The US Food and Drug Administration (FDA) has approved Anthim (obiltoxaximab) injection, the Elusys Therapeutics' monoclonal antibody (mAb) anthrax antitoxin. Anthim is indicated in adult and paediatric patients for the treatment of inhalational anthrax due to Bacillus anthracis in combination with appropriate antibacterial drugs, and for prophylaxis of inhalational anthrax when alternative therapies are not available or are not appropriate.

Anthim should only be used for prophylaxis when its benefit for prevention of inhalational anthrax outweighs the risk of hypersensitivity and anaphylaxis. The effectiveness of Anthim is based solely on efficacy studies in animal models of inhalational anthrax. There have been no studies of the safety or pharmacokinetics (PK) of Anthim in the paediatric population. Dosing in paediatric patients was derived using a population PK approach. Anthim does not have direct antibacterial activity. Anthim should be used in combination with appropriate antibacterial drugs. Anthim is not expected to cross the blood-brain barrier and does not prevent or treat meningitis.

“Elusys is delighted to receive FDA approval for Anthim and, in addition to FDA, we thank the Biomedical Advanced Research and Development Authority (BARDA), the National Institutes of Health (NIH), and the Department of Defense (DoD), as well as our group of prominent biotech investors, for their ongoing collaboration and support,” said Elizabeth Posillico, PhD, president and chief executive officer of Elusys. “This marks a historic milestone for our company, resulting from an unprecedented partnership with several government agencies, to develop a new anthrax antitoxin that will be an important addition to the Strategic National Stockpile (SNS) and help protect the safety of our citizens and emergency personnel in the event of biowarfare attack. We are continuing product development to deliver additional treatment options to the SNS and further protect Americans.”

“Maintaining a robust supply of treatment options, including antitoxins and other medical countermeasures, to protect public health and enhance national health security is critical to the safety of our civilians and military personnel. Anthim is an important addition to the Strategic National Stockpile and is an example of a successful partnership between government and the biomedical industry to develop critically needed medical countermeasures,” said Clifton R. Lacy, MD, Professor and Director, Institute for Emergency Preparedness and Homeland Security, Rutgers University.

Anthim is a monoclonal antibody that binds to the protective antigen (PA) component of anthrax toxin. Anthim’s toxin neutralizing activity prevents entry of anthrax toxin into susceptible cells, avoiding further spread of the toxin throughout the body and the ensuing tissue damage that leads to death. Anthim is supplied as single-dose vials for intravenous (IV) infusion.

Anthrax is a life-threatening infectious disease caused by Bacillus anthracis. Cases of inhalational anthrax in humans can occur through intentional spread of B. anthracis spores as a biowarfare or bioterrorism agent. B. anthracis spores introduced through the lungs lead to inhalational anthrax, which is deadly in humans.

Because 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 is based on efficacy studies in two animal models. The animal efficacy studies are conducted under widely varying conditions, such that the survival rates observed in the animal studies cannot be directly compared between studies and may not reflect the rates observed in clinical practice.

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.

The Anthim programme was supported primarily with federal funds from the Office of the Assistant Secretary for Preparedness and Response, Biomedical Advanced Research and Development Authority (BARDA), the Department of Health and Human Services (HHS) under Contract numbers HHSO100201000026C and HHS0100201100034C.

Elusys Therapeutics, a private company based in Pine Brook, New Jersey, is focused on the development of antibody therapeutics for the treatment of infectious disease.