Weekly cycles of once-daily anti-HIV drugs could reduce cost of HIV treatment

In a small study conducted at the US 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, sevenday on, sevenday off cycles. This approach is known formally as "short-cycle structured intermittent antiretroviral therapy" (SIT) or colloquially as the "7-7" approach.

Says study author Dr Mark Dybul of the National Institute of Allergy and Infectious Diseases (NIAID), a component of the NIH, "Our data suggests 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." He adds, "The 7-7 approach may have particular relevance to resource-poor countries around the world…By using half as much antiretroviral medication, drug costs are reduced and drug-related toxicities may be less in the long run."

Dr Dybul and Dr Anthony S. Fauci, director NIAID, along with 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 six months. Upon enrolment, the patients began following a treatment regimen of seven days without antiretroviral therapy, followed by once-daily treatment with the drugs didanosine (ddI), lamivudine (3TC) and efavirenz for seven days, followed by seven 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 a different drug regimen, the investigators did not observe transient "blips" during which bloodstream levels of HIV rise above detectable levels. They attribute this finding 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, randomised, 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."