General Information

Anthim (obiltoxaximab) is a monoclonal antibody that binds the PA of B. anthracis.

Anthim is specifically indicated for use in adult and pediatric patients for the treatment of inhalational anthrax due to Bacillus anthracis in combination with appropriate antibacterial drugs and for prophylaxis of inhalational anthrax due to B. anthracis when alternative therapies are not available or not appropriate.

Anthim is supplied as an injection for intravenous administration. The recommended dose is as follows:

Adults:

Pre-medicate with diphenhydramine prior to administering Anthim

Dilute the injection in 0.9% Sodium Chloride Injection, USP, before administering as an intravenous infusion

Administer a single dose of 16 mg/kg intravenously over 90 minutes (1 hour and 30 minutes)

See drug label for administration in adult patients weighing less than 40 kg.

Pediatrics:

Pre-medicate with diphenhydramine prior to administering Anthim

Dilute the injection in 0.9% Sodium Chloride Injection, USP, before administering as an intravenous infusion

The recommended dose for pediatric patients is based on weight:

Body Weight: Greater than 40 kg Dose: 6 mg/kg

Body Weight: Greater than 15 kg to 40 kg Dose: 24 mg/kg

Body Weight: Less than or equal to 15 kg Dose: 32 mg/kg

Administer the recommended dose of Anthim intravenously over 90 minutes (1 hour and 30 minutes)

Clinical Results

FDA Approval

As it is not feasible or ethical to conduct controlled clinical trials in humans with inhalational anthrax, the efficacy of Anthim for the treatment of inhalational anthrax was based on efficacy studies in NZW rabbits and cynomolgus macaques. Anthim monotherapy administered as a single 16 mg/kg IV dose for the treatment of inhalational anthrax disease resulted in statistically significant improvement in survival relative to placebo in two studies for each species. Anthim administered in combination with antibacterial drugs (levofloxacin, ciprofloxacin and doxycycline) for the treatment of systemic inhalational anthrax disease resulted in higher survival outcomes than antibacterial therapy alone in multiple studies where Anthim and antibacterial therapy was given at various doses and treatment times. Anthim administered as prophylaxis resulted in higher survival outcomes compared to placebo in multiple studies where treatment was given at various doses and treatment times.

Side Effects

Adverse effects associated with the use of Anthim may include, but are not limited to, the following:

headache

pruritus

infections of the upper respiratory tract

cough

vessel puncture site bruise

infusion site swelling

nasal congestion

infusion site pain

urticaria

pain in extremity

Anthim comes with a black box warning of hypersensitivity reactions, including anaphylaxis, have been reported during Anthim infusion

Mechanism of Action

Anthim (obiltoxaximab) is a monoclonal antibody that binds free PA with an affinity equilibrium dissociation constant (Kd) of 0.33 nM. Obiltoxaximab inhibits the binding of PA to its cellular receptors, preventing the intracellular entry of the anthrax lethal factor and edema factor, the enzymatic toxin components responsible for the pathogenic effects of anthrax toxin.