Zymeworks' lead product candidate, ZW25, is a novel bispecific (dual-targeting) antibody currently being evaluated in an adaptive Phase 1 clinical trial, targeting two distinct domains of the human epidermal growth factor receptor 2, or HER2, a protein that promotes the growth of cancer cells. This unique design enables ZW25 to address patient populations with all levels of HER2 expression, including those with low to intermediate HER2-expressing tumors, who are otherwise limited to chemotherapy or hormone therapy. Approximately 81% of patients with HER2-expressing breast cancer and 57% of patients with HER2-expressing gastric and gastroesophageal junction cancer have tumors that express low to intermediate levels of HER2, making them ineligible for treatment with currently-approved HER2-targeted therapies, such as blockbuster drugs Herceptin and Perjeta. In the Phase 1 clinical trial, ZW25 has demonstrated preliminary anti-tumor activity across multiple cancer types in patients who have progressed after several lines of treatment with HER2-targeted therapies. Zymeworks' second product candidate, ZW33, is a bispecific antibody-drug conjugate, or ADC, based on the same antibody framework as ZW25 but armed with a cytotoxic (potent cancer cell-killing) payload. ZW33 is designed to target several indications characterized by HER2 expression; Phase 1 clinical trials are expected in the 2H17. It also has a pipeline of preclinical candidates and programs in immuno-oncology and other therapeutic areas. In addition, two of the therapeutic platforms have revenue-generating partnerships with Merck, Lilly, Celgene, GSK and Daiichi.