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Purpose: The treatment-emergent HIV resistance profiles were examined for children receiving fosamprenavir (FPV)-containing regimens in Studies APV20002 (age range:2 months-2 years) and APV29005 (age range:2-18 years) over 48 weeks.
Methods: HIV from antiretroviral therapy (ART)-naïve and ART-experienced (ART-e) study subjects who met virologic failure (VF) criteria by either failing to suppress (HIV-1 RNA <400copies/mL) through Wk24 or experienced confirmed rebound to >400copies/mL through Wk 48 were analyzed for treatment-emergent mutations (TEMs) or reduced drug susceptibility (RS).
Results: Through Wk 48, 25/109 (23%) APV29005 subjects and 9/54 (17%) APV20002 subjects met VF criteria (overall VF rate, 21%). Most of these subjects (17/25 and 7/9, respectively) were ART-e. Paired HIV-1 baseline and VF results were obtained for 22 subjects (15/25 APV29005 and 7/9 APV20002), 19 of whom received FPV/ritonavir (RTV)-containing ART and 3 unboosted FPV. TEMs were detected in virus from 7/15 (APV29005) and 3/7 (APV20002) subjects. Major protease inhibitor (PI) TEMS at VF included mutations or mutation mixtures at codons M46, I50, I54, Q58, V82 and I84. Virus from 5 subjects selected the NRTI mutation M184V at VF; virus from 2 subjects selected minor NNRTI mutations. HIV from 9 subjects (7/15 [47%] in APV29005 and 2/7 [29%] in APV20002) developed RS to any antiretroviral drug at VF. Of these, 4/9 subjects were ART-naïve. Three (of 4) ART-naïve subjects with any RS received unboosted FPV; all developed NRTI RS, and 2 (of 3) also developed FPV RS.
Conclusion: The overall VF rate through 48 weeks was relatively low (21%), given the high proportion of ART-e children. For subjects meeting VF criteria, most of whom were previously ART-e, 45% had virus with TEMs (although some were minor PI or NNRTI TEMs only) and 41% developed RS to ≥1 drug. TEMs were generally consistent with those observed in adults meeting VF on FPV-containing regimens.