Quanterix Corp., of Billerica, Mass., reported that researchers have developed a COVID-19 antibody test with 1,000 times the sensitivity of current tests using its Simoa bead-based immunoassay platform. The blood-based test detects and measures immunoglobulin G (IgG), IgM and IgA antibodies against four immunogenic viral proteins, or antigens, associated with SARS-CoV-2, the virus responsible for the current pandemic, showing seroconversion as early as one day after the onset of symptoms with less than a microliter of plasma.

In a study led by David Walt, a scientific founder and board member of Quanterix and professor at Harvard Medical School and Brigham and Women’s Hospital, the high-fidelity panel demonstrated 86% sensitivity and 100% specificity during the first week of infection when COVID-19-positive patients were compared with prepandemic controls. Both sensitivity and specificity were 100% when patients were tested one week after onset of symptoms.

Quanterix licensed the assay from Brigham and Women’s. Medrxiv released a preprint of the study late Monday. It is currently undergoing peer review.

First step is quantitative IgG test

Kevin Hrusovsky, Quanterix’s chairman, president and CEO, said the company’s goal is to get the multiplex serological assay into the population studies research use only (RUO) market as quickly as possible and then launch a quantitative single plex IgG test for RUO use in the second quarter of 2020. The aim of the population study would be twofold: to gauge the incidence of COVID-19 and begin to understand what the results explain about how the disease affects different individuals.

Based on those results, the company hopes to transition the test to a commercially available product for more widespread COVID-19 testing. “I think it’s absolutely possible that we would seek an emergency use authorization [from the U.S. FDA] in 2020,” he told BioWorld.

Hrusovsky likened the RUO test to a 12-plex serology test. “Nothing in the world would provide anything like that, so that’s a really deep dive. But it’s going to be a more expensive test because of its breadth,” he said. “We think the quantitative IgG test would be the first step in a population study because it’s a lower-cost, high intel” product.

Plan includes at-home fingerprick test

Patients who tested positive with the IgG test would be followed up with the multiplex assay to gain more insights on that person and the level of antibodies they have across different categories and whether those antibodies are neutralizing against reinfection with SARS-CoV-2.

Currently, the test is based on a blood draw. However, Hrusovsky said the longer-term aim is to offer a fingerprick test so that patients could collect their own blood sample and then ship it to a central lab for testing.

“We think the capillary’s going to be a pretty important way for us to help the world get these answers from home,” he said, adding to assay’s sensitivity – 1,000 times that of other technologies – is “what allows you to get an answer from a fingerprick.”

The company is developing its quantitative IgG test for use with its Simoa HD-X analyzer, which launched in October 2019. About 60 units had been deployed by the end of last year, at least 10 of those in CLIA laboratories, and Hrusovsky said he believed a large number of the devices were on sites that have CLIA labs.

Increasing protein detection

Separately, Quanterix reported results from a study showing a 100-magnitude increased sensitivity of digital enzyme-linked immunosorbent assays (ELISAs) using a modified version of the Simoa technology that powers its HD-X and SR-X ultra-sensitive biomarker detection systems. The results, published in Lab on a Chip, boost the signal-to-background of ELISAs, enabling detectability from a wider range of proteins.

The paper also describes a novel approach called magnetic-meniscus sweeping (MMS) that increased by 10-fold the number of beads loaded into microwell arrays in the Simoa disk. The researchers used this, along with improved optics and image analysis algorithms, to create an assay for IL-17A, a pro-inflammatory cytokine, that is 437 times more sensitive than standard digital ELISA.

“Our technology today is a thousand times more sensitive,” Hrusovsky said. “our goal … is that by the end of 2021 we’re going to have an instrument that would be 100 times more sensitive than the current instrument. That would make it 100,000 times more sensitive than most of today’s technologies.”

Strong Q1

For the first quarter of 2020, Quanterix’s revenue increased 28% year over year to $15.7 million, beating both consensus estimates. During an earnings call, Hrusovsky said that in addition to quantitative COVID-19 serology testing, the company is exploring capabilities for viral antigen testing with its Simoa platform.

In a recent note, BTIG’s Sung Ji Nam said "the company’s quick mobilization to offer its uniquely positioned technology platform and products for COVID-19 research, vaccine/therapeutic development and diagnostics applications is expected to contribute an incremental $3 million to $5 million in revenue this year."

Cowen analyst Doug Schenkel echoed the positive outlook. “[T]here is building evidence that Quanterix’s technology has utility in diagnostics (particularly in neurology applications, though not limited to), and COVID-19 provides another avenue for QTRX to demonstrate the applicability of its Simoa technology in diagnostics,” he wrote.

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