Positive Results for Mosunetuzumab in Japanese Phase I Study: Meeting Primary Endpoint for Relapsed and Refractory Follicular Lymphoma Expansion Cohort

Chugai Pharmaceutical Co., Ltd. (TOKYO: 4519) has revealed that the anti-CD20/CD3 bispecific antibody mosunetuzumab has successfully met the primary endpoint of achieving a complete response rate (CRR) in an expansion cohort within the Japanese Phase I study. This study aimed to assess the efficacy and safety of mosunetuzumab in patients with relapsed or refractory (R/R) follicular lymphoma (FL) who had undergone two or more prior systemic therapies. The safety profile observed in the study remained consistent with findings from previous overseas trials.

Dr. Osamu Okuda, President, and CEO of Chugai expressed optimism regarding these results, stating, “R/R FL poses significant challenges in terms of recurrence and treatment, necessitating novel therapeutic approaches. We are greatly encouraged by mosunetuzumab’s achievement of CRR and its promising outcomes for achieving remission. Our commitment remains steadfast in seeking approval for mosunetuzumab in Japan, aiming to swiftly offer this treatment option to patients.”

Chugai intends to pursue a new drug application in Japan based on the positive outcomes from this study, along with data from Phase I/II clinical trials conducted overseas by Roche, targeting the same patient demographic.

The Japanese Phase I study for mosunetuzumab comprised both dose-escalation and expansion cohorts, specifically focusing on patients with R/R FL who had previously undergone two or more systemic therapies. Notably, the expansion cohort included 19 patients, with the primary endpoint set as CRR. Key secondary endpoints encompassed overall response rate, progression-free survival, and duration of response.

Mosunetuzumab, a CD20xCD3 T cell-engaging bispecific antibody, has been developed to target CD20 on B cells and CD3 on T cells. The mechanism of action is expected to involve the activation of the immune system through cytotoxic T cells, thereby exerting antitumor effects on CD20-expressing tumor cells. The drug is currently under development with both intravenous and subcutaneous formulations, aiming to address R/R FL and R/R aggressive B-cell non-Hodgkin lymphoma.

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