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Rosetta Puts Blood-Based Cancer Screen on Back Burner to Refocus on miRNA Diagnostics

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By Doug Macron

Rosetta Genomics this month announced that it has scaled back its work on a serum-based colon cancer-screening assay based on microRNA biomarkers, less than a year after the company said that commercialization of the test, dubbed miRscreen Colon, had become its top priority.

The news, which was disclosed with the release of Rosetta's third-quarter financial results, wasn't a complete surprise given the general difficulties in measuring and interpreting blood-borne miRNA signatures, as well as the firm's own admission in September that "technical obstacles" had been stymieing its efforts to develop the screen.

"The results we have seen in our colon cancer studies in serum over the past several months suggest that we will not be able to bring to market a competitive serum-based colon cancer-screening assay," Rosetta President and CEO Kenneth Berlin, who replaced former top executive Amir Avniel in November (see RNAi News, 11/5/2009), said in a statement. "While we continue to work on a colon cancer screening test in other blood compartments, we've recently determined that a colon cancer-screening test will not be a priority project at this time."

Instead, Rosetta has moved three new miRNA-based tests to the head of its product pipeline, including a second-generation version of its cancer-of-unknown-primary-origin diagnostic miRview Mets, expected to be available in the second half of 2010; a fine needle aspirate test to classify non-small cell lung cancer as either squamous or non-squamous, slated for commercialization in the second half of 2011; and a test to predict the risk of superficial bladder cancer becoming invasive, which is expected to reach the market in late 2011.

The two other tests were not disclosed.

"Since joining Rosetta Genomics … I have been reviewing our commercialization strategy, technology, and research capabilities," Berlin added. "I believe the five products we have decided to advance ahead of the colon cancer test represent a more compelling and differentiated product offering, and therefore better position us for success."

Though it was founded as a developer of both miRNA diagnostics and drugs (see RNAi News, 11/4/2005), Rosetta has been steadily transitioning away from the therapeutics space and now characterizes itself strictly as a "molecular diagnostics company."

By the end of 2008, Rosetta had brought to market three miRNA diagnostics: miRview Meso, which differentiates lung cancer from mesothelioma; miRview Mets, which is designed to determine the source of cancers of unknown primary origin; and miRview Squamous, which is designed to differentiate squamous from non-squamous non-small cell lung cancer.

But early the next year, the company announced that it had shifted its focus away from diagnostics onto screening assays, with miRscreen Colon as its lead product candidate.

"Screening tests target millions of healthy individuals and … therefore, potentially hold enormous … financial impact on our company," Avniel said at the time, adding that the colon cancer test was expected to reach the market before the end of this year.

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A few months later, however, Avniel said that the expected launch date for miRscreen Colon had been pushed back to mid-2010 as Rosetta encountered difficulties in consistently measuring miRNA biomarkers in serum (see RNAi News, 9/10/2009).

Avniel said at that time that these "technical obstacles" were likely the result of inconsistencies in the way serum samples are obtained and that Rosetta was reviewing protocols related to how blood samples are obtained and handled.

But based on comments from one key figure in the miRNA space, the issues Rosetta faced with miRscreen Colon may be more fundamental.

According to University of Massachusetts Medical School investigator and miRNA pioneer Victor Ambros, the phenomenon of miRNAs in circulation remains "mysterious," and their meaning "still pretty obscure.

"There are hundreds of them that can be detected in human plasma," he told RNAi News earlier this month. "It's just not clear what they represent. A portion of those could represent debris from cells that are being turned over in one part of the body … and being taken through the circulation to be filtered out through the liver or kidney."

Another possibility is that "some fraction of microRNAs may be in packaged form that really is produced in one part of the body to be sent to another part, perhaps as a signal to other cells," he noted. But "these are broad hypotheses that have yet to be tested."

While Ambros is optimistic about the potential to use miRNAs in the blood as biomarkers of disease, "the field is at the very early stages.

"We … need to learn more about the biological meaning of these circulating microRNAs," he said. "What is their physical form, where do they come from, how are they produced, what is the range of particles and their sources and their destinations that are present in circulation? It's amazingly uncharacterized at the moment."

Third Quarter

For the three-month period ended Sept. 30, Rosetta's net loss rose to $3.4 million, or $0.24 per share, from a year-ago loss of $3.1 million, or $0.25 per share.

Research and development spending in the quarter fell to $1.7 million from $2 million, while general and administrative costs increased to $858,000 from $691,000.

The company reported zero revenues in the third quarters of both 2008 and 2009.

At the end of the third quarter, Rosetta had cash, cash equivalents, short-term bank deposits, and marketable securities totaling $13.5 million.

Looking ahead, it said that it expects its monthly cash burn during 2010 to be roughly $900,000. "However, this may change significantly based on a number of factors, including our current assumptions of revenues and royalties from sales of our three marketed products, as well as the availability of other potential sources of cash," Rosetta noted.

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