November 21, 2002
A number of studies have previously documented that induction-maintenance regimens involving a switch from three to two drugs after initiation of antiretroviral therapy cannot be expected to maintain low viral loads over protracted periods (e.g., the Trilège study). In fact, most such analyses have reported a rapid rebound in viral load after abandonment of one of the active drugs in a successful three-drug regimen. Now the issue of whether there is room for induction/maintenance regimens in anti-HIV therapeutics has been given new license by regimens that initiate therapy with four drugs and then reduce pill burden to three anti-HIV agents.
In this open-label multi-center (eight sites) study, 51 patients had received Trizivir (AZT/3TC/ABC)/nelfinavir (NFV, Viracept) for 48 weeks and had achieved viral loads less than 50 copies/ml. Eighteen of these patients were then switched to receive only Trizivir. The primary objective of the study was to assess the proportion of such subjects maintaining viral load less than 50 copies/ml at 24 and 48 weeks. Secondary objectives included assessments of CD4 counts, analysis of virological rebound, measurement of metabolic abnormalities, and safety and tolerance of the Trizivir regimen over this period. An intent-to-treat (ITT) analysis was performed.
The results showed that maintenance with Trizivir after induction with Trizivir/nelfinavir was able to sustain the control of plasma viral RNA until week 24 in 16 of 18 patients at less than 50 copies/ml (89 percent). However, some fluctuations were observed over this period and the proportion of individuals who sustained these low viral loads over time were 16/18 (week 4), 14/18 (week 8), 16/18 (week 16) and 16/18 (week 24). Two patients were withdrawn during the period of study, one due to pregnancy and the other for a protocol violation. The results also showed that median plasma viral load remained stable over the 24-week period of study while there was a slight continued increase in CD4 count. No significant variations were observed in regard to any cholesterol, triglyceride, lactate or fasting blood glucose levels during the 24 weeks of study.
These results demonstrate that simplification with Trizivir over 24 weeks following induction with Trizivir/nelfinavir over 48 weeks maintained viral suppression in almost all cases and was well tolerated. Of course, it will be necessary to wait for 48-week data and beyond in regard to further understanding of the durability of this approach. In the meantime, these 24-week data should be considered as both preliminary and encouraging.
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