RNA-seq analysis of paired Non-Hodgkin's lymphoma (NHL) tumor samples at pretreatment and after mosunetuzumab relapse coinciding with the loss of CD20 protein

CD20 protein-negative diseases were observed for a subset of patients with B-NHL that relapsed after initial responses to mosunetuzumab. For many of these tumors, whole exome (WES) and RNA-seq failed to detect any MS4A1 genetic variants or loss of CD20 mRNA, which could have explained the apparent loss of CD20 protein. For this study, we obtained formalin-fixed paraffin-embedded (FFPE) tumor samples from a similar cohort of four additional patients relapsing after mosunetuzumab, and performed RNA-seq to look for changes in the splicing pattern of CD20. We performed RNA-seq analysis on FFPE tumor samples from 4 patients with B-NHL that have relapsed to mosunetuzumab. All four patients had paired pretreatment (“pre”) tumor samples that were CD20 positive by IHC and mosunetuzumab relapse (“post”) samples that had lost CD20 protein expression.