By Lisa Seachrist

Washington Editor

WASHINGTON - An FDA advisory committee unanimously endorsed approval of Vysis Inc.'s genetic test to detect and quantify HER2 gene amplification in breast cancer.

The Hematology and Pathology Devices Panel recommended the agency approve the PathVysion HER-2 DNA Probe Kit to aid physicians in determining the best therapeutic options for breast cancer patients. The company filed for approval in June.

"We received a standard review under the new guidelines," said John Bishop, president and CEO of Downers Grove, Ill.-based Vysis. "The FDA has been very good to work with."

Breast cancer patients whose tumors show an increase in the number of copies of the HER2 gene are prone to a particularly aggressive and fast-growing form of the disease. Approximately one-third of all breast cancers overexpress the HER2 gene.

Vysis presented data from a laboratory comparison study of 524 patients receiving three different doses of cyclophosphamide, adriamycin and 5-fluorouracil. All of these tumors were tested with the PathVysion kit to determine the HER2 status.

Patients without the HER2 gene amplification did not benefit from increased dosages of adriamycin. As a result, those women should be treated with the lowest dose of adriamycin in order to prevent heart damage associated with the drug. Patients with HER2 gene amplification, on the other hand, benefited from a very aggressive chemotherapy treatment plan.

Test Uses FISH Technology

The PathVysion test is significantly different from the two other HER2 gene status tests available on the market. The testing kit produced by Dako Corp., of Carpinteria, Calif., a subsidiary of Dakopatts A/S, of Copenhagen, Denmark, uses antibodies to measure the amount of HER2 on a cell surface. That test was approved in September, in conjunction with the approval of Genentech Inc.'s Herceptin, a monoclonal antibody that inactivates the HER2 protein.

Dako's test is specifically indicated for use in women who are candidates for Herceptin. The PathVysion test won't receive labeling for establishing whether Herceptin is an appropriate therapy, but some physicians may use it for that purpose.

PathVysion relies on the DNA probes directly labeled with a fluorescent marker that binds to target DNA or a particular gene within a tumor cell nucleus. The technology is called fluorescent in situ hybridization (FISH). The technology allows for a direct visualization of the gene.

Oncor Inc., of Gaithersburg, Md., has its own FISH-based HER2 test. However, Bishop pointed out that PathVysion is capable of visualizing not only the HER2 gene, but chromosome 17 during the same test. The test uses directly labeled DNA probes: The HER2 probe glows orange and the chromosome 17 probe glows green.

"It's important to distinguish between the amplification of the HER2 gene and an abnormal increase in chromosome 17," Bishop said. "That increase can be misinterpreted as an increase in HER2. The Oncor product doesn't do that."

In April, Vysis and Oncor settled a three-year patent dispute over the FISH technology, with Vysis obtaining Oncor's non-oncology FISH genetics program and Oncor agreeing to pay license fees. (See BioWorld Today, April 14, 1998, p. 1.)

Bishop said he expects the FDA to act on approval within 30 days and is preparing the product for market.

"We are ready to go from the sales and marketing perspective, and will have the test on the market almost immediately post-approval," he said.

Vysis' stock (NASDAQ:VYSI) closed Tuesday at $8.125, up $1.875. n

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