Zymeworks Inc. (ZYME) presented new Phase 1 data for its folate receptor alpha (FRa)-targeting antibody-drug conjugate (ADC), ZW191 at the AACR Annual Meeting 2026. The therapy demonstrated encouraging anti-tumor activity in heavily pretreated ovarian and endometrial cancers, with responses observed regardless of FRa expression levels.
Addressing Unmet Needs
Ovarian and endometrial cancer often recur after standard treatments, leaving patients with limited options. ZW191 is designed to target FRa, a protein found in majority of high-grade serous ovarian carcinomas and many endometrial cancers, delivering a novel payload directly into tumor cells.
Phase 1 Study Results
The ongoing global Phase 1 study (ZWI-ZW191-101) enrolled patients with advanced, drug-resistant tumors. In platinum-resistant ovarian cancer, ZW191 achieved a confirmed objective response rate (cORR) of 56% across all dose levels, with tumor regression in 68% of patients and disease control in 94%.
At doses of 6.4-9.6 mg/kg, responses were even stronger:
-Ovarian cancer: cORR of 61%, disease control in 100% of patients.
-Endometrial cancer: cORR of 57%, disease control in 86%.
Responses appeared early, with a median time to response of 1.4 months. Median duration of response was not reached at data cutoff, and median progression-free survival was 7.6 months across cohorts.Safety Profile
ZW191 was generally well tolerated up to 11.2 mg/kg. Severe (grade =3) treatment-emergent adverse events (TEAEs) occurred in 55% of patients, most commonly neutropenia, anemia and thrombocytopenia. Grade 4 events were rare, and one grade 5 events at the highest dose was deemed unrelated to treatment. Investigators noted the safety profile was manageable with no unexpected signals.
Next Steps
Part 2a of the study, focused on dose optimization in ovarian cancer, has completed enrolment across North America, Europe and Asia-Pacific. Results will guide the recommended dose for further registration studies.
ZW191's differentiated design- including a high drug-to antibody ratio and proprietary payload- supports its potential as best-in-class therapy for gynecological cancers and possibly other FRa- expressing tumors.
Company Snapshot
Zymeworks is advancing a diverse pipeline of antibody-based therapeutics, including ADCs and multispecific antibodies, alongside licensed assets such as Ziihera.
ZYME has traded between $10.86 and $28.49 over the past year. The stock closed Tuesday's trading at $28.27, up 1.51%. During overnight trading the stock is at $28.77, up 1.77%.
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