LEXINGTON, Mass., October 23, 2025– Partner Therapeutics, Inc. (PTx), a fully integrated biotechnology company, announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy Designation (BTD) to zenocutuzumab-zbco (BIZENGRI®) for the treatment of adults with advanced unresectable or metastatic cholangiocarcinoma harboring a neuregulin-1 (NRG1) gene fusion. The designation was supported by new data from the Phase 2 eNRGy trial, which demonstrated a 37% overall response rate (ORR) and a median duration of response of 7.4 months. The data will be featured as both oral and poster presentations at the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics in Boston, Massachusetts, and will serve as the basis for a supplemental Biologics License Application (sBLA) planned for 2026.
Science Significance
Zenocutuzumab-zbco represents a major advance in precision oncology, targeting a rare but actionable genomic alteration—NRG1 fusions—that drive tumor growth across multiple solid cancers. Unlike conventional receptor-targeted therapies, NRG1 fusions form chimeric ligands that aberrantly activate the HER2/HER3 signaling pathway. Zenocutuzumab-zbco is a bispecific antibody designed to block HER2/HER3 dimerization and interrupt NRG1-driven oncogenic signaling. In the ongoing eNRGy trial, 19 evaluable patients with advanced NRG1+ cholangiocarcinoma achieved a 37% investigator-assessed ORR, a median time to response of 1.9 months, and median progression-free survival of 9.2 months. The clinical benefit rate was 58%, with most adverse events being grade 1 or 2. Dr. Alison M. Schram of Memorial Sloan Kettering Cancer Center stated, “NRG1 fusions are rare but actionable drivers in cholangiocarcinoma. The data from the eNRGy trial continue to highlight the potential of zenocutuzumab to offer meaningful clinical benefit for these patients.”
Regulatory Significance
Breakthrough Therapy Designation is among the FDA’s most valuable regulatory pathways, reserved for investigational therapies that may demonstrate substantial improvement over existing standards of care for serious or life-threatening conditions. The designation provides access to frequent FDA guidance, rolling review, and priority review eligibility, accelerating the potential timeline to approval. The BTD for zenocutuzumab-zbco follows its accelerated approval in December 2024 for adults with NRG1+ non-small cell lung cancer (NSCLC) and pancreatic adenocarcinoma who experienced disease progression after prior therapy. Together, these milestones solidify zenocutuzumab-zbco as the first and only FDA-approved therapy directly targeting NRG1 fusions.
Business Significance
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The designation further enhances Partner Therapeutics’ strategic and commercial position within precision oncology. The company holds exclusive U.S. rights to develop, manufacture, and commercialize zenocutuzumab-zbco under a license agreement with Merus N.V., while providing access to the product on a named-patient basis outside the U.S. This breakthrough bolsters PTx’s growing oncology portfolio, which also includes sargramostim (LEUKINE®, IMREPLYS®, SARGMALIN®) and other immune-modulating biologics. By combining immunotherapy expertise with genomic targeting, PTx is strengthening its footprint in rare-oncology markets and reinforcing investor confidence in its innovation pipeline. Pritesh J. Gandhi, PharmD, Chief Development Officer at PTx, commented, “With more actionable gene fusions being discovered, it’s essential that oncologists perform comprehensive RNA-based sequencing to identify patients who could benefit from targeted treatments such as zenocutuzumab-zbco.”
Patients’ Significance
Cholangiocarcinoma remains a highly aggressive and often fatal cancer, with limited standard therapy options and poor outcomes. For patients whose tumors harbor NRG1 gene fusions, zenocutuzumab-zbco offers a new, rationally designed precision therapy aimed at the underlying disease biology. Dr. Juan W. Valle, Chief Medical Officer of the Cholangiocarcinoma Foundation, emphasized, “The eNRGy trial results are encouraging, and they underscore how critical comprehensive molecular testing is for identifying rare genetic drivers such as NRG1.” For patients with few alternatives, the Breakthrough Therapy Designation signals hope for faster access to an effective, targeted option that could significantly extend survival and improve quality of life.
Policy Significance
The FDA’s decision underscores the agency’s continued commitment to precision-medicine pathways and support for biomarker-defined subpopulations. By prioritizing Breakthrough Therapies, the FDA accelerates access to high-impact drugs for rare cancers, aligning with federal policies that promote molecular diagnostics and genomic testing standards in oncology. This designation also supports broader policy goals under the U.S. Cancer Moonshot initiative, which aims to reduce cancer mortality and foster early access to personalized medicines through regulatory flexibility and scientific collaboration.
Transaction Highlights
The FDA’s Breakthrough Therapy Designation for zenocutuzumab-zbco represents a strategic inflection point for Partner Therapeutics. The designation provides regulatory acceleration, clinical validation, and commercial momentum, positioning the company for potential revenue expansion and strategic partnerships. From a development perspective, PTx gains access to intensive FDA collaboration during clinical advancement and expedited review timelines, shortening the path from trial data to market approval. Financially, the breakthrough status enhances investor confidence and may open opportunities for co-development alliances, milestone-based licensing, or capital infusion from strategic partners in oncology innovation. Operationally, the designation validates the company’s precision-oncology strategy and supports its continued investment in biologics targeting rare, genomically driven cancers. Overall, this milestone reinforces PTx’s position as a leader in next-generation cancer therapeutics built on genetic and immunologic insight.
Source: Partner Therapeutics, Inc. Press Release
