September 22, 1995
Media Contact: Marc Kusintz
Phone: (410) 955-8665

A new drug to prevent a viral disease that strikes people with advanced AIDS is effective, but so toxic that it should not be used until doctors can determine a safe dose, according to a study headed by a Johns Hopkins researcher.

The drug, valaciclovir (VACV), a new form of acyclovir, is being studied as a possible preventive treatment for infections caused by cytomegalovirus (CMV) in patients with weakened immune systems, including persons with AIDS. CMV primarily causes diseases of the retina, brain and gastrointestinal tract, and ultimately strikes about 20 to 40 percent of patients with advanced HIV disease.

In the study of 1,227 patients, researchers found that very high oral doses of VACV (2 grams, four times a day), a chemically modified form of acyclovir, produced blood levels of the drug that could be achieved only by giving acyclovir intravenously. And patients who received VACV were less likely to develop CMV disease, especially retinitis, which can cause visual loss and blindness.

But while these levels might be high enough to provide effective protection against many strains of CMV, the dose used in the study proved to be more toxic than the high (800 mg, four times a day) or low doses (400 mg, two times a day) of acyclovir.

"Now that we know that VACV can reduce the rate of CMV infection by about a third, further research is needed to learn how to give a dose that is still effective, but not so high as to be toxic to the patient," says Judith Feinberg, M.D., associate professor of medicine at Johns Hopkins.

Feinberg discussed the results of the study in an oral presentation at the 1995 Interscience Conference on Antimicrobial Agents and Chemotherapy in San Francisco on Sept. 20.

The researchers previously had found that when patients receive VACV by mouth, the levels of acyclovir in the blood are three to five times higher than when patients get acyclovir itself, because acyclovir is not well-absorbed by the body after being taken orally.

Other authors of the study include David Cooper, M.D. (St. Vincent's Hospital, Sydney, Australia) and Shelley Hurwitz, Ph.D. (Harvard University).

The study was supported by funds from the National Institutes of Health, AIDS Clinical Trials Group (U.S. sites) and Glaxo Wellcome Company (international sites).

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