• Changes in plasma HIV-1 RNA load
  

• Changes in the genotype of the dominant quasispecies
  
• Replicative fitness of the dominant quasispecies
  
• Changes in CD4+ and CD8+ cell counts
  

Mathematical modeling has suggested that cyclic use of antiretroviral therapy can be an effective strategy in lowering viral load in HIV-1 infected patients when regular triple drug combinations have lost efficacy due to the emergence of HIV resistance mutations.

This is an open label, crossover pilot study to explore the safety and efficacy of a rapid cycling regimen of antiretroviral combination therapy in HIV-1 infected patients with virus harboring genotypic resistance to at least three classes of antiretroviral therapy.

The objectives are to study the feasibility, safety and efficacy of sequential combination therapy in HIV-1 infected patients with virus harboring genotypic resistance to at least three classes of antiretroviral agents and who currently have no adequate treatment options available.

This is an open-label, crossover, pilot study. Patients that fail their current regimen, and who currently have no adequate treatment options left, will be randomized to start either an alternating triple combination, or to start a continuous quadruple regimen of drugs. After 6 weeks, patients will crossover from either strategy to the other strategy for another 6 weeks. Each period is preceded by an interruption of all antiretroviral therapy for 4 weeks. In the study period when regimens are alternated, two combinations of three drugs with the least possible cross-resistance will alternate every week.