The world's first gene chip has been launched for pharmacogenomics, personalized medicine that uses a person's genetic constitution to guide drug treatment.
Switzerland's Roche Holding, the world's largest diagnostic company, will introduce the chip first in the US and then in Europe following expected approval by American and European regulatory authorities.
Called the AmpliChip CYP450, the product enables clinical diagnostic laboratories to identify variations in two genes that play a major role in drug metabolism.
The two genes, CYP2D6 and CYP2C19, affect the rate that people metabolize drugs used to treat such diseases as depression, high blood pressure, attention deficit hyperactivity disorder and heart disease.
Metabolism important in drug treatment
Roughly 10% of Caucasians and 20% of Asians are poor metabolizers of drugs, while smaller populations of people are fast metabolizers.
Both groups are at risk if given standard doses. Poor metabolizers are at risk of retaining medication for too long, while fast metabolizers are in danger of not retaining medication long enough to receive any therapeutic value.
"There is an increasing awareness of the important role these two genes play in metabolizing an estimated 20% to 25% of drugs already on the market," says Greg Heath, head of Roche Molecular Diagnostics Clinical Genomics Business. Targeting use of these drugs, as well as development of new drugs, to those who can most benefit from them represents an important opportunity for improving therapeutic value, reducing healthcare costs associated with a more time consuming trial-and-error approach and improving the patient's overall experience with the chosen therapy."
Such targeting will allow physicians to be better equipped to select the right drug and dose for a patient sooner while avoiding guesswork with medications that might cause adverse reactions.
Several factors require that physicians move beyond the one-size-fits-all approach to prescribing medication. These include the high percentage of people who fail to benefit from many drugs currently on the market and adverse reactions to prescribed drugs.
In the US alone, adverse drug reactions account for an estimated 100,000 deaths each year.
The AmpliChip
AmpliChip microarrays include thousands of DNA sections, called probes, that are assembled on glass plates the size of a thumbnail.
DNA is extracted from a sample, labeled with fluorescent dye and applied to the microarray. Genes represented in the sample will bind with any DNA pieces on the microarray. The area where the binding occurs is made visible through laser technology.
An AmpliChip test will initially cost between US$350 and US$400.
source: http://www.betterhumans.com/News/news.aspx?articleID=2003-07-02-3 3jul03
Background Information
MICROARRAY ("DNA CHIP") AND ROCHE AmpliChip™ CYP450 BACKGROUNDER
A microarray or "DNA chip" is an orderly arrangement of synthetic stretches of DNA attached to a rigid flat surface, such as a microscope slide. Each spot contains a specific sequence of DNA, usually less than 60 bases long. AmpliChip™ microarrays, powered by Affymetrix technology, use photolithography and solid phase chemistry. Each microarray contains hundreds of thousands of oligonucleotide probes packed at extremely high densities. The entire chip is no larger than a human thumbnail. This DNA chip technology allows researchers to selectively identify particular gene sequences and their variations or mutations. A tiny amount of DNA is required for analysis. This can be obtained from a small amount of blood or even a gentle swab from the inside of one's cheek. However, the DNA then needs to be amplified, usually by PCR (Polymerase Chain Reaction) technology developed by Roche Molecular Diagnostics. PCR allows specific gene regions to be selectively amplified from minute amounts of genetic material into billions of copies in just a couple of hours.
Roche Diagnostics' AmpliChip CYP450 is the first wide-scale application of diagnostic microarray technology in the world. AmpliChip CYP450 can identify naturally occurring genetic variations or common mutations in two specific genes, CYP2D6 and CYP2C19, members of the cytochrome P450 gene family. Common variations in these genes play a crucial role in determining how a person can process or metabolize many of the drugs used for the most common conditions including analgesics, antidepressants, antihistamines, heart and blood pressure medications, antidepressants and antipsychotics.
Roche Grenzacher Strasse Divisional Communications Phone +41 61 688 3079
Diagnostics Division CH – 4070 Basel Fax +41 61 688 1054 http://www.roche-diagnostics.com
By recognizing common DNA polymorphisms or mutations in the CYP2D6 and CYP2C19 genes, DNA chips can determine if a person is a poor metabolizer (PM) or an ultrarapid metabolizer (UM). PMs have trouble inactivating certain drugs and eliminating them from the body. Generally, a PM is at increased risk for experiencing adverse drug reactions, toxicities and even dangerous side effects of therapies.
UMs, on the other hand, with additional functional copies of the genes, have an increased risk of being a nonresponder because they can inactivate and eliminate a drug before the drug has had a chance to achieve its therapeutic effect. With the launch of AmpliChip CYP450, it is hoped that CYP450 genotyping can be used in the clinic to assist in therapeutic decision-making with the goal of prescribing drugs that are optimally effective and safe for the individual. Currently, Adverse Drug Reactions (ADRs) in US hospitals are responsible for more than 100,000 deaths nationwide each year making it one of the leading causes of death. 1 Each year, more than two million hospital patients experience a serious ADR in the US, representing a significant burden on healthcare systems and costs.
1. JAMA. 1998; 279: 1216-1217, Pomeranz, MD, PHD
Roche Grenzacher Strasse Divisional Communications Phone +41 61 688 3079
Diagnostics Division CH – 4070 Basel Fax +41 61 688 1054 http://www.roche-diagnostics.com
source: www.roche-diagnostics.com/media/pdf/press_release/2003/background_amplichip_450.pdf (0PDF-File - 49 KB) 3jul03
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