The in vitro cytotoxic activity of naratuximab emtansine correlated with CD37 expression. (A-F) Pearson correlations between naratuximab emtansine activity, measured by IC₅₀ values, and CD37 protein surface expression, measured by FACS in both B- and T-cell lymphomas (A; n = 54); CD37 RNA levels, measured by the 2 different probes on the Illumina HT-12 arrays, in both B- and T-cell lymphomas (B-C; n = 51); or B-cell lymphoma only, measured with the Illumina HT-12 array (D-E; n = 43) or via total RNA-Seq in 45 B-cell lymphomas (F; n = 45). Illumina HT-12 arrays and RNA-seq data were available for 51 and 45 of the 54 cell lines, respectively.