In a small study conducted at the U.S. National Institutes of Health (NIH), researchers have shown that it may be feasible to treat HIV-infected patients with a simple, once-daily regimen of anti-HIV drugs given in pre-planned, 7-day-on, 7-day-off cycles. This approach is known formally as “short-cycle structured intermittent antiretroviral therapy” (SIT) or colloquially as the “7-7” approach.
“Our data suggest that the 7-7 approach, used with well-chosen drug regimens in settings where patient adherence is high, could be a powerful and cost-effective tool in treating HIV-infected individuals,” says study author Mark Dybul, M.D., of the National Institute of Allergy and Infectious Diseases (NIAID), a component of NIH. “By using half as much antiretroviral medication, drug costs are reduced and drug-related toxicities may be less in the long run.” He adds, “The 7-7 approach may have particular relevance to resource-poor countries around the world.”
Dr. Dybul, NIAID Director Anthony S. Fauci, M.D., and their colleagues report their findings in the June 1, 2004 issue of the Journal of Infectious Diseases.
In their study, the NIH investigators enrolled eight HIV-infected people who had been successfully treated with a combination of three or more antiretroviral drugs for at least 6 months. Upon enrollment, the patients began following a treatment regimen of 7 days without antiretroviral therapy, followed by once-daily treatment with the drugs didanosine (ddI), lamivudine (3TC) and efavirenz for 7 days, followed by 7 days off the antiretroviral drugs, repeating the off-on cycle for more than a year. One patient withdrew from the study for personal reasons at week 24; the other seven patients receiving the 7-7 regimen maintained undetectable levels of HIV in their bloodstream [<50 HIV RNA copies per milliliter] for 60 to 84 weeks. During this period, the study volunteers had no significant changes in their CD4+ T-cell counts, and no evidence of resistance to the antiretroviral drugs in their treatment regimen.
Unlike a previous NIH 7-7 study using as different drug regimen, the investigators did not observe transient "blips" during which bloodstream levels of HIV rise above detectable levels, a finding they attribute to the persistence of efavirenz in the blood throughout the 7-day-off-therapy cycle in the current study.
The authors note that strict adherence to the prescribed regimen in the 7-7 approach is necessary. Of note, the once-daily regimen used by Dr. Dybul and his colleagues may allow for enhanced adherence compared with the twice-daily regimen that the researchers used in a previous study.
In their paper, the authors conclude: “If the safety and efficacy of short-cycle SIT ultimately are demonstrated in clinical settings, it might prove to be an important strategy to expand therapy in resource-limited settings. In this regard, randomized, controlled clinical trials are being conducted in various sites in the United States and other countries to evaluate the clinical usefulness of short-cycle SIT.”