Zymeworks Halts Development of ZW171 T-cell Engager After Phase 1 Trial Assesses Benefit-Risk Profile

Zymeworks has discontinued clinical development of ZW171, a mesothelin-directed T-cell engager, after completing Phase 1 dose escalation cohorts in ovarian cancer and non-small cell lung cancer patients123.

The company determined that further dose evaluation would be unlikely to achieve a benefit-risk profile consistent with their monotherapy target product profile13.

Dose-limiting toxicities related to mesothelin-targeted effects were observed, though cytokine release syndrome was well-managed in the trial13.

Ongoing trial participants may continue treatment at their investigator's discretion; those discontinuing will be followed for safety as per protocol13.

Discontinuation of ZW171 is part of Zymeworks's ongoing portfolio management, and the company continues to advance other candidates such as ZW191 (Phase 1), ZW251 (Phase 1 planned for 2025), and ZW209 (IND filing planned for early 2026)34.

Sources:

1. https://www.thepharmaletter.com/biotechnology/zymeworks-drops-development-of-zw171-a-mesothelin-directed-t-cell-engager

2. https://www.stocktitan.net/news/ZYME/

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

4. https://www.globenewswire.com/news-release/2025/03/25/3049195/0/en/Zymeworks-to-Present-Preclinical-Data-on-T-cell-Engager-and-Antibody-Drug-Conjugate-Platforms-in-Six-Posters-at-AACR-Annual-Meeting.html