Human Genome sees FDA delay with anthrax treatment

ROCKVILLE, Md. - Human Genome Sciences Inc. said Monday the Food and Drug Administration will not approve the company's anthrax treatment until it receives additional information on the potential drug.

The drug candidate, called raxibacumab or ABthrax, is aimed at treated inhaled anthrax. It is being developed under a 2006 contract with the U.S. government. Human Genome said it fulfilled its commitment to deliver 20,000 doses of raxibacumab to the Strategic National Stockpile for emergency use in the treatment of inhalation anthrax. In July, the U.S. government exercised its option to buy an additional 45,000 doses of raxibacumab for the stockpile, to be delivered over a three-year period.

The FDA approval for commercial use is separate from the U.S. government's stockpiling of the drug for emergency use.

Human studies of the drug candidate were not feasible, considering there are relatively few cases of Anthrax exposure and creating a study around exposure would be ethically questionable. Instead, the company focused on animal studies.

A study published in the New England Journal of Medicine in July showed ABthrax was significantly more effective than a placebo in protecting against inhaled anthrax. Another study showed the drug was safe for use in humans.

The studies involved rabbits and monkeys who were exposed to anthrax spores at a level that was either 100 times or 200 times the average lethal dose. They were then treated with either ABthrax or a placebo, and survival rates for animals treated with the drug were significantly higher.

"We have responded to all of FDA's previous questions," said Sally D. Bolmer, senior vice president of development and regulatory affairs at Human Genome. "We plan to address the current questions as well. In certain respects, the Complete Response Letter (request) appears to be inconsistent with the FDA's published final rule governing the development of new drugs when human efficacy studies are not ethical or feasible."

Shares of Human Genome Studies fell 50 cents to $27.39 in morning trading.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.