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Phase I Dose-Escalation Study of Mosunetuzumab in B-Cell Lymphomas

By: Vanessa A. Carter, BS
Posted: Wednesday, March 23, 2022

Nancy L. Bartlett, MD, of Siteman Cancer Center, Washington University School of Medicine, St. Louis, and colleagues evaluated the use of single-agent mosunetuzumab—a bispecific antibody targeting CD20 and CD3—in patients with relapsed or refractory B-cell non-Hodgkin lymphomas (NHLs). These results suggest that when mosunetuzumab is administered with step-up dosing, it demonstrates manageable safety with anticancer activity. These findings were published in the Journal of Clinical Oncology.

“The clinical evidence of the step-up dosing for cytokine-release syndrome mitigation combined with the exposure-response characterization for clinical response supported the selection of a recommended phase II dose that is being further studied in histology-specific expansion cohorts,” the study authors commented. “The promising results of this phase I study raise the important question of the optimal use of bispecifics for both aggressive and indolent NHL, especially in relationship to CAR-T cell therapy.”

This first-in-human trial enrolled 230 patients with relapsed or refractory B-cell NHLs who were expected to express CD20 with no available therapy for survival improvement. Mosunetuzumab was administered intravenously in 3-week cycles, at full dose on day 1 of the cycle (group A) or with increasing doses on days 1, 8, and 15 of cycle 1 (group B), for 8 or 17 cycles dependent on tumor response.

The maximum doses for groups A and B were 2.8 mg and 60 mg, respectively. In group B, the best overall response rate for patients with aggressive disease was 34.9%, and the rate for those with indolent disease was 66.2%; complete response rates were 19.4% and 48.5%. Among individuals who experienced a complete response, the median duration of response was 22.8 months and 20.4 months for those with aggressive and indolent lymphomas, respectively.

The most common adverse events in group B were neutropenia, fatigue, diarrhea, cytokine-release syndrome, and hypophosphatemia. Of note, the authors considered the cytokine-release syndrome to be of low grade and primarily observed during cycle 1.

Disclosure: For full disclosures of the study authors, visit ascopubs.org.


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