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FDA OK of Life Tech, Quidel C. Diff Assay Sets Stage for Future Cleared Tests on QuantStudio Dx

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Life Technologies and Quidel said this week that they have received 510(k) clearances from the US Food and Drug Administration to market the Quidel Molecular Direct C. difficile assay with Life Tech's QuantStudio Dx and Applied Biosystems 7500 Fast Dx real-time PCR instruments.

For Life Tech, the clearance is particularly significant because it is the first for its QuantStudio Dx system — arguably making it easier for both Life Tech and its development partners to clear future tests for marketing in the US, including infectious disease assays and cancer biomarker panels in multiple consumable formats. Life Tech and Quidel received a CE mark for the QuantStudio Dx and C. difficile assay in November.

Meantime, for Quidel, the approval is the latest in its Quidel Molecular product line, which comprises PCR reagent kits for use by molecular diagnostic laboratories on existing instrument platforms. The company also sells FDA-approved real-time PCR assays for influenza A and B, human metapneumovirus, and respiratory syncytial virus plus hMPV.

Life Tech unveiled the QuantStudio Dx last July at the American Association for Clinical Chemistry meeting (PCR Insider, 7/26/2012). It is an in vitro diagnostic version of the QuantStudio 12K Flex instrument that the company launched for research use only in October 2011 (PCR Insider, 10/13/2011).

The platforms are similar, but QuantStudio Dx does not have digital PCR capabilities, and has several distinct features that make it more amenable to developing and running real-time PCR-based in vitro diagnostic tests.

For instance, the platform features specially designed clinical laboratory software, a touch screen, reagent and sample tracking, and a laboratory information management systems interface.

QuantStudio Dx's six-color feature enables six-target multiplexing. In addition, the platform has an optional test-development mode allowing the use of easily interchangeable thermal cycling blocks that accommodate 96- or 384-well plates and a proprietary qPCR microfluidics card, which can perform 48 tests on eight samples simultaneously without the need for liquid-handling robots.

The card can also be used to design and implement custom tests. In this test development mode, the QuantStudio Dx can perform numerous functions, including pathogen detection, gene expression analysis, SNP genotyping, copy number analysis, mutation detection, microRNA and other non-coding RNA analysis, and high-resolution melt analysis.

Meantime, the ABI 7500 Fast Dx is a five-color real-time PCR platform using a 96-well format. Although the company has not disclosed exact figures, this platform has a relatively large installed base, and has already been FDA-cleared for diagnostic use with the US Center for Disease Control's H1N1 influenza assay and the Quidel Molecular assays for Influenza A+B and hMPV.

Kimberlee Caple, vice president and general manager of the molecular diagnostics business unit at Life Tech, told PCR Insider this week that it is relatively unusual for an assay to be simultaneously approved for use on two different platforms from the same company.

"I think that's primarily because most companies don't have a variety of PCR platforms as we do," Caple said. "The 7500 Fast Dx is a little bit of a lower-volume platform, geared toward a lower-throughput laboratory. And the QuantStudio Dx is geared toward a laboratory with higher volumes and the need for perhaps a little more throughput."

To Caple's point, it is not as unusual for an assay to be approved on multiple platforms from multiple companies. An example is Quidel's influenza A+B test, which is FDA-cleared on both the 7500 Fast Dx and Cepheid's SmartCycler.

Now that the QuantStudio Dx is cleared for use with Quidel's Molecular Direct C. difficile assay, it will theoretically be easier for Life Tech and its partners to gain FDA approval for other assays on the system.

"With that FDA clearance, adding menu or additional IVD tests to the menu is a simpler process through the FDA," Caple said. "The instrument itself will not need to be resubmitted."

An interesting twist on this is the fact that the QuantStudio Dx supports 96-well, 384-well, and the microfluidics card format. Regardless of what format a future molecular test might use, the instrument will still not need to be resubmitted for clearance to FDA. However, "the assay in a [microfluidic] card format and required clinical data, validation data, analytical data, et cetera, would still have to be submitted," Caple said.

Life Tech and its partners have multiple molecular tests in development for the QuantStudio Dx and, perhaps to a lesser extent, the ABI 7500 Fast Dx. For instance, Life Tech and Quidel are working on other infectious disease assays for the platforms focusing on hospital-acquired infections and respiratory ailments. Caple specifically underscored potential assays for herpes simplex viruses I and II, RSV, and flu strains.

These tests would most likely utilize the QuantStudio Dx's 96- or 384-well format, since they are usually single-analyte tests.

Meantime, Life Tech's organic molecular test development is focused mostly on the oncology space, Caple said. These assays would more likely be developed using the microfluidics card format, because they will typically comprise gene panels requiring a higher degree of multiplexing.

"There are certainly opportunities within infectious disease testing – say, paneling [gastrointestinal] pathogens or respiratory pathogens … but the bigger opportunities lay probably in oncology," Caple said. For example, she noted, the qPCR-based molecular diagnostic assay that Life Tech is developing to help select patients who may benefit from a GlaxoSmithKline candidate cancer immunotherapy will use the microfluidics card format "because it is a multi-gene gene expression test." (PCR Insider, 10/27/2011). Life Tech is also working on creating an IVD kit for its Pervenio Lung RS, a lab-developed test it launched in September to distinguish between high-risk and low-risk early-stage lung cancer patients (PCR Insider, 9/27/2012).

For Quidel, the Molecular Direct C. difficile approval is another stepping stone in its rapidly developing molecular diagnostics business. Quidel claims that its molecular product line provides attractive features for clinical laboratories including refrigerated storage instead of freezing, ready-to-use reagents, and a short time to result.

More specifically, the Quidel C. difficile assay kit includes an extraction-free, three-step sample preparation process that requires no heat step, no timed step, and no centrifugation. This direct-to-amplification procedure allows the assay to generate a result in less than 70 minutes, according to the company.

Quidel disclosed in an earnings call last year that it had signed an agreement with Life Tech to develop and commercialize real-time PCR assays for QuantStudio Dx, around the time that Life Tech introduced the instrument. This agreement built on an existing pact between the companies to market Quidel's molecular assays on the ABI 7500 Fast Dx.

Quidel executives said in October that the company is "on track" to develop a suite of some 20 real-time assays for use on existing commercial thermal cyclers – as well as eventually on its own fully integrated molecular diagnostics platform, which it hopes to launch in the developing world in 2014 and in the US in 2015 (PCR Insider, 10/25/2012).

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