Induction of adaptive Anti-HER2/neu immune responses in a Phase 1B/2 trial of 2B1 bispecific murine monoclonal antibody in metastatic breast cancer (E3194): a trial coordinated by the Eastern Cooperative Oncology Group

Warming-up the immune cell engagers (ICEs) era in breast cancer: state of the art and future directions

The advent of immune checkpoint inhibitors (ICIs) has deeply reshaped the therapeutic algorithm of triple-negative breast cancer (TNBC). However, there is considerable scope for better engagement of the immune system in other BC subtypes. ICIs have paved the way for investigations into emerging immunotherapeutic strategies, such as immune cell engagers (ICEs) that work by promoting efficient tumor cell killing through the redirection of immune system against cancer cells. Most ICEs are bispecific antibodies that simultaneously recognize and bind to both cancer and immune cells generating an artificial synapse. Major side effects are cytokine release syndrome, hepatotoxicity, and neurotoxicity related to inappropriate immune system activation. Here, we provide a comprehensive overview of this compounds, the available preclinical and clinical evidence supporting their investigation and development in BC also highlighting the challenges that have prevented their widespread use in oncology. Finally, major strategies are explored to broaden their use in BC.

Targeting HER2-positive breast cancer: advances and future directions

The long-sought discovery of HER2 as an actionable and highly sensitive therapeutic target was a major breakthrough for the treatment of highly aggressive HER2-positive breast cancer, leading to approval of the first HER2-targeted drug - the monoclonal antibody trastuzumab - almost 25 years ago. Since then, progress has been swift and the impressive clinical activity across multiple trials with monoclonal antibodies, tyrosine kinase inhibitors and antibody-drug conjugates that target HER2 has spawned extensive efforts to develop newer platforms and more targeted therapies. This Review discusses the current standards of care for HER2-positive breast cancer, mechanisms of resistance to HER2-targeted therapy and new therapeutic approaches and agents, including strategies to harness the immune system.

Immunological Landscape of HER-2 Positive Breast Cancer

Understanding the biological aspects of immune response in HER2+ breast cancer is crucial to implementing new treatment strategies in these patients. It is well known that anti-HER2 therapy has improved survival in this population, yet a substantial percentage may relapse, creating a need within the scientific community to uncover resistance mechanisms and determine how to overcome them. This systematic review indicates the immunological mechanisms through which trastuzumab and other agents target cancer cells, also outlining the main trials studying immune checkpoint blockade. Finally, we report on anti-HER2 vaccines and include a figure exemplifying their mechanisms of action.

AMPD1 Is Associated With the Immune Response and Serves as a Prognostic Marker in HER2-Positive Breast Cancer

Background

Although immunotherapy has been used in the treatment of metastatic triple negative breast cancer (TNBC), its therapeutic influence on human epidermal growth factor receptor 2 (HER2)-positive subtype remains controversial. It is therefore imperative to find biomarkers that can predict the immune response in HER2+ BC.

Methods

ESTIMATE was utilized to compute the ImmuneScore and StromalScore from data obtained from TCGA database, and differentially expressed genes (DEGs) were identified. In addition, univariate Cox regression was used to assess candidate genes such as AMPD1, CD33, and CCR5. Gene set enrichment analysis (GSEA) was used to further understand AMPD1-associated pathways. Moreover, immunohistochemical analyses were performed to further reveal the relationship among AMPD1, CD4 and CD8 genes.

Results

The expression of AMPD1 was markedly associated with disease outcome and tumor-infiltrating immune cells (TICs). In addition, AMPD1 was associated with lymph node status, age and the expression of PD-L1 and PD-L2. High AMPD1 expression was linked to longer overall survival (OS). Upregulated expression of AMPD1 correlated with the enrichment of immune-related signaling pathways. In addition, immunohistochemical analyses demonstrated a co-expression profile among AMPD1, CD4 and CD8 genes.

Conclusions

Taken together, our data demonstrated that AMPD1 might serve as a novel biomarker for predicting the immune response and disease outcome in HER2+ BC.

Immunotherapy in HER2-positive breast cancer: state of the art and future perspectives

Breast cancer (BC) is a complex disease with primary or acquired incurability characteristics in a significant part of patients. Immunotherapeutical agents represent an emerging option for breast cancer treatment, including the human epidermal growth factor 2 positive (HER2+) subtype. The immune system holds the ability to spontaneously implement a defensive response against HER2+ BC cells through complex mechanisms which can be exploited to modulate this response for obtaining a clinical benefit. Initial immune system modulating strategies consisted mostly in vaccine therapies, which are still being investigated and improved. However, the entrance of trastuzumab into the scenery of HER2+ BC treatment was the real game changing event, which embodied a dominant immune-mediated mechanism. More recently, the advent of the immune checkpoint inhibitors has caused a new paradigm shift for immuno-oncology, with promising initial results also for HER2+ BC. Breast cancer has been traditionally considered poorly immunogenic, being characterized by relatively low tumor mutation burden (TMB). Nevertheless, recent evidence has revealed high tumor infiltrating lymphocytes (TILs) and programmed cell death-ligand 1 (PD-L1) expression in a considerable proportion of HER2+ BC patients. This may translate into a higher potential to elicit anti-cancer response and, therefore, wider possibilities for the use and implementation of immunotherapy in this subset of BC patients. We are herein presenting and critically discussing the most representative evidence concerning immunotherapy in HER2+ BC cancer, both singularly and in combination with therapeutic agents acting throughout HER2-block, immune checkpoint inhibition and anti-cancer vaccines. The reader will be also provided with hints concerning potential future projection of the most promising immutherapeutic agents and approaches for the disease of interest.

Harnessing the immune system in the battle against breast cancer

Breast cancer is the most prevalent malignancy in women and the second most common cause of cancer-related death worldwide. Despite major innovations in early detection and advanced therapeutics, up to 30% of women with node-negative breast cancer and 70% of women with node-positive breast cancer will develop recurrence. The recognition that breast tumors are infiltrated by a complex array of immune cells that influence their development, progression, and metastasis, as well as their responsiveness to systemic therapies has sparked major interest in the development of immunotherapies. In fact, not only the native host immune system can be altered to promote potent antitumor response, but also its components can be manipulated to generate effective therapeutic strategies. We present here a review of the major approaches to immunotherapy in breast cancers, both successes and failures, as well as new therapies on the horizon.

Perspectives of HER2-targeting in gastric and esophageal cancer

INTRODUCTION

The blockade of HER2 signaling has significantly improved the outlook for esophagogastric cancer patients. However, targeting HER2 still remains challenging due to complex biology of this receptor in gastric and esophageal cancers. Areas covered: Here, we review complex HER2 biology, current methods of HER2 testing and tumor heterogeneity of gastroesophageal cancer. Ongoing and completed clinical research data are discussed. Expert opinion: HER2 overexpression is a validated target in gastroesophageal cancer, with therapeutic implications resulting in prolonged survival when inhibited in the front-line setting. With standardized HER2 testing in gastro-esophageal cancer, the ongoing trials are testing newer agents and combinations including combination of anti-HER2 antibodies with immunotherapy. Clonal heterogeneity and emergence of resistance will challenge our approach to treating these patients beyond the frontline settings.

A FcγRIII-engaging bispecific antibody expands the range of HER2-expressing breast tumors eligible to antibody therapy

Trastuzumab is established as treatment of HER2^high metastatic breast cancers but many limitations impair its efficacy. Here, we report the design of a Fab-like bispecific antibody (HER2bsFab) that displays a moderate affinity for HER2 and a unique, specific and high affinity for FcγRIII. In vitro characterization showed that ADCC was the major mechanism of action of HER2bsFab as no significant HER2-driven effect was observed. HER2bsFab mediated ADCC at picomolar concentration against HER2^high, HER2^low as well as trastuzumab-refractive cell lines. In vivo HER2bsFab potently inhibited HER2^high tumor growth by recruitment of mouse FcγRIII and IV-positive resident effector cells and more importantly, exhibited a net superiority over trastuzumab at inhibiting HER2^low tumor growth. Moreover, FcγRIIIA-engagement by HER2bsFab was independent of V/F158 polymorphism and induced a stronger NK cells activation in response to target cell recognition. Thus, taking advantage of its epitope specificity and affinity for HER2 and FcγRIIIA, HER2bsFab exhibits potent anti-tumor activity against HER2^low tumors while evading most of trastuzumab Fc-linked limitations thereby potentially enlarging the number of patients eligible for breast cancer immunotherapy.

Biological role of NK cells and immunotherapeutic approaches in breast cancer

In recent decades, tumor surveillance by the immune system and its impact on disease outcomes in cancer patients in general and in breast cancer (BC) patients in particular has been documented. Natural killer (NK) cells are central components of the innate immunity and existing data indicate that they play a role in preventing and controlling tumor growth and metastasis. Their biological significance was first recognized by their ability to exert direct cellular cytotoxicity without prior sensitization. This is important in tumors, as transforming events are likely to result in downregulation of self-ligands and expression of stress-induced ligands which can be recognized by NK cells. Their activation also leads to secretion of stimulatory cytokines which participate in cancer elimination by several direct mechanisms as well as by stimulating the adaptive immune system. In this regard, it was recently revealed a dendritic cell (DC)-NK-cell crosstalk which provides another novel pathway linking innate and adaptive immunity. In addition, NK cells are feasible targets of stimulation in immunotherapeutic approaches such as antibody-based strategies and adoptive cell transfer. Nevertheless, NK cells display impaired functionality and capability to infiltrate tumors in BC patients. This review compiles information about NK-cell biology in BC and the attempts which aim to manipulate them in novel therapeutic approaches in this pathology.

Targeting T cells with bispecific antibodies for cancer therapy

Bispecific antibodies (BiAbs) offer a unique opportunity to redirect immune effector cells to kill cancer cells. BiAbs combine the benefits of different binding specificities of two monoclonal antibodies (mAbs) into a single construct. This unique feature of BiAbs enables approaches that are not possible with single mAbs. Advances in antibody engineering and antigen profiling of malignant cells have led to the development of a number of BiAb formats and their combinations for redirecting effector cells to tumor targets. There have been significant advances in the design and application of BiAbs for intravenous and local injection.The initial barrier of cytokine storm has been partially overcome by more recent constructs that have improved clinical effectiveness without dose-limiting toxicities. Since the recent revival of BiAbs, there has been multiple, ongoing, phase I/II and III trials, and some promising clinical outcomes have been reported in completed clinical studies. This review focuses on arming T cells with BiAbs to create the 'poor man's cytotoxic lymphocyte'.

Effective antibody therapy induces host-protective antitumor immunity that is augmented by TLR4 agonist treatment

Toll-like receptors are potent activators of the innate immune system and generate signals leading to the initiation of the adaptive immune response that can be utilized for therapeutic purposes. We tested the hypothesis that combined treatment with a Toll-like receptor agonist and an antitumor monoclonal antibody is effective and induces host-protective antitumor immunity. C57BL/6 human mutated HER2 (hmHER2) transgenic mice that constitutively express kinase-deficient human HER2 under control of the CMV promoter were established. These mice demonstrate immunological tolerance to D5-HER2, a syngeneic human HER2-expressing melanoma cell line. This human HER2-tolerant model offers the potential to serve as a preclinical model to test both antibody therapy and the immunization potential of human HER2-targeted therapeutics. Here, we show that E6020, a Toll-like receptor-4 (TLR4) agonist effectively boosted the antitumor efficacy of the monoclonal antibody trastuzumab in immunodeficient C57BL/6 SCID mice as well as in C57BL/6 hmHER2 transgenic mice. E6020 and trastuzumab co-treatment resulted in significantly greater inhibition of tumor growth than was observed with either agent individually. Furthermore, mice treated with the combination of trastuzumab and the TLR4 agonist were protected against rechallenge with human HER2-transfected tumor cells in hmHER2 transgenic mouse strains. These findings suggest that combined treatment with trastuzumab and a TLR4 agonist not only promotes direct antitumor effects but also induces a host-protective human HER2-directed adaptive immune response, indicative of a memory response. These data provide an immunological rationale for testing TLR4 agonists in combination with antibody therapy in patients with cancer.

Testing for HER2 in Breast Cancer: A Continuing Evolution

Human epidermal growth factor receptor 2 (HER2) is an important prognostic and predictive factor in breast cancer. HER2 is overexpressed in approximately 15%–20% of invasive breast carcinomas and is associated with earlier recurrence, shortened disease free survival, and poor prognosis. Trastuzumab (Herceptin) a “humanized” monoclonal antibody targets the extracellular domain of HER2 and is widely used in the management of HER2 positive breast cancers. Accurate assessment of HER2 is thus critical in the management of breast cancer. The aim of this paper is to present a comprehensive review of HER2 with reference to its discovery and biology, clinical significance, prognostic value, targeted therapy, current and new testing modalities, and the interpretation guidelines and pitfalls.

Bispecific antibodies for cancer therapy

Bispecific antibodies, in contrast to conventional monoclonal antibodies, can bind simultaneously two different antigens. Taking advantage of this virtue, they are mostly designed for immune effector cell redirection to tumors and for radionuclide pretargeting to tumors. Bispecific antibodies of the first generation were produced by chemical cross-linking or cell-fusion technologies. More recently, the application of genetic engineering technologies gave rise to numerous formats of bispecific antibody fragments and whole IgG molecules. Because bispecific antibodies enable therapeutic strategies that are not possible with conventional monoclonal antibodies, they attract strong interest. Several bispecific antibody formats have already shown clinical efficacy in cancer patients, catalyzing efforts to translate the imaginative bispecific antibody concepts into effective therapies.

Activating and inhibitory Fcgamma receptors in immunotherapy: being the actor or being the target

Membrane Fcgamma receptors (FcgammaRs) can act either as potent activators of effector cell functions or as inhibitors of receptor-mediated cell activation following engagement by IgG antibodies bound to their target molecules. The remarkable ability of activating FcgammaRs to trigger antibody-dependent cellular cytotoxicity, cytokine release and phagocytosis/endocytosis followed by antigen presentation has stimulated the development of a number of therapeutic monoclonal antibodies whose Fc regions have been engineered to optimize their effector functions, mostly their killing activities. Conversely, the demonstration that inhibitory FcgammaRs can block or downmodulate effector functions has led to the concept that targeting these receptors is of interest in a number of pathologies. The use of bispecific antibodies leading to the crosslinking of FcgammaRIIB with activating receptors could induce immunomodulation in autoimmune or allergic diseases. Alternatively, the use of cytotoxic/antagonist anti-FcgammaRIIB antibodies could kill FcgammaRIIB-positive tumor cells or prevent the downmodulation of activating receptors. Thus, antibodies engineered to preferentially target activating or inhibitory FcgammaRs are currently being designed for therapeutic use.

Ertumaxomab: a trifunctional antibody for breast cancer treatment

Ertumaxomab is an intact bispecific antibody targeting HER2/neu and CD3 with preferential binding to activating Fcgamma type I/III-receptors, resulting in the formation of a tri-cell complex among tumour cell, T cell and accessory cell. Recently, the antibody demonstrated antitumour efficacy against HER2/neu low-expressing tumours resistant to trastuzumab. Data from a completed Phase I study in metastatic breast cancer patients indicates strong immune responses. Owing to efficient tumour cell destruction by humoral and T-cell-dependent mechanisms, differing from conventional HER2/neu directed treatments, and a potential for long-lasting antitumour immunoreactivity, ertumaxomab is at present investigated within Phase II studies enrolling metastatic breast cancer patients even without HER2/neu gene amplification.

Development and prospects for bispecific antibody-based therapeutics in cancer and other applications

BACKGROUND

Progress in molecular biology for the production of bispecific antibodies (BiAbs) and the expanding knowledge on receptors on malignant and normal target cells provide the basis for developing new strategies using antibody- and/or receptor-based platform technology for the treatment of cancer and other diseases.

OBJECTIVE

This review provides a preclinical and clinical perspective on application of bispecific antibodies for the treatment of solid tumors, hematologic malignancies and other diseases.

METHODS

This review focuses on BiAb-based immunotherapy, clinical trials, alternative strategies, the challenges of technology and future applications.

RESULTS/CONCLUSION

The successful application of a particular BiAb will depend on a thorough evaluation of the expected functional application and thoughtful engineering of structure, affinity and number of binding sites based on the desired function.

New ways to target old receptors

Numerous important drugs target cytokines and growth factors or their receptors. Our understanding of the molecular mechanisms governing receptor activation and signaling has lagged in key areas, however, limiting drug discovery efforts to relatively few basic strategies. Recently, substantial progress has been made on several aspects of this problem. These include improved methods for establishing the mechanism of receptor activation, a clearer understanding of the biochemical basis for differential signaling by ligands that act through a common receptor, new methods for measuring the affinities of steps in receptor activation on live cells, and progress toward a systems level understanding of receptor signaling. These advances are providing a new understanding of the function of these receptors that presents opportunities for the development of improved drugs.