Trastuzumab emtansine plus atezolizumab versus trastuzumab emtansine plus placebo in previously treated, HER2-positive advanced breast cancer (KATE2): a phase 2, multicentre, randomised, double-blind trial

Progress of PD-1/PD-L1 inhibitor combination therapy in immune treatment for HER2-positive tumors

BACKGROUND

Patients with HER2-positive cancers often face a poor prognosis, and treatment regimens containing anti-HER2 have become the first-line treatment options for breast and gastric cancers. However, these approaches are faced with significant challenges in terms of drug resistance. Hence, it is crucial to explore precise treatment strategies aimed at improving survival outcomes.

ADVANCEMENTS IN TREATMENT

Over the past few years, there has been rapid advancement in the realm of tumor therapy, particularly with the swift progress of immune checkpoint inhibitors, including PD-1/PD-L1 inhibitors. They exert anti-tumor effects by disrupting immune-suppressive factors within the tumor microenvironment. However, monotherapy with PD-1/PD-L1 inhibitors has several limitations. Consequently, numerous studies have explored combinatorial immunotherapeutic strategies and demonstrated highly promising avenues of development.

OBJECTIVE

This article aims to review the clinical trials investigating PD-1/PD-L1 inhibitor combination therapy for HER2-positive tumors. Additionally, it provides a summary of ongoing trials evaluating the efficacy and safety of these combined treatments, with the intention of furnishing valuable insights for the clinical management of HER2-positive cancer.

CONCLUSION

Combinatorial immunotherapeutic strategies involving PD-1/PD-L1 inhibitors hold considerable promise in the treatment of HER2-positive tumors. Continued research efforts and clinical trials are warranted to elucidate optimal treatment regimens that maximize therapeutic benefits while minimizing adverse effects.

Risk of interstitial lung disease with the use of programmed cell death 1 (PD-1) inhibitor compared with programmed cell death ligand 1 (PD-L1) inhibitor in patients with breast cancer: A systematic review and meta-analysis

Background

Programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1) inhibitors have become integral elements within the current landscape of breast cancer treatment modalities; however, they are associated with interstitial lung disease (ILD), which is rare but potentially fatal. Notably, only a few studies have compared the difference in ILD incidence between PD-1 and PD-L1 inhibitors. Therefore, this study aimed to assess the discrepancies regarding ILD risk between the two immune checkpoint inhibitors. We also reported three cases of ILD after PD-1 inhibitor treatment.

Methods

We comprehensively searched PubMed, EMBASE, and the Cochrane Library to identify clinical trials that investigated PD-1/PD-L1 inhibitor treatment for patients with breast cancer. Pooled overall estimates of incidence and risk ratio (RR) were calculated with a 95% confidence interval (CI), and a mirror group analysis was performed using eligible studies.

Results

This meta-analysis included 29 studies with 4639 patients who received PD-1/PD-L1 inhibitor treatment. A higher ILD incidence was observed among 2508 patients treated with PD-1 inhibitors than among 2131 patients treated with PD-L1 inhibitors (0.05 vs. 0.02). The mirror group analysis further revealed a higher ILD event risk in patients treated with PD-1 inhibitors than in those treated with PD-L1 inhibitors (RR = 2.34, 95% CI, 1.13-4.82, P = 0.02).

Conclusion

Our findings suggest a greater risk of ILD with PD-1 inhibitors than with PD-L1 inhibitors. These findings are instrumental for clinicians in treatment deliberations, and the adoption of more structured diagnostic approaches and management protocols is necessary to mitigate the risk of ILD.

Incidence of antibody-drug conjugate-related fatigue in patients with breast cancer: A systematic review and meta-analysis

BACKGROUND

Numerous studies have reported the efficacy of antibody-drug conjugates (ADCs) for treating breast cancer. However, during cytotoxic drug treatment, long-term disabling fatigue is common. Moreover, studies in the relevant literature have indicated that fatigue can significantly increase the incidence of depression and sleep disorders. Therefore, this meta-analysis aims to evaluate the incidence of fatigue in breast cancer survivors treated with ADCs.

METHODS

PubMed, EMBASE, Web of Science, and Cochrane Library databases were systematically searched for articles and conference abstracts published before March 16, 2023. Further, two authors independently extracted data from the included studies. The primary outcome of this study was the incidence of all-grade fatigue caused by the use of ADCs in patients with breast cancer. Finally, a random-effects model was used to calculate the incidence and 95% confidence intervals (CIs) of the outcome.

RESULTS

Overall, 7963 patients from 31 studies were included in this meta-analysis to assess the incidence of fatigue caused by the use of approved and marketed ADCs in patients with breast cancer. Notably, the incidence of all-grade fatigue during ADC monotherapy was 39.84% (95% CI, 35.09%-44.69%). In subgroup analyses, among ADCs, the incidence of trastuzumab deruxtecan-induced fatigue was the highest, with an all-grade fatigue incidence of 47.05% (95% CI, 42.38%-51.75%). Meanwhile, the incidence of trastuzumab emtansine (T-DM1)-induced all-grade fatigue was 35.17% (95% CI, 28.87%-41.74%), which was the lowest among ADCs. Further, the incidence of all-grade fatigue due to sacituzumab govitecan was 42.82% (95% CI, 34.54%-51.32%), which was higher than that due to T-DM1. Moreover, the incidence of fatigue was higher with T-DM1 combination therapy than with monotherapy.

CONCLUSIONS

Clinicians have highlighted the high incidence of ADC-related fatigue and its negative impact on patients' physical and mental health, making fatigue an important research variable. The results of this study will further contribute to a comprehensive understanding of ADCs, which have some clinical importance and are of great benefit to patients with breast cancer.

Tailoring Neoadjuvant Therapy in Human Epidermal Growth Factor Receptor 2-Positive Early Breast Cancer: Recent Advances and Strategies

Neoadjuvant HER2 Therapy: Beyond one-size-fits-all.

Drug conjugates for the treatment of lung cancer: from drug discovery to clinical practice

A drug conjugate consists of a cytotoxic drug bound via a linker to a targeted ligand, allowing the targeted delivery of the drug to one or more tumor sites. This approach simultaneously reduces drug toxicity and increases efficacy, with a powerful combination of efficient killing and precise targeting. Antibody‒drug conjugates (ADCs) are the best-known type of drug conjugate, combining the specificity of antibodies with the cytotoxicity of chemotherapeutic drugs to reduce adverse reactions by preferentially targeting the payload to the tumor. The structure of ADCs has also provided inspiration for the development of additional drug conjugates. In recent years, drug conjugates such as ADCs, peptide‒drug conjugates (PDCs) and radionuclide drug conjugates (RDCs) have been approved by the Food and Drug Administration (FDA). The scope and application of drug conjugates have been expanding, including combination therapy and precise drug delivery, and a variety of new conjugation technology concepts have emerged. Additionally, new conjugation technology-based drugs have been developed in industry. In addition to chemotherapy, targeted therapy and immunotherapy, drug conjugate therapy has undergone continuous development and made significant progress in treating lung cancer in recent years, offering a promising strategy for the treatment of this disease. In this review, we discuss recent advances in the use of drug conjugates for lung cancer treatment, including structure-based drug design, mechanisms of action, clinical trials, and side effects. Furthermore, challenges, potential approaches and future prospects are presented.

Management of patients with advanced-stage HER2-positive breast cancer: current evidence and future perspectives

Amplification and/or overexpression of ERBB2, the gene encoding HER2, can be found in 15-20% of invasive breast cancers and is associated with an aggressive phenotype and poor clinical outcomes. Relentless research efforts in molecular biology and drug development have led to the implementation of several HER2-targeted therapies, including monoclonal antibodies, tyrosine-kinase inhibitors and antibody-drug conjugates, constituting one of the best examples of bench-to-bedside translation in oncology. Each individual drug class has improved patient outcomes and, importantly, the combinatorial and sequential use of different HER2-targeted therapies has increased cure rates in the early stage disease setting and substantially prolonged survival for patients with advanced-stage disease. In this Review, we describe key steps in the development of the modern paradigm for the treatment of HER2-positive advanced-stage breast cancer, including selecting and sequencing new-generation HER2-targeted therapies, and summarize efficacy and safety outcomes from pivotal studies. We then outline the factors that are currently known to be related to resistance to HER2-targeted therapies, such as HER2 intratumoural heterogeneity, activation of alternative signalling pathways and immune escape mechanisms, as well as potential strategies that might be used in the future to overcome this resistance and further improve patient outcomes.

Lung toxicity induced by anti-HER2 antibody - drug conjugates for breast cancer

Human epidermal growth factor receptor 2 (HER2) serves as both a prognostic indicator and a therapeutic target for breast cancer. Therefore, anti-HER2 therapy plays a crucial role in the treatment of HER2-positive cancer. Antibody-drug conjugates (ADCs) are composed of a monoclonal antibody, a chemical linker and a payload, wherein their aim is to reduce the toxicity associated with chemotherapy drugs by utilizing specific antibodies. Among the anti-HER2 ADCs currently approved for clinical use, trastuzumab emtansine(T-DM1) and trastuzumab deruxtecan (T-Dxd) have demonstrated remarkable efficacy in treating HER2-positive breast cancer. However, it is essential to emphasize the occurrence of lung toxicity during the treatment process, which can be life-threatening. In this review, we provide an overview of the new epidemiological features associated with interstitial lung disease (ILD) related to anti-HER2 ADCs in breast cancer. We also summarize the potential pathogenesis and explore the diagnosis and treatment strategies within this field.

Standard-of-Care Treatment for HER2+ Metastatic Breast Cancer and Emerging Therapeutic Options

Prior to the advent of the HER2-targeted monoclonal antibody trastuzumab, HER2+ breast cancer (BC) was considered an aggressive disease with a poor prognosis. Over the past 25 years, innovations in molecular biology, pathology, and early therapeutics have transformed the treatment landscape. With the advent of multiple HER2-directed therapies, there have been immense improvements in oncological outcomes in both adjuvant and metastatic settings. Currently, 8 HER2-targeted therapies are approved by the Food and Drug Administration (FDA) for the treatment of early-stage and/or advanced/metastatic disease. Nonetheless, approximately 25% of patients develop recurrent disease or metastasis after HER2-targeted therapy and most patients with HER2+ metastatic breast cancer (MBC) die from their disease. Given the many mechanisms of resistance to HER2-directed therapy, there is a pressing need to further personalize care for patients with HER2+ MBC, by the identification of reliable predictive biomarkers, and the development of novel therapies and combination regimens to overcome therapeutic resistance. Of particular interest are established and novel antibody-drug conjugates, as well as other novel therapeutics and multifaceted approaches to harness the immune system (checkpoint inhibitors, bispecific antibodies, and vaccine therapy). Herein, we discuss standard-of-care treatment of HER2+ MBC, including the management of breast cancer brain metastases (BCBM). Furthermore, we highlight novel treatment approaches for HER2+ MBC, including endeavors to personalize therapy, and discuss ongoing controversies and challenges.

Update on current and new potential immunotherapies in breast cancer, from bench to bedside

Impressive advances have been seen in cancer immunotherapy during the last years. Although breast cancer (BC) has been long considered as non-immunogenic, immunotherapy for the treatment of BC is now emerging as a new promising therapeutic approach with considerable potential. This is supported by a plethora of completed and ongoing preclinical and clinical studies in various types of immunotherapies. However, a significant gap between clinical oncology and basic cancer research impairs the understanding of cancer immunology and immunotherapy, hampering cancer therapy research and development. To exploit the accumulating available data in an optimal way, both fundamental mechanisms at play in BC immunotherapy and its clinical pitfalls must be integrated. Then, clinical trials must be critically designed with appropriate combinations of conventional and immunotherapeutic strategies. While there is room for major improvement, this updated review details the immunotherapeutic tools available to date, from bench to bedside, in the hope that this will lead to rethinking and optimizing standards of care for BC patients.

Endothelial cells in tumor microenvironment: insights and perspectives

The tumor microenvironment is a highly complex and dynamic mixture of cell types, including tumor, immune and endothelial cells (ECs), soluble factors (cytokines, chemokines, and growth factors), blood vessels and extracellular matrix. Within this complex network, ECs are not only relevant for controlling blood fluidity and permeability, and orchestrating tumor angiogenesis but also for regulating the antitumor immune response. Lining the luminal side of vessels, ECs check the passage of molecules into the tumor compartment, regulate cellular transmigration, and interact with both circulating pathogens and innate and adaptive immune cells. Thus, they represent a first-line defense system that participates in immune responses. Tumor-associated ECs are involved in T cell priming, activation, and proliferation by acting as semi-professional antigen presenting cells. Thus, targeting ECs may assist in improving antitumor immune cell functions. Moreover, tumor-associated ECs contribute to the development at the tumor site of tertiary lymphoid structures, which have recently been associated with enhanced response to immune checkpoint inhibitors (ICI). When compared to normal ECs, tumor-associated ECs are abnormal in terms of phenotype, genetic expression profile, and functions. They are characterized by high proliferative potential and the ability to activate immunosuppressive mechanisms that support tumor progression and metastatic dissemination. A complete phenotypic and functional characterization of tumor-associated ECs could be helpful to clarify their complex role within the tumor microenvironment and to identify EC specific drug targets to improve cancer therapy. The emerging therapeutic strategies based on the combination of anti-angiogenic treatments with immunotherapy strategies, including ICI, CAR T cells and bispecific antibodies aim to impact both ECs and immune cells to block angiogenesis and at the same time to increase recruitment and activation of effector cells within the tumor.

Quantitative systems pharmacology modeling of HER2-positive metastatic breast cancer for translational efficacy evaluation and combination assessment across therapeutic modalities

HER2-positive (HER2+) metastatic breast cancer (mBC) is highly aggressive and a major threat to human health. Despite the significant improvement in patients' prognosis given the drug development efforts during the past several decades, many clinical questions still remain to be addressed such as efficacy when combining different therapeutic modalities, best treatment sequences, interindividual variability as well as resistance and potential coping strategies. To better answer these questions, we developed a mechanistic quantitative systems pharmacology model of the pathophysiology of HER2+ mBC that was extensively calibrated and validated against multiscale data to quantitatively predict and characterize the signal transduction and preclinical tumor growth kinetics under different therapeutic interventions. Focusing on the second-line treatment for HER2+ mBC, e.g., antibody-drug conjugates (ADC), small molecule inhibitors/TKI and chemotherapy, the model accurately predicted the efficacy of various drug combinations and dosing regimens at the in vitro and in vivo levels. Sensitivity analyses and subsequent heterogeneous phenotype simulations revealed important insights into the design of new drug combinations to effectively overcome various resistance scenarios in HER2+ mBC treatments. In addition, the model predicted a better efficacy of the new TKI plus ADC combination which can potentially reduce drug dosage and toxicity, while it also shed light on the optimal treatment ordering of ADC versus TKI plus capecitabine regimens, and these findings were validated by new in vivo experiments. Our model is the first that mechanistically integrates multiple key drug modalities in HER2+ mBC research and it can serve as a high-throughput computational platform to guide future model-informed drug development and clinical translation.

Advances in the study of marketed antibody-drug Conjugates (ADCs) for the treatment of breast cancer

Breast cancer continues to have a high incidence rate among female malignancies. Despite significant advancements in treatment modalities, the heterogeneous nature of breast cancer and its resistance to various therapeutic approaches pose considerable challenges. Antibody-drug conjugates (ADCs) effectively merge the specificity of antibodies with the cytotoxicity of chemotherapeutic agents, offering a novel strategy for precision treatment of breast cancer. Notably, trastuzumab emtansine (T-DM1) has provided a new therapeutic option for HER2-positive breast cancer patients globally, especially those resistant to conventional treatments. The development of trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG) has further broadened the applicability of ADCs in breast cancer therapy, presenting new hopes for patients with low HER2 expression and triple-negative breast cancer. However, the application of ADCs presents certain challenges. For instance, their treatment may lead to adverse reactions such as interstitial lung disease, thrombocytopenia, and diarrhea. Moreover, prolonged treatment could result in ADCs resistance, complicating the therapeutic process. Economically, the high costs of ADCs might hinder their accessibility in low-income regions. This article reviews the structure, mechanism of action, and clinical trials of commercially available ADCs for breast cancer treatment, with a focus on the clinical trials of the three drugs, aiming to provide insights for clinical applications and future research.

Molecular Targeting of the Human Epidermal Growth Factor Receptor-2 (HER2) Genes across Various Cancers

Human epidermal growth factor receptor 2 (HER2) belongs to the ErbB family, a group of four transmembrane glycoproteins with tyrosine kinase activity, all structurally related to epidermal growth factor receptor (EGFR). These tyrosine kinases are involved in the transmission of cellular signals controlling normal cell growth and differentiation. If this transmission goes awry, it can lead to dysregulated growth of the cell. HER2 specifically can be implicated in the pathogenesis of at least eight malignancies. HER2 positivity quickly became a well-characterized indicator of aggressiveness and poor prognosis, with high rates of disease progression and mortality. After realizing the implication of HER2, it first became investigated as a target for treatment in breast cancer, and later expanded to areas of research in other cancer types. To this day, the most therapeutic advancements of anti-HER2 therapy have been in breast cancer; however, there have been strong advancements made in the incorporation of anti-HER2 therapy in other cancer types as well. This comprehensive review dissects HER2 to its core, incorporating the most up to date information. The topics touched upon are discussed in detail and up to 200 published sources from the most highly recognized journals have been integrated. The importance of knowing about HER2 is exemplified by the groundbreaking advancements that have been made, and the change in treatment plans it has brought to the oncological world in the last twenty years. Since its groundbreaking discovery there have been significant breakthroughs in knowledge regarding the actual receptor, the receptors biology, its mechanism of action, and advancements in tests to detect HER2 and significant strides on how to best incorporate targeted treatment. Due to the success of this field thus far, the review concludes by discussing the future of novel anti-HER2 therapy currently in development that everyone should be aware of.

Endocrine therapy plus HER2-targeted therapy, another favorable option for HR+/HER2+ advanced breast cancer patients

Advanced breast cancer (ABC) that is positive for hormone receptors (HRs) and human epidermal growth factor receptor 2 (HER2) is a cancer subtype with distinctive characteristics. The primary treatment guidelines suggest that a combination therapy comprising anti-HER2 therapy and chemotherapy should be administered as the initial treatment for HR-positive/ HER2-positive (HR+/HER2+) ABC. However, crosstalk between the HR and HER2 pathways can partially account for the resistance of HR+/HER2+ disease to HER2-targeted therapy. This, in turn, provides a rationale for the concomitant administration of HER2-targeted therapy and endocrine therapy (ET). Many clinical studies have confirmed that the combination of HER2-targeted therapy and ET as a first-line treatment is not inferior to the combination of HER2-targeted therapy and chemotherapy, and support its use as a first-line treatment choice for HR+/HER2+ ABC. Other drugs, such as antibody-drug conjugates, cyclin-dependent kinase 4/6 inhibitors, phosphatidylinositol 3-kinase-protein kinase B (AKT)-mammalian target of rapamycin inhibitors, and programmed cell death protein 1 or programmed cell death ligand 1 inhibitors, may also improve the prognosis of patients with breast cancer by blocking signaling pathways associated with tumor proliferation and break new ground for the treatment of HR+/HER2+ ABC.

The promise and challenges of combination therapies with antibody-drug conjugates in solid tumors

Antibody-drug conjugates (ADCs) represent an important class of cancer therapies that have revolutionized the treatment paradigm of solid tumors. To date, many ongoing studies of ADC combinations with a variety of anticancer drugs, encompassing chemotherapy, molecularly targeted agents, and immunotherapy, are being rigorously conducted in both preclinical studies and clinical trial settings. Nevertheless, combination therapy does not always guarantee a synergistic or additive effect and may entail overlapping toxicity risks. Therefore, understanding the current status and underlying mechanisms of ADC combination therapy is urgently required. This comprehensive review analyzes existing evidence concerning the additive or synergistic effect of ADCs with other classes of oncology medicines. Here, we discuss the biological mechanisms of different ADC combination therapy strategies, provide prominent examples, and assess their benefits and challenges. Finally, we discuss future opportunities for ADC combination therapy in clinical practice.

An overview of the therapeutic strategies for neoplastic meningitis due to breast cancer: when and why?

INTRODUCTION

Neoplastic meningitis (NM), also known as leptomeningeal carcinomatosis, is characterized by the infiltration of tumor cells into the meninges, and poses a significant therapeutic challenge owing to its aggressive nature and limited treatment options. Breast cancer is a common cause of NM among solid tumors, further highlighting the urgent need to explore effective therapeutic strategies. This review aims to provide insights into the evolving landscape of NM therapy in breast cancer by collating existing research, evaluating current treatments, and identifying potential emerging therapeutic options.

AREAS COVERED

This review explores the clinical features, therapeutic strategies, recent advances, and challenges of managing NM in patients with breast cancer. Its management includes multimodal strategies, including systemic and intrathecal chemotherapy, radiation therapy, and supportive care. This review also emphasizes targeted drug options and optimal drug concentrations, and discusses emerging therapies. Additionally, it highlights the variability in treatment outcomes and the potential of combination regimens to effectively manage NM in breast cancer.

EXPERT OPINION

Challenges in treating NM include debates over clinical trial end points and the management of adverse effects. Drug resistance and low response rates are significant hurdles, particularly inHER2-negative breast cancer. The development of more precise and cost-effective medications with improved selectivity is crucial. Additionally, global efforts are needed for infrastructure development and cancer control considering the diverse nature of the disease.

Systemic Therapies for HER2-Positive Advanced Breast Cancer

Despite recent advances, HER2-positive advanced breast cancer (ABC) remains a largely incurable disease, with resistance to conventional anti-HER2 drugs ultimately unavoidable for all but a small minority of patients who achieve an enduring remission and possibly cure. Over the past two decades, significant advances in our understanding of the underlying molecular mechanisms of HER2-driven oncogenesis have translated into pharmaceutical advances, with the developing of increasingly sophisticated therapies directed against HER2. These include novel, more potent selective HER2 tyrosine kinase inhibitors (TKIs); new anti-HER2 antibody-drug conjugates; and dual epitope targeting antibodies, with more advanced pharmacological properties and higher affinity. With the introduction of adjuvant T-DM1 for incomplete responders to neoadjuvant therapy, fewer patients are relapsing, but for those who do relapse, disease that may be resistant to standard first- and second-line therapies requires new approaches. Furthermore, the risk of CNS relapse has not been abrogated by current (neo)adjuvant strategies; therefore, current research efforts are being directed towards this challenging site of metastatic disease. In this article, we review the currently available clinical data informing the effective management of HER2-positive breast cancer beyond standard first-line therapy with pertuzumab, trastuzumab, and taxanes, and the management of relapse in patients who have already been exposed to both these agents and T-DM1 for early breast cancer (EBC). We additionally discuss novel anti-HER2 targeted agents and combinations in clinical trials, which may be integrated into standard treatment paradigms in the future.

Evaluation of tumor-infiltrating lymphocytes, PD-L1, and PIK3CA mutations and association with prognosis in HER2-positive early stage breast cancer

BACKGROUND

Tumor-infiltrating lymphocytes (TILs) have predictive and prognostic potential in HER2-positive breast cancer (HER2+ BC). Programmed death-ligand 1 (PD-L1) is an immune checkpoint protein, with important roles in the tumor microenvironment, possibly in both tumor and immune cells (ICs), providing rationale for targeting with immune-checkpoint therapy. PIK3CA mutations are oncogenic, activating mutations, which are also of relevance in breast cancer. Herein, we investigate the frequency of TILs, PD-L1 and PIK3CA mutations, and whether these factors influence outcome, in early HER2+ BC.

MATERIALS AND METHODS

Stromal TILs (sTILs) and PD-L1 expressions were assessed using full tumor-sections and TMA, respectively, from 236 patients with HER2+ BC. TILs were assessed, according to a standardized method, as continuous measurement and according to three predefined categories: low (0-10%), intermediate (11-59%), and high (60-100%). PD-L1 immunohistochemistry (Ventana SP263) was evaluated and positivity defined as ≥1% expression in tumor and ICs. PIK3CA mutations (exons 9 and 20) were determined by pyrosequencing.

RESULTS

Fourteen percent of patients had high sTILs and 25% had a PIK3CA mutation. PD-L1 expression was more frequent in ICs (68%) than tumor cells (24%). Patients with low sTILs had a significantly worse overall survival (multivariate: HR 2.80; 95% CI 1.36-5.78; p = .02).

DISCUSSION

Patients with low sTILs had a significantly poorer survival, despite adequate treatment with adjuvant therapy.

Clinical characteristics and treatment outcomes of HER2 mutation and HER2 fusion in 22 patients with advanced breast cancer

BACKGROUND

The clinical characteristics and efficacy of human epidermal growth factor receptor-2 (HER-2)-directed agents against HER2 mutations and HER2 fusions in breast cancer are obscure due to their low frequency.

METHODS

We conducted a retrospective study in patients with advanced breast cancer harboring HER2 mutations and/or HER2 fusions between January 1, 2017 and January 1, 2021.

RESULTS

Among a total of 22 patients, 17 HER2 mutations were detected, including L755S, S310F, R100=, V777L, R897W, T862A, 440-17C > G, H878Y, V842I, 73 + 9G > C, T278fs, E1069K, L755P, 226-11C > T, 574 + 12C>T, L114V and P128L. The majority of patients had ductal carcinoma, which mostly coexisted with HER2 amplification/overexpression. The median progression-free survival (PFS) of the 22 patients was 6.9 months (95% CI: 4.7, 9.1) in the first-line setting. The median PFS of patients who received first-line trastuzumab-based regimens was significantly longer than that of patients who received a first-line tyrosine kinase inhibitor (TKI) (10.8 months [95% CI: 2.9, 18.7] vs. 1.9 months [95% CI: 0.8, 3.0], p < 0.005). A total of 14 patients were treated with anti-HER2 antibody-drug conjugate (ADC), among whom the median treatment line of first-time of administration of anti-HER2 ADC was 4.5 (range, 1-10). Anti-HER2 ADC reached an objective response rate (ORR) of 42.9%, a disease control rate (DCR) of 85.7% and a median PFS of 7.3 months (95% CI: 4.4-10.1) from the first-time of administration.

CONCLUSION

Our data demonstrated the clinical benefit of anti-HER2 treatment in Chinese breast cancer patients harboring HER2 mutation and/or HER2 fusion. The value of immunotherapy and treatment selection among individual HER2 variants needs further study.

Efficacy and Safety of Trastuzumab Deruxtecan in Breast Cancer: A Systematic Review and Meta-Analysis

Trastuzumab deruxtecan (T-DXd) is a novel antibody-drug-conjugate (ADC), primarily used in the treatment of HER2-positive breast cancer. This study aimed to conduct a systematic review to evaluate the efficacy and safety of T-DXd in treating breast cancer, based on clinical trials. A systematic search of the literature was conducted to identify clinical trials investigating the efficacy and safety of T-DXd in breast cancer. Clinical trials of any phase were included. Outcome measures were any adverse events and survival. Meta-analysis was conducted where possible. Pooled prevalence for each adverse event of any grade and grade 3 or greater were estimated. Progression-free survival (PFS), overall survival (OS) and objective response rates (ORRs) were also reported to evaluate the efficacy of T-DXd in breast cancer. A total of 1593 patients from 6 clinical trials were included. Common adverse events of any grade were nausea, anemia, neutropenia, vomiting, fatigue, constipation and diarrhea, occurring in greater than 30% of cases. In terms of adverse events of grade 3 or more, only anemia and neutropenia occurred at a relatively high rate. Median PFS ranged from 11.1 to 22.1 months. There was evidence of a benefit of T-DXd compared to controls in terms of both PFS (OR: 0.38; 95% CI: 0.32, 0.45) and OS (OR: 0.61; 95% CI: 0.48, 0.78). ORRs ranged from 37% to 79.9%. The present systematic review shows evidence that T-DXd is a safe and effective agent in the treatment of breast cancer based on currently available data. The most common adverse events affected the blood, lymphatic and gastrointestinal systems. Interstitial lung disease (ILD) is a notable and potentially serious adverse event.

The impact of ECOG performance status on efficacy of immunotherapy and immune-based combinations in cancer patients: the MOUSEION-06 study

ECOG performance status (PS) is a pivotal prognostic factor in a wide number of solid tumors. We performed a meta-analysis to assess the role of ECOG PS in terms of survival in patients with ECOG PS 0 or ECOG PS 1 treated with immunotherapy alone or combined with other anticancer treatments. Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses, all phase II and III randomized clinical trials that compared immunotherapy or immune-based combinations in patients with solid tumors were retrieved. The outcomes of interest were overall survival (OS) and progression-free survival (PFS). We also performed subgroup analyses focused on type of therapy (ICI monotherapy or combinations), primary tumor type, setting (first line of treatment, subsequent lines). Overall, 60 studies were included in the analysis for a total of 35.020 patients. The pooled results showed that immunotherapy, either alone or in combination, reduces the risk of death or progression in both ECOG PS 0 and 1 populations. The survival benefit was consistent in all subgroups. Immune checkpoint inhibitors monotherapy or immune-based combinations are associated with improved survival irrespective of ECOG PS 0 or 1. Clinical trials should include more frail patients to assess the value of immunotherapy in these patients.

Immune checkpoint inhibitors in breast cancer: development, mechanisms of resistance and potential management strategies

The use of immune checkpoint inhibitors (ICIs) has increased exponentially in the past decade, although its progress specifically for breast cancer has been modest. The first U.S. Food and Drug Administration approval for ICI in breast cancer came in 2019, eight years after the first-ever approval of an ICI. At present, current indications for ICIs are relevant only to a subset of patients with triple-negative breast cancer, or those displaying high microsatellite instability or deficiency in the mismatch repair protein pathway. With an increasing understanding of the limitations of using ICIs, which stem from breast cancer being innately poorly immunogenic, as well as the presence of various intrinsic and acquired resistance pathways, ongoing trials are evaluating different combination therapies to overcome these barriers. In this review, we aim to describe the development timeline of ICIs and resistance mechanisms limiting their utility, and summarise the available approaches and ongoing trials relevant to overcoming each resistance mechanism.

The Evolving Landscape of Antibody-Drug Conjugates: In Depth Analysis of Recent Research Progress

Antibody-drug conjugates (ADCs) are targeted immunoconjugate constructs that integrate the potency of cytotoxic drugs with the selectivity of monoclonal antibodies, minimizing damage to healthy cells and reducing systemic toxicity. Their design allows for higher doses of the cytotoxic drug to be administered, potentially increasing efficacy. They are currently among the most promising drug classes in oncology, with efforts to expand their application for nononcological indications and in combination therapies. Here we provide a detailed overview of the recent advances in ADC research and consider future directions and challenges in promoting this promising platform to widespread therapeutic use. We examine data from the CAS Content Collection, the largest human-curated collection of published scientific information, and analyze the publication landscape of recent research to reveal the exploration trends in published documents and to provide insights into the scientific advances in the area. We also discuss the evolution of the key concepts in the field, the major technologies, and their development pipelines with company research focuses, disease targets, development stages, and publication and investment trends. A comprehensive concept map has been created based on the documents in the CAS Content Collection. We hope that this report can serve as a useful resource for understanding the current state of knowledge in the field of ADCs and the remaining challenges to fulfill their potential.

Immunological and clinicopathological features predict HER2-positive breast cancer prognosis in the neoadjuvant NeoALTTO and CALGB 40601 randomized trials

The identification of prognostic markers in patients receiving neoadjuvant therapy is crucial for treatment optimization in HER2-positive breast cancer, with the immune microenvironment being a key factor. Here, we investigate the complexity of B and T cell receptor (BCR and TCR) repertoires in the context of two phase III trials, NeoALTTO and CALGB 40601, evaluating neoadjuvant paclitaxel with trastuzumab and/or lapatinib in women with HER2-positive breast cancer. BCR features, particularly the number of reads and clones, evenness and Gini index, are heterogeneous according to hormone receptor status and PAM50 subtypes. Moreover, BCR measures describing clonal expansion, namely evenness and Gini index, are independent prognostic factors. We present a model developed in NeoALTTO and validated in CALGB 40601 that can predict event-free survival (EFS) by integrating hormone receptor and clinical nodal status, breast pathological complete response (pCR), stromal tumor-infiltrating lymphocyte levels (%) and BCR repertoire evenness. A prognostic score derived from the model and including those variables, HER2-EveNT, allows the identification of patients with 5-year EFS > 90%, and, in those not achieving pCR, of a subgroup of immune-enriched tumors with an excellent outcome despite residual disease.

Anti-HER2 Drugs for the Treatment of Advanced HER2 Positive Breast Cancer

OPINION STATEMENT

Approximately 15-20% of breast cancers (BC) demonstrate HER2 overexpression/gene amplification. Historically, before the era of HER2-directed therapies, this subtype was associated with poor prognosis. Anti-HER2 agents dramatically changed the natural course of disease and significantly prolonged patients' survival. In recent years, a number of new anti-HER2 therapies have been developed, and their approvals offer new therapeutic options for patients with advanced HER2-positive breast cancer. At present, HER2 pathway blocking drugs used in the treatment of metastatic breast cancer worldwide include trastuzumab and pertuzumab in the first-line treatment; trastuzumab deruxtecan and trastuzumab emtansine in the second line; and tucatinib, neratinib, lapatinib, and margetuximab in further lines of treatment of advanced HER2 positive breast cancer. Additionally, there are many clinical trials underway evaluating drugs blocking the HER2 pathway in advanced disease setting. This article presents new treatment options, discussing the most important findings from clinical trials and real-world reports, clinical benefits and risks of treatment, as well as efficacy of re-treatment with trastuzumab in metastatic breast cancer. New data challenge the current standards, and a number of questions arise regarding the optimal sequence of anti-HER2 targeted therapies, the optimal combination, including endocrine agents in luminal HER2 positive tumors and treatment of special patient population such as patients with brain metastases (BM).

HER2-positive breast cancer: cotargeting to overcome treatment resistance

PURPOSE OF REVIEW

The introduction in clinical practice of anti-HER2 agents changed the prognosis of patients with HER2-positive (HER2+) breast cancer in both metastatic and early setting. Although the incomparable results obtained in the last years with the approval of new drugs targeting HER2, not all patients derive benefit from these treatments, experiencing primary or secondary resistance. The aim of this article is to review the data about cotargeting HER2 with different pathways (or epitopes of receptors) involved in its oncogenic signaling, as a mechanism to overcome resistance to anti-HER2 agents.

RECENT FINDINGS

Concordantly to the knowledge of the HER2+ breast cancer heterogeneity as well as new drugs, novel predictive biomarkers of response to anti-HER2 treatments are always raised helping to define target to overcome resistance. Cotargeting HER2 and hormone receptors is the most well known mechanism to improve benefit in HER2+/HR+ breast cancer. Additional HER2-cotargeting, such as, with PI3K pathway, as well as different HERs receptors or immune-checkpoints revealed promising results.

SUMMARY

HER2+ breast cancer is an heterogenous disease. Cotargeting HER2 with other signaling pathways involved in its mechanism of resistance may improve patient outcomes. Research efforts will continue to investigate novel targets and combinations to create more effective treatment regimes.

Breast Cancer: An Overview of Current Therapeutic Strategies, Challenge, and Perspectives

Breast cancer is the most commonly diagnosed cancer and the leading cause of death among female patients, which seriously threatens the health of women in the whole world. The treatments of breast cancer require the cooperation of a multidisciplinary setting and taking tumor load and molecular makers into account. For early breast cancer, breast-conserving surgery with radiotherapy or mastectomy alone remains the standard management, and the administration of adjuvant systemic therapy is decided by the status of lymph nodes, hormone receptors, and human epidermal growth factor receptor-2. For metastatic breast cancer, the goal of treatments is to prolong survival and maintain quality of life. This review will present the current advances and controversies of surgery, chemotherapy, radiotherapy, endocrine therapy, targeted therapy, immunotherapy, gene therapy, and other innovative treatment strategies in early-stage and metastatic breast cancer.

The History and Development of HER2 Inhibitors

HER2 is highly expressed in a variety of malignant tumors and affects the prognosis of patients, making it a highly sensitive target for cancer therapy. Since the approval of the first HER2 inhibitor, trastuzumab, in 1998, HER2-targeted drugs have rapidly evolved. Currently, targeting HER2 drugs mainly include monoclonal antibodies (mAbs), tyrosine kinase inhibitors (TKIs), and antibody-drug conjugates (ADCs). This article reviews the development of HER2 inhibitors for various tumors over the past 20 years.

Incidence and risk of fatal adverse events in cancer patients treated with HER2-targeted antibody-drug conjugates: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

Antibody-drug conjugates (ADCs) that target human epidermal growth factor receptor 2 (HER2) are leading a new era of targeted cancer therapy. These drugs have also been associated with several fatal adverse events, such as pneumonia, interstitial lung disease, and infection. We performed a meta-analysis of randomized controlled trials (RCTs) to estimate the incidence and risk of fatal adverse events in cancer patients treated with HER2-targeted ADCs.

METHODS

We performed a systematic search in Embase, PubMed, Web of Science, and Scopus databases from inception to February 1, 2022, and the last search was updated to July 1, 2023. The eligible studies for inclusion in our analysis were limited to RCTs of HER2-targeted ADCs that were approved by the US Food and Drug Administration and examined on cancer patients with available data on fatal adverse events. The protocol for this study was registered in PROSPERO (No. CRD42022331627).

RESULTS

Fifteen studies (13 RCTs) involving 7,277 patients were finally included for meta-analysis. Of these patients, 4,246 received HER2-targeted ADCs and 3,481 received the control treatment. The data were combined using Bayesian hierarchical modeling, which allowed for the estimation of the mean incidence of fatal adverse events to be 0.78% (95% CrI: 0.28-1.37%, τ = 0.006) for the patients treated with HER2-targeted ADCs. The relative risk was 0.80 (95% CrI, 0.5-1.26, τ = 0.17) compared to control patients. Among 43 reported deaths caused by HER2-targeted ADCs, the most common fatal adverse event was respiratory toxicity, including pneumonia, pneumonitis, and interstitial lung disease. On subgroup analysis, no difference in the risk of fatal adverse events was found between different HER2-targeted ADCs or cancer types.

CONCLUSION

Our findings suggest that the risk of fatal adverse events with HER2-targeted ADCs may be lower compared to standard control therapies in cancer patients, and there is no significant difference in risk observed between different HER2-targeted ADCs or cancer types. However, the most common fatal adverse event was respiratory toxicity, suggesting that cancer patients who use the above drugs should strengthen respiratory system monitoring and take preventive measures in some severe cases.

B-cells and regulatory T-cells in the microenvironment of HER2+ breast cancer are associated with decreased survival: a real-world analysis of women with HER2+ metastatic breast cancer

BACKGROUND

Despite major improvements in treatment of HER2-positive metastatic breast cancer (MBC), only few patients achieve complete remission and remain progression free for a prolonged time. The tumor immune microenvironment plays an important role in the response to treatment in HER2-positive breast cancer and could contain valuable prognostic information. Detailed information on the cancer-immune cell interactions in HER2-positive MBC is however still lacking. By characterizing the tumor immune microenvironment in patients with HER2-positive MBC, we aimed to get a better understanding why overall survival (OS) differs so widely and which alternative treatment approaches may improve outcome.

METHODS

We included all patients with HER2-positive MBC who were treated with trastuzumab-based palliative therapy in the Netherlands Cancer Institute between 2000 and 2014 and for whom pre-treatment tissue from the primary tumor or from metastases was available. Infiltrating immune cells and their spatial relationships to one another and to tumor cells were characterized by immunohistochemistry and multiplex immunofluorescence. We also evaluated immune signatures and other key pathways using next-generation RNA-sequencing data. With nine years median follow-up from initial diagnosis of MBC, we investigated the association between tumor and immune characteristics and outcome.

RESULTS

A total of 124 patients with 147 samples were included and evaluated. The different technologies showed high correlations between each other. T-cells were less prevalent in metastases compared to primary tumors, whereas B-cells and regulatory T-cells (Tregs) were comparable between primary tumors and metastases. Stromal tumor-infiltrating lymphocytes in general were not associated with OS. The infiltration of B-cells and Tregs in the primary tumor was associated with unfavorable OS. Four signatures classifying the extracellular matrix of primary tumors showed differential survival in the population as a whole.

CONCLUSIONS

In a real-world cohort of 124 patients with HER2-positive MBC, B-cells, and Tregs in primary tumors are associated with unfavorable survival. With this paper, we provide a comprehensive insight in the tumor immune microenvironment that could guide further research into development of novel immunomodulatory strategies.

Newly Approved and Emerging Agents in HER2-Positive Metastatic Breast Cancer

Human epidermal growth factor receptor 2-positive breast cancer (HER2+ BC) is an aggressive tumor type, accounting for 15% to 20% of the approximately 300,000 new BC cases in the United States each year. The goal of this review is to discuss the evolving landscape of therapies for HER2+ metastatic BC (mBC). Targeted therapies that have been the standard of care (SOC) for HER2+ mBC for almost a decade have greatly improved patient outcomes. The SOC for the first-line treatment of HER2+ mBC continues to be HER2-targeted monoclonal antibodies (mAbs) + a taxane, but recent updates in the second-line setting favor use of a newer HER2-targeted antibody-drug conjugate (ADC), trastuzumab deruxtecan, versus the prior SOC ADC, trastuzumab emtansine. Numerous options are now available in the third line and beyond, including tyrosine kinase inhibitor (TKI) regimens, newer mAbs, and other ADCs. The optimal course of treatment for individual patients can be guided by location of metastases, prior therapies, concomitant biomarkers, and monitoring and management of adverse events. Ongoing trials will further the evolution of the HER2+ mBC treatment landscape. Furthermore, next-generation ADCs, TKIs, and classes of drugs that have not been approved for the treatment of HER2+ mBC, including immune checkpoint inhibitors and cyclin-dependent kinase 4 and 6 inhibitors, are also being evaluated for their efficacy in the first and second line. Although the influx of new drugs may complicate treatment decisions for physicians, having a multitude of options will undoubtedly further improve patient outcomes and patient-centered care.

A comprehensive overview on antibody-drug conjugates: from the conceptualization to cancer therapy

Antibody-Drug Conjugates (ADCs) represent an innovative class of potent anti-cancer compounds that are widely used in the treatment of hematologic malignancies and solid tumors. Unlike conventional chemotherapeutic drug-based therapies, that are mainly associated with modest specificity and therapeutic benefit, the three key components that form an ADC (a monoclonal antibody bound to a cytotoxic drug via a chemical linker moiety) achieve remarkable improvement in terms of targeted killing of cancer cells and, while sparing healthy tissues, a reduction in systemic side effects caused by off-tumor toxicity. Based on their beneficial mechanism of action, 15 ADCs have been approved to date by the market approval by the Food and Drug Administration (FDA), the European Medicines Agency (EMA) and/or other international governmental agencies for use in clinical oncology, and hundreds are undergoing evaluation in the preclinical and clinical phases. Here, our aim is to provide a comprehensive overview of the key features revolving around ADC therapeutic strategy including their structural and targeting properties, mechanism of action, the role of the tumor microenvironment and review the approved ADCs in clinical oncology, providing discussion regarding their toxicity profile, clinical manifestations and use in novel combination therapies. Finally, we briefly review ADCs in other pathological contexts and provide key information regarding ADC manufacturing and analytical characterization.

Antibody-drug conjugates in breast cancer: overcoming resistance and boosting immune response

Antibody-drug conjugates (ADCs) have emerged as a revolutionary therapeutic class, combining the precise targeting ability of monoclonal antibodies with the potent cytotoxic effects of chemotherapeutics. Notably, ADCs have rapidly advanced in the field of breast cancer treatment. This innovative approach holds promise for strengthening the immune system through antibody-mediated cellular toxicity, tumor-specific immunity, and adaptive immune responses. However, the development of upfront and acquired resistance poses substantial challenges in maximizing the effectiveness of these therapeutics, necessitating a deeper understanding of the underlying mechanisms. These mechanisms of resistance include antigen loss, derangements in ADC internalization and recycling, drug clearance, and alterations in signaling pathways and the payload target. To overcome resistance, ongoing research and development efforts are focused on urgently identifying biomarkers, integrating immune therapy approaches, and designing novel cytotoxic payloads. This Review provides an overview of the mechanisms and clinical effectiveness of ADCs, and explores their unique immune-boosting function, while also highlighting the complex resistance mechanisms and safety challenges that must be addressed. A continued focus on how ADCs impact the tumor microenvironment will help to identify new payloads that can improve patient outcomes.

Efficacy and Safety of Anti-HER2 Targeted Therapy for Metastatic HR-Positive and HER2-Positive Breast Cancer: A Bayesian Network Meta-Analysis

Despite the development of HER2-targeted drugs, achieving favorable outcomes for patients with HR+/HER2+MBC remains challenging. This study utilized Bayesian Network Meta-analysis to compare the efficacy and safety of anti-HER2 combination regimens. The primary analysis focused on progression-free survival (PFS), while secondary analyses included objective response rate, overall survival (OS) and the incidence rate of grade 3/4 adverse events (AEs). A comprehensive search across seven databases identified 25 randomized controlled trials for inclusion in this meta-analysis. For patients eligible for endocrinotherapy, our findings revealed that dual-target combined endocrine therapy, such as Her2-mAb+Her2-mAb+Endo (HR = 0.38; 95%CrI: 0.16-0.88) and Her2-mAb+Her2-tki+Endo (HR = 0.45; 95%CrI: 0.23-0.89), significantly improved PFS compared to endocrine therapy alone. According to the surface under the cumulative ranking curves (SUCRAs), Her2-mAb+Her2-mAb+Endo and Her2-mAb+Her2-tki+Endo ranked highest in terms of PFS and OS, respectively. For patients unsuitable for endocrine therapy, anti-HER2 dual-target combined chemotherapy, such as Her2-mAb+Her2-mAb+Chem (HR = 0.76; 95%CrI: 0.6-0.96) and Her2-mAb+Her2-tki+Chem (HR = 0.48; 95%CrI: 0.29-0.81), demonstrated significant improvements in PFS compared to Her2-mAb+Chem. The results were the same when compared with Her2-tki+Chem. According to the SUCRAs, Her2-mAb+Her2-tki+Chem and Her2-mAb+Her2-mAb+Chem ranked highest for PFS and OS, respectively. Subgroup analyses consistently supported these overall findings, indicating that dual-target therapy was the optimal approach irrespective of treatment line.

Reviving immunogenic cell death upon targeting TACC3 enhances T-DM1 response in HER2-positive breast cancer

Immunogenic cell death (ICD), an immune-priming form of cell death, has been shown to be induced by several different anti-cancer therapies. Despite being the first and one of the most successful antibody-drug conjugates (ADCs) approved for refractory HER2-positive breast cancer, little is known if response and resistance to trastuzumab emtansine (T-DM1) involves ICD modulation that can be leveraged to enhance T-DM1 response. Here, we report that T-DM1 induces spindle assembly checkpoint (SAC)-dependent ICD in sensitive cells by inducing eIF2α phosphorylation, surface exposure of calreticulin, ATP and HMGB1 release, and secretion of ICD-related cytokines, all of which are lost in resistance. Accordingly, an ICD-related gene signature correlates with clinical response to T-DM1-containing therapy. We found that transforming acidic coiled-coil containing 3 (TACC3) is overexpressed in T-DM1 resistant cells, and that T-DM1 responsive patients have reduced TACC3 protein while the non-responders exhibited increased TACC3 expression during T-DM1 treatment. Notably, genetic or pharmacological inhibition of TACC3 revives T-DM1-induced SAC activation and induction of ICD markers in vitro. Finally, TACC3 inhibition elicits ICD in vivo shown by vaccination assay, and it potentiates T-DM1 by inducing dendritic cell (DC) maturation and enhancing infiltration of cytotoxic T cells in the human HER2-overexpressing MMTV.f.huHER2#5 (Fo5) transgenic model. Together, our results show that ICD is a key mechanism of action of T-DM1 which is lost in resistance, and that targeting TACC3 restores T-DM1-mediated ICD and overcomes resistance.

Clinical Impact of New Treatment Strategies for HER2-Positive Metastatic Breast Cancer Patients with Resistance to Classical Anti-HER Therapies

HER2-positive breast cancer accounts for 15-20% of all breast cancer cases. This subtype is characterized by an aggressive behavior and poor prognosis. Anti-HER2 therapies have considerably improved the natural course of the disease. Despite this, relapse still occurs in around 20% of patients due to primary or acquired treatment resistance, and metastasis remains an incurable disease. This article reviews the main mechanisms underlying resistance to anti-HER2 treatments, focusing on newer HER2-targeted therapies. The progress in anti-HER2 drugs includes the development of novel antibody-drug conjugates with improvements in the conjugation process and novel linkers and payloads. Moreover, trastuzumab deruxtecan has enhanced the efficacy of trastuzumab emtansine, and the new drug trastuzumab duocarmazine is currently undergoing clinical trials to assess its effect. The combination of anti-HER2 agents with other drugs is also being evaluated. The addition of immunotherapy checkpoint inhibitors shows some benefit in a subset of patients, indicating the need for useful biomarkers to properly stratify patients. Besides, CDK4/6 and tyrosine kinase inhibitors are also included in the design of new treatment strategies. Lapitinib, neratinib and tucatinib have been approved for HER2-positive metastasis patients, however clinical trials are currently ongoing to optimize combined strategies, to reduce toxicity, and to better define the useful setting. Clinical research should be strengthened along with the discovery and validation of new biomarkers, as well as a deeper understanding of drug resistance and action mechanisms.

Tumor Infiltrating Lymphocytes (TILS) and PD-L1 Expression in Breast Cancer: A Review of Current Evidence and Prognostic Implications from Pathologist's Perspective

With the rise of novel immunotherapies able to stimulate the antitumor immune response, increasing literature concerning the immunogenicity of breast cancer has been published in recent years. Numerous clinical studies have been conducted in order to identify novel biomarkers that could reflect the immunogenicity of BC and predict response to immunotherapy. In this regard, TILs have emerged as an important immunological biomarker related to the antitumor immune response in BC. TILs are more frequently observed in triple-negative breast cancer and HER2+ subtypes, where increased TIL levels have been linked to a better response to neoadjuvant chemotherapy and improved survival. PD-L1 is a type 1 transmembrane protein ligand expressed on T lymphocytes, B lymphocytes, and antigen-presenting cells and is considered a key inhibitory checkpoint involved in cancer immune regulation. PD-L1 immunohistochemical expression in breast cancer is observed in about 10-30% of cases and is extremely variable based on tumor stage and molecular subtypes. Briefly, TNBC shows the highest percentage of PD-L1 positivity, followed by HER2+ tumors. On the other hand, PD-L1 is rarely expressed (0-10% of cases) in hormone-receptor-positive BC. The prognostic role of PD-L1 expression in BC is still controversial since different immunohistochemistry (IHC) clones, cut-off points, and scoring systems have been utilized across published studies. In the present paper, an extensive review of the current knowledge of the immune landscape of BC is provided. TILS and PD-L1 expression across different BC subtypes are discussed, providing a guide for their pathological assessment and reporting.

Antibody-Drug Conjugates in Breast Cancer: Current Status and Future Directions

Antibody drug conjugates (ADCs) are novel medications that combine monoclonal antibodies with cytotoxic payloads, enabling the selective delivery of potent drugs to cancer cells expressing specific surface antigens. This targeted strategy seeks to optimize treatment effectiveness while reducing the risk of systemic toxicity, distinguishing ADCs from conventional chemotherapy. The rapid growth in ADC research has led to numerous developments and approvals for cancer treatment, with significant impacts on the management of breast cancer. ADCs like T-DXd for HER2-low disease and sacituzumab govitecan for triple negative breast cancer (TNBC) have provided valuable options for challenging subtypes of breast cancer. However, essential questions still need to be addressed, including the optimal order of ADCs amidst the growing number of newly developed ones and strategies to overcome resistance mechanisms. Preclinical studies have shed light on potential resistance mechanisms, emphasizing the potential benefit of combinational approaches with other agents such as immune checkpoint inhibitors (ICIs) and targeted tyrosine kinase inhibitors (TKIs) to enhance treatment effectiveness. Additionally, personalized approaches based on molecular profiling hold promise in tailoring ADC treatments to individual tumors, identifying unique molecular markers for each patient to optimize treatment efficacy while minimizing side effects.

Emerging insights into mechanisms of trastuzumab resistance in HER2-positive cancers

HER2 is an established therapeutic target in breast, gastric, and gastroesophageal junction carcinomas with HER2 overexpression or genomic alterations. The humanized monoclonal antibody trastuzumab targeting HER2 has substantially improved the clinical outcomes of HER2-positive patients, yet the inevitable intrinsic or acquired resistance to trastuzumab limits its clinical benefit, necessitating the elucidation of resistance mechanisms to develop alternate therapeutic strategies. This review presents an overview of trastuzumab resistance mechanisms involving signaling pathways, cellular metabolism, cell plasticity, and tumor microenvironment, particularly discussing the prospects of developing rational combinations to improve patient outcomes.

[Diagnosis and management of interstitial lung disease induced by antibody-drug conjugates in breast cancer: A French expert opinion paper]

Interstitial lung disease (ILD) has been reported with many cancer drugs including some recent antibody-drug conjugates (ADCs). The mechanisms of ILD induced by many chemotherapy drugs, other drug classes and ADCs used in cancer, including breast cancer, are not clearly elucidated. In the absence of specific clinical or radiological signs, the diagnosis of drug-induced ILD is often a diagnosis of exclusion. When present, the most frequent symptoms are respiratory signs (cough, dyspnea, chest pain) and general signs (fatigue, fever). Any suspicion of ILD should be evaluated by imaging and, if in doubt, the CT scan should be evaluated by a pulmonologist and a radiologist. A network of multidisciplinary experts for proactive early management of ILD is important, including oncologist, radiologist, pulmonologist, infectious disease specialist and nurses. Patient education is essential to report new or exacerbated lung symptoms and prevent high-grade ILD. Study drug is discontinued temporarily or permanently according to ILD severity and type of ADC. For asymptomatic cases (Grade 1), the efficacy of corticosteroids is not clearly established; for higher grades, the benefit/risk balance of long-term corticosteroid therapy should be considered for the dose and treatment duration. Hospitalization and oxygen supplementation are required for severe cases (Grades 3-4). For patient follow-up, the expertise of a pulmonologist is necessary with repeated chest scans, spirometry and DLCO. Preventing ADC-induced ILDs and evolution to high grade rests on a network of multidisciplinary experts for assessment of individual risk factors, early management, close follow-up and patient education.

Metastatic HER2-Positive Breast Cancer: Is There an Optimal Sequence of Therapy?

OPINION STATEMENT

Approximately 20% of breast cancers overexpress human epidermal growth factor receptor 2 (HER2+), conferring a particularly aggressive subtype of the disease with an increased risk for the development of systemic and brain metastases. However, the advent of trastuzumab and more recently several other HER2-targeting novel therapies has led to significant improvements in the prognosis, making the diagnosis a "double-edged sword." The current standard first-line therapy for patients with HER2+ metastatic breast cancer (MBC) is a taxane combined with trastuzumab and pertuzumab. Trastuzumab deruxtecan should be used preferentially in the second line, with the only caveat being patients with CNS involvement where the tucatinib, capecitabine, and trastuzumab regimen could be considered. In the third line setting, given the survival benefits demonstrated with the tucatinib regimen in patients with and without CNS metastases, this is the preferred strategy. In the fourth line and beyond, there is no clear standard. Options include margetuximab in combination with chemotherapy, neratinib + capecitabine, or trastuzumab + chemotherapy. There are several novel therapies under investigation reporting promising results in the late-line setting. The treatment landscape of HER2-positive advanced disease is evolving constantly, with several active therapies being moved to the early-stage setting. Accordingly, it will be critical to identify biomarkers and mechanisms of resistance to optimize therapy selection and maximize patient outcomes and quality of life. Here, we provide an overview of the current and future management of HER2-positive advanced breast cancer and address the specific scenarios which may impact treatment selection including triple-positive breast cancer and the presence of brain metastases. Finally, we highlight promising novel treatments and ongoing trials that may impact future treatment sequencing.

Current indications and future perspectives for antibody-drug conjugates in brain metastases of breast cancer

Breast cancer is one of the main cause of cerebral and leptomeningeal metastases, the prognosis of which remains poor to this day. Most studies excluded patients with active brain metastases (BM) and particularly with leptomeningeal metastases (LM) explaining the lack of therapeutic innovation in this area. Currently, the standard management of patients with BM of breast cancer is based on the combination of surgery, radiotherapy and systemic treatments. Recently, third-generation of Antibody-Drug Conjugates (ADCs), have revolutionized the management of metastatic breast cancer. Trastuzumab deruxtecan and Sacituzumab govitecan have indeed shown significant improvements of survival outcomes and can now be used in a wide range of breast cancer subtypes. However, few data are available on the efficacy of third-generation ADCs on BM and LM of breast cancer. As the field of ADCs is rapidly evolving, with new constructs entering the late clinical development, in this review we describe the efficacy of approved and novel promising conjugates on patients with BM and LM of breast cancer.

Antibody-Drug Conjugates for the Treatment of Renal Cancer: A Scoping Review on Current Evidence and Clinical Perspectives

Antibody-drug conjugates (ADCs) are complex chemical structures composed of a monoclonal antibody, serving as a link to target cells, which is conjugated with a potent cytotoxic drug (i.e., payload) through a chemical linker. Inspired by Paul Ehrlich's concept of the ideal anticancer drug as a "magic bullet", ADCs are also highly specific anticancer agents, as they have been demonstrated to recognize, bind, and neutralize cancer cells, limiting injuries to normal cells. ADCs are among the newest pharmacologic breakthroughs in treating solid and hematologic malignancies. Indeed, in recent years, various ADCs have been approved by the Food and Drug Administration and European Medicines Agency for the treatment of several cancers, resulting in a "practice-changing" approach. However, despite these successes, no ADC is approved for treating patients affected by renal cell carcinoma (RCC). In the present paper, we thoroughly reviewed the current literature and summarized preclinical studies and clinical trials that evaluated the activity and toxicity profile of ADCs in RCC patients. Moreover, we scrutinized the potential causes that, until now, hampered the therapeutical success of ADCs in those patients. Finally, we discussed novel strategies that would improve the development of ADCs and their efficacy in treating RCC patients.

Appraisal of Systemic Treatment Strategies in Early HER2-Positive Breast Cancer-A Literature Review

BACKGROUND

The overexpression of the human epidermal growth factor receptor 2 (HER2+) accounts for 15-20% of all breast cancer phenotypes. Even after the completion of the standard combination of chemotherapy and trastuzumab, relapse events occur in approximately 15% of cases. The neoadjuvant approach has multiple benefits that include the potential to downgrade staging and convert previously unresectable tumors to operable tumors. In addition, achieving a pathologic complete response (pCR) following preoperative systemic treatment is prognostic of enhanced survival outcomes. Thus, optimal evaluation among the suitable strategies is crucial in deciding which patients should be selected for the neoadjuvant approach.

METHODS

A literature search was conducted in the Embase, Medline, and Cochrane electronic libraries.

CONCLUSION

The evaluation of tumor and LN staging and, hence, stratifying BC recurrence risk are decisive factors in guiding clinicians to optimize treatment decisions between the neoadjuvant versus adjuvant approaches. For each individual case, it is important to consider the most likely postsurgical outcome, since, if the patient does not obtain pCR following neoadjuvant treatment, they are eligible for adjuvant T-DM1 in the case of residual disease. This review of HER2-positive female BC outlines suitable neoadjuvant and adjuvant systemic treatment strategies for guiding clinical decision making around the selection of an appropriate therapy.

Antibody-Drug Conjugates in Solid Tumor Oncology: An Effectiveness Payday with a Targeted Payload

Antibody-drug conjugates (ADCs) are at the forefront of the drug development revolution occurring in oncology. Formed from three main components-an antibody, a linker molecule, and a cytotoxic agent ("payload"), ADCs have the unique ability to deliver cytotoxic agents to cells expressing a specific antigen, a great leap forward from traditional chemotherapeutic approaches that cause widespread effects without specificity. A variety of payloads can be used, including most frequently microtubular inhibitors (auristatins and maytansinoids), as well as topoisomerase inhibitors and alkylating agents. Finally, linkers play a critical role in the ADCs' effect, as cleavable moieties that serve as linkers impact site-specific activation as well as bystander killing effects, an upshot that is especially important in solid tumors that often express a variety of antigens. While ADCs were initially used in hematologic malignancies, their utility has been demonstrated in multiple solid tumor malignancies, including breast, gastrointestinal, lung, cervical, ovarian, and urothelial cancers. Currently, six ADCs are FDA-approved for the treatment of solid tumors: ado-trastuzumab emtansine and trastuzumab deruxtecan, both anti-HER2; enfortumab-vedotin, targeting nectin-4; sacituzuzmab govitecan, targeting Trop2; tisotumab vedotin, targeting tissue factor; and mirvetuximab soravtansine, targeting folate receptor-alpha. Although they demonstrate utility and tolerable safety profiles, ADCs may become ineffective as tumor cells undergo evolution to avoid expressing the specific antigen being targeted. Furthermore, the current cost of ADCs can be limiting their reach. Here, we review the structure and functions of ADCs, as well as ongoing clinical investigations into novel ADCs and their potential as treatments of solid malignancies.

Antibody-drug conjugates come of age in oncology

Antibody-drug conjugates (ADCs) combine the specificity of monoclonal antibodies with the potency of highly cytotoxic agents, potentially reducing the severity of side effects by preferentially targeting their payload to the tumour site. ADCs are being increasingly used in combination with other agents, including as first-line cancer therapies. As the technology to produce these complex therapeutics has matured, many more ADCs have been approved or are in late-phase clinical trials. The diversification of antigenic targets as well as bioactive payloads is rapidly broadening the scope of tumour indications for ADCs. Moreover, novel vector protein formats as well as warheads targeting the tumour microenvironment are expected to improve the intratumour distribution or activation of ADCs, and consequently their anticancer activity for difficult-to-treat tumour types. However, toxicity remains a key issue in the development of these agents, and better understanding and management of ADC-related toxicities will be essential for further optimization. This Review provides a broad overview of the recent advances and challenges in ADC development for cancer treatment.

Combination therapy with antibody‑drug conjugate RC48 (disitamab vedotin) and zimberelimab (PD‑1 inhibitor) successfully controlled recurrent HER2‑positive breast cancer resistant to trastuzumab emtansine: A case report

Options for later-line therapy are limited for patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer who have exhibited resistance to several systemic treatments. Antibody drug conjugates (ADCs) and immune checkpoint inhibitors are novel approaches for HER2-positive breast cancer, but few reports have been published regarding the efficacy of their combinations, particularly in patients with prior ADC failure. The present report describes a case of recurrent metastatic HER2-positive breast cancer, which responded poorly to several perioperative systemic therapies, including chemotherapies, HER2-targeted antibodies, small molecule inhibitors and trastuzumab emtansine (an ADC), along with post-surgical radiotherapy. Following failure of front-line therapies for recurrent cancer located in the chest wall, combination treatment with another HER2-targeted ADC, disitamab vedotin (120 mg), and zimberelimab (240 mg), a fully humanized anti-programmed cell death protein-1 (PD-1) antibody, administered intravenously every 2 weeks, was initiated. The tumor lesions improved slightly after two cycles of treatment and shrunk markedly, and almost disappeared at the end of the sixth cycle of therapy. The patient is still in remission at present. The present findings suggest the potential efficacy of HER2-targeted ADCs combined with PD-1 inhibitors for patients with HER2-positive breast cancer, including those resistant to prior HER2-targeted ADCs.

A new paradigm for classifying and treating HER2-positive breast cancer

BACKGROUND

Because of the phenomenal success of treatment with monoclonal antibodies and antibody-drug conjugates targeting human epidermal growth factor receptor 2 (HER2), most patients with early-stage HER2-positive breast cancer (HER2+ BC) and some with limited metastatic diseases have been cured, and those who have not been cured have achieved significant improvements in overall survival, which has weakened the role of the TNM staging system in the prognosis of HER2+ BC today. Given that the disease is now highly curable, treatment conception, classification, and modalities should differ from those of cancer types with a poor prognosis. It is warranted to build a new paradigm for classifying and treating HER2+ BC.

RECENT FINDINGS

In our personal view, we suggest that the classification system should be based not only on traditional anatomy and cancer biology but also on available treatment regimens, their exceptional outcomes, and their toxicities. In this regard, we developed a new concise classification of HER2+ BC based on the TNM staging system, a review of the literature, research results, and our clinical experience, dividing the patients into four distinct groups: curable (lymph-node negative and small (≤3 cm) early breast cancer), do our best to cure (locally advanced or tumors >3 cm early breast cancer), hope for cure (local-regional recurrent, limited metastases, and exceptional responders), and incurable (metastatic breast cancer with poor performance status or non-exceptional responders).

CONCLUSION

It will assist clinicians in developing an optimal treatment regimen at the outset, curing more HER2+ BC patients and improving their quality of life.

Antibody-Drug Conjugates: Ushering in a New Era of Cancer Therapy

Antibody-drug conjugates (ADCs) have provided new therapeutic options and significant promise for patients with cancer, particularly where existing treatments are limited. Substantial effort in ADC development is underway globally, with 13 ADCs currently approved and many more in development. The therapeutic benefits of ADCs leverage the ability to selectively target cancer cells through antibody binding, resultant relative sparing of non-malignant tissues, and the targeted delivery of a cytotoxic payload. Consequently, this drug class has demonstrated activity in multiple malignancies refractory to standard therapeutic options. Despite this, limitations exist, including narrow therapeutic windows, unique toxicity profiles, development of therapeutic resistance, and appropriate biomarker selection. This review will describe the development of ADCs, their mechanisms of action, pivotal trials, and approved indications and identify common themes. Current challenges and opportunities will be discussed for this drug class in cancer therapeutics at a time when significant developments in antibody therapies, immunotherapy, and targeted agents are occurring.

Antibody-Drug Conjugates for Breast Cancer Treatment: Emerging Agents, Targets and Future Directions

To achieve the scheme of "magic bullets" in antitumor therapy, antibody-drug conjugates (ADCs) were developed. ADCs consist of antibodies targeting tumor-specific antigens, chemical linkers, and cytotoxic payloads that powerfully kill cancer cells. With the approval of ado-trastuzumab emtansine (T-DM1) and fam-trastuzumab deruxtecan (T-DXd), the therapeutic potentials of ADCs in breast cancer have come into the spotlight. Nearly 30 ADCs for breast cancer are under exploration to move targeted therapy forward. In this review, we summarize the presenting and emerging agents and targets of ADCs. The ADC structure and development history are also concluded. Moreover, the challenges faced and prospected future directions in this field are reviewed, which give insights into novel treatments with ADCs for breast cancer.