Zymeworks Pulls Plug On Early-Stage Cancer Potential As Therapy Unlikely To Provide Benefit

Author: Vandana Singh | September 02, 2025 12:30pm

Zymeworks Inc. (NASDAQ:ZYME) on Tuesday decided to voluntarily discontinue clinical development of ZW171, a T-cell engager designed to target gynecological, thoracic, and digestive system cancers.

ZW171 is designed to address cancers driven by mesothelin, a well-recognized but historically challenging target.

The decision to discontinue clinical development of ZW171 was based on completion of the planned cohorts of the dose escalation portion of the Phase 1 trial of ZW171 in patients with ovarian cancer and non-small cell lung cancer.

Also Read: Cancer-Focused Zymeworks’ Q4 Earnings Miss Expectations, Reprioritize Resources To Focus On ZW251

After completing the planned dose escalation cohorts and establishing a maximum tolerated dose, Zymeworks determined that further dose evaluation in the current trial would unlikely support a benefit-risk profile consistent with the desired monotherapy target product profile.

While cytokine release syndrome was well-managed in the Phase 1 study, dose-limiting toxicities were consistent with mesothelin-related on-target off-tumor toxicity.

Ongoing participants in the Phase 1 trial will continue treatment at the discretion of their investigator, and participants who have discontinued treatment will continue safety follow-up as per the study protocol.

“We continue to advance our broader product pipeline, including the ongoing Phase 1 trial of ZW191 and the initiation of a Phase 1 study for ZW251 expected in 2025. We are also preparing an IND filing for ZW209, our DLL3-directed trispecific T cell engager, planned in the first half of 2026,” said Kenneth Galbraith, Chair and CEO of Zymeworks.

Price Action: ZYME stock is down 5% at $14.07 at the last check on Tuesday.

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