Effect of zidovudine resistance mutations on virologic response to treatment with zidovudine-lamivudine-ritonavir: Genotypic analysis of human immunodeficiency virus type 1 isolates from AIDS Clinical Trials Group Protocol 315

The effect of baseline drug resistance mutations on response to zidovudine, lamivudine, and ritonavir was evaluated in zidovudine- experienced persons infected with human immunodeficiency virus type 1 (HIV- 1). Presence of the K70R mutation was associated with significantly higher plasma HIV-1 RNA levels at baseline. However, presence of resistance mutations did not affect the increase in plasma HIV-1 RNA during a 5-week drug washout, nor was there any effect on first-phase virus decay rates after initiation of therapy or on the probability of having plasma HIV-1 RNA levels <100 copies/mL at week 48. Polymorphisms at protease codons 10, 36, and 71 were associated with significantly faster second-phase decay rates. Suppression of plasma HIV-1 RNA despite presence of zidovudine resistance mutations implies that the presence of these mutations does not preclude a durable response to treatment with a potent 3-drug regimen.