Alphamab Oncology Announces Biparatopic HER2-targeting ADC JSKN003 Was Granted Breakthrough Therapy Designation by the FDA for the Treatment of PROC

SUZHOU, China, Dec. 20, 2025 /PRNewswire/ -- Alphamab Oncology (stock code: 9966.HK) announced that the biparatopic HER2-targeting antibody-drug conjugate (ADC) JSKN003, 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), has been granted breakthrough therapy designation (BTD) by the U.S. Food and Drug Administration (FDA) for the treatment of adult patients with advanced or metastatic platinum-resistant recurrent epithelial ovarian cancer, primary peritoneal, or fallopian tube cancers (PROC) expressing HER2 (IHC 1+, 2+ and 3+) who have received prior treatment with bevacizumab.

Previously, JSKN003 has received approval from FDA to initiate a phase II clinical study for the treatment of PROC not restricted by HER2 expression, has been granted Fast Track Designation (FTD) by the FDA for PROC and has been granted Orphan Drug Designation (ODD) by the FDA for gastric cancer and gastroesophageal junction cancer (GC/GEJ). It has also been granted BTDs by the Center for Drug Evaluation (CDE) of the National Medical Products Administration of China (NMPA) for both PROC and colorectal cancer (CRC). The grant of this BTD further demonstrates the international regulatory community's recognition of JSKN003's clinical potential and its importance as a novel therapeutic candidate. The phase III clinical trial of JSKN003 for the treatment of PROC in China is currently undergoing smoothly.

The grant of BTD for JSKN003 is based on the pooled analysis of the phase I clinical study in Australia (JSKN003-101, NCT05494918) and the phase I/II clinical study in China (JSKN003-102, NCT05744427). The relevant efficacy and safety data of PROC were released at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting.

Ovarian cancer (OC) is one of the most common malignant tumors of the female reproductive system. Most patients are diagnosed at an advanced stage, and the disease is characterized by a high recurrence rate and significant treatment challenges. The standard treatment regimens recommended by authoritative guidelines both domestically and internationally include surgery combined with platinum-based chemotherapy and targeted therapy maintenance. However, about 80% of OC cases recur, and eventually progress to PROC, leaving patients with limited effective treatment options and poor prognosis. The U.S. National Comprehensive Cancer Network (NCCN) recommended single-agent non-platinum chemotherapy with or without bevacizumab as preferred regimens for PROC. However, these non-platinum chemotherapies demonstrate limited efficacy, with an objective response rate (ORR) of only 10% to 15%, a median progression-free survival (mPFS) of only 3 to 4 months, and a median overall survival (OS) of approximately 12 months, highlighting an urgent need for new treatment options. The grant of BTD by FDA will further expedite the clinical development and regulatory review of JSKN003 and bring new choice to patients with PROC worldwide.

About JSKN003

JSKN003 is developed by site-specific conjugation to the Fc glycans of anbenitamab, resulting in a homogeneous and stable ADC with a DAR of 4. JSKN003 binds to two HER2 epitopes on tumor cells and release topoisomerase I inhibitors through cellular endocytosis, exerting anti-tumor effects.

Compared to similar ADCs, JSKN003 demonstrates better serum stability, reduced hematological toxicity, and stronger tumor inhibition and bystander effect, resulting in significantly wider therapeutic window.

Multiple registrational studies of JSKN003 are ongoing, including trials in HER2-positive breast cancer (BC), all-comer platinum-resistant ovarian cancer (PROC), HER2-low BC, and HER2-positive colorectal cancer (CRC).

JSKN003 has been granted Orphan Drug Designation (ODD) by the U.S. Food and Drug Administration (FDA) for gastric cancer (GC) and gastroesophageal junction cancer (GEJ), has been granted Fast Track Designation (FTD) by the FDA for the treatment of advanced or metastatic platinum-resistant recurrent epithelial ovarian cancer, primary peritoneal cancer, or fallopian tube cancer (PROC), not restricted by HER2 expression, has been granted Breakthrough Therapy Designation (BTD) by the FDA for the treatment of patients with HER2-expressing PROC who have received prior treatment with bevacizumab. It has also been granted two BTDs by the National Medical Products Administration (NMPA) for PROC and HER2-positive advanced CRC that has failed prior oxaliplatin, fluorouracil, and irinotecan therapy.

In September 2024, the Company entered a licensing agreement with JMT-Bio Technology Co., Ltd. ("JMT-Bio"), a wholly-owned subsidiary of CSPC Pharmaceutical Group Co., Ltd. ("CSPC") (stock code: 1093.HK). JMT-Bio was granted the exclusive license and sublicense rights to develop, sell, offer for sale and commercialize JSKN003, for tumor-related indications in mainland China (excluding Hong Kong, Macau or Taiwan). Alphamab retains exclusive production rights for JSKN003.

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. Four 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, delivering China-innovated cancer therapies to benefit patients worldwide.

SOURCE Alphamab Oncology