Study on mutations and antiretroviral therapy (SMART): preliminary results

Resistance to antiretroviral drugs is believed to be an important cause of treatment failure in human immunodeficiency virus (HIV)-infected patients, however, the role of susceptibility assays in the management of these indiv iduals needs to be defined. SMART (study on mutations and antiretroviral th erapy) is an ongoing study on mutations and antiretroviral therapy focused particularly on HIV-infected patients treated with two nucleoside analogue reverse transcriptase inhibitors (NRTIs). Plasma HIV-1 RNA was assessed by NASBA (nucleic acid sequence-based amplifications) (Organon Teknika, Boxtel , The Netherlands) with a detection limit of 80 copies/ml, whereas resistan ce was assessed by direct sequencing of the RT pol gene in patients with de tectable viraemia, and by Antivirogram (Virco) in non-responder patients. T he preliminary results of this study show that both genotypic and phenotypi c assays identify mutated viral strains in the majority of patients failing a dual regimen. Furthermore, the data indicate a high rate of genotypic re sistance to lamivudine in both responders and nonresponders, a high rate of phenotypic resistance to lamivudine in non-responders, no genotypic resist ance to didanosine and stavudine in responders, and a very low rate of both genotypic and phenotypic resistance to didanosine and stavudine in non-res ponders.