Microarrays get their 15 minutes, but routine use still 10 years away

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June 10, 2003 — The U.S. Centers for Disease Control and Prevention recently released its latest test for the SARS virus, but it will be another decade before microarray technology brings quick, accurate tools for detection of this and other viruses directly to the doctor’s office.

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Current tests for Severe Acute Respiratory Syndrome use a technology called polymerase chain reaction (PCR) — a technique for replicating DNA. PCR tests are cheap, often less than $10, and effective for many basic types of fluid tests, but microarrays had a brief moment in the spotlight when researchers in the DiRisi Laboratory at the University of California, San Francisco used the devices to quickly identify the virus that causes SARS

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Microarrays, which combine MEMS and fluidics to allow fast, accurate tests of diseases, were conceived in 1993, by Stanford’s Pat Brown, who counts Joseph DeRisi among his students. Now, the phone calls keep coming to DeRisi’s lab. The easy calls come from other researchers, or journalists. The heartbreaking ones come from people with mystery ailments, hoping the lab can give them some answers.

“They want us to sample them,” said David Wang, one of the DeRisi Lab’s star researchers. Labs aren’t allowed to perform random work on human samples, so those callers end up disappointed.

SARS made a star out of microarrays. But fame doesn’t necessarily lead to fortune, and that’s true for this still developing technology.

SARS “is evolutionary, not revolutionary” for the industry, said Greg Yap, senior director of marketing for DNA products at Affymetrix Inc. in Santa Clara, Calif. Yap said microarrays will continue to sell primarily into research labs, even in the wake of SARS. That hasn’t stopped Affymetrix from releasing a SARS-labeled version of its GeneChip family. But the big growth opportunities in the short term will probably come from DNA analysis, Yap said. The field is new enough, though, that “we don’t know for sure what our second and third and fifth and 50th applications will be.”

The Holy Grail for the industry is seeing microarrays used in doctors’ offices to diagnose patients, something that is perhaps a decade away.

“For a quick screen, you don’t want a microarray. You want something that costs a few cents,” said Felicia Gentile, president of BioInsights, a biotech consulting company in Cupertino, Calif. Gentile estimates the microarray business will grow about 12.5 percent in the next two years, from $400 million in 2003 to $450 million in 2004. Affymetrix has about 70 percent of the market.

While microarrays generate faster, more accurate results than typical PCR tests, a microarray costs several hundred dollars. Microarrays also generate significant amounts of data, which must be interpreted. A PCR generates a quick yes/no answer to the question, “Does this patient have a specific disease?”

The main value of microarrays comes from their ability to run multiple tests at once. The SARS samples were tested against hundreds of known virus types on a single microarray, then analyzed. That ability makes the devices useful for tracking the genetic mutations of a virus, for instance, which helps scientists understand the virus and may help in developing drugs to battle the diseases.

The lack of an immediate mass market potential doesn’t mean there aren’t firms trying to take advantage of the microarray’s moment in the spotlight. CombiMatrix Corp., a unit of Acacia Research Corp., has generated multiple news releases touting its SARS-related microarray advances, including one saying it had synthesized SARS-specific interfering RNA, offering hope for drug development.

Ali Ajormand, a senior scientist at the Mukilteo, Wash., firm, said that any move past research labs will be at least two to three years away. He thinks microarrays will follow a path similar to that of PCRs, which spent years as a pure research tool before finally finding a use in diagnostics. “In 10 years, you may see microarrays routinely used for diagnostics,” he said.

Making that market leap will depend more on companies like Roche Pharmaceuticals, which is working with both Affymetrix and CombiMatrix to develop new types of tools based on microarrays, including hybrids that also contain PCR tests. Roche’s versions of the Affymetrix chips will roll out over the next 18 months. But the cost issues will remain significant for some time.

Microarrays are still new enough that different methods of manufacturing them are being developed. For instance, GeneFluidics Inc., a startup in Monterey Park, Calif., is using plastic injection modeling instead of glass to make its microarrays.

Microarrays remain somewhat exotic even in research labs. Wang noted that even the DeRisi Lab’s basic work was only published last November. “We’ve only had a few months to play with it. We’re really just getting started,” Wang said.

The lab has put together a microarray with every known sequenced virus on it, which it will use to look for new kinds of viruses. In the process, it may be able to solve some of the mystery ailments that afflict its callers. Then the phones may really start ringing off the hook.


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