On October 23, 2026 SystImmune, Inc. (SystImmune), a clinical-stage biotechnology company, and Bristol Myers Squibb (NYSE: BMY) reported that SystImmune’s parent company Sichuan Biokin Pharmaceutical, Ltd. (Biokin) announced positive results from a prespecified interim analysis of the randomized Phase 3 PANKU-Breast01 study (NCT06343948) evaluating izalontamab brengitecan (iza-bren), an investigational, potentially first-in-class, dual-targeting EGFRxHER3 bispecific antibody-drug conjugate (ADC), versus chemotherapy in patients with unresectable locally advanced, recurrent or metastatic hormone receptor-positive (HR+)/HER2-negative (HER2-) breast cancer who have failed at least one prior line of chemotherapy. Results will be presented today in a late-breaking oral presentation at the European Society for Medical Oncology (ESMO) (Free ESMO Whitepaper) 2026 Annual Congress taking place October 23–27 in Madrid, Spain, and simultaneously published in The Lancet.
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With a median follow-up for progression-free survival (PFS) of 15.2 months, results showed iza-bren (n=190) reduced the risk of disease progression or death, the study’s primary endpoint, by 59%, with median PFS vs. chemotherapy (n=193) of 8.2 months vs. 4.0 months as assessed by Blinded Independent Central Review (BICR) [HR: 0.41; 95% CI: 0.33-0.53, p<0.0001]. Overall survival, a key secondary endpoint of the study, was immature at the time of interim analysis. Confirmed objective response rate (cORR) by BICR was 40.5% with iza-bren vs. 20.2% with chemotherapy, and median duration of response (mDOR) was 6.9 months vs. 4.2 months, respectively.
"While there have been advances in the treatment landscape for HR-positive, HER2-negative advanced breast cancer, options can become increasingly limited as patients progress through available therapies, with most ultimately relying on chemotherapy," said Professor Binghe Xu, Academician of the Chinese Academy of Engineering, Cancer Hospital Chinese Academy of Medical Sciences. "PANKU-Breast01 provides encouraging evidence for a new therapeutic approach. Unlike other ADCs, izalontamab brengitecan is designed to target both EGFR and HER3, and the reduction in the risk of disease progression or death suggests it could offer patients a meaningful new treatment option."
The safety profile for iza-bren was manageable and no new safety signals were identified. Grade ≥3 treatment-related adverse events (TRAEs) were predominantly hematologic in nature. TRAEs were manageable with supportive care, and only 1.6% of patients discontinued iza-bren treatment due to TRAEs. Adjudicated interstitial lung disease (ILD) occurred in two (1.1%) patients with iza-bren (Grade 1 or 2).
"The 59% reduction in progression or death we see with iza-bren represents a substantial advance for patients who have limited treatment options after prior chemotherapy," said Dr. Jonathan Cheng, Chief Medical Officer of SystImmune. "This Phase 3 data, combined with our positive results in triple-negative breast cancer, demonstrates that our dual EGFRxHER3-targeting approach can meaningfully address the biology of multiple breast cancer subtypes and represents an important step towards more effective, precision-based treatment strategies."
"The positive PANKU-Breast01 results are an important validation of iza-bren’s potential as an innovative scientific approach to overcome disease resistance and the limitations of currently available treatment options," said Cristian Massacesi, MD, executive vice president, chief medical officer and head of development, Bristol Myers Squibb. "Together with the clinical benefit iza-bren has shown in other tumor types, these data position iza-bren as a potentially first-in-class dual-targeting ADC therapy with the potential to become a new standard of care across the cancer treatment paradigm."
Iza-bren has demonstrated clinical benefit in five Phase 3 trials across five distinct indications, including previously-treated HR+/HER2-negative breast cancer, previously-treated EGFR-mutated non-small cell lung cancer, nasopharyngeal carcinoma after prior treatment, previously-treated esophageal squamous cell carcinoma, and advanced triple-negative breast cancer, underscoring iza-bren’s broad therapeutic potential in areas of critical unmet need. Iza-bren has also received Breakthrough Therapy Designation from the U.S. Food and Drug Administration for previously-treated advanced EGFR-mutated NSCLC.
The PANKU-Breast01 study is sponsored by SystImmune’s parent company, Sichuan Biokin Pharmaceutical Co., Ltd. (Biokin), in Mainland China. Outside of China, iza-bren is jointly developed by SystImmune and Bristol Myers Squibb under a collaboration and exclusive license agreement.
About izalontamab brengitecan (iza-bren)
Izalontamab brengitecan (iza-bren, BL-B01D1) is a bispecific antibody-drug conjugate (ADC) that targets both EGFR and/or HER3, antigens that are highly expressed in various epithelial cancers and are known to be associated with cancer cell proliferation and survival. Upon target binding and internalization, iza-bren’s therapeutic novel Topo1i payload is released, causing cytotoxic stress that leads to cancer cell death. Iza-bren’s dual mechanism of action also blocks EGFR and HER3 signals to cancer cells, reducing proliferation and survival signals. Iza-bren is being developed under a license and collaboration agreement by and between SystImmune and Bristol Myers Squibb.
(Press release, Bristol-Myers Squibb, OCT 23, 2026, View Source;Breast-Cancer-in-Phase-3-PANKU-Breast01-Study/default.aspx [SID1234673703])