Zymeworks and BeiGene plan to initiate registration-enabling global studies with ZW25 in HER2-expressing biliary tract cancer (BTC) and gastroesophageal adenocarcinoma (GEA).
The plans are based on new data obtained from a Phase I clinical trial performed in heavily pretreated patients with HER2‑expressing solid tumours.
Based on Zymeworks’ Azymetric platform, ZW25 concurrently binds to two non-overlapping epitopes of HER2, resulting in several mechanisms of action.
Zymeworks is developing the drug to treat solid tumours that express HER2.
The ongoing, three-part Phase I trial assessed the safety, tolerability and effectiveness of ZW25 as a monotherapy and in combination with chemotherapy agents in patients with locally advanced and/or metastatic HER2-expressing cancers.
Data was obtained from 69 patients, except those with breast cancer, treated with 10mg/kg weekly or 20mg/kg every other week dose. At the data cut-off time, 57 of these patients were response evaluable.
Overall disease control rate was 70%, including 44% partial responses and 26% with stable disease. Results showed that 32% of patients achieved disease control for more than six months.
According to the company, nine evaluable patients with BTC experienced a DCR of 78% and an objective response rate (ORR) of 67%.
In addition, 13 patients with colorectal cancer and 23 with GEA had 46% and 39% ORRs, respectively.
Zymeworks added that the confirmed responses were observed across patients with other cancers, including a 100% reduction in target lesions in those with pancreatic cancer.
The overall median progression-free survival was 5.5 months and is said to be evolving.
Further analysis showed that the drug candidate was well-tolerated, with the most common adverse events being diarrhoea, infusion-related reaction and nausea.
BeiGene co-founder, CEO and chairman John Oyler said: “The encouraging clinical data on ZW25 supports further evaluation of this bispecific antibody in HER2-expressing solid tumours.”
ZW25 received fast track status in the US for first-line gastroesophageal adenocarcinoma in combination with standard of care chemotherapy, and orphan drug designation for gastric and ovarian cancers.
