Anti-HER2 Biparatopic ADC JSKN003 Has Been Granted Breakthrough-Therapy Designation for the Treatment of PROC

Alphamab Oncology (stock code: 9966.HK) and CSPC Pharmaceutical Group Co., Ltd. ("CSPC") (Stock Code: 1093.HK) jointly announced that anti-HER2 biparatopic antibody-drug conjugate (ADC) JSKN003 has been granted Breakthrough Therapy Designation by the Center for Drug Evaluation (CDE) of the National Medical Products Administration (NMPA). The designation is for the treatment of platinum-resistant recurrent epithelial ovarian cancer (PROC), primary peritoneal cancer, or fallopian tube cancer, not restricted to HER2 expression levels.

Ovarian cancer (OC) ranks as the third most common gynecologic malignancy in China and continues to show a rising incidence, with the highest mortality rate among all malignant gynecologic tumors. 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 platinum-resistant ovarian cancer (PROC), leaving patients with limited effective treatment options and poor prognosis. Non-platinum chemotherapy, with or without bevacizumab, is the standard treatment for PROC. Previous studies have shown that the objective response rate (ORR) of PROC treated with non-platinum chemotherapy is only 10% to 15%. The median progression-free survival (PFS) is only 3 to 4 months, and the median overall survival (OS) approximately 12 months, highlighting an urgent need for new treatment options.

The grant of Breakthrough Therapy Designation is based on the pooled analysis of two clinical studies, JSKN003-101 and JSKN003-102. JSKN003-101 (NCT05494918) is an open-label, multicenter, dose-escalation Phase I clinical study conducted in Australia, enrolling patients with advanced solid tumors expressing HER2 (IHC≥1+) or with HER2 mutations. JSKN003-102 (NCT05744427) is a Phase I/ II study conducted in China. The Phase I part enrolled patients with histologically confirmed HER2 expression (IHC≥1+) or HER2 mutations advanced solid tumors. The Phase II part enrolled patients with advanced solid tumors regardless of HER2 expression or mutation status. Pooled results have demonstrated that JSKN003 monotherapy has a favorable tolerability and safety profile, with promising efficacy signals in patients with advanced PROC, and the efficacy was observed across patients with (IHC 1+/2+3+) or without (IHC 0) HER2 expression, with or without prior bevacizumab and prior PARP inhibitor. Preliminary data from the pooled analysis of these two studies were presented at the 2024 European Society for Medical Oncology (ESMO) Congress.

The Phase III clinical study of JSKN003 for this indication is currently in the enrollment phase and the study is progressing smoothly. As a novel bispecific ADC, JSKN003 leverages the synergistic mechanism of enzyme catalysis and click chemistry to enhance serum stability and bystander effects, while demonstrating superior efficacy. The grant of Breakthrough Therapy Designation is expected to accelerate the clinical development, review and approval process of JSKN003, enabling more patients with PROC to benefit sooner.

About JSKN003

JSKN003 is an anti-HER2 bispecific antibody-drug conjugate (bis-ADC), which is developed inhouse with Alphamab's proprietary Glycan-specific conjugation platform. JSKN003 can bind HER2 on the surface of tumor cells and release topoisomerase I inhibitors (TOPIi) through cellular endocytosis, thereby exert anti-tumor effects. Compared with its ADC counterparts, JSKN003 demonstrated better serum stability and stronger bystander effect, which effectively expands the therapeutic window.

Multiple clinical studies at various stages of JSKN003 are currently being conducted in China and Australia. Clinical research results have demonstrated favorable tolerability and safety profile, with promising efficacy of JSKN003 in heavily pretreated patients with advanced solid tumors, especially in patients with HER2-expressing breast cancer, platinum-resistant ovarian cancer (PROC), or high HER2-expressing solid tumors.

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), pursuant to which, JMT-Bio was granted the exclusive license and sublicense rights to develop, sell, offer for sale and commercialize JSKN003, for the treatment of tumor-related indications (the "Field") in mainland China (excluding Hong Kong, Macau or Taiwan) (the "Territory") and become the sole marketing authorization holder for JSKN003 for the Field in the Territory. Alphamab retains the sole right to supply JSKN003.

About Alphamab Oncology

Alphamab Oncology is a leading biopharmaceutical company committed to the development, manufacturing, and commercialization of cutting-edge biotherapeutics for the treatment of cancer. On December 12, 2019, the company was successfully listed on the Main Board of the Hong Kong Stock Exchange, trading under the stock code 9966.

Our integrated platform seamlessly combines research, development, and manufacturing capabilities for biologics. We take pride in our extensive intellectual property portfolio, which encompasses protein/antibody engineering, antibody screening, and multi-module/multi-functional antibody modification.

Distinguished by a globally competitive pipeline, Alphamab Oncology specializes in antibody-drug conjugation (ADC), single domain antibody, and bispecific antibodies. Notably, Envafolimab, the world's first subcutaneously injectable PD-L1 inhibitor, was approved by Chinese authorities in 2021, making a significant breakthrough in the convenience and accessibility of cancer treatment. Three assets are currently undergoing Phase III or pivotal clinical trials, and several other bispecific ADC new drug candidates are in early clinical stage. Multiple strategic collaborations based on innovative products or technology platforms have been established with partners such as CSPC, Arrivent, and Glenmark.

Our overarching mission is to make cancer manageable and curable by addressing unmet clinical needs in oncology. Alphamab Oncology is dedicated to the development of safe, effective and affordable drugs, leveraging a global competitive edge.