Zymeworks Inc. said data from its ongoing phase 1 study showed that its antibody ZW25 showed anti-tumor activity in heavily pretreated patients across a range of HER2-expressing cancers.
HER2 is a member of human epidermal growth factor receptor family and amplification or over-expression of this oncogene can play an important role in the development and progression of certain aggressive types of breast cancer.
The company said that, to date, a total of 50 patients have been enrolled in the study and data from 42 patients were available as of the data cut-off date of April 18.
In 33 evaluable patients, the drug reduced the size of the tumors in 36% of the patients. The disease remained stable in 18% of the patients and worsened in 45% of the patients. The company said 68% of all patients with measurable disease, or 21 out of 31, had a decrease in target lesions.
The company said that ZW25 was well tolerated at all dose levels and schedules and there were no dose-limiting toxicities.
Zymeworks plans to develop the drug as a standalone treatment for advanced HER2 high gastroesophageal cancer in patients who have received prior treatment with Roche Holding AG's Herceptin, or trastuzumab, as well as in other HER2 high cancers, such as colorectal, where a HER2-targeted agent has not yet been approved.
The company also plans to develop the drug in combination with chemotherapy in earlier lines of therapy for HER2 high gastroesophageal and breast cancers. Zymeworks may also develop the antibody in combination with other anti-cancer agents in patients with lower HER2-expressing cancers.
However, the company said its top priority is to focus on advanced gastroesophageal cancer, with a phase 2/3 study expected to start as soon as the second half of 2019 subject to discussion with the U.S. Food and Drug Administration.
Zymeworks plans to start new studies to evaluate combinations, other than those being tested in the ongoing phase 1 study, later in 2018.
The 2018 American Society of Clinical Oncology meeting is expected to bring together more than 32,000 professionals from all over the world, with more than 2,500 study abstracts to be presented on-site and an additional 3,350 abstracts to be published online.
