Frequency and outcomes of obinutuzumab‐induced thrombocytopenia

Summary Obinutuzumab is a third‐generation anti‐CD20 monoclonal antibody widely used in the treatment of B‐lymphoproliferative disorders but infrequently associated with severe thrombocytopenia, which can be life‐threatening. The pathophysiology is unclear, but platelet clearance can be extremely rapid (usually within 24 h). In a retrospective case series, we have identified four cases among 149 recipients of obinutuzumab‐containing chemotherapy regimens between 2015 and 2022 treated for haematological malignancies in Canberra, Australia (frequency 2.7%). We illustrate four cases of obinutuzumab‐induced thrombocytopenia with a review of the literature. Research is required to identify the pathophysiology and improve early recognition and management of the condition in the context of multiagent chemotherapy.