Zymeworks Stock Tanks Over 17% After Cancer Drug Candidate Update

Zymeworks Inc. (ZYME) on Tuesday announced its decision to discontinue clinical development of ZW171, designed to target certain cancers.

ZW171 is designed to address cancers driven by Mesothelin, a cell-surface protein overexpressed in certain cancers, including gynecological, thoracic, and digestive system cancers. The company was testing the drug in an early-stage trial in patients with ovarian cancer and non-small cell lung cancer.

At the time of writing, ZYME stock was down by over 17% in Tuesday’s pre-market session. On Stocktwits, retail sentiment around ZYME stock, however, rose from ‘neutral’ to ‘bullish’ territory over the past 24 hours, while message volume stayed at ‘low’ levels.

After establishing a maximum tolerated dose in the early-stage trial, the company determined that further dose escalation would be unlikely to support a benefit-risk profile consistent with the company’s intent to develop it as a standalone therapy.

While ongoing participants in the trial will continue treatment at the discretion of their investigator, participants who have discontinued treatment will continue safety follow-up as per the study protocol, Zymeworks said.

Zymeworks CEO Kenneth Galbraith said that the outcome is “disappointing” given the promising preclinical activity observed with ZW171.

“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,” he added. 

ZYME stock is up by 1% this year and nearly 29% over the past 12 months.

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