Comparative study of two PD-L1 expression assays in patients with non-small cell lung cancer (NSCLC).

e20581Background: Response to anti–PD-L1/PD-1 therapy in patients with NSCLC has been associated with tumor PD-L1 expression. Avelumab is a fully human anti‒PD-L1 IgG1 antibody that has shown antitumor activity in advanced NSCLC, with a trend for greater efficacy in patients with PD-L1+ vs PD-L1– NSCLC tumors, as assessed using a proprietary PD-L1 assay in development (Dako, Carpinteria, CA; based on antibody clone 73-10, Merck KGaA, Darmstadt, Germany). This study compares the analytical performance of the 73-10 assay with the FDA-approved PD-L1 IHC 22C3 pharmDx diagnostic assay (Dako) in NSCLC tumors. Methods: Formalin-fixed paraffin-embedded NSCLC tumor samples were obtained from a commercial source and from a study of first-line (1L) avelumab in patients with advanced NSCLC (NCT01772004). Tumor membrane PD-L1 expression was assessed with the 73-10 and 22C3 assays by immunohistochemistry. Correlation between assays was determined at different PD-L1 cut-off levels. Results: In initial staining of commer...