Therapeutic options for treatment experienced patients: a focus on resistance testing and optimizing background therapy.

Antiretroviral therapy may fail to achieve virologic suppression for a variety of reasons. When failure occurs, treatment regimens and goals must be carefully reassessed. Even with extensive multiclass resistance, most treatment-experienced patients benefit from continuing or switching regimens rather than discontinuing therapy entirely. Selection of a new treatment strategy is influenced by the presence of resistance mutations; therefore, resistance testing is a crucial part of designing a new antiretroviral regimen. Various clinical trials have confirmed the benefit of such testing and the advantages of individualized and optimized regimens. However, some highly treatment-experienced patients may have few or no remaining treatment options and pose a major challenge to disease management. The development of new agents will be necessary to create highly effective regimens for patients with complicated resistance patterns.