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Exosome's $27M Series B to Drive Internal, Qiagen-Partnered MDx Development

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Having raised $27 million in a Series B financing round, Exosome Diagnostics said this week that it plans to use the funds to support the development and commercialization of a number of non-invasive fluid-based molecular diagnostic products based on its proprietary platform technology for capturing and processing nucleic acids from microvesicles.

New York-based Exosome will continue development of its own diagnostic kits, the first of which is a urine-based test designed to rule out the need for a prostate biopsy in patients with elevated prostate-specific antigen levels. The company hopes to first offer the test out of its Minnesota-based CLIA lab before seeking regulatory approval in both Europe and the US, CEO James McCullough told PCR Insider this week.

In addition, the cash infusion will help Exosome and partner Qiagen — which also participated in the financing as a new investor — continue to develop a blood-based diagnostic test to measure an actionable mutation in non-small cell lung cancer, as well as develop and launch a specialized co-branded kit to extract RNA from blood serum and plasma in the second quarter of this year.

"This is very much a platform technology," McCullough said. "We've done a considerable amount of work creating what we think is a robust fluid-based molecular platform. I really view fluid molecular as one of the next-generation pillars of personalized medicine. When we move out of the tissue into fluids, it opens up a series of new possibilities – the capacity to monitor [and] to get clinically actionable information, and continue that flow of information on a consistent, repetitive basis."

In its assays, Exosome Diagnostics is looking to isolate and analyze so-called extracellular RNA, also known as exosomic RNA or exRNA, a recently discovered class of RNA molecules that are ejected from cells and encased in spherical microvesicles such as exosomes, or are bound to circulating proteins, and travel through bodily fluids to deliver messages to other cells in the body.

Specifically, the company has developed a proprietary method for isolating and preparing specific RNA molecules from these microvesicles, and particularly a class of microvesicles called exosomes.

McCullough noted that the company does not believe that the information contained within exosomes is a magic bullet in terms of detecting or monitoring diseases such as cancer; rather, it complements information that can be collected through a number of molecular assays. "These are very complex diseases we're working with," he said. "There is different biological significance at different time points that is a function of treatment, stress, tumor growth, recurrence. That said, the exosome provides unique information … that other fluid molecular technology approaches cannot."

For instance, he said that preparing and analyzing exRNAs from exosomes enables the company to both detect specific mutational biomarkers and profile gene expression levels. "I think the [next generation] of fluid molecular solutions are going to have both mutation detection and level-based analysis," he noted.

Another key aspect of exosomes is that they provide a natural, stable package for exRNAs, which has "a number of significant influences on the clinical diagnostic programs we are pursuing," McCullough said.

"For example, with prostate, the stability of the RNA expression signature that we're using comes simply in urine," he said. "It's a truly non-invasive sample collection format. If you can pee in a cup, we can get a molecular analysis against your prostate."

In addition, when applied to biomarker discovery for drug response or disease recurrence, the stability of the nucleic acid component of the exosome can withstand freezing, "so we can take a look at these incredible, very well-characterized biobanks that are available [within] pharmaceutical companies [and] academic centers … and we can go back and get a stable nucleic acid preparation out of a [small] blood sample. That becomes a critical enabler, because now we can do relatively quick biomarker discovery against a selective outcome point, out of a frozen sample."

Stable microvesicles containing these exRNAs are present not only in urine, but also bodily fluids such as blood and cerebrospinal fluid, a fact that Exosome Diagnostics plans to also leverage as part of its product-development efforts.

The company's most advanced internal development effort is EXO106, a diagnostic test using a non-invasive urine sample that could potentially reduce the number of unnecessary prostate biopsies in patients with elevated PSA levels.

"We have a multi-center study group [with] more than 12 [academic] centers contributing," McCullough said. "We do have a signature, and we are constructing an assay that has a negative predictive value bias. If you have an elevated PSA level, this brings additional information with a negative predictive value … prior to going to a biopsy."

McCullough said that the company plans to initially launch this assay this year through its CLIA lab in St. Paul, Minn., but it will also seek regulatory approval in Europe and the US, though he didn't provide a timeline for the latter goals.

Exosome Diagnostics is also working on a blood-based, multi-gene biomarker panel called EXO1000 for use in oncology applications. "We're starting in key cancer areas like lung cancer and building outwards," McCullough said. "A lot of mutations and expressions are applicable across multiple cancers, and we intend to continue to build a panel of both key expressions and key mutations in concert."

At least the urine-based prostate cancer assay will use reverse-transcription quantitative PCR for analysis. McCullough said the company has evaluated a number of different RT-qPCR platforms, but is not yet ready to announce which company's platform it will use.

One possibility is Qiagen's Rotor-Gene Q thermal cycler which, both alone and in combination with the QIASymphony RGQ automation platform. The former has been cleared for use by the US Food and Drug Administration, and the latter Qiagen recently submitted to the agency for clearance.

Qiagen makes sense as a platform provider for Exosome since the two companies have already struck a broad product development and co-marketing agreement for a number of different biofluid molecular assays.

Exosome's recent financing will also support these initiatives with Qiagen, the first of which is EXO501, a blood-based diagnostic test measuring an actionable mutation in non-small cell lung cancer to repeatedly and non-invasively assess tumor mutation status.

"The intention there is to follow a regulatory pathway, so we have to create a very robust, very well-controlled diagnostic that is capable of withstanding the regulatory process," McCullough said. "The kits have to eventually be put on top of a broadly distributed, well-recognized instrument platform, and in this case Qiagen was the perfect partner to do that."

In addition, Exosome and Qiagen are planning to globally launch in the second quarter of this year a co-branded research kit called exoRNeasy to extract RNA from blood serum or plasma.

"Qiagen is the world leader in sample prep, so was a very natural partner for us," McCullough said, citing the company's "manufacturing, distribution, instrumentation, and regulatory know-how" as key assets. "We're doing a lot of work with [Qiagen] and again, we're very much interested in pursuing robust regulatory diagnostics."

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