Ambrx Granted Orphan Drug Designation for ARX788 for the Treatment of Gastric Cancer

SAN DIEGO, Calif., March 17, 2021 – Ambrx, a clinical stage biopharmaceutical company using an expanded genetic code to create Engineered Precision Biologics, today announced that the U.S. Food and Drug Administration (FDA) has granted the company orphan drug designation for ARX788 for the treatment of patients with HER2-positive gastric cancer, including cancer at the gastroesophageal junction.

The FDA’s Office of Orphan Drug Products grants orphan status to support the development of medicines for underserved patient populations, or rare disorders, that affect fewer than 200,000 people in the U.S. Orphan drug designation for ARX788 for gastric cancer provides Ambrx with certain benefits, including an exemption to FDA prescription drug user fees and tax credits for qualified clinical trials. Orphan drug designation also confers eligibility for seven years of market exclusivity to an orphan drug post-approval, subject to receiving marketing approval from the FDA.

“The ongoing Phase 1 ACE-Gastric-01 trial has shown promising anti-tumor activity in HER2-positive advanced gastric patients who have been previously treated with trastuzumab and chemotherapy in the metastatic setting,” said Feng Tian, Ph.D., President and CEO of Ambrx. “Receiving orphan drug designation from the FDA is an important milestone in our ongoing efforts to develop ARX788 for a wide range of HER2-positive cancers. We are proud to be targeting a rare disease that is currently severely underserved by advancing ARX788 into additional clinical trials.”

The company anticipates the release of additional Phase 1 data from the ACE-Gastric-01 trial by the end of 2021 and initiation of ACE-Gastric-02, a global Phase 3 trial for HER2-positive gastric cancer, in the second half of 2021. ACE-Gastric-02 is currently planned to be a randomized trial of ARX788 versus physician’s choice of treatment in second line HER2-positive gastric cancer and HER2-positive cancer at the gastroesophageal junction.

About ARX788
ARX788 is a homogeneous and highly stable antibody drug conjugate (ADC) targeting the HER2 receptor. ARX788 is an Engineered Precision Biologic ADC that consists of two cytotoxic payloads site-specifically conjugated to a Herceptin® (trastuzumab)-based antibody. ARX788 was designed to maximize potential anti-tumor activity by optimizing the number and position of the payloads and the chemical bonds that conjugate the cytotoxic AS269 payloads to the antibody. AS269 is a proprietary tubulin inhibitor specifically designed to form a highly stable covalent bond with our synthetic amino acids, a fundamental step in the creation of an Engineered Precision Biologic ADC. Ambrx licensed the China rights to ARX788 to its partner NovoCodex.

About HER2-positive Gastric Cancer
Human epidermal growth factor receptor 2 (HER2) is a tyrosine kinase receptor growth-promoting protein found on the surface of some cancer cells. Gastric cancer with HER2 overexpression has shown aggressive biological behavior, with higher frequencies of disease recurrence in HER2-positive tumors. The frequency of HER2 overexpression in gastric cancer, and cancer at the gastroesophageal junction, range widely with an average of 20% expression. The heterogeneity within gastric tumors and poor treatment options shows an unmet medical need for patients with HER2-positive advanced gastric cancer.

About Ambrx
Ambrx is a clinical stage biopharmaceutical company using an expanded genetic code platform to create Engineered Precision Biologics. These include next generation antibody drug conjugates (ADCs), bispecifics, targeted immuno-oncology therapies, novel cytokines to modulate the immune system, and long-acting therapeutic peptides for metabolic and cardiovascular disease. Ambrx is advancing a robust portfolio of clinical and preclinical programs optimized for efficacy, safety and ease of use, in multiple therapeutic areas, including its lead product candidate ARX788. In addition, the company has collaborations with Bristol Myers Squibb, Astellas, BeiGene, Sino Biopharma, Elanco and NovoCodex, for drug candidates generated using Ambrx technology. For additional information, please visit


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