Abacavir safety and effectiveness in young infants with HIV in South African observational cohorts.

Background: WHO guidelines recommend abacavir in first-line antiretroviral treatment for children and neonates. However, there is no approved dose <3 months of age, and data in neonates are limited.

Methods: We included infants who initiated ART aged <3 months, between 2006 and 2019, in nine South African cohorts. In those who received abacavir or zidovudine, we described antiretroviral discontinuation rates; and 6- and 12-month viral suppression (<400 copies/mL). We compared infants aged <28 and ≥28 days, those weighing <3 and ≥3 kg.

Results: Overall 837/1643 infants (51%) received abacavir and 443 (27%) received zidovudine. Median (interquartile range, IQR) age was 52 days (23-71), CD4 percentage was 27.9 (19.2-38.0), and weight was 4.0 kg (3.0-4.7) at ART initiation. In those with ≥1 month's follow-up, 100/718 (14%) infants discontinued abacavir, at a median of 17.5 months (IQR 6.5-39.5). Abacavir discontinuations did not differ by age or weight category (p = 0.4 and 0.2, respectively); and were less frequent than zidovudine discontinuations (adjusted hazard ratio 0.14, 95% confidence interval 0.10-0.20). Viral suppression at 12 months occurred in 43/79 (54%) and 130/250 (52%) of those who started abacavir aged <28 and ≥28 days, respectively (p = 0.8); 11/19 (58%) and 31/60 (52%) in those who weighed <3 and ≥3 kg, respectively (p = 0.6); and 174/329 (53%) in those on abacavir versus 77/138 (56%) in those on zidovudine (adjusted odds ratio 1.8, 95% confidence interval 1.0-3.2).

Conclusion: Our data suggest that abacavir may be used safely in infants <28 days old or who weigh <3 kg.