Roche Holding AG, the world's largest maker of diagnostics, will start selling a new kind of genetic test in Europe that can help doctors find the right medicine and dose for patients to reduce the risk of side effects.

The product, AmpliChip CYP450, is the first of its kind that identifies variations in two genes that play a major role in how a patient's body absorbs many drugs used to treat heart disease, blood pressure, depression or pain, said Heino von Prondzynski, who runs Roche's Basel, Switzerland-based health tests unit.

"This is a landmark in diagnostics," von Prondzynski said. "My wife is a poor metabolizer and now we know why not all of the pain drugs in the dentist's office work."

The AmpliChip, co-developed with Santa Clara, California-based Affymetrix Inc, detects genetic abnormalities that affect sets of liver enzymes the body's main tools for breaking down a drug. People with abnormalities in these enzymes might be more likely to have bad reactions to certain medicines.

Doctors already use some genetic tests in their practices, such as one that looks for a specific abnormality in breast tumours that Roche and Genentech Inc's Herceptin cancer drug can tackle. The AmpliChip test will be conducted in a doctor's office and then sent to a laboratory for analysis.

The Affymetrix chip technology, which uses DNA fragments on a piece of glass about the size of a dime, can screen thousands of genes. Last year Affymetrix, the world's biggest maker of gene chips, introduced a new product that contains the entire human genome on a single panel the size of a thumbnail.

Roche bought rights to develop diagnostic products based on Affymetrix's microarray platform for US$70 million last year. The agreement is expected to help Roche expand in a gene-chip market Roche officials expect to be worth between US$8 billion and US$11 billion by 2014. The AmpliChip CYP450 may have annual sales of more than US$100 million in peak sales, von Prondzynski said.

"I don't expect huge sales at the very beginning," von Prondzynski said. "This is a brand-new technology and it needs a lot of education with physicians. The challenge we have is to be able to provide information to physicians about what it means if a person is a poor metabolizer."

Microarrays, also called gene chips, are tiny glass plates dotted with DNA fragments used for research. The AmpliChip test, which will cost around 400 euros (US$487), may help doctors avoid drugs that are unsuitable for a patient.

This may cut severe adverse drug reactions, which kill about 100,000 people and affect another 2 million in the United States every year, Roche says.

"Up to 70 per cent of patients don't receive the intended benefit from drugs they take," von Prondzynski said.

(China Daily 09/02/2004 page12)