The U.S. Food and Drug Administration (FDA) has approved additional indications for the Roche PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody and VENTANA HER2 Dual ISH DNA Probe Cocktail tests.
These tests are now approved to help identify HER2-positive metastatic breast cancer (mBC) patients who may be eligible for treatment with trastuzumab deruxtecan (Enhertu®; Daiichi Sankyo and AstraZeneca), an engineered HER2-directed antibody-drug conjugate (ADC) composed of a humanized immunoglobulin G1 monoclonal antibody specifically targeting HER2, a tetrapeptide-based cleavable linker, and a potent topoisomerase I inhibitor payload.
In the United States, trastuzumab deruxtecan is approved for the treatment of adult patients with unresectable or metastatic HER2-positive (IHC 3+, ISH+) breast cancer (mBC) who have received a prior anti-HER2-based regimen. More recently, trastuzumab deruxtecan was also approved in the United States and the European Union for patients with HR-positive, HER2-low (IHC 1+, IHC 2+/ISH-negative) or HER2-ultralow (IHC 0 with membrane staining) breast cancer following disease progression after one or more endocrine therapies in the metastatic setting. This latter setting extends the previous approval of trastuzumab deruxtecan for use after prior chemotherapy in the metastatic setting, or after disease recurrence within 6 months of completing adjuvant chemotherapy, in patients with HER2-low breast cancer.[1]
Expanded approval
Until now, Roche’s PATHWAY HER2 (4B5) test had been approved for identifying mBC patients with HER2-low and HER2-ultralow expression. With this expanded approval, Roche’s PATHWAY HER2 (4B5) test, when combined with the VENTANA HER2 Dual ISH DNA Probe Cocktail, can now be used to identify patients across the full spectrum of HER2 expression for potential eligibility for trastuzumab deruxtecan.
This approval reflects the vital role of advanced diagnostics in guiding precise treatment decisions to address the diverse needs of mBC patients.
“Metastatic breast cancer remains a significant challenge,” noted Laura Apitz, Head of Pathology Lab at Roche Diagnostics.
“Diagnostic advances like these bring much-needed hope for patients. With this approval, our breast diagnostic portfolio can further guide therapy decisions for clinicians, enabling a more personalised approach,” Apitz added.
HER2 Breast Cancer
Breast cancer now represents one in four of all cancers diagnosed in women worldwide. [2] Despite advances in care, metastatic breast cancer poses a growing challenge, especially in younger populations, [3][4] where cases among women aged 25 to 39 increased by 32% between 2009 and 2015. [3][4]
However, treatment for metastatic breast cancer is evolving as our understanding of HER2 biology deepens, revealing that HER2 expression exists on a continuous spectrum rather than as distinct ‘positive‘ or ‘negative‘ categories.[5]
These diagnostics strengthen Roche’s broader breast cancer portfolio, which offers solutions across the full spectrum of breast cancer management, including key predictive assays. Roche remains committed to supporting patients with advanced diagnostic tools that help clinicians improve outcomes and deliver more personalized care at every stage of the disease.
PATHWAY anti-HER2/neu
The PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody delivers timely, clear, and reliable results, enhancing diagnostic certainty and enabling therapeutic decisions that can lead to better patient outcomes.
Previously indicated as an aid to identify certain breast cancer patients eligible for HER2-targeted treatment with trastuzumab (Herceptin®; Genentech/Roche), trastuzumab emtansine (Kadcyla®; Genentech/Roche), or trastuzumab deruxtecan,[6] the test is used in combination with the fully automated BenchMark ULTRA and BenchMark ULTRA PLUS staining platforms.
The assay standardizes all IHC (immunohistochemistry) processes from baking through staining, and reduces the possibility of human error. [6] It also minimizes inherent variability arising from individual reagent dilutions and other processes in manual and semi-automated IHC methods.
The HER2 (4B5) clone consistently achieves higher proficiency assessment scores than other clones [7]. It demonstrates high concordance with HER2 FISH [8][9], enabling laboratories to use the most widely adopted and reliable HER2 IHC primary antibody.
VENTANA HER2 Dual ISH DNA Probe
The VENTANA HER2 Dual ISH DNA Probe Cocktail assay is a fully automated, ready-to-use brightfield solution for determining HER2 gene status. VENTANA HER2 Dual ISH helps identify breast cancer patients eligible for personalized HER2-targeted therapy. The VENTANA HER2 Dual ISH DNA Probe Cocktail assay is optimised for use with the VENTANA Silver ISH DNP Detection Kit and the VENTANA Red ISH DIG Detection Kit on the fully-automated BenchMark ULTRA and BenchMark ULTRA PLUS staining platforms.[10]
This assay is an enhanced version of the previous-generation test. New oligonucleotide probes and highly sensitive detection kits provide precise results to pathology labs more quickly, allowing clinicians to make treatment decisions earlier.
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Highlight of prescribing information
Trastuzumab deruxtecan (Enhertu®; Daiichi Sankyo and AstraZeneca)[Prescribing Information]
Trastuzumab (Herceptin®; Genentech/Roche)[Prescribing Information]
Trastuzumab emtansine (Kadcyla®; Genentech/Roche)[Prescribing Information]
References
[1] Shami R, Salgado R, Bardia A, Curigliano G, Hu X, Dent R, Pierga JY, Tsurutani J, Wildiers H, Ricciardi G, Marchiò C, Penault-Llorca F, Bor-Angelier C, Manoogian M, Lucas S, Olson MT, Liu X, Toro P, Baker AF, Fang Q, Su J, Yoder A, Andrzejuk-Ćwik A, Darilay A, Matsuo T, Jones F, Viale G. Analytical and clinical validation of PATHWAY HER2 (4B5) assay for assessment of HER2-low/HER2-ultralow status and eligibility for trastuzumab deruxtecan in DESTINY-Breast06. ESMO Open. 2025 Jun;10(6):105310. doi: 10.1016/j.esmoop.2025.105310. Epub 2025 Jun 9. PMID: 40494041; PMCID: PMC12180978.
[2] Breast Cancer Resource Foundation [Internet; cited 21 Nov 2024] Online. Last accessed on December 15, 2025. Online. Last accessed on December 15, 2025
[3] Breast Cancer Resource Foundation [Internet; cited 2024 Oct 8] Online. Last accessed on December 15, 2025
[4] Hendrick RE, Helvie MA, Monticciolo DL. Breast Cancer Mortality Rates Have Stopped Declining in U.S. Women Younger than 40 Years. Radiology. 2021 Apr;299(1):143-149. doi: 10.1148/radiol.2021203476. Epub 2021 Feb 9. PMID: 33560186.
[5] Morrar D, Brogi E, Schwartz CJ, Pareja F, Wen HY, Ross DS. Human Epidermal Growth Factor Receptor 2 (HER2)-Ultralow Breast Cancer: Incidence, Clinicopathologic Features, and Need for Refined Scoring System. Mod Pathol. 2025 Sep 29;38(12):100901. doi: 10.1016/j.modpat.2025.100901. Epub ahead of print. PMID: 41033579., doi:
[6] Roche. PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody, US Package Insert (D218295 Rev 2). 2025.
[7] NordiQC Assessments. Online. Last accessed on January 28, 2025.
[8] Mayr D, Heim S, Werhan C, Zeindl-Eberhart E, Kirchner T. Comprehensive immunohistochemical analysis of Her-2/neu oncoprotein overexpression in breast cancer: HercepTest (Dako) for manual testing and Her-2/neuTest 4B5 (Ventana) for Ventana BenchMark automatic staining system with correlation to results of fluorescence in situ hybridization (FISH). Virchows Arch. 2009 Mar;454(3):241-8. doi: 10.1007/s00428-009-0728-8. Epub 2009 Jan 24. PMID: 19169706.
[9] Brügmann A, Lelkaitis G, Nielsen S, Jensen KG, Jensen V. Testing HER2 in breast cancer: a comparative study on BRISH, FISH, and IHC. Appl Immunohistochem Mol Morphol. 2011 May;19(3):203-11. doi: 10.1097/PAI.0b013e3181f7118e. PMID: 21475037.
[10] Roche. VENTANA HER2 Dual ISH DNA Probe Cocktail, US Package Insert (D218296 Rev 1). 2025.
This article was first published in ADC Review | J. Antibody-drug Conjugates on Monday, December 15, 2025.
Featured image © 2016 – 2025 Fotolia/Adobe. Used with permission.
DOI
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