An independent study into the efficacy of the Parsortix liquid biopsy diagnostic system has found that it is superior to the current leading antibody-based CTC (Circulating Tumor Cell) test.

The study, conducted by researchers at Western University and Lawson Health Research Institute, discovered that the Parsortix system could harvest significantly more mesenchymal prostate CTCs – which occur in greater numbers when tumours metastasise – than this leading alternative.

This is clinically relevant because, during the process of cancer metastases, cancer cells
undergo morphological and molecular changes to transition from an epithelial to a mesenchymal phenotype, and although this transition is associated with increased metastatic potential and worse prognosis, many CTC isolation methods only identify cells expressing epithelial markers.

Study author Professor Alison Allan, senior oncologist for the London Regional Cancer Program and chair of the department of anatomy and cell biology at Western University in Ontario, Canada, said: “It is estimated that 90% of cancer related deaths are due to metastatic disease because current therapies are non-curative against these aggressive cancers.

“Epithelial to mesenchymal transition (EMT) is well established as an important marker of metastasis, giving rise to cells with greater migratory capacity and invasiveness, however, many technologies used to detect CTCs rely on epithelial biomarkers.

“Here we demonstrate the unique attributes of Parsortix which position it as
an ideal CTC platform for use in the clinic, including metastatic patients with predominantly mesenchymal CTCs.”

Angle submitted an application for the Parsortix liquid biopsy using the De Novo process, an FDA pathway that involves dialogue with the regulator to assess the risk of a product that does not have an equivalent on the market.

The company had hoped its diagnostic would be approved for use in patients with metastatic breast cancer by the third quarter of 2020, but instead was granted for substantive review in September.


The study: Parsortix versus CellSearch liquid biopsy

The CellSearch, made by Italian biotech company Menarini Silicon Biosystems, is currently the only FDA-approved technology for CTC detection in patients.

The researchers in Canada conducted CTC analysis using Parsortix and CellSearch on groups of 5, 10, 100, or 1000 human breast cancer cells (epithelial phenotype) or human prostate cancer cells (mesenchymal phenotype) inserted into whole human blood.

Although they observed that overall recovery of epithelial CTCs in human blood was not significantly different between the two systems, recovery of mesenchymal CTCs in human blood was significantly higher using Parsortix.

In the discussion section of the study, the researchers said the focus of CellSearch on epithelial CTCs may be limiting the ability of oncologists to capitalise on the full potential of using them as a diagnostic marker.