Suzhou, China, June 11, 2026 - Alphamab Oncology (stock code: 9966.HK) today announced that HER2 bispecific antibody Anbenitamab (brand name: 恩尼妥^® , KN026), independently developed by the Company, and co-developed with JMT-Bio Technology Co., Ltd., a wholly-owned subsidiary of CSPC Pharmaceutical Group Co., Ltd. (stock code: 1093.HK), in combination with CSPC’s Docetaxel for Injection (Albumin-bound) (HB1801), has successfully met the pre-specified primary endpoint of progression-free survival (PFS) as assessed by the Independent Data Monitoring Committee (IDMC) in a Phase III clinical study (KN026-003, NCT05838066) for first-line treatment of HER2-positive advanced breast cancer, and has shown a trend toward overall survival (OS) benefit.

The study showed that KN026 in combination with HB1801 significantly prolonged PFS as compared with the current standard of care (trastuzumab plus pertuzumab and docetaxel, i.e., the THP regimen), with the superiority being both statistically significant and clinically meaningful benefits, coupled with a favorable safety profile. This combination therapy is expected to become the preferred first-line treatment option for patients with HER2-positive advanced breast cancer. Detailed data from the study will be presented at an upcoming international academic conference.

Innovative Dual‑Epitope Blockade Mechanism

Full Treatment-Cycle Coverage of HER2‑Positive Breast Cancer

KN026 is a HER2 bispecific antibody independently developed by the Company using the proprietary CRIB (Charge Repulsion Induced Bispecific) platform. Anbenitamab can simultaneously and precisely bind to two non‑overlapping epitopes of the HER2 receptor (domain IV and domain II). By specifically binding to multiple HER2 proteins on the tumor cell membrane, KN026 comprehensively blocks downstream signaling pathways, making it a landmark innovative drug in the HER2‑targeted field. In May 2026, KN026 obtained marketing approval in China through the priority review and approval process of the National Medical Products Administration (NMPA), offering a potentially practice‑changing new option for second‑line treatment of HER2‑positive gastric cancer.

In breast cancer, KN026 in combination with HB1801 has completed the full treatment-cycle clinical development layout covering neoadjuvant, adjuvant, and first‑line treatment of HER2‑positive breast cancer. The positive primary endpoint achieved in this first-line Phase III trial provides further solid evidence of efficacy, following the breakthrough positive results from the neoadjuvant Phase III study (KN026‑004) of the same combination regimen.

To date, KN026 has achieved strong positive results in three consecutive Phase III studies, demonstrating its major clinical value as a front‑runner among HER2 bispecific antibodies.

Head‑to‑Head Challenge Against Global Standard of Care

A Historic Breakthrough in First‑Line Therapy

Breast cancer ranks among the top high-incidence malignant tumors among women in China, with the HER2-positive subtype accounting for approximately 20% to 30% of cases. In China, approximately 20% of patients with breast cancer are already at an advanced stage upon initial diagnosis, and approximately 10% of patients with HER2-positive early breast cancer experience disease recurrence within three years after radical surgery. The THP regimen remains the preferred first-line treatment for HER2-positive advanced breast cancer globally. Although the THP regimen has significantly prolonged PFS in such patients, approximately 50% of patients still experience disease progression within two years. Prolonging PFS and improving long‑term survival remain the primary treatment goals in this setting.

KN026-003 is a randomized, controlled, open‑label, multi-center Phase III clinical study designed to enroll approximately 880 patients with HER2‑positive advanced breast cancer. Patients were randomized 1:1 to receive either the investigational regimen (KN026 plus HB1801) or the control regimen (THP). The primary endpoint is PFS assessed by blinded independent review committee (BIRC). This is the world’s first head‑to‑head Phase III study of a HER2 bispecific antibody‑based combination therapy that has successfully demonstrated superior efficacy over the THP regimen in first‑line HER2‑positive advanced breast cancer, achieving a historic breakthrough in this field.

Three Core Advantages

Poised to Reshape the First‑Line Treatment Landscape

●   Superior Efficacy: The KN026 plus HB1801 regimen significantly prolongs PFS compared to the current standard of care, offering a more pronounced clinical benefit.

●   Better Safety: Although trastuzumab deruxtecan plus pertuzumab has shown success in first‑line HER2‑positive advanced breast cancer, it carries a risk of fatal interstitial lung disease. KN026, as a HER2 bispecific antibody, avoids the interstitial lung disease events associated with ADCs. Moreover, it has a better safety profile compared to ADCs, making it more suitable for long‑term treatment, especially during the maintenance phase after combination chemotherapy. In addition, the non-ADC antibody regimen in the first‑line setting preserves the opportunity for subsequent ADC therapy, enabling a “first‑line bispecific antibody, second‑line ADC” sequencing strategy that may extend patients’ high‑quality overall survival and improve full‑course treatment benefits.

●   More Convenient Dosing: KN026 requires shorter infusion time than the sequential infusion of trastuzumab plus pertuzumab, offering greater treatment convenience. HB1801 can be infused rapidly at high concentration without the need for corticosteroid premedication, which is more convenient than conventional docetaxel.

This major advance further solidifies the core position of the KN026 plus HB1801 combination in the full treatment-cycle of HER2‑positive breast cancer. Alphamab Oncology will continue to advance the subsequent development and regulatory submission of this combination therapy, striving to provide Chinese breast cancer patients with a more effective, safer, and more convenient new treatment option as soon as possible, and to help upgrade the precision treatment of breast cancer in China.

About 恩尼妥^® (Anbenitamab Injection)

恩尼妥^® (Anbenitamab injection, KN026) is an anti-HER2 bispecific antibody independently developed by the Company using the proprietary Fc-based heterodimer bispecific platform technology called CRIB (Charge Repulsion Induced Bispecific). Anbenitamab can simultaneously bind two non-overlapping epitopes of HER2, resulting in HER2 signal blockade. Through antibody-induced receptor clustering, it enhances antibody-dependent cell-mediated cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) effects while promoting the down-regulation of HER2 receptors on the cell surface.

In May 2026, 恩尼妥^® obtained approval for marketing from the National Medical Products Administration of China (NMPA) through the priority review and approval pathway for combination with chemotherapy for the treatment of adult patients with locally advanced or metastatic HER2 positive gastric cancer/gastroesophageal junction cancer (GC/GEJ) who have previously received at least one trastuzumab-containing regimen. The Phase III clinical study of neoadjuvant treatment for HER2-positive breast cancer has reached its primary endpoint, and a New Drug Application (NDA) will be submitted in the near future. Currently, multiple registrational clinical trials of Anbenitamab for indications such as first-line treatment of HER2-positive breast cancer, adjuvant treatment of HER2-positive breast cancer and first-line treatment of HER2-positive GC/GEJ are ongoing.

Anbenitamab has been granted Orphan Drug Designation by the U.S. Food and Drug Administration (FDA) for the treatment of HER2-positive or low expressing GC; it has been granted Breakthrough Therapy Designation by NMPA for the treatment of patients with HER2-positive GC/GEJ who have failed first-line standard treatment.

In August 2021, the Company entered an agreement with JMT-Bio Technology Co., Ltd. (JMT-Bio), a wholly-owned subsidiary of CSPC Pharmaceutical Group Co., Ltd. (CSPC) (stock code: 1093.HK), for the development and commercialization of KN026 in Mainland China. JMT-Bio was granted exclusive license rights of KN026 for the development and commercialization in the indications of BC and GC/GEJ in Mainland China (excluding Hong Kong, Macau and Taiwan).

About Docetaxel (Albumin-bounded) HB1801

Docetaxel (Albumin-Bound) for Injection (HB1801) is one of the flagship drugs independently developed by CSPC Group on its proprietary nanomedicine technology platform. With docetaxel encapsulated in human serum albumin and free of Tween-80 and ethanol, HB1801 has the following advantages over conventional docetaxel injection: (1) Safety: No steroid premedication is needed. It can be rapidly administered at high concentrations, featuring superior safety and better patient compliance; (2) Efficacy: It has exhibited remarkable efficacy in multiple preclinical tumor models and several early-stage clinical studies. Higher doses can be applied clinically to further improve therapeutic outcomes. HB1801 has currently entered pivotal phase III registrational clinical trials for indications including breast cancer and gastric cancer.

About Alphamab Oncology

Alphamab Oncology (Stock Code: 9966.HK) is an innovative biopharmaceutical company focused on oncology. Leveraging proprietary platforms-including single-domain antibodies, bispecific antibodies, glycan-specific conjugation, linker-payloads, dual-payload ADCs, and high-concentration subcutaneous formulations, the Company has built a differentiated and globally competitive pipeline, covering cutting-edge candidates in ADCs, bispecific antibodies, and single-domain antibodies.

Two products have received market approval: Envafolimab (KN035, brand name: 恩维达^®), the world's first subcutaneously injected PD-(L)1 inhibitor, offering greater convenience and accessibility in cancer treatment; and Anbenitamab (KN026, brand name: 恩尼妥^®), the first domestically developed HER2 bispecific antibody approved for marketing in China, redefining the standard of treatment for second‑line HER2‑positive gastric cancer. Six bispecific ADC, dual-payload ADC candidates have entered clinical stages, and next-generation ADC pipelines are advancing rapidly. The Company has established strategic partnerships with organizations including CSPC, ArriVent, and Glenmark, covering both product development and technology platforms.

Our overarching mission is to make cancer manageable and curable by addressing unmet clinical needs in oncology. Alphamab Oncology is continuously dedicated to the development of effective, safe, and globally competitive anti-tumor drugs, enabling patients to achieve long-term, high-quality survival and delivering China-innovated cancer therapies to benefit patients worldwide.

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