PGx abacavir

Synonyms: Abacavir Therapy, HLA-B*57:01

Material:

EDTA blood
(1 ml), buccal swab

TAT:

5-10 days

Method:

NGS, amplicon-based, SSO

Overview

Abacavir is a nucleoside reverse transcriptase inhibitor (NRTI) that is widely used as part of combination antiretroviral therapy for the treatment of human immunodeficiency virus (HIV) infection. For most patients, abacavir is an effective and well-tolerated medication. However, a small proportion of individuals may develop a potentially serious hypersensitivity reaction shortly after starting treatment.

Research has demonstrated a strong association between this adverse drug reaction and the presence of the HLA-B57:01 allele. Today, HLA-B57:01 testing is considered standard of care before initiating abacavir therapy and is recommended by regulatory agencies and international HIV treatment guidelines.

The relationship between HLA-B*57:01 and abacavir hypersensitivity is one of the best-established examples of pharmacogenetics in clinical medicine and has become a model for personalised drug therapy.

PGx abacavir

1 Gene(s)*

HLA-B

Pharmacological background

What is HLA-B*57:01?

HLA-B*57:01 is a specific variant of the HLA-B gene, which forms part of the human leukocyte antigen (HLA) system. HLA molecules play a central role in the immune system by presenting peptide antigens to T lymphocytes and helping the body distinguish between self and foreign substances.

Individuals who carry HLA-B*57:01 have an increased risk of mounting an inappropriate immune response when exposed to abacavir. This immune activation can result in a multisystem hypersensitivity syndrome that may become severe or even life-threatening if the drug is continued.

Abacavir hypersensitivity reaction

Abacavir hypersensitivity reaction (ABC-HSR) typically occurs within the first six weeks after treatment initiation, although it may develop at any time during therapy.

Common symptoms include:

Fever
Skin rash
Fatigue or malaise
Nausea and vomiting
Abdominal pain
Diarrhea
Headache
Muscle aches
Cough or shortness of breath

Symptoms often worsen with each subsequent dose of abacavir and usually improve rapidly after discontinuation of the medication.

Importantly, patients who have experienced an abacavir hypersensitivity reaction must never be re-exposed to the drug, as rechallenge can trigger a rapid and potentially fatal reaction involving hypotension, respiratory compromise, and multi-organ failure.

Genetic association

The association between HLA-B*57:01 and abacavir hypersensitivity is exceptionally strong compared with most pharmacogenetic markers.

Studies have shown that:

Approximately 5–8% of untreated patients develop clinically suspected hypersensitivity when no genetic screening is performed.
HLA-B*57:01-positive individuals have a markedly increased risk of developing hypersensitivity.
HLA-B*57:01-negative individuals have a very low likelihood of experiencing immunologically confirmed reactions.

The biological mechanism is now well understood. Abacavir binds within the peptide-binding groove of the HLA-B*57:01 molecule, altering the repertoire of peptides presented to the immune system. This triggers activation of CD8-positive T cells and initiates a systemic immune reaction.

Tested variants

Result interpretation

Test limitations

Clinical relevance

Indication	ICD-10	Gene
Adverse drug reaction	T88.7	HLA-B

References

Created by

Our editorial team consists of medical specialists and scientists in the field of human genetics. All content is created and reviewed in accordance with current scientific standards.

Last content review: August 4, 2026. As pharmacogenomic evidence and recommendations continue to evolve, the information presented on this page may not always reflect the latest updates. For current guidance and annotations, please refer to .

Last Update : 24.09.2026

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