Relapse after glofitamab has a poor prognosis and rates of CD20 loss are high

Summary We reviewed cases with aggressive B‐cell non‐Hodgkin lymphoma who relapsed or progressed following glofitamab. The prognosis was poor, with low rates of response to subsequent salvage therapies, and a median overall survival of 4.1 months from the time of progression. There were high rates of CD20 loss (59%) at the time of relapse. In a field where CD20 × CD3 bispecific antibodies are entering routine clinical use, our experience highlights a potential means of resistance. It illustrates both the need to further characterise mechanisms of CD20 loss, and to pursue clinical trials of novel non‐CD20‐directed treatments in this cohort.