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cfDNA cancer blood test that can detect mutations in 54 genes that are the targets of already-approved drugs or those in late-stage testing. Johnson & Johnson’s CellSearch system, meanwhile, was the first FDA-approved CTC-counting diagnostic. It’s approved for monitoring patients with breast, prostate, and colon cancer. There are other companies pursuing different forms of that approach as well: Houston-based ApoCell and San Diego-based Epic Sciences, among them.
McLain, however, contends these methods have limitations. Finding and isolating the rare, intact CTCs, for instance, is a tough technical challenge—“it’s kind of like [finding] a needle in a haystack,” says McLain. And cfDNA is only released when cells are dying, he adds, so it’s not going to be in the blood if a tumor is rapidly growing, limiting its effectiveness.
McLain says his company overcomes these problems by focusing on exosomes—tiny bubbles found released by all living cells that make their way into most all body fluids, including blood and urine. Exosomes were long thought to just be garbage bins; little vehicles for bundled up, excess lipids and proteins to be shipped out to fluids in the body and eliminated. When at Massachusetts General Hospital doing his post-doctoral work several years ago, Exosome’s scientific founder, Johan Skog, found that those bubbles contained something potentially more important as well—genetic information in the form of RNA. If those molecules could be isolated, Skog reasoned it might be useful as a diagnostic.
That idea was the foundation of Exosome. It has since raised over $50 million in venture funding from Qiagen, Arcus Ventures, Forbion Capital Partners, and others. Since its founding in 2008, the company has developed and patented a way to isolate exosomes from liquid samples, access the RNA, and analyze it. The entire process, from collecting a sample to returning a report to doctors, should take an average of three business days, McLain says.
McLain—who took over for founding CEO James McCullough in August—says Exosome’s approach has a few advantages over other liquid biopsy methods. First, since exosomes are consistently released from every living cell, the information the company isolates is a snapshot of the cell “as it exists today.” Second, exosomes contain both RNA and proteins, each of which should yield more information than cfDNA does, he says. Exosome can also use its process to simultaneously isolate and analyze both the RNA from exosomes and the cfDNA in plasma.
“That just gives us a sensitivity that you’re not going to be able to achieve with any other method,” McLain says.
It’s now on Exosome to go out and prove this claim, and convince payers and clinicians to buy in. That means accumulating evidence in clinical trials that its tests can change patient outcomes for the better. For instance, McLain says that many men who get a prostate-specific antigen, or PSA, test (the first line of screening for prostate cancer) have PSA counts that fall in a “grey zone.” Those men are often sent for an expensive, painful, prostate biopsy—and 75 percent of those biopsies come back negative. Exosome is conducting a large trial in which patients are getting both a biopsy and a urine test with its technology; the goal is to show that getting that urine test can obviate the need for many of those biopsies.
Exosome views prostate cancer and lung cancer as test cases for its technology—the easiest paths forward to regulatory approval and traction with doctors and payers. The goal: profitability in 2018. And given that other companies, like Irving, Texas-based Caris Life Sciences, among others, are starting to develop programs with exosome technology, McLain knows that time is of the essence—hence the push to raise more cash now.
“Being realistic, we believe we have anywhere from a three to five year lead time on somebody else figuring another way around this,” he says. “So our focus is on accelerating how quickly we can advance over [that time] and establish a position for ourselves.”
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