VANCOUVER, Canada I April 15, 2019 I Zymeworks Inc. (NYSE/TSX: ZYME), a clinical-stage biopharmaceutical company developing multifunctional therapeutics, today announced it has initiated its global multicenter Phase 2 clinical trial evaluating ZW25 in combination with standard of care chemotherapy for the first-line treatment of HER2-positive metastatic gastric, gastroesophageal junction, and esophageal adenocarcinomas.

“Advancing ZW25 into a Phase 2 clinical trial represents another key milestone for Zymeworks,” said Ali Tehrani, Ph.D., Zymeworks’ President & CEO. “This reaffirms our commitment to execute our ambitious drug development strategy to address unmet need in patients with HER2-expressing cancers across multiple indications and lines of therapy. We anticipate that data from this trial will support initiation of a first-line registrational trial, which could position ZW25 as the new standard of care for HER2-positive metastatic gastric cancer.”

In addition to the Phase 2 metastatic gastroesophageal cancer trial, ZW25 continues to be evaluated in multiple expansion cohorts in the ongoing Phase 1 trial as a single agent in gastrointestinal, gynecological, and other HER2-expressing cancers, and in combination with chemotherapy in breast and gastroesophageal cancers.

About the Trial

The Phase 2 trial is a two-part open-label study. The primary objectives of this trial are to confirm the safety, tolerability, and anti-tumor activity of ZW25 in combination with global standard of care regimens for gastroesophageal adenocarcinoma, including platinum and fluoropyrimidine-based regimens.

“While major advances have been made in the treatment of HER2-positive breast cancer, patients with HER2-positive gastroesophageal adenocarcinomas still have limited options,” said Diana Hausman, M.D., Chief Medical Officer of Zymeworks. “Based on the encouraging single agent anti-tumor activity we observed in patients with gastroesophageal adenocarcinomas in our Phase 1 study, we believe that ZW25 has the potential to address this need, and we are excited to be starting this first-line trial.”

About ZW25

ZW25 is being evaluated in Phase 1 and Phase 2 clinical trials across North America and South Korea. It is a bispecific antibody, based on Zymeworks’ Azymetric™ platform, that can simultaneously bind two non-overlapping epitopes of HER2, known as biparatopic binding. This unique design results in multiple mechanisms of action including dual HER2 signal blockade, increased binding and removal of HER2 protein from the cell surface, and potent effector function leading to encouraging anti-tumor activity in patients. Zymeworks is developing ZW25 as a HER2-targeted treatment option for patients with any solid tumor that expresses HER2. The FDA has granted Orphan Drug Designation to ZW25 for the treatment of both gastric and ovarian cancers.

About the Azymetric™ Platform

The Azymetric platform enables the transformation of monospecific antibodies into bispecific antibodies, giving the antibodies the ability to simultaneously bind two different targets. Azymetric bispecific technology enables the development of multifunctional biotherapeutics that can block multiple signaling pathways, recruit immune cells to tumors, enhance receptor clustering degradation, and increase tumor-specific targeting. These features are intended to enhance efficacy while reducing toxicities and the potential for drug-resistance. Azymetric bispecifics have been engineered to retain the desirable drug-like qualities of naturally occurring antibodies, including low immunogenicity, long half-life, and high stability. In addition, they are compatible with standard manufacturing processes with high yields and purity, potentially significantly reducing drug development costs and timelines.

About Zymeworks Inc.

Zymeworks is a clinical-stage biopharmaceutical company dedicated to the development of next-generation multifunctional biotherapeutics. The Company’s suite of therapeutic platforms and its fully integrated drug development engine enable precise engineering of highly differentiated product candidates. Zymeworks’ lead clinical candidate, ZW25, is a novel Azymetric™ bispecific antibody currently in Phase 2 clinical development. The Company’s second clinical candidate, ZW49, is a bispecific antibody-drug conjugate currently in Phase 1 clinical development and combines the unique design and antibody framework of ZW25 with Zymeworks’ proprietary ZymeLink™ cytotoxic payload. Zymeworks is also advancing a deep preclinical pipeline in immuno-oncology and other therapeutic areas. In addition, its therapeutic platforms are being leveraged through multiple strategic partnerships with eight global biopharmaceutical companies. For more information, visit www.zymeworks.com.

SOURCE: Zymeworks