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Colorado State Spinout Burst Diagnostics Aims to Deliver Lab-Accurate ELISA-in-a-Cartridge


NEW YORK – Colorado State University spinout Burst Diagnostics has developed a cartridge-based antigen testing system and high-sensitivity chemiluminescence reader that it believes can deliver performance equal to PCR-based testing at half the price.

Charles Henry, CEO of Burst and chemistry professor at the university, said the company's name derives from the surface tension-based "burst" valves in its microfluidic capillary-driven immunoassay (CaDI) system. By building on technology developed in his lab at CSU, the firm has learned how to incorporate washing and amplification steps within each cartridge.

"It's an ELISA system that looks and feels a lot like a rapid antigen test with a reader added to it," he said. "We get the sensitivity and performance that's equivalent to PCR. So, we've done some head-to-head comparisons with PCR, for example, with COVID, and, if it's positive by PCR, we see it as positive by our CaDI system, including at relatively high Ct values."

The firm needs more data to show the assays consistently deliver on the accuracy seen in early testing, Henry said, but the firm plans to complete additional studies and file for US Food and Drug Administration authorization for its first test and reader by the first quarter of 2024. The first product to market will likely be the firm's multiplex test for COVID-19, influenza A and B, and RSV, and the firm is in the early stages of developing tests for sexually transmitted infections and strep throat.

Burst Chief Operating Officer Rose Nash said the company aims to deliver rapid immunoassays with lower rates of false negatives than the typical rapid antigen test used in point-of-care settings as well as deliver those results at lower costs than laboratory-based tests. The company's officers have been developing low-cost diagnostics since before the company's inception, and she and Henry said inexpensive but accurate and rapid testing could help improve healthcare to people who have lower incomes, high-deductible insurance plans, or long distances between their healthcare providers and central laboratories.

While Nash said the firm has a great working prototype for detecting respiratory diseases, "we do find this market area to be pretty crowded."

That crowding has been increasing as of late. Larger firms have been expanding their menus to incorporate syndromic panels, companies that gained prominence at the height of the pandemic have been trying to establish themselves beyond COVID-19 testing, and developers of novel testing instruments have been planning their forays into the market.

Harry Glorikian, general partner at Scientia Ventures, said that even if Burst's technology works as the company claims it does, point-of-care testing is a tough market. Any company trying to enter that market needs a product that fits within healthcare providers' existing workflows and delivers lab-level accuracy, plus they need to have a pipeline of future tests, he said.

Programming a test cartridge

Nash said the adaptable design of Burst's cartridges lets the company incorporate the steps and reagents of a full ELISA into a cartridge in a set sequence. Changing the assay target can be simple as replacing the nitrocellulose membrane used to read the results.

"We can program that through changes in channel geometry; we can incorporate washing steps, extra enzymes, or extra antibodies," Nash said. "Any step that you would find in an immunoassay, we can design that in and completely automate it through the design of this microfluidic cassette that's upstream of the nitrocellulose membrane."

The ability to deliver reagents at timed intervals has also let the company incorporate chemiluminescence and a high-sensitivity chemiluminescence sensor to read the results, Nash said, adding that future generations of the instrument will incorporate the readout into healthcare facilities' LIMS systems.

The test, Henry said, delivers answers within 15 minutes, and Burst is considering a price of $30-$35 per test. The firm is trying to make the reader affordable and doesn't yet have an estimated price, he said, "but it's certainly going to be closer to $1,000 than $10,000." Nash said the reader will likely be sold at low cost or provided free in exchange for commitments to buy test cartridges.

David Juncker, chair of the biomedical engineering department at McGill University's Genome Centre, said the performance of the typical lateral flow assay is hampered by the absence of washing steps that could reduce background noise as well as by the inability to incorporate amplification reactions. He said his research team at McGill similarly found that it is possible to encode sequential flow of solutions within the structure of an assay through capillary flow, including the addition of washing and amplification features.

Juncker said he is keen to see the performance data from Burst's quadruplex respiratory virus test, including clinical study results to support those claims.

"There are many pitfalls in assays, and so meeting those claims could still be challenging," he said.

In early studies, Burst's prototype respiratory panel for COVID-19, influenza A and B, and RSV delivered accurate results down to 2,000 copies per mL from nasal swab samples when compared to RT-PCR, Nash said. The firm also plans to compare the test's performance against LAMP-based point-of-care tests.

Burst has also been developing a prototype multiplex test for gonorrhea and chlamydia that could help increase the ease of screening, and Nash said the firm is pursuing development of a strep throat test intended for the pediatric population. Following commercialization of the CaDI platform in settings such as physicians' offices and university health clinics, Nash said the firm hopes to release new tests each year and eventually pursue at-home testing.

Glorikian said that in addition to needing to deliver laboratory quality results, companies jockeying for space in the point-of-care market need to establish how their tests will fit into the procedures and narrow time windows of a clinical visit. He also asks startups seeking investment about their pipeline of future tests, regulatory paths to authorization, reimbursement strategies, and understanding of the concerns of their potential customers and end users. He recalled a conversation with one healthcare company representative who said that if a test instrument is too small, someone could walk away with it.

"It's not necessarily the technology; it's the whole system of how you make this functional within one of these settings," he said.

Henry said Burst has talked with a few potential end users who said simplification and connections with medical records were important considerations. Nash said Burst is also incorporating into its testing design feedback from medical products distributors, and she noted that all the company's tests require no more than two steps performed by the user. The firm has also set a goal for its products to fit within existing CPT codes to ease its path to reimbursement.

Nash also said infectious disease doctor Cathy Petti, who is a former executive at Novartis and, joined Burst's board of directors this week and will help bring a customer's voice into the board room as well as experience in diagnostics markets, R&D, and capital fundraising.

"We agree that, for our tests to solve real market needs, we must go to the health care providers and solve their problems," Nash said.

The firm plans to apply for US Food and Drug Administration 510(k) clearances by the first quarter of 2024, which Henry acknowledged is an aggressive timeline for the first offering. Nash said the company is working with a regulatory specialist, though, to help the firm find the easiest regulatory pathway to marketing authorization.

Henry noted that the firm closed a seed round with two significant investors and has plans for a series A funding round within the next year to support scaled-up manufacturing, clinical testing, and commercialization. It also is considering entering the research-use market to generate revenue while performing clinical trials and developing the assays for regulatory clearance.

Burst developed its reader with Irvine, California-based Zymo Research, and the firms have formed a partnership, through which Zymo will manufacture and deliver the reader through its distribution network and Burst will make the test cartridges in-house.

Expanding testing access

Henry cofounded the company in 2020 with fellow CSU faculty members David Dandy and Brian Geiss. When the COVID-19 pandemic began, the cofounders saw an opportunity to improve antigen assays by making them simple and intuitive for clinicians and, eventually, untrained users at home.

The startup has licensed some of its immunoassay testing technology from the university and has developed upon those innovations, Henry said, and recently filed for patent protections for technologies used in its prototypes.

Henry spent the prior decade developing low-cost tools that would meet diagnostic needs in developing countries. During that time, he and Nash, then a postdoctoral fellow, worked separately on a Bill and Melinda Gates Foundation-funded project to create tuberculosis tests for use in low- and middle-income countries.

Nash said Burst has a long-term goal of working with organizations that can help bring the company's tests to these types of countries. "I think that this technology could make us an incredibly profitable company, and the people at the helm are really excited to make sure that the impacts of the company don't just stay in the US," she said.