A 'gene chip' test that helps predict how people will react to certain medicines has now been approved for sale in the US by the Food and Drug administration (FDA). The AmpliChip Cytochrome P450, launched in 2003 by Swiss firm Roche Diagnostics, is one of the first commercial applications of pharmacogenomics: the matching of medical treatments to a person's genetic make-up. However, the test was withdrawn from sale in the US in November 2003, following confusion over how it should be regulated.
The AmpliChip Cytochrome P450 detects variations in two genes that make key liver enzymes. Variations in the activity of these enzymes are responsible for different reactions to many commonly used drugs. Some people, classed as 'poor metabolisers', may not break a drug down quickly enough, and so could suffer side effects, whereas in 'fast metabolisers' the same drug may be broken down before it has chance to work. The test looks at the genes CYP2C19 and CYP2D6, and is sold as a DNA microarray - a thumbnail-sized glass 'chip' with DNA fragments arranged on it - made by US firm Affymetrix. The test detects the likely response to a wide range of drugs, including many anti-depressants, anti-psychotics, painkillers, beta-blockers, anti-convulsants and anti-malarial drugs.
'Physicians can use the genetic information from this test to prevent harmful drug interactions and to assure drugs are used optimally, which in some cases will enable patients to avoid less effective or potentially harmful treatment choices', said Lester M Crawford, Acting FDA Commissioner. The FDA's approval of the AmpliChip Cytochrome P450 clears the way for the marketing of similar microarray-based genetic tests. The test was approved for sale in the European Union last September.