Loncastuximab Tesirine and Venetoclax for Relapsed/ Refractory Non-Hodgkin Lymphoma

This is a phase I trial designed to evaluate the safety and tolerability of loncastuximab tesirine given in combination with venetoclax for treatment of relapsed/refractory non - Hodgkin lymphoma. Loncastuximab tesirine is an investigational (experimental) drug that works by targeting a protein in cancer cells (called CD19) and delivering a small amount of chemotherapy directly to the cancer cells. Loncastuximab tesirine is experimental because it is not approved by the Food and Drug Administration (FDA). Venetoclax, is a targeted anti-cancer drug, which works by imitating a particular protein produced by the tumor and interrupting its normal processes, ultimately causing the tumor cells to die. Adding venetoclax to the loncastuximab tesirine regimen is believed to increase the chance of getting relapsed or refractory B cell lymphoma cancer in remission. Venetoclax is approved by the FDA for treatment in some types of cancer, but is not approved by the FDA for the treatment of lymphoma soit is considered experimental in this study. Up to 36 subjects will take in this phase I research study. The primary objective for this study: To determine the safety and tolerability of the combination of loncastuximab tesirine and venetoclax to identify the recommended phase 2 dose (RP2D) of these agents. Secondary objectives are: * To describe the adverse event profile of the combination of loncastuximab tesirine and venetoclax. * To describe the overall response rate (ORR) and complete response rate (CRR) of relapsed/refractory non-Hodgkin lymphoma treated with the combination of loncastuximab tesirine and venetoclax. * To describe the overall survival (OS) and progression free survival (PFS) of subjects with relapsed / refractory non-Hodgkin lymphoma treated with the combination of loncastuximab tesirine and venetoclax. * To describe the disease-free survival, the disease specific survival and time to treatment failure of subjects with relapsed/refractory non-Hodgkin lymphoma treated with the combination of loncastuximab tesirine and venetoclax.