TEVIMBRA plus ZIIHERA and chemotherapy demonstrated statistically significant overall survival benefit with an unprecedented seven-month improvement in first-line HER2+ GEA

Oral presentation at ASCO highlights benefit regardless of PD-L1 status, including in PD-L1 <1%

BeOne Medicines Ltd. (Nasdaq: ONC; HKEX: 06160; SSE: 688235), a global oncology company, today announced that data from HERIZON-GEA-01 were published in The New England Journal of Medicine and will be presented in an oral presentation (Rapid Oral Abstract: 4010) at the American Society of Clinical Oncology (ASCO) Annual Meeting on June 1, 2026, in Chicago. The HERIZON-GEA-01 clinical trial evaluated ZIIHERA^® (zanidatamab) plus chemotherapy, with and without TEVIMBRA^® (tislelizumab), compared with the control arm of trastuzumab plus chemotherapy as first-line treatment for advanced/metastatic HER2+ gastroesophageal adenocarcinoma (GEA).

Dr. Sun Young Rha, Professor of Medical Oncology at the Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea, senior author of the NEJM manuscript and first author of the ASCO abstract, said:

“Results from the HERIZON-GEA-01 published in The New England Journal of Medicine and presented in an oral presentation at ASCO provide new data about the regimen of tislelizumab added to zanidatamab plus chemotherapy, which demonstrated meaningfully improved outcomes for patients with HER2-positive gastroesophageal adenocarcinoma. In particular, the findings show that this regimen resulted in a survival benefit, even in patients with PD-L1 <1%. This combination has the potential to be an important new treatment option in areas of high unmet need in HER2+ GEA.”

Key findings published in The New England Journal of Medicine

• Overall survival (OS): A statistically significant and clinically meaningful improvement in OS with ZIIHERA plus TEVIMBRA and chemotherapy, reaching a median OS of 26.4 months; mOS of 24.4 months was reported with ZIIHERA plus chemotherapy, and 19.2 months with the control arm.
• Progression-free survival (PFS): A statistically significant and clinically meaningful improvement in PFS in both ZIIHERA-containing arms with a median PFS of 12.4 months.
• Duration of Response (DoR): Median DoR of 20.7 months with ZIIHERA and TEVIMBRA plus chemotherapy; median DoR of 14.3 months with ZIIHERA plus chemotherapy and 8.3 months with the control arm.

Dr. Geoffrey Ku, Associate Attending physician on the Gastrointestinal Oncology Service in the Department of Medicine at Memorial Sloan Kettering Cancer Center, author of the NEJM manuscript and the ASCO abstract, said:

“This practice-changing study demonstrates that zanidatamab is clearly superior to trastuzumab, with a manageable safety profile, in HER2-positive GEA. Moreover, the addition of tislelizumab contributes to the prolongation of overall survival and remarkable durability of responses, with benefit in both PD-L1 positive and negative tumors. If approved, the combination of zanidatamab, tislelizumab and chemotherapy should become the standard of care in untreated metastatic or locally advanced HER2-positive GEA patients irrespective of the tumor PD-L1 status.”

Oral presentation with new data at ASCO 2026 demonstrates benefit regardless of PD-L1 status

• With 26 months of follow-up, ZIIHERA plus TEVIMBRA and chemotherapy meaningfully improved PFS and OS were observed in both PD-L1-positive and PD-L1-negative patients compared with the control arm; data were consistent between tumor area positivity (TAP) and combined positive score (CPS).
• In PD-L1 TAP <1% and ≥1% patients, the 18-month PFS was 50.3% and 42.6%, respectively, and the 24-month OS was 63.7% and 53.5% with ZIIHERA plus TEVIMBRA and chemotherapy.
• In PD-L1-negative patients (TAP <1%), median OS was 29.7 months with ZIIHERA plus TEVIMBRA and chemotherapy compared with 15.8 months with the control arm. In PD-L1-positive patients (TAP≥1%), median OS was 26.4 months with ZIIHERA plus TEVIMBRA and chemotherapy compared with 21.2 months in the control arm. Findings were consistent across PD-L1 assessment methods.
• In TAP<1%, the ZIIHERA plus TEVIMBRA and chemotherapy regimen resulted in a mPFS of 18.5 months compared with mPFS of 7.9 months in the control arm, while in TAP≥1% patients, the mPFS was 11.3 months vs. mPFS of 8.3 months in the control arm

Mark Lanasa, M.D., Ph.D., Chief Medical Officer, Solid Tumors at BeOne Medicines, said:

“The HERIZON-GEA-01 results – now published in The New England Journal of Medicine with a detailed sub-group analysis presented in an oral session at ASCO – strengthen the evidence supporting the role of TEVIMBRA in driving a sustained and statistically significant overall survival benefit. With a median OS of more than 26 months, unprecedented in this disease, the TEVIMBRA-containing arm is positioned as a compelling new therapeutic approach in a disease where there remains a critical unmet need.”

The safety findings for the ZIIHERA plus TEVIMBRA and chemotherapy arm were generally consistent with the known effects of HER2-directed therapy and immunotherapy, and no new safety signals were identified. Diarrhea was the most common Grade ≥3 treatment-related adverse event (TRAE) in 24.5% of patients with ZIIHERA plus TEVIMBRA and chemotherapy, 20.0% of patients in the ZIIHERA plus chemotherapy arm, and 12.9% in the trastuzumab plus chemotherapy arm, noting that the median treatment duration was longest for the triplet arm at 43.1 weeks (vs. 31.0 weeks with ZIIHERA plus chemotherapy and 30.0 weeks in the control arm). A mandatory anti-diarrheal prophylaxis was established during the first cycle, and discontinuation rates due to drug-related diarrhea were relatively low at 4.1%, 1.3%, and 0% of patients, respectively, with most diarrhea events occurring early in the trial.

Regulatory Status

The U.S. FDA has accepted a supplemental Biologics License Applications (sBLA) for TEVIMBRA and has granted it priority review. In addition, the Center for Drug Evaluation (CDE) of China’s National Medical Products Administration (NMPA) has accepted sBLAs for ZIIHERA and for TEVIMBRA for the first-line treatment of advanced/metastatic HER2+ GEA. BeOne holds the rights to ZIIHERA in Asia (excluding India and Japan), Australia, and New Zealand, and intends to work with authorities in these markets to expedite regulatory submissions.

About the HERIZON-GEA-01 Phase 3 Trial

HERIZON-GEA-01 (NCT05152147) is a global, randomized, open-label Phase 3 trial, conducted jointly with Jazz Pharmaceuticals, to evaluate and compare the efficacy and safety of ZIIHERA plus chemotherapy, with and without TEVIMBRA, to the standard of care (trastuzumab plus chemotherapy) as first-line treatment for adult patients with advanced/metastatic HER2+ GEA. The trial randomized 914 patients from approximately 300 trial sites in more than 30 countries. Patients for this trial had unresectable locally advanced, recurrent or metastatic HER2+ GEA (adenocarcinomas of the stomach or esophagus, including the gastroesophageal junction), defined as 3+ HER2 expression by IHC or 2+ HER2 expression by IHC with ISH positivity per central assessment. Patients were randomized to the three trial arms: ZIIHERA in combination with chemotherapy and TEVIMBRA; ZIIHERA in combination with chemotherapy; and trastuzumab plus chemotherapy. The trial is evaluating dual primary endpoints, PFS per blinded independent central review (BICR) and OS.

About Gastroesophageal Adenocarcinoma

Gastroesophageal adenocarcinoma (GEA), which includes cancers of the stomach, gastroesophageal junction, and esophagus, is the fifth most common cancer worldwide. Approximately 20% of GEA patients have HER2-positive disease.^1,2,3, which has high morbidity and mortality, and patients are urgently in need of new treatment options. The overall prognosis for patients with GEA remains poor, with a global five-year survival rate of less than 30% for gastric cancer and about 19% for GEA.⁴

About ZIIHERA (zanidatamab)

ZIIHERA (zanidatamab) is a bispecific human epidermal growth factor receptor 2, or HER2-directed antibody that binds to two extracellular sites on HER2. Binding of zanidatamab with HER2 results in internalization leading to a reduction in HER2 expression of the receptor on the tumor cell surface. Zanidatamab induces complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC) and antibody-dependent cellular phagocytosis (ADCP). These mechanisms result in tumor growth inhibition and cell death in vitro and in vivo.⁵

Zanidatamab is being developed in multiple clinical trials as a targeted treatment option for patients with solid tumors that express HER2. Zanidatamab is approved in China for the treatment of patients who have unresectable, locally advanced, or metastatic HER2-high expression (IHC 3+) biliary tract cancer (BTC) and who have received prior systemic therapy. ZIIHERA has also been granted accelerated approval in the U.S. and conditional marketing authorization in the European Union for eligible BTC patients. Zanidatamab is being developed by Jazz and BeOne under license agreements from Zymeworks, which first developed the molecule. BeOne has licensed zanidatamab from Zymeworks in Asia (excluding India and Japan), Australia and New Zealand. Jazz Pharmaceuticals has rights in all other regions.

ZIIHERA is a registered trademark of Zymeworks BC Inc.

About TEVIMBRA (tislelizumab)

TEVIMBRA is a uniquely designed humanized immunoglobulin G4 (IgG4) anti-programmed cell death protein 1 (PD-1) monoclonal antibody with high affinity and binding specificity against PD-1. It is designed to minimize binding to Fc-gamma (Fcγ) receptors on macrophages, helping to aid the body’s immune cells to detect and fight tumors.

TEVIMBRA is the foundational asset of BeOne’s solid tumor portfolio and has shown potential across multiple tumor types and disease settings. The global TEVIMBRA clinical development program includes almost 15,000 patients enrolled to date in 30+ countries and regions across 71 trials, including 21 registration-enabling studies. TEVIMBRA is approved in over 50 countries, and more than 2 million patients have been treated globally.

Select Important Safety Information

Serious and sometimes fatal adverse reactions occurred with TEVIMBRA treatment. Warnings and precautions include severe and fatal immune-mediated adverse reactions, including pneumonitis, colitis, hepatitis, endocrinopathies, dermatologic adverse reactions, nephritis with renal dysfunction, and solid organ transplant rejection. Other warnings and precautions include infusion-related reactions, complications of allogeneic HSCT, and embryo-fetal toxicity.

Please see full U.S. Prescribing Information including the U.S. Medication Guide.

The information in this press release is intended for a global audience. Product indications vary by region.

About BeOne

BeOne Medicines is a global oncology company that is discovering and developing innovative treatments for cancer patients worldwide. With a portfolio spanning hematology and solid tumors, BeOne is expediting development of its diverse pipeline of novel therapeutics through its internal capabilities and collaborations. The Company has a growing global team spanning six continents who are driven by scientific excellence and exceptional speed to reach more patients than ever before. To learn more about BeOne, please visit www.beonemedicines.com and follow us on LinkedIn, X, Facebook and Instagram.

Forward-Looking Statement

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 and other federal securities laws, including statements regarding the potential benefits of ZIIHERA and TEVIMBRA; the potential of TEVIMBRA plus ZIIHERA and chemotherapy to become an important new treatment option; BeOne’s plans to work with authorities in certain markets to expedite regulatory submissions; BeOne’s expectations regarding ZIIHERA’s and TEVIMBRA’s clinical development and regulatory milestones; and BeOne’s plans, commitments, aspirations, and goals under the heading “About BeOne.” Actual results may differ materially from those indicated in the forward-looking statements as a result of various important factors, including BeOne's ability to demonstrate the efficacy and safety of its drug candidates; the clinical results for its drug candidates, which may not support further development or marketing approval; actions of regulatory agencies, which may affect the initiation, timing, and progress of clinical trials and marketing approval; BeOne's ability to achieve commercial success for its marketed medicines and drug candidates, if approved; BeOne's ability to obtain and maintain protection of intellectual property for its medicines and technology; BeOne's reliance on third parties to conduct drug development, manufacturing, commercialization, and other services; BeOne’s limited experience in obtaining regulatory approvals and commercializing pharmaceutical products and its ability to obtain additional funding for operations and to complete the development of its drug candidates and achieve and maintain profitability; and those risks more fully discussed in the section entitled “Risk Factors” in BeOne’s most recent quarterly report on Form 10-Q, as well as discussions of potential risks, uncertainties, and other important factors in BeOne's subsequent filings with the U.S. Securities and Exchange Commission. All information in this press release is as of the date of this press release, and BeOne undertakes no duty to update such information unless required by law.

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