NIH 2013

Abacavir is a nucleoside analogue reverse transcriptase inhibitor (NRTI) indicated for the treatment of human immunodeficiency virus (HIV) infection as part of a multidrug, highly active antiretroviral therapy (HAART) regimen. Despite its efficacy in treating HIV, approximately 5% of individuals that receive abacavir develop an immune-mediated hypersensitivity reaction (HSR) that warrants immediate discontinuation of abacavir and switching to an alternative antiretroviral regimen. Abacavir HSR is associated with individuals that carry the *57:01 variant in the human leukocyte antigen B (HLA-B) gene. There is a large volume of evidence to show that those who carry HLA-B*57:01 are at significantly increased risk of developing HSR and should not receive abacavir. Using pharmacogenetic screening to ensure individuals who carry y HLA-B*57:01 do not receive abacavir can reduce the incidence of abacavir HSR and is now considered the standard of care before prescribing abacavir. Genetic testing for abacavir HSR is currently one of the best examples of integrating pharmacogenetic testing into clinical practice.