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With Expanded FDA Clearance for Sepsis Test, Immunexpress Furthers Commercialization Strategy


NEW YORK – After getting expanded clearance from the US Food and Drug Administration for its sepsis test, Immunexpress is continuing its commercialization path and working on further expansions for its assay. 

The qPCR-based SeptiCyte Rapid test first received FDA clearance in 2021 and has been CE-marked and available in Europe since 2020. Last month, the company received 510(k) clearance for use of the test with ethylenediaminetetraacetic acid (EDTA) blood-compatible cartridges, which had been available in Europe since August 2022. According to Immunexpress CEO Rollie Carlson, the European approval "jumpstarted uptake in Europe," particularly in Germany, France, and Spain. 

It previously had clearance for use of the test with venous blood samples collected in PAXgene Blood RNA tubes. 

SeptiCyte Rapid also this week received regulatory clearance from the Australian Therapeutic Goods Administration, and the test will be sold in Australia through Abacus Diagnostics. 

The device remains the same, and the customer will be able to choose what blood tube is used for the test, with only a slight modification in the software depending on which tube is used. In some cases, customers will want to use PAXgene tubes to look back on stored samples, Carlson said, but noted that there were "some significant potential customers in the US" waiting on the EDTA approval. 

The SeptiCyte Rapid assay runs on Biocartis' handheld Idylla platform and is used to assess patients with suspected sepsis by quantifying mRNA transcripts of host response genes phospholipase A2 group VII platelet activating factor (PLA2G7) and placental-specific 8 (PLAC8) and determining their relative expression levels. The genes are expressed in white blood cells when patients experience the cytokine cascade that indicates sepsis, and the expression differs depending on whether a patient is having an inflammatory response caused by a pathogen that will lead to sepsis or a general systemic inflammatory response. 

The rule-in, rule-out test returns a SeptiScore of between 1 and 15 that correlates to the probability of sepsis within one hour. A score above 7 means physicians can prioritize the blood culture to determine the pathogen and treatment options, while a lower score allows clinicians to look for another cause of symptoms.

The test is approved for use in adults, but Carlson noted that the company completed trials for pediatric use and will be submitting it for expanded regulatory approval this month in that population, which will further broaden its potential customer base. The test's pricing is comparable to direct pathogen detection tests in blood and blood cultures, he added.

The firm is also working on a test, SeptiCyte BV, developed on the same cartridge that will be able to tell whether an infection is bacterial or viral. The new assay has been evaluated in more than 4,000 pediatric and adult patients, and the company has had discussions with the FDA about a regulatory trial for the test, Carlson said. 

In 2020, the firm published a paper in BMC Medicine describing the identification and validation of a transcriptomic blood signature to detect the host response to bacterial infection. A signature to detect host response to viral infection was validated in a Scientific Reports paper published in 2017. The combination of the two signatures was validated in the BMC paper on whole blood from emergency room patients with fevers, and the combination discriminated between bacterial and viral infections in those patients with an area under the receiver operating characteristic curve of 0.95.

According to Carlson, the two signatures are the basis of SeptiCyte BV, but "the final test has a couple of additions and deletions" and includes 10 genes.

The BV test's development was particularly complex because "there's not only the biological sort of signal that you're looking for to make that distinction between bacterial and viral, but then you have the technical complication, which is do these genes behave well together, because you're in a multiplex environment," he said. 

Beyond its technological and portfolio developments, the firm is also seeking a Series C fundraising round and would "very much entertain" strategic partnerships, particularly with companies that have relationships with hospitals and a broader reach, he said. In the US, it uses a direct sales method but is looking to partner with organizations that are focused on critical care settings and has been in discussions with some potential, unnamed strategic partners. 

While the company is currently focused on the hospital market, Carlson said that it has also seen interest from large players in the elder care and long-term care space that would like to have the capability of testing for sepsis on-site. The technology could be used at the point of care, but Carlson noted the firm would need to pursue CLIA waiver, which is an opportunity it plans to pursue in the future.

Rapid sepsis testing has long been an area of interest in the diagnostics industry, with many firms, established and startups, competing for a spot in the market. In Carlson's view, what sets Immunexpress apart is that its signal has been developed "to distinguish between the systemic inflammatory response and sepsis" early in the process. Other companies, such as Inflammatix and Cytovale, are also developing or launching rapid sepsis host response tests. Stanford University spinout Inflammatix is preparing to launch a blood-based test to help differentiate between bacterial and viral infections and noninfectious diseases, as well as predict disease progression in adults who have suspected acute infections or sepsis. Cytovale, meantime, has an FDA-cleared prognostic blood test that stratifies patients by sepsis risk using high-speed imaging and machine learning to measure immune cell activity associated with the sepsis host response.