Anthrax Monoclonal Antibody Therapeutic – Product Candidate

• Disease Overview
• Prevalence and Current Treatment
• Product Candidate Description
• Announcements

Disease Overview

Bacillus anthracis are naturally occurring, spore-forming bacteria found in soil throughout the world. B. anthracis spores can withstand extreme heat, cold and drought for long periods without nutrients or air. Anthrax infections occur if the spores enter the body through one of three possible routes: 1) a cut, abrasion or open sore (cutaneous anthrax), 2) ingestion of the spores (gastrointestinal anthrax), or 3) inhalation of the spores (inhalational anthrax). Once inside the body, the spores germinate into bacteria that then multiply. B. anthracis bacteria secrete three proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF). Individually these proteins are non-toxic, but they can become highly toxic if allowed to be combined in a binary fashion (PA + LF or PA + EF) on the surface of human or animal cells.

Cutaneous anthrax, although rare in the United States, is the most common type of naturally acquired anthrax. Cutaneous anthrax typically occurs through contact with contaminated animals and animal products. The fatality rate for untreated cases of cutaneous anthrax is estimated to be approximately 20%.

Inhalational anthrax is the most lethal form of anthrax, and consequently aerosolized anthrax spores are the most likely method to be used in a potential anthrax bioterrorism attack. Inhalational anthrax has been reported to occur from one to 43 days after exposure to aerosolized spores. Initial symptoms of inhalational anthrax are non-specific and may include sore throat, mild fever, cough, achiness or weakness, lasting up to a few days. After a brief period of improvement, the release of anthrax toxins may cause an abrupt deterioration of the infected person, with the sudden onset of symptoms including fever, shock and respiratory failure. Hemorrhagic meningitis is common. Death often occurs within 24 hours of the onset of advanced respiratory complications. The fatality rate for inhalational anthrax is estimated to be between 45% and 90%, depending on whether aggressive, early treatment is provided.

Prevalence and Current Treatment

Currently, there are no approved products for the treatment of anthrax disease that specifically target anthrax toxins that have been released into the body. Because early symptoms of anthrax disease are non-specific, a delay between exposure to anthrax and diagnosis of disease may occur and may render current post-exposure treatments less effective. As observed in the 2001 letter attacks, by the time individuals with inhalation anthrax were symptomatic, antibiotics prevented death in only 6 of 11 cases.

In August 2004, the U.S. Department of Health and Human Services (HHS) issued a request for proposal (RFP) seeking between 10,000 and 200,000 courses of treatment of products to treat inhalational anthrax disease, including monoclonal antibodies, polyclonal antibodies (such as human immune globulin), and other protein therapeutic products. To date, HHS has awarded two procurement contracts for anthrax therapeutics for placement in the Strategic National Stockpile (SNS) to: 1) a Canadian-based company for 10,000 therapeutic courses of treatment of an anthrax immune globulin and 2) a U.S.-based company for 20,000 therapeutic courses of treatment of a monoclonal antibody.

Product Candidate Description

We are developing AVP-21D9, a monoclonal anthrax therapeutic for use against symptomatic anthrax infection. This product is a fully human monoclonal antibody that appears to be highly active as a therapeutic for anthrax based on laboratory and experimental animal studies conducted to date. These studies suggest that AVP-21D9 could have the potential to be a life-saving medical countermeasure and to fill an important unmet need. This product candidate is being developed with funding support from NIAID that totals over $24.3 million. The addition of an anthrax monoclonal therapeutic to the company’s portfolio would broaden Emergent’s anthrax countermeasure program and reflects the company’s ongoing commitment to develop a full portfolio of countermeasures to strengthen national preparedness in the event of future anthrax attacks.

Announcements