TEST:

PATHWAY antiHer2/neu (4B5) Rabbit Monoclonal Primary Antibody

This study suggested that two-thirds of HER2-negative unresectable/mBC patients in Taiwan were HER2-low. Reassessing the HER2 status of HER2-negative patients could improve treatment strategies with the evolving HER2 classification paradigm.

P1, N=45, Recruiting, Baylor College of Medicine | Trial primary completion date: Dec 2024 --> Dec 2025

"Roche...U.S. Food and Drug Administration (FDA) has approved a label expansion for the PATHWAY® anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody* to identify patients with HR-positive, HER2-ultralow metastatic breast cancer who may be eligible for treatment with ENHERTU®."

Despite distinct clinicopathological features, FISH remains inadequate for distinguishing HER2-low from HER2-ZERO expression. Further studies are needed to improve HER2 assessment in this challenging subset of patients.

Now, based on the DESTINY Breast-04 Trial (DB-04) results, for patients with metastatic breast cancer it underpins eligibility for T-DXd treatment...Having validated our approach, we will use these reference case sets with expert level consensus scores for peer training and updating our national HER2 IHC external quality assurance program. In our ongoing studies, we are also assessing the performance of software algorithms to determine their suitability for pre-screening of HER2 IHC slides.

"Roche...announced...the U.S. Food and Drug Administration (FDA) approval of a label expansion into biliary tract cancer (BTC) for the PATHWAY anti-HER2/neu (4B5) Rabbit Monoclonal Primary Antibody test. This test is now the first and only FDA-approved companion diagnostic to aid in the assessment of HER2-positive status to identify BTC patients who are eligible for treatment with Jazz Pharmaceuticals' ZIIHERA (zanidatamab-hrii)."

Among 22 HER2-positive/heterogenous cases with successful ISH testing, 100% (22/22) demonstrated amplification via ISH. Because the classification of tumors as HER2-positive/heterogenous by IHC correlated very closely with ISH positivity, our results suggest that ISH is likely unnecessary for CRCs with 3+ HER2 overexpression in 10-49% of neoplastic cells.

median ERBB2 = 31 TPM in IHC intensity of 0+, 48 TPM in IHC of 1+; 84 TPM in IHC of 2+, and 445 TPM of IHC of 3+ (p<0.0001). Using a multi-omic approach, we thoroughly surveyed gene expressions on pathways associated with antibody-drug conjugate resistance mechanisms. By examining clinical outcome data from 1144 breast cancer patients treated with T-DXd, our data suggest that at an intracellular level TDXd outcome is a function of drug concentration influx and time to efflux.

Recently, FDA approved antibody drug conjugate (ADC) trastuzumab deruxtecan (T-DXd; Enhertu®) for the treatment of metastatic HER2-positive and HER2-low breast cancer. We demonstrated high slide-level agreement of the AI-based estimate of HER2 expression in tumor regions and the ground-truth with Pearson correlation of 0.94, and R2 of 0.87. In the future we expect AI-assisted quantification and visualization of HER2 expression to enable fast and safe treatment decisions.

Background The efficacy of fam-trastuzumab deruxtecan-nxki (T-DXd) in patients with HER2-low (IHC 1+ or IHC 2+/ISH negative) mBC was established by results of DESTINY-Breast04 and substantiated in DESTINY-Breast06 (HR+/HER2-low), which explored T-DXd efficacy in HER2-ultralow (IHC 0 with ≤10% cells with faint, incomplete membrane staining) as a secondary endpoint...Conclusions While 28.3% of IHC 0 WSI were rescored as HER2-ultralow, 65.8% could be reclassified with a clinically actionable level of expression (HER2-ultralow or IHC 1+). The discrepancies in scoring and a trend to extended review times for HER2-ultralow and IHC 1+ highlight the need for training, digital tools for decision support, and increased awareness of the available therapies for HER2-ultralow and IHC 1+ cases, to motivate pathologists to improve consistency in scoring for optimal patient care and treatment selection.

Overall, there was strong agreement between the two methodologies; however, the AI solution outperformed manual scoring in 24 cases (8.3%), which would otherwise be deemed unsuitable for treatment. Notably, the membrane staining in the 11 cases re-scored by AI as 0, was just bellow the 10% threshold currently established by UK and ASCO/CAP guidelines, underscoring the challenges in achieving precision in borderline cases through manual scoring. Given the unique nature of our unit, it is anticipated that a greater number of discordant cases may be identified in different clinical settings.

The AI solution demonstrated high accuracy and generalizability to multiple different laboratories (pre-analytics and staining protocols) and scanners. AI solutions, such as the one investigated here, could be used as decision-support tools for pathologists in routine clinical practice, enhancing the reproducibility and consistency of HER2 scoring, thus enabling optimal treatment pathways and improved patient outcomes.

Background Treatment with trastuzumab deruxtecan improved outcomes compared with standard of care for human epidermal growth factor receptor 2 (HER2)-low (immunohistochemistry [IHC] 1+ or IHC 2+ with in situ hybridization negative) metastatic breast cancer (BC) in DESTINY-Breast04 and DESTINY-Breast06...PPA tended to be higher than NPA, suggesting more consistent detection of HER2-low compared to HER2 IHC 0. Awareness of available novel treatment options, deliberate pathologist training, and optimization of analytical assay methods and their choice are indicated for accurate identification of patients with clinically actionable HER2 expression levels.

The advent of novel therapeutic molecules that require fewer membrane epitopes to be effective has prompted a reevaluation of the current immunohistochemistry testing protocols, with special emphasis on the detection limit. Here, we have used Boston Cell Standards technology to determine the sensitivity of 2 commercially available HER2 immunohistochemistry assays, including a lower limit of detection.

A significant proportion of previous 'HER2-negative' primaries and DM cases were reclassified as HER2-low. Discordant HER2 status between IBC primary and metastasis and between different DM sites demonstrated tumour heterogeneity and highlights the need for HER2 retesting in distant metastasis.

Conclusions This study, per the rescored HER2 IHC, suggests that up to two-thirds of HER2-negative unresectable/mBC patients in Taiwan were HER2-low and may benefit from T-DXd. Findings indicate that re-evaluating the HER2 status of HER2-negative patients may enhance treatment approaches with the evolving HER2 classification paradigm.

This study reports an independent validation of a fully automated AI solution for HER2 scoring in BC. Our results show high accuracy for the AI, suggesting that AI can improve reproducibility and standardization of HER2 scoring in BC and additional validation studies are ongoing

HER2 IHC interpretation has a history of controversy due to competing scoring schema. Additionally, before 2022 no HER2 targeted treatment was available for the lower expression profiles (0, 1+, and 2+/ISH negative) and thus did not command the same level of interest as they do now. Here we demonstrate that the PATHWAY HER2 (4B5) assay is robust and reproducible in identifying HER2- ultralow tumours.

The overall consistency of HER2 expression between antibodies of different clone numbers was high, but the consistency of detecting HER2 low and ultra-low expression cases was poor, and there were differences in the detection rates, which still need to be validated by more subsequent studies.

Context: Human epidermal growth factor receptor 2 (HER2) overexpression in breast carcinomas offers the use of a targeted treatment approach with the monoclonal antibody trastuzumab... Manual immunohistochemical scoring of HER2 has high interobserver variability among the 0+ to 2+ categories. In the context of emerging HER2-low therapies and clinical trials, additional specific criteria are necessary for HER2 immunohistochemistry interpretation to improve reproducibility among pathologists.Fleiss κ Scores for HER2 IHC Agreement Among Categories 0+ to 2+

Recently, a new type of antibody-drug conjugate, trastuzumab-deruxtecan (T-DXd), has been approved for the treatment of metastatic breast cancer with low level of human epidermal growth factor receptor 2 (HER2) gene expression...The ability of pathologists to achieve acceptable diagnostic accuracy in identifying patients with HER2-low breast cancer could be enhanced by short-term training. Potential routes to improve the quality of HER2-low scoring in clinical practice have been identified.

As assays were validated for detecting HER2-amplified tumours, not all assays and antibodies proved suitable for HER2-low detection. Some tests showed distinct expression in the negative cell line. Dynamic range cell line controls and quantitative analysis using calibrators demonstrated more interlaboratory variability than commonly appreciated. Revalidation of HER2 tests by laboratories is needed to ensure clinical applicable HER2-low assays.

AI excels in automating the assessment of HER2 immunohistochemistry, showing promising results despite slight variations in performance across different HER2 status. While incorporating AI algorithms into the pathology workflow for HER2 assessment poses challenges in standardization, application patterns, and ethical considerations, ongoing advancements suggest its potential as a widely effective tool for pathologists in clinical practice in the near future.

While gastric and breast criteria demonstrated 96% concordance in identifying EEAs positive for HER2 overexpression, equivocal staining was more often documented with gastric scoring. This greater frequency of equivocal results may suggest a preference for gastric criteria in the assessment of EEA, matching trial inclusion criteria where clinical benefit of HER2 ADCs has been established in patients with HER2 equivocal tumors. Table: 739P Concordance and discordance of HER2 IHC calls by gastric and breast criteria

HER2-OE was relatively low across GTs, though certain histotypes and molecular features (HRD negative OCs, p53 abnormal EC and adenocarcinomas/CPS<1% CC) exhibited higher scores. The high CR suggests either scoring guideline may be suitable for GTs. HER2-OE's predictive/prognostic value in GTs requires further evaluation.

Local vs central HER2 agreement by standardized IHC techniques decreased for HER2-low compared to HER2 status. Monoclonal HercepTest proved higher agreement with gold standard than polyclonal HercepTest in terms of HER2 status and HER2-low BC identification, especially for 1+ and 2+ IHC cases. This highlights the need for standardized HER2 testing review, particularly when evaluating potential benefits of novel therapies for HER2-low BC patients.

In March 2019, AstraZeneca entered into a global development and commercialization collaboration agreement with Daiichi Sankyo for trastuzumab deruxtecan (T-DXd; DS-8201)... Data show the gastric and breast algorithms are comparable in HER2 IHC 3+ identification; lower concordance was observed for IHC 2+ and 1+, and between the gastric and endometrial algorithms. Findings indicate greater awareness of best scoring practice is needed to ensure consistent assessment of HER2 IHC status in solid tumors. Table: 177P *Salivary gland tumors (n=18) and DP-02 other cohort; †PPA was 100% as no cases identified by gastric/breast algorithm

Pts with HR+ mBC determined as HER2-low or HER2-ultralow using the VENTANA HER2 (4B5) assay (and ISH when applicable) derived clinical benefit from T-DXd, irrespective of sample type used to determine HER2 status. Of note, 64% of pts with a local HER2 IHC 0 score were classed as HER2-low or HER2-ultralow by central test. It may be advisable for pts with HR+ HER2 IHC 0 mBC to be reassessed to determine T-DXd eligibility.

HER2 scores vary markedly between different clinically approved HER2 antibodies, both in primary tumours and their corresponding metastasis, and across different antibodies. Especially DG44 deviated from the other antibodies. Discrepancies in testing methods could impact patient selection for Trastuzumab-deruxtecan treatment.

The HER2 “ultra-low� category is not currently recognized as a target for new HER2 anti-ADCs. However, this could change soon depending on the results of ongoing clinical trials. If this becomes the case, HER2 assays must provide supporting evidence on their capability to accurately differentiate HER2 null from HER2 “ultra-low�.

The real-world data on HER2 assessment concordance, in the spectrum of HER2-low BC, although substantial, are not perfect even among experienced breast pathologists. Concordance was significantly better with the Ventana 4B5 clone, which provided a majority of score 0 cases. On the contrary, with the Novacastra/Leica CB11 clone the 2+ score prevailed.

After administering a total of 17 courses of eribulin, she was evaluated as having PD due to pleural dissemination. She then administered 3 courses of paclitaxel-bevacizumab therapy, but developed aphasia...After that, five courses of the drug were administered as outpatients, and both brain metastasis and pleural dissemination achieved partial response, and tumor markers gradually decreased. Conclusion In cases where symptom improvement can be expected by surgical local treatment of the brain metastasis responsible lesion, as in this case, treatment aimed at improving ADL with an eye on the application of the drug may also be considered

Background Trastuzumab deruxtecan (T-DXd), an antibody-drug conjugate (ADC), has shown favorable PFS and OS for HER2-positive unresectable or metastatic breast cancer in a series of DESTINY trials, and can now be said to be a key drug in the treatment of metastatic breast cancer.In March 2023, its indications were expanded to include "inoperable or recurrent breast cancer with low HER2 expression and a history of chemotherapy." The diagnosis of HER2 low expression requires confirmation by Ventana ultraView Pathway HER2 (4B5) as a companion diagnostic, and specimens stained after March 27, 2023 must be evaluated for past specimens...&lsqb;Discussion] In this study, no difference was found in the low expression rate at the time of specimen collection, but the HER2 low expression rate in in-hospital IHC staining and 4B5 evaluation differed greatly. There was also a large discrepancy in diagnosis between pathologists, and it was considered important to resubmit 4B5 regardless of the IHC judgment at the time of initial onset, or to re-evaluate HER2 by aggressive re-biopsy in metastatic lesions

Of the 51 cases, 15 (29%) were HER2 0, 30 (59%) were 1+, and 6 (12%) were 2+. Of the 36 cases with low HER2 expression, 18 (60%) were ER positive/ER negative/12 (40%). One case was originally HER2 0 but changed to HER2 low expression, and conversely, 8 cases changed from low expression to HER2 0, with a concordance rate of HER2 status of 87.5% for HER2 0 and 73% for low expression.

The subjects consisted of 9 advanced breast cancers and 14 recurrent breast cancers, with 11 (47.8%) patients with high HER2 expression and an average age of 65.7 years, and 12 (52.2%) patients with low HER2 expression and an average age of 64.1 years. The patients with low HER2 expression showed a score of 1 on the Ventana Ultra View Pathway HER2 (4B5). Sixteen patients were HR positive and seven were negative, with HR positive accounting for 83.3% of the patients with low HER2 expression.

Background In the DESTINY-Breast04 (DB-04) study, trastuzumab plus deruxtecan therapy was administered to patients with HER2-low expressing breast cancer. Adverse events were almost the same as when used in HER2 positive cases. Conclusion In clinical practice, T-DXd therapy for HER2-low expressing breast cancer does not have a high response rate, but the clinical benefit rate is relatively good, and it is considered to be a new treatment option

After postoperative radiation therapy, the patient took capecitabine for 10 months...After 13 sessions of eribulin as chemotherapy, 8 sessions of fulvestrant + abemaciclib were administered, resulting in PR. After that, eribulin + palbociclib was administered due to bone metastasis progression, but the patient did not progress, resulting in PD...Furthermore, by using T-DXd, which has a different therapeutic mechanism, it was possible to shrink the tumor and improve the patient's quality of life, despite its late use as the seventh regimen. Conclusion We have observed a case in which changing the treatment method in accordance with the change in subtype of recurrent breast cancer produced an antitumor effect

Eight patients were hormone receptor (HR) positive and HER2 negative, four were HR negative and HER2 negative, four were stage IV, and eight were recurrent cases. The median number of lines of T-Dxd treatment for metastatic or recurrent breast cancer was five (2-12), with only one patient receiving the second line and 11 receiving the third line or later. The maximum therapeutic effect was PR in 3 patients, SD in 3 patients, PD in 3 patients, and NE in 3 patients.

The median age was 59 years (range 47 to 66 years), all patients were female, and the subtypes were luminal B in three cases and triple-negative in one case. The median number of chemotherapy regimens administered was 3.5 (range 3 to 6), and the breakdown of metastatic lesions was lung pleura in two cases, regional lymph nodes in two cases, bone in two cases, liver in one case, chest wall in two cases, and skin in one case. Clinical efficacy was PR in one case, SD in one case, and PD in two cases, with one case of death due to multiple organ failure and one case of death from current disease.

After starting pembrolizumab + carboplatin (CBDCA) + weekly-paclitaxel (wPTX), she developed fatigue, nausea, and loss of appetite...When using them, it is necessary to pay close attention to immune-related adverse events, which are a concept different from the adverse events of conventional cytotoxic antitumor drugs. In addition, in cases such as Case 2, it is difficult to choose the postoperative therapy

Background Trastuzumab decrustecan has been shown to be effective in treating patients with HER2 low-expressing breast cancer. All 18 patients were female, with a median age of 62 years (44-75 years), 2 patients (11.1%) were premenopausal, and 16 patients (88.9%) were postmenopausal. Thirteen cases (72.2%) were recurrent, five cases (27.8%) were de novo Stage IV, 16 cases (88.9%) had visceral metastases, and three cases (16.7%) had brain metastases. Biology: 14 cases (77.8%) were hormone receptor (HR) positive, four cases (22.2%) were HR negative, and 14 cases (77.8%) were HER2 1+ and four cases (22.2%) were HER2 2+ by companion diagnosis using HER2 4B5.

[Cases] (Onset, CDK4/6 inhibitor, and Enhertz use start date are listed) Case 1: Right-sided breast cancer treated with conservative therapy (BCT) on 2013/3/13, pleural metastasis on 2016/3, 2019/2/7 ~ Faslodex (FAS) + Verzenio, 2023/11/8 ~ Enhertz, tumor markers decreasing Case 2: 2001/6/29 BCT for right breast cancer, 2012/12 pleural and abdominal wall metastases, 2018/6/14 ~ Ibrance + Letrozole (LET), 2019/1/31 ~ FAS + Verzenio, 2023/9/27 ~ Enhertz, tumor markers decreasing Case 3: 2011/2/4 Right stage IV breast cancer, lymph node and bone metastases, 2022/11/16 mastectomy after chemotherapy (Bt + Ax), 2019/2/7-2019/9/12 Exemestane (EXE) + Verzenio, 2021/10/20 ~ 2021/12/15EXE Ibrance, 2023/7/19 ~ Enhertz, Tumor marker decreased, but after 6 cycles interstitial pneumonia developed, improved with pulse therapy, treatment for recurrence ended, transitioned to palliative care Case ④: 2014/6/18Bilateral breast cancer, bilateral BCT, 2019/3Pleural dissemination and bone metastasis, 2020/4/16 ~ 2020/8/5EXE + Vergenio, 2021/12/1 ~ 2023/1FAS + Ibrance, 2023/10 ~ Enhertz, under observation Case ⑤: 2012/9/19Left breast cancer, Bt + Ax (with FISH amplification), 2018/7Resection due to chest wall recurrence, then chest wall recurrence + supraclavicular metastasis, No FISH amplification in repeat biopsy, 2019/11/28 ~ 2021/5 FAS + Verzenio, 2023/10/4 recurrence in precordial area, 2023/11/8 ~ Enhertz, under observation Case ⑥: 2007/11/21 Left breast cancer, preoperative chemotherapy followed by Bt + Ax, 2010/12 liver metastasis, 2019/2/7 ~ 2021/4/13 LET + Verzenio, 2021/4/14 ~ FAS + Verzenio, 2023/1/15 ~ Nolvadex (TAM) + Verzenio, recent tumor marker increase, scheduled to switch to Enhertz from 2024/1. &lsqb;Results] Enhertz therapy is effective, but under observation. One patient developed interstitial pneumonia, but it improved