The following clinically important adverse reactions are described elsewhere in the labeling: Hypersensitivity and Anaphylaxis [see Warnings and Precautions ( 5.1 )]. Most frequently reported adverse reactions in healthy adult subjects (≥1.5%) were headache, pruritus, infections of the upper respiratory tract, cough, vessel puncture site bruise, infusion site swelling, nasal congestion, infusion site pain, urticaria and pain in extremity.
( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Elusys Therapeutics, Inc. at 1-844-808-0222 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
6.1Clinical 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 of ANTHIM has been studied only in healthy volunteers. It has not been studied in patients with inhalational anthrax. The safety of ANTHIM was evaluated in 320 healthy subjects treated with one or more 16 mg/kg IV doses in three clinical studies.
Study 1 was a placebo-controlled study evaluating a single dose of ANTHIM vs. placebo (210 subjects received ANTHIM, 70 received placebo). Study 2 was a repeat-dose study in which 70 subjects received the first dose, but 34 and 31 subjects received a second dose of ANTHIM in sequences A (2 weeks apart) and B (≥ 4 months apart), respectively. Study 3 was a drug interaction study of a single dose of ANTHIM with ciprofloxacin in 40 subjects (20 subjects received ANTHIM alone and 20 subjects received ANTHIM plus ciprofloxacin for 9 days).
Subjects were 18 to 79 years of age, 54% were male, 70% Caucasian, 26% Black/African American, 2% American Indian/Alaska Native, 1% Asian and 10% Hispanic. Adverse Reactions Leading to Discontinuation of ANTHIM Infusion ANTHIM infusion was discontinued in 8/320 healthy subjects (2.5%) in clinical trials due to hypersensitivity reactions or anaphylaxis [see Warnings and Precautions ( 5.1 )] . Most Frequently Reported Adverse Reactions The most frequently reported adverse reactions were headache, pruritus, infections of the upper respiratory tract, cough, vessel puncture site bruise, infusion site swelling, urticaria, nasal congestion, infusion site pain, and pain in extremity.
Table 3 shows the adverse reactions that occurred in ≥1.5% of healthy subjects receiving a single dose of ANTHIM (16 mg/kg IV) and more frequently than those receiving placebo. Table 3. Adverse Reactions Reported in ≥1.5% of Healthy Adult Subjects Exposed to a Single Dose of ANTHIM 16 mg/kg IV *Single-dose population: 210 subjects in study 1 plus 70 subjects in the first treatment period of study 2 plus 20 subjects in the ANTHIM alone treatment arm of study 3 Adverse Reactions Placebo N = 70 (%) Single Dose ANTHIM N = 300 * (%) Headache 4 (6%) 24 (8%) Pruritus 1 (1%) 11 (4%) Infections of the upper respiratory tract 2 (3%) 14 (5%) Cough 0 9 (3%) Vessel puncture site bruise 1 (1%) 8 (3%) Infusion site swelling 1 (1%) 8 (3%) Nasal congestion 1 (1%) 5 (2%) Infusion site pain 0 7 (2%) Urticaria 0 5 (2%) Pain in extremity 1 (1%) 5 (2%) Effect of Diphenhydramine on the Incidence of Adverse Reactions Overall in the single-dose population, subjects who received pre-medication with diphenhydramine were less likely to experience adverse reactions with administration of ANTHIM compared to those who did not (42% vs. 58% respectively).
Specifically, the incidence of the following adverse reactions was lower in the subjects who received diphenhydramine prior to ANTHIM infusion compared to those who did not: headache (5% vs. 16%), cough (1% vs. 8%), rash (2% vs. 7%), pruritus (3% vs. 4%) throat irritation (0 vs. 3%), rhinorrhea (0 vs. 3%), and infusion site erythema (0% vs. 4%). Somnolence was only reported in subjects who were pretreated with diphenhydramine.
Less Common Adverse Reactions Clinically important adverse reactions that were reported in <1.5% of subjects exposed to ANTHIM and at rates higher than in placebo subjects are listed below: General disorders and administration site conditions: chest discomfort/pain, fatigue, pyrexia, intravenous site discoloration Musculoskeletal and connective tissue disorders: myalgia, musculoskeletal pain Respiratory, thoracic and mediastinal disorders: oropharyngeal pain, sinus congestion, rhinorrhea, dysphonia, dyspnea Investigations: lymphocyte count decreased, neutrophil count decreased, white blood count decreased, increased creatine phosphokinase Cardiac disorders: palpitations, cyanosis Neurologic disorders: dizziness Gastrointestinal disorders: vomiting, dry mouth
6.2 Immunogenicity As with all therapeutic proteins, there is a potential for immunogenicity. The development of anti-ANTHIM antibodies was evaluated in all subjects receiving single and double doses of ANTHIM in studies 1, 2 and 3. Eight subjects (2.5%) who received at least one dose of IV ANTHIM were positive for a treatment-emergent anti-therapeutic antibody (ATA) response. Quantitative titers were low ranging from 1:20 – 1:320.
There was no evidence of altered PK or toxicity profile in subjects with ATA development. The incidence of antibody formation is highly dependent on the sensitivity and specificity of the immunogenicity assay. Additionally, the observed incidence of any antibody positivity in an assay is highly dependent on several factors, including assay sensitivity and specificity, assay methodology, sample handling, timing of sample collection, concomitant medications, and underlying disease.
For these reasons, comparison of incidence of antibodies to obiltoxaximab with the incidence of antibodies to other products may be misleading.
