Clinical Outcomes of Obinutuzumab Therapy across Non-Hodgkin Lymphoma Subtypes

Introduction: The type II anti-CD20 monoclonal antibody, obinutuzumab (OBI) is an effective therapy approved for chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) and follicular lymphoma (FL). Data are limited for use of OBI as monotherapy in CLL/SLL as well as across other lymphoma subtypes, other than the GAUSS, GADOLIN, and GAUGUIN trials. We describe our experience of OBI as monotherapy without chlorambucil in the CLL/SLL population and OBI as monotherapy or in combination regimens across non-Hodgkin lymphomas (NHLs). Patients and Methods: We conducted a retrospective cohort study of all adult pts who received OBI for CLL/SLL and NHL at the University of Pennsylvania between 2/2013 and 6/2019. Demographics, overall response, survival, and toxicities were examined. The primary endpoints were progression-free survival (PFS; defined as time from OBI start to disease progression or regimen change, death due to CLL/SLL or NHL or last-follow-up in remission), and overall survival (OS) using the Kaplan-Meier method. All other analyses were descriptive. Indolent lymphomas included follicular, marginal zone, and mantle cell lymphomas. Aggressive lymphomas included diffuse large B-cell lymphoma, Richter transformation, transformed follicular lymphoma, and transformed marginal-zone lymphoma. Results: We identified 78 pts for this analysis. Disease subtypes included CLL/SLL (58%; n=45), follicular lymphoma (13%; n=10), MZL (8%; n=6), MCL (5%; n=5), DLBCL/transformed disease (15%; n=12). Median age of OBI start was 67 years (27-89); CLL/SLL patients (pts) were median Rai Stage 2 and ECOG performance 0. NHL pts were median Ann Arbor Stage IV and ECOG performance 1. Median number of prior therapies was 1 (Range 1-7) in CLL/SLL and 3 in NHL (Range 0-9) with a median time to OBI initiation from last therapy of 12 months (mos) and 1 mos respectively. Of the CLL/SLL population 60% were rituximab naïve and 18% were rituximab refractory; 9% of NHL pts were rituximab naïve and 52% were rituximab refractory. Overall response rate (ORR) for the CLL/SLL cohort was 91%, 80% for FL, 83% for marginal zone lymphoma (n=6), 80% for mantle cell lymphoma (n=5), and 25% for aggressive lymphomas (n=12). For NHL, 50% received OBI as monotherapy, with 33% ORR. Median PFS subdivided by histologic cohorts were: 35 mos for CLL/SLL, not reached in indolent lymphomas, and 4 mos for aggressive lymphomas. Median overall survival divided by histologic subtype were 17 mos for CLL/S