Zymeworks Presents New Phase 1 Data for ZW191, a Folate Receptor Alpha-Targeting ADC at AACR Annual Meeting 2026
Rhea-AI Summary
Zymeworks (Nasdaq: ZYME) on April 21, 2026 presented Phase 1 dose-escalation data for ZW191, an FRα-targeting ADC showing strong anti-tumor activity and manageable safety in heavily pretreated ovarian and endometrial cancers.
Key data: confirmed ORR up to 61% at 6.4–9.6 mg/kg, median progression-free survival 7.6 months, duration of response not reached, and tolerability to 11.2 mg/kg.
AI-generated analysis. Not financial advice.
Positive
- cORR 61% in 6.4–9.6 mg/kg ovarian cohort
- Median PFS 7.6 months across ovarian and endometrial cohorts
- Duration of response not reached at data cutoff
- Tolerated up to 11.2 mg/kg with manageable safety
Negative
- Grade ≥3 TEAEs in 55% of patients
- 24% neutropenia, 20% anemia, 12% thrombocytopenia
- 20% discontinued due to adverse events
- One on-study grade 5 event at highest dose (not treatment-related)
News Market Reaction – ZYME
On the day this news was published, ZYME gained 0.19%, reflecting a mild positive market reaction.
Data tracked by StockTitan Argus on the day of publication.
Key Figures
Market Reality Check
Peers on Argus
ZYME was up 0.18% while key peers were mixed: RCUS up 13.31%, DNTH, PGEN, and NTLA down modestly, and TRML flat. This points to stock-specific dynamics rather than a broad biotech move.
Previous Clinical trial Reports
| Date | Event | Sentiment | Move | Catalyst |
|---|---|---|---|---|
| Mar 30 | Fast Track designation | Positive | +0.1% | FDA Fast Track status granted for ZW191 in platinum‑resistant ovarian cancer. |
| Nov 17 | Phase 3 results | Positive | +29.1% | Positive Phase 3 HERIZON-GEA-01 data for Ziihera plus chemotherapy in HER2+ GEA. |
| Oct 23 | Initial Phase 1 data | Positive | -1.5% | Preliminary Phase 1 efficacy and safety data for ZW191 presented at AACR-NCI-EORTC. |
| Sep 02 | Program discontinuation | Negative | -5.4% | Clinical development of ZW171 discontinued after Phase 1 due to dose-limiting toxicities. |
| May 19 | Preclinical data | Positive | +5.2% | Preclinical efficacy and PK data for respiratory candidate ZW1528 presented at conference. |
Clinical and regulatory wins for pipeline assets, including ZW191 and Ziihera, have often coincided with positive single-day moves, though occasional negative reactions to favorable data also appear.
Over the past year, Zymeworks has reported multiple clinical milestones. For ZW191, initial Phase 1 data on Oct 23, 2025 showed encouraging activity, followed by a U.S. FDA Fast Track designation on Mar 30, 2026. Separately, positive Phase 3 results for Ziihera were announced on Nov 17, 2025, and preclinical data for ZW1528 were shared on May 19, 2025. The ZW171 program was discontinued on Sep 2, 2025. Today’s Phase 1 update for ZW191 builds on this ZW191-focused clinical and regulatory trajectory.
Historical Comparison
Clinical-trial headlines for Zymeworks have produced an average one-day move of 5.49%, with reactions ranging from modest to very strong, indicating that trial readouts can be meaningful trading catalysts.
For ZW191, the timeline shows initial Phase 1 data in Oct 2025, followed by U.S. FDA Fast Track designation in Mar 2026, and now updated Phase 1 results with dose escalation and optimization. In parallel, Ziihera advanced with positive Phase 3 data, while other assets like ZW1528 progressed preclinically and ZW171 was discontinued, illustrating active portfolio pruning and advancement.
Market Pulse Summary
This announcement provides expanded Phase 1 data for ZW191, showing a cORR of 61% in platinum‑resistant ovarian cancer at 6.4–9.6 mg/kg and median PFS of 7.6 months across ovarian and endometrial cohorts. These results build on earlier ZW191 data and the recent Fast Track designation. Investors may watch how efficacy at the selected dose, the reported 55% rate of grade ≥3 adverse events, and future registration-enabling decisions fit into Zymeworks’ broader clinical strategy.
Key Terms
folate receptor alpha medical
frα medical
antibody-drug conjugate medical
adc medical
objective response rate medical
progression-free survival medical
treatment-emergent adverse events medical
teaes medical
AI-generated analysis. Not financial advice.
- ZW191 demonstrates encouraging anti-tumor activity in heavily pretreated ovarian and endometrial cancers, regardless of FRα expression
- Confirmed objective response rate (cORR) of
61% at doses 6.4-9.6 mg/kg in platinum resistant ovarian cancer - Median duration of response was not reached at the time of data cutoff, and median progression-free survival was 7.6 months in ovarian and endometrial cancer cohorts
- Favorable tolerability profile and broad therapeutic window support continued clinical development
VANCOUVER, British Columbia, April 21, 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 results from the dose-escalation part of the Phase 1 study for ZW191, a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), at the 2026 American Association for Cancer Research (AACR) Annual Meeting.
The data from Part 1 of the ongoing global Phase 1 study (ZWI-ZW191-101), highlight a compelling combination of anti-tumor activity and manageable safety in patients with advanced, heavily pretreated solid tumors, including ovarian and endometrial cancers.
“We are highly encouraged by the initial clinical data for ZW191, which reinforce the strength of our ADC platform and its ability to generate differentiated therapeutics,” said Sabeen Mekan, M.D., Senior Vice President and Chief Medical Officer at Zymeworks. “The breadth and durability of responses, along with activity across varying levels of FRα expression, support further development of ZW191 as a potential best-in-class agent for patients with ovarian and endometrial cancers.”
Part 2a, the dose-optimization portion of the study evaluating patients with ovarian cancer at doses of 6.4 mg/kg and 9.6 mg/kg, has completed enrollment, with participants recruited globally across North America, Europe, and Asia-Pacific. The data from Part 2a will determine the recommended dose for any future registration studies.
Key Findings
In platinum resistant ovarian cancer patients, ZW191 demonstrated a cORR of
In endometrial cancer, ZW191 showed a cORR of
Across ovarian and endometrial cancer cohorts, responses were observed early, with a median time to response of 1.4 months. Median duration of response was not reached at the time of data cutoff, and median progression-free survival was 7.6 months.
ZW191 was well tolerated and safely administered up to 11.2 mg/kg. Severe (grade ≥3) treatment-emergent adverse events (TEAEs) occurred in
“These data demonstrate the potential of ZW191 to deliver meaningful clinical benefit in patients with heavily pre-treated gynecological tumors with limited options,” said Patricia LoRusso, DO, PhD (hc), FAACR and lead author. “The combination of encouraging response rates and manageable safety profile supports further development of this therapy, particularly in ovarian and endometrial cancers where new treatment options are urgently needed.”
ZW191’s differentiated profile, including a high drug-to-antibody ratio and novel payload, support its potential to address key limitations of current therapies and expand the reach of FRα-targeted treatment approaches across multiple tumor types.
About ZW191
ZW191 is an antibody-drug conjugate engineered to target a protein called folate receptor-⍺ found in ~
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 Zymeworks’ 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 the potential safety profile and therapeutic effects of Zymeworks’ product candidates; Zymeworks’ development of product candidates; status of studies and the related data; anticipated clinical data presentations; Zymeworks’ implementation of its long-term strategy; 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 or royalties 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; market conditions, including the impact of tariffs; 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 global and regional geopolitical or public health developments 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; Zymeworks may be unsuccessful in actively managing and/or aggregating revenue generating assets alongside its active R&D operations; 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; Zymeworks’ assumptions and estimates regarding its financial condition, future financial performance and estimated cash runway may be incorrect; 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
---
1 Köbel, M., Madore, J., Ramus, S. et al., Br J Cancer 111, 2297–2307 (2014).
2 May B, Conway N, Truong T, Linhart S, et al. FRα, B7-H4, & HER2 Expression in Endometrial Cancer: Assessing the Promise of Antibody Drug Conjugate Therapies. Presented at: SGO 2025 Winter Meeting; January 30 - February 1, 2025; Whistler, British Columbia, Canada.
3 Senol S, Ceyran AB, Aydin A, Zemheri E, Ozkanli S, Kösemetin D, Sehitoglu I, Akalin I. Folate receptor α expression and significance in endometrioid endometrium carcinoma and endometrial hyperplasia. Int J Clin Exp Pathol. 2015 May 1;8(5):5633-41.
4 O'Shannessy DJ, et al., Oncotarget. 2012 Apr; 3(4):414-25.
