First Liquid Biopsy Companion Diagnostic, for Erlotinib, Approved by FDA

The FDA has approved the first ever blood-based companion diagnostic test. The cobas EGFR Mutation Test v2 was developed by Roche for the drug erlotinib (Tarceva), which was developed by Astellas for the treatment of non-small cell lung cancer (NSCLC).

Tumor cells in patients with NSCLC are released into the circulation, which can then be isolated from the patient’s blood sample for detecting specific mutations—a process called “liquid biopsy.” According to Alberto Gutierrez, PhD, director of the Office of In Vitro Diagnostics and Radiological Health in the FDA’s Center for Devices and Radiological Health, “Liquid biopsies also have the potential to allow physicians to identify patients whose tumors have specific mutations in the least invasive way possible.”

Between 10% and 20% of NSCLC patients are known to harbor the exon 19 deletion or exon 21 (L858R) substitution mutations that the test can identify. Roche evaluated this molecular diagnostic test using blood samples from NSCLC patients whose tumor biopsies were positive for EGFR exon 19 deletion or L858R mutations.

While there has been a long-standing debate about the value of liquid biopsy tests in the detection of circulating tumor cells, the cobas EGFR Mutation Test v2 could prove extremely useful in identifying the subset of potential positive responders to erlotinib, in a non-invasive manner. This addresses the fundamental issue of personalizing treatment to avoid unnecessary exposure of those patients who do not harbor the mutation, and also avoids the discomfort associated with retrieving a tumor biopsy sample. Additionally, the turnaround time with a blood-based test could help oncologists make quicker decisions on the treatment path to follow.

A much awaited liquid biopsy test is a pan-cancer diagnostic test being developed by a spin-off of Illumina. “Grail” is being developed for the early detection of cancer in asymptomatic individuals, using a technique called “ultra-deep” sequencing. The project, which had raised more than a $100 million at the beginning of the year, has the backing of a venture capital firm, Arch Venture Partners, Microsoft cofounder Bill Gates, and Amazon’s Jeffrey Bezos.