Nucleoside analogue reverse transcriptase inhibitor options: a re-examination of the class.

The main options for dual nucleoside (or nucleotide) analogue reverse transcriptase inhibitors (nRTIs) as a component of initial antiretroviral therapy regimens are tenofovir/emtricitabine, zidovudine/lamivudine, and abacavir/lamivudine as fixed-dose combinations. Resistance to nRTIs can limit usefulness of many of the drugs in the class. Investigation of triple nRTI regimens has shown that zidovudine/lamivudine/abacavir does not provide benefits compared with dual nRTIs plus efavirenz and that others (tenofovir/lamivudine/abacavir and didanosine/lamivudine/abacavir) are associated with very high virologic failure rates. Further, 4-nRTI regimens are under investigation. The article summarizes a presentation on nRTIs made by Scott M. Hammer, MD, at the International AIDS Society-USA course in New York in March 2006. The original presentation is available as a Webcast at www.iasusa.org.