Single-Agent Mosunetuzumab Shows Durable Complete Responses in Patients With Relapsed or Refractory B-Cell Lymphomas: Phase I Dose-Escalation Study

Author(s): Lihua E. Budde, MD1; Sarit Assouline, MD2; Laurie H. Sehn, MD3; Stephen J. Schuster, MD4; Sung-Soo Yoon, MD, PhD5; Dok Hyun Yoon, MD, PhD6
Source: DOI: 10.1200/JCO.21.00931 Journal of Clinical Oncology 40, no. 5 (February 10, 2022) 481-491. Published online December 16, 2021. PMID: 34914545
Lucio Gordan MD

Dr. Lucio Gordan's Thoughts

Early study but more supportive data for bispecific antibodies in this setting. Community oncology will soon have an array of options and understanding/managing toxicities will be important for this class of drugs.


Mosunetuzumab is a bispecific antibody targeting CD20 and CD3 that redirects T cells to engage and eliminate malignant B cells and is being developed for relapsed or refractory (R/R) B-cell non-Hodgkin lymphomas (B-NHLs).


This first-in-human trial ( identifier: NCT02500407) evaluated the safety and tolerability and efficacy of mosunetuzumab in patients with R/R B-NHL and established the recommended phase II dose. Data from dose escalation are presented. Single-agent mosunetuzumab was administered intravenously in 3-week cycles, at full dose in cycle 1 day 1 (group A) or with ascending (step-up) doses during cycle 1 on days 1, 8, and 15 (group B), for eight or 17 cycles on the basis of tumor response.


Two hundred thirty patients were enrolled. Doses up to 2.8 mg and 60 mg were assessed in groups A and B, respectively; maximum tolerated dose was not exceeded. In group B (n = 197), common adverse events (≥ 20% of patients) were neutropenia (28.4%), cytokine release syndrome (27.4%), hypophosphatemia (23.4%), fatigue (22.8%), and diarrhea (21.8%). Cytokine release syndrome was mostly low-grade (grade ≥ 3: 1.0%) and mainly confined to cycle 1. Across the doses investigated (group B), best overall response rates were 34.9% and 66.2% in patients with aggressive and indolent B-NHL, respectively, and complete response rates were 19.4% and 48.5%. Among patients with a complete response, the median duration of response was 22.8 months (95% CI, 7.6 to not estimable) and 20.4 (95% CI, 16 to not estimable) in patients with aggressive and indolent B-NHL, respectively.


Mosunetuzumab, administered with step-up dosing, has a manageable safety profile and induces durable complete responses in R/R B-NHL. The expansion stage of the study is ongoing at the dose level of 1/2/60/60/30 mg selected for further study.

Author Affiliations

1City of Hope National Medical Center, Duarte, CA 2Jewish General Hospital and McGill University, Montreal, Quebec, Canada 3BC Cancer Centre for Lymphoid Cancer and The University of British Columbia, Vancouver, British Columbia, Canada 4Lymphoma Program, Abramson Cancer Center, University of Pennsylvania, Philadelphia, PA 5Seoul National University Hospital, Seoul, South Korea 6Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea

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