Background: Ibrutinib, a first-in-class oral Bruton’s tyrosine kinase inhibitor, has demonstrated single-agent activity in a variety of relapsed or refractory B-cell malignancies with limited toxicity, making it an appropriate drug to combine with standard R-CHOP chemotherapy in patients with previously untreated NHL. Methods: Patients received oral daily dose of ibrutinib (280, 420, or 560 mg) in combination with standard doses of R-CHOP (rituximab, cyclophosphamide, doxorubicin, and vincristine on day 1, and prednisone on days 1 through 5 of each 21-day cycle for up to 6 cycles). The primary objective was to determine the recommended phase 2 dose (RP2D) of ibrutinib in combination with standard R-CHOP (IR-CHOP). The secondary objectives were to assess safety, overall response rate, pharmacokinetics, and pharmacodynamic biomarkers. Results: Seventeen patients (7, 4, and 6 in increasing ibrutinib doses) were enrolled: 59% male, median age 65 (range 46-81) years, diffuse large B-cell lymphoma 47%, mantle cell lymphoma 29% and follicular lymphoma 24%. In the 280 mg cohort, 2 patients had dose-limiting toxicity (DLT): 1 with transient syncope and 1 with periorbital cellulitis; at 560 mg, 1 patient had gastritis (grade 2). The RP2D was established at 560 mg ibrutinib. The most common (≥ 20% of patients) adverse events (AEs) were neutropenia (77%), thrombocytopenia (65%), vomiting (59%), anemia (53%), nausea (47%), fatigue (35%), headache (29%), constipation (24%), diarrhea (24%), and dizziness (24%). To date, 6 patients completed 6 cycles of treatment, and 2 patients discontinued treatment (1 due to noncompliance with the study drug and 1 due to non-DLT AE). At the time of this analysis, of the 10 patients had at least one post baseline tumor, the overall response rate was 100% (7 complete and 3 partial responses). Conclusions: The combination of IR-CHOP has an acceptable safety profile. No new toxicities were noted with adding ibrutinib to R-CHOP. An expansion cohort 560 mg ibrutinib (RP2D) is being opened to further explore the safety and efficacy of IR-CHOP in patients with newly diagnosed diffuse large B-cell lymphomas. Clinical trial information: NCT01569750.