Zymeworks Inc., a clinical-stage biotechnology company, has announced its decision to discontinue the clinical development of ZW171, a T cell engager designed to target cancers involving mesothelin, including gynecological, thoracic, and digestive system cancers. This decision follows the completion of the dose escalation portion of the Phase 1 trial in patients with ovarian cancer and non-small cell lung cancer. Despite promising preclinical activity, Zymeworks determined that further dose evaluation would likely not support the desired monotherapy target product profile due to dose-limiting toxicities related to mesothelin on-target off-tumor effects. The ongoing participants in the trial will continue their treatment under the guidance of their investigators, while those who have discontinued will undergo safety follow-up as per the study protocol. Zymeworks continues to advance its broader product pipeline, including ongoing trials for ZW191 and preparations for a new Phase 1 study for ZW251, expected in 2025, and an IND filing for ZW209 planned for the first half of 2026.