Liquid gold: blood-based biopsies make headway

Other targets and sources for liquid biopsy

Another approach to liquid biopsies that is also beginning to take off is to collect tumor-derived exosomes from the bloodstream. Exosomes are tiny, fluid-filled, membrane-bound sacks that bud off from the surface of a cell to expel waste or to transport cargo from one cell to another. DNA, RNA, and protein can be extracted from tumor-derived exosomes and could also serve as molecular biomarkers relating to the cancer cells from which they came.^6,7

Exosome Diagnostics is bringing the first exosome-based diagnostic tests to the market and recently teamed up with Amgen for the development of these liquid biopsies.¹⁷ In January 2016, they launched ExoDx Lung (ALK), for detection of EML4-ALK gene fusions in patients with NSCLC, using a proprietary platform for the isolation of RNA from exosomes. Data that was presented at several different conferences in 2015 demonstrated a sensitivity of 88% and specificity of 100% for this diagnostic when compared with tissue ALK status in NSCLC patients receiving a second-generation ALK inhibitor following progression on prior ALK inhibitor therapy.¹⁸

In September, they subsequently announced the launch of a test that analyses genetic information from exosomes collected from a urine sample taken from prostate cancer patients. Using a 3-gene signature, in combination with a proprietary algorithm, this diagnostic generates a score assessing a prostate cancer patient’s risk for higher grade, more aggressive disease. It is designed to complement the prostate-specific antigen score and has demonstrated accuracy in ruling out the presence of high-grade cancer before an initial biopsy in more than 1,500 patients.¹⁹