Targeted therapy of hepatocellular cancer

Importance of the field: Hepatocellular cancer (HCC) is the fifth most common malignancy worldwide and third leading cause of cancer death. HCC is highly resistant to conventional systemic therapies, and prognosis for advanced HCC patients remains poor. However, identification of signaling pathways responsible for HCC growth and progression such as RAS/RAF/MEK/ERK or PI3K/AKT/mTOR has determined crucial molecular targets and led to development of novel promising targeted therapies.

Areas covered in this review: This article presents molecular mechanisms responsible for development and progression of HCC and strategies aimed to block important molecules involved in signal transduction. It also reviews the clinical studies evaluating efficacy and safety of novel targeted approaches for treatment of this malignancy.

What the reader will gain: Inhibition of molecular targets (ligands, membrane receptors and receptor-associated kinases) represents a promising strategy for treatment of HCC; in the case of sorafenib, this has already been demonstrated to significantly improve survival of advanced HCC patients. This article reviews novel therapeutic approaches that are based on combinations of different targeted agents with or without classic cytotoxic drugs.

Take home message: Despite significant progress, advanced HCC remains an incurable disease, and the overall efficacy of recently approved targeted therapy (sorafenib) remains moderate. It is to be hoped that several ongoing clinical trials evaluating novel targeted approaches for treatment of HCC will lead to further improvement in the management of advanced disease.     

Treatment strategies for DNA repair-deficient prostate cancer

Introduction: Common recurrent genetic alterations have been identified in prostate cancer through comprehensive sequencing efforts, and the prevalence of mutations in DNA repair pathway genes in patients with advanced and metastatic disease approaches 20–25%. Identification of these underlying DNA repair defects may present unique treatment opportunities for patients, both in terms of standard-of-care treatments and selected investigational agents.

Areas covered: We review our current understanding of the genomic landscape of prostate cancer, with special attention to alterations in DNA repair pathway genes in metastatic castration-resistant disease. For patients with tumors deficient in homologous recombination repair, potential opportunities for treatment include platinum chemotherapy, poly(ADP) ribose polymerase (PARP) inhibitors, bipolar androgen therapy, and maybe immune checkpoint blockade therapy. In addition, tumors with mismatch repair defects (i.e. microsatellite instability) may be particularly susceptible to checkpoint blockade immunotherapy.

Expert commentary: We anticipate that genomic profiling of tumors will become necessary to guide treatment of advanced prostate cancer in the coming years. Work is needed to define the optimal tissue to test, and to define the natural history of tumors with specific genetic defects. The prognostic and therapeutic importance of germline vs somatic DNA repair alterations, and mono-allelic vs bi-allelic inactivation, also remains unclear. Finally, optimal strategies to sequence or combine targeted agents for these patients with ‘actionable’ mutations are now needed.     

Androgen pathway resistance in prostate cancer and therapeutic implications

Introduction: Metastatic prostate cancer is an incurable disease that is treated with a variety of hormonal therapies targeting various nodes of the androgen receptor (AR) pathway. Invariably patients develop resistance and become castration resistant. Common treatments for castration-resistant disease include novel hormonal therapies, such as abiraterone and enzalutamide, chemotherapy, immunotherapy and radiopharmaceuticals. As this disease generally remains incurable, understanding the molecular underpinnings of resistance pathways is critical in designing therapeutic strategies to delay or overcome such resistance.

Areas covered: This review will explore the resistance mechanisms relevant to hormonal agents, such as AR-V7 expression and others, as well as discussing new approaches being developed to treat patients with castration-resistant prostate cancer that take advantage of these new insights. A literature search was performed to identify all published clinical trials related to androgen therapy mechanisms of drug resistance in metastatic castration-resistant prostate cancer.

Expert opinion: Androgen therapy resistance mechanisms are varied, and include modification of all nodes in the androgen signaling pathway. The optimal treatment for men with relapsed metastatic castration-resistant prostate cancer is uncertain at this time. The authors recommend using available clinical data to guide treatment decision making until more specific biomarkers are clinically available.     

Chemotherapeutic inhibitors in the treatment of prostate cancer

Introduction: Prostate cancer being the second leading cause of death in men in Western countries remains a major challenge in healthcare. Several novel agents targeting signaling pathways in prostate cancer have recently been approved by the US Food and Drug Administration (FDA) but there is still an unmet need for new treatment strategies for castration-resistant prostate cancer (CRPC).

Areas covered: This review provides a broad overview of prostate cancer therapeutics and highlights key players in the biology of prostate cancer as well as first- and second-line treatments for CRPC. Keywords ‘chemotherapeutic agents', ‘prostate cancer', ‘Phase III clinical trials' and ‘US FDA approval' were used for search in PubMed and clinicalTrials.gov databases and the obtained literature was reviewed and summarized.

Expert opinion: Owing to the advances in screening and diagnostic techniques, the majority of prostate cancer cases are diagnosed at an early stage resulting in an almost 100% 5-year survival rate. Recently FDA-approved novel agents (e.g., abiraterone acetate and enzalutamide) have provided new hope in the fight against prostate cancer. However, CRPC remains an incurable disease. Identification of mechanisms of resistance, new biomarkers, appropriate clinical trial end points and novel treatments holds the key for the future of prostate cancer therapy.     

Advancing therapies in metastatic castration-resistant prostate cancer

ABSTRACT

Introduction: Prostate cancer is the second most common cause of cancer worldwide and is the most frequently detected cancer in the European Union in men over 50 years of age. Androgen deprivation therapy remains the cornerstone of treatment for recurrent or metastatic disease. Unfortunately, nearly all patients will develop resistance to androgen blockade leading to castration-resistant prostate cancer (CRPC). Over the last 10 years, new treatments have dramatically improved overall survival of men with mCRPC. Current therapies are based on AR-axis inhibitors and taxane-based chemotherapies, as well as radiopharmaceuticals and Sipuleucel T.

Areas covered: The authors provide a review of the current field of systemic therapy in metastatic CRPC. This is followed by an in-depth analysis of recent developments in treatment, and the biological rationale behind these therapies.

Expert opinion: Since several trials with docetaxel or novel hormonal agents showed improvement in overall survival in metastatic castration-sensitive prostate cancer, as well as in non-metastatic castration-resistant patients, it is expected that a growing subgroup of patients will be exposed earlier to chemotherapy and to AR targeted agents. It becomes then fundamental to find novel strategies to overcome drug resistance and further improve survival.     

Safety profile of new anticancer drugs

Importance of the field: The development of targeted anticancer therapies stems from advances in molecular biology. New agents range from antibodies that form complexes with antigens on the surface of the cancer cell to small molecules that have been engineered to block key enzymatic reactions. The interaction of the antibody or drug with its target inhibits key pathways involved in cell proliferation or metastasis, or activates pathways leading to cell death. Such pathways constitute ideal pharmacological targets. Clinical benefits from these novel therapeutic strategies are striking for patients with metastatic diseases.

Areas covered: This review analyses the main toxicities among most common targeted therapies that have been approved by the FDA or European Medicines Agency for their clinical utilisation in solid tumours treatment.

What the reader will gain: Here, the main toxicity and safety data among new anticancer targeted therapies are described. Data are organised through the pathways targeted by the drugs.

Take home message: The emergence of new targeted anticancer therapies promises more efficient and less toxic therapies. Generally, they are well tolerated, toxicities are commonly mild to moderate and can be handled rapidly. However, if most of these adverse events are manageable, life threatening and fatal complications can still occur.     

Emerging drugs for prostate cancer

Introduction: Androgen deprivation therapy is the mainstay treatment for patients with prostate cancer who are not candidates for definitive treatment, are diagnosed with advanced disease on initial presentation or progress after primary treatment. Patients who stop responding to androgen deprivation therapy develop castration resistant prostate cancer (CRPC). Emerging drugs undergoing clinical evaluation and drugs that have recently received FDA approval for the treatment of CRPC are reviewed.

Areas covered: As the natural history and signaling pathways of prostate cancer are better understood, new treatments and targeted therapies will be developed. The FDA recently approved 5 medications that increase survival in patients with CRPC. Additional medications and drug classes are being explored that may eventually lead to new treatment options. Articles were identified using a PubMed database search.

Expert opinion: Recent FDA medication approvals and the development of emerging treatments are promising for the future of patients with prostate cancer. The addition of new medications challenges physicians to identify the optimal sequence and/or combination in which newer and older medications should be administered. Physicians treating patients with prostate cancer have a growing responsibility to keep pace with these new medications so that they may counsel and treat patients appropriately.     

Docetaxel in the management of prostate cancer: current standard of care and future directions

Background: Advanced and metastatic prostate cancer continues to represent a significant healthcare burden. Since the publication of two randomized trials that showed significant survival and palliative benefits for men treated with docetaxel, this drug has become the treatment of choice for patients with metastatic castration resistant prostate cancer (CRPC). Objective: This review discusses the development and current use of docetaxel in metastatic CRPC, as well as future clinical applications. Methods: The current literature, meeting abstracts and ClinicalTrials.gov have been reviewed. The most relevant studies involving patients with prostate cancer receiving therapy with docetaxel, alone or in combination with other agents, have been summarised. Conclusion: Docetaxel monotherapy is the approved treatment for patients with metastatic CRPC, and its association with other agents, such as targeted therapies, is currently under study. Several trials are currently ongoing to investigate the use of docetaxel in the early stages of disease, particularly in the neoadjuvant and adjuvant settings for patients with high-risk disease.     

Advances in pharmacotherapy of small cell lung cancer

Introduction: Small cell lung cancer (SCLC) is an aggressive malignancy characterized by early metastatic dissemination and responsiveness to initial therapy. The incidence of SCLC has been declining over the past two decades. Limited-stage SCLC is a potentially curable disease with long-term survival of ～ 20% when treated with platinum-based chemotherapy plus concurrent thoracic radiation and prophylactic cranial irradiation. For patients with extensive-stage SCLC, survival can be increased with combination platinum-based chemotherapy, but the disease remains incurable.

Areas covered: This review looks at the current advances in pharmacotherapy for SCLC.

Expert opinion: Many chemotherapeutic strategies and newer cytotoxic agents have been evaluated in SCLC, and some had promising activity in early clinical trials. However, none have demonstrated consistent improvements in outcome over standard platinum-based treatment. Similarly, although many potential molecular targets have been identified in preclinical studies of SCLC, molecularly targeted therapy has yet to demonstrate any substantial activity in clinical trials. Nonetheless, future advances in this disease will undoubtedly depend on improvements in our understanding of the molecular mechanisms that drive the proliferation and survival of SCLC cells.     

Xenograft and genetically engineered mouse model systems of osteosarcoma and Ewing's sarcoma: tumor models for cancer drug discovery

Introduction: There are > 75 histological types of solid tumors that are classified into two major groups: bone and soft-tissue sarcomas. These diseases are more prevalent in children, and pediatric sarcomas tend to be highly aggressive and rapidly progressive. Sarcomas in adults may follow a more indolent course, but aggressive tumors are also common. Sarcomas that are metastatic at diagnosis, or recurrent following therapy, remain refractory to current treatment options with dismal overall survival rates. A major focus of clinical trials, for patients with sarcoma, is to identify novel and more effective therapeutic strategies targeted to genomic or proteomic aberrations specific to the malignant cells. Critical to the understanding of the potential for targeted therapies are models of disease that are representative of clinical disease and predictive of relevant clinical responses.

Areas covered: In this article, the authors discuss the use of mouse xenograft models and genetically engineered mice in cancer drug discovery. The authors provide a special focus on models for the two most common bone sarcomas: osteosarcoma (OS) and Ewing's sarcoma (ES).

Expert opinion: Predicting whether a new anticancer agent will have a positive therapeutic index in patients with OS and ES remains a challenge. The use of mouse sarcoma models for understanding the mechanisms involved in the response of tumors to new treatments is an important step in the process of drug discovery and the development of clinically relevant therapeutic strategies for these diseases.     

The preclinical discovery and development of bortezomib for the treatment of mantle cell lymphoma

Introduction: Mantle cell lymphoma (MCL) is an incurable, often aggressive B-cell malignancy. Bortezomib (BTZ), the 20S proteasome inhibitor was originally developed and approved for treatment of relapsed refractory multiple myeloma, and subsequently approved for treatment of MCL. BTZ’s single-agent activity induces clinical responses in approximately one-third of relapsed MCL patients. BTZ-containing combination therapies have further improved the quality and duration of clinical responses compared to standard chemotherapies in previously untreated MCL patients.

Areas covered: This review summarizes the discovery, mechanisms of -action and resistance, preclinical- clinical-developments, and FDA approval of BTZ for treatments of MCL.

Expert opinion: Preclinical MCL models demonstrated the apoptotic effect of BTZ through multiple mechanisms, as well as synergistic anti-MCL activity between BTZ and other chemotherapeutics. Single-agent and combinational clinical trials have validated the therapeutic potential of targeting the ubiquitin proteasome system (UPS) in MCL. However, inherent and acquired drug resistance remains a significant clinical problem and multiple potential mechanisms have been identified. Next-generation proteasome inhibitors with different pharmacodynamic properties from BTZ may partially address the issue of inherent resistance, with increased response rates noted in some diseases. In addition, upstream UPS components, e.g., E3 ligases or deubiquitinating enzymes, may also be targetable in MCL.     

New therapies for castrate-resistant prostate cancer

Introduction: Prostate cancer is the second leading cause of cancer death in men in the USA, and most of these deaths will occur as a result of castrate-resistant prostate cancer (CRPC) that has progressed despite androgen deprivation therapy. There has been better understanding of castration resistance and molecular mechanisms of prostate cancer progression recently, leading to new treatment strategies.

Areas covered: This review focuses on emerging and new therapies for castrate-resistant prostate cancer, including hormonal therapy, immunotherapy and cytotoxic agents.

Expert opinion: New treatment strategies have been developed in recent years and, with improved understanding of advanced CRPC, additional targeted treatments are expected in the near future. Further cost effectiveness research of these treatments is warranted before dissemination of these promising agents.     

Initial systemic chemotherapeutic and targeted therapy strategies for the treatment of colorectal cancer patients with liver metastases

ABSTRACT

Introduction: The liver is the most common metastatic site in colorectal cancer with more than half the patients developing a liver metastasis either at the time of their diagnosis (synchronous) or later (metachronous). Surgical resection remains the principal curative approach that offers significant survival improvements. However, upfront surgery is only possible in about 10–20% of patients at the time of diagnosis, making the consideration of other treatment modalities essential.

Areas covered: In this review, the authors provide an overview of the standard approaches for the initial management of patients with colorectal cancer with liver metastases. They then provide an up-to-date discussion of first-line systemic chemotherapy/targeted therapy options in the contexts of initially resectable and unresectable disease and review toxicities and complications following these options.

Expert opinion: Advances in chemotherapeutic agents and biological targeted therapies have improved the prognosis of colorectal cancer with liver metastases. However, there is still no ‘single best approach’, making further trials necessary to provide more evidence.     

Emerging drugs targeting human epidermal growth factor receptor 2 (HER2) in the treatment of breast cancer

Introduction: Human epidermal growth factor 2 (HER2) overexpression is present in 20% of breast cancer patients. It is associated with more aggressive disease and worse clinical outcome. New drugs are thus needed. Approved and future treatments will be discussed in this review.

Areas covered: The monoclonal antibodies trastuzumab and pertuzumab, the tyrosine kinase inhibitor lapatinib and the antibody-drug conjugate trastuzmab emtansine are approved for HER2 positive breast cancer. The combination of trastuzumab, pertuzumab and docetaxel is currently the first-line treatment in the metastatic setting. New therapies are still needed due to frequent relapse and resistance. These include mammalian target of rapamycin inhibitors, heat shock protein 90 inhibitors, pan-HER2 tyrosine kinase inhibitors, antibody-drug conjugates, immunotherapy agents (antibodies and vaccines), radioimmunotherapy and HER2 specific affinity proteins. Possible developmental issues are the complexity of the molecular biology of the HER2 positive cancer cell, the occurrence of resistance, toxicity and the high cost.

Expert opinion: The determination of the right sequence of use of old and new therapies remains a challenging issue. The selection of patients who do or don’t benefit from potentially toxic chemotherapy is also difficult. Central nervous system metastases are a common problem in HER2 positive breast cancer that needs to be addressed in future trials.     

New targeted therapies for renal cell carcinoma

Introduction: The aim of treatment in metastatic renal cell carcinoma is palliation. In the last 5 years, multiple targeted agents have been developed which have resulted in prolongation of patients' lives, but complete responses remain rare. New therapies and approaches are required to further improve the prognosis for patients with this disease.

Areas covered: This review discusses the molecular targets in renal cell carcinoma relevant to the development of new treatments and describes the progress of novel therapies. The evidence is compiled from the PubMed database and proceedings of scientific meetings, searched up to December 2010.

Expert opinion: A multitude of experimental agents are in clinical development and offer theoretical advantages over those currently in use. It is hoped that these treatments will result in better long-term control of metastatic renal cell carcinoma, with improved side effect profiles, but curative treatment in this disease remains elusive until the mechanisms underlying response and resistance to therapy are elucidated. Progress in the field has been limited by inadequate tissue collection within clinical trials; current and future clinical trial design will incorporate a larger translational component in an attempt to establish predictive biomarkers.     

Emerging targeted therapies for melanoma

Introduction: Melanoma is an aggressive cutaneous malignancy associated with poor response to traditional therapies. Recent regulatory approval for immune checkpoint inhibitors and agents targeting mutated BRAF has led to a tremendous expansion of effective treatment options for patients with advanced melanoma. Unfortunately, primary or acquired resistance develops in most patients, highlighting the need for additional therapies. Numerous genetic and other molecular features of this disease may provide effective targets for therapy development.

Areas covered: This article reviews available melanoma treatments, including immune and molecularly-targeted therapies. We then discuss agents in development, with a focus on targeted (rather than immune) therapies. In particular, we discuss agents that block mitogen-activated protein kinase (MAPK) signaling, as well as other emerging approaches such as antibody-drug conjugates, cell-cycle targeting, and novel genetically-informed clinical trials.

Expert opinion: Despite the incredible advances in melanoma therapeutics over the last several years, a clear need to develop more effective therapies remains. Molecularly-targeted therapy approaches will likely remain a cornerstone of melanoma treatment in parallel to immune therapy strategies.     

Novel targeted therapies for the treatment of penile cancer

Introduction: The treatment of penile cancer has changed over the past decade in that it was primarily a surgically managed disease and those with locally advanced or metastatic disease uniformly had a very poor prognosis. However, with the use of better traditional systemic chemotherapeutic agents in the neoadjuvant and adjuvant settings, the disease-specific survival and general outlook has improved. However, there is still a large group of patients who will progress even while on systemic therapy. It is in those patients where the application of targeted therapies has been investigated with some experiencing partial or even complete responses. With the improvement seen in patients with chemotherapy refractory disease, the application of novel targeted agents in the neoadjuvant setting may have a resultant positive impact on patient survival.

Areas covered: This review includes research pertaining to targeted therapies, biomarkers and signaling pathways involved with penile cancer. The article was based on a literature search using the keywords ‘penile cancer’ and ‘targeted therapies’.

Expert opinion: Penile cancer at the advanced stages of the disease has a high mortality. The utilization of novel targeted therapies in these situations is warranted in combination with, or sequentially with, traditional cytotoxic chemotherapy to improve the patient survival rate. Personalized therapy is nearly here for penile cancer and should be made real within the next decade.     

Molecular signature of pancreatic adenocarcinoma: an insight from genotype to phenotype and challenges for targeted therapy

Introduction: Pancreatic adenocarcinoma remains one of the most clinically challenging cancers despite an in-depth characterization of the molecular underpinnings and biology of this disease. Recent whole-genome-wide studies have elucidated the diverse and complex genetic alterations which generate a unique oncogenic signature for an individual pancreatic cancer patient and which may explain diverse disease behavior in a clinical setting.

Areas covered: In this review article, we discuss the key oncogenic pathways of pancreatic cancer including RAS-MAPK, PI3KCA and TGF-β signaling, as well as the impact of these pathways on the disease behavior and their potential targetability. The role of tumor suppressors particularly BRCA1 and BRCA2 genes and their role in pancreatic cancer treatment are elaborated upon. We further review recent genomic studies and their impact on future pancreatic cancer treatment.

Expert opinion: Targeted therapies inhibiting pro-survival pathways have limited impact on pancreatic cancer outcomes. Activation of pro-apoptotic pathways along with suppression of cancer-stem-related pathways may reverse treatment resistance in pancreatic cancer. While targeted therapy or a ‘precision medicine’ approach in pancreatic adenocarcinoma remains an elusive challenge for the majority of patients, there is a real sense of optimism that the strides made in understanding the molecular underpinnings of this disease will translate into improved outcomes.     

The hurdle of antiandrogen drug resistance: drug design strategies

Introduction: Prostate cancer is the second most common cancer death in men after lung cancer, due to distant metastases. While distant prostate cancer is typically castrate resistant, it is not necessarily androgen independent. For this reason, a review of the literature regarding the pathways involved in androgen signaling and therapeutic regimens to treat distant metastases is beneficial to increasing the survival rate of prostate cancer patients.

Areas covered: In this article, the author reviews the literature from the past decade covering metastatic hormone refractory prostate cancer with the aim to examine and identify pathways, therapeutic targets and current therapies for treating castrate-resistant disease. As this area is lacking, the author aims to provide the reader with knowledge of the molecular consequences of castrate resistant prostate cancer, the current treatment paradigms and future directions.

Expert opinion: While there have been advances in the treatment of castrate resistant prostate cancer, only minimal advances have been made in overall survival rate. Due to aberrant mutations and activation in the androgen receptor gene, and the complexity of cell signaling within prostate cancer, the androgen receptor should remain a main target for drug discovery efforts. This author believes that designing compounds that will reduce the activation of the androgen receptor may hold the key to a cure in the future.