A collaboration between Zymeworks and BeiGene has expanded the Phase III HERIZON‑GEA‑01 clinical trial of zanidatamab for treating gastroesophageal adenocarcinomas to Asia.

BeiGene dosed the first subject of the trial in South Korea.

A bispecific antibody, zanidatamab can attach two non-overlapping HER2 epitopes at the same time, a process called biparatopic binding.

The companies signed licensing and partnership agreements in November 2018 under which BeiGene obtained an exclusive licence to research, develop and market zanidatamab and ZW49 in Asia, excluding Japan, Australia and New Zealand.

Furthermore, Zymeworks and BeiGene are partnering on joint worldwide development for specific indications to develop zanidatamab and ZW49 across various HER2-expressing malignancies and treatment options.

With the first subject dosing in Asia, BeiGene will make a milestone payment of $8m to Zymeworks.

The international, randomised Phase III trial will assess the efficacy and safety of zanidatamab plus physician’s choice chemotherapy with or without tislelizumab versus trastuzumab plus physician’s choice chemotherapy as first-line therapy.

It will enrol nearly 700 patients with advanced or metastatic human epidermal growth factor receptor 2 (HER2)-positive gastroesophageal cancers at approximately 300 study centres in 38 nations.

Progression-free survival as evaluated by blinded independent central review and overall survival will be the primary goals of the trial.

BeiGene will manage the study centres sites in Australia, New Zealand and Asia except for Japan while Zymeworks will handle sites in areas that include North and South America, Europe, Japan, Africa and the Middle East.

With an estimated enrolment period of two years, Zymeworks anticipates the filing of a supplemental Biologics Licence Application with the US Food and Drug Administration by 2024.

This October, Zymeworks and ALX Oncology dosed the first participant in the Phase Ib/II trial of Zanidatamab plus evorpacept in individuals with advanced HER2-expressing breast cancer and other solid tumours.