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analyzing the tumor cells in blood in a search for biomarkers that might become drug targets or guides to treatment decisions.
Toner says the latest version of his team’s CTC testing system isolates a broader range of tumor cell types, revealing the heterogeneity of the disease’s molecular traits within individual patients. The Massachusetts General device does this with a tweak that differentiates it from the Veridex system.
The Toner team had started out with a method like Veridex’s for separating the tumor cells from other blood-borne cells. Veridex uses antibodies that selectively stick to a molecule on the surface of CTCs, such as the protein called EpCAM . Once stuck, the CTCs flow into different microfluidic channels from the other cells in the blood. But some tumor cells don’t bear the EpCAM molecule, so they may evade capture.
The third-generation CTC-iChip can work in a different mode. Instead of using antibodies to pluck out the tumor cells, it pulls away the non-tumor cells—red blood cells and white blood cells—using various means such as antibodies to those non-tumor cells, magnetic beads, and filtering by cell size. This subtractive process leaves only the tumor cells —including those without EpCAM or any other surface marker a Veridex-like system might have fished for with antibody “hooks.”
Those tumor cells may uncover a fuller range of malignant mutations in a patient’s body than a biopsy of a single tumor site. The single rare cells, once captured, can then be subjected to further tests, such as gene expression studies or assays for drug resistance.
Veridex called the CTC-iChip its “next-generation circulating tumor cell (CTC) technology” in a written statement celebrating the Toner team’s publication in Science Translational Medicine. Veridex said the device “offers enhanced specificity and sensitivity and enables more extensive characterization of captured cells,” as well as the ability to process large blood volumes “with high throughput and efficiency.”
But the timeline for commercial development of the CTC-iChip may be uncertain, or lengthy. Veridex didn’t respond to Xconomy’s inquiries about the development plan going forward, and about current revenues for its marketed system, CellSearch.
Mike Stocum, president and founder of the consulting firm Personalized Medicine Partners, says the primary market for CTC testing systems at this point is among research units at universities, government agencies such as the NIH, and drug companies. But CTC testing products may never pay off the money poured into their development until they break through into common use by practicing doctors, Stocum says.
“In order to get a return on investment, you’ve got to get routine clinical adoption,” he says. It might take revenues of $100 million or more per year, for a number of years, to pay off the development costs, Stocum says.
Stocum was hired in late 2011 as On-Q-ity’s CEO, when the startup was trying to find a partner and a path forward. During the year he held the executive post, one of his priorities was to use the On-Q-ity system to analyze patients’ tumor cells and their health outcomes, and try to demonstrate that it could help doctors make decisions. But the small company ran out of funds to do those clinical studies.
CTC testing may take off in the commercial mainstream once a study emerges showing that it can make a big difference in treatment plans for a major cancer indication, Stocum says. For example, he says, a researcher is now testing CTCs to see if they can distinguish between the prostate cancers that may not cause problems for years and the aggressive cases of the disease that should be treated immediately.
“That would take us a long way,” Stocum says.
Booth, who used his blog to share a generous analysis of the lessons he learned by investing in On-Q-ity, said CTC testing must overcome the hurdles commonly faced in all diagnostics development.
“Diagnostics aren’t for the faint of heart and are a much tougher place to make returns today than other life science subsectors,” Booth wrote. “Despite the frothy commentary about personalized medicine and the dawn of diagnostics, it’s a very tough business that faces many of the risks and costs of drug R&D but without the upside. It’s often not less capital intensive than therapeutics, faces similar ‘academic validation‘ concerns, is confronted by larger reimbursement and regulatory uncertainties, has commodity-oriented high volume, low price demands, and typically needs to get to commercialization before a material exit outcome. All these things add up for a challenging investment sector.”