Viro-immunological dynamics in HIV-1-infected subjects receiving once-a-week emtricitabine to delay treatment change after failure: A pilot randomised trial

Background: In HIV-1-infected patients harbouring the M184V mutation (M184V), lamivudine monotherapy leads to a smaller decrease in CD4 percentages (CD4%) than treatment interruption, possibly due to the reduced fitness of the mutated virus. Objective: We assessed whether a minimal dose of a cytidine analogue that is theoretically sufficient to maintain M184V (one emtricitabine tablet once-weekly) may be as effective. Study design: In a proof-of-concept, randomised clinical trial, HIV-1-infected patients with CD4 cells >400/mm³, failing on lamivudine- or emtricitabine-containing combination antiretroviral therapy (cART), received emtricitabine once-a-week (A), or emtricitabine once-a-day (B), or lamivudine once-a-day (C). The primary endpoint was the proportion of subjects without a 12-week loss in CD4%. The patients resumed cART after 24 weeks or in the case of CD4 cells <350/mm³. Results: The 38 enrolled patients had similar baseline characteristics across groups. The primary endpoint was reached by 5/13 patients (38.5%) in arm A, 3/13 (23.1%) in arm B, and 3/12 (25%) in arm C (P = 0.644), and respectively 4/13 (30.8%), 4/13 (30.8%) and 5/12 (41.7%) had to resume cART within 24 weeks (P = 0.805). The immunological changes over 24 weeks were similar in the three groups, but there was a higher median viral rebound in once-weekly treatment recipients (A) than in once-daily (B + C): 0.97 versus 0.52 log₁₀ copies/ml (P = 0.033). M184V was maintained in all the participants. Conclusions: Once-weekly emtricitabine led to a higher viral rebound than once-daily monotherapy, but similar immunological changes, thus suggesting a role of M184V in slowing the decrease in CD4% in treatment failing subjects.