Kantaro Biosciences LLC, a joint venture between the Mount Sinai Health System and RenalytixAI, has received emergency use authorization from the U.S. FDA for its semi-quantitative SARS-CoV-2 IgG antibody test kit. Known as COVID-Seroklir, the test determines the presence and precise level of IgG antibodies. It has demonstrated 98.8% sensitivity and 99.6% specificity for detecting SARS-CoV-2 specific IgG antibodies against two virus antigens, the full-length spike protein and its receptor-binding domain.

COVID-Seroklir is a two-step enzyme-linked immunosorbent assay and can be used by any CLIA-certified laboratory without the need for proprietary equipment.

Mount Sinai is located in New York, which was the epicenter of the first wave of the pandemic in the U.S., Sara Barrington, Kantaro's chief commercial officer, told BioWorld. Against that backdrop, Florian Krammer, professor of vaccinology at the Icahn School of Medicine at Mount Sinai, and his team developed a serological assay for the screening and identification of human SARS-CoV-2 seroconverters. Results were published in Nature Medicine May 12, 2020.

It was this Mount Sinai technology that led to this week’s development. Barrington noted that the test quantifies an individual’s antibody levels. “Having a numerical understanding of antibody levels can be especially powerful for patients, enabling them to take control of their health and enjoy some peace of mind during these uncertain times,” she added. It also can help individuals learn if they had COVID in the past and were asymptomatic. That is important because COVID-19 can have an impact on other health conditions.

For example, the U.S. CDC has noted that the virus could have cardiovascular, respiratory, renal, dermatologic, neurological and psychiatric effects.

Study data

The group also had five-month data pointing to the test’s potential that was published in Science Oct. 28, 2020, using the underlying technology. Krammer was a senior author on the paper, whose findings were based on a dataset of 30,082 individuals screened within the Mount Sinai Health System between March and October.

“I think the really important element of that study was identifying that the majority of individuals had moderate to high levels of antibodies against SARS-CoV-2,” Erik Lium, president of Mount Sinai Innovation Partners and chief commercial innovation officer of the Mount Sinai Health System, told BioWorld. He added that their response was durable, with the majority not experiencing a significant decline in the number of antibodies.

The authors did acknowledge that it is currently unclear if humans infected with SARS-CoV-2 are protected from reinfection or for how long.

However, work on common human coronaviruses has demonstrated that neutralizing antibodies are induced. These can last for years and either protect from reinfection or reduce the effects of the disease. In addition, work in nonhuman primates has shown that infection with SARS-CoV-2 does offer protection from reinfection for a period of time.

Barrington added that the implications of the study should prove interesting, particularly as it is time that experts really take control of the pandemic. “And I think that this new generation of antibody tests is really going to help us do that.”

One promising development is the possible availability of vaccines in the near term. She explained that while the vaccine will represent a big step forward, there likely will be a limited number of doses available – at least initially. The tests can help prioritize those most in need. Even front-line workers could allow others to receive a dose if they already have high levels of antibodies.

JV’s origins

In May, it was revealed that RenalytixAI Inc., of New York, had entered the joint venture with Mount Sinai. Kantaro initiated a partnership with Minneapolis-based Bio-Techne Corp. with an eye toward producing more than 10 million patient tests per month. Barrington told BioWorld that Bio-Techne could double that number produced per month if necessary.

The test just received the CE mark last month. “We’re working with distributors over in Europe. They’re thrilled in terms of being able to partner with us so that they can also take advantage of rapid deployment to multiple testing labs and locations in Europe.” She noted that the company had announced partnerships for the U.K. and Germany with Ekf Diagnostics, which will offer COVID-Seroklir, and COVID-Seroindex, for the European research market, on a non-exclusive basis. Other disclosures expected in coming months.

Beyond the U.S. and Europe, Barrington said Kantaro is talking to potential partners around the world. She noted that the company wants to help patients while also assisting in getting the global economy restarted. Currently, the test is in active review with Health Canada.