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Myriad Genetics Launches Molecular Diagnostic Test

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Myriad Genetics, Inc. announced that it has introduced a new product, TheraGuide 5-FU™, to help predict which cancer patients are likely to suffer serious toxic reactions to the drug 5-Fluorouracil (5-FU) or the oral form of the drug, capecitabine.

More than 500,000 Americans with breast cancer, colon cancer, skin cancer or head and neck cancer are treated with 5-FU each year. Approximately 30% of those patients experience severe toxicity.

TheraGuide 5-FU is analysis of the genetic variations in two genes, DPYD and TYMS, which increase a patient's risk for toxicity to 5-FU chemotherapy. With the TheraGuide 5-FU test results, oncologists and their patients can take steps to reduce the risk of avoidable toxicity, including using alternative therapies, reducing the size of the dose and increasing patient monitoring for side effects.

TheraGuide 5-FU can provide the critical guidance oncologists need to personalize chemotherapy for their cancer patients who are being considered for chemotherapy regimens.

"TheraGuide 5-FU is a new personalized medicine test that has the potential to save many cancer patients from serious toxic reactions to the medicine that is supposed to help them," said Greg Critchfield, M.D., President of Myriad Genetic Laboratories, Inc. "TheraGuide 5-FU points the way to the future promise of personalized medicine, where tests can guide the therapeutic choice for improved patient care, while limiting the side effects of otherwise efficacious drugs."

Approximately one third of all patients given 5-FU will experience dose-limiting toxicity that can be severe to life-threatening. The majority of these toxic reactions are due to genetic variations in the DPYD and TYMS genes. The DPYD gene makes the enzyme that is primarily responsible for metabolizing or breaking down 5-FU and clearing it from the body quickly.

If the DPYD enzyme activity is compromised, 5-FU will be cleared more slowly from the system resulting in a longer period of exposure to 5-FU and a subsequent increased risk for toxicity. An estimated 9 million individuals in the U.S. have low DPYD enzyme activity due to mutations in the DPYD gene.

Thymidylate synthase (TYMS) is an essential enzyme for DNA synthesis. The chemotherapy drug, 5-FU, binds to the TYMS enzyme, inhibiting its function. When the TYMS enzyme is inhibited, DNA synthesis does not go forward and the cell dies. Since cancer cells multiply rapidly, requiring a high level of DNA synthesis, they are much more sensitive to thymidine depletion than normal cells.

TheraGuide 5-FU is Myriad's fifth molecular diagnostic product. The Company is now accepting samples for testing with TheraGuide 5-FU. The test cost is $1,100 and includes a comprehensive DNA sequence analysis of the DPYD gene and the important variations in the TYMS gene. The result is returned to the requesting physician within seven days of receipt at Myriad.