Zymeworks to Present Clinical Data from the Phase 1 trial of ZW191, an Antibody-Drug Conjugate Targeting Folate Receptor-⍺, at AACR-NCI-EORTC International Conference

• Preliminary data presented at the AACR-NCI-EORTC conference will provide insights into the potential of ZW191 in patients with advanced solid tumors, including ovarian cancer, endometrial cancer, and non-small cell lung cancer.
• Data from the Phase 1 trial of ZW191 provide readthrough to Zymeworks'broader ADC portfolio utilizing its novel bystander active topoisomerase-1 inhibitor payload, ZD06519.

VANCOUVER, British Columbia, Oct. 13, 2025 (GLOBE NEWSWIRE) -- Zymeworks Inc. (Nasdaq: ZYME), a clinical-stage biotechnology company developing a diverse pipeline of novel, multifunctional biotherapeutics to improve the standard of care for difficult-to-treat diseases, including cancer, inflammation, and autoimmune disease, today announced the acceptance of a poster presentation discussing preliminary results from a Phase 1 study evaluating ZW191, an antibody-drug conjugate (ADC) targeting folate receptor-⍺ (FR⍺), at the AACR-NCI-EORTC Conference on Molecular Targets and Cancer Therapeutics, being held October 22-26, 2025, in Boston, MA.

“We are excited to share early clinical data from Part 1 of our first-in-human, Phase 1 trial of ZW191 in patients with advanced solid tumors,” said Sabeen Mekan, MD, Senior Vice President of Clinical Development of Zymeworks. “These initial results reinforce our confidence in our novel ADC design and its potential to deliver improved treatments for broader patient populations. ZW191 is the lead product candidate from our broad ADC portfolio utilizing our proprietary payload, ZD06519, and targets FRα, a protein expressed in several difficult-to-treat cancers, underscoring our commitment to developing differentiated therapies for patients who urgently need better treatment options.”

Presentation Details

Title: Preliminary results from a phase 1 first-in-human multicenter open-label study of ZW191, a folate receptor α-targeting antibody-drug conjugate, in patients with advanced solid tumors
Session: Poster Session A
Date/Time: Thursday, October 23, 2025 at 12:30-4:00 pm Eastern Time (ET)

Investor & Analyst Call

A live webcast will be held with lead author Patricia LoRusso, DO, PhD (hc), FAACR and Zymeworks senior management on October 23, 2025 at 3:30 pm ET to discuss the data presented. Dial-in details and webcast replay are available on Zymeworks'website at https://ir.zymeworks.com/events-and-presentations.

About ZW191
ZW191 is an ADC engineered to target a protein called folate receptor-⍺ found in ~75% of high-grade serous ovarian carcinomas1 and ~70% of lung adenocarcinomas2. ZW191’s differentiated design strongly supports its ability to internalize into FR⍺-expressing cells with the potential to release bystander active topoisomerase-1 inhibitor (ZD06519), a novel proprietary payload developed by Zymeworks to kill tumor cells.

About Zymeworks Inc.
Zymeworks is a global clinical-stage biotechnology company committed to the discovery, development, and commercialization of novel, multifunctional biotherapeutics. Zymeworks'mission is to make a meaningful difference in the lives of people impacted by difficult-to-treat conditions such as cancer, inflammation, and autoimmune disease. The Company’s complementary therapeutic platforms and fully integrated drug development engine provide the flexibility and compatibility to precisely engineer and develop highly differentiated antibody-based therapeutic candidates. Zymeworks engineered and developed zanidatamab, a HER2-targeted bispecific antibody using the Company’s proprietary Azymetric™ technology. Zymeworks has entered into separate agreements with BeOne Medicines Ltd. (formerly BeiGene, Ltd.) and Jazz Pharmaceuticals Ireland Limited, granting each exclusive rights to develop and commercialize zanidatamab in different territories. Zanidatamab has received accelerated approval from the U.S. FDA, conditional approval from the NMPA in China, and conditional marketing authorization from the European Commission for the treatment of adults with previously treated, unresectable or metastatic HER2-positive (IHC 3+) biliary tract cancer. It is the first and only dual HER2-targeted bispecific antibody approved for this indication in the U.S., Europe, and China. Zanidatamab is also being evaluated in multiple global clinical trials as a potential best-in-class treatment for patients with multiple HER2-expressing cancers. Zymeworks is rapidly advancing a robust pipeline of wholly-owned product candidates, leveraging its expertise in both antibody drug conjugates and multispecific antibody therapeutics targeting novel pathways in areas of significant unmet medical need. A Phase 1 study for ZW191 is actively recruiting and ZW251 is expected to enter clinical trials in 2025. In addition to Zymeworks'pipeline, its therapeutic platforms have been further leveraged through strategic partnerships with global biopharmaceutical companies. For information about Zymeworks, visit www.zymeworks.com and follow @ZymeworksInc on X.

Cautionary Note Regarding Forward-Looking Statements
This press release includes “forward-looking statements” or information within the meaning of the applicable securities legislation, including Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements in this press release include, but are not limited to, statements that relate to Zymeworks'data presentations and key findings; the timing and status of ongoing and future studies and the release of data; the potential therapeutic effects of and commercial potential of Zymeworks'product candidates; Zymeworks'preclinical pipeline; the ability to advance product candidates into later stages of development; and other information that is not historical information. When used herein, words such as “plan”, “believe”, “expect”, “may”, “anticipate”, “potential”, “will”, “on track”, “continue”, “progress” and similar expressions are intended to identify forward-looking statements. In addition, any statements or information that refer to expectations, beliefs, plans, projections, objectives, performance or other characterizations of future events or circumstances, including any underlying assumptions, are forward-looking. All forward-looking statements are based upon Zymeworks'current expectations and various assumptions. Zymeworks believes there is a reasonable basis for its expectations and beliefs, but they are inherently uncertain. Zymeworks may not realize its expectations, and its beliefs may not prove correct. Actual results could differ materially from those described or implied by such forward-looking statements as a result of various factors, including, without limitation: clinical trials may not demonstrate safety and efficacy of any of Zymeworks'or its collaborators'product candidates; any of Zymeworks'or its partners'product candidates may fail in development, may not receive required regulatory approvals, or may be delayed to a point where they are not commercially viable; regulatory agencies may impose additional requirements or delay the initiation of clinical trials; the impact of new or changing laws and regulations; market conditions, including the impact of tariffs; potential negative impacts of FDA regulatory delays and uncertainty and new policies implemented under the current administration, including executive orders, changes in the leadership of federal agencies such as the FDA, staff layoffs, budget cuts to agency programs and research, and changes in drug pricing controls; the impact of pandemics and other health crises on Zymeworks'business, research and clinical development plans and timelines and results of operations, including impact on its clinical trial sites, collaborators, and contractors who act for or on Zymeworks'behalf; clinical trials and any future clinical trials may not demonstrate safety and efficacy of any of Zymeworks'or its collaborators'product candidates; inability to maintain or enter into new partnerships or strategic collaborations; and the factors described under “Risk Factors” in Zymeworks'quarterly and annual reports filed with the Securities and Exchange Commission (copies of which may be obtained at www.sec.gov and www.sedarplus.ca).

Although Zymeworks believes that such forward-looking statements are reasonable, there can be no assurance they will prove to be correct. Investors should not place undue reliance on forward-looking statements. The above assumptions, risks and uncertainties are not exhaustive. Forward-looking statements are made as of the date hereof and, except as may be required by law, Zymeworks undertakes no obligation to update, republish, or revise any forward-looking statements to reflect new information, future events or circumstances, or to reflect the occurrences of unanticipated events.

Investor inquiries:
Shrinal Inamdar
Senior Director, Investor Relations
(604) 678-1388
ir@zymeworks.com

Media inquiries:
Diana Papove
Senior Director, Corporate Communications
(604) 678-1388
media@zymeworks.com

1 Köbel, M., Madore, J., Ramus, S. et al., Br J Cancer 111, 2297–2307 (2014).
2 O'Shannessy DJ, et al., Oncotarget. 2012 Apr; 3(4):414-25.