Abstract Body

The World Health Organization recommends abacavir (ABC) as the preferred/alternative backbone for 1st line regimens in children with HIV from age 28 days. There are limited data available on safety and tolerability of ABC in young infants aged <3 months.

All children in the European Pregnancy and Paediatric HIV Cohort Collaboration (EPPICC) who initiated ABC aged <3 months between 2000-2016 were included. We describe infant and regimen characteristics at the start of ABC (including drug combinations and dosing) and outcomes up to 12 months after first use of ABC. Outcomes include drug discontinuations (defined as interruption of treatment for >30 days), clinical adverse events (AE, reported from start of ABC up to 30 days after discontinuation) and viral suppression <400c/ml (VS) at 6 and 12 months of treatment for children who remained on ABC.

Of 498 children in EPPICC who received antiretroviral therapy (ART) whilst aged <3 months, 139(28%) received an ABC-containing regimen (n=20 aged<28 days) and were followed for median 4.6 [IQR 1.5,9.7] years. Median year of birth was 2010 [2006,2012], age at HIV diagnosis was 39 [11,62] days and 84(60%) were female. 53(38%) were from UK and Ireland, 23(17%) Ukraine, 19(14%) Spain, 14(10%) Russia, 12(9%) Belgium and 18(13%) elsewhere in Europe. 63(45%) received post-exposure prophylaxis (PEP) prior to ABC-based treatment (4 PEP regimens included ABC, with the ABC continuing following HIV diagnosis). 54(39%) were taking ABC with lamivudine and lopinavir/ritonavir and for 44 infants with ABC dosing/weight data available, 30(68%) started on an 8mg/kg twice daily (BD) dose (Table).
Overall 66/92(70%) and 59/77(77%) on ABC-containing regimens had VS after 6 and 12 months, respectively. During the first 12 months on ABC, AEs were reported in 8 infants with 4 events leading to discontinuation of ABC, all occurring within the first 7 days of treatment (Table). By 12 months after start of ABC, cumulative incidence of discontinuation of ABC due to a safety concern was 3.6% (95% CI 1.4,7.8%).  A further 11 infants discontinued ABC for other reasons (5 of 11 later restarted ABC) and the cumulative incidence of any discontinuation by 12 months was 11.8% (7.3,18.9%). There were no deaths reported during follow-up.

ABC is safe and well tolerated in infants, with rare discontinuations for safety concerns, supporting WHO treatment recommendation. More data on ABC use are required in neonates.