 6.0 with L-aspartic acid.
Each single-dose 105 mg vial contains a 0.7 mL solution of emicizumab-kxwh (105 mg), L-arginine (18.3 mg), L-histidine (2.2 mg), and poloxamer 188 (0.4 mg), adjusted to pH 6.0 with L-aspartic acid.
Each single-dose 150 mg vial contains a 1 mL solution of emicizumab-kxwh (150 mg), L-arginine (26.1 mg), L-histidine (3.1 mg), and poloxamer 188 (0.5 mg), adjusted to pH 6.0 with L-aspartic acid.
HEMLIBRA bridges activated factor IX and factor X to restore the function of missing activated factor VIII that is needed for effective hemostasis.
Emicizumab-kxwh exhibited dose-proportional pharmacokinetics over a dose range of 0.3 mg/kg (0.1 times approved recommended starting dosage) to 6 mg/kg following subcutaneous administration. Following multiple subcutaneous administrations of a loading dose of 3 mg/kg emicizumab-kxwh once weekly for the first 4 weeks in hemophilia A patients, mean (± SD) trough plasma concentrations of 52.6 ± 13.6 μg/mL was achieved at Week 5. Sustained mean (± SD) plasma concentrations of emicizumab-kxwh at steady-state with the recommended maintenance doses are shown in Table 4.
|Parameters||1.5 mg/kg once every week||3 mg/kg once every two weeks||6 mg/kg once every four weeks|
|AUCss ,τ = area under the concentration time curve at steady-state over the dosing interval (τ = 1, 2, or 4 weeks); Cmax, ss = maximum plasma concentration at steady state; Ctrough, ss = trough concentration at steady state.|
|Cmax, ss (µg/mL)||55.1 ± 15.9||58.3 ± 16.4||67 ± 17.7|
|AUCss,τ (µg/mL*day)||376 ± 109||752 ± 218||1503 ± 437|
|Ctrough, ss (µg/mL)||51.2± 15.2||46.9 ± 14.8||38.5 ± 14.2|
|Cmax / Ctrough ratio (µg/mL)||1.08 ± 0.03||1.26 ± 0.12||1.85 ± 0.47|
Following subcutaneous administration, the mean (± SD) absorption half-life was 1.6 ± 1 day.
The absolute bioavailability following subcutaneous administration of 1 mg/kg was between 80.4% and 93.1%. Similar pharmacokinetic profiles were observed following subcutaneous administration in the abdomen, upper arm, and thigh [see Dosage and Administration (2.2)].
The mean apparent volume of distribution (% coefficient of variation [%CV]) was 10.4 L (26.0%).
The mean apparent clearance (%CV) was 0.27 L/day (28.4%) and the mean elimination apparent half-life (± SD) was 26.9 ± 9.1 days.
The pharmacokinetics of emicizumab-kxwh are not influenced by age (1 year to 77 years), race (White 62.7%, Asian 22.9%, and Black 8%), inhibitor status (inhibitor present, 50%), mild hepatic impairment (defined as total bilirubin 1× to ≤ 1.5× the upper limit of normal (ULN) and any aspartate transaminase (AST) level), moderate hepatic impairment (defined as total bilirubin 1.5× to ≤ 3× the ULN and any AST level), mild renal impairment (defined as creatinine clearance (CrCl) of 60 – 89 mL/min), and moderate renal impairment (defined as CrCl of 30 – 59 mL/min). Emicizumab-kxwh has not been studied in patients with severe hepatic or renal impairment.
In pediatric patients less than 6 months old, the predicted concentrations of emicizumab-kxwh were 19% to 33% lower than the older patients, especially with the 3 mg/kg once every two weeks or 6 mg/kg once every four weeks maintenance dose.
Body weight: The apparent clearance and volume of distribution of emicizumab-kxwh increased with increasing body weight (9 kg to 156 kg). Dosing in mg/kg provides similar emicizumab-kxwh exposure across body weight range.
Drug Interaction Studies
No drug-drug interaction studies have been conducted with HEMLIBRA.
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