Anti-anthrax agent shows promise in humans

NEW YORK (Reuters Health) – A human monoclonal antibody
against the agent that causes anthrax (Bacillus anthracis
protective antigen), which has shown action against inhaled
anthrax in animals, appears to be safe and well tolerated in
humans as well, researchers report.

“This report describes the first investigational agent
against anthrax infection to be evaluated in a clinical study
since the 2001 anthrax attacks in the United States,” Dr. Mani
Subramanian of Human Genome Sciences in Rockville, Maryland and
colleagues write in Clinical Infectious Diseases, a medical
journal.

With further successful testing, the anti-anthrax agent
dubbed “PAmAb” could be used in individuals with suspected or
probable exposure to aerosolized anthrax spores.

Anthrax spores lend themselves well to aerosolization are
hard to breakdown in the environment; “thus they represent one
of the greatest threats in biological warfare,” the scientists
note.

Following a single dose, PAmAb provided complete protection
against death in a rat model of anthrax disease. It also
provided a survival advantage in rabbits and monkeys.

This led Subramanian’s team to investigate PAmAb’s safety
and activity in 105 healthy human volunteers. Subjects received
a variety of doses of the agent or placebo as a continuous
infusion or a single intramuscular injection.

Results showed that PAmAb can be safely administered in
humans and is well tolerated, producing only transient
mild-to-moderate side effects, according to the team.

Moreover, the agent has a long half-life in the human body
after a single injection and, importantly, provides serum
levels that have been shown to provide protection against
anthrax in animals.

These findings, the researchers conclude, support “further
clinical development of PAmAb as a novel therapeutic agent for
inhalational anthrax.”

SOURCE: Clinical Infectious Disease July 1, 2005.