Abstract Body

World Health Organization guidelines recommend abacavir as part of the preferred first line antiretroviral treatment (ART) regimen in children aged >28 days. However, there is no approved dose under 3 months of age, and with increasing access to early infant HIV diagnosis, more data are necessary to guide dosing recommendations in neonates. We describe the safety and effectiveness of abacavir in young infants in 9 South African cohorts participating in the IeDEA collaboration.

We included all infants who initiated ART (≥3 antiretroviral drugs from ≥2 classes) before 3 months of age, between 2006–2017. In those who received abacavir we described characteristics at abacavir initiation; the proportion who discontinued abacavir; and viral load suppression at 12 months. We compared infants who started abacavir aged <28 days with older infants, and those who weighed <3 kg with those who weighed ≥3 kg, in terms of abacavir discontinuations and viral load suppression, using Chi-squared or Fisher’s exact tests.

Of 1847 infants who started ART aged <3 months, 931 (50%) received abacavir: 96 were aged <28 days. At abacavir start, median (interquartile range, IQR) age was 67 days (48 to 80), CD4 percentage was 26.9 (19.0 to 37.0), viral load was 1 000 000 copies/mL (146 036 to 3 792 175), and weight was 4.2 kg (3.2 to 5.0). ART regimens included lamivudine and ritonavir-boosted lopinavir in 858 infants (92%), lamivudine and nevirapine in 9 (1%) and other antiretrovirals in 64 (7%). In those with ≥1 month’s follow-up after abacavir initiation, 61/789 (8%) infants discontinued abacavir permanently, at a median of 13.3 months (IQR 6.4 to 26.8). There were no significant differences in the proportion of discontinuations by age or weight category (p=0.6 and 0.9 respectively, Table 1). Reasons for discontinuation were documented in 20 infants (33%): non-compliance or transfer out in 11, treatment failure in 6, and hypersensitivity in 1. Viral load was measured at 12 months in 353/527 infants with ≥12 months’ follow up. The proportion of infants with viral load <400 copies/mL was 15/27 (56%) and 188/326 (58%) in those who started abacavir aged <28 days and 28 days to 3 months respectively (p=0.8); and 17/24 (71%) and 67/111 (60%) in those who weighed <3 kg and ≥3 kg respectively (p=0.4).

Half of the infants who started ART before three months of age in our cohort received abacavir. Our data suggest that abacavir may be used safely in infants <28 days old or who weigh <3 kg.