Until recently, the model of what constitutes a companion diagnostic (CDx) for a drug was straightforward: It identified a biomarker that indicated an approved drug was appropriate for a specific patient’s treatment. One test; one drug. It seems almost too elegant in its simplicity. And often, it is. For patients with many forms of cancer, collecting an adequate quantity of tumor tissue for the test is often problematic, if not impossible, and in cases where a tissue sample is collected, a treating oncologist often needs to make an educated guess on the specific type of cancer for which to test with a CDx. If the doctor’s educated guess for a patient is wrong the first time, then it’s back to another test if there is enough remaining tumor tissue. That’s a big if.
Today, as next-generation sequencing (NGS) makes significant inroads for cancer diagnostics, the road map is changing. Multi-marker, pan-cancer CDxes leveraging the latest sequencing technologies are poised to significantly alter the landscape of one test for one drug, to one that allows for a single test to point toward many approved drugs. Further, as significant effort and capital is expended to find the latest immunotherapies and combination therapies for cancer, the biomarker landscape is also changing. Where once pharma companies and their diagnostic partners
searched for evidence of specific genetic variations, today their attention has turned to a new class of biomarkers and potential biomarkers such as PD-1, PD-L1, tumor mutational burden (TMB), and microsatellite instability (MSI) as researchers look to delineate responders from non-responders of these new classes of promising drugs.
“The drug companies and, obviously, the diagnostic companies are jumping on this as fast as they can. It is poised to really get traction because of the confluence of scientific and technical issues, and also the growing commercial
acceptance of next-generation sequencing as a valid cancer diagnostic test,” says David Parker, Ph.D., senior vice president, diagnostic solutions at Precision for Medicine. “It is when the commercial, the clinical, and the scientific all come together that the market really starts to move.”
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