Suzhou, China, April 23, 2026 - Alphamab Oncology (stock code: 9966.HK) today announced that the results from a Phase I clinical study (JSKN016-101, NCT06592417) of its first-in-class TROP2/HER3 bispecific antibody-drug conjugate (ADC) JSKN016, for the treatment of HER2-negative locally advanced or metastatic breast cancer (BC), will be presented as a poster at the 2026 American Society of Clinical Oncology (ASCO) Annual Meeting. The 2026 ASCO Annual Meeting will be held from May 29, 2026 to June 2, 2026 (local time) in Chicago, the United States.

JSKN016-101 (NCT06592417) is a dose-escalation and dose-expansion clinical study in China, enrolling patients with advanced solid tumors to receive JSKN016 monotherapy. The 2026 ASCO Annual Meeting will feature the presentation of analytical results from the HER2-negative BC cohort of this study. JSKN016 demonstrated very promising efficacy and superior safety profile in late line BC patients. The results guarantee the further development of JSKN016, in combo with chemo, IO and target therapy, in front line and perioperative settings.

Title: JSKN016, a First-in-Class Anti-TROP2/HER3 Bispecific Antibody-Drug Conjugate (ADC) in Patients (pts) with HER2-Negative Locally Advanced or Metastatic Breast Cancer: Results from a Phase I Study

Abstract Number: 1123

Presentation Type: Poster

Principal Investigator: Professor Herui Yao, Sun Yat-sen Memorial Hospital, Sun Yat-sen University

Presentation Time: June 1, 2026, 1:30-4:30 PM CDT

JSKN016 is a TROP2/HER3 targeting bispecific ADC developed using the proprietary single-domain antibody and bispecific antibody platforms. It is conjugated via site-specific glycosylation to generate a homogeneous and stable ADC with a drug-to-antibody ratio (DAR) of 4. JSKN016 precisely binds to TROP2 and/or HER3 on tumor cells, blocks tumor signaling pathways, and releases topoisomerase I inhibitors for precise and potent antitumor activity. The glycan conjugation technology confers high stability and low off-target toxicity. Clinical studies have demonstrated encouraging antitumor activity and a favorable safety profile of JSKN016 in heavily pretreated advanced triple-negative breast cancer (TNBC) and other solid tumors. Multiple clinical studies of JSKN016 as monotherapy and in combination therapies for lung cancer, breast cancer, and other indications have been initiated. The Phase III clinical study evaluating JSKN016 for the treatment of TNBC is currently ongoing.

About JSKN016

JSKN016 is a TROP2/HER3 targeting bispecific ADC developed using the proprietary single-domain antibody and bispecific antibody platforms. It is conjugated via site-specific glycosylation to generate a homogeneous and stable ADC with a drug-to-antibody ratio (DAR) of 4. JSKN016 binds to TROP2 and/or HER3 on tumor cells and release topoisomerase I inhibitors through cellular endocytosis, exerting anti-tumor effects.

JSKN016 has demonstrated promising antitumor activity and a favorable safety profile across multiple solid tumors. Multiple clinical studies of JSKN016 as monotherapy and in combination therapies for lung cancer, breast cancer, and other indications have been initiated. The Phase III clinical study evaluating JSKN016 for the treatment of triple-negative breast cancer (TNBC) is currently ongoing.

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.

One product has 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. The NMPA has accepted the new drug application for KN026 (Anbenitamab Injection), a HER2 bispecific antibody, for second-line or later HER2-positive gastric cancer, and currently under review. Five bispecific ADC candidates have entered clinical stages, and next-generation ADC pipelines—such as dual-payload ADCs—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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