A DNA chip developed at Pleasanton, Calif.-based Roche Molecular Systems and approved by the U.S. Food and Drug Administration two weeks ago will usher in a new era, where genetics plays an increasingly important role in defining patient care.

“It’s a very important milestone,” said Jorge Leon, president of Leomics, a molecular diagnostics consulting firm. “Roche is taking a leadership position to pave the way.”

Roche’s test chip, known as the AmpliChip CYP450, focuses on two enzymes that can strongly influence how the body responds to many drugs. The idea behind the chip is to determine whether a patient processes drugs at a normal, slow or fast rate. In this way, doctors can more easily prescribe appropriate medications and dosages.

For example, if someone processes drugs slowly, they will likely do better on a lower dosage. A higher dose may work better for a patient who processes drugs quickly.

This biology has been well understood for a while, but until now, there has been no simple way to screen for differences.

Instead, doctors have traditionally relied on trial and error. The majority of patients might respond well to the recommended dosage. However, a minority would not, experiencing bad side- effects, or not seeing any benefits.

Among Caucasians, about 8 percent process the affected drugs slower than normal. Roche has also found that about 4.5 percent of African-Americans and Latinos process the drugs much faster than the normal rate.

The size of a thumbnail, the AmpliChip contains 15,000 short stretches of DNA, representing 31 genetic variations in two enzymes that belong to a family of genes called cytochrome P450.

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