PD-L1 Expression Testing

Vamsi Velcheti, MD, and David Rimm, MD, PhD, discuss the high number of recent programmed death ligand 1 (PD-L1) inhibitor approvals and the need to harmonize the various diagnostic assay developments across the supporting clinical trials. Dr. Rimm notes the important difference between companion diagnostics, which must be used to test PD-L1 levels before prescribing a drug, and complementary diagnostics, which the FDA recommends using prior to prescribing the PD-L1 inhibitor.

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