For in vitro diagnostic use. Membrane Others HER-2 neu 4B5 PATHWAY IVD Breast Carcinoma PATHWAY® anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody RTD001084 Rabbit 4B5 05 278 368 001 5 278 368 001 05278368001 5278368001 05278368001 PATHWAY ANTI-HER-2/NEU (4B5) RABBIT MONO PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody 04015630972197 Reagents, kits 790-2991 50 tests Not Available true PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody (PATHWAY anti-HER2 (4B5) antibody) is a rabbit monoclonal antibody intended for laboratory use for the semi-quantitative detection of HER2 antigen by immunohistochemistry (IHC) in sections of formalin-fixed, paraffin-embedded breast carcinoma, biliary tract cancer (gallbladder adenocarcinoma, intrahepatic cholangiocarcinoma, and extrahepatic cholangiocarcinoma) and gastroesophageal adenocarcinoma (gastric, gastroesophageal junction and esophageal adenocarcinoma) tissue using the ultraView Universal DAB Detection Kit on a BenchMark ULTRA or BenchMark ULTRA PLUS instrument.The IHC device is indicated for identifying patients who are eligible for treatment with the following therapies in accordance with the approved therapeutic labeling:Indication for useHER2 ScoreTherapyBreast carcinoma IHC 3+ or IHC 2+/ISH amplifiedHerceptin®Breast carcinoma IHC 3+ or IHC 2+/ISH amplifiedKADCYLA®Breast carcinoma IHC 3+ or ISH amplifieda ENHERTU®bBreast carcinoma IHC 0 with membrane staining, IHC 1+ or IHC 2+/ISH non-amplifiedENHERTU®Biliary tract cancercIHC 3+ ZIIHERA®Gastroesophageal adenocarcinomac IHC 3+ or IHC 2+/ISH amplifiedZIIHERA® in combination with fluoropyrimidine- and platinum-containing chemotherapy and tislelizumab-jsgrdGastroesophageal adenocarcinomac IHC 3+ ZIIHERA® in combination with fluoropyrimidine- and platinum-containing chemotherapyda See Scoring Convention section for use of ISH in context of the indication for use. b See ENHERTU® product label for specific clinical circumstances guiding HER2 testing. c Biliary tract cancer and gastroesophageal adenocarcinoma indications are only approved for use with BenchMark ULTRA instrument. d See the ZIIHERA® product label for specific clinical circumstances guiding HER2 testing. Test results should be interpreted by a qualified pathologist in conjunction with histological examination, relevant clinical information, and proper controls. This product is intended for in vitro diagnostic (IVD) use. en PATHWAY anti-HER2 (4B5) antibody is a rabbit monoclonal antibody, which binds to HER2 in formalin-fixed, paraffin-embedded (FFPE) tissue sections. The specific antibody is located by a cocktail of enzyme-labeled secondary antibodies that recognize rabbit immunoglobulins followed by the addition of a secondary antibody-HRP conjugate (ultraView Universal DAB Detection Kit). The specific antibody-enzyme complex is then visualized with a precipitating enzyme reaction product. Each step is incubated for a precise time and temperature. At the end of each incubation step, the BenchMark ULTRA or BenchMark ULTRA PLUS instrument washes the sections to stop the reaction and to remove unbound material that would hinder the desired reaction in subsequent steps. It also applies Liquid Coverslip, which minimizes evaporation of the aqueous reagents from the specimen slide. Clinical cases should be evaluated within the context of the performance of appropriate controls. The inclusion of a positive tissue control fixed and processed in the same manner as the patient specimen (for example, a weakly positive breast carcinoma) is recommended. In addition to staining with PATHWAY anti-HER2 (4B5) antibody, a second slide should be stained with CONFIRM Negative Control Rabbit Ig. For the test to be considered valid, the positive control tissue should exhibit membrane staining of the tumor cells. These components should be negative when stained with CONFIRM Negative Control Rabbit Ig. In addition, it is recommended that a negative tissue control (for example, a HER2 negative breast carcinoma, or non-staining components of the same tissue used for the positive tissue control) be included for every batch of samples processed and run on a BenchMark ULTRA or BenchMark ULTRA PLUS instrument. This negative tissue control should be stained with PATHWAY anti-HER2 (4B5) antibody to ensure that the antigen enhancement and other pretreatment procedures did not create false positive staining. The use of pre-diluted PATHWAY anti-HER2 (4B5) antibody and ready-to-use ultraView Universal DAB Detection Kit, in combination with a BenchMark ULTRA or BenchMark ULTRA PLUS instrument, reduces the possibility of human error and inherent variability resulting from individual reagent dilution, manual pipetting, and manual reagent application. en

PATHWAY^® anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody

IVD

Leading the way in HER2 testing¹

The use of pre-diluted PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody² (Roche HER2 (4B5)), in combination with the fully automated BenchMark IHC/ISH slide staining instrument, standardizes all IHC processes from baking through staining, and reduces the possibility of human error.²It also minimizes inherent variability resulting from individual reagent dilution and other processes found in manual and semi-automated IHC methods.

The Roche HER2 (4B5) clone* empowers you to:

Achieve consistently high proficiency assessment scores with the Roche HER2 (4B5) clone, compared to other clones¹
Employ the most widely adopted and reliable HER2 IHC primary antibody¹
Demonstrate high concordance with HER2 FISH^3,4

Consistent performance and superior quality¹

The Roche HER2 (4B5) clone* has shown the most consistent performance and superior quality when compared to other on-market HER2 clones.**

*Refers to the PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody and VENTANA® anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody products.

**Based on data from a leading external quality assessment scheme.¹

US IVD

Intended use²

PATHWAY anti-HER-2/neu (4B5) Rabbit Monoclonal Primary Antibody (PATHWAY anti-HER2 (4B5) antibody) is a rabbit monoclonal antibody intended for laboratory use for the semi-quantitative detection of HER2 antigen by immunohistochemistry (IHC) in sections of formalin-fixed, paraffin-embedded breast carcinoma, biliary tract cancer (gallbladder adenocarcinoma, intrahepatic cholangiocarcinoma, and extrahepatic cholangiocarcinoma) and gastroesophageal adenocarcinoma (gastric, gastroesophageal junction and esophageal adenocarcinoma) tissue using the ultraView Universal DAB Detection Kit on a BenchMark ULTRA or BenchMark ULTRA PLUS instrument.

The IHC device is indicated for identifying patients who are eligible for treatment with the following therapies in accordance with the approved therapeutic labeling:

Breast carcinoma: Herceptin® (IHC 3+ or IHC 2+/ISH amplified), KADCYLA® (IHC 3+ or IHC 2+/ISH amplified), ENHERTU®* (IHC 0 with membrane staining, IHC 1+ or IHC 2+/ISH non-amplified, IHC 3+ or ISH amplified**)
Biliary tract cancer***(BTC): ZIIHERA® (IHC 3+)
Gastroesophageal adenocarcinoma(GEA): ZIIHERA (IHC3+, IHC 3+ or IHC 2+/ISH amplified****)^✝

*See the therapeutic product label for specific clinical circumstances guiding HER2 testing.

**See Scoring Convention section for use of ISH in context of the indication for use.

***Biliary tract cancer indication is only approved for use with BenchMark ULTRA instrument.

**** GEA indication is only approved for use with the BenchMark ULTRA instrument.

^✝See the ZIIHERA product label for specific clinical circumstances guiding HER2 testing.

Test results should be interpreted by a qualified pathologist in conjunction with histological examination, relevant clinical information, and proper controls.

This product is intended for in vitro diagnostic (IVD) use.

Scoring Conventions for the Interpretation of PATHWAY HER2 (4B5) Antibody

Below is a quick reference chart for staining criteria. Refer to Interpretation Guide for PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody for a more detailed description with photographs of staining.

Scoring Criteria for Intensity and Pattern of Cell Membrane Staining with PATHWAY anti-HER2 (4B5) Antibody in Breast Carcinoma

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Staining Pattern	HER2 (4B5) Score (report to treating physician)	HER2 Status	Therapy
No membrane staining is observed*	IHC 0 absent membrane staining	HER2-null	None
Any staining of the membrane in greater than 0 and less than or equal to 10% of the cancer cells,,**	IHC 0 with membrane staining	HER2-ultralow expression	ENHERTU (fam-trastuzumab deruxtecan-nxki)
Faint, partial staining of the membrane in greater than 10% of the cancer cells*	IHC 1+	HER2-low expression
Weak to moderate complete staining of the membrane in greater than 10% of the cancer cells	IHC 2+**** Reflex test: HER2 Non-Amplified	HER2-low expression
	IHC 2+**** Reflex test: HER2 Amplified	HER2-positive / overexpression	HERCEPTIN (trastuzumab) KADCYLA (trastuzumab emtansine) ENHERTU***** (fam-trastuzumab deruxtecan-nxki)
Intense complete staining of the membrane in greater than 10% of the cancer cells	IHC 3+	HER2-positive / overexpression

* Review at 40x is recommended to discern the presence or absence of any staining such as faint, partial staining.
** Recommend re-reading by a second pathologist for cases classified as HER2-null or as HER2-ultralow expression with %Tumor Cells (%TC) ≤ 5%.
*** In the HER2-ultralow “IHC 0 with membrane staining” category, partial membranous staining is usually faint but may exhibit stronger intensities, and such rare cases are scored as HER2-ultralow if they do not otherwise qualify for a higher score. Refer to the Interpretation Guide for case examples.
**** Recommend reflex test to assess gene amplification per ASCO/CAP guidelines.
***** See the therapeutic product label for specific clinical circumstances guiding HER2 testing.

Scoring Criteria for Intensity and Pattern of Cell Membrane Staining with PATHWAY anti-HER2 (4B5) Antibody in Biliary Tract Cancer

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Table 2. Scoring Criteria for Intensity and Pattern of Cell Membrane Staining with PATHWAY HER2 (4B5) Antibody in Biliary Tract Cancer
Staining Pattern (resection specimen)	Staining Pattern (biopsy specimen*)	HER2 (4B5) Score (report to requesting physician)	HER2 Status	Therapy
No reactivity or membranous reactivity in <10% of tumor cells	No reactivity membranous reactivity in any tumor cell	IHC 0	HER2 negative	Treatment ineligible
Faint/barely perceptible membranous reactivity in ≥10% of tumor cells; cells are reactive only in part of their membrane	Tumor cell cluster** with a faint/barely perceptible membranous reactivity irrespective of percentage of tumor cells stained	IHC 1+
Weak to moderate complete, basolateral or lateral membranous reactivity in ≥10% of tumor cells***	Tumor cell cluster with a weak to moderate complete, basolateral or lateral membranous reactivity irrespective of percentage of tumor cells stained***	IHC 2+
Strong complete, basolateral or lateral membranous reactivity in ≥10% of tumor cells***	Tumor cell cluster with a strong, complete basolateral or lateral embranous reactivity irrespective of percentage of tumor cells stained***	IHC 3+	HER2 positive	ZIIHERA® (zanidatamab)

* Biopsy specimens include endoscopic, pinch (forceps), and needle core.
** ≥ 5 cohesive cells.
*** Recommend re-reading by a second pathologist for cases with "strong complete basolateral or lateral membranous reactivity" and a %TC (resection specimens) near the threshold of 10% (range of %TC between 1%-20%) or tumor cell cluster (biopsy specimens) of 5 cohesive cells (tumor cell cluster between 1-20 cohesive cells).

Scoring Criteria for Intensity and Pattern of Cell Membrane Staining with PATHWAY anti-HER2 (4B5) Antibody in Gastroesophageal Adenocarcinoma

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Staining pattern specimen	Staining pattern (biopsy specimen^a)	HER2 (4B5) Score (report to requesting physician)	Recommended Reporting Status	Therapy
No reactivity or membranous reactivity in < 10% of	No reactivity or membranous reactivity in any tumor cell	0	HER2 Negative	Treatment ineligible
Faint/barely perceptible membranous reactivity in ≥ 10% of tumor cells; cells are reactive only in part of their membrane Weak to moderate complete, basolateral or lateral membranous reactivity in ≥ 10% of tumor cells^d	Tumor cell cluster^b with a faint/barely perceptible membranous reactivity irrespective of percentage of tumor cells stained	1+
	Tumor cell cluster with a weak to moderate complete, basolateral or lateral membranous reactivity irrespective of percentage of tumor cells stained	2+^c Reflex test: HER2 non-amplified
		2+^c Reflex test: HER2 amplified	HER2 Positive	ZIIHERA® in combination with fluoropyrimidine-and platinum-containing chemotherapy, and tislelizumab-jsgr^e
Strong complete, basolateral or lateral membranous reactivity in ≥ 10% of tumor cells^d	Tumor cell cluster with a strong, complete basolateral or lateral membranous reactivity irrespective of percentage of tumor cells stained	3+	HER2 Positive	ZIIHERA® in combination with fluoropyrimidine-and platinum-containing chemotherapy, with or without tislelizumab-jsgr^e

^a Biopsy specimens include endoscopic, pinch, and needle core
^b ≥ 5 cohesive cells
^c Recommend reflex test to assess gene amplification
^d Recommend re-reading by a second pathologist for cases with "weak to moderate complete, basolateral or lateral membranous reactivity" or "strong complete basolateral or lateral membranous reactivity" and a %TC (resection specimens) near the threshold of 10% (range of %TC between 1%-20%) or tumor cell cluster (biopsy specimens) of 5 cohesive cells (tumor cell cluster between 1-20 cohesive cells)
^e See the ZIIHERA^® product label for specific clinical circumstances guiding HER2 testing

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References

NordiQC Assessments. https://www.nordiqc.org/epitope.php?id=11. Accessed January 28, 2025.
PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody Package Insert (14427US Rev Q), 2026.
Mayr D, et al. Comprehensive immunohistochemical analysis of Her-2/neu oncoprotein overexpression in breast cancer: HercepTest™ (Dako) for manual testing and Her2/neuTest 4B5 (VENTANA) for VENTANA BenchMark automatic staining system with correlation to results of BenchMark automatic staining system with correlation to results of fluorescence in situ hybridization (FISH). Virchows Archiv. 2009; 454(3):241–248.
Brügmann A, Lelkaitis G, Nielsen S, et al. Testing HER2 in breast cancer: a comparative study on BRISH, FISH, and IHC. Appl Immunohistochem Mol Morphol. 2011;19(3):203-211.

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