Zymeworks to Discontinue ZW171 Clinical Development

Zymeworks has discontinued clinical development of ZW171, a product candidate for cancer treatment. The company has a pipeline of four preclinical candidates, including ZW191, ZW220, and ZW251, and is engaged in the discovery, development, and commercialization of multifunctional biotherapeutics to treat cancer and other serious diseases. Zymeworks' platforms include Azymetric, Drug Conjugate Platforms, EFECT, and ProTECT.

VANCOUVER, British Columbia, Sept. 02, 2025 — Zymeworks Inc. (Nasdaq: ZYME) has announced the discontinuation of clinical development for ZW171, a T cell engager targeting mesothelin-driven cancers. The decision follows the completion of Phase 1 trial dose escalation cohorts in ovarian cancer and non-small cell lung cancer patients. While cytokine release syndrome was manageable, the trial revealed dose-limiting toxicities related to mesothelin-targeted effects [1].

Zymeworks determined that further dose evaluation would not support a favorable benefit-risk profile. The company is redirecting resources to more promising candidates, including ZW191 (currently in Phase 1), ZW251 (planned Phase 1 study in 2025), and ZW209 (IND filing planned for early 2026) [1].

The termination of ZW171 represents a significant setback in Zymeworks' oncology pipeline. The mesothelin-targeting T cell engager was being evaluated for gynecological, thoracic, and digestive system cancers, all areas with substantial unmet needs. The critical issue identified was an unfavorable benefit-risk profile due to dose-limiting toxicities consistent with mesothelin-related on-target off-tumor effects [1].

Zymeworks continues to advance its pipeline, leveraging its expertise in antibody drug conjugates and multispecific antibody therapeutics targeting novel pathways in areas of significant unmet medical need. The company's platforms include Azymetric, Drug Conjugate Platforms, EFECT, and ProTECT [1].

References:
[1] https://www.stocktitan.net/news/ZYME/zymeworks-announces-decision-to-discontinue-clinical-development-of-qezs3habk5i6.html