In June, nevirapine became the ninth drug approved by the Food and Drug Administration (FDA) for the treatment of people with HIV infection. The first in a new class of antiretroviral drugs known as non-nucleoside reverse transcriptase inhibitors (NNRTIs), nevirapine will be marketed under the name Viramune by Boehringer Ingleheim Pharmaceuticals, Inc. As their name implies, NNRTIs inactivate reverse transcriptase, the same HIV enzyme targeted by the nucleoside analog drugs AZT, ddI, ddC, d4T and 3TC. NNRTIs and nucleoside analogs attack the enzyme at different locations, however.
Central to the FDA's approval of nevirapine was the NIAID clinical trial ACTG 241, a study of nearly 400 patients with advanced HIV infection who had received extensive treatment with nucleoside analogs. ACTG 241 showed that nevirapine, combined with AZT and ddI, was significantly better than the combination of AZT and ddI at reducing viral load and increasing CD4+ T cell counts in these patients. A second study conducted by the drug's manufacturer showed that the same three-drug combination also was significantly better than AZT and ddI for HIV-infected patients who had received no prior treatment.
The new drug further expands the treatment options available to individuals infected with HIV. In combination with nucleoside analogs, nevirapine could be used as a first-line therapy or as an alternative treatment for patients who either show no improvement with other drugs or experience adverse reactions to them, says Steven M. Schnittman, M.D., assistant director for clinical research in NIAID's Division of AIDS.
Some individuals, for example, can't tolerate the new protease inhibitors," says Dr. Schnittman. "For those patients, it may turn out that a regimen of two nucleosides combined with nevirapine provides anti-HIV activity reasonably close to that seen with protease inhibitors." Dr. Schnittman adds that the additional combination therapy regimens made possible by nevirapine could help physicians devise better strategies for avoiding drug resistance.
Another attractive aspect of nevirapine is its long half-life -- the time it takes for half of a given dose to be eliminated from the body. Nevirapine remains active much longer than other antiretrovirals and thus can be administered less frequently. Dr. Schnittman says nevirapine's long half-life suggests that it might be useful in strategies for preventing mother-to-infant HIV transmission by reducing the amount of virus in a womans blood before she gives birth. NIAID-supported clinical trials are under way in which HIV-infected pregnant women are given a dose of nevirapine when they arrive at the hospital in labor.
The drug is highly active and should remain in the woman's blood, and hopefully the infant's as well, throughout the perinatal period," says Dr. Schnittman. "Although HIV quickly develops resistance to nevirapine when it is administered alone, that should not be a concern in perinatal settings, where the drug will only be given for a day or two."