REAL WORLD OUTCOMES OF OBINUTUZUMAB MONOTHERAPY IN PATIENTS WITH CHRONIC LYMPHOCYTIC LEUKEMIA

Introduction: Obinutuzumab (OBI) is approved for use in combination with chlorambucil for patients (pts) with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) in both frontline and relapsed/refractory (r/r) settings. OBI has been successfully evaluated as a single agent without significant loss of efficacy (Gay ND, Leuk. Lymphoma 2018). We performed an analysis of all CLL/SLL pts treated with OBI monotherapy at our institution to assess efficacy and safety in any line of therapy. Methods: We conducted a retrospective cohort study of all adult pts who received OBI monotherapy for CLL at the University of Pennsylvania between 2/2013 and 2/2019. Demographics, duration of therapy, reason for discontinuation, 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 or last-follow-up in remission), and overall survival using the Kaplan-Meier method. Results: We identified 40 pts with CLL/SLL for this analysis. Median age of start was 70 years, Rai stage 2 (35% >3), and ECOG performance status 1. Most pts were rituximab naïve (58%) and 20% were rituximab refractory. Frontline use was seen in 53% of pts received OBI frontline and 47% were treated for r/r disease. 9 pts were documented with progression and 4 patients met indication for subsequent therapy. At this time, 7 pts are receiving active OBI treatment. 55% of pts followed the package insert recommended schedule of OBI administration. Overall response rate was 90% (10% CR). The median PFS and OS for the entire cohort was 11.5 and 16.5 months respectively. At least 1 adverse events (AEs) occurred in 90% of pts. AEs included infusion related reactions (63%), thrombocytopenia (43%), infection (23%), neutropenia (15%), diarrhea (10%), neutropenic fever (8%). All pts with infusion reactions experienced symptoms on the first dose (92% grade 2; 8% grade 3), with 6 pts experiencing more than one infusion reaction in the first cycle. One patient stopped therapy after experiencing a severe grade 3 infusion reaction. One patient had an opportunistic infection (Rhizopus sp.). Keywords: chronic lymphocytic leukemia (CLL); obinutuzumab. Disclosures: Hughes, M: Consultant Advisory Role: AstraZeneca; Research Funding: Acerta Pharma. Schuster, S: Consultant Advisory Role: Novartis, Nordic Nanovector, Celgene, Merck, Gilead, Pfizer; JS: BMS, Seattle Genetics, KITE, Kyowa, Pharmacyclics; Honoraria: SJS: Genentech, Novartis, Nordic Nanovector, Celgene, Merck, OncLive, Dava Oncology, Physician's Education Source, LLC; Research Funding: SJS: Genentech, Novartis, Nordic Nanovector, Celgene, Merck, OncLive, Dava Oncology, Physician's Education Source, LLC. Svoboda, J: Consultant Advisory Role: BMS, Seattle Genetics, KITE, Kyowa, Pharmacyclics; Research Funding: BMS, Regeneron, Merck, Seattle Genetics, TG Therapeutics, Pharmacyclics. Landsburg, D: Consultant Advisory Role: Celgene, Curis; Research Funding: Triphase, Takeda, Curis. Stadtmauer, E: Consultant Advisory Role: Celgene, Janssen; Research Funding: Abbvie. Nasta, S: Consultant Advisory Role: Celgene; Research Funding: Pharmacyclics, Incyte, Roche, Aileron, Rafael/WF, Debiopharm, Takeda/Millenium; Other Remuneration: Merck: DSMC.