A Rockville biotechnology company plans to announce today that it has received government permission to launch human tests of a drug designed to combat anthrax, the biowarfare agent that killed five people and terrified Congress in 2001.

Human Genome Sciences Inc. appears to be ahead of several competitors to develop such a compound. Its drug, Abthrax, could be submitted to the Food and Drug Administration for approval in months, presenting the Bush administration with a test of its stated commitment to buy anti-terrorism drugs if industry takes the trouble to develop them.

The drug is a synthetic antibody, a type of protein similar to antibodies produced by the immune system, that neutralizes the main toxin produced by the anthrax germ. Anthrax can already be treated with antibiotics, but drugs like the one Human Genome Sciences is developing might be useful as an adjunct to or replacement for antibiotics in several situations.

The drug is on an unusually fast path.

Anthrax is rare as a naturally occurring disease, and, because it's potentially fatal, humans can't ethically be exposed to it in tests. That means the only test available to show the new drug works is in animals. Human Genome Sciences said the drug has already passed that test, showing marked improvement in survival for animals that received the new drug and were exposed to anthrax spores.

The company has now received FDA permission to test the drug in people, but only to see if it can be administered safely. The test subjects won't be exposed to anthrax spores. The initial safety tests, in scores of healthy volunteers, are likely to go rapidly.

But William A. Haseltine, chairman and chief executive of Human Genome Sciences, said the company won't proceed to the more expensive final phases of safety testing unless it's clear the government is willing to buy the drug. "It has to make economic sense, or we will not proceed with it," he said.

Under new legislation, drugs like this may win FDA approval based only on animal studies of their effectiveness, coupled with human safety tests. That means the drugs may well enter national anti-terror stockpiles without doctors having a clear fix on how to use them.

Theory suggests that an anthrax antibody, like Abthrax, may be useful in several situations. If terrorists create an anthrax strain resistant to antibiotics, an antibody might be the only treatment for exposed people.

An anthrax vaccine is available, but it requires multiple shots over months. By contrast, an antibody injection would in theory confer instant immunity, so it might save the lives of soldiers or workers at risk of exposure to the germ who haven't already been immunized.

Finally, a high proportion of people who develop anthrax symptoms die in spite of receiving antibiotics. The antibiotics attack the germ itself, but not a toxin that it releases into the blood. Drugs like Abthrax are specifically designed to attack the toxin, so they might, in theory, save the lives of people who are not responding well to standard anthrax treatment.

Exactly how well the drug would work may be answered only if there's another terrorist attack with anthrax, like the ones in 2001 that emptied congressional and media offices, killed several postal workers and others, and forced some 10,000 people, including members of Congress and their employees, onto antibiotic therapy as a preventive measure.

Because a drug like Abthrax would generally be useful only in an attack, there's likely to be no routine commercial market for it. Instead, the government has pledged to create a market for such drugs by stockpiling them if they meet certain criteria.

The nation already has large stockpiles of anti-terrorism drugs and supplies, but administrators at the Department of Health and Human Services have complained that they don't have the authority to make long-term purchase commitments that would create a stronger incentive for firms to undertake expensive research and development.

President Bush has asked Congress to fix that by passing Project BioShield, which would commit some $6 billion to anti-terror defenses over 10 years. The National Institutes of Health has said the Human Genome Sciences drug may serve as a test for whether Project BioShield can work.

The legislation has bogged down in Congress. Bush, speaking Monday to biotechnology executives in Washington, demanded again that Congress resolve the issues. "For the sake of our national security, . . . Congress must pass the BioShield legislation as soon as possible," Bush said.