CD37 is cell surface tetraspanin present on normal and malignant B cells. Otlertuzumab (TRU-016) is a novel humanized anti-CD37 protein therapeutic that triggers direct caspase independent apoptosis of malignant B cells and induces antibody-dependent cell-mediated cytotoxicity. This study evaluated the safety, pharmacokinetics, and efficacy of otlertuzumab administered in combination with rituximab and bendamustine to patients with relapsed, indolent B-cell non-Hodgkin Lymphoma (NHL).