State of inhalational anthrax treatment development seen as positive

At the 5th Annual Public Health Emergency Medical Countermeasures Workshop held recently in Washington, D.C., Dr. Ajoy Chakrabarti gave a presentation on developments in the use of Anthrax Immune Globulin in treating inhalational anthrax.

Dr. Chakrabarti is the senior director and project manager of AIG product development for Emergent BioSolutions, Inc.

When anthrax is inhaled into the body, it is first in the form of spores that are in a state of suspended animation, Chakrabarti said. It is when those spores germinate and become live bacteria that they begin to attack the body.

"But it is not the bacteria that are going to kill you from anthrax," Chakrabarti said. "It's the toxins that they secrete. Anthrax bacteria secrete what is kind of a mixture of several different toxins together which ultimately form the thing that destroys your cellular machinery.

"The goal of our product, in this case the therapeutic, is to treat people when they have already been exposed to anthrax spores."

A person exposed to anthrax could simply develop a high fever, or could be in terrible shape. Reactions to anthrax generally depend on how long it has been since a person was exposed. In most cases, antibiotics should be used immediately, but they may not always be effective.

"Antibiotics are great if you get them to people early enough," Chakrabarti said. "Our therapeutic goes after the toxins that are being produced; the antibiotics go after the anthrax themselves. They'll probably work hand in hand."

The exception occurs in those who are reached too late. In those cases, the antibiotics will be of minimal value since the toxins become more of a threat than the bacteria.

"The idea with our product is that it takes care of the toxin," Chakrabarti said. "It binds it up. It allows it to be eliminated from your system."

Chakrabarti explained the process by which AIG is made. First, a person is vaccinated with BioThrax, an anthrax vaccine made by Emergent BioSolutions, Inc. The person is then given a booster so their immune system produces a large number of anthrax antibodies.

Blood proteins are then removed and the mixture is purified, resulting in the immune globulin product AIG. The process is the same as the one that produces Gamunex, but Gamunex is made without using subjects that have been vaccinated with BioThrax.

"This is a real advantage for us in terms of manufacturing because the Gamunex process is FDA validated," Chakrabarti said. "There is much less concern over any manufacturing related issues."

In terms of composition, 95 percent of the proteins are the same as in Gamunex, but the five percent difference contains the crucial part.

"It's a pool of immune globulin, but it is enriched for anthrax antibodies," Chakrabarti said.

The results of testing so far have been very encouraging, Chakrabarti said, adding that more studies will be undertaken.

"What we're going to do is follow up on the positive results that we have and we'll do additional studies with a much higher level of statistical significance to determine which doses work and then we'll do studies in combination with antibiotics," Chakrabarti said.

Chakrabarti said that the antibiotic studies will be critically important since the drug will most likely always be used in conjunction with some form of antibiotic.