Ecallantide

KALBITOR ® (ecallantide) is indicated for treatment of acute attacks of hereditary angioedema (HAE) in patients 12 years of age and older. KALBITOR is a plasma kallikrein inhibitor indicated for treatment of acute attacks of hereditary angioedema (HAE) in patients 12 years of age and older. ( 1 )

KALBITOR is a clear, colorless liquid free of preservatives. Each vial of KALBITOR contains ecallantide at a concentration of 10 mg/mL. Single-dose glass vial containing 10 mg/mL of ecallantide as a solution for injection. ( 3 )

Do not administer KALBITOR to a patient who has known clinical hypersensitivity to KALBITOR. [ see Warnings and Precautions (5.1) ]. Do not administer KALBITOR to a patient who has known clinical hypersensitivity to KALBITOR. ( 4 )

Hypersensitivity Reactions Including Anaphylaxis: Anaphylaxis has occurred in 4% of treated patients. Administer KALBITOR in a setting equipped to manage anaphylaxis and hereditary angioedema. Given the similarity in hypersensitivity symptoms and acute HAE symptoms, monitor patients closely for hypersensitivity reactions ( 5 ).

5.1 Hypersensitivity Reactions, Including Anaphylaxis Potentially serious hypersensitivity reactions, including anaphylaxis, have occurred in patients treated with KALBITOR. In 255 HAE patients treated with intravenous or subcutaneous KALBITOR in clinical studies, 10 patients (4%) experienced anaphylaxis. For the subgroup of 187 patients treated with subcutaneous KALBITOR, 5 patients (3%) experienced anaphylaxis. Symptoms associated with these reactions have included chest discomfort, flushing, pharyngeal edema, pruritus, rhinorrhea, sneezing, nasal congestion, throat irritation, urticaria, wheezing, and hypotension. These reactions occurred within the first hour after dosing. Other adverse reactions indicative of hypersensitivity reactions included the following: pruritus (5%), rash (3%), and urticaria (2%). Patients should be observed for an appropriate period of time after administration of KALBITOR, taking into account the time to onset of anaphylaxis seen in clinical trials. Given the similarity in hypersensitivity symptoms and acute HAE symptoms, patients should be monitored closely in the event of a hypersensitivity reaction. KALBITOR should not be administered to any patients with known clinical hypersensitivity to KALBITOR [ see Contraindications (4) ] .

Hypersensitivity reactions, including anaphylaxis, have occurred in patients treated with KALBITOR [ see Contraindications (4) and Warnings and Precautions (5.1) ]. The most common adverse reactions occurring in ≥3% of KALBITOR-treated patients and greater than placebo are headache, nausea, diarrhea, pyrexia, injection site reactions, and nasopharyngitis. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Takeda Pharmaceuticals U.S.A., Inc. at 1-877-TAKEDA-7 (1-877-825-3327) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The safety data described below reflect exposure to KALBITOR in 255 patients with HAE treated with either intravenous or subcutaneous KALBITOR. Of the 255 patients, 66% of patients were female and 86% were Caucasian. Patients treated with KALBITOR were between the ages of 10 and 78 years. Overall, the most common adverse reactions in 255 patients with HAE were headache (16%), nausea (13%), fatigue (12%), diarrhea (11%), upper respiratory tract infection (8%), injection site reactions (7%), nasopharyngitis (6%), vomiting (6%), pruritus (5%), upper abdominal pain (5%), and pyrexia (5%). Anaphylaxis was reported in 4% of patients with HAE. Injection site reactions were characterized by local pruritus, erythema, pain, irritation, urticaria, and/or bruising. The incidence of adverse reactions below is based upon 2 placebo-controlled, clinical trials (EDEMA3 ® and EDEMA4) in a total of 143 unique patients with HAE. Patients were treated with KALBITOR 30 mg subcutaneous or placebo. Patients were permitted to participate sequentially in both placebo-controlled trials; safety data collected during exposure to KALBITOR was attributed to treatment with KALBITOR, and safety data collected during exposure to placebo was attributed to treatment with placebo. Table 1 shows adverse reactions occurring in ≥3% of KALBITOR-treated patients that also occurred at a higher rate than in the placebo-treated patients in the two controlled trials (EDEMA3 and EDEMA4) of the 30 mg subcutaneous dose. Table 1: Adverse Reactions Occurring at ≥3% and Higher than Placebo in 2 Placebo Controlled Clinical Trials in Patients with HAE Treated with KALBITOR KALBITOR N=100 Placebo N=81 Adverse Reactions n (%) Patients experiencing more than 1 event with the same preferred term are counted only once for that preferred term. n (%) Headache 8 (8%) 6 (7%) Nausea 5 (5%) 1 (1%) Diarrhea 4 (4%) 3 (4%) Pyrexia 4 (4%) 0 Injection site reactions 3 (3%) 1 (1%) Nasopharyngitis 3 (3%) 0 Some patients in EDEMA3 and EDEMA4 received a second, open-label 30 mg subcutaneous dose of KALBITOR within 24 hours following the initial dose. Adverse reactions reported by these patients who received the additional 30 mg subcutaneous dose of KALBITOR were consistent with those reported in the patients receiving a single dose.

6.2 Immunogenicity In the KALBITOR HAE program, patients developed antibodies to KALBITOR. Rates of seroconversion increased with exposure to KALBITOR over time. Overall, 20.2% of patients seroconverted to anti-ecallantide antibodies. Neutralizing antibodies to ecallantide were determined in vitro to be present in 8.8% of patients and were not associated with loss of efficacy. Anti-ecallantide IgE antibodies were detected at a rate of 4.7% for tested patients, and anti- P. pastoris IgE antibodies were also detected at a rate of 20.2%. Patients who seroconvert may be at a higher risk of a hypersensitivity reaction. The long-term effects of antibodies to KALBITOR are not known. The test results for the ecallantide program were determined using one of two assay formats: ELISA and bridging electrochemiluminescence (ECL). As with all therapeutic proteins, there is a potential for immunogenicity with the use of KALBITOR. The incidence of antibody formation is highly dependent on the sensitivity and specificity of the assay. Additionally, the observed incidence of antibody (including neutralizing antibody) positivity in an assay may be influenced by several factors, including assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease. For these reasons, comparison of the incidence of antibodies to KALBITOR with the incidence of antibodies to other products may be misleading.

6.3 Postmarketing Experience Similar adverse reactions have been observed postmarketing as described for clinical trial experience. Because these events are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate frequency or to establish a causal relationship with drug exposure.

No formal drug interactions studies were performed. No in vitro metabolism studies were performed.

8.1 Pregnancy Risk Summary The available data from the pharmacovigilance database for KALBITOR have not identified a drug-associated risk of major birth defects, miscarriage or adverse maternal or fetal outcomes. In an animal reproduction study, increased early fetal deaths resulting in decreased live fetuses were observed in rats following treatment during the period of organogenesis at an intravenous dose approximately 1.6 times the maximum recommended human dose (MRHD) in the presence of maternal toxicity. There were no effects on embryofetal survival or structural abnormalities in rats and rabbits following treatment during the period of organogenesis with intravenous doses up to approximately 1.1 and 6 times the MRHD, respectively, or rats treated with subcutaneous doses up to 2.4 times the MRHD. In a pre- and post-natal development study with rats, there were no effects on pup survival and development with subcutaneous doses up to approximately 2.7 times the MRHD. 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 an embryofetal development study with rats, ecallantide administered by the intravenous route during the period of organogenesis from gestation days 7 to 17 at a dose approximately 1.6 times the MRHD (on a mg/m 2 basis at a maternal intravenous dose of 15 mg/kg/day) caused increased numbers of early resorptions and percentages of resorbed conceptuses per litter resulting in decreased numbers of live fetuses in the presence of mild maternal toxicity. No effects on embryofetal survival or structural abnormalities were observed in rats with intravenous doses up to approximately 1.1 times the MRHD (on a mg/m 2 basis with maternal intravenous dose of 10 mg/kg/day). In an embryofetal development study with rats, ecallantide administered by the subcutaneous route during the period of organogenesis from gestation days 7 to 17 at doses up to approximately 2.4 times the MRHD (on an AUC basis with maternal subcutaneous doses up to 20 mg/kg/day) had no effects on embryofetal survival or structural abnormalities. In an embryofetal development study with rabbits, ecallantide administered by the intravenous route during the period of organogenesis from gestation days 7 to 19 at doses up to approximately 6 times the MRHD (on an AUC basis with maternal intravenous doses up to 5 mg/kg/day in rabbits) had no effects on embryofetal survival or structural abnormalities. In a pre- and post-natal development study with rats, ecallantide administered by the subcutaneous route from gestation day 7 through lactation day 20 at doses up to approximately 2.7 times the MRHD (on a mg/m 2 basis with maternal subcutaneous doses up to 25 mg/kg/day) had no effects on pup survival and behavioral or physical development.

8.2 Lactation Risk Summary There are no data on the presence of ecallantide in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for KALBITOR and any potential adverse effects on the breastfed child from KALBITOR or from the underlying maternal condition.

8.4 Pediatric Use The safety and effectiveness of KALBITOR have been established in patients 12 to 17 years of age. The efficacy of KALBITOR in the 12-15 year age group is extrapolated from efficacy in patients 16 years of age and older with support from population pharmacokinetic analyses showing similar drug exposure levels in adults and adolescents [see Clinical Pharmacology (12.3) and Clinical Studies (14) ] . The safety profile observed in pediatric patients 12-17 years of age was similar to the adverse reactions observed in the overall clinical trial population [see Adverse Reactions (6.1) ] . Safety and effectiveness of KALBITOR in patients less than 12 years of age have not been established.

8.5 Geriatric Use Clinical trials of KALBITOR did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Hereditary angioedema (HAE) is a rare genetic disorder caused by mutations to C1-esterase-inhibitor (C1-INH) located on Chromosome 11q and inherited as an autosomal dominant trait. HAE is characterized by low levels of C1-INH activity and low levels of C4. C1-INH functions to regulate the activation of the complement and intrinsic coagulation (contact system pathway) and is a major endogenous inhibitor of plasma kallikrein. The kallikrein-kinin system is a complex proteolytic cascade involved in the initiation of both inflammatory and coagulation pathways. One critical aspect of this pathway is the conversion of High Molecular Weight (HMW) kininogen to bradykinin by the protease plasma kallikrein. In HAE, normal regulation of plasma kallikrein activity and the classical complement cascade is therefore not present. During attacks, unregulated activity of plasma kallikrein results in excessive bradykinin generation. Bradykinin is a vasodilator which is thought by some to be responsible for the characteristic HAE symptoms of localized swelling, inflammation, and pain. KALBITOR is a potent (Ki = 25 pM), selective, reversible inhibitor of plasma kallikrein. KALBITOR binds to plasma kallikrein and blocks its binding site, inhibiting the conversion of HMW kininogen to bradykinin. By directly inhibiting plasma kallikrein, KALBITOR reduces the conversion of HMW kininogen to bradykinin and thereby treats symptoms of the disease during acute episodic attacks of HAE.