Exosome Diagnostics, Inc. has announced the launch of ExoDx Lung(ALK), the first ever CLIA-validated exosome based blood test. This test detects EML4-ALK fusion transcripts in the plasma of lung cancer patients whose primary tumors carry this mutation. Although these patients make up a small minority of cases, identifying them is important because their tumors are particularly sensitive to ALK inhibitors. Current clinical tests are performed on biopsied tumor tissue. Major drawbacks include not only the risks associated with the invasive biopsy procedure but also low test performance for some of the commonly used methods (especially immunocytochemistry-based tests). In contrast, ExoDx Lung(ALK) requires only a standard blood draw and has 88% sensitivity and 100% specificity (as reported by the manufacturer). This is a major milestone in the application of exosome-based biomarkers to precision medicine, especially in the areas of companion diagnostics and targeted therapies.
The key discovery that let to this test was made eight years ago when Dr. Johan Skog, the Chief Scientific Officer at Exosome Diagnostics, demonstrated that a mutation present in the tumors of patients with glioblastoma could be detected in their blood (Skog et al., 2008). The publication reporting this finding has been cited over 1600 times, indicating its significance and potential for broad application. Now lung cancer patients can directly benefit from the first clinical test based on this discovery, in the form of a non-invasive test to determine the EML4/ALK mutation status of their tumors. We are sure that many more biofluid-based tests, targeting not only cancers but also other conditions where non-invasive testing is desired, will soon follow.