Differentiation of genotypic resistance profiles for amprenavir and lopinavir, a valuable aid for choice of therapy in protease inhibitor-experienced HIV-1-infected subjects

One of the major challenges to the successful long-term treatment ofHIV-1 infection is overcoming the development of increasing levelsof antiretroviral resistance that often accompany the failure of suc-cessive treatment regimens. In order to meet this challenge a goodunderstanding of genotypic resistance profiles and the potential forcross-resistance within each class of antiretrovirals is essential. Forthe protease inhibitors (PIs), cross-resistance is complex, as a resultof the large number of mutations involved. Amprenavir and lopinavirare potent PIs used in ritonavir-boosted regimens, often in patientswho have already experienced treatment with other PIs. The resist-ance profiles of these two PIs overlap to a certain extent but also con-tain some important differences that can be exploited in the choice ofoptimal treatment for PI-experienced patients. This article reviewsour own research and that of others, in order to clarify the similaritiesand the differences between the genotypic resistance profiles foramprenavir and lopinavir. Whereas phenotypic data are valuable forunderstanding resistance, HIV-1 genotyping is critical in making theoptimal choice between these two drugs in PI-experienced subjects.