TNFRSF17 deletion after belantamab treatment. (A) CNV analysis of bulk WES data from patient 1 following relapse from belantamab treatment demonstrates loss of both copies of TNFRSF17. This is consistent with the emergence of a plasma cell clone with biallelic loss of TNFRSF17 (supplemental Figure 1) and explains the lack of BCMA expression seen in patient 1. (B) Integrative genomic viewer (IGV) snapshot showing the genomic deletion beginning at ∼12 Mb on chromosome 16 and covering the entire TNFRSF17 locus. CNV, copy number variant.