When the human genome project was completed five years ago, many experts predicted that personalised medicine would swiftly follow

When the human genome project was completed five years ago, many experts predicted that personalised medicine - drugs and dosages tailored to specific patient groups - would swiftly follow. In fact, the technology has been slow to arrive. But Swiss manufacturer Roche claims that its new microarray test is the first of its kind to detect genetic variations that influence drug response.

Physicians can use the test to analyse genes encoding the enzymes of the cytochrome P450 (CYP) complex. There are about 50 different CYPs in man, which play a key role in toxin and drug removal.

The AmpliChip CYP450 test assays a patient’s CYP2D6 and CYP2C19 genotypes; two key regions encoding the enzymes of the CYP complex. Variations in the CYP2D6 gene influence the metabolism of numerous drugs, including anti-depressants, anti-psychotics, anti-arrhythmics, beta-blockers, pain medications, anti-emetics and some anti-cancer treatments.

The CYP2C19 gene has implications for metabolism of anti-convulsants, proton pump inhibitors, benzodiazepines and anti-malarials, amongst others.

The AmpliChip combines Roche’s polymerase chain reaction amplification technology to boost detection levels of genetic material, and high-density thumbnail-sized microarrays provided by Affymetrix, each with tens of thousands of DNA fragments.

’This new test allows physicians access to information that could help to prevent harmful drug interactions and to assure drugs are used optimally,’ said Heino von Prondzynski, divisional chief executive officer of Roche Diagnostics. Patients will also be able to steer clear of less effective or harmful treatments, he added.

In a separate development, Cambridge, UK-based Astex Technology has patented the crystal structure of human cytochrome P450 3A4. Around 50 per cent of all drugs are thought to interact with this form of cytochrome P450. Astex chief executive Timothy Haines said: ’The insights provided by the crystal structure of cytochromes P450 should improve the success rates and economics of drug development and result in safer and more effective new medicines.’

Helen Carmichael