MS4A1 (the gene that encodes CD20) transcript profiling. (A) MS4A1 RNAseq-based expression relative to CD20⁺PAX5⁺ protein IHC staining in pre-mosunetuzumab tumor biopsies, and (B) in posttreatment tumor biopsies obtained on treatment (square) vs at progression (triangle). Loss of function (LoF) variants in CD20 identified by WES (red) and WES confirmed CD20 WT (purple). (C) Changes in the levels of MS4A1 in paired tumor biopsy specimens collected on treatment (left) or at progression (right) by best overall response (CR/PR, green; SD/PD, red). (D) Summary samples with multiple CD20 biomarker measurements (IHC, RNASeq, and WES) in samples collected before mosunetuzumab (top) or at progression (ie, at progression and on treatment) (bottom). LoF, loss of function; N/A, not available; nRPM, normalized reads per million.