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DxS Hoping to Invite Companion Dx Opportunities by Developing Blood-based Genetic Tests with Exosome

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By Turna Ray

In collaborating with Exosome Diagnostics to expand the market for its Scorpion RT-PCR Mutations Test Kits, UK-based DxS is hoping to attract more pharmaceutical partners in developing companion diagnostics for cancer therapies.

Tests kits from DxS' Scorpion brand are used to detect cancer gene mutations, such as KRAS, BRAF, and EGFR. Under the partnership announced this week, DxS' RT-PCR technology will be joined with Exosome Dx's xOSO technology — which collects nucleic acids from blood exosomes — to develop blood-based companion diagnostics for detecting cancer gene mutations.

"Combining the ability to pull high-quality mutations from a simple blood draw with … our Scorpion assays will provide our pharmaceutical and research customers with an ideal solution in personalized medicine" Stephen Little, DxS CEO, said in a statement.

DxS already has experience developing companion diagnostics in concert with a major drug developer in launching its TheraScreen KRAS Mutation Test Kit as a companion diagnostic for Amgen's colorectal cancer monoclonal antibody Vectibix.

The KRAS test, distributed worldwide by Roche Diagnostics, is currently under review at the US Food and Drug Administration. The agency is considering whether to update the labels of Vectibix and Bristol-Myers Squibb's Erbitux with a recommendation that only colorectal cancer patients with tumors carrying the wildtype KRAS gene receive these drugs [see PGx Reporter 03-04-2009].

Specifically, DxS expects the partnership with Exosome Dx to broaden the market for its mutation detection kits into other types of cancer, where tissue sample acquisition is not possible. "Blood-based mutation measurement is particularly valuable in circumstances where tissue bioavailability is limited, such as in lung, pancreatic, and ovarian cancers," DxS said in a statement.

This added capability will particularly assist DxS in its latest Rx/Dx partnership to develop a companion diagnostic test kit for Boehringer Ingelheim's BIBW 2992 (Tovok) drug candidate that can identify mutations of the epidermal growth factor receptor in patients with non-small cell lung cancer.

According to Exosome Dx CEO James McCullough, the detection kits being developed under the collaboration may be potentially useful in investigating the pharmacogenomics of the more than 370 targeted cancer compounds currently under investigation at more than 180 companies. McCullough believes that many of these investigational agents may require molecular companion diagnostics.

"Teaming with the world leader in this space is a critical step in providing a solution for pharmaceutical companies, researchers, and clinicians to measure the key mutations DxS Scorpion probes target directly from blood," McCullough added.

The partners will focus on developing blood-based measurement of KRAS, BRAF, EGFR, and other mutations for predicting patient response to targeted therapies.

Under its companion diagnostic development program, DxS currently markets several research-use-only assays for detecting mutations in KRAS, EGFR, BRAF, P13K, T790M, and T3151 BCR-ABL. The company is also developing new assays, which can be customized to detect a biomarker of interest that relates to a new therapy.

Exosomes are microvesicles shed by all solid tumors into blood and contain virtually the entire cancer tumor transcriptome. In studies, Exosome Dx has identified over 21,000 mRNA and 1,100 miRNA in circulating tumor-derived exosomes, all protected in the exosome lipid bilayer from any blood-based RNase, according to a statement from the partners. Initial findings from these studies were published in the December issue of Nature Cell Biology.

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