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Solidus Develops 3D Cell Microarray As Low-Cost, HTP ADME/Tox Option

A team of researchers from Rensselaer Polytechnic Institute, the University of California at Berkeley, and Solidus Biosciences have developed biochip technology that could limit or make moot animal-based toxicity testing in the cosmetics, chemical, and pharmaceutical industries.
The investigators developed a miniaturized three-dimensional cell culture array, called the DataChip, to enable high-throughput screening of drug candidates, cosmetics, and chemicals, as well as their cytochrome p450-generated metabolites, according to Jonathan Dordick, a professor of chemical and biological engineering at Rensselaer.
Dordick, who is co-lead author of the group’s paper that will be published shortly in the online early edition of the Proceedings of the National Academy of Sciences, said that the DataChip comprises up to 1,080 individual 3D human cell cultures.
Dordick co-founded Solidus Biosciences in 2002 with Douglas Clark, a professor of engineering at Berkeley. He told CBA News this week that the 3D structure of the DataChip closely mimics the arrangement of cells in human organs. The cells are encapsulated in collagen or alginate gels, some as small as 20 nL, and arrayed on a glass slide.  
The DataChip is intended for use with the group’s other technology, the MetaChip, Dordick said (see CBA News, 12/26/05). The MetaChip comprises a sol-gel microarray containing one or more human p450 isoforms that generate biologically active metabolites of a candidate compound (see CBA News, 3/1/05).
“You would spot onto the MetaChip the compound that you want to test, and you would at that point put one chip on top of the other, which we call stamping,” Dordick explained.
He added that the plates would be incubated together for a short period. Investigators could then assess the toxicity of any compounds in the sample that was tested or the metabolites that were generated through the MetaChip.
Toxicity to human cells is determined by the DataChip, said Dordick. The cells in the DataChip take up the test compounds or metabolites generated by the MetaChip, and “if the parent compounds or their metabolites are toxic, then the resulting effect will be a reduction in cell growth.”
If metabolites are not generated on the MetaChip, or if the MetaChip is metabolizing only 50 percent of the parent compounds, then the parent compounds are going directly onto the DataChip, Dordick said.
Dordick said that the incubation period of the DataChip varies according to the assay being run, but the incubation time for a growth/inhibition assay is usually three days.
“We are obviously running these tests over a long period of time on a large number of samples,” Dordick said, adding that hundreds of DataChips can be cultured simultaneously.
“The MetaChip/DataChip interaction may be at most six hours, depending on what we are looking at,” he said. “We then discard the MetaChip and culture the DataChip [and] stain it.”
If, for example, the researchers are looking at cytotoxicity, they can stain it with various dyes to determine the fraction of live and dead cells, Dordick said. The chip is then read on an array scanner or a machine that he and his team are developing, tentatively dubbed the MetaReader. Dordick explained that the MetaReader is an automated device that would be able to scan the DataChip slides and immediately capture the quantitative information.
According to Dordick, the plan is ultimately for customers to buy MetaChips and DataChips as part of the MetaReader integrated platform. “We have not developed a fully integrated platform yet, but we have developed some parts of it,” he said. For example, he said that he and his team have developed the scanning and data-analysis components.
He declined to elaborate.
Be Nice to Mice
Solidus will target its biochip technology mostly to pharmaceutical and cosmetics companies, Dordick said. He said that much of the interest in the technology is the result of a law set to go into effect in 2009 that bans animal testing on cosmetics that are produced or marketed in the European Union.
Dordick also pointed out that another piece of legislation, which affects the chemical industry — called Registration, Evaluation, Authorization, and Restriction of Chemicals, or REACH — went into effect in the European Union on June 1 of this year. The legislation requires chemical companies to test compounds produced in volumes of 1 ton or greater.  
“That’s a real problem because a lot of currently available in vitro technologies are not very predictive of what happens in a human,” Dordick said. This issue is creating quite a problem for the industry, so a need for alternative testing methods exists, said Dordick.

“The whole pharmaceutical industry clearly recognizes that it needs to deal with the ADME/Tox issue earlier rather than later.”

“There is an interest in our technology because it uses a wide range of human cell types and the metabolizing enzymes that humans have to screen for potential toxicity issues,” Dordick said. The DataChip and MetaChip technologies are also low-cost and high-throughput.
“Both the cosmetics and chemical industries cannot recoup the cost of certain alternatives to animal testing, or the cost of animal testing itself,” said Dordick. For example, animal testing in the chemical industry would be prohibitively expensive, he said.
Any US company that plans to sell a cosmetic or a chemical in Europe will have to comply with the European legislation, Dordick said. “Given that all of these companies are international anyway, they are all going to have to be compliant with the regulations.”
“Ultimately, identifying and adopting cost-effective alternatives to animal testing is an issue that is going to have to be of importance here in the US,” he said.
Dordick added that he believes countries such as Japan and Canada are likely to fall into line as well.
This is likely just the beginning of an overall, industry-wide requirement to find in vitro alternatives to animal testing protocols, which eventually will need to be validated, Dordick said. He went on to say that Solidus is currently in the process of determining the specific tests that it wants to have validated, and is primarily focusing on its tests for acute toxicity and metabolite toxicity.
A number of agencies in the US and Europe, such as the European Center for the Validation of Alternative methods, or ECVAM, and the Interagency Coordinating Committee on the Validation of Alternative Methods, or ICCVAM, “say that we have to have an in vitro test that can be used by others to obtain consistent, reproducible data in order to be validated,” he explained.
Over the next year, Solidus will be getting some of its tests that it has developed and some of its assays to the point where they are ready to be validated in various academic, governmental, and industrial labs, Dordick said. Once validated, they can be used as part of FDA and other government agency filings.  
The ADME/Tox market has gotten significantly bigger over the last two to three years, said Dordick. “The whole pharmaceutical industry clearly recognizes that it needs to deal with the ADME/Tox issue earlier rather than later,” he said.
Dordick added that he thinks the global ADME/Tox market is growing at a rate of approximately 25 percent per year, and faster in some areas.
Dordick said he believes that the value of the ADME/Tox market “as a whole is probably in the neighborhood of $5 billion to $6 billion per year, including the internal research that pharma companies do, for example, or that chemical companies or cosmetics companies do.” This internal testing represents a large fraction of the R&D done by these companies, he added.
He said he suspects that the increased focus on early-stage ADME/Tox testing “will result in a paradigm shift in the way that new drugs are developed.”
In the future, a number of these in vitro tests will become validated and become more accepted in the chemical, cosmetics, and pharmaceutical industries, said Dordick. “If that is the case, the ADME/Tox market will continue to expand and the impact that these technologies will have on specific products in the chemical and cosmetics industries, which is probably where you will see the impact first, will be dramatic,” he said.
In the past two years, Solidus has raised nearly $3 million from NIH and NSF grants and has recently begun to obtain funding through various industrial contracts with pharmaceutical, cosmetics, and chemical companies,” Dordick said. He declined to elaborate further however.
Dordick said that the company, which is located in the incubator at RPI and “plans to stay here for the time being,” currently employs six people and “needs to hire two to three more PhD-level scientists over the next few months.”

Solidus is now focusing on the cosmetics and chemical markets, as the company feels that they are the probably the first industries where its products will be used, because of the European legislation that is coming into or is already in effect, Dordick said. He added that expanding the firm’s headcount is “a priority.”