Changing Patterns in the Selection of Viral Mutations among Patients Receiving Nucleoside and Nucleotide Drug Combinations Directed against Human Immunodeficiency Virus Type 1 Reverse Transcriptase

Combination antiretroviral therapy (ART) has dramatically decreased morbidity and mortality among human immunodeficiency virus (HIV) type 1 (HIV-1)-infected patients through the durable suppression of viral replication to undetectable levels (22). Although ART has changed significantly in the decades since the advent of monotherapy, nucleoside and nucleotide reverse transcriptase (RT) inhibitors (NRTIs and NtRTIs, respectively) remain important foundations of therapy. The current guidelines for the treatment of HIV infection in the United States and the United Kingdom recommend dual NRTI and NtRTI therapy in combination with a protease inhibitor (PI) or a nonnucleoside reverse transcriptase inhibitor (NNRTI) for most patients (1, 3). New NRTI and NtRTI options for HIV therapy include two new fixed-dose once-daily combinations, abacavir (ABC) plus lamivudine (3TC) and tenofovir disoproxil fumarate (TDF) plus emtricitabine (FTC).