Bioterror Drugs May Get Fast-Tracked
FDA considers whether to bypass human testing
TUESDAY, Oct. 30, 2001 (HealthDayNews) -- With an eye to making more drugs available to fight bioterrorism, the U.S. government might allow companies to market drugs that have been proven effective in animals but never tested for how well they work in people.
Before it approves a new prescription medication, the Food and Drug Administration generally requires multiple levels of testing, including what it considers a pivotal third stage of clinical studies, which proves whether a product is effective on people.
But in October 1999, the FDA proposed that companies working on compounds for treating deadly or disabling agents could submit animal data on a product's effectiveness when human studies "are not feasible and cannot be ethically conducted."
This so-called "animal rule," which the FDA has indicated would apply to chemical, biological, radiological or nuclear substances, remains on the drawing board two years later.
But Dr. Janet Woodcock, director of the agency's Center for Drug Evaluation and Research, says the agency hopes to make it policy "soon."
"The comment period is done, we've analyzed all the comments and prepared the final version," but the rest of the government must sign off on the rule, she says.
Michael Werner, bioethics counsel for the Biotechnology Industry Organization, doesn't believe officials have acted too slowly to implement the proposal. "I'm sure this was not a huge priority in 1999," he says. "I just think it's the regulatory process."
Getting effective treatments to consumers quickly is a priority, but making sure they're safe is equally important, he says.
"The worst thing would be if a product gets on the market and it's harmful or it doesn't work," Werner says. "That would be a disaster, and everybody knows it."
The biotech industry group hasn't taken a formal position on the so-called animal rule, but Werner says it supports the principle.
"There's needs to be some flexibility or some expediting of the FDA regulatory process," he says. "One way to do that is to rely on animal efficacy studies." However, should the agency finalize the proposal, it must do so in a way that makes its expectations for companies clear, he cautions.
"It would be important for there to be some clarification, so that companies would have the confidence that they could proceed in a way that's predictable," Werner says. "I think that the FDA's going to make every effort to do that."
If the new proposal gets approved, drug companies still would have to proceed on a case-by-case basis with any new products, Woodcock says. That's because the animal considered appropriate for testing would vary from disease to disease.
Primates, for instance, might be a good choice for an anthrax antibiotic. Indeed, Cipro won approval for the disease last year largely because of tests in rhesus monkeys. But experts say they're not ideal for testing drugs against other bioterror agents.
"You can't just say you have to use monkeys and dogs," Woodcock says. "Say you're looking at a skin agent. From a scientific standpoint, the pig is the correct model for human skin. That's why we can't dictate species."
Part of the logic behind the proposal, experts say, stems from a desire not to "challenge" people who participate in tests of new drugs for infectious agents that have no known treatments, or which could cause lasting harm.
The government, for example, is now sponsoring a multi-center study of 680 young adults to see whether the existing stock of 15.4 million doses of smallpox vaccine could be diluted into 75 million doses or more with its effectiveness intact.
Dr. Carol Tacket, of the University of Maryland Center for Vaccine Development, is leading one arm of that trial, which is comparing the potency of the vaccine at one-tenth and one-fifth of its normal concentration.
Tacket's center intends to recruit 170 volunteers. Enrollment began Oct. 24 and hasn't yet met that goal, she says. One reason may be people's fear of contracting smallpox, but Tacket stresses that, while there are small but definite risks of complications from the vaccine, smallpox isn't one of them.
"This does not involve any kind of a challenge with smallpox at all," she says.
Tacket and her colleagues will be looking for what they call the telltale vaccine "take," a blister that forms at the site of the injection. That indicates an immune reaction to the vaccinia virus, related to cow pox, that generates protection against smallpox.
A small study last year using vaccine watered down to one-tenth its usual strength produced a take rate of 70 percent, Tacket says. So if a solution twice that strong can generate complete coverage, "it would be a long way toward vaccinating the entire population," she says. Results from the trial could be ready in three months.
In the meantime, Lenore Gelb, an FDA spokeswoman, says regulators are working with other health officials to hasten review of drugs that might help in the defense against bioterror. "It's going to speed up everything we do," she says.
But the question remains: What constitutes an anti-terror product?
"We have to decide what the greatest public health need is," Gelb says. "There's no regulation that states which products are bioterror products and which aren't."
And, if the scientists did test drugs or vaccines on people against bioterror diseases with no treatments, would anyone volunteer?
There's a good chance some might, says Janet Wittes, president of the Society for Clinical Trials, a research standards group based in Washington, D.C.
After all, the yet-unsuccessful quest for a malaria vaccine has relied on many human volunteers willing to subject themselves to almost certain illness when they're intentionally infected with the parasite that causes the disease, she says.
"I think it's altruism," Wittes says. "It's really because people understand that volunteering for this kind of study is actually doing good."
And, she adds, these sorts of studies generally can be small, so "you don't need lots of altruistic people."
What To Do
For more on bioterrorism and what officials are trying to do to stop it, check out the Web sites of the National Memorial Institute for the Prevention of Terrorism, or the Centers for Disease Control and Prevention. Or visit the FDA online.
For a history of the smallpox vaccine, take a look at information provided by Stanford University.