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

This article is more than 21 years old.

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 1st 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.

Glossary

nucleoside

A precursor to a building block of DNA or RNA. Nucleosides must be chemically changed into nucleotides before they can be used to make DNA or RNA. 

boosting agent

Booster drugs are used to ‘boost’ the effects of protease inhibitors and some other antiretrovirals. Adding a small dose of a booster drug to an antiretroviral makes the liver break down the primary drug more slowly, which means that it stays in the body for longer times or at higher levels. Without the boosting agent, the prescribed dose of the primary drug would be ineffective.

AIDS defining condition

Any HIV-related illness included in the list of diagnostic criteria for AIDS, which in the presence of HIV infection result in an AIDS diagnosis. They include opportunistic infections and cancers that are life-threatening in a person with HIV.

disease progression

The worsening of a disease.

p-value

The result of a statistical test which tells us whether the results of a study are likely to be due to chance and would not be confirmed if the study was repeated. All p-values are between 0 and 1; the most reliable studies have p-values very close to 0. A p-value of 0.001 means that there is a 1 in 1000 probability that the results are due to chance and do not reflect a real difference. A p-value of 0.05 means there is a 1 in 20 probability that the results are due to chance. When a p-value is 0.05 or below, the result is considered to be ‘statistically significant’. Confidence intervals give similar information to p-values but are easier to interpret. 

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

References

Boffito M et al. Treating advanced HIV infection. JAIDS 34: 344 – 345, 2003.