FDA finds anthrax drug to be effective

The U.S. Food and Drug Administration tentatively supported the benefits of an investigational monoclonal antibody used to treat inhalational anthrax this week after animal studies showed improved survival rates.

Rabbits receiving the investigational raxibacumab in combination with the antibiotic levofloxacin showed a 17 percent greater survival rate compared with the rabbits treated with levofloxacin alone, MedPageToday reports.

"Although a positive, statistically significant added benefit result was not achieved with this underpowered study design, there appears to be a trend towards greater survival in rabbits when raxibacumab is co-administered with levofloxacin 84 hours after inhalational anthrax exposure," FDA reviewers said, according to MedPageToday.

Members of the FDA's Anti-Infective Drugs Advisory Committee will vote on the safety and efficacy of raxibacumab's efficacy and safety on Friday.

Human Genome Sciences, a GlaxoSmithKline subsidiary that manufactures raxibacumab, first sought FDA approval for the treatment in 2009.

Raxibacumab combined with levofloxacin was no different in animal survival rates when compared with levofloxacin alone when administered right after anthrax detection. To address the concern, the researchers administered the drugs 84 hours after anthrax exposure.

Raxibacumab, a human monoclonal antibody that targets the protective antigen of anthrax, is administered in a two hour intravenous infusion. The drug may prevent the toxin from causing ill effects.

A safety trial found that the biologic was generally well tolerated in a study of 326 healthy human volunteers. Common side effects included rash, headache and upper respiratory tract infection.

It is anticipated that the FDA will take action on raxibacumab by December 15, MedPageToday reports.