MOR208 is an anti-CD19 monoclonal antibody that has been effective in treating a range of lymphomas, including diffuse large B-cell lymphoma. Here, Wojciech Jurczak, MD, PhD, from Jagiellonian University, Kraków, Poland, provides an update on the ongoing COSMOS trial (NCT02639910), a study of MOR208 in combination with idelalisib or venetoclax in patients with relapsed/refractory chronic lymphocytic leukemia (CLL) who have been pretreated with a BTK inhibitor, such as ibrutinib. Speaking from the 23rd Congress of the European Hematology Association (EHA) 2018, held in Stockholm, Sweden, Prof. Jurczak describes the two arms of the COSMOS trial, and the promise of the combination of MOR208 and idelalisib, which has shown a low side effect profile while offering durable response rates.