Nevirapine, efavirenz and Kaletra regimens best for treatment naive

Initial HAART regimens including the NNRTIs efavirenz or nevirapine, or the boosted protease inhibitor Kaletra are most likely to achieve a sustained reduction in viral load below 500 copies/mL in HIV-positive treatment naive individuals, according to the results of an international observational study involving over 1,000 patients presented as a poster to the 43^rd Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago on September 15^th.

Investigators from the US HIV Insight^TM study and the Dutch ATHENA cohort analysed data from 1,119 antiretroviral naive patients who started HAART between 1999 and 2002.

Five commonly used HAART regimens were compared. Three were based on protease inhibitors: nelfinavir (339 patients); indinavir boosted by low dose ritonavir (48 individuals); and, Kaletra (lopinavir with low dose ritonavir, 61 patients). The remaining two regimens examined in the study were NNRTI based, with 400 people taking nevirapine and 271 efavirenz.

Effectiveness was measured according to two outcomes: the time taken for HIV viral load to fall below 500 copies/mL; and, the subsequent time taken for virological failure to occur, assessed as two consecutive viral load measurements above 500 copies/mL.

Results were adjusted according to age, sex, previous NRTI use, year of entry to the study, HIV risk group, country of residence, and baseline CD4 cell count and viral load.

The investigators found that individuals prescribed regimens containing efavirenz, nevirapine or Kaletra, but not indinavir boosted by ritonavir, were significantly more likely to achieve a viral load below 500 copies than those starting a nelfinavir-containing regimen (Hazard Ratios [HR] compared to nelfinavir: 1.7, 95% CI, 1.4 - 2.2, p

Individuals taking the NNRTI-based regimens were significantly less likely than those taking either the nelfinavir or indinavir/ritonavir-containing regimens to experience virological failure (HR compared to nelfinavir: 0.38, 95% CI, 0.21 - 0.69, p=0.002, and 1.7, 95% CI 1.1 - 2.5, p=0.018 respectively). There was a trend for patients to experience failure later on Kaletra compared to nelfinavir, but given the small sample size testing for significance was not possible. There were no significant differences, however, in the time to virological failure between patients taking efavirenz, nevirapine or Kaletra.

The investigators conclude, that of the current common initial HAART regimens, those containing efavirenz, nevirapine and Kaletra offer treatment-naive patients the best opportunity to achieve and maintain HIV suppression.