Zymeworks Inc. announced that the Company has begun enrolling patients into the expansion cohort portion of the ongoing Phase 1 clinical trial for ZW49, its novel HER2-targeted antibody-drug conjugate (ADC). The dose escalation portion of the study employed a standard 3 + 3 design to evaluate escalating doses within different dosing regimens including once every two week (Q2W) and once every three week (Q3W) schedules with the objective of selecting a dose and schedule to advance into the expansion cohorts. To date patients from sites across the US and Canada with a variety of heavily pretreated HER2 `positive cancer types have been enrolled, including breast cancer, gastroesophageal adenocarcinoma, gynecologic cancers, non-small cell lung cancer, anal cancer, and colorectal cancer. In the 35 patients who have received ZW49 across all dosing regimens, there have been no dose limiting toxicities, no treatment-related hematologic toxicities including neutropenia or thrombocytopenia, no treatment-related pulmonary toxicity including interstitial lung disease or pneumonitis, and no treatment-related liver toxicity. There have been no treatment-related deaths.