There is a need for additional treatment options for patients with relapsed or refractory diffuse large B‐cell lymphoma (DLBCL) who do not benefit from available therapies. We examined combinations of the cereblon E3 ligase modulator (CELMoD) agent avadomide (CC‐122), the selective, ATP‐competitive mammalian target of rapamycin kinase inhibitor CC‐223, and the potent, selective, covalent Bruton tyrosine kinase inhibitor CC‐292 in patients with relapsed/refractory (R/R) DLBCL.In the multicenter, phase Ib CC‐122‐DLBCL‐001 study (NCT02031419), the dose‐escalation portion explored combinations of CC‐122, CC‐223, and CC‐292 administered as doublets or triplets with rituximab in patients with chemorefractory DLBCL. Primary endpoints were safety, tolerability, and dose‐limiting toxicities; additional endpoints included pharmacokinetics, pharmacodynamics, biomarkers, and preliminary efficacy.As of December 1, 2017, 106 patients were enrolled across four cohorts. The median age was 65 years (range 24–84 years), and patients had a median of 3 (range 1–10) prior to regimens. A total of 101 patients (95.3%) discontinued, most commonly due to disease progression (49.1%). The most common any‐grade adverse events (AEs) across treatment arms were gastrointestinal and hematologic; the most common grade 3/4 AEs were hematologic. CC‐122 was well tolerated, with no unexpected safety concerns. Preliminary efficacy was observed in three of four treatment arms. CC‐122 plus rituximab was considered suitable for dose expansion, whereas CC‐223 and CC‐292 combinations were associated with enhanced toxicity and/or insufficient improvement in responses.CC‐122 plus rituximab was well tolerated, with preliminary antitumor activity in patients with R/R DLBCL. This innovative study demonstrates the feasibility of assessing the tolerability and preliminary efficacy of novel combinations utilizing a multi‐arm dose‐finding design.