Therapy For HER2-positive Breast Cancer Research Articles

Abstract PO3-01-01: Dysregulation of Phenylalanine-tyrosine Metabolic Signaling Pathway and Neoadjuvant Response in HER2-positive Breast Cancer

Abstract Background: Although trastuzumab and tyrosine inhibitors combined with neoadjuvant chemotherapy could significantly improve patients' pathological complete response (pCR) rate, nearly half of the patients could not achieve complete remission. Our objective was to explore the relationship between metabolic signaling pathway changes and therapeutic efficacy in patients receiving neoadjuvant therapy for HER2-positive breast cancer. Methods: Core needle biopsy specimens from HER2-positive breast cancer patients who underwent neoadjuvant therapy and radical mastectomy at Fudan University Shanghai Cancer Center between January 2017 and December 2021 were collected for RNA sequencing. According to pathological evaluation, samples (n=133) were divided into pCR and non-pCR groups. Gene differences between the two groups were further evaluated for KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analysis. The TCGA (The Cancer Genome Atlas, n=1091) and the HAN ethnic GEO datasets (GSE162228, GSE206, GSE48391, n=305) were used to analyze the metabolic differences between tumors and normal tissues with patients’ prognosis. Consensus clustering analysis was performed to divide patients for low and high phenylalanine-tyrosine metabolism dysregulation to analyze patients’ outcomes. The IC50 value of cell lines was tested using CCK-8 experiments. Western blot was performed to analyze the protein level changes in mTOR and glycolysis pathway. Results: We found that phenylalanine-tyrosine metabolism was significantly enriched in HER2-positive breast cancer patients. Consensus clustering analysis of TCGA and the HAN ethnic GEO datasets showed that patients with low phenylalanine-tyrosine catabolism had a significantly worse survival outcome than patients with high tyrosine metabolism (P= 0.017). In our cohort, phenylalanine-tyrosine pathway metabolic enzyme DDC was upregulated while MAOA was downregulated in non-pCR patients compared to pCR patients, suggesting the increased production of dopamine and reduced catabolism of dopamine (DA) in non-pCR tumors. In vitro experiments showed that dopamine and the knockdown of MAOA decreased cell sensitivity to pyrotinib. In addition, dopamine and clorgyline- an MAOA inhibitor, promoted the proliferation of HER2-positive cell lines under the treatment of pyrotinib. The GSEA analysis of our neoadjuvant cohort and TCGA datasets revealed that MAOA expression was associated with an inverse enrichment of the mTORC1 and glycolysis pathways. Western blot experiment results showed that dopamine or the knockdown of MAOA could activate the mTOR and glycolysis pathway Conclusions: Phenylalanine-tyrosine metabolism was significantly enriched in HER2-positive breast cancer patients. The phenylalanine-tyrosine signaling pathway may be dysregulated in HER2-positive breast cancer and patients with low phenylalanine-tyrosine catabolism have a worse prognosis. Low expression of MAOA promotes tumor resistance to HER2-targeted drugs and could serve as a therapeutic biomarker in breast cancer. Citation Format: Chih Wan Goh, Bingqiu Xiu, Jingyan Xue, Yayun Chi, Jiong Wu. Dysregulation of Phenylalanine-tyrosine Metabolic Signaling Pathway and Neoadjuvant Response in HER2-positive Breast Cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO3-01-01.

The efficacy and safety of trastuzumab and albumin-bound paclitaxel with or without pyrotinib as neoadjuvant therapy for HER2-positive breast cancer: a prospective observational cohort study

The efficacy and safety of trastuzumab and albumin-bound paclitaxel with or without pyrotinib as neoadjuvant therapy for HER2-positive breast cancer: a prospective observational cohort study

Current Status and Future Prospects of Neoadjuvant Therapy for HER2-positive Breast Cancer

Current Status and Future Prospects of Neoadjuvant Therapy for HER2-positive Breast Cancer

Exploring Anticancer Properties of Medicinal Plants against Breast Cancer by Downregulating Human Epidermal Growth Factor Receptor 2.

Plants have a history of being employed in managing breast cancer. However, no scientific evidence supports the idea that these plants can effectively reduce the level of HER2 expression. In this study, extracts from 10 medicinal plants were evaluated for their anticancer properties against HER2-positive breast cancer cells through various methods, including the SRB assay, comet assay, annexin V-FITC dual staining, and immunoblotting. All extracts exerted antiproliferative activity against HER2-positive breast cancer cells. Furthermore, Terminalia chebula (T. chebula), Berberis aristata (B. aristata), and Mucuna pruriens (M. pruriens) reduced HER2 expression in tested cell lines. In addition, an increased Bax/Bcl-2 ratio was observed after the treatment. A comparative proteomics study showed modulation in the proteome profile of breast cancer cells after treatment with T. chebula, B. aristata, Punica granatum, M. pruriens, and Acorus calamus. Metabolic profiling of lead plants revealed the existence of multiple anticancer compounds. Our study demonstrates the considerable potential of the mentioned plants as innovative therapies for HER2-positive breast cancer.

Intracranial Efficacy of Pyrotinib and Capecitabine Combination Therapy in HER2-Positive Breast Cancer with Brain Metastases.

Approximately 50% of patients diagnosed with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer (BC) are estimated to develop brain metastases (BMs). This study was aimed to assess the intracranial efficacy and survival benefits of pyrotinib and capecitabine combination therapy in the treatment of BMs in patients with HER2-positive BC. A total of 56 HER2-positive BC patients with BMs were treated with 400 mg pyrotinib once daily along with 1000 mg/m2 capecitabine twice daily for 14 days in 21-day cycles. The patients were allocated into three cohorts: (1) Cohort A composed of patients with newly diagnosed BMs without prior local radiotherapy, (2) Cohort B included patients with stable post-local radiotherapy, and (3) Cohort C composed of patients with progression following local radiotherapy. The primary endpoint was the intracranial objective response rate (CNS-ORR), while secondary endpoints included intracranial disease control rate (CNS-DCR), progression-free survival (PFS), overall survival (OS), safety, as well as QoL. The observed CNS-ORR CNS-ORR of 72.73% (95% CI 51.85-86.85%) in cohort A, 55% (95% CI 34.21-74.18%) in cohort B, and 42.86% (95% CI 21.38-67.41%) in cohort C. The mPFS was 11 months, 8.4 months, and 5.2 months in cohorts A, B, and C, respectively. Diarrhea, accounting for 23.21% of all the patients, was the most common grade 3/4 adverse event related with treatments (6/22 [27.3%] in cohort A, 4/20 [20.0%] in cohort B, and 3/14 [21.4%] in cohort C). However, there were no deaths related with treatments observed. Importantly, the QoL was efficiently maintained throughout the treatment duration. Pyrotinib and capecitabine combination therapy proved significant effectiveness as well as tolerability in treating HER2-positive BC with BMs, yielding satisfactory results, especially in radiotherapy-naive population.

Abstract IA21: Mechanisms of Resistance to HER2-Targeted Therapies in HER2-positive Breast Cancer

Abstract Recent advancements in HER2-targeted therapies for HER2+ BC have revolutionized patient outcome. Yet, intrinsic and acquired resistance, especially in the advanced setting remains a clinical challenge. In the era of precision oncology, better understanding of these mechanisms of resistance is key to identifying new strategies to overcome resistance and for developing personalized treatment approaches. Our recent studies suggest that a subset of HER2+ BCs, associated with high and homogeneous levels of HER2 gene amplification, protein, and activity, are addicted to HER2 and may therefore benefit from chemotherapy-sparing HER2-targeted regimens. However, even in such tumors, constitutive activation of the PI3K/AKT pathway due to deregulations in the downstream PI3K pathway can lead to resistance. In all HER2+ BCs, failure to achieve a comprehensive blockade of the HER receptor layer is one of the major mechanisms of resistance due to the functional redundancy of the HER receptors and compensatory signaling within the pathway. But, in some cases, effective inhibition of HER receptors might be challenged by molecular masking of the receptors (e.g., MUC4) or by epi/genetic or post-translational alterations in the receptors itself (e.g., HER2 L755S, p95HER2). Indeed, we recently reported that acquisition of HER2 L755S, either alone or together with PIK3CA mutation, and hyperactive EGFR signaling due to acquired EGFR amplification or excess HER ligands are associated with resistance to HER2-targeted therapy, especially tyrosine kinase inhibitors. Likewise, clinically, HER mutations have been reported to be further enriched in the metastatic vs. primary HER2+ tumors. When HER2 does remain sustainably inhibited by HER2-targeted agents, resistance may arise due to the emergence of alternative signaling pathways transmitting compensatory proliferative and survival signals, such as ER, receptor tyrosine kinases, or downstream/intracellular signaling. Further, the emergence of metabolic pathways as alternative pathways of resistance have also been documented. We recently reported the activation of the cholesterol biosynthetic mevalonate (MVA) pathway as an escape mechanism that provides alternative signals through the YAP/TAZ-mTORC1-survivin axis to evade HER2 blockade. This resistance could be overcome using MVA pathway inhibitors (e.g., statins). Additionally, activation of the cell cycle regulatory complex cyclin D1/CDK4 has been shown to be associated with HER2-targeted therapy resistance, which could be exploited as a potential therapeutic vulnerability by using CDK4/6 inhibitors. Finally, response to HER2-targeted therapy could potentially be also modulated by the tumor microenvironment itself, including components of the host immune system and extracellular matrix. Together, a better understanding of the underlying mechanisms of resistance in the context of tumor and host biology, and treatment setup is fundamental to develop new treatment strategies and to guide patient stratification for personalized treatments and improved patient outcomes. Citation Format: Jamunarani Veeraraghavan, Fu-Tien Liao, Lanfang Qin, Tia Gordon, Alekya Raghavan, Caroline Sabotta, Rachel Kaplan, Carolina Gutierrez, C. Kent Osborne, Mothaffar F. Rimawi, Rachel Schiff. Mechanisms of Resistance to HER2-Targeted Therapies in HER2-positive Breast Cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr IA21.

Neoadjuvant docetaxel/carboplatin/trastuzumab/pertuzumab (TCHP) in patients with HER2-positive early or locally advanced breast cancer

The widespread use of anti-HER2 drugs has fundamentally changed the fate of patients with both early and metastatic HER2-positive breast cancer (BC). The results of clinical studies demonstrate a significant increase in the frequency of achieving complete pathological response (pCR) and, as a consequence, improved survival rates when using the combination of docetaxel + carboplatin + trastuzumab + pertuzumab (TCHP) in neoadjuvant chemotherapy for HER2+ breast cancer, which is reflected in modern domestic and international guidelines. The purpose of this study was to evaluate the effectiveness of the TCHP regimen, as well as to identify independent clinical and morphological factors in achieving pCR. The study included 234 patients with HER2-positive breast cancer of stages II and III who received TCHP regimen in neoadjuvant setting, 233 were operated. The rate of achieving complete pathomorphological response (pCR, RCB 0) was 63 %, in the nonluminal HER2-positive subtype – 76 %, in the luminal HER2-positive subtype – 55 %. Predictors of pCR were the absence of hormonal receptors in the tumor (OR = 1.72; 95 % CI: 1.17–2.54; р = 0,01), as well as a high (>50 %) Ki-67 proliferation index (OR = 1.4; 95 % CI: 1.01–1.98; р = 0,05). The use of granulocyte colony stimulating factor as primary prevention has reduced the risk of febrile neutropenia and mucositis. Further observation of patients will allow us to evaluate the long-term results of neoadjuvant therapy for HER2-positive breast cancer using the TCHP regimen in our population.

Optimal choice of neoadjuvant therapy for HER2-positive breast cancer. Analysis of doctors’ preferences in Russian Federation

The development and introduction into widespread practice of anti-HER2 agents has changed the natural course of HER2-positive breast cancer, significantly increasing the chance of cure in early forms and significantly increasing the life expectancy of patients with metastatic disease. The results of clinical trials indicate a significant increase in the frequency of achieving complete pathological regress and improved survival rates when using the combination of trastuzumab + pertuzumab in neoadjuvant therapy for HER2-positive breast cancer, which is reflected in modern national and international guidelines. However, the use of drugs in real clinical practice is associated with a whole range of factors and may differ from standard recommendations. To understand the situation in the Russian Federation, a survey study ‘Therapy of HER2-positive breast cancer’ was conducted. 50 specialists – heads of drug therapy departments and/or their deputies who are directly involved in the development of a treatment plan for patients, were involved in the survey. It allows to reflect the preferences of leading chemotherapists regarding treatment strategies for patients with HER2-positive breast cancer in Russian Federation. This publication highlights the results of a survey on the prescription of neoadjuvant therapy for primary resectable and locally advanced unresectable HER2-positive breast cancer. Most experts prefer to use combinations with pertuzumab. In real clinical practice, 62% of patients receive dual anti-HER2 therapy. In the future, experts are ready to increase the percentage of prescribing pertuzumab for early HER2-positive breast cancer for more 16–20%. Based on the results of large randomized trials, this should improve long-term outcomes in one of the most aggressive forms of breast cancer.

Benefit of postoperative regional nodal irradiation in patients receiving preoperative systemic therapy with docetaxel/carboplatin/trastuzumab/pertuzumab for HER2-positive breast cancer

AimThe role of regional nodal irradiation (RNI) after preoperative systemic treatment (PST) with targeted therapy for HER2-positive breast cancer remains uncertain. This study aimed to investigate the impact of RNI on locoregional recurrence (LRR) and disease-free survival (DFS) outcomes after docetaxel/carboplatin/trastuzumab/pertuzumab (TCHP) for PST. MethodsWe retrospectively analyzed 255 patients who were treated with six cycles of TCHP between 2016 and 2019. The patients were divided into four groups based on clinical nodal involvement: group A, with no nodal disease; group B, with axillary lymph node (AXL) level I; group C, with AXL level I with II/III; and group D, with supraclavicular or internal mammary nodes. ResultsThe RNI group had more advanced nodal disease (C/D) than the no RNI group (56.9 % vs. 6.8 %). With a median follow-up of 51.3 months, there were two (0.8 %), three (1.2 %), and 15 (5.9 %) local, regional, and distant metastases, respectively. LRR did not differ significantly according to the RNI (2.6 % vs. 1.0 %, p = 0.651). Group D had the most frequent distant metastases (17.5 %; p = 0.005). The 4-year DFS rate was 92.7 %, and DFS did not improve significantly after RNI (p = 0.074). When stratified by clinical nodal groups and pathological axillary response, RNI had no effect on LRR/DFS outcomes. ConclusionWith a rare incidence of LRR, RNI did not significantly affect LRR or DFS in patients with HER2-positive breast cancer after with PST-TCHP. However, intensive systemic treatment is required for advanced diseases (C/D). Selective de-intensified RNI and intensified systemic treatment should be investigated in future studies.

Identification of potential inhibitors of HER2 targeting breast cancer—a structure-based drug design approach

Breast cancer is one of the most prevalent and malignant cancers in women. Most breast cancer patients show overexpression of the HER2 protein. The current study focused on identifying potent inhibitors of HER2 using a structure-based drug design approach. Prefiltered compounds from the Drugbank and the ZINC database were docked on HER2 protein using the FlexX docking tool of LeadIT. The docking study identified the 12 best molecules that interacted strongly with the active site of HER2 and also fulfilled the ADMET parameters. The complexes of these compounds with HER2 were further subjected to molecular dynamics simulation using GROMACS 2021.4, followed by the end-state MMGBSA binding energy calculations. The RMSD analysis was conducted to study the conformational changes, which revealed stability throughout the 100 ns simulation period. The local flexibility and dynamics of the simulated ligand-protein complexes were studied using RMSF analysis. The values of the radius of gyration were computed to analyze the compactness of HER2. The MMGBSA analysis provided insights into the energetic aspects of the system. The compound DB15187 emerged as the most potent candidate, showing MMGBSA-computed binding energy of −63.60 ± 3.39 kcal/mol. The study could help develop targeted therapies for HER2-positive breast cancer. Communicated by Ramaswamy H. Sarma

Oncodrivers for Immunotherapies in Triple-Negative Breast Cancer

Breast Cancer: Breast CancerMany advances have been made in therapies for patients having breast cancer driven by the estrogen receptor, the progesterone receptor, or the human epidermal growth factor 2 receptor (HER2). However, for patients with breast cancer not driven by any of these mechanisms, the disease, termed triple-negative, is characterized by an aggressive clinical course with poor patient outcomes. In a recent poster presented at the AACR Annual Meeting 2023, Saurabh K. Garg, PhD, a research scientist in the Czerniecki Lab at Moffitt Cancer Center, presented data from a retrospective study of triple-negative breast cancer patients who had undergone surgery at the Moffitt Cancer Center between January 2010 and February 2019 (Abstract 962). “Our team at the Czerniecki Lab and Moffitt Breast Clinic utilizes the power of dendritic cells, the primary antigen-presenting cells of the body, to present major histocompatibility complex Class II antigens from tumor-associated oncodrivers to prime the immune response against breast cancer,” Garg noted. “In our clinical trials, we are seeing a robust targeted response with dendritic cell-based therapies in HER2-positive breast cancer. This prompted us to identify immunogenic oncodrivers to develop targeted immunotherapies for triple-negative breast cancer, which accounts for 15-20 percent of breast cancer cases and presents as a more aggressive disease, with poor outcomes from current standard-of-care treatment options.” Regarding their study, Garg noted, “This is an institutional review board-approved, single institution retrospective study of 90 patients with triple-negative breast cancer who have undergone standard of care at Moffitt Cancer Center between January 2010 and February 2019. “Surgical biopsy tissue blocks of various stages, along with patient outcome data, were available to perform this downstream analysis,” he stated. “We utilized multiplex tissue microarray analyses, where multiple tissue core biopsies are arranged on a single slide for this immunofluorescence assay,” Garg explained. The tissue microarray analyses were divided into two panels: one for the oncodrivers and the other for tumor-infiltrating lymphocytes. In the first panel, “the expression of three oncodrivers: MET (MET proto-oncogene, receptor tyrosine kinase), EGFR (epidermal growth factor receptor), and HER3 (erb-b2 receptor tyrosine kinase 3) on surgical tissue blocks was scored by tumor microarray analysis,” Garg explained. “We also performed a second tissue microarray analysis to examine tumor-infiltrating lymphocytes expressing CD4, CD8, CD20, CD45, and CD56,” Garg noted about the second panel. “Subsequently, we correlated the expression of oncodrivers with patient outcome data and lymphocyte infiltration to catalog the immunogenicity of MET, EGFR, and HER-3 expression in triple-negative breast cancer settings.” Research Results When queried as to their findings, Dr. Garg answered, “The main finding of this study is that high expression of MET, EGFR, and HER3 correlated with higher occurrence of CD4, CD8, and CD45, respectively. This provided us invaluable information, indicating that these tumor-driving proteins have immunogenic potential to recruit lymphocytes to the tumor site, which could be harnessed to design targeted immunotherapies.” In addition, the elevated expression of HER3 was observed in the samples obtained from chemotherapy-treated patients, possibly implying a role in disease resistance. Interestingly, there was no correlation of prognoses with increased expression levels of the oncodrivers explored in this study. Another relevant observation was that better survival was observed in patients who had intermediate expression levels for EGFR with higher numbers of activated tumor-infiltrating lymphocytes. Future Directions “The present study provided a perfect segue for future targeted therapies that will be further developed and utilized in the clinic for triple-negative breast cancer patients,” Garg noted. “The identification of these immunogenic oncodrivers for triple-negative breast cancer will assist researchers at Moffitt and all over the world to target them with innovative therapies. “The next step in this study will be to identify the immunogenic regions of MET and EGFR proteins using our in-house peptide screening pipeline,” he stated. “This pipeline utilizes pre-clinical investigative tools to screen immunogenic major histocompatibility complex class II peptides to design dendritic cell-based cancer immunotherapies. Once identified and produced, we will test the efficacy of these treatments utilizing murine models of triple-negative breast cancer. “Furthermore, we have already performed peptide screening for the HER3 protein and have validated it in murine models of triple-negative breast cancer,” Garg said. “This HER3-based dendritic cell immunotherapy has been translated to a clinical trial, which is now underway at Moffitt for triple-negative breast cancer patients. Overall, successful completion of the pre-clinical translational research on all three triple-negative breast cancer oncodrivers will open the door for them to be incorporated in future dendritic cell immunotherapy clinical trials at the Moffitt Cancer Center with the potential of making significant improvements to the current triple-negative breast cancer standard of care and patient outcomes.” Richard Simoneaux is a contributing writer.

Trastuzumab potentiates doxorubicin-induced cardiotoxicity via activating the NLRP3 inflammasome in vivo and in vitro

Trastuzumab (Tra), the first humanized monoclonal antibody that targets human epidermal growth factor receptor 2 (HER2), is commonly used alongside doxorubicin (Dox) as a combination therapy in HER2-positive breast cancer. Unfortunately, this leads to a more severe cardiotoxicity than Dox alone. NLRP3 inflammasome is known to be involved in Dox-induced cardiotoxicity and multiple cardiovascular diseases. However, whether the NLRP3 inflammasome contributes to the synergistic cardiotoxicity of Tra has not been elucidated. In this study, primary neonatal rat cardiomyocyte (PNRC), H9c2 cells and mice were treated with Dox (15 mg/kg in mice or 1 μM in cardiomyocyte) or Tra (15.75 mg/kg in mice or 1 μM in cardiomyocyte), or Dox combined Tra as cardiotoxicity models to investigate this question. Our results demonstrated that Tra significantly potentiated Dox-induced cardiomyocyte apoptosis and cardiac dysfunction. These were accompanied by the increased expressions of NLRP3 inflammasome components (NLRP3, ASC and cleaved caspase-1), the secretion of IL-β and the pronounced production of ROS. Inhibiting the activation of NLRP3 inflammasome by NLRP3 silencing significantly reduced cell apoptosis and ROS production in Dox combined Tra-treated PNRC. Compared with the wild type mice, the systolic dysfunction, myocardial hypertrophy, cardiomyocyte apoptosis and oxidative stress induced by Dox combined Tra were alleviated in NLRP3 gene knockout mice. Our data revealed that the co-activation of NLRP3 inflammasome by Tra promoted the inflammation, oxidative stress and cardiomyocytes apoptosis in Dox combined Tra-induced cardiotoxicity model both in vivo and in vitro. Our results suggest that NLRP3 inhibition is a promising cardioprotective strategy in Dox/Tra combination therapy.

Role of plasma circulating HER2/EFTUD2 ratio in predicting pathological complete response (pCR) after neoadjuvant dual anti-HER2 therapy in HER2-positive breast cancer (HER2+ BC).

e12592 Background: Achieving pCR following neoadjuvant chemo and anti-HER2 therapy is associated with a significantly better survival in HER2+ BC. There is currently a lack of a robust biomarker to predict pCR in HER2+ BC. Using EFTUD2 as chromosome 17 reference probe, circulating HER2/EFTUD2 plasma DNA copy number ratio (H-ratio) detected by droplet digital PCR (ddPCR) was shown to have high concordance with the tumor HER2 status. We aim to evaluate whether the change in H-ratio is associated with response to neoadjuvant dual anti-HER2 therapy. Methods: We prospectively recruited patients with HER2+ BC who received neoadjuvant taxane, trastuzumab and pertuzumab followed by radical surgery from May 2019 to April 2022. Serial plasma samples (n = 49) were collected at pre-treatment (Tpre), at 4th cycle (Tmid) and at completion of neoadjuvant treatment (Tpost). H-ratio was determined in each plasma sample using droplet ddPCR (QX200 ddPCR system, Bio-rad). H-ratio responders were defined as patients having a declining Tpost H-ratio, whereas patients having a rising or persistent Tpost H-ratio were defined as H-ratio non-responders. The relationship between pCR, H-ratio and various clinicopathological characteristics were evaluated by Spearman’s correlation, Fisher’s exact test and Wilcoxon signed-rank test. Results: Eighteen clinical stage II or III HER2+ BC patients with a median age of 56 years old (range 33 - 71) were included. The median H-ratio at Tpre, Tmid and Tpost were 1.27, 1.12 and 1.10, respectively. Higher Tpre H-ratio was significantly associated with larger tumor size (p = 0.004) and higher tumor grade (G1-2 vs G3; median H-ratio 1.15 vs 1.78; p = 0.024). Six patients (33.3%) were H-ratio responders. Ten (55.6%) of 18 patients achieved pCR after completion of neoadjuvant treatment. The pCR rate in H-ratio responders was significantly higher than the H-ratio non-responders (100% vs. 36.4%; p = 0.017). In predicting pCR, H-ratio response outperformed hormonal receptor (HR) negativity (HR- vs HR+; 72.7% vs 28.6%; p = 0.088) or high tumor grade (G1-2 vs G3; 66.7% vs 33.3%; p = 0.201). There was no association between pCR and Tpre/Tmid/Tpost H-ratio. With a median follow up of 22.8 months (range 8.2 - 41.8), there were no relapse or death. Conclusions: A high pre-treatment plasma circulating HER2/EFTUD2 ratio is associated with large tumor size and high tumor grade in HER2+ BC. The decline of HER2/EFTUD2 ratio after neoadjuvant dual anti-HER2 therapy predicts pCR, and may serve as a potential biomarker for treatment de-escalation.

Resistance to anti-HER2 therapy associated with the TSC2 nonsynonymous variant c.4349 C > G (p.Pro1450Arg) is reversed by CDK4/6 inhibitor in HER2-positive breast cancer

HER2-positive breast cancer patients carrying the germline TSC2 nonsynonymous variant c.4349 C > G (p.Pro1450Arg) are resistant to anti-HER2 therapy. Multi-predictor in silico analysis reveals that this variant is deleterious. We explore the potential mechanism of this TSC2 variant and investigate methods for overcoming anti-HER2 resistance. TSC2 c.4349 C > G reverses the inhibitory effect on mTOR and downstream signaling by increasing TSC2 phosphorylation at Thr1462 and confers significant lapatinib resistance in vitro and in vivo. The combination of lapatinib and the CDK4/6 inhibitor palbociclib inhibits cyclin D1/CDK4/Rb alternative pathway and TSC2 phosphorylation, thereby partially attenuating mTOR activity and inducing TSC2-mutant cell blockage at G1/G0. In in vitro and xenograft models, palbociclib+lapatinib shows higher anti-tumor activity than monotherapy and overcomes the resistance of the TSC2 c.4349 C > G-related variant to anti-HER2 therapy. We reveal a new mechanism of resistance to anti-HER2 therapy and provide a strategy to increase the efficiency of anti-HER2 therapy in HER2-positive breast cancer.

Preclinical and Basic Research Strategies for Overcoming Resistance to Targeted Therapies in HER2-Positive Breast Cancer.

The amplification of epidermal growth factor receptor 2 (HER2) is associated with a poor prognosis and HER2 gene is overexpressed in approximately 15-30% of breast cancers. In HER2-positive breast cancer patients, HER2-targeted therapies improved clinical outcomes and survival rates. However, drug resistance to anti-HER2 drugs is almost unavoidable, leaving some patients with an unmet need for better prognoses. Therefore, exploring strategies to delay or revert drug resistance is urgent. In recent years, new targets and regimens have emerged continuously. This review discusses the fundamental mechanisms of drug resistance in the targeted therapies of HER2-positive breast cancer and summarizes recent research progress in this field, including preclinical and basic research studies.

Interaction between Radiation Therapy and Targeted Therapies in HER2-Positive Breast Cancer: Literature Review, Levels of Evidence for Safety and Recommendations for Optimal Treatment Sequence.

Purpose: Over the past twenty years, anti-HER2 targeted therapies have proven to be a revolution in the management of human epidermal growth receptor 2 (HER2)-positive breast cancers. Anti-HER2 therapies administered alone or in combination with chemotherapy have been specifically studied. Unfortunately, the safety of anti-HER2 therapies in combination with radiation remains largely unknown. Thus, we propose a literature review of the risks and safety of combining radiotherapy with anti-HER2 therapies. We will focus on the benefit/risk rationale and try to understand the risk of toxicity in early-stage and advanced breast cancer. Methods: Research was carried out on the following databases: PubMed, EMBASE, ClinicalTrial.gov, Medline, and Web of Science for the terms "radiotherapy", "radiation therapy", "radiosurgery", "local ablative therapy", and "stereotactic", combined with "trastuzumab", "pertuzumab", "trastuzumab emtansine", "TDM-1", "T-Dxd", "trastuzumab deruxtecan", "tucatinib", "lapatinib", "immune checkpoint inhibitors", "atezolizumab", "pembrolizumab", "nivolumab", "E75 vaccine", "interferon", "anti-IL-2", "anti-IL 12", and "ADC". Results: Association of radiation and monoclonal antibodies such as trastuzumab and pertuzumab (with limited data) seems to be safe, with no excess risk of toxicity. Preliminary data with radiation and of antibody-drug conjugate of trastuzumab combined cytotoxic (trastuzumab emtansine, trastuzumab deruxtecan), given the underlying mechanism of action, suggest that one must be particularly cautious with the association. The safety of the combination of a tyrosine kinase inhibitor (lapatinib, tucatinib) and radiation remains under-studied. The available evidence suggests that checkpoint inhibitors can be safely administrated with radiation. Conclusions: HER2-targeting monoclonal antibodies and checkpoint inhibitors can be combined with radiation, apparently with no excess toxicities. Caution is required when associating radiation with TKI and antibody drugs, considering the limited evidence.

Landscape of neoadjuvant therapy in HER2-positive breast cancer: a systematic review and network meta-analysis

BackgroundThe recommended preoperative approach for HER2-positive breast cancer is unclear. We aimed to investigate the following: i) what is the optimal neoadjuvant regimen and ii) whether anthracyclines could be excluded. MethodsA systematic literature search in Medline, Embase and Web of Science databases was performed. Studies had to satisfy the following criteria: i) randomised controlled trials (RCTs), ii) enroled patients treated preoperatively for HER2-positive BC (breast cancer), iii) at least one treatment group received an anti-HER2 agent, iv) available information of any efficacy end-point and v) published in English. A network meta-analysis with a frequentist framework using random-effects model was used to pool direct and indirect evidence. Pathologic complete response (pCR), event-free survival (EFS) and overall survival (OS) were the efficacy end-points of interest, and selected safety end-points were also analysed. ResultsA total of 11,049 patients with HER2-positive BC (46 RCTs) were included in the network meta-analysis, and 32 different regimens were evaluated. Dual anti-HER2-therapy, with pertuzumab or tyrosine kinase inhibitors, combined with chemotherapy was significantly superior to trastuzumab and chemotherapy in terms of pCR, EFS and OS. However, a higher risk of cardiotoxicity was observed with dual anti-HER2-therapy. Anthracycline-based chemotherapy was not associated with better efficacy outcomes in comparison with non-anthracycline-based chemotherapy. In anthracycline-free regimens, the addition of carboplatin presented numerically better efficacy outcomes. ConclusionDual HER2 blockade with chemotherapy is the recommended choice as neoadjuvant therapy for HER2-positive breast cancer, preferably by omitting anthracyclines in favour of carboplatin.

131I-Labeled Anti-HER2 Nanobody for Targeted Radionuclide Therapy of HER2-Positive Breast Cancer.

The unique structure of nanobodies is advantageous for the development of radiopharmaceuticals for nuclear medicine. Nanobodies targeted to human epidermal growth factor receptor 2 (HER2) can be used as tools for the imaging and therapy of HER2-overexpressing tumors. In this study, we aimed to describe the generation of a 131I-labeled anti-HER2 nanobody as a targeted radionuclide therapy (TRNT) agent for HER2-positive breast cancer. The anti-HER2 nanobody NM-02 was labeled with 131I using the iodogen method, and its radiochemical purity and stability in vitro were assessed. The pharmacokinetic profile of 131I-NM-02 was investigated in normal mice. Tumor accumulation, biodistribution, and therapeutic potential of 131I-NM-02 were evaluated in HER2-positive SKBR3 xenografts; HER2-negative MB-MDA-231 xenografts were used as the control group. 131I-NM-02 could be readily prepared with satisfactory radiochemical purity and stability in vitro. Apparent tumor uptake was observed in HER2-positive tumor-bearing mice with rapid blood clearance and favorable biodistribution. 131I-NM-02 could significantly inhibit tumor growth and extend the life of these mice with good organ compatibility. Negligible tumor accumulation and inhibitory effects of 131I-NM-02 were observed in the negative control group. 131I-NM-02 has the potential to be explored as a novel tool for TRNT of HER2-positive breast cancer.

Emerging Targeted Therapies for HER2-Positive Breast Cancer.

Breast cancer is the most common cancer in women and the leading cause of death. HER2 overexpression is found in approximately 20% of breast cancers and is associated with a poor prognosis and a shorter overall survival. Tratuzumab, a monoclonal antibody directed against the HER2 receptor, is the standard of care treatment. However, a third of the patients do not respond to therapy. Given the high rate of resistance, other HER2-targeted strategies have been developed, including monoclonal antibodies such as pertuzumab and margetuximab, trastuzumab-based antibody drug conjugates such as trastuzumab-emtansine (T-DM1) and trastuzumab-deruxtecan (T-DXd), and tyrosine kinase inhibitors like lapatinib and tucatinib, among others. Moreover, T-DXd has proven to be of use in the HER2-low subtype, which suggests that other HER2-targeted therapies could be successful in this recently defined new breast cancer subclassification. When patients progress to multiple strategies, there are several HER2-targeted therapies available; however, treatment options are limited, and the potential combination with other drugs, immune checkpoint inhibitors, CAR-T cells, CAR-NK, CAR-M, and vaccines is an interesting and appealing field that is still in development. In this review, we will discuss the highlights and pitfalls of the different HER2-targeted therapies and potential combinations to overcome metastatic disease and resistance to therapy.

Abstract P1-04-16: A nomogram based on clinicopathologic factors and pretreatment systemic inflammation response index to predict pathological complete response of neoadjuvant systemic therapy in HER2-positive breast cancer: A dual-center study

Abstract Purpose: Multiple pretreatment systemic inflammatory markers (SIMs) have been reported as predictors of pathological complete response (pCR) after neoadjuvant systemic therapy (NST) in patients with breast cancer (BC). However, the most significant SIM remains to be conclusively identified, and variations among different molecular subtypes remain unknown. The objective of the study was to identify the most significant SIM in patients with human epidermal growth factor receptor 2 (HER2) positive BC, and to construct a pCR-predictive nomogram combining it with other clinicopathological factors. Methods: We retrospectively reviewed the findings for 240 patients with stage I–III HER2-positive BC who underwent NST and subsequent surgery at Kaohsiung and Taichung Veterans General Hospital from 2011 to 2021. Clinicopathological factors were analyzed by stepwise logistic regression with forward selection. The data were used to construct a nomogram plot for determining the probability of pCR. Results: Among the pretreatment SIMs, only SIRI was significantly related to pCR, with an optimal cutoff value of 1.27 × 10^9/L. Stepwise logistic analyses indicated that clinical N stage, HER2 immunohistochemistry (IHC) score, hormone receptor status, targeted therapy regimen, and SIRI were independent predictors of pCR, with an area under the curve (AUC) of 0.722. The Hosmer–Lemeshow test and calibration curve revealed that the predictive ability was a good fit to actual observations. A nomogram was constructed based on the logistic model. Conclusions: Pretreatment SIRI < 1.27 is predictive of pCR in HER2-positive BC. Our nomogram could efficiently predict pCR and facilitate clinical decision-making before neoadjuvant treatment. Univariable and multivariable analyses for predictive factors of pathological complete response of neoadjuvant systemic therapy in HER2-positive breast cancer Citation Format: Hong Yu Wu, Yen-Dun Tzeng, Jie Ru Yang, Chih Chiang Hung. A nomogram based on clinicopathologic factors and pretreatment systemic inflammation response index to predict pathological complete response of neoadjuvant systemic therapy in HER2-positive breast cancer: A dual-center study [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-04-16.