Failure of treatment with first-line lopinavir boosted with ritonavir can be explained by novel resistance pathways with protease mutation 76V.

Background: Virological failure of first-line antiretroviral therapy based on lopinavir boosted with ritonavir (lopinavir/r) has rarely been associated with resistance in protease. We identified a new genotypic resistance pathway in 3 patients who experienced failure of first-line lopinavir/r treatment.

Methods: Viral protease and the C-term part of Gag were sequenced.