The purpose of this study is to determine the safety and tolerability of an experimental drug called IPH6501, as well as evaluate its activity against cancerous cells causing lymphoma. The study focuses on people who have been diagnosed with advanced relapsed and/or refractory non-Hodgkin’s lymphomas (lymphoma that has come back or is resistant to treatment), specifically diffuse large B cell lymphoma, high-grade B-cell lymphoma, primary mediastinal large B-cell lymphoma, follicular lymphoma, mantle cell lymphoma, or marginal zone lymphoma. Study procedures include vital signs collection, physical exams, blood and urine samples collection, electrocardiograms, computer tomography scans, biopsies, and administration of the study drug. IPH6501 is a molecule manufactured in a laboratory to use the patient’s own immune system (natural defenses) for acting against cancer cells through different mechanisms that might slow down and/or destroy cancer cell growth.