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FDA Clears Pathwork Diagnostics' Tissue-of-Origin Test for Use with FFPE Samples

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By Justin Petrone

This article has been updated from a previous version to correct the company's name, which was erroneously reported in the second and third paragraphs.

The US Food and Drug Administration has cleared Pathwork Diagnostics' tissue-of-origin test for use with formalin-fixed, paraffin-embedded tissues, the company said this week.

The FDA originally cleared the Affymetrix-manufactured test in 2008 for use with frozen tissue samples, and Pathwork has been offering the TOO assay with FFPE samples as a lab-developed test since 2009.

"The FDA clearance demonstrates our ability to develop and commercialize robust FFPE diagnostics" and will "open the door for future tests to be offered on the Pathwork platform," Pathwork CEO Deborah Neff said in a statement this week.

Shawn Becker, vice president of marketing for the firm, told BioArray News this week that the TOO test for FFPE samples uses a different gene signature and algorithm from the TOO test for frozen tissue samples.

Pathwork, based in Redwood City, Calif., said it will now offer the TOO assay for FFPE tissue to community and research hospitals and will perform the test in its Clinical Laboratory Improvement Acts-certified lab. It will also make an IVD kit available to customers who want to run the test on FFPE samples in their own clinical labs.

Becker said that kit commercialization timing has "not been finalized but the first phase should begin later this year." He said the LDT version of the test is "functionally equivalent" to the IVD version, but that the transition entails "ensuring Pathwork's systems are in place to enable compliance with FDA requirements."

Pathwork in April 2008 began running the test on frozen tissue samples as an LDT in its CLIA lab, and began providing IVD kits upon receiving FDA clearance later that year (BAN 8/5/2008). The test compares the expression of more than 1,500 genes in a tumor sample against 15 known tissues that represent more than 60 morphologies.

Pathwork claims the test can provide an objective, probability-based score for each potential malignancy. The test is meant to be used with the patient's clinical history and complementary diagnostics, such as immunohistochemistry.

Neff said that Pathwork has seen "significant adoption" of its tests over the past two years from "leading oncologists and pathologists" at institutions such as MD Anderson Cancer Center and the University of Pittsburgh.

In 2008, she told BioArray News that Pathwork had been developing several other tests for use on frozen tissue and FFPE tissue, and was focused on "three or four large areas of oncology that you might expect us to be working on" (BAN 8/5/2008). The firm has not publicly discussed other potential indications since that time. Becker this week declined to provide more detail on the company's pipeline.

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