Objectives: To evaluate the virological, immunological and clinical responses to the boosted double protease inhibitor (PI) regimen combination of lopinavir/ritonavir and saquinavir ('LOPSAQ') without reverse transcriptase inhibitors (RTI) in HIV-positive patients who have few viable RTI treatment options. Methods: Cohort study of 128 heavily pre-treated patients who were experiencing therapy failure on their current regimen due to RTI resistance and/or systemic toxicities. Patients with

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... stance mutations or RTI toxicity underwent a structured treatment interruption (STI) (n = 76) until virus reverted to wild-type or until resolution of toxicity symptoms. Baseline was defined as the time point when lopinavir/ritonavir plus saquinavir therapy was initiated. Virological response was defined as viral load <400 copies/mL at week 48. Results: A total of 78 (61%) patients experienced a virological response to therapy (ITT). Median viral load at baseline was 5.06 log 10 copies/mL; at week 48 median was 2.16 log 10 copies. Median CD4 at week 48 was 280 cells/mm 3 compared with 172 cells at baseline. At week 48, 78/128 patients were still on therapy. In univariable analyses, significant predictors of virological response included higher CD4 count (P < 0.001), lower viral load (P = 0.002), less PI-experience (P = 0.006) at baseline and fewer PI-resistance mutations (P = 0.043) at end of prior failing regimen; in the multivariable analysis only higher CD4 count at baseline (P = 0.009) and fewer number of drugs previously taken (P = 0.003) could be specified as independent predictors for response. Conclusions: The combination of lopinavir/ritonavir and saquinavir without RTIs is a potential option as salvage therapy for patients experiencing therapy failure due to RTI resistance or toxicity. This regimen may not be suitable for patients with very low baseline CD4 cell counts, very broad antiretroviral therapy experience or extensive PI-resistance mutations.