Zymeworks Announces Agreement with Pfizer and Initiation of a New Phase 2 Trial Evaluating ZW25 in Combination with Ibrance® (palbociclib)

Monday, January 13, 2020

Zymeworks Inc., a clinical-stage biopharmaceutical company developing multifunctional therapeutics, today announced the initiation of a Phase 2 trial evaluating ZW25 combination therapy and an agreement with Pfizer which advances the study. Zymeworks’ HER2-targeted bispecific antibody ZW25 is being evaluated in combination with Pfizer’s Ibrance® (palbociclib), an oral CDK4/6 inhibitor, and the hormone therapy fulvestrant in patients with previously-treated locally advanced and/or metastatic HER2-positive, HR-positive breast cancer. Zymeworks will sponsor the study, and Pfizer will provide palbociclib.

“The initiation of this Phase 2 trial and collaboration with Pfizer mark significant milestones in our progress towards establishing ZW25 as the foundational HER2 therapy in multiple regimens across breast and other cancers,” said Diana Hausman, M.D., Chief Medical Officer at Zymeworks. “Together, ZW25 and palbociclib have the potential to improve anti-tumor activity and minimize side effects for people living with advanced HER2‑positive, HR-positive breast cancer.”

This Phase 2 clinical trial is a multicenter, open-label, two-part study (clinicaltrials.gov: NCT04224272). Part one of the study will evaluate the safety and tolerability of ZW25 in combination with palbociclib and fulvestrant and identify the recommended doses (RD) of ZW25 and palbociclib. Part two of the study will evaluate anti-tumor activity at the RD level. The trial will enroll up to 76 patients at sites in the United States and Canada, and expansion to Spain is planned.

ZW25 is being evaluated within a broad clinical development program in multiple HER2‑expressing cancers, including biliary tract, gastroesophageal adenocarcinoma (GEA), breast, colorectal, and gynecologic cancers. In an ongoing Phase 1 clinical trial, Zymeworks is evaluating ZW25 as a single agent and in combination with chemotherapy as potential treatments for patients with HER2-expressing cancers (clinicaltrials.gov: NCT02892123). For patients with HER2-positive GEA, ZW25 is being studied in a Phase 2 trial as a first-line treatment in combination with standard of care chemotherapy (clinicaltrials.gov: NCT03929666). Zymeworks plans to initiate a registration-enabling Phase 2 trial in previously-treated or recurrent HER2-positive biliary tract cancer in 2020.