Boosted PI regimen achieves fastest fall in HIV viral load in patients diagnosed late

Individuals diagnosed HIV-positive when they already have severe immune damage who take the "boosted" protease inhibitor Kaletra (lopinavir with a small dose of ritonavir to boost its bio-availability) are significantly more likely to achieve rapid suppression of viral load than patients taking regimens including either the non-nucleoside efavirenz or the protease inhibitor indinavir.

Clinicians in north west Italy have witnessed a doubling in the number of patients in the past two years who were diagnosed with HIV with an CD4 cell count below 200 cells/mm³. In study published in the November 1^st edition of the Journal of Acquired Immune Deficiency Syndromes the Italian doctors examined whether different HAART regimens were more likely to achieve rapid suppression of viral load in 32 patients. All of these individuals were diagnosed with HIV when their CD4 cell count was so low that they were at risk of developing an AIDS-defining condition (below 200 cells/mm³).

All the study participants were prescribed two nucleoside analogues. In addition to these drugs they were randomised to receive the protease inhibitor indinavir, or the non-nucleoside efavirenz, or the boosted protease inhibitor lopinavir/ritonavir.

At baseline the patients in the three arms of the study had comparable demographic and social characteristics. Median CD4 cell count was 32 cells/mm³ and median viral load was over 500,000 copies/mL.

After the first seven days of therapy there was no significant difference in the decline in viral load in the three arms of the study. However, the investigators noted that during the first 24 hours of treatment, lopinavir/ritonavir achieved a 70% reduction in circulating HIV viral load compared to 39% for indinavir and 29% for efavirenz (p=0.020).

Patients receiving lopinavir/ritonavir had a probability of achieving a viral load below 400 copies/mL after seven days of treatment of 13% compared to 12% for efavirenz and 0% for indinavir. At days 14 the probabilities were 40% for lopinavir/ritonavir, 37% for efavirenz and 11% for indinavir. These differences were maintained at day 28, when 53% of individuals taking the boosted protease inhibitor had a viral load below 400 copies/mL compared to 38% of those taking the non-nucleoside and 11% of those taking indinavir.

What’s more, the investigators noted that over a third of the patients taking lopinavir/ritonavir achieved a viral load below 50 copies/mL at day 28, whereas none of the individuals taking the other two study medications achieved this.

Median CD4 cell count increased to 115 cells/mm³ over the month of the study, with no significant differences between the three arms of the study.

The investigators emphasise that all three study regimens are undoubtedly able to achieve good suppression of HIV in the long-term. However, for patients with severe immune suppression the selection of a regimen able to rapidly suppress viral load is important, given the vulnerability of these patients to rapid disease progression. The investigators conclude that a regimen that includes lopinavir/ritonavir is most likely to achieve this.

Further information on this website

Lopinavir - overview