Bristol Myers Squibb (BMS) has reported positive results from two phase 3 trials of izalontamab brengitecan (iza-bren), a bispecific antibody-drug conjugate (ADC), in patients with lung and breast cancer. Conducted in China by the drug’s original developer, Sichuan Biokin Pharmaceutical, the Panku-Lung01 and Panku-Breast01 studies demonstrated improvements in progression-free survival (PFS).
Detailed findings from both studies were presented at the European Society for Medical Oncology 2026 Congress in Madrid. Their results bring the number of positive phase 3 studies of iza-bren in China to five.
“This brings five out of five positive phase 3 studies with this ADC. That is quite remarkable,” said Cristian Massacesi, M.D., BMS’s chief medical officer, in an interview with Fierce.
Results in EGFR-Mutant Lung Cancer
Panku-Lung01 evaluated iza-bren in patients with EGFR-mutant non-small cell lung cancer (NSCLC) whose disease had progressed following treatment with a third-generation EGFR tyrosine kinase inhibitor (TKI).
The study found that iza-bren reduced the risk of disease progression or death by 60% compared with platinum-based chemotherapy. Median PFS was 11.1 months among patients receiving iza-bren, compared with 5.7 months in the chemotherapy group.
The confirmed objective response rate (ORR) was 60.2% with iza-bren and 34.5% with chemotherapy. Median duration of response was 10.5 months and 5.7 months, respectively.
Overall survival (OS) data were immature, although the findings indicated a favorable trend toward a 34% improvement.
BMS has launched the phase 2/3 Izabright-Lung01 trial to evaluate iza-bren in patients with EGFR-mutant NSCLC following progression on TKI treatment. Results are expected in 2028. The company also began the global phase 3 Izabright-Lung02 trial last month to investigate the drug in the first-line setting.
Massacesi described the Panku-Lung01 findings as relevant to setting expectations for the global studies, noting that EGFR mutations are more common among Asian patients than Western patients.
Breast Cancer Trial Shows Improved PFS
Panku-Breast01 investigated iza-bren in patients with hormone receptor-positive, HER2-negative (HR+/HER2-) breast cancer who had previously received endocrine therapy, CDK4/6 inhibitors and chemotherapy.
The study demonstrated a 59% improvement in PFS compared with physician’s choice of chemotherapy. Median PFS was 8.2 months in the iza-bren group, compared with four months in the chemotherapy group. Confirmed ORR was 40.5% and 20.2%, respectively.
A subgroup analysis found PFS improvements across HER2 expression levels, including 59% among patients with IHC 0, 47% among those with IHC 1+ and 68% among those with IHC 2+/ISH-.
OS results were not presented because the data were still very immature, Massacesi said.
Global Breast Cancer Trial Still Under Assessment
BMS has not yet initiated a global phase 3 trial corresponding to Panku-Breast01. Massacesi said the company was assessing the opportunity, noting that the HR+/HER2- breast cancer treatment landscape includes multiple treatment options and new entrants.
Other treatments in this setting include AstraZeneca and Daiichi Sankyo’s TROP2 ADC Datroway. In the global phase 3 Tropion-Breast01 trial, Datroway demonstrated a 37% PFS benefit over chemotherapy in patients with HR+/HER2- breast cancer who had previously received endocrine therapy and chemotherapy. Median PFS was 6.9 months with Datroway and 4.9 months with chemotherapy, while ORR was 36.4% and 22.9%, respectively.
Oral selective estrogen receptor degraders (SERDs) have also emerged as a treatment class for certain patients with HR+/HER2- breast cancer. Celcuity’s PI3K/mTOR inhibitor Revtorpyk has received FDA approval, while Enhertu has become an option for certain patients previously classified as HER2-negative through the HER2-low category.
Across its five positive phase 3 studies in China, iza-bren has demonstrated PFS benefits in the range of 50% to 60% in nasopharyngeal cancer, esophageal cancer, triple-negative breast cancer, HR+/HER2- breast cancer and EGFR-mutant NSCLC. Massacesi said these findings provide BMS with confidence in its ongoing global phase 3 trials.
Iza-Bren Delivers Positive Phase 3 Clinical Trial Results
Iza-Bren, also known as izalontamab brengitecan, has delivered encouraging Phase 3 clinical trial results in lung and breast cancer, strengthening Bristol Myers Squibb’s (BMS) position in oncology research. Developed by SystImmune and its parent company, Sichuan Biokin Pharmaceutical, Iza-Bren is an investigational bispecific antibody-drug conjugate designed to target EGFR and HER3 proteins on cancer cells. The treatment aims to deliver cancer-killing medication directly to tumors, potentially improving effectiveness while managing damage to healthy tissues. Recent results presented around the 2026 European Society for Medical Oncology (ESMO) Congress have increased interest in its potential across multiple cancer types.
