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MiDiagnostics Developing qPCR Platform for SARS-CoV-2 Breath Testing

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NEW YORK ─ MiDiagnostics is developing a breath test that catches aerosols carrying SARS-CoV-2 viral particles for testing by a qPCR instrument in a bid to increase the throughput of rapid testing at airports and other settings.

The company, based in Leuven, Belgium, is doing feasibility testing of a pre-commercial prototype at Brussels International Airport to gather information that will inform the final design of the test and prepare it for validation.

All going to plan, the firm will launch a breath test that consists of a silicon capture device, disposable test card, and small qPCR instrument sometime next year with the aim of cutting testing time to less than half an hour, said MiDiagnostics CEO Katleen Verleysen.

Combining breath as a sample with qPCR for detection is a new approach to diagnosing SARS-CoV-2, and the test will need extensive validation before it can be cleared by regulators and launched by MiDiagnostics.

Verleysen said the timeline for a potential launch of such as test is uncertain and more development is needed to prepare it for manufacturing, but the firm is aiming to launch it in 2022.

MiDiagnostics last month announced it had licensed technology from Imec, an R&D organization based in Belgium, that had developed a silicon sieve that captures breath aerosols.

In 2015, Imec and Johns Hopkins University spun out MiDiagnostics to commercialize diagnostic testing technology they were jointly developing that leverages a silicon, nanofluidic processor which is at the core of the current test instruments MiDiagnostics is developing.

The company licensed the silicon sieve technology because "it had reached a point where it could be turned into a product that will be affordable, scalable, and quite unique," Verleysen said.

It is pairing the capture device with a miniature qPCR instrument that it has been developing to detect SARS-CoV-2 using nasopharyngeal swabs, a sample and test combination it also plans to commercialize.

The breath test involves more sophisticated technology, but its operation is simple, Verleysen said.

The silicon sieve uses an engineering principle called impaction, involving the bending of air through the sieve, leaving behind droplets. For testing, the user blows into a tube, which enables the silicon sieve to capture aerosol droplets. The sieve is then incubated in a master reagent mix and the mix is added to a disposable test card that also performs RNA extraction and purification in preparation for PCR testing. The card is then plugged into the test instrument, and a laptop provides results on a dashboard for up to 20 instruments at a time.

The target turnaround time for tests using either nasopharyngeal swabs or breath samples is a half hour from sample to result, accounting for passenger registration, sampling, sample transportation to a container located at the airport, sample preparation, PCR testing, and reporting results to passengers.

Once the sample is loaded the instrument completes testing in less than 10 minutes, enabled by a miniature reaction chamber that resides inside the nanofluidic chip and speeds up PCR reactions, and aided by capillary forces to manage the flow of sample materials and reagents, Verleysen said.

Such a test is needed to safely open up activities such as returning to school and work during the pandemic, said Stuart Ray, who was a scientific director of the project at Johns Hopkins that contributed to MiDiagnostics' founding and currently represents Johns Hopkins on the board of the firm.

"Along with vaccinations, mask wearing, and good ventilation, rapid breath testing represents a major opportunity for us to return to normalcy," said Ray, a professor of medicine in the division of infectious diseases at Johns Hopkins University School of Medicine.

Verleysen said the nasopharyngeal swab-based SARS-CoV-2 test is further along in development, and likely to be available for commercial testing earlier than the breath test.

That is partly because nasopharyngeal swab sampling is more familiar to regulators. The firm plans to obtain both CE marking to enable marketing of the test in the European Union and other countries that accept the designation as well as US Food and Drug Administration Emergency Use Authorization.

If MiDiagnostics is successful, the swab-based test could be available next April for point-of-care testing at airports, Verleysen said, adding that the firm is currently validating its manufacturing and assembly lines with the goal of producing 2.4 million tests in the first year.

The developers are also preparing a submission to an undisclosed peer-reviewed journal to describe the studies undertaken to validate the nasopharyngeal swab qPCR test, as well as its performance, Verleysen said, adding the swab test has shown "sensitivity, specificity, and overall rates of [positive and negative percent] agreement that are in high concordance with large, centralized testing systems."

The breath test is also showing high performance in early studies, but is too early in development to establish levels of sensitivity and specificity, Verleysen added.

In practice, a large number of breath samples could be collected with minimal supervision by healthcare professionals. Based on MiDiagnostics studies, about 100 instruments are needed to provide testing for 500 passengers in an hour, she said, adding that a reagent rental business model offered by the firm would enable placing the instruments for free based on pre-agreed testing volumes.

The company plans to offer its swab-based PCR test for around €120 ($136), matching the current price for PCR testing that requires a three-hour turnaround at Brussels airport, and it is targeting similar pricing for its breath test, she said.

Additionally, based on its studies and longitudinal data it collected, breath samples from people with SARS-CoV-2 infection are positive a day earlier than for people testing with nasopharyngeal swabs. The developers are also seeing a stable decline in viral load over time, and the breath test becomes negative after eight to 10 days when a nasopharyngeal swab test from the same people remains positive for 28 days or more.

"Those results are aligned with our findings," said William Fairbrother, a professor of biology at Brown University who is leading a team developing a similar method for detecting SARS-CoV-2 in breath that relies on an enzymatic reaction mixture to detect viral RNA and convert it to DNA for measurement using a PCR instrument.

"If you are using human breath as a biological sample, you can potentially start to follow contagion risk and [determine] whether you are still infectious," said Fairbrother, who is not affiliated with MiDiagnostics. "Further, in clinical studies, we see at least a threefold enrichment of viral particles over what we are seeing with swab testing."

MiDiagnostics said it is in discussions with the FDA about the requirements for studies to prove that its breath test can show when the SARS-CoV-2 virus is no longer infectious.

Breath testing technologies

Diagnostic testing companies have been developing breath tests for years and for a range of medical conditions. For example, Owlstone Medical is involved in numerous studies to validate a breath test that captures volatile organic compounds in exhaled breath at the point of care and conducts testing by mass spectrometry in a laboratory. Owlstone has opted not to pursue a test that analyzes aerosols to detect SARS-CoV-2.

MiDiagnostics' breath testing technology to detect SARS-CoV-2 is interesting and "speeds up diagnostic testing" over what can be accomplished with nasopharyngeal swabs, said David Joseph, president and CEO of Avisa Diagnostics, which is developing a 10-minute breath test to detect metabolized urease bacteria in patients with ventilator-associated pneumonia and post-COVID-19 respiratory infections.

The Belgian firm's breath-based instrument and test may not represent a "a major breakthrough over current PCR testing, but … is good [news] for this nascent technology," said Joseph, who is not affiliated with MiDiagnostics.

As a result of its collaboration with Imec and Johns Hopkins, MiDiagnostics is also developing a complete blood count test that analyzes blood cell components to diagnose and monitor a range of health issues at the point of care. The instrument and test, which are in development and have a turnaround time of around 10 minutes, use lens-free imaging technology, a microscopy-based system that creates holograms by passing light through a sample.

The firm is aiming to commercialize the instrument and test in collaboration with an IVD-industry partner, but its primary focus is on developing its PCR technology for multiple applications, Verleysen said.

MiDiagnostics also plans to develop its breath test to detect conditions other than SARS-CoV-2 and has its eye on other respiratory diseases, including influenza and RSV, as well as tuberculosis.

However, the company also expects it may encounter hurdles in implementing the breath test. For example, the developers will need to ensure that the test is tamper proof and that people are actually blowing into the breath testing system. "We need to make sure that at the end of testing, there's a green light or some other indicator that enough of a sample volume was collected," Verleysen said, adding, "If people pretend to blow into the device, we need to know."

An additional task ahead of the firm before it can move ahead with manufacturing plans is to make the breath test more affordable and design it for manufacturing at high volumes. "At present, we are not able to manufacture millions of these, so the current feasibility study involving about 200 people will help use decide what parts of the design need changing," Verleysen said.

As MiDiagnostics continues to integrate and validate the breath capture device and qPCR instrument, it has plans to develop an instrument that enables blowing directly into a tube connected to the diagnostic instrument. That will entail additional engineering to design a portal that allows air into the instrument and then closes to allow PCR reactions, which is not an easy technical task, Verleysen said.

Ray noted that liters of sample per minute can be collected by a breath capture device, whereas PCR typically requires a one microliter sample for testing. "Something has to capture the aerosol and bring it into a reaction chamber to be tested, and that requires a capture device with a surface that is relatively large compared to a PCR chamber," he said, adding, "Those are engineering steps that are challenging, but Imec and MiDiagnostics have the people who can solve them."

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