Pharmacogenetics in practice
Genetic testing has dramatically reduced the number of people suffering side-effects to HIV medicines.
Abacavir is a highly effective antiretroviral treatment for HIV (the virus that causes AIDS), but around 5% of patients suffer a severe side-effect to his drug, such as rash, fatigue and diarrhoea.
The nature of the symptoms suggested that these patients were suffering a 'hypersensitivity' reaction. This means that their immune systems were overreacting to the drug. This in turn suggested that genes controlling the way that people's immune systems respond (which are in the major histocompatibility complex [MHC]) - might be responsible for the side-effects.
This turned out to be the case. In 2002, two groups identified a particular gene variant in the MHC (HLA-B*5701) as the key susceptibility factor.
Clinical trials showed that screening patients for HLA-B*5701 before treatment dramatically reduced the number of hypersensitivity reactions. Use of the test is also cost-effective.
Screening patients with HIV for HLA-B*5701 is now a routine part of clinical practice in the UK and included in HIV treatment guidelines.
