Phase 3 Success Boosts Prospects for Iza-Bren

SystImmune and Bristol Myers Squibb have reported positive Phase 3 results for izalontamab brengitecan (iza-bren), an investigational bispecific antibody-drug conjugate (ADC), demonstrating significant survival benefits in patients with difficult-to-treat triple-negative breast cancer (TNBC) and esophageal squamous cell carcinoma (ESCC). The findings, presented at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting, further strengthen the therapy’s position as a potential new standard of care across multiple cancer types.

The results were disclosed by Sichuan Biokin Pharmaceutical Co., Ltd., the parent company of SystImmune, following prespecified interim analyses of two pivotal Phase 3 studies. Both trials met their primary objectives, showing statistically significant and clinically meaningful improvements in overall survival (OS) and progression-free survival (PFS) among heavily pretreated patients with advanced disease.

One of the studies, PANKU-Breast02 (BL-B01D1-307), evaluated the treatment in patients with unresectable locally advanced or metastatic triple-negative breast cancer, an aggressive form of breast cancer that lacks common therapeutic targets and is often associated with poor outcomes. The second study, PANKU-Esophagus01 (BL-B01D1-305), assessed the therapy in patients with recurrent or metastatic esophageal squamous cell carcinoma, another cancer type with limited treatment options after disease progression.

According to the companies, iza-bren is a potentially first-in-class EGFRxHER3 bispecific antibody-drug conjugate. The therapy is designed to target two cancer-related proteins simultaneously while delivering a potent anti-cancer payload directly to tumor cells. This dual-targeting approach is intended to improve efficacy while minimizing damage to healthy tissues.

The newly reported data mark a significant milestone in the development of bispecific ADCs. The TNBC trial became the first Phase 3 study of a bispecific ADC to demonstrate positive results for both progression-free survival and overall survival as dual primary endpoints in triple-negative breast cancer. Similarly, the ESCC study represents the first Phase 3 trial of a bispecific ADC in esophageal cancer to achieve positive outcomes on both key efficacy measures.

These achievements build on earlier success for iza-bren. In 2025, the therapy delivered positive Phase 3 results in recurrent or metastatic nasopharyngeal carcinoma (NPC), further highlighting its broad potential across multiple tumor types. With positive findings now reported in three separate Phase 3 trials, the investigational treatment is emerging as one of the most promising candidates in the rapidly growing antibody-drug conjugate field.

Dr. Yi Zhu, Chief Executive Officer of Biokin, said the results reinforce the value of iza-bren’s dual mechanism of action and demonstrate its ability to provide meaningful clinical benefits compared with existing treatment standards. He noted that the therapy’s success across multiple cancers underscores its broad therapeutic potential and supports ongoing efforts to expand its use in additional indications.

Bristol Myers Squibb, which is collaborating on the development of the therapy, also emphasized the significance of the findings. Cristian Massacesi, Executive Vice President, Chief Medical Officer and Head of Development at the company, stated that iza-bren could help address a major treatment gap for patients whose disease progresses after prior therapies. He added that the drug may also have potential applications in earlier lines of treatment and in combination with other cancer therapies.

The growing body of evidence supporting iza-bren comes at a time when researchers are increasingly exploring bispecific ADCs as a new frontier in oncology. By combining targeted antibody technology with highly potent cancer-killing agents, these therapies aim to improve precision and effectiveness compared with conventional chemotherapy.

With positive Phase 3 results now spanning triple-negative breast cancer, esophageal squamous cell carcinoma, and nasopharyngeal carcinoma, iza-bren is positioning itself as a potential cornerstone therapy in oncology. Regulatory submissions and further development activities are expected to follow as the companies seek to bring the treatment to patients facing some of the most challenging forms of cancer.