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Privately held molecular diagnostics firm Source MDx Inc. is partnering with Pfizer Inc. in a multiyear collaboration to develop RNA-based biomarkers for Pfizer's cancer and inflammatory disease pipelines, with the goal of creating companion diagnostics to be marketed in tandem with targeted drugs.

It's a space that has been getting a lot of attention lately. In fact, it was New York-based Pfizer that had one of the recent success stories with the summer approval of HIV viral entry inhibitor Selzentry (maraviroc), a drug designed specifically for adults infected with only CCR5-tropic HIV-1 who have evidence of viral replication and have resistant HIV-1 strains.

The success of Selzentry in pivotal trials hinged on the use of an HIV co-receptor tropism assay developed by South San Francisco-based Monogram Biosciences Inc. to screen patients for enrollment, and the two firms are working together to make Trofile available commercially for screening and monitoring patients taking Selzentry.

And Pfizer's not alone in its interest in companion diagnostics. "Most of the major pharmas have announced that they intend to get into this area," said Karl Wassermann, president and CEO of Boulder, Colo.-based Source MDx, which has developed and patented its Precision Profiles, molecular diagnostic assays for more than 1,800 target genes based on RNA transcript measurement using quantitative RT-PCR.

Since the company began operations in 1999, its technology has been used in more than 150 preclinical and clinical trials for more than 30 pharma firms, Wassermann said.

Source MDx has worked with Pfizer since 2002, applying RNA transcription profiling to the pharma firm's drug development process in inflammatory diseases such as rheumatoid arthritis. Since then, "what we've done as a company is invested heavily" in the development of oncology biomarkers, Wassermann told BioWorld Today.

The firm worked with the Dana-Farber Cancer Institute in Boston to create molecular diagnostics in cancers, including breast, cervical, colon, lung, ovarian, prostate and skin cancer.

In the Pfizer deal, Source MDx will apply its technology in clinical studies for Pfizer drugs in development for both oncology and inflammation. In exchange, Pfizer will make an equity investment in Source MDx, and will pay a technology license fee and provide research and development funding for the term of the alliance. Specific financial terms were not disclosed, but the agreement includes provisions for the companies to commercialize any companion diagnostics that emerge from the collaboration.

Source MDx's technology is "based on the measurement of RNA," Wassermann said, "very precise, calibrated RNA."

The problem with other biomarker tests, such as microarrays, he said, is that the RNA might be amplified randomly, making it difficult to achieve consistent accuracy. The Precision Profile platform, however, provides "highly efficient amplification," very tight measures between genes and is "highly reproducible."

What also sets it apart from some other technologies is that is uses whole blood rather than tissue samples, which not only makes it much easier on the patients - who are able to avoid an invasive biopsy - but also provides more accurate results, Wassermann said.

"Many people focus on the tumor, but tumor tissues are very difficult to get," he said, and results could vary "depending on which part of the tumor tissue you get."

Source MDx's technology is designed to identify biomarkers in whole blood and circulating rare cells, with the aim of measuring the immune system. The idea behind it is "based on the fact that the tumor is rendering the immune system dysfunctional," Wassermann said. "A healthy person has a normal range of gene expression," so the diagnostic assays are testing whole blood to discern any abnormalities in immune function.

The Precision Profile assays essentially are intended to provide two advantages in drug development, he added. First, they aim to predict response, so that investigators and physicians can determine whether a patient would benefit from a particular targeted therapy, and second, they can be used to watch for drug resistance.

"Over time, most people develop some resistance," Wassermann said, "so we would be able to monitor and see that."

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