SystImmune, Inc. announced today that updated safety and efficacy data for izalontamab brengitecan (iza-bren) in locally advanced or metastatic breast cancer will be presented at the European Society for Medical Oncology (ESMO) Breast Cancer 2025 Annual Congress. The meeting will take place May 14-17 in Munich, Germany.
The presentation will feature data from an ongoing Phase 1 clinical trial evaluating iza-bren, a potentially first-in-class EGFRxHER3 bispecific antibody-drug conjugate (ADC) with a topoisomerase inhibitor payload. Iza-bren is being jointly developed by SystImmune and Bristol Myers Squibb under a collaboration and exclusive license agreement.
Promising Results in HER2-Negative Breast Cancer
Additional subgroup analysis of previously disclosed data from SABCS 2024 demonstrates encouraging efficacy for iza-bren across all HER2 expression levels in HER2-negative breast cancer patients, including those with HER2 0 status. These findings highlight continued progress in the clinical development of iza-bren and build upon previously reported clinical data.
"These data continue to support our conviction that iza-bren demonstrates strong clinical efficacy across a wide variety of tumors such as breast cancer, including HER2-negative breast cancer, with a manageable safety profile," said Jonathan Cheng, M.D., Chief Medical Officer of SystImmune. "This positions iza-bren as an important therapeutic option that may address the unmet medical needs of patients with limited treatment options."
Dr. Cheng emphasized the company's commitment to advancing the therapy through clinical trials, exploring its potential both as a monotherapy and in combination with other agents to improve outcomes for cancer patients globally.
Presentation Details
The Phase 1 study results will be presented during Mini Oral Session 2 on Friday, May 16, 2025, from 8:20 AM to 10:10 AM CEST. The presentation (No. 302MO) will be delivered by Yiqun Du from Shanghai, China, and will detail the findings from the study of iza-bren in patients with locally advanced or metastatic breast cancer.
Mechanism of Action
Iza-bren represents an innovative approach to targeting cancer cells. As a bispecific ADC, it simultaneously targets both EGFR and HER3 receptors, which are highly expressed in most epithelial tumors. The tetravalent structure of iza-bren includes two binding domains for these distinct growth factor receptors that drive cancer cell proliferation and survival.
The mechanism of action is twofold: first, iza-bren blocks EGFR and HER3 signaling to cancer cells, reducing proliferation and survival signals; second, upon antibody-mediated internalization, iza-bren is trafficked to cancer cell lysosomes where it releases its therapeutic payload, inducing genotoxic stress that activates pathways leading to cancer cell death.
About SystImmune
SystImmune is a clinical-stage biopharmaceutical company based in Redmond, Washington. The company specializes in developing innovative cancer treatments using established drug development platforms, with a focus on bi-specific and multi-specific antibodies, as well as antibody-drug conjugates.
The company has several assets in various stages of clinical trials for both solid tumor and hematologic indications. In addition to its ongoing clinical trials, SystImmune maintains a robust preclinical pipeline of potential cancer therapeutics in the discovery or IND-enabling stages, representing cutting-edge biologics development in the oncology field.
