Impact of genetic variation on response to therapy
The HLA-B*5701 variant allele is associated with an increased risk of hypersensitivity reactions to abacavir. Abacavir hypersensitivity reactions are characterised by fever and/or rash with other symptoms indicating multi-organ involvement. Hypersensitivity reactions can be life-threatening and in rare cases fatal.
The SmPC for abacavir states that all patients should be tested for HLA-B*5701 prior to prescribing abacavir, and that abacavir should never be initiated in patients with a positive HLA-B*5701 status.
The British HIV Association also recommend that abacavir should only be considered for people who are HLA-B*5701 negative.
Testing recommendations
The SmPC for abacavir states that before initiating treatment with abacavir, screening for carriage of the HLA-B*5701 allele should be performed in any person living with HIV.
The British HIV Association recommends that all patients should be tested for HLA-B*5701 prior to prescribing abacavir.
Therapeutic recommendations
Carriers of HLA-B*5701 variant allele associated with increased risk of hypersensitivity reactions with abacavir:
• Abacavir should never be initiated in patients with a positive HLA-B*5701 status.
References
Dr. Reddy’s Laboratories (UK) Ltd (2023). Abacavir 300mg Film-Coated Tablets SmPC. Available at: https://www.medicines.org.uk/emc/product/10525/smpc (Accessed online 2 July 2025).
British HIV Association (2023). BHIVA guidelines on antiretroviral treatment for adults living with HIV-1 2022 (2023 interim update). Available at: https://bhiva.org/clinical-guidelines/ (Accessed online 2 July 2025.)
Clinical Pharmacogenetics Implementation Consortium (CPIC®) (2012). CPIC® Guideline for Abacavir and HLA-B. Available at: https://cpicpgx.org/guidelines/guideline-for-abacavir-and-hla-b/ (Accessed online 2 July 2025.)
