Trastuzumab emtansine for HER2-positive advanced breast cancer

Preclinical safety profile of trastuzumab emtansine (T-DM1): mechanism of action of its cytotoxic component retained with improved tolerability

Trastuzumab emtansine (T-DM1) is the first antibody-drug conjugate (ADC) approved for patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic breast cancer. The therapeutic premise of ADCs is based on the hypothesis that targeted delivery of potent cytotoxic drugs to tumors will provide better tolerability and efficacy compared with non-targeted delivery, where poor tolerability can limit efficacious doses. Here, we present results from preclinical studies characterizing the toxicity profile of T-DM1, including limited assessment of unconjugated DM1. T-DM1 binds primate ErbB2 and human HER2 but not the rodent homolog c-neu. Therefore, antigen-dependent and non-antigen-dependent toxicity was evaluated in monkeys and rats, respectively, in both single- and repeat-dose studies; toxicity of DM1 was assessed in rats only. T-DM1 was well tolerated at doses up to 40 mg/kg (~4400 μg DM1/m(2)) and 30 mg/kg (~ 6000 μg DM1/m(2)) in rats and monkeys, respectively. In contrast, DM1 was only tolerated up to 0.2mg/kg (1600 μg DM1/m(2)). This suggests that at least two-fold higher doses of the cytotoxic agent are tolerated in T-DM1, supporting the premise of ADCs to improve the therapeutic index. In addition, T-DM1 and DM1 safety profiles were similar and consistent with the mechanism of action of DM1 (i.e., microtubule disruption). Findings included hepatic, bone marrow/hematologic (primarily platelet), lymphoid organ, and neuronal toxicities, and increased numbers of cells of epithelial and phagocytic origin in metaphase arrest. These adverse effects did not worsen with chronic dosing in monkeys and are consistent with those reported in T-DM1-treated patients to date.

A novel anti-CD37 antibody-drug conjugate with multiple anti-tumor mechanisms for the treatment of B-cell malignancies

CD37 has gathered renewed interest as a therapeutic target in non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL); however, CD37-directed antibody-drug conjugates (ADCs) have not been explored. Here, we identified a novel anti-CD37 antibody, K7153A, with potent in vitro activity against B-cell lines through multiple mechanisms including apoptosis induction, antibody-dependent cellular cytotoxicity, antibody-dependent cellular phagocytosis, and complement-dependent cytotoxicity. The antibody was conjugated to the maytansinoid, DM1, a potent antimicrotubule agent, via the thioether linker, N-succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate (SMCC), and the resulting ADC, IMGN529, retained the intrinsic antibody activities and showed enhanced cytotoxic activity from targeted payload delivery. In lymphoma cell lines, IMGN529 induced G2/M cell cycle arrest after internalization and lysosomal processing to lysine-N(ε)-SMCC-DM1 as the sole intracellular maytansinoid metabolite. IMGN529 was highly active against subcutaneous B-cell tumor xenografts in severe combined immunodeficient mice with comparable or better activity than rituximab, a combination of cyclophosphamide, vincristine, and prednisone, or bendamustine. In human blood cells, CD37 is expressed in B cells at similar levels as CD20, and IMGN529 resulted in potent and specific depletion of normal and CLL B cells. These results support evaluation of the CD37-targeted ADC, IMGN529, in clinical trials in patients with B-cell malignancies including NHL and CLL.

Time to stop operating on breast cancer patients with pathological complete response?

Surgery is an obligatory component of treatment for early breast cancer. The last 20 years developments in systemic neoadjuvant therapy have progressively increased pathological complete response (pCR). Pathological complete response is associated with excellent prognosis especially for hormone receptor negative cancers. Therapeutic advances and recognition of the importance of pathological subtype in predicting pCR facilitate identification of subgroups with very high pCR rates. Treatment of HER2 positive hormone receptor negative cancers with combination chemotherapy and multiple targeted anti-HER2 agents results in consistently high pCR rates of 60-83%. Routine surgery in this setting where most patients have no potential to benefit is of questionable value and the option of omitting surgery in these patients should now be explored in a randomized trial. For HER2 positive disease not achieving pCR after neoadjuvant treatment the outcomes are poor. Trials are underway to determine if outcomes for these patients can be improved with alternative targeted therapy.

Patient-derived xenografts, the cancer stem cell paradigm, and cancer pathobiology in the 21st century

Cancer is a heterogeneous disease manifest in many forms. Tumor histopathology can differ significantly among patients and cellular heterogeneity within tumors is common. A primary goal of cancer biologists is to better understand tumorigenesis and cancer progression; however, the complex nature of tumors has posed a substantial challenge to unlocking cancer's secrets. The cancer stem cell (CSC) paradigm for the pathobiology of solid tumors appropriately acknowledges phenotypic and functional tumor cell heterogeneity observed in solid tumors and accounts for the disconnect between drug approval based on response and the general inability of approved therapies to meaningfully impact survival due to their failure to eradicate these most important of cellular targets. First proposed to exist decades ago, CSC have only recently begun to be precisely identified due to technical advancements that facilitate identification, isolation, and interrogation of distinct tumor cell subpopulations with differing ability to form and perpetuate tumors. Precise identification of CSC populations and the complete hierarchy of cells within solid tumors will facilitate more accurate characterization of patient subtypes and ultimately contribute to more personalized and effective therapies. Rapid advancement in the understanding of tumor biology as it exists in patients requires cooperation among institutions, surgeons, pathologists, cancer biologists and patients alike, primarily because this translational research is best done with patient-derived tissue grown in the xenograft setting as patient-derived xenografts. This review calls for a broader change in the approaches taken to study cancer pathobiology, highlights what implications the CSC paradigm has for pathologists and cancer biologists alike, and calls for greater collaboration between institutions, physicians and scientists in order to more rapidly advance our collective understanding of cancer.

pH-Responsive Theranostic Polymer-Caged Nanobins (PCNs): Enhanced Cytotoxicity and T1 MRI Contrast by Her2-Targeting

A PCN theranostic platform comprises a doxorubicin (DXR)-loaded liposomal core and an acid-sensitive polymer shell that is functionalized with Herceptin and Gd^III-based MRI contrast agents. In vitro testing reveals a 14-fold increase in DXR-based cytotoxicity versus a non-targeted analogue and an 120-fold improvement in cellular Gd^III-uptake in comparison with clinically approved DOTA-Gd^III, leading to significant T₁ MRI contrast enhancement.

Ado-Trastuzumab Emtansine and Radium 223 Dichloride

The complexity of cancer chemotherapy requires pharmacists be familiar with the complicated regimens and highly toxic agents used. This column reviews various issues related to preparation, dispensing, and administration of antineoplastic therapy, and the agents, both commercially available and investigational, used to treat malignant diseases.

Targeted therapy for breast cancer

Breast cancer is a heterogeneous group of diseases that are clinically subdivided as hormone receptor-positive, human epidermal growth factor receptor 2-positive (HER2(+)), and triple-negative breast cancer, to guide therapeutic interventions. Agents that target estrogen receptor (ER) and HER2 are among the most successful cancer therapeutics. However, de novo or acquired resistance is common, despite the development of newer agents against these pathways. As our understanding of tumor biology improves, novel targets are being identified. Notably, inhibitors against several pathways [including, among others, the phosphoinositide 3-kinase/mammalian target of rapamycin (PI3K/mTOR), cell-cycle regulation, heat shock protein, and epigenetic pathways] have demonstrated promising activity in clinical trials, and the mTOR-inhibitor everolimus has been approved for advanced or metastatic aromatase inhibitor-resistant ER(+) breast cancer. At present, there are no established targeted agents for triple-negative breast cancer (negative ER, progesterone receptor, and HER2). Although poly(ADP-ribose) polymerase inhibitors have shown promising activity in BRCA-related cancers, its value in the treatment of triple-negative breast cancers remains to be demonstrated. In this Review, we present a basic understanding of the major targeted agents in current practice and under development for the treatment of breast cancer in the context of the three clinical subgroups.

Changing T-cell enigma: cancer killing or cancer control?

Data from different laboratories and theoretical considerations challenge our current view on anticancer immunity. Immune cells are capable of destroying cancer cells under in vitro and in vivo conditions. Therefore, cellular immunity is considered to control cancers through mechanisms that kill cancers. Yet, therapeutic anticancer immune responses rarely delete cancers. If efficient, they rather establish a life with stable disease. This raises the question of whether killing is the sole mechanism by which immune therapy attacks cancers. Here, we show that, besides cancer eradication by cytotoxic lymphocytes, other modes of action are operative and strictly required for cancer control. We show that T helper-1 cells arrest cancer growth by driving cancers into a state of stable or permanent growth arrest, called senescence. Such immune cells establish cytokine-producing walls around developing cancers. When producing interferon-γ and tumor necrosis factor, this cytokine-induced tumor immune-surveillance keeps the cancer cells in a permanently non-proliferating state. Simultaneously, antiangiogenic chemokines cut their connections to the surrounding tissues. This strategy significantly reduces tumor burden and prolongs life of cancer-bearing animals. As human cancers also undergo senescence, the current data suggest tumor-immune surveillance through cytokine-induced senescence, instead of tumor eradication, as the more realistic and primary goal of cancer control.

Tubulin: an example of targeted chemotherapy

Anticancer drugs directed against the microtubule, including taxanes and vinca alkaloids, have been the backbone of many chemotherapy regimes for decades. These drugs have, however, significant limitations, which have prompted the development of novel microtubule targeting agents (MTAs). This article will discuss MTAs for anticancer therapies and recent debates regarding their mechanisms of action. Furthermore, the limitations of taxanes, including hypersensitivity reactions, neurotoxicity, drug resistance and lack of validated biomarkers to guide therapy will be discussed, all of which have driven the development of novel agents. The mechanisms of action and drug development of new generations of MTAs will also be outlined. Agents demonstrating utility in Phase III clinical trials, including eribulin, ixabepilone, cabazitaxel and trastuzumab-DM1 will be highlighted, as well as novel agents currently in development and future directions for MTAs.

External Quality Assessment (EQA) program for the preanalytical and analytical immunohistochemical determination of HER2 in breast cancer: an experience on a regional scale

BACKGROUND

An External Quality Assessment (EQA) program was developed to investigate the state of the art of HER2 immunohistochemical determination in breast cancer (BC) in 16 Pathology Departments in the Lazio Region (Italy). This program was implemented through two specific steps to evaluate HER2 staining (step 1) and interpretation (step 2) reproducibility among participants.

METHODS

The management activities of this EQA program were assigned to the Coordinating Center (CC), the Revising Centers (RCs) and the Participating Centers (PCs). In step 1, 4 BC sections, selected by RCs, were stained by each PC using their own procedures. In step 2, each PC interpreted HER2 score in 10 BC sections stained by the CC. The concordance pattern was evaluated by using the kappa category-specific statistic and/or the weighted kappa statistic with the corresponding 95% Jackknife confidence interval.

RESULTS

In step 1, a substantial/almost perfect agreement was reached between the PCs for scores 0 and 3+ whereas a moderate and fair agreement was observed for scores 1+ and 2+, respectively.In step 2, a fully satisfactory agreement was observed for 6 out of the 16 PCs and a quite satisfactory agreement was obtained for the remaining 10 PCs.

CONCLUSIONS

Our findings highlight that in the whole HER2 evaluation process the two intermediate categories, scores 1+ and 2+, are less reproducible than scores 0 and 3+. These findings are relevant in clinical practice where the choice of treatment is based on HER2 positivity, suggesting the need to share evaluation procedures within laboratories and implement educational programs.

Immunotherapeutic strategies to target prognostic and predictive markers of cancer

Throughout the last century medical advances in cancer treatment in the fields of surgery, radiation therapy and chemotherapy have greatly impacted patients' survival rates. Nevertheless, cancer remains a significant cause of mortality, with an estimated 7.6 million deaths worldwide in 2008, reflecting the inability of existing therapies to effectively cure disease. The emergence of vaccines and their successes in preventing the spread of infectious diseases has demonstrated the unique specificity and therapeutic potential of the immune system. This potential has driven the development of novel cancer immunotherapeutics. This review focuses on the current status of the use of immunologic effectors to target known biomarkers in cancer.

Pertuzumab: optimizing HER2 blockade

Pertuzumab has been approved by the U.S. Food and Drug Administration for use in combination with trastuzumab and docetaxel for the first-line treatment of patients with advanced HER2-positive (HER2(+)) breast cancer. Pertuzumab is a recombinant humanized monoclonal antibody that binds to the extracellular dimerization domain II of HER2 and inhibits heterodimerization of HER2 with other HER family members, including EGF receptor (EGFR), HER3, and HER4. The HER2-HER3 heterodimer is a robust activator of phosphoinositide 3-kinase (PI3K) pathway signaling and functions as the most transforming and mitogenic of the receptor complexes formed by the HER family of proteins; thus, blockade of HER2-HER3 likely represents the most relevant action of pertuzumab. In the seminal phase III study, patients with HER2(+) metastatic breast cancer were randomized to receive trastuzumab and docetaxel, with or without pertuzumab: Addition of pertuzumab significantly prolonged progression-free survival with an increase of 6.1 months (12.4 vs. 18.5 months, respectively). In a subsequent analysis with 30 months of median follow-up, pertuzumab conferred a 34% reduction in the risk of mortality. Here, we review the mechanism of action of pertuzumab, the rationale for combining it with trastuzumab/pertuzumab, clinical data, and future directions for this work.

A HER2-targeted RNA aptamer molecule labeled with 99mTc for single-photon imaging in malignant tumors

A modified RNA aptamer with HER2-specific binding was conjugated to hynic and labeled with (99m)Tc, for potential use as a radiopharmaceutical for diagnostic imaging of ovarian cancer cells (SKOV-3) with high HER2 expression. The aptamer was radiolabeled with (99m)Tc by using hynic as the chelator and tricine as the co-ligand. Stability testing of the radioconjugated aptamer was performed via ITLC and SDS-PAGE in normal saline and serum. The aptamer-radionuclide conjugate was evaluated for cellular HER2-specific binding, saturation affinity, and cellular internalization in SKOV-3 and MCF-7 cells, and its biodistribution properties were assessed in normal and SKOV-3 tumor-bearing mice. Radiolabeling of the aptamer was achieved with high yield and radiochemical purity, and the (99m)Tc-hynic-RNA aptamer was highly stable in normal saline and serum. Cellular experiments showed specific binding of the aptamer to the HER2 receptor with a dissociation constant of 27 nM. Rapid blood clearance was observed after injection of the (99m)Tc-hynic-RNA aptamer, and the main excretion route was via the hepatobilary system. While the radioconjugated aptamer bound specifically to the HER2 receptor on cells in vitro, it did not show any significant tumor-to-blood or tumor-to-muscle ratios in mice. Modifications to radiolabeled aptamer will require improving its pharmacokinetic properties and tumor uptake in vivo.

Emerging targeted combinations in the management of breast cancer

The number of targeted treatments has risen exponentially over the last few years and is an important concept in the fight against cancer. This review will concentrate on some of the main treatments targeting aberrant pathways which have been tested mainly in the Phase I/II setting. These include human epidermal growth factor receptor 2 inhibitors, drug-antibody conjugates, epidermal growth factor receptor inhibitors, vascular endothelial growth factor inhibitors, reticular activating system, mammalian target of rapamycin and multi-kinase inhibitors. Further knowledge of these pathways and the predictors of response to them will enable personalized medicine to become a reality.

MSCs: Delivery Routes and Engraftment, Cell-Targeting Strategies, and Immune Modulation

Mesenchymal stem cells (MSCs) are currently being widely investigated both in the lab and in clinical trials for multiple disease states. The differentiation, trophic, and immunomodulatory characteristics of MSCs contribute to their therapeutic effects. Another often overlooked factor related to efficacy is the degree of engraftment. When reported, engraftment is generally low and transient in nature. MSC delivery methods should be tailored to the lesion being treated, which may be local or systemic, and customized to the mechanism of action of the MSCs, which can also be local or systemic. Engraftment efficiency is enhanced by using intra-arterial delivery instead of intravenous delivery, thus avoiding the "first-pass" accumulation of MSCs in the lung. Several methodologies to target MSCs to specific organs are being developed. These cell targeting methodologies focus on the modification of cell surface molecules through chemical, genetic, and coating techniques to promote selective adherence to particular organs or tissues. Future improvements in targeting and delivery methodologies to improve engraftment are expected to improve therapeutic results, extend the duration of efficacy, and reduce the effective (MSC) therapeutic dose.

Cardiotoxicity of novel HER2-targeted therapies

BACKGROUND

Trastuzumab, an anti-HER2 humanized monoclonal antibody, is the standard treatment for both early and metastatic HER2-positive breast cancer. In addition to other chemotherapeutic agents, trastuzumab significantly improves response rate and survival in HER2-positive early and metastatic breast cancer. Although it is well known that trastuzumab therapy is closely associated with both symptomatic and asymptomatic cardiotoxicity, less is known about novel HER2-targeted therapies. The aim of this review is to discuss the cardiac safety data from recent studies of novel anti-HER2 drugs other than trastuzumab.

SCOPE

Novel HER2-targeted therapies showed favorable results in HER2 positive metastatic breast cancer patients. Pubmed database, ASCO and San Antonio Breast Cancer Symposium Meeting abstracts were searched until January 2013 using the following search keywords; 'trastuzumab, trastuzumab cardiotoxicity, HER-2 targeted therapies, lapatinib, pertuzumab, trastuzumab emtansine, afatinib and neratinib'; papers which were considered relevant for the aim of this review were selected by the authors. Lapatinib, pertuzumab, T-DM1, neratinib and afatinib molecules are evaluated in the study.

FINDINGS

In a comprehensive analysis, 3689 lapatinib treated patients enrolled in 49 trials; asymptomatic cardiac events were reported in 53 patients (1.4%) and symptomatic grade III and IV systolic dysfunction was observed only in 7 patients (0.2%) treated with lapatinib. In phase I-III trials of pertuzumab, cardiac dysfunction was seen in 4.5-14.5% of patients with pertuzumab treatment and cardiac dysfunction was usually grade I and II. Cardiotoxicity of pertuzumab was usually reported with the trastuzumab combination and no additive cardiotoxicity was reported with addition of pertuzumab to trastuzumab. T-DM1 had a better safety profile compared to trastuzumab, no significant cardiotoxicity was observed with T-DM1 in heavily pre-treated patients. In the EMILIA study, only in 1.7% of patients in the T-DM1 group experienced reduction of left ventricular ejection fraction (LVEF) and grade III LVEF reduction developed only in one patient (0.2%) in the T-DM1 group compared to the lapatinib plus capacitabine group. In phase I-II trials with neratinib no cardiotoxicity was reported whereas cardiotoxicity was seen between 0-5.3% with afatinib treatment.

CONCLUSION

Although cardiac toxicity has been reported as an adverse event for novel HER2-targeted therapies, cardiac dysfunction rate of the novel HER2-targeted therapies is significantly lower than the trastuzumab and combination of these agents with trastuzumab did not significantly increase the cardiac adverse events.

Drug-conjugated antibodies for the treatment of cancer

Despite considerable effort, application of monoclonal antibody technology has had only modest success in improving treatment outcomes in patients with solid tumours. Enhancing the cancer cell-killing activity of antibodies through conjugation to highly potent cytotoxic 'payloads' to create antibody-drug conjuates (ADCs) offers a strategy for developing anti-cancer drugs of great promise. Early ADCs exhibited side-effect profiles similar to those of 'classical' chemotherapeutic agents and their performance in clinical trials in cancer patients was generally poor. However, the recent clinical development of ADCs that have highly potent tubulin-acting agents as their payloads have profoundly changed the outlook for ADC technology. Twenty-five such ADCs are in clinical development and one, brentuximab vedotin, was approved by the FDA in August, 2011, for the treatment of patients with Hodgkin's lymphoma and patients with anaplastic large cell lymphoma, based on a high rate of durable responses in single arm phase II clinical trials. More recently, a second ADC, trastuzumab emtansine, has shown excellent anti-tumour activity with the presentation of results of a 991-patient randomized phase III trial in patients with HER2-positive metastatic breast cancer. Treatment with this ADC (single agent) resulted in a significantly improved progression-free survival of 9.6 months compared with 6.4 months for lapatinib plus capecitabine in the comparator arm and significantly prolonged overall survival. Besides demonstrating excellent efficacy, these ADCs were remarkably well tolerated. Thus these, and other ADCs in development, promise to achieve the long sought goal of ADC technology, that is, of having compounds with high anti-tumour activity at doses where adverse effects are generally mild.

Primer on tumor immunology and cancer immunotherapy

Individualized cancer therapy is a central goal of cancer biologists. Immunotherapy is a rational means to this end—because the immune system can recognize a virtually limitless number of antigens secondary to the biology of genetic recombination in B and T lymphocytes. The immune system is exquisitely structured to distinguish self from non-self, as demonstrated by anti-microbial immune responses. Moreover the immune system has the potential to recognize self from “altered-self”, which is the case for cancer. However, the immune system has mechanisms in place to inhibit self-reactive responses, many of which are usurped by evolving tumors. Understanding the interaction of cancer with the immune system provides insights into mechanisms that can be exploited to disinhibit anti-tumor immune responses. Here, we summarize the 2012 SITC Primer, reviewing past, present, and emerging immunotherapeutic approaches for the treatment of cancer—including targeting innate versus adaptive immune components; targeting and/or utilizing dendritic cells and T cells; the role of the tumor microenvironment; and immune checkpoint blockade.

Breast cancer metastasis: issues for the personalization of its prevention and treatment

Despite important progress in adjuvant and neoadjuvant therapies, metastatic disease often develops in breast cancer patients and remains the leading cause of their deaths. For patients with established metastatic disease, therapy is palliative, with few breaks and with mounting adverse effects. Many have hypothesized that a personalized or precision approach (the terms are used interchangeably) to cancer therapy, in which treatment is based on the individual characteristics of each patient, will provide better outcomes. Here, we discuss the molecular basis of breast cancer metastasis and the challenges in personalization of treatment. The instability of metastatic tumors remains a leading obstacle to personalization, because information from a patient's primary tumor may not accurately reflect the metastasis, and one metastasis may vary from another. Furthermore, the variable presence of tumor subpopulations, such as stem cells and dormant cells, may increase the complexity of the targeted treatments needed. Although molecular signatures and circulating biomarkers have been identified in breast cancer, there is lack of validated predictive molecular markers to optimize treatment choices for either prevention or treatment of metastatic disease. Finally, to maximize the information that can be obtained, increased attention to clinical trial design in the metastasis preventive setting is needed.

Bayesian mixture models for assessment of gene differential behaviour and prediction of pCR through the integration of copy number and gene expression data

We consider modeling jointly microarray RNA expression and DNA copy number data. We propose Bayesian mixture models that define latent Gaussian probit scores for the DNA and RNA, and integrate between the two platforms via a regression of the RNA probit scores on the DNA probit scores. Such a regression conveniently allows us to include additional sample specific covariates such as biological conditions and clinical outcomes. The two developed methods are aimed respectively to make inference on differential behaviour of genes in patients showing different subtypes of breast cancer and to predict the pathological complete response (pCR) of patients borrowing strength across the genomic platforms. Posterior inference is carried out via MCMC simulations. We demonstrate the proposed methodology using a published data set consisting of 121 breast cancer patients.

The success story of trastuzumab emtansine, a targeted therapy in HER2-positive breast cancer

Trastuzumab emtansine is a unique antibody-drug conjugate targeting selectively human epidermal growth factor receptor 2 (HER2)-positive breast cancer cells, thus conferring high efficacy with minimal systemic toxicities. Trastuzumab emtansine consists of a monoclonal antibody trastuzumab and potent cytotoxic agent DM1, combined together through a stable thioether bond. First-in-man phase I study set the maximum tolerated dose at 3.6 mg/kg given intravenously on a 3-weekly regimen. In phase II studies, trastuzumab emtansine at 3.6 mg/kg provided objective tumour responses and clinical benefit with an encouraging safety profile. Over these studies, trastuzumab emtansine had favourable pharmacokinetics. No accumulation of trastuzumab emtansine or catabolites was observed even after repeated dosing and free DM1 was very low in circulation. The stability of trastuzumab emtansine in circulation justifies the minimal systemic toxicity observed. Recently, a randomised international open-label phase III study confirmed the efficacy and safety of trastuzumab emtansine versus lapatinib plus capecitabine in patients with HER2-positive locally advanced or metastatic breast cancer. Overall survival was significantly improved in the trastuzumab emtansine arm. Safety outcomes were also favourable. The adverse events traditionally related to chemotherapy were markedly lower or absent with trastuzumab emtansine. Cardiotoxicity, frequently observed in HER2-directed therapy, was not reported. Although thrombocytopenia and elevations in hepatic enzymes were reported with trastuzumab emtansine, these events were reversible and manageable. Ongoing trials investigating trastuzumab emtansine as a single-agent or in combination with other agents, will determine the place of trastuzumab emtansine in the current therapeutic strategies deployed for HER2-metastatic breast cancer.

Emerging strategies for the dual inhibition of HER2-positive breast cancer

PURPOSE OF REVIEW

To review the recently published trials to help us refine and optimize the use of approved HER2-targeted agents (trastuzumab and lapatinib) and highlight future combination strategies for the treatment of HER2-positive breast cancer.

RECENT FINDINGS

Pertuzumab, which prevents the dimerization of HER2/HER3, and trastuzumab emtansine (T-DM1), a novel antibody drug conjugate (trastuzumab joined via a stable linker to a derivative of the potent cytotoxic agent maytansine), have both demonstrated promising clinical activity in HER2-positive breast cancer. Dual anti-HER2 regimens combining trastuzumab with lapatinib or pertuzumab show remarkable synergy and improved outcomes in patients previously thought to have refractory disease. In the neoadjuvant setting, dual anti-HER2 blockade and chemotherapy have almost doubled the rates of pathologic complete response compared to single anti-HER2 therapy. A better understanding of the mechanisms of resistance has led to the development of rational combination therapies cotargeting the PI3K and vascular endothelial growth factor signaling pathways.

SUMMARY

New therapeutic options such as pertuzumab or T-DM1 will yield clinically meaningful improvements for patients with HER2-positive breast cancer. Given the high prevalence of intrinsic and acquired resistance to single-agent regimens, the treatment paradigm is shifting toward a dual anti-HER2 therapeutic approach.

Companion diagnostics in oncology - current status and future aspects

A large number of targeted anticancer drugs are currently under development and most of them will have a companion diagnostic linked to their use. If a diagnostic assay is developed in conjunction with a targeted anticancer drug, such an assay will later end up determining the conditions for the use of the drug after its approval. The assay then becomes a kind of 'gatekeeper' in relation to which patients should be treated with the drug in question. This 'gatekeeper' role implies that companion diagnostic assays must live up to the same regulatory standards and requirements known from drug development. The assays must have proven to be analytically robust and reliable and to have demonstrated clinical utility before they are routinely used in the clinic. In the drug-diagnostic codevelopment model, several 'traditional' study designs have been used to demonstrate clinical utility. However, if we are to benefit from the increasing knowledge provided by molecular oncology, new ways should be developed to demonstrate the clinical utility of drug-diagnostic combinations. The development of such an approach will require a rethinking at different levels and is likely to include a number of ethical, regulatory and practical challenges.

Use of pertuzumab for the treatment of HER2-positive metastatic breast cancer

INTRODUCTION

Targeting the human epidermal growth factor receptor (HER) family of tyrosine kinase receptors has proven to be effective as a therapeutic strategy for HER type 2 (HER2)-positive breast cancer. Since resistance to trastuzumab occurs relatively frequently, particularly in the metastatic setting, novel anti-HER2 targeted therapies with complementary and/or synergistic mechanisms of action have been under development. Pertuzumab, a HER2-targeted monoclonal antibody that prevents HER2 dimerisation, is the first of a class of promising targeted agents for the treatment of HER2-positive breast cancer.

METHODS

A review of the biomedical literature published prior to February 2013 was conducted in English using PubMed. ClinicalTrials.gov was searched for appropriate clinical trials. The search terms used included breast neoplasm, pertuzumab, dimerisation, and HER2-positive. Abstracts of studies presented at the ASCO and ESMO Annual Meetings, and San Antonio Breast Cancer Symposium were also included.

RESULTS

Pertuzumab represents a novel anti-HER2 targeted therapy for HER2-positive breast cancers. In this article, we describe the mechanism of action of pertuzumab, as well as its drug development process and preclinical testing results. Based on the results of ancillary studies, dual inhibition using pertuzumab and trastuzumab was shown to be effective for the management of HER2-positive metastatic breast cancers pre-treated with trastuzumab-based therapy. For the first-line setting, the combination of both pertuzumab and trastuzumab with docetaxel (CLEOPATRA trial; clinical evaluation of pertuzumab and trastuzumab) has changed the paradigm of patient management.

CONCLUSION

Pertuzumab provided a more comprehensive inhibition of HER2-driven signalling pathways. When administered together with trastuzumab, pertuzumab represent a significant advancement for the treatment of HER2-positive metastatic breast cancer patients.

Active immunotherapy in HER2 overexpressing breast cancer: current status and future perspectives

BACKGROUND

The use of anti-HER2 monoclonal antibodies (mAbs) has improved the clinical outcome of HER2-overexpressing breast cancers (BCs). Unfortunately, often these tumors tend to relapse and, when metastatic, the duration of clinical benefit is limited over time and almost invariably followed by tumor progression. Alternative approaches to this essentially passive immunotherapy are therefore needed in HER2-overexpressing BC patients. As HER2 is one of the most suitable targets for active immunotherapy in BC, manipulating the immune system is a highly attractive approach.

MATERIAL AND METHODS

A computer-based literature search was carried out using PubMed (keywords: breast neoplasm, HER2 vaccine, immunology); data reported at international meetings were included.

RESULTS

This review provides a focus on the following active vaccinal approaches under clinical investigation against HER2-overexpressing BC: (i) peptide and protein based; (ii) DNA based; (iii) whole tumor cell based; (iv) dendritic cell based. Moreover, the review discuss future challenges in the field, trying to define the best setting for the development of this innovative strategy, considering both immunological and clinical aspects of HER2 targeting.

CONCLUSIONS

Development of effective vaccines for BC remains a distinct challenge but is likely to become a substantial advance for patients with HER2-overexpressing BCs.

MSP-RON signalling in cancer: pathogenesis and therapeutic potential

Since the discovery of MSP (macrophage-stimulating protein; also known as MST1 and hepatocyte growth factor-like (HGFL)) as the ligand for the receptor tyrosine kinase RON (also known as MST1R) in the early 1990s, the roles of this signalling axis in cancer pathogenesis has been extensively studied in various model systems. Both in vitro and in vivo evidence has revealed that MSP-RON signalling is important for the invasive growth of different types of cancers. Currently, small-molecule inhibitors and antibodies blocking RON signalling are under investigation. Substantial responses have been achieved in human tumour xenograft models, laying the foundation for clinical validation. In this Review, we discuss recent advances that demonstrate the importance of MSP-RON signalling in cancer and its potential as a therapeutic target.

Breast cancer, version 3.2013: featured updates to the NCCN guidelines

These NCCN Guidelines Insights highlight the important updates specific to the management of HER2-positive metastatic breast cancer in the 2013 version of the NCCN Clinical Practice Guidelines in Oncology for Breast Cancer. These include new first-line and subsequent therapy options for patients with HER2-positive metastatic breast cancer.

Regulation of Apoptosis by HER2 in Breast Cancer

HER2 is a trans-membrane receptor tyrosine kinase that activates multiple growth-promoting signaling pathways including PI3K-AKT and Ras-MAPK. Dysregulation of HER2 is a frequent occurrence in breast cancer that is associated with poor patient outcomes. A primary function of HER2 is suppressing apoptosis to enhance cell survival giving rise to uncontrolled proliferation and tumor growth. There has been much investigation into the mechanisms by which apoptosis is suppressed by HER2 in hopes of finding clinical targets for HER2-positive breast cancers as these cancers often become resistant to therapies that directly target HER2. Several apoptotic mechanisms have been shown to be deregulated in HER2-overexpressing cells with examples in both the intrinsic and extrinsic apoptotic pathways. HER2-mediated activation of PI3K-AKT signaling is required for many of the mechanisms HER2 uses to suppress apoptosis. HER2 overexpression is correlated with increases in anti-apoptotic Bcl-2 proteins including Bcl-2, Bcl-xL, and Mcl-1. HER2 also suppresses p53-mediated apoptosis by upregulation of MDM2 by activation of AKT. In addition, survivin expression is often increased with HER2 overexpression leading to inhibition of caspase activation. There is also recent evidence to suggest HER2 can directly influence apoptosis by translocation to the mitochondria to inhibit cytochrome c release. HER2 can also suppress cellular reaction to death ligands, especially TRAIL-induced apoptosis. Elucidation of the mechanisms of apoptotic suppression by HER2 suggest that clinical treatment will likely need to target multiple components of these pathways as there is redundancy in HER2-mediated cell survival. Several therapies have attempted to target Bcl-2 proteins that have promising pre-clinical results. Next-generation HER2 targeting therapies include irreversible pan-ERBB inhibitors and antibody-drug conjugates, such as T-DM1 that has very promising clinical results thus far. Further investigation should include elucidating mechanisms of resistance to HER2-targeted therapies and targeting of multiple components of HER2-mediated cell survival.

Challenges in the treatment of older breast cancer patients

As the population ages, oncologists will be faced with managing an exploding number of older patients with breast cancer. The primary challenge of caring for older cancer patients is providing treatment options that maximize long-term survival while accounting for comorbidities, life expectancy, and effects of treatment. There is a paucity of data from trials on the risks and benefits of effective treatments in elderly breast cancer patients. This article discusses how to evaluate older breast cancer patients and provides guidelines for optimal therapies in the adjuvant and metastatic treatment settings.

Targeted therapies of solid cancers: new options, new challenges

PURPOSE OF REVIEW

The landscape of medical oncology is filled with approvals of new anticancer agents, the majority of which are targeted agents. This shift in therapies raises multiple challenges including the appearance of new toxicities, the need for biomarkers, the emergence of genomics and the evolution of cancer molecular imaging.

RECENT FINDINGS

Biopsy of metastatic lesions is slowly becoming a standard of care before the initiation of any therapy. These invasive procedures have been found to be generally well tolerated and are being put to use with the emergence of genomics. Gene sequencing and new imaging techniques are serving the understanding of tumor biology and the search for 'biomarkers' predicting response and resistance to treatment. New clinical trial designs incorporating the 'presumed' biomarkers are guiding patients to specific treatments and have shown outcome improvements.

SUMMARY

Many questions remain however unanswered and new challenges appear. Intratumor heterogeneity emerges as a brake to personalized cancer care. Relevant targets remain undruggable and costs may hinder progress. Furthermore, technical issues continue to arise. The ultimate goal remains to achieve cure by blocking the multiple pathways of cancer development and proliferation, while sparing the patients the burden of therapy.

Targeted therapy for HER2 positive breast cancer

INTRODUCTION

Breast cancer is the second most common cause of death for women behind lung cancer and the most common cause of cancer deaths for women aged 45-55 years old (CDC.gov 2012). Although there continue to be enormously large numbers of disease incidence, deaths have been declining due to the disease with two hallmark time frames. The first occurred during the mid to late 1980's when hormonal therapy was introduced as a treatment for ER/PR positive breast cancer. The second occurred in the late 1990's when trastuzumab was introduced in treating HER2 positive breast cancer. These remarkable accomplishments in developing novel targeted therapies for breast cancer, along with a better understanding of the disease biology have improved disease outcome over the past 20 years.This article reviews the data presented at 2012 American Society of Clinical Oncology and 2012 San Antonio Breast Cancer Symposium regarding progress made in the field of HER2 positive breast cancer and examines the future of HER2 targeted therapy.

Anti-tumor activity of a novel monoclonal antibody, NPC-1C, optimized for recognition of tumor antigen MUC5AC variant in preclinical models

PURPOSE

NPC-1C is a chimeric immunoglobulin IgG1 developed from antigen tested in the Hollinshead tumor vaccine trials that recognizes an immunogenic MUC5AC-related tumor-associated antigen. In this article, we describe the pre-clinical characterization of this antibody that is currently being tested in human clinical trials.

EXPERIMENTAL DESIGN

The specificity of NPC-1C for pancreatic and colorectal cancer cell lines was tested by flow cytometry assays and immunohistochemical staining. Antibody-dependent cell cytotoxicity was measured using a tumor cell line lysis assay. Anti-tumor efficacy and biodistribution were assessed in nude mice bearing human pancreatic tumor xenografts.

RESULTS

Human tumor cell binding measured by flow cytometry ranged from 52 to 94 % of cells stained positive with NPC-1C in three colorectal and one pancreatic cell lines, while IHC demonstrated staining of 43 % of colon cancers and 48 % of pancreatic cancer tissues, with little or no cross-reactivity of NPC-1C with normal colon or pancreas tissues. In vitro NPC-1C-mediated tumor cell killing occurred in a median of 44.5 % of four colorectal and three pancreatic tumor cell lines. In vivo anti-tumor efficacy in a human pancreatic CFPAC-1 tumor xenograft model was demonstrated with a twofold to threefold reduction in tumor growth in the NPC-1C-treated mice compared to saline and human IgG controls. Pharmacodynamic studies indicate NPC-1C localizes in antigen-positive tumors and has minimal uptake in normal mouse tissues.

CONCLUSIONS

NPC-1C, a chimeric monoclonal antibody that reacts with a MUC5AC-related antigen expressed by pancreatic and colorectal tumor tissues, has promising preclinical activity in pancreatic and colorectal adenocarcinoma.

Single-antibody, targeted nanoparticle delivery of camptothecin

We have developed a new method for assembling targeted nanoparticles that utilizes the complexation between targeting agents that contain boronic acids and polymer-drug conjugates that possess diols. Here, we report the first in vivo, antitumor results of a nanoparticle formed via this new assembly methodology. A nanoparticle consisting of a mucic acid polymer conjugate of camptothecin (CPT), MAP-CPT, and containing on average one Herceptin antibody is investigated in nude mice bearing HER2 overexpressing BT-474 human breast cancer tumors. Nontargeted MAP-CPT and antibody-containing MAP-CPT nanoparticles of ca. 30-40 nm diameter and slightly negative zeta potential show prolonged in vivo circulation and similar biodistributions after intravenous tail vein injections in mice. The maximum tolerated dose (MTD) of the nontargeted and Herceptin-containing MAP-CPT nanoparticles is found to be 10 and 8 mg of CPT/kg, respectively, in mice. Mice bearing BT-474 human breast tumors treated with nontargeted MAP-CPT nanoparticles at 8 mg of CPT/kg show significant tumor growth inhibition (mean tumor volume of 63 mm(3)) when compared to irinotecan at 80 mg/kg (mean tumor volume of 575 mm(3)) and CPT at 8 mg/kg (mean tumor volume of 808 mm(3)) at the end of the study. Herceptin antibody treatment at 5.9 mg/kg results in complete tumor regressions in 5 out of 8 mice, with a mean tumor volume of 60 mm(3) at the end of the study. Mice treated with MAP-CPT nanoparticles at 1 mg of CPT/kg do not show tumor inhibition. However, all mice receiving administrations of MAP-CPT nanoparticles (1 mg of CPT/kg) that contain on average a single Herceptin molecule per nanoparticle (5.9 mg of Herceptin equivalent/kg) show complete tumor regression by the end of the study. These results demonstrate that the antitumor efficacy of nanoparticles carrying anticancer drugs can be enhanced by incorporating on average a single antibody.

Efficacy, safety, pharmacokinetics and biomarker findings in patients with HER2-positive advanced or metastatic breast cancer treated with lapatinib in combination with capecitabine: results from 51 Japanese patients treated in a clinical study

Background

The results from a phase III trial conducted outside of Japan demonstrated a significant improvement in time to progression (TTP) when lapatinib was combined with capecitabine compared with capecitabine alone in patients with HER2-positive advanced or metastatic breast cancer. In this clinical study of lapatinib in combination with capecitabine, efficacy, safety, pharmacokinetics (PK) and biomarkers were investigated in Japanese patients with HER2-positive advanced or metastatic breast cancer treated with prior trastuzumab.

Methods

Eligible women received lapatinib 1250 mg once daily and capecitabine 1000 mg/m² twice daily on days 1 through 14 of a 21-day cycle. The primary endpoint was the clinical benefit rate (CBR: complete response, partial response or stable disease for at least 24 weeks).

Results

Lapatinib in combination with capecitabine was well tolerated in the 51 patients enrolled in this study. CBR was 59 % (95 % CI 44.2, 72.4), and the median TTP in the Kaplan-Meier estimate was 36 weeks (95 % CI 27.1, 48.0). The majority of drug-related adverse events were mild to moderate (grade 1 or 2); the most common adverse events reported were palmar-plantar erythrodysesthesia syndrome (76 %), diarrhea (67 %) and stomatitis (41 %).

Conclusions

Lapatinib in combination with capecitabine in Japanese HER2-positive breast cancer patients was well tolerated. Overall, our findings on the efficacy, safety and PK were similar to those reported from the overseas studies.

Current Challenges for HER2 Testing in Diagnostic Pathology: State of the Art and Controversial Issues

HER2 overexpression and anti-HER2 agents represent probably the best story of success of individualized therapy in breast cancer. Due to the important therapeutic implications, the issue under the spotlight has been, since ever, the correct identification of true HER2 positivity on tissue specimens. Eligibility to anti-HER2 agents is strictly dependent on the demonstration of HER2 overexpression (by immunohistochemistry) or of HER2 gene amplification by in situ techniques (fluorescence in situ hybridization, FISH), however there are controversial issues involving cases with "equivocal" HER2 status based on conventional techniques (about 20% of specimens). In terms of HER2 expression a major debate is the presence of full-length and truncated forms of the protein and controversial clinical data have been reported on the therapeutic implications of these HER2 fragments. In terms of HER2 gene assessment, the occurrence of amplification of the chromosome 17 centromeric region (CEP17) has been proven responsible for misleading HER2 FISH results, precluding anti-HER2 based therapy to some patients. Finally HER2 activating mutations have been recently described as a biological mechanisms alternative to HER2 gene amplification. In this review we will focus on the controversies that pathologists and oncologists routinely face in the attempt to design the most tailored treatment for breast cancer patients. We will focus on the HER2 gene and on the protein, both at technical and interpretational levels.

Companion biomarkers: paving the pathway to personalized treatment for cancer

BACKGROUND

Companion biomarkers are biomarkers that are used in combination with specific therapies and that prospectively help predict likely response or severe toxicity. In this article we review the role of companion biomarkers in guiding treatment in patients with cancer.

CONTENT

In addition to the established companion biomarkers such as estrogen receptors and HER2 (human epidermal growth factor receptor 2) in breast cancer, several new companion biomarkers have become available in recent years. These include v-Ki-ras2 Kirsten rat sarcoma viral oncogene homolog (KRAS) mutations for the selection of patients with advanced colorectal cancer who are unlikely to benefit from anti-epidermal growth factor receptor antibodies (cetuximab or panitumumab), epidermal growth factor receptor (EGFR) mutations for selecting patients with advanced non-small cell lung cancer (NSCLC) for treatment with tyrosine kinase inhibitors (gefitinib or erlotinib), v-raf murine sarcoma viral oncogene homolog B1 (BRAF) mutations for selecting patients with advanced melanoma for treatment with anti-BRAF agents (vemurafenib and dabrafenib), and anaplastic lymphoma receptor tyrosine kinase (ALK) translocations for identifying patients with NSCLC likely to benefit from crizotinib.

SUMMARY

The availability of companion biomarkers should improve drug efficacy, decrease toxicity, and lead to a more individualized approach to cancer treatment.

Flotillin2 expression correlates with HER2 levels and poor prognosis in gastric cancer

OBJECTIVE

Flotillin gene is known as a tumor promoter or suppressor, depending on the tumor type or tumor stage. We aimed to investigate the clinical significance of flotillin2 protein expression in gastric cancer.

METHODS

We examined flotillin2 and erbB2 levels in tissue microarray of 282 gastric cancer samples and analyzed the association between flotillin2 levels, clinicopathologic factors and prognosis. The regulation of erbB2 by flotillin2 was examined with flotillin2 siRNA-transfected gastric cancer cells.

RESULTS

Flotillin2 partially co-localized with erbB2 at the plasma membrane as detected by confocal microscopy, levels of erbB2 were reduced after flotillin knockdown in SGC-7901 cancer cells, and the expression of flotillin2 was positively correlated with that of erbB2. In non-neoplastic gastric mucosa, flotillin2 was not expressed in the epithelial compartment. In gastric cancer, positive staining of flotillin2 was shown in 129 (45.7%) of 282 cases, also, it was significantly associated with a Lauren grade, histologic type, lymphovascular invasion and tumor location. Moreover, survival analysis showed that flotillin2 expression was an independent prognostic factor of poor survival (p<0.001).

CONCLUSIONS

These results indicate that a positive correlation exists between flotillin2 and erbB2 expression levels, flotillin2 maybe involved in the stabilization of erbB2 at the plasma membrane, flotillin2 is significantly correlated with cancer progression and poor prognosis in gastric cancer.

Long-term disease control with lapatinib and capecitabine in a patient with HER2-positive metastatic breast cancer pretreated with trastuzumab and trastuzumab-emtansine

We describe the case of a woman who has been undergoing treatment for HER2-positive metastatic breast cancer since 2002. She presented liver metastasis at diagnosis in February 2002. Combination therapy with docetaxel and trastuzumab was administered as first-line treatment, and a complete response of the hepatic lesion and a partial response at the breast primary cancer site were achieved. After 6 cycles of therapy, the patient underwent surgical excision of the breast and then received trastuzumab alone until progression, which occurred in March 2010 with the development of a right chest wall lesion. The patient progressed after therapy with trastuzumab emtansine (T-DM1) received as second-line treatment. Subsequently, a combination of lapatinib and capecitabine was started in April 2011. At this writing, the patient is still receiving treatment (24 months) and is showing a long-lasting response with a favorable safety profile.

Immunogenicity assays for antibody–drug conjugates: case study with ado-trastuzumab emtansine

Background: Antibody–drug conjugates (ADCs) such as Kadcyla™ (ado-trastuzumab emtansine [T-DM1]) present covalently bound cytotoxic drugs, which may influence their immunogenicity potential compared with antibody therapies. Therefore, ADCs require assay strategies that allow measurement of responses to all the molecular components. Results: The immunogenicity strategy for T-DM1 used a risk-based, tiered approach that included screening and titration to detect antitherapeutic antibodies; confirmation of positive responses; and characterization to assess whether the immune response is primarily to the antibody or to the linker–drug and/or new epitopes in trastuzumab resulting from conjugation. Conclusion: The tiered immunogenicity assay strategy for T-DM1 allowed detection of antitherapeutic antibodies to all components of the ADC in multiple nonclinical and clinical studies. Characterization strategies implemented in clinical studies provided additional insights into the specificity of the immune response.

Pertuzumab, trastuzumab, and docetaxel for HER2-positive metastatic breast cancer (CLEOPATRA study): overall survival results from a randomised, double-blind, placebo-controlled, phase 3 study

BACKGROUND

CLEOPATRA is a phase 3 study to compare the efficacy and safety of pertuzumab, trastuzumab, and docetaxel with placebo, trastuzumab, and docetaxel in patients with HER2-positive first-line metastatic breast cancer. The results of the primary analysis showed significantly longer median progression-free survival in the pertuzumab group than in the placebo group. Interim analysis of overall survival favoured the pertuzumab group but was not significant. Here, we report results for overall survival after an additional year of follow-up.

METHODS

The study was a double-blind randomised trial undertaken at 204 centres in 25 countries. Patients with HER2-positive metastatic breast cancer who had not received previous chemotherapy or biological treatment for their metastatic disease were randomly assigned to receive either pertuzumab, trastuzumab, and docetaxel (n=402) or the same regimen with a matching placebo replacing pertuzumab (n=406). Randomisation was in a 1:1 ratio, stratified by geographical region and previous treatment status. The primary endpoint was progression-free survival (assessed independently), which has been reported previously; no follow-up data were gathered for the primary endpoint. Secondary endpoints included overall survival, progression-free survival (assessed by investigator), objective response rate, and safety. Median follow-up was 30 months in both groups. Efficacy endpoints were analysed in the intention-to-treat population and safety was analysed by treatment received. The study is completed but safety and survival data continue to be followed up. This trial is registered with ClinicalTrials.gov, number NCT00567190.

FINDINGS

In the intention-to-treat population, 267 patients died by data cutoff (May 14, 2012), 154 (38%) of 406 in the placebo group and 113 (28%) of 402 in the pertuzumab group. Median overall survival was 37.6 months (95% CI 34.3-NE [not estimable]) in the placebo group but had not been reached (95% CI 42.4-NE) in the pertuzumab group (hazard ratio 0.66, 95% CI 0.52-0.84; p=0.0008). Investigator-assessed median progression-free survival was 12.4 months (95% CI 10.4-13.5) in the placebo group and 18.7 months (16.6-21.6) in the pertuzumab group (hazard ratio 0.69, 95% CI 0.58-0.81). Serious adverse events were reported in 115 (29%) of 396 patients who received placebo, trastuzumab, and docetaxel and 148 (36%) of 408 who received pertuzumab, trastuzumab, and docetaxel, and included febrile neutropenia, neutropenia, diarrhoea, pneumonia, and cellulitis. Overall, adverse events were similar to those reported at the primary analysis with respect to frequency, severity, and specificity.

INTERPRETATION

Our analysis shows a significant improvement in overall survival with pertuzumab, trastuzumab, and docetaxel in patients with HER2-positive metastatic breast cancer, compared with placebo, trastuzumab, and docetaxel. Since this effect was not achieved at the expense of adverse events, this regimen represents a substantial improvement on the standard of care for this population of patients.

FUNDING

F Hoffmann-La Roche, Genentech.

Cancer immunotherapy strategies based on overcoming barriers within the tumor microenvironment

For tumor antigen-specific T cells to effectively control the growth of cancer cells in vivo, they must gain access to, and function within, the tumor microenvironment. While tumor antigen-based vaccines and T cell adoptive transfer strategies can result in clinical benefit in a subset of patients, most of the patients do not respond clinically. Even for tumor-infiltrating lymphocyte (TIL)-based adoptive transfer for patients with metastatic melanoma, which can provide tumor shrinkage in around 50% of treated individuals, many patients are not eligible, in part because there are not sufficient TIL present in the resected tumor. Thus, the denominator is in fact larger, and it has been suggested that absence of TIL may be a marker for poor efficacy of immunotherapies in general. While qualitative and/or quantitative features of the T cells are important considerations for efficacy, a major component of primary resistance likely can be attributed to the tumor microenvironment. Data are accumulating suggesting that two major categories of immune resistance within the tumor microenvironment may exist: failure of T cell trafficking due to low levels of inflammation and lack of chemokines for migration, and dominant suppression through immune inhibitory mechanisms. New therapeutic interventions are being guided by these observations, and preliminary clinical success is validating this working model.