Human Genome Sciences Inc.’s experimental anthrax treatment, studied more extensively in animals than in humans, may not be more effective than older therapies. U.S. Food and Drug Administration staff members said studies may not be sufficient to show the drug, called raxibacumab, works better than antimicrobials, in a report posted today on the agency’s Web site. An FDA advisory panel will meet Oct. 27 in Silver Spring, Maryland to discuss whether to approve the treatment. Raxibacumab, also called Abthrax, would be the Rockville-based company’s first marketed drug. Human Genome Sciences has already delivered 20,000 doses of the antibody to the U.S. Strategic National Stockpile, which accumulates treatments to protect citizens in the event of a bioterrorist attack or public health emergency. “When given in combination with antimicrobials, the efficacy of the combination was high, but the efficacy of antimicrobials alone was also high, raising the question of whether the animal model adequately reflects the findings from patients with inhalational anthrax,” the FDA staff wrote in the documents. — Bloomberg