FDA Grants Fast Track Status to ZW191 for Platinum-Resistant Ovarian Cancer

The FDA has granted Fast Track designation to ZW191, an investigational antibody-drug conjugate (ADC) targeting folate receptor-alpha (FRα), as a potential treatment for patients with advanced or metastatic platinum-resistant ovarian cancer (PROC).

A Differentiated Mechanism: Targeting the Folate Receptor

FRα is a glycosylphosphatidylinositol-anchored glycoprotein that is overexpressed in several solid tumors but has limited expression in normal tissues. Expression is particularly high in:

• High-grade serous ovarian carcinomas: Approximately 75% of cases.¹
• Endometrial cancers: Over 50% of cases.^2,3
• Lung adenocarcinomas: Approximately 70% of cases.⁴

ZW191 is engineered with a proprietary topoisomerase-1 inhibitor payload ZD06519, but it also has “bystander active" potential, which in turn may address the challenge of intratumoral heterogeneity.

Clinical Implications: Moving Beyond Biomarker Selection

FDA’s decision is that the Fast Track designation was granted irrespective of FRα expression levels.

“The designation was granted irrespective of FRα expression, highlighting ZW191’s potential of extending treatment benefits to a broad group of patients without need for biomarker selection,” Sabeen Mekan, MD, senior vice president and chief medical officer at Zymeworks, the developer of ZW191, stated in a press release.

From a nursing perspective, this suggests a future where the administrative burden of waiting for immunohistochemistry (IHC) confirmation of high FRα expression—currently a requirement for other agents in this class—could be mitigated, allowing for more rapid initiation of therapy in the platinum-resistant setting.

Safety and Trial Status

ZW191 is currently being evaluated in a phase 1 open-label study (NCT06555744), which is enrolling patients with advanced solid tumors to determine:

• Safety and Tolerability: Establishing the maximum-tolerated dose and identifying dose-limiting toxicities.
• Pharmacokinetics: Understanding how the drug is absorbed, distributed, and excreted.
• Preliminary Antitumor Activity: Assessing objective response rates and disease control.

As with other topoisomerase-1 inhibitor-based ADCs, oncology nurses should remain vigilant for class-specific toxicities during the trial phase, which often include gastrointestinal events and hematologic suppressions.

The Fast Track program is intended to expedite the development and review of drugs for serious conditions, therefore allowing for more frequent communication between the FDA and the drug manufacturer, as well as eligibility for Priority Review designation and Rolling Review submission if relevant criteria are met.

References

1. Zymeworks Inc. Zymeworks Receives U.S. FDA Fast Track Designation for ZW191. News release. March 30, 2026. Accessed March 30, 2026.
2. Cheung A, Bax HJ, Josephs DH, et al. Folate receptor alpha-targeted therapies in ovarian cancer. Oncotarget. 2018;9(43):27045-27068.
3. Necela BM, Cannon AN, Asmann YW, et al. Folate receptor-alpha (FRA) expression in endometrial cancer. PLoS One. 2015;10(3):e0120158.
4. Christoph DC, Kasper S, Gauler TC, et al. Folate receptor alpha expression in lung cancer. J Thorac Oncol. 2013;8(4):452-463.