The confirmed objective response rate is 37.9% (95% confidence interval [CI]: 20.7%-57.7%) and the disease control rate is 55.2% (95% CI: 35.7%-73.6%). With a median follow up of 10 months, the median progression-free survival and overall survival are 4.1 (95% CI: 1.4-6.4) and 10.7 months (95% CI: 4.8-not reached), respectively. The median duration of response is 8.4 (95% CI: 2.1-18.9) months. ARX788 is well tolerated and has promising anti-tumor activity in patients with HER2-positive advanced gastric adenocarcinoma.

Ambrx...today announced that NovoCodex Pharmaceuticals Ltd. (NovoCodex), Ambrx’s partner in China, presented positive interim data from the ACE-Gastric-01 Phase 1 clinical study of ARX788 for the treatment of HER2+ metastatic gastric / gastroesophageal junction (GEJ) cancer at The Chinese Society of Clinical Oncology (CSCO)...Demonstrated overall response rate (ORR) of 44.4% (12/27) in the response-evaluable patients across all three cohorts (1.3 mg/kg, 1.5 mg/kg, 1.7 mg/kg every three weeks). Low drug-related severe adverse events (SAE) occurred in 6.7% (2/30) of all treated patients across all three cohorts (1.3 mg/kg, 1.5 mg/kg, 1.7 mg/kg every three weeks). Drug-related grade 3 and above adverse events (AEs) comprised only 10% (3/30).

ARX788 was well tolerated with promising antitumor activity in patients with HER2-positive advanced gastric and GEJ adenocarcinoma.

ARX788 was effective in T-DM1-resistant in vitro and in vivo models of HER2-positive breast cancer and gastric cancer. ARX788 showed a pronounced growth inhibitory effect on all five HER2-positive cell lines tested, of which two gastric cancer cell lines had acquired resistance to T-DM1. ARX788 evoked more apoptotic events compared to T-DM1. Mice treated with ARX788 survived longer than those treated with T-DM1.