Zymeworks Announces Presentations for Ziihera® (zanidatamab-hrii) at 2026 AACR Annual Meeting

Four presentations deliver new insights into zanidatamab, including its differentiated HER2 biology

VANCOUVER, British Columbia, March 18, 2026 (GLOBE NEWSWIRE) -- Zymeworks Inc. (Nasdaq: ZYME), a biotechnology company managing a portfolio of licensed healthcare assets while developing a diverse pipeline of novel, multifunctional biotherapeutics, today announced that the company’s partner, Jazz Pharmaceuticals, will present four abstracts featuring data from clinical trials evaluating Ziihera® (zanidatamab-hrii) at the American Association for Cancer Research (AACR) Annual Meeting, being held April 17-22, 2026 in San Diego, CA.

“We are pleased to see the continued clinical progress of zanidatamab reflected in multiple presentations at AACR,” said Ken Galbraith, Chair, Chief Executive Officer, and Interim Chief Financial Officer of Zymeworks. “These studies highlight emerging data evaluating zanidatamab across tumor types beyond biliary tract cancer and gastroesophageal adenocarcinoma, and contribute to the growing body of evidence supporting its potential across HER2-expressing cancers.”

Highlights at the AACR Annual Meeting include:

• An oral presentation with results from the Phase 2 single-arm, open-label NeoZanHER trial (NCT05035836) evaluating zanidatamab for the investigational use as neoadjuvant monotherapy in patients with early-stage HER2+ breast cancer. At six weeks, zanidatamab treatment resulted in a statistically significant decrease in tumor size and volume from baseline, and 30% of patients (n=6) achieved pathologic complete response (pCR). Treatment with zanidatamab was manageable with no new safety signals.
• A poster presentation detailing mechanistic and multi-omics analyses characterizing zanidatamab’s differentiated HER2 biology, including dual, domain-specific binding and downstream effects on key cellular signaling pathways, with insights into activity in models following progression on trastuzumab deruxtecan (T-DXd).

Additional presentations further explore zanidatamab’s utility across HER2-expressing solid tumors and within innovative biomarker-driven clinical trial designs, including adaptive organ-preservation strategies in gastroesophageal adenocarcinoma.

Oral Presentation

Title: A Phase 2 Single-Arm Open-Label Trial Evaluating Zanidatamab in Patients with Early Stage HER2 positive Breast Cancer: The NeoZanHER Study
Presentation Number: CT012
Session: Clinical Trials Minisymposium: Aiming for Cure: Perioperative Clinical Trials
Date/Time: Saturday, April 18, 2026 at 12:30 – 2:30 pm Pacific Standard Time (PST)

Poster Presentations

Title: Zanidatamab Modulates Multiple Pathways Involved in Tumor Growth and Survival is Efficacious Post-T-DXd
Abstract: 452
Session: Experimental and Molecular Therapeutics: Next-Generation Targeted Therapies Directed Against Tumor Surface Antigens
Date/Time: Tuesday, April 21, 2026 at 9:00 am – 12:00 pm PST

Title: DiscovHER PAN-206: Phase 2 Tumor-Agnostic Study of Zanidatamab in Patients With Previously Treated Human Epidermal Growth Factor Receptor 2–Overexpressing Solid Tumors
Abstract: CT209
Session: Phase II and Phase III Clinical Trials in Progress
Date/Time: Tuesday, April 21, 2026 at 9:00 am – 12:00 pm PST

Title: AACR Adaptive Biomarker-Driven Organ Preservation Trial in GE Adenocarcinomas (AACR-ADOPT-GEA)
Abstract: CT223
Session: Phase II and Phase III Clinical Trials in Progress
Date/Time: Tuesday, April 21, 2026 at 9:00 am – 12:00 pm PST

The AACR abstracts are available at https://www.abstractsonline.com/pp8/#!/21436.

About Ziihera® (zanidatamab-hrii)

Ziihera (zanidatamab-hrii) is a bispecific HER2-directed antibody that binds to two extracellular sites on HER2. Binding of zanidatamab-hrii with HER2 results in internalization leading to a reduction in HER2 expression of the receptor on the tumor cell surface. Zanidatamab-hrii induces complement-dependent cytotoxicity (CDC), antibody-dependent cellular cytotoxicity (ADCC), and antibody-dependent cellular phagocytosis (ADCP). These mechanisms result in tumor growth inhibition and cell death in vitro and in vivo. In the United States, Ziihera is indicated for the treatment of adults with previously treated, unresectable or metastatic HER2-positive (IHC 3+) biliary tract cancer (BTC), as detected by an FDA-approved test.¹ The FDA granted accelerated approval for this indication based on overall response rate and duration of response. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).¹

Zanidatamab is being developed in multiple clinical trials as a targeted treatment option for patients with solid tumors that express HER2. Zanidatamab is being developed by Jazz and BeOne under license agreements from Zymeworks, which first developed the molecule.

The FDA granted two Breakthrough Therapy designations for zanidatamab's development: one as a single agent for previously treated HER2 gene-amplified BTC, and one in combination with standard-of-care chemotherapy for first-line HER2+ locally advanced or metastatic GEA. The FDA also granted two Fast Track designations for zanidatamab: one as a single agent for refractory BTC and one in combination with standard-of-care chemotherapy for first-line GEA. Additionally, zanidatamab has received Orphan Drug designations from the FDA for the treatment of BTC, gastric (including gastroesophageal junction) cancer, and esophageal cancer, as well as Orphan Drug designations from the European Medicines Agency for the treatment of BTC, gastric/gastroesophageal junction cancer and oesophageal cancer.

The full U.S. Prescribing Information for Ziihera, including BOXED Warning, is available at: https://pp.jazzpharma.com/pi/ziihera.en.USPI.pdf

About Zymeworks Inc.

Zymeworks is a global biotechnology company managing a portfolio of licensed healthcare assets and 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. Zymeworks’ asset and royalty aggregation strategy focuses on optimizing positive future cash flows from an emerging portfolio of licensed products such as Ziihera® (zanidatamab-hrii) and other licensed products and product candidates, such as pasritamig. In addition, Zymeworks is also building a portfolio of healthcare assets that can generate strong cash flows, while supporting the development of innovative medicines. Zymeworks engineered and developed Ziihera, a HER2-targeted bispecific antibody using the Company’s proprietary Azymetric™ technology and 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. Zymeworks is rapidly advancing a robust pipeline of product candidates, leveraging its expertise in both antibody drug conjugates and multispecific antibody therapeutics targeting novel pathways in areas of significant unmet medical need. Zymeworks’ complementary therapeutic platforms and fully integrated drug development engine provide the flexibility and compatibility to precisely engineer and develop highly differentiated antibody-based therapeutics. These capabilities 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’ implementation of its long-term strategy to maximize value creation; the potential of zanidatamab as a treatment of HER2-expressing cancers; anticipated data presentations; potential safety profile and therapeutic effects of zanidatamab; the commercial potential of technology platforms and product candidates; preclinical and clinical development of product candidates; and other information that is not historical information. When used herein, words such as “plan”, “believe”, “expect”, “may”, “continue”, “anticipate”, “potential”, “will”, “on track”, “progress”, “preserve”, “intend”, “could”, 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: 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; Zymeworks may not achieve milestones or receive additional payments under its collaborations; regulatory agencies may impose additional requirements or delay the initiation of clinical trials; the impact of new or changing laws and regulations; potential negative impacts of FDA regulatory delays and uncertainty around recent policy developments, 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; zanidatamab may not be successfully commercialized; Zymeworks’ business strategy related to anticipated and potential future milestones and royalty streams and existing and potential new partnerships may not be successfully implemented; Zymeworks’ evolution of its business strategy may not deliver meaningful shareholder returns; ongoing and future clinical trials may not demonstrate safety and efficacy of any of Zymeworks’ or its collaborators’ product candidates; data providing early validation of our antibody drug conjugate platform and next generation pipeline programs may not be replicated in future studies; 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.

Contacts:

Investor Inquiries:
Shrinal Inamdar
Vice President, Investor Relations
(604) 678-1388
ir@zymeworks.com

Media Inquiries:
Diana Papove
Vice President, Corporate Communications
(604) 678-1388
media@zymeworks.com

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¹ ZIIHERA (zanidatamab-hrii) Prescribing Information. Palo Alto, CA: Jazz Pharmaceuticals, Inc.