Safety and Efficacy Study of Loncastuximab Tesirine + Ibrutinib in Diffuse Large B-Cell or Mantle Cell Lymphoma

The Phase 1 portion of the study will cover the dose escalation portion of the study. This will then be followed by the Phase 2 portion of the study, which will treat participants with the dose of loncastuximab tesirine determined in the Phase 1 portion of the study. The ibrutinib dose of 560 mg daily, will remain the same throughout both phases of the study. A standard 3+3 dose escalation design will be used for the Phase 1 portion of the study. The dose-limiting toxicity (DLT) period will be the 21 days following the first dose of ibrutinib. The dose escalation cohort will receive loncastuximab tesirine for 2 cycles with concurrent ibrutinib (concomitant therapy) and may then continue ibrutinib therapy up to one year. The Phase 2 portion of the study will involve 3 cohorts: * Non-germinal center B-cell diffuse large B-cell lymphoma (Non-GCB DLBCL) cohort * Germinal center B-cell diffuse large B-cell lymphoma (GCB DLBCL) cohort * Mantle cell lymphoma (MCL) cohort Each of the cohorts will be treated with the recommended dose of loncastuximab tesirine determined in the Phase 1 portion of the study. The study will include a Screening Period (of up to 28 days), a Treatment Period (cycles of 3 to 4 weeks), and a Follow-up Period (approximately every 12 week visits for up to 2 years after treatment discontinuation).