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OGT Using Protein Array Platform to Develop Prostate Cancer Test, Plans Clinical Study

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By Justin Petrone

Oxford Gene Technology has identified a panel of biomarkers it claims can be used to distinguish individuals with prostate cancer from both normal individuals and those suffering from other diseases of the prostate.

The company last week presented preliminary data on the panel at the American Association for Cancer Research's International Conference on Molecular Diagnostics in Cancer Therapeutic Development, held in Denver. After screening 73 prostate cancer samples and 60 control samples in a pilot study, the company identified a panel of markers it now hopes to expand and validate in a much larger clinical study.

The move into biomarker discovery is an expansion of activities for OGT. Founded in 1995 to protect the patent estate of inventor Edwin Southern, OGT in recent years began offering products and services in a number of research areas, particularly cytogenetics.

OGT's new prostate cancer diagnostic panel is being developed with the functional protein array technology that the UK company gained through its acquisition of Sense Proteomic last year (BAN 3/17/2009).

John Anson, director of OGT's year-old biomarker-discovery business unit, said that the prostate cancer program is a continuation of work that was underway at Sense Proteomic prior to the acquisition.

Anson told BioArray News this week that one of the reasons that the firm acquired Sense Proteomic was its own desire to move OGT's traditionally research-oriented business into biomarker discovery and, eventually, molecular diagnostics.

"When we looked at Sense as a potential acquisition target, we were very interested in the application of the technology for biomarker discovery," Anson said.

Building on its preliminary program in prostate cancer, OGT was able to develop the signature in the recent pilot study. Now it will use the protein array platform in a larger study involving 1,800 samples, up to 600 of which will be prostate cancer cases. The samples are being provided by a commercial supplier.

The control group of approximately 1,200 samples will include "a whole group of interfering diseases such as prostatitis and benign prostatic hyperplasia," said Anson. "The whole point of the study is to test whether we can identify a biomarker panel that can distinguish individuals with prostate cancer from a whole constellation of interfering diseases."

OGT said in a statement that its panel, which demonstrated 90 percent sensitivity and specificity in the pilot study, could eventually replace the current standard for prostate cancer screening, which looks for the presence of prostate specific antigen in a blood sample. According to the US National Cancer Institute, only about 30 percent of men who are biopsied following a PSA screen actually turn out to have cancer. The rest are false positives.

According to Cancer Research UK, prostate cancer is the most common form of cancer among males in the UK, with 36,000 cases reported in 2007. The National Cancer Institute estimates that more than 217,000 cases of prostate cancer will be reported in the US this year, making it the second most common form of cancer among American males.

Results from the follow-on study are due in the first half of 2011. Anson said that OGT is assessing partnership opportunities with diagnostic and pharmaceutical companies for the development of a test. It is unclear if OGT's protein array platform will be used in the final test, should it come to market.

The company wants its diagnostic to be platform-agnostic, said Anson. "It could be an array, but that may not be most effective and convenient format," he said, adding that some partners might want to transfer the panel to their existing platforms, such as enzyme-linked immunosorbant or bead-based assays.

Biomarker Discovery

OGT's main protein biomarker discovery tool is its Sense Proteomic functional protein array platform. Sense arrays contain over a thousand correctly folded proteins and can be used to detect autoantibodies in serum samples.

To make the arrays, each protein is expressed in insect cells as a fusion protein with a proprietary biotin carboxyl carrier protein tag, which monitors correct folding, according to OGT. This means that only functional proteins are immobilized on the array surface with native epitopes presented, which are readily accessible to assay reagents and autoantibodies.

"The way that these proteins are expressed and attached retains functional folding," said Anson. "It will present every opportunity for the autoantibody to bind to the surface of that protein."

In addition to its prostate cancer program, OGT is using its Sense Proteomic platform to identify biomarkers for colorectal cancer, non-small cell lung cancer, and systemic lupus erythematosus. The company has positioned its protein array platform for pharmaceutical companies to monitor immune modulation to therapeutic intervention during clinical trials.

In parallel to its protein array-based discovery programs, OGT is also using its oligonucleotide arrays to develop genomic biomarkers, Anson said. In terms of DNA array-based research programs, he said that OGT is mainly focused on prostate cancer and colorectal cancer.

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