Early-phase clinical trials investigating several MALT1 protease inhibitors in relapsed or refractory B cell non-Hodgkin lymphoma (including DLBCL) and chronic lymphocytic leukemia are under way (ClinicalTrials.gov NCT05618028, NCT03900598, NCT04876092, NCT04657224, NCT05515406, and NCT05544019). Here, MALT1 is linked to B-cell chronic lymphocytic leukemia.