April 20, 2000 -- A new way to fight viruses might mean new treatments for herpes, and maybe even AIDS. In a study reported at a scientific meeting, researchers today said that members of a new class of drugs -- some of which already are known to be safe in humans -- might stop many major viruses dead in their tracks.
"This is a completely new approach," study leader Priscilla A. Schaffer, PhD, tells WebMD. "All of the existing antiviral drugs target the virus. But viruses don't grow in a vacuum, they grow in a cell. The cell provides the virus with lots of [things] it needs to grow." The new treatments would take these things away, leaving the virus high and dry like a seed without water.
In order for viruses to reproduce, they must use a human substance known as "cdk." Cdk works like a little motor that drives the cell through the process of division. The new drugs throw a monkey wrench into the cdk machinery. When tested against herpes viruses in the test tube, they worked so well that the virus could not make any copies of itself.
Perhaps the most exciting thing about the research is the suggestion that drugs that block cdk might be effective not only against all human herpes viruses, but also against hepatitis viruses and even HIV.
"The potentially exciting thing about this class of compounds is the spectrum of viruses likely to be affected," says Schaffer. "Our best guess is all the herpes viruses ... will be shown to be inhibited." But more importantly, many human viruses, including HIV, are likely to be inhibited by these drugs, he says. "While one can say this is an early stage of the research, the likelihood is great that other viruses will be affected," he adds. Schaffer is chair of the microbiology department at the University of Pennsylvania School of Medicine.
The cdk motor goes out of control in some cancers. Because of this, many drug companies are working to develop anti-cdk drugs. One of these drugs already is being studied at the National Cancer Institute (NCI) -- and the trials already have answered one major question.
"We are very confident that we can give it safely to humans," NCI researcher Edward A. Sausville, MD, PhD, tells WebMD. "The major side effects are related to diarrhea." That is one of the reasons drug companies are looking at other drugs to block cdk -- drugs that might not have this unpleasant side effect, he says.
Sausville says that anti-cdk drugs will still have to undergo full safety tests before they can be used against virus infections. Although previous studies in cancer patients have shown that the drugs that block cdk appear to be safe in humans, the drugs in development to fight viruses are slightly different, he says. Therefore, the drugs still need to be closely scrutinized, but Sausville is encouraged that this new research will speed things along. Sausville is an associate director of the NCI's developmental therapeutics program.
It will also be of great interest to show exactly which of the cdks must be blocked in order to stop these viruses from causing disease, University of Iowa biochemist David H. Price, PhD, tells WebMD. Price and co-workers are currently developing drugs similar to cdk blockers to fight HIV.
- Scientists say a new class of drugs may be effective against viruses that cause diseases like herpes and AIDS.
- Instead of trying to kill the virus, these drugs take a different approach: They prevent an invading virus from using its human host's cdk, a substance that drives cell division. Without cdk, the virus can't reproduce itself.
- It's possible that cdk-blocking agents could be used to fight certain types of cancer. Scientists still have to access their safety in people as well as learn how knocking out cdk can prevent a viral infection.