De Luca A, et al. - In this study, the accumulation of HIV-1 drug resistance and its effect on the activity of next-line components in patients with virological failure (HIV-1 RNA >1000 copies/mL) were assessed after 1 year (t1) of first-line antiretroviral therapy (ART) not switching to second-line drugs for one additional year (t2) in low-middle income countries (LMIC). While there appeared a reduction in the activity of NNRTIs early during failure, tenofovir and zidovudine activity seemed reducing more frequently after 1 year of documented virological failure of thymidine analogue-based first-line ART, with RAMs accumulating faster in patients with higher viral loads. The present observation appeared relevant for decision making on when to switch to a second line ART in patients on virological failure in LMIC.