Overall survival benefit with lapatinib in combination with trastuzumab for patients with human epidermal growth factor receptor 2-positive metastatic breast cancer: final results from the EGF104900 Study

Skeletal metastasis: treatments, mouse models, and the Wnt signaling

Skeletal metastases result in significant morbidity and mortality. This is particularly true of cancers with a strong predilection for the bone, such as breast, prostate, and lung cancers. There is currently no reliable cure for skeletal metastasis, and palliative therapy options are limited. The Wnt signaling pathway has been found to play an integral role in the process of skeletal metastasis and may be an important clinical target. Several experimental models of skeletal metastasis have been used to find new biomarkers and test new treatments. In this review, we discuss pathologic process of bone metastasis, the roles of the Wnt signaling, and the available experimental models and treatments.

Investigational therapies targeting the ErbB (EGFR, HER2, HER3, HER4) family in GI cancers

INTRODUCTION

Gastrointestinal (GI) malignancies account for nearly one-fourth of all cancer-related deaths in the United States and approximately 30% of all cancer-related deaths worldwide. Use of combination cytotoxic therapy offers a modest improvement in survival, but the prognosis and long-term survival of most patients with GI cancer remains poor. In certain GI malignancies, therapies that target members of the HER family of receptors have positively impacted patient care.

AREAS COVERED

In this review, we discuss the significance of the HER family of receptors in esophagogastric, hepatobiliary, pancreatic, and colorectal cancers and explain the rationale supporting the use of monoclonal antibodies (mAbs) and small molecule tyrosine kinase inhibitors (TKIs) to inhibit HER activation and downstream events that contribute to tumor proliferation, migration, and survival.

EXPERT OPINION

Despite recent advances, the treatment of GI cancers remains challenging. Therapies targeting the HER family of receptors have been extensively studied in these malignancies with inconsistent results. The rationale behind varied tumor responses with these agents remains uncertain. We believe that additional studies are needed to identify biomarkers that could help identify a population of patients who would be more responsive to a given therapy.

Beyond trastuzumab and lapatinib: new options for HER2-positive breast cancer

HER2-positive breast cancer (BC) constitutes a molecular subtype of the disease with an aggressive biologic behavior. Trastuzumab revolutionized the treatment of this disease, changing its natural history. Lapatinib is active in the metastatic setting, approved for patients who were pretreated with trastuzumab. However, resistance to anti-HER2 agents is a major clinical issue, occurring in both early-stage and advanced disease, and new treatment options are clearly needed. An abundance of HER2-targeted agents are being clinically developed: monoclonal antibodies, small molecule inhibitors, and antibody drug conjugates (ADC). Combining HER2-targeted agents in regimens of dual HER2 blockade has already reached clinical practice in the metastatic setting, confirming the preclinical efficacy of enhanced HER2 inhibition. Promising results have been generated in the neoadjuvant setting, and large randomized trials are seeking evidence for dual HER2 blockade in the adjuvant setting. ADC represent another hope for improved treatment outcomes of HER2-positive BC, as exemplified by the positive results of clinical trials employing trastuzumab-DM1 (trastuzumab emtansine, T-DM1). Moreover, an understanding of the molecular mechanisms mediating resistance to HER2 blockade has opened new therapeutic avenues, with several targeted agents entering clinical trials. This paper presents the clinical data of the HER2-targeted agents under development, as well as an overview of the biologic rationale for the development of agents aimed at circumventing anti-HER2 resistance.

When Standard Therapy Fails in Breast Cancer: Current and Future Options for HER2-Positive Disease

The area of HER2-positive breast cancer is a rapidly changing field. The use of the humanized monoclonal antibody, trastuzumab, significantly improved the prognosis for patients with HER2-positive breast cancer, however, increasing knowledge regarding mechanisms of resistance to trastuzumab have come to light, prompting research into additional methods to target the HER2 protein. The purpose of this article is to discuss evidence for why continued blockade of the HER2 pathway continues to be important despite progression on trastuzumab, as well as to review additional HER2-targeted therapies and progression in the central nervous system. With the availability of new drugs comes the need to determine the appropriate therapeutic combinations and optimal order in which to deliver these therapies. This review summarizes the practice-changing phase III trials and some supporting phase II data regarding the various targeted HER2 therapies available for patients with advanced HER2-positive breast cancer, proposes order for anti-HER2 therapy in the advanced HER2-positive breast cancer patient, and includes information on future strategies. While other reviews on HER2-targeted therapy are available, this review specifically aims at addressing treatment options after trastuzumab failure in the patient with advanced HER2-positive breast cancer.

Phase II study evaluating lapatinib in combination with nab-paclitaxel in HER2-overexpressing metastatic breast cancer patients who have received no more than one prior chemotherapeutic regimen

Lapatinib, an oral, reversible inhibitor of epidermal growth factor receptor and human epidermal growth factor receptor 2 (HER2) tyrosine kinase, has proven antitumor activity in HER2-positive metastatic breast cancer (MBC). Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) is indicated for the treatment of breast cancer after failure of combination chemotherapy for metastatic disease or relapse within 6 months of adjuvant chemotherapy. This was an open-label, single-arm, multicenter, Phase II study to evaluate the efficacy and safety of nab-paclitaxel plus lapatinib in women with HER2 over-expressing MBC who had received no more than one prior chemotherapeutic regimen. The primary efficacy endpoint was the overall response rate (ORR). This was defined as the percentage of patients having either a complete response (CR) or partial response (PR). Secondary efficacy endpoints included progression-free survival (PFS), overall survival, duration of response (DoR), time to response (TTR), and time to progression (TTP). Investigator-assessed ORR was 53 % (n = 32, 95 % confidence interval (CI): 40.7-66.0) with the majority of patient responses demonstrating a PR (47 %). Four (7 %) patient responses demonstrated a CR, and ten (17 %) a stable disease. The median Kaplan-Meier estimate of investigator-assessed PFS, DoR, TTR, and TTP was 39.7 weeks (95 % CI 34.1-63.9), 48.7 weeks (95 % CI 31.7-57.1), 7.8 weeks (95 % CI 7.4-8.1), and 41 weeks (95 % CI 39.1-64.6), respectively. Lapatinib 1,000 mg with nab-paclitaxel 100 mg/m(2) IV is feasible with manageable and predictable toxicity and an ORR of 53 % comparing favorably with other HER2-based combinations in this setting.

New developments and future directions in systemic therapy

Adjuvant systemic therapies for breast cancer have led to a significant reduction in the risk of relapse and improvement in overall survival. However, a substantial proportion of breast cancer patients still ultimately experience relapse with metastatic disease. Here we review recent progress in trials of systemic therapies, including endocrine therapy, chemotherapy and targeted therapies for breast cancer. A current challenge for translational research is to identify drivers of resistance that may be amenable to therapy, as well as potential compensatory mechanisms that might limit the effectiveness of novel therapies. Unfortunately, not all targeted agents entering clinical trials will show sufficient efficacy to be approved for use. We highlight key findings from trials of novel agents, and the need for further research to identify biomarkers of response to systemic therapies in breast cancer.

Molecular Mechanisms of Trastuzumab-Based Treatment in HER2-Overexpressing Breast Cancer

The past decade of research into HER2-overexpressing breast cancer has provided significant insight into the mechanisms by which HER2 signaling drives tumor progression, as well as potential mechanisms by which cancer cells escape the anticancer activity of HER2-targeted therapy. Many of these preclinical findings have been translated into clinical development, resulting in novel combinations of HER2-targeted therapies and combinations of trastuzumab plus inhibitors of resistance pathways. In this paper, we will discuss proposed mechanisms of trastuzumab resistance, including epitope masking, cross signaling from other cell surface receptors, hyperactive downstream signaling, and failure to induce antibody-dependent cellular cytotoxicity. In addition, we will discuss the molecular mechanisms of action of dual HER2 inhibition, specifically the combination of trastuzumab plus lapatinib or trastuzumab with pertuzumab. We will also discuss data supporting therapeutic combinations of trastuzumab with agents targeted against molecules implicated in trastuzumab resistance. The roles of insulin-like growth factor-I receptor and the estrogen receptor are discussed in the context of resistance to HER2-targeted therapies. Finally, we will examine the major issues that need to be addressed in order to translate these combinations from the bench to the clinic, including the need to establish relevant biomarkers to select for those patients who are most likely to benefit from a particular drug combination.

Is the Improved Efficacy of Trastuzumab and Lapatinib Combination Worth the Added Toxicity? A Discussion of Current Evidence, Recommendations, and Ethical Issues Regarding Dual HER2-Targeted Therapy

Following FDA approval of trastuzumab in 1998 and lapatinib in 2007, several clinical studies have addressed the question of whether trastuzumab and lapatinib combination therapy is better than trastuzumab alone in the metastatic breast cancer and neoadjuvant setting. In this review, updated to September 2012, we focus on the relevant clinical trials that address this question and, based on the available data, reach conclusions regarding a rational and reasonably individualized approach to the management of HER2+ breast cancer. With the FDA approval of pertuzumab in June 2012 and the likely approval of T-DM1 approaching, several ethical issues overshadow the excitement oncologists have for these new treatment options. We discuss the potential evolution of highly active anti-HER2 therapy (HAAHT) as an optimal treatment paradigm for HER2+ breast cancer. Additionally, we review lessons learned from the evolution of HAART for HIV treatment.

Multifunctional nanoparticles: cost versus benefit of adding targeting and imaging capabilities

Nanoparticle-based drug delivery systems have been developed to improve the efficacy and reduce the systemic toxicity of a wide range of drugs. Although clinically approved nanoparticles have consistently shown value in reducing drug toxicity, their use has not always translated into improved clinical outcomes. This has led to the development of "multifunctional" nanoparticles, where additional capabilities like targeting and image contrast enhancement are added to the nanoparticles. However, additional functionality means additional synthetic steps and costs, more convoluted behavior and effects in vivo, and also greater regulatory hurdles. The trade-off between additional functionality and complexity is the subject of ongoing debate and the focus of this Review.

Designing immunoconjugates for cancer therapy

INTRODUCTION

Antibody-drug conjugates (ADCs), as well as antibody conjugates of protein toxins (immunotoxins) and cytokines (immunocytokines), are showing clinical efficacy, with manageable toxicities, in cancer treatment.

AREAS COVERED

The utility of an ADC is governed by the antibody and the target, as well as by the drug-linker component of the conjugate. The conjugation site, conjugating group, drug/antibody ratios and site-specific conjugation for product homogeneity are all aspects to consider in optimizing the ADC and enhancing its therapeutic window. Immunotoxin and immunocytokine construction by recombinant methods can be modulated to improve efficacy and reduce toxicity. The Dock-and-Lock (DNL) platform technology provides a flexible approach to assemble mono- or bispecific constructs carrying multiple toxin or cytokine molecules for targeted therapy.

EXPERT OPINION

Conjugation chemistry and recombinant technologies have had a significant impact on the therapeutic prospects of immunoconjugates, particularly in hematopoietic diseases. Continued concerted efforts from different scientific disciplines are needed, together with newer treatment paradigms, for greater progress in the more challenging therapy of solid tumors.

Everolimus and its role in hormone-resistant and trastuzumab-resistant metastatic breast cancer

Advances in targeted therapies have improved progression-free and overall survival in women with metastatic breast cancer; however, regardless of efficacy, resistance almost always occurs eventually. Upregulation of the PI3K/AKT/mTOR pathway, which promotes cell growth and proliferation, is a means of escaping responsiveness to hormone therapy in hormone receptor-positive disease, or trastuzumab in HER2-positive disease. Everolimus, an inhibitor of mTOR, has shown promise in early clinical trials in metastatic breast cancer and is currently being studied in larger Phase II and III clinical trials, combined with hormone therapy or trastuzumab with or without cytotoxic chemotherapy. In this article, we discuss the mechanistic and preclinical data for everolimus, efficacy and safety results of clinical trials, and the landscape looking forward.

Trastuzumab as first-line therapy in HER2-positive metastatic breast cancer patients

Trastuzumab is a humanized monoclonal antibody against the extracellular domain of hEGF receptor-2 (HER2). Trastuzumab in combination with chemotherapy has proven efficacy in treating both early and metastatic HER2-positive breast cancer. In the metastatic setting, the addition of trastuzumab to chemotherapy is associated with a statistically significant longer time to disease progression, higher rate of objective response and improvement in overall survival. Trastuzumab efficacy is not influenced by hormone receptor status, but differences in median overall survival exist between HER2-positive and HER2-negative states. Reassessment of the benefit of re-exposing patients with metastatic breast cancer to trastuzumab following relapse in the adjuvant setting is necessary. Ongoing research into new HER2-targeted therapies and trials involving combination anti-HER2 drug therapy without chemotherapy show promise. This review is focused on the available results obtained with the use of trastuzumab in the subset of HER2-positive breast cancer patients with metastatic disease.

Combined targeting of HER2 and VEGFR2 for effective treatment of HER2-amplified breast cancer brain metastases

Brain metastases are a serious obstacle in the treatment of patients with human epidermal growth factor receptor-2 (HER2)-amplified breast cancer. Although extracranial disease is controlled with HER2 inhibitors in the majority of patients, brain metastases often develop. Because these brain metastases do not respond to therapy, they are frequently the reason for treatment failure. We developed a mouse model of HER2-amplified breast cancer brain metastasis using an orthotopic xenograft of BT474 cells. As seen in patients, the HER2 inhibitors trastuzumab and lapatinib controlled tumor progression in the breast but failed to contain tumor growth in the brain. We observed that the combination of a HER2 inhibitor with an anti-VEGF receptor-2 (VEGFR2) antibody significantly slows tumor growth in the brain, resulting in a striking survival benefit. This benefit appears largely due to an enhanced antiangiogenic effect: Combination therapy reduced both the total and functional microvascular density in the brain xenografts. In addition, the combination therapy led to a marked increase in necrosis of the brain lesions. Moreover, we observed even better antitumor activity after combining both trastuzumab and lapatinib with the anti-VEGFR2 antibody. This triple-drug combination prolonged the median overall survival fivefold compared with the control-treated group and twofold compared with either two-drug regimen. These findings support the clinical development of this three-drug regimen for the treatment of HER2-amplified breast cancer brain metastases.

Targeting the human epidermal growth factor receptor 2 pathway in breast cancer

The discovery of amplification of human epidermal growth factor receptor 2 (HER2), a member of the epidermal growth factor receptor family, was an important milestone in our understanding of the biology of breast cancers. This heralded the discovery of trastuzumab, a humanized monoclonal antibody targeting HER2. Trastuzumab is the foundation of treatment of HER2-positive breast cancers, demonstrating dramatic responses in patients with metastatic disease. Unfortunately, most tumors will inevitably develop resistance to trastuzumab, necessitating the need for alternate HER2-directed therapeutic approaches. Recent advances in our understanding of the interaction between HER2 and other members of the epidermal growth factor receptor family have led to identification of newer agents, resulting in the expansion of the clinical armamentarium of available agents for the treatment of HER2-positive tumors. In this article, we review the molecular biology of the ERbb receptor family, the use of HER2-targeted agents in early and advanced breast cancer, and the next-generation anti-HER2 agents that are currently in clinical evaluation.

Targeted treatments of HER2-positive metastatic breast cancer: trastuzumab and beyond

SUMMARY HER2 positivity defines a molecular subtype of breast cancer with aggressive biological behavior. HER2 has been clinically validated as a prominent therapeutic target in breast cancer, and an abundance of data from clinical trials proving the efficacy of trastuzumab, a humanized anti-HER2 monoclonal antibody, has changed the natural history of this disease. Despite positive results from many trials, resistance to anti-HER2 agents inevitably occurs in both the metastatic and adjuvant settings. This clinical reality has led to the development of various other targeted agents designed to block the HER2 receptor. Similarly, attempts to elucidate the molecular mechanisms of resistance to the already established anti-HER2 agents have opened new therapeutic avenues with numerous promising agents. This review presents a comprehensive overview of the data available on anti-HER2-targeted agents other than trastuzumab, and describes both challenges and directions for the future.

Lapatinib, trastuzumab or the combination added to preoperative chemotherapy for breast cancer: a meta-analysis of randomized evidence

We compared the efficacy and safety of the addition of lapatinib versus trastuzumab or their combination to neoadjuvant chemotherapy in HER2-positive breast cancer. Potentially eligible trials were located through PubMed and Cochrane Library searches and abstracts of major international conferences. The endpoints that we assessed were pathologic complete response (pCR) rate, and toxicity. Pooled risk ratios (RR) were estimated for each endpoint with fixed or random effects models, depending on between studies heterogeneity. Six trials were identified with 1,494 eligible patients. The probability to achieve pCR was higher for the trastuzumab plus chemotherapy arm versus lapatinib plus chemotherapy (RR 1.25, 95 % confidence interval [CI] 1.08-1.43; p = 0.003) (6 trials; 1,494 patients). Probability to pCR was significantly higher in the group receiving lapatinib and trastuzumab than in the group with trastuzumab alone (RR 1.39, 95 % CI 1.20-1.63; p < 0.001) (4 trials; 779 patients). Grade III-IV diarrhea and dermatologic toxicities were statistically more frequent in patients receiving lapatinib. No differences were observed regarding cardiac adverse events among patients receiving trastuzumab, lapatinib, or their combination. These data supports the superiority of a dual-HER2 inhibition for the treatment of HER2-positive breast cancer in the neoadjuvant setting. The direct comparison of trastuzumab and lapatinib showed that lapatinib is inferior in terms of pCR and associated with a higher risk for toxicity.