Two experimental drugs designed to treat anthrax infection have shown promise in recent tests, according to their developers — evidence that the nation might eventually produce new defenses against a weapon that terrorized Capitol Hill and much of the East Coast in late 2001.
Human Genome Sciences Inc., a Rockville biotechnology company, plans to reveal today that its anti-anthrax drug appears safe for human use based on a recent test. The company disclosed yesterday at a scientific meeting in Baltimore that separate tests in rabbits suggested the drug might be effective if given within 12 hours of exposure to anthrax.
A second company, Elusys Therapeutics Inc. of Pine Brook, N.J., said a similar anti-anthrax drug it is developing was able, if administered immediately ahead of time, to protect rabbits and mice from the lethal effects of inhaling anthrax spores. The company is not as far along as its Rockville competitor, but so far the two drugs appear quite similar.
Most of the test results have not yet been scrutinized by the Food and Drug Administration, and approval, if it ever comes, could still be several years away.
The drugs are artificial antibodies, or proteins that mimic the natural proteins made by the body to fight off invading germs. Several companies are developing such drugs in response to calls from the government, soon after the attacks of 2001, for new defenses against terrorist threats. Anthrax spores sent through the mail that October sickened 18 people, killed five of them, emptied offices on Capitol Hill, forced 10,000 people onto preventive drugs and terrified the nation for weeks.
Embarrassment of riches
Various new treatments and vaccines are under development by the nation's biotechnology industry to counter biological weapons. The government, though it has invested tens of millions of dollars in development grants, has yet to commit to buying many of these products for the nation's anti-terrorism stockpiles. President Bush called on Congress more than a year ago to pass legislation encouraging such purchases, but the law authorizing his program, Project Bioshield, has bogged down in the Senate.
An even bigger issue has cropped up in recent months, though: So many companies have responded to the task that the government now confronts an embarrassment of riches. Multiple companies are working on similar drugs, and the government will have to decide which to buy without definitive human tests of their effectiveness. While the safety of the drugs can be tested in people, their effectiveness cannot be, since it would be unethical to expose people to bioterror germs.
"We would completely break the bank if we committed to purchasing every one" of the products under development, said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, which has funded development work at many companies. "We just can't do that."
The government is working on ground rules for judging competing bioterror products, he said.
Executives of Human Genome Sciences yesterday repeated a statement they have made several times in the past nine months, that they would soon be forced to halt development of their drug unless the government makes a firm purchase commitment. With no private market for anthrax drugs, the only potential buyer is the federal government. Unlike most companies working in the field, Human Genome Sciences developed its drug, known as Abthrax, without government grant money.
"We are at a decision point," said Craig Rosen, the company's president of research and development.
Animal tests are the best substitute for human effectiveness studies. Human Genome Sciences has reported that Abthrax can prevent death in rabbits and monkeys if given by injection shortly before anthrax exposure, and the new tests suggest the same is true if the drug is administered soon after exposure.
105 human volunteers
The company will report this morning that in safety tests of 105 human volunteers, the drug caused no greater problems than a dummy injection, and achieved blood levels likely to be effective against anthrax.
The Elusys antibody, known as ETI-204, has yet to enter human tests, but the company reported rabbit and mouse tests yesterday that mimic test results reported earlier for Abthrax.
The latest tests suggest that anthrax antibodies, though potentially useful, share one of the main disadvantages of current treatment with antibiotics. Their effectiveness appears to drop off rapidly the later they are administered in the course of the disease. That's what apparently happened to some people who died from anthrax exposure in 2001; their treatment didn't begin until they had been sick for days.
The biggest open question is whether an antibody could be combined with antibiotics to yield a treatment more effective than either alone. Expensive tests on monkeys could answer that question, but Human Genome Sciences has said it won't move forward with those, or with larger human safety tests, until the government decides whether to buy Abthrax.
Even if the antibodies prove roughly equivalent to antibiotics in treating anthrax, it might be desirable to have the artificial antibodies on hand, government scientists have said. Bioterrorists could easily devise anthrax strains resistant to all known antibiotics. But designing strains resistant to antibodies would be harder, in theory, so in some attacks an antibody might be the only effective treatment.
"As a physician, I hope this thing is never used," said David Stump, executive vice president for drug development at Human Genome Sciences. "As a citizen, I think we'd all be very reassured to know something like this is available should that day ever come."
