sible role of pharmacokinetic raltegravir monitoring and the biological meaning of unintegrated proviral DNA. Raltegravir is a novel HIV-1 integrase inhibitor that prevents proviral DNA-strand transfer and HIV genome integration into the host chromosomes

Background: Raltegravir is the first approved antiretroviral able to prevent HIV genome integration into the host chromosomes. The aim of the study is to test if raltegravir plasma concentrations can be associated with proviral DNA decline during raltegravir-based salvage therapy. Methods: A total of 33 multidrug-resistant HIV-infected patients were enrolled in a longitudinal open-label pilot study and completed a 24-week follow-up. The CD4+ T-cell count, plasma viral load, proviral HIV DNA and twolong-terminal repeat (2-LTR) circular forms were assessed at baseline, day 14, 30, 60, 90 and 180. The raltegravir trough concentration (Ctrough) was measured by HPLCultraviolet and patients were divided into two groups according to the median raltegravir Ctrough. Results: The mean ±sd values of baseline HIV RNA, CD4+ T-cell count and HIV DNA were 4.4 ±0.82 log copies/ml, 256 ±177 cells/mm3, and 2,668 ±4,721 copies/106 peripheral blood mononuclear cells, respectively. Despite a transient increase of total DNA at week 2, a marked proviral DNA decay (P=0.01) with an increase of the 2-LTR unintegrated/ total DNA ratio (P=0.06) over time was observed. At univariate analysis, no correlation between raltegravir Ctrough and classical virological parameters was observed. Nevertheless, the decay of proviral HIV DNA was more pronounced in patients displaying Ctrough<158 ng/ml with respect to those with Ctrough>158 ng/ml (P=0.046). Conclusions: Successful raltegravir-based therapy produces a significant decline in proviral DNA and is associated with an increase of the unintegrated/total DNA ratio. Further studies are necessary to define the possible role of pharmacokinetic raltegravir monitoring and the biological meaning of unintegrated proviral DNA.