Alphamab Oncology announced that its anti-HER2 biparatopic antibody-drug conjugate (ADC) JSKN003 has received Orphan Drug Designation from the U.S. Food and Drug Administration for the treatment of gastric cancer and gastroesophageal junction cancer (GC/GEJ). The designation represents a significant regulatory milestone that will provide multiple development and commercialization advantages for the innovative cancer therapy.
Addressing Critical Unmet Medical Need
Gastric and gastroesophageal junction cancers represent the fifth most common cancer and fifth leading cause of cancer death worldwide. According to the 2022 Global Cancer Statistics report from the International Agency for Research on Cancer, approximately 960,000 new cases are diagnosed globally each year, resulting in 660,000 deaths annually.
In the United States, the SEER database model predicts 26,890 new cases and 10,880 deaths from GC/GEJ in 2024, with a five-year overall survival rate of less than 40%. Current treatment options remain limited, with fluoropyrimidine and platinum-based regimens serving as standard first-line treatments. Second-line and later-line options, including paclitaxel plus ramucirumab, paclitaxel, docetaxel or irinotecan monotherapy, achieve objective response rates of only 15-25%. Median overall survival remains poor at approximately 8-9 months for second-line treatment and 4-6 months for later lines.
Innovative ADC Technology Platform
JSKN003 is developed using Alphamab's proprietary glycan-specific conjugation platform, featuring the antibody molecule KN026 that is site-specifically modified through enzyme catalytic reaction and click chemistry to achieve a drug-to-antibody ratio of approximately 4. The biparatopic ADC binds HER2 on tumor cell surfaces and releases topoisomerase I inhibitors through cellular endocytosis to exert anti-tumor effects.
Compared to other ADC counterparts, JSKN003 demonstrated superior serum stability and stronger bystander effect, which effectively expands the therapeutic window. These characteristics potentially address key limitations of existing ADC therapies and may improve treatment outcomes for patients with HER2-expressing cancers.
Promising Clinical Results
Research results from two Phase I clinical studies have demonstrated favorable tolerability and safety profiles for JSKN003. The Phase I study JSKN003-101 (NCT05494918) conducted in Australia and the Phase I/II study JSKN003-102 (NCT05744427) in China showed promising efficacy in heavily pretreated patients with advanced solid tumors, particularly those with high HER2-expressing gastrointestinal tumors.
Detailed clinical data were first presented at the 2024 European Society for Medical Oncology Congress and subsequently updated at the 2025 Annual Meeting of American Society of Clinical Oncology in June 2025, highlighting the drug's potential in addressing current treatment gaps.
Regulatory Advantages and Development Path
The Orphan Drug Designation, established under the Orphan Drug Act, encourages development of innovative treatments for diseases affecting fewer than 200,000 people in the United States. For JSKN003, this designation provides substantial benefits including funding for research and development costs, tax credits for clinical trial expenditures, waiver of prescription drug user fees, and accelerated review and approval processes.
Upon potential approval, JSKN003 would receive seven years of market exclusivity in the United States, providing significant commercial advantages for Alphamab Oncology's continued development efforts.
Broader Development Pipeline
Beyond gastric cancer, JSKN003 is being evaluated across multiple cancer types. The company has initiated three Phase III clinical studies for HER2-low expressing breast cancer, platinum-resistant ovarian cancer, and HER2-positive breast cancer, along with multiple exploratory Phase II studies. The drug previously received breakthrough therapy designation from China's Center for Drug Evaluation for treating platinum-resistant recurrent epithelial ovarian cancer, primary peritoneal cancer, or fallopian tube cancer.
In September 2024, Alphamab entered a licensing agreement with JMT-Bio Technology, a subsidiary of CSPC Pharmaceutical Group, granting exclusive development and commercialization rights for JSKN003 in mainland China while retaining sole supply rights.
