Ixabepilone (Epothilone B Analogue BMS-247550) Is Active in Chemotherapy-Naive Patients With Hormone-Refractory Prostate Cancer: A Southwest Oncology Group Trial S0111

Crosstalk between Microtubule Stabilizing Agents and Prostate Cancer

A variety of microtubule-stabilizing cytotoxic agents (MSA) with diverse chemical scaffolds have been discovered from marine sponges, microorganisms, and plants. Two MSAs, docetaxel and cabazitaxel, are the exclusive chemotherapeutics that convey a survival benefit in patients with castration-resistant prostate cancer (CRPC). Additional MSAs have been investigated for their potential in treating prostate cancer in both clinical and preclinical settings. Independent of promoting mitotic arrest, MSAs can suppress the nuclear accumulation of androgen receptor (AR), which is the driving force for prostate cancer cell growth and progression. The alternative mechanism not only helps to better understand the clinical efficacy of docetaxel and cabazitaxel for AR-driven CRPC but also provides an avenue to seek better treatments for various forms of prostate cancer. The dual mechanisms of action enable MSAs to suppress AR-null prostate cancer cell proliferation by cell mitosis pathway and to interfere with the AR signaling pathway in AR positive cells. MSA chemotherapeutics, being administered alone or in combination with other therapeutics, may serve as the optimal therapeutic option for patients with either castration-sensitive or castration-resistant prostate cancer. This review provides an overview of the anti-prostate cancer profiles (including preclinical and clinical studies, and clinical use) of diverse MSAs, as well as the mechanism of action.

Regression of Castration-Resistant Prostate Cancer by a Novel Compound HG122

Prostate cancer (PCa) is a common aggressive disease worldwide which usually progresses into incurable castration-resistant prostate cancer (CRPC) in most cases after 18-24 months treatment. Androgen receptor (AR) has been considered as a crucial factor involved in CRPC and the study of AR as a potential therapeutic target in CRPC may be helpful in disease control and life-cycle management. In this study, we identified a potent small molecule compound, HG122, that suppressed CRPC cells proliferation and metastasis, and inhibited tumor growth both in subcutaneous and orthotopic tumor model. In addition, HG122 reduced the mRNA expression of PSA and TMPRSS2 which are target genes of AR, resulting in cell growth inhibition and metastasis suppression of CRPC, without affecting the expression of AR mRNA level. Mechanically, HG122 promoted AR protein degradation through the proteasome pathway impairing the AR signaling pathway. In conclusion, HG122 overcomes enzalutamide (ENZ) resistance in CRPC both in vitro and in vivo, thus suggesting HG122 is a potential candidate for the clinical prevention and treatment of CRPC.

Novel Agents and Targets in Managing Patients with Metastatic Prostate Cancer

Background

Docetaxel has recently been found to improve survival in patients with metastatic androgen-independent prostate cancer (AIPC). Chemotherapy as a first-line option leaves room for improvement, while second-line options are multiple and somewhat controversial.

Methods

Clinically relevant articles focusing on chemotherapy drugs for metastatic prostate cancer and their mechanism of action and efficacy were reviewed from January 2004 through April 2006.

Results

Docetaxel is the standard of care for AIPC. However, for doublets with docetaxel or second-line chemotherapy, multiple studies have shown interesting and promising results with calcitriol, thalidomide, bevacizumab, satraplatin, vaccines, ixabepilone, and atrasentan.

Conclusions

Docetaxel should be considered for first-line treatment of metastatic AIPC. Due to its progression-free survival of only 6 months, more effective drugs and drug combinations need to be developed to treat patients with AIPC. Combination treatments with docetaxel and other new agents are promising, but adequately powered phase III trials need to be conducted with survival as the principal endpoint for these promising drug combinations.

Ixabepilone for the treatment of endometrial cancer

INTRODUCTION

Endometrial cancer (EC) is the most common gynaecological cancer. Despite significant progress in the multimodality treatment approach, the prognosis remains poor for patients with advanced disease. Thus, there is the necessity of more effective strategies. The microtubule-stabilizing agent ixabepilone is the first drug in this new class of agents that has been approved for metastatic breast cancer treatment. Based on empiric data and on the clinical efficacy demonstrated in breast cancer, several clinical trials were proposed to define its role in EC. The aim of this review is to determine whether ixabepilone improved the clinical outcome in patients with locally advanced, recurrent or metastatic EC.

AREAS COVERED

Preclinical and clinical studies of ixabepilone in endometrial cancer were analyzed and discussed. Data were obtained by searching for English peer-reviewed articles on PubMed, phase I and II studies registered on clincaltrials.gov, and related abstracts recently presented at major international congresses.

EXPERT OPINION

Advanced or recurrent EC still represents a challenge and an unmet need in the panorama of gynaecological malignancies. Ixabepilone's future therapeutic role in EC remains ill defined. Nevertheless, despite its limited efficacy in EC, clinicians treating gynaecological tumours should be aware of its main aspects.

Novel non-AR therapeutic targets in castrate resistant prostate cancer

Castrate resistant prostate cancer (CRPC) remains a disease with significant morbidity and mortality. The recent approval of abiraterone and enzalutamide highlight the improvements which can be made targeting the androgen receptor (AR) axis. Nonetheless, resistance inevitably develops and there is continued interest in targeting alternate pathways which cause disease resistance and progression. Here, we review non-AR targets in CRPC, with an emphasis on novel agents now in development. This includes therapeutics which target the tumour microenvironment, the bone metastatic environment, microtubules, cellular energetics, angiogenesis, the stress response, survival proteins, intracellular signal transduction, DNA damage repair and dendritic cells. Understanding the hallmarks of prostate cancer resistance in CRPC has led to the identification and development of these new targets. We review the molecular rationale, as well at the clinical experience for each of these different classes of agents which are in clinical development.

Bladder carcinoma: understanding advanced and metastatic disease with potential molecular therapeutic targets

This article is an expert review of bladder cancer genetics focusing on genetic changes and their significance in the pathogenesis and progression of bladder transitional cell carcinoma, in particular, muscle-invasive disease. Alongside the relevant genetic markers and their products, new therapeutic targets and agents that are being developed are presented.

Tubulin-targeted agents including docetaxel and cabazitaxel

Microtubules are dynamic filamentous cytoskeletal proteins that are responsible for cellular integrity and architecture, mitosis, intracellular transport, cell signaling, and gene expression. Tubulin exists in the cell as dimers of α and β subunits, which complexes with a variety of regulatory proteins. There is a dynamic equilibrium between free and polymerized tubulin causing a state called "dynamic instability," which is a target of anticancer drugs, which inhibit tubulin through polymerization (taxanes, epothilones) or depolymerization (vinca alkaloids). Docetaxel-based therapy was the first such treatment to demonstrate a survival benefit in men with castration-resistant prostate cancer. Cabazitaxel, an antitubulin agent, which demonstrates activity in multidrug- and docetaxel-resistant cancer cell lines, demonstrates a survival benefit over mitoxantrone and prednisone in patients who have failed docetaxel-based chemotherapy. This article reviews the use of antitubulin agents in patients with castration-resistant prostate cancer.

Evolving landscape and novel treatments in metastatic castrate-resistant prostate cancer

Treatment options for castrate-resistant prostate cancer (CRPC) have advanced in recent years and significantly improved the outlook for patients with this aggressive and lethal disease. Further understanding of the biology of CRPC has led to several new targeted therapies and continues to emphasize the importance of androgen receptor (AR) directed therapy. The treatment landscape is rapidly changing and further biologically rationale, biomarker-based ongoing clinical trials are needed. We review the recent results of major clinical trials in CRPC. New and investigational agents now in clinical evaluation are reviewed including inhibitors of angiogenesis, microtubules, chaperones, AR and intracellular kinases, as well as immunotherapy, radiopharmaceuticals and bone-targeted agents. The recent improvement in prognosis for CRPC brings continued optimism for further improvements. Thoughtful planning of clinical trials and further understanding of the mechanisms of resistance to therapies will allow for continued progress in patient care.

Current management of prostate cancer: dilemmas and trials

The past decade has witnessed significant advances in our understanding of the biology of prostate cancer. Androgen ablation/androgen receptor inhibition remains as the mainstay of treatment for advanced prostate cancer. Our understanding of the biology of prostate cancer has increased exponentially owing to advances in molecular biology. With this knowledge many intriguing issues have come to light, which clinicians and scientists alike strive to answer. These include why prostate cancer is so common, what drives the development of prostate cancer at a molecular level, why prostate cancer appears refractory to many families of cytotoxic chemotherapeutics, and why prostate cancer preferentially metastasizes to bone. Two clinical forms of prostate cancer have been identified: indolent organ confined disease, which elderly men often die of, and aggressive metastatic disease. A method of distinguishing between these two forms of the disease at an organ-confined stage remains elusive. Understanding the mechanisms of castrate resistance is a further issue of clinical importance. New trials of treatments, including molecular agents that target prostate cancer from a range of angles, have been instituted over the past 10-15 years. We can look at these trials not only as a chance to investigate the effectiveness of new treatments but also as an opportunity to further understand the complex biology of this disease.

The unfolding treatment landscape for men with castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) is a fatal disease in virtually all patients. Docetaxel chemotherapy became the standard front-line agent based on the results of the TAX327 trial in 2004, with a survival advantage of 3 months achieved over mitoxantrone. Over the past few years, an improved understanding of the molecular biology of castration-resistance has resulted in expansion of the treatment armamentarium for advanced prostate cancer with the emergence of novel androgen receptor-directed therapies, cytotoxic chemotherapies, as well as immunotherapies. Four different agents have very recently gained approval by the U.S. Food and Drug Administration for the treatment of CRPC and this review will summarize the development, mechanism of action, and safety and efficacy of these agents as demonstrated in preclinical as well as clinical studies.

Ixabepilone-associated peripheral neuropathy: data from across the phase II and III clinical trials

PURPOSE

Dose-limiting neuropathy is a major adverse event associated with most of the microtubule-stabilizing agent-based chemotherapy regimens. Ixabepilone, a semisynthetic analogue of the natural epothilone B, has activity against a wide range of tumor types. Peripheral neuropathy (PN), associated with ixabepilone treatment, is usually mild to moderate, predominantly sensory and cumulative. Preclinical studies demonstrate that ixabepilone and taxanes produce a similar neurotoxicity profile.

METHODS

We searched databases of phase II/III clinical trials involving patients receiving ixabepilone as a monotherapy or in combination with capecitabine for incidences of neuropathy. Potential risk factors for grade 3/4 PN were identified by a Cox regression analysis on a dataset of 1,540 patients with different tumor types across multiple studies.

RESULTS

Rates for incidence of ixabepilone-induced severe PN (Common Terminology Criteria for Adverse Events grade 3/4) ranged from 1% in early untreated breast cancer up to 24% in heavily pretreated metastatic breast cancer; grade 4 PN was rare (≤ 1%). Common symptoms included numbness, paresthesias, and sometimes dysesthesias. Cox regression analysis identified only preexisting neuropathy as a risk factor for increased ixabepilone-associated PN. The management of PN has been primarily through dose adjustments (dose delays and/or dose reduction). Patients had resolution of their neuropathy within a median time of 5 to 6 weeks.

CONCLUSIONS

PN is a dose-limiting toxicity associated with ixabepilone treatment, is reversible in most patients, and can be managed with dose reduction and delays.

Phase II trial of ixabepilone and carboplatin with or without bevacizumab in patients with previously untreated advanced non-small-cell lung cancer

BACKGROUND

Epothilones, a new class of cytotoxic agents, have demonstrated activity in non-small-cell lung cancer (NSCLC). This phase II study examined ixabepilone/carboplatin (cohort A) and ixabepilone/carboplatin/bevacizumab (cohort B) as first-line therapy for patients with advanced NSCLC.

METHOD

Patients were enrolled to either cohort A or B at physician discretion and when eligibility met. Eligible patients had newly diagnosed stage III/IV NSCLC, ECOG PS 0-1, adequate organ function, no active CNS metastases, and, in cohort B, bevacizumab treatment criteria. Both cohorts received ixabepilone 30 mg/m2 and carboplatin AUC=6 IV day 1 every 3-weeks for a maximum of 6 cycles. Patients assigned to cohort B also received bevacizumab 15 mg/kg IV day 1 of each cycle, and could continue single-agent bevacizumab for 6 additional cycles.

RESULTS

Eighty-two patients (median age, 63 years; majority stage IV and former smokers) were enrolled from 11/08 to 10/09 (A-42, B-40) and received medians of 4 and 6 cycles, respectively. The ORRs were 29% and 50%. After median follow up of 17.5 months (A) and 15.7 months (B), median progression free survivals were A-5.3 months (95% CI 2.8-8.6) and B-6.7 months (95% CI 5.1-8.4), with median overall survivals of 9.3 months (95% CI 6.4-16.6) 13.2 months (95% CI 8.9-upper limit not reached), respectively. Grade 3/4 toxicity included: anemia (A-10%, B-27%), neutropenia (A-31%, B-48%), thrombocytopenia (A-19%, B-20%), fatigue (A-10%, B-23%), infection (A-5%, B-20%), and hypersensitivity reaction (A-2%, B-5%). There was one treatment-related death, due to hemoptysis in a cohort B patient with squamous histology.

CONCLUSIONS

Ixabepilone can be safely combined with carboplatin in newly diagnosed patients with advanced NSCLC. The benefits of treatment appear consistent with those achieved with other modern platinum-doublet regimens. The addition of bevacizumab increases toxicities, however, these are largely expected and reversible. The high ORR and OS observed in the bevacizumab-cohort are encouraging, but would require validation in a larger randomized trial of cohort A versus B.

Targeted therapies in metastatic castration-resistant prostate cancer: beyond the androgen receptor

Prostate cancer is the most common male cancer and one of the top causes of male cancer-related death in Western countries. Most patients with prostate cancer respond to initial androgen deprivation therapy but eventually progress to castration-resistant prostate cancer (CRPC). Although androgen receptor signaling remains the main driver in CRPC, a growing body of evidence suggests that other pathways are involved in this progression. This article reviews the preclinical data and current status of clinical trials therapeutically targeting tubulin, DNA repair, molecular chaperones such as CLU and Hsp27, tyrosine kinases, and DNA repair.

Phase II study of first-line sagopilone plus prednisone in patients with castration-resistant prostate cancer: a phase II study of the Department of Defense Prostate Cancer Clinical Trials Consortium

BACKGROUND

Preclinical studies in prostate cancer (PC) models demonstrated the anti-tumour activity of the first fully synthetic epothilone, sagopilone. This is the first study to investigate the activity and safety of sagopilone in patients with metastatic castration-resistant PC (CRPC).

METHODS

Chemotherapy-naïve patients with metastatic CRPC received sagopilone (one cycle: 16 mg m(-2) intravenously over 3 h q3w) plus prednisone (5 mg twice daily). The primary efficacy evaluation was prostate-specific antigen (PSA) response rate (≥50% PSA reduction confirmed ≥28 days apart). According to the Simon two-stage design, ≥3 PSA responders were necessary within the first 13 evaluable patients for recruitment to continue until 46 evaluable patients were available.

RESULTS

In all, 53 patients received ≥2 study medication cycles, with high compliance. Mean individual dose was 15.1±1.4 mg m(-2) during initial six cycles, mean dose intensity 94±9%. The confirmed PSA response rate was 37%. Median overall progression-free survival was 6.4 months. The most commonly reported adverse events (>10% of patients) were peripheral neuropathy (94.3%), fatigue (54.7%) and pain in the extremities (47.2%). Sagopilone was associated with very little haematological toxicity.

CONCLUSION

This study shows that first-line sagopilone has noteworthy anti-tumour activity and a clinically significant level of neuropathy for patients with metastatic chemotherapy-naïve CRPC.

A phase II trial of ixabepilone in Asian patients with advanced gastric cancer previously treated with fluoropyrimidine-based chemotherapy

PURPOSE

The highest rates of gastric cancer occur in Eastern Asia. Fluoropyrimidine-based therapy is used initially in unresectable and metastatic disease, but no single standard of care exists following disease progression. Ixabepilone, an epothilone B analog, is a non-taxane microtubule-stabilizing agent with clinical activity across multiple tumor types approved by the United States Food and Drug Administration for treatment of metastatic breast cancer.

METHODS

Asian patients with unresectable or metastatic gastric adenocarcinoma who had failed fluoropyrimidine-based chemotherapy received ixabepilone 40 mg/m(2) by 3-h intravenous infusion every 3 weeks. The primary endpoint was objective response rate (ORR).

RESULTS

Fifty-two patients were treated (65.4 % men; median age: 56.5 years). The ORR was 15.4 % (95 % confidence interval [CI] 6.9-28.1); 8 patients achieved partial responses for a median duration of 3.1 months (95 % CI 2.6-4.1 months) and 26 patients (50.0 %) had stable disease. Median progression-free survival was 2.8 months (95 % CI 2.1-3.5 months). The most common grade 3 non-hematological toxicities were fatigue (9.6 %), decreased appetite (7.7 %), sensory neuropathy (5.8 %), and diarrhea (5.8 %). Grade 3/4 neutropenia occurred in 46.2 % of patients.

CONCLUSIONS

Ixabepilone is active in Asian patients with advanced gastric cancer and shows a toxicity profile similar to those previously reported in other tumor types.

Medical therapy of endometrial cancer: current status and promising novel treatments

While early-stage endometrial cancer is often successfully treated with surgical intervention, treatment of advanced endometrial carcinoma can be difficult and prognosis poor, particularly in the context of metastatic or recurrent disease. Standard chemotherapy agents for both adjuvant first-line treatment (for selected patients deemed at high risk of relapse) and recurrent endometrial cancer include doxorubicin, platinum agents and paclitaxel. Investigational options currently being studied in phase II trials include both combined regimens of standard chemotherapeutic agents versus radiation as well as targeted treatments such as epothilones, mammalian target of rapamycin (mTOR) inhibitors and anti-angiogenic agents. Recent interest in the molecular pathways of carcinogenesis have lead to increased investigation of these novel agents and the hope that they will impact positively on the overall survival of women with endometrial cancer.

[Prostate cancer and chemotherapy: standards care and perspectives]

Docetaxel is a reference treatment of metastatic prostate cancer castration-resistant. Until now, the different associations were studied without benefit when compared to docetaxel as monotherapy. Cabazitaxel showed efficacy in second-line in patients with progressive disease during or after docetaxel chemotherapy. Other molecules are being evaluated in second-line post-docetaxel. Abiraterone acetate is an alternative treatment to cabazitaxel in metastatic second-line resistant to castration. Predictive factors to choice treatment must be evaluated and proposed to personalize treatment in the future. Docetaxel activity was also studied in early stage of prostate cancer and seems to be promising. A cabazitaxel activity in early stage of cancer is also being evaluated.

Castration-resistant prostate cancer: mechanisms, targets, and treatment

Patients with castration-resistant prostate cancer (CRPC), who progress after docetaxel therapy, had until very recently, only a few therapeutic options. Recent advances in this field brought about new perspectives in the treatment of this disease. Molecular, basic, and translational research has given us a better understanding on the mechanisms of CRPC. This great investment has turned into a more rational approach to the development of new drugs. Some of the new treatments are already available to our patients outside clinical trials and may include inhibitors of androgen biosynthesis; new chemotherapy agents; bone-targeted therapy; and immunotherapy. This paper aims to review the mechanisms of prostate cancer resistance, possible therapeutic targets, as well as new options to treat CRPC.

Phase II trial of weekly ixabepilone in men with metastatic castrate-resistant prostate cancer (E3803): a trial of the Eastern Cooperative Oncology Group

Ixabepilone is an epothilone B analogue with activity in a variety of solid malignancies, including prostate cancer. The main dose-limiting toxicity of ixabepilone is myelosuppression when administered by using an every 3-week schedule. Here we evaluate the activity of a weekly ixabepilone in men with metastatic castrate-resistant prostate cancer to minimize hematologic toxicity.

PURPOSE

BMS-247550 (ixabepilone) is an epothilone B analogue with activity in taxane-resistant cancer cell lines. Here we report the activity and toxicity of ixabepilone, administered by using a weekly schedule, in men with metastatic castrate-resistant prostate cancer (CRPC).

EXPERIMENTAL DESIGN

Patients with metastatic CRPC received ixabepilone at 20 mg/m(2) intravenous weekly x 3, in 4-week cycles. This noncomparative study stratified patients to either a chemotherapy naive (CN), prior taxane (Tax) only, or 2 prior cytotoxic (TCx) chemotherapy arm. The primary endpoint was prostate-specific antigen response by using PCWG (Prostate Cancer Working Group) 1 criteria. Secondary endpoints included radiographic response when using RECIST (Response Evaluation Criteria In Solid Tumors).

RESULTS

In total, 124 patients were enrolled, of whom, 109 were eligible (35 CN, 42 Tax, and 32 TCx) for the primary response determination in this study. Prostate-specific antigen responses were seen in 12 (34.3%) of 35, 12 (28.6%) of 42, and 7 (21.9%) of 32 patients with the partial objective response in 5 (22.7%) of 22, 2 (8.0%) of 25, and 0 (0.0%) of 24 patients for the CN, Tax, and TCx arms, respectively. Significant (grade 3/4) neutropenia was seen in 6 (15.4%), 7 (14.6%), and 9 (25.0%); and grade 3/4 sensory neuropathy was seen in 8 (20.5%), 12 (25.0%), and 12 (33.3%) for CN, Tax, and TCx, respectively. Grade 3/4 thrombocytopenia was infrequent and seen in only one patient on the CN and the TCx arm.

CONCLUSION

Ixabepilone was found to have an acceptable toxicity profile when administered by using a weekly schedule with less myelosuppression compared with prior studies when using the every 3-week schedule. Single-agent activity was observed and met prespecified activity levels for the Tax treated arm.

Phase I trial of ixabepilone administered as three oral doses each separated by 6 hours every 3 weeks in patients with advanced solid tumors

BACKGROUND

Ixabepilone, which stabilizes microtubules, has low susceptibility to drug resistance mediated by P-glycoprotein or βIII-tubulin.

MATERIALS AND METHODS

This study was designed to determine the maximum tolerated dose (MTD) of oral ixabepilone when administered every 6 h for three doses, every 3 weeks, to patients with refractory advanced cancers. Eighteen patients were treated with escalating doses of ixabepilone: three at cohort 1 (30 mg/dose; 90 mg on Day 1), nine at cohort 2 (40 mg/dose; 120 mg on Day 1), and six at cohort 3 (50 mg/dose; 150 mg on Day 1). Serial plasma samples were collected during cycle 1 for pharmacokinetic (PK) measurements.

RESULTS

Of the 18 treated patients, eight were male and ten were female. The median age was 59 years, and most had an excellent performance status (KPS 90-100; 61%). There were two dose limiting toxicities (DLT): Grade 4 febrile neutropenia at the 120 mg dose and Grade 4 neutropenic sepsis at the 150 mg dose. Because of the severity and duration of neutropenic sepsis at level 3, level 2 (120 mg) was defined as the MTD and this cohort was expanded to nine patients. High inter-individual variability in plasma drug concentrations was observed during the study, with particularly high levels in two patients with DLT.

CONCLUSIONS

On the basis of this safety profile, the MTD of oral ixabepilone was defined as 120 mg given as three 40 mg doses each separated by 6 h on Day 1 of a 3-week cycle. However, the PK variability observed makes further development of this oral formulation unlikely.

Current and emerging treatment options for castration-resistant prostate cancer: a focus on immunotherapy

BACKGROUND

Castration-resistant prostate cancer is a disease with limited treatment options. However, the ongoing elucidation of the mechanisms underlying this disease continues to support the development of not only novel agents, but also innovative approaches. Among these therapies, immunotherapy has emerged as a promising strategy.

DESIGN

This review article summarizes the most recent data from investigations of immunotherapies in castration-resistant prostate cancer (literature and congress searches current as of August 2011).

RESULTS

Immunotherapeutic strategies such as passive immunization, vaccines, and particularly checkpoint blockade have demonstrated some efficacy as single agents. Elucidation of effective combinations of agents and drug regimens is ongoing but will require continued careful investigation, including the standardization of surrogate endpoints in clinical trials.

CONCLUSIONS

It is hypothesized that the combination of immunotherapeutic agents with traditional and novel chemotherapeutics will potentiate the efficacy of the chemotherapeutics while maintaining manageable toxicity.

A phase 2 study of patupilone in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel: Canadian Urologic Oncology Group study P07a

BACKGROUND

The purpose of this study was to determine the clinical activity of patupilone in patients with metastatic castration-resistant prostate cancer previously treated with docetaxel.

PATIENTS AND METHODS

Eligible patients had progressive disease within 6 months of receiving docetaxel. Patupilone was administered 10 mg/m2 i.v. every 3 weeks. The primary end point was the proportion of patients with a confirmed≥50% prostate-specific antigen (PSA) decline.

RESULTS

Eighty-three patients were enrolled. At baseline, the median time to progression after prior docetaxel was 1.4 months (range 0-5.7). Gastrointestinal serious adverse events occurred in four of the six initial patients leading to a reduction of the starting dose of patupilone to 8 mg/m2 for subsequent patients. Grade 3-4 toxicity at this dose included diarrhea (22%), fatigue (21%), and anorexia (10%). One patient experienced grade 3-4 hematologic toxicity. A PSA decline of ≥50% occurred in 47% of patients. A partial measurable disease response occurred in 24% of assessable patients. A patient-reported pain response was observed in 59% of assessable patients. Median time to PSA progression was 6.1 months [95% confidence interval (CI) 4.7-8.0] and median overall survival was 11.3 months (95% CI 9.8-15.4).

CONCLUSIONS

Patupilone at 8 mg/m2 was tolerable, had antitumor activity, and was associated with symptomatic improvement in patients previously treated with docetaxel.

Castration-resistant prostate cancer: new science and therapeutic prospects

There is a growing number of new therapies targeting different pathways that will revolutionize patient management strategies in castration-resistant prostate cancer (CRPC) patients. Today there are more clinical trial options for CRPC treatment than ever before, and there are many promising agents in late-stage clinical testing. The hypothesis that CRPC frequently remains driven by a ligand-activated androgen receptor (AR) and that CRPC tissues exhibit substantial residual androgen levels despite gonadotropin-releasing hormone therapy, has led to the evaluation of new oral compounds such as abiraterone and MDV 3100. Their results, coupled with promising recent findings in immunotherapy (eg sipuleucel-T) and with agents targeting angiogenesis (while awaiting the final results of the CALGB trial 90401) will most probably impact the management of patients with CRPC in the near future. Other new promising agents need further development. With our increased understanding of the biology of this disease, further trial design should incorporate improved patient selection so that patient populations are those who may be most likely to benefit from treatment.

Novel therapeutics for the management of castration-resistant prostate cancer (CRPC)

Androgen-deprivation therapy is the initial treatment for metastatic prostate cancer. Although highly effective, all men who live long enough will eventually experience disease progression and develop castration resistance. Patients who have castration-resistant prostate cancer (CRPC) have a median survival of ≈1-3 years. When evaluating novel therapies for CRPC, one must consider the endpoints measured for determination of response. We will discuss PSA, circulating tumour cells, progression-free survival, overall survival, and other endpoints used in clinical trials. Docetaxel and sipuleucel-T are currently the preferred first-line treatment options for patients with CRPC; cabazitaxel is a new option for patients after docetaxel failure. Patients with CRPC historically have very poor survival, underscoring the unmet need for novel therapeutics. Although many agents appear promising, well-designed randomized phase III trials are necessary to establish their impact on survival and health-related quality of life. Promising new therapies include hormonal agents, such as abiraterone and MDV3100, as well as other novel immunotherapeutics and anti-prostate-specific membrane antigen therapies. In the future, we anticipate therapies tailored to individual patients' malignancies using various molecular analyses.

Horizon scanning for novel therapeutics for the treatment of prostate cancer

Treatment options for patients with advanced prostate cancer (PCa) remain limited. Improved understanding of the underlying molecular drivers of PCa pathogenesis, progression and resistance development has provided the fundamental basis for rational targeted drug design. Key findings in recent years include the identification of ETS gene rearrangements, the dissection of PCa molecular heterogeneity and the discovery that castration-resistant prostate cancer (CRPC) remains androgen driven despite the androgen-depleted milieu, thus making androgen receptor (AR) signaling a continued focus of molecularly targeted treatments. AR ligand-independent activation of tyrosine kinase prosurvival signaling cascades and angiogenesis have also been implicated in disease progression. A multitude of new molecularly targeted agents that abrogate AR signaling, inhibit the mitogenic and prosurvival signal transduction pathways, perturb the tumor-bone microenvironment, impair tumor vasculature, facilitate immune modulation and induce apoptosis are in clinical development and are highly likely to change the current treatment paradigm. It is clear that the success of these molecular targeted therapies hinges in part on optimal patient selection based on the molecular disease profile and an improved understanding of the mechanistic basis of acquired resistance. This review outlines the current clinical development of molecular targeted treatments in CRPC, with particular emphasis on agents that are in the later stages of clinical development, and details the challenges and future direction of developing these antitumor agents.

The epothilones: new therapeutic agents for castration-resistant prostate cancer

The management of castration-resistant prostate cancer (CRPC) presents a clinical challenge because of limitations in efficacy and durability with currently available therapeutics. The epothilones represent a novel class of anticancer therapy that stabilizes microtubules, causing cell death and tumor regression in preclinical models. The structure of the tubulin-binding site for epothilones is distinct from that of the taxanes. Moreover, preclinical studies suggest nonoverlapping mechanisms of resistance between epothilones and taxanes. In early-phase studies in patients with CRPC, treatment with ixabepilone, a semisynthetic analog of epothilone B, induced objective responses and prostate-specific antigen declines in men previously progressing on docetaxel-based regimens. Clinical activity has been observed in nonrandomized trials for patients with CRPC using ixabepilone in the first- and second-line settings as a single agent and in combination with estramustine. Patupilone and sagopilone were also shown to have promising efficacy in phase II clinical trials of patients with CRPC. All three epothilones appear to be well tolerated, with modest rates of neutropenia and peripheral neuropathy. The lack of crossresistance between epothilones and taxanes may allow sequencing of these agents. Evaluating epothilones in phase III comparative trials would provide much-needed insight into their potential place in the management of patients with CRPC.

Evolving standards in the treatment of docetaxel-refractory castration-resistant prostate cancer

The management of men with metastatic castration-resistant prostate cancer (CRPC) has taken several leaps forward in the past year, with the demonstration of improved overall survival with three novel agents (sipuleucel-T, cabazitaxel with prednisone and abiraterone acetate with prednisone), and a significant delay in skeletal-related events observed with denosumab. The pipeline of systemic therapies in prostate cancer remains strong, as multiple agents with a diverse array of mechanisms of action are showing preliminary signs of clinical benefit, leading to more definitive phase III confirmatory trials. In this review, which represents part 1 of a two-part series on metastatic CRPC, we will summarize the mechanisms of resistance to hormonal and chemotherapies and discuss the evolving landscape of treatment options for men with CRPC, with a particular focus on currently approved and emerging treatment options following docetaxel administration, as well as prognostic factors in this post-docetaxel state. As docetaxel remains the standard initial systemic therapy for men with metastatic CRPC for both palliative and life-prolonging purposes, knowledge of these evolving standards will help to optimize delivery of care and long-term outcomes.

Pathways of chemotherapy resistance in castration-resistant prostate cancer

Chemotherapy remains the major treatment option for castration-resistant prostate cancer (CRPC) and limited cytotoxic options are available. Inherent chemotherapy resistance occurs in half of all patients and inevitably develops even in those who initially respond. Docetaxel has been the mainstay of therapy for 6 years, providing a small survival benefit at the cost of significant toxicity. Cabazitaxel is a promising second-line agent; however, it is no less toxic, whereas mitoxantrone provides only symptomatic benefit. Multiple cellular pathways involving apoptosis, inflammation, angiogenesis, signalling intermediaries, drug efflux pumps and tubulin are implicated in the development of chemoresistance. A thorough understanding of these pathways is needed to identify biomarkers that predict chemotherapy resistance with the aim to avoid unwarranted toxicities in patients who will not benefit from treatment. Until recently, the search for predictive biomarkers has been disappointing; however, the recent discovery of macrophage inhibitory cytokine 1 as a marker of chemoresistance may herald a new era of biomarker discovery in CRPC. Understanding the interface between this complex array of chemoresistance pathways rather than their study in isolation will be required to effectively predict response and target the late stages of advanced disease. The pre-clinical evidence for these resistance pathways and their progress through clinical trials as therapeutic targets is reviewed in this study.

Emerging Treatments for Castrate-Resistant Prostate Cancer

Castrate-resistant prostate cancer (CRPC) is a challenging aspect in the treatment of prostate cancer. Research has identified several pathways in the pathogenesis of CRPC. Several new agents targeting some of these pathways have shown promising data during clinical trials. In the area of androgen depletion, abiraterone acetate and MDV100 have been studied and have shown to decrease prostate-specific antigen (PSA) levels in phase I and II studies. Bevacizumab is a monoclonal antibody antiangiogenesis agent that targets vascular endothelial growth factor (VEGF) and has shown to decrease PSA levels in combination with other cytotoxic agents. Three agents, ixabepilone, patupilone, and sagopilone, in the class of epothilones (tubulin polymerizing antitumor agents), have shown moderate reductions in PSA levels and moderate adverse effects. The results of ongoing studies with these new treatment agents may offer viable alternatives to the traditional treatment of CRPC to decrease disease progression and improve overall survival.

Management of metastatic castration-resistant prostate cancer after first-line docetaxel

Although chemotherapy, based on docetaxel, is now established in the management of metastatic castration-resistant prostate cancer (mCRPC), until recently, there has been no treatment licensed for use in the second line in men whose disease progresses during or after docetaxel therapy. This article reviews the classes of agents that have shown potential in this setting, notably chemotherapy drugs, hormonal therapies, immunotherapies, anti-angiogenic drugs, and clusterin-targeted therapy.

Drug development for metastatic castration-resistant prostate cancer: current status and future perspectives

Prostate cancer represents a third of all newly diagnosed cancers in men in the USA with an estimated incidence of 192,280 cases and 27,360 deaths in 2009. It continues to be a major cause of cancer-related morbidity and mortality, and there is an urgent need for new treatments. Historically, systemic therapy options were limited after progression on docetaxel-based chemotherapy. This article reviews current data on the novel therapeutics demonstrating activity in metastatic castration-resistant prostate cancer and their future role in the treatment of this disease with a poor prognosis.

Epothilones in the treatment of ovarian cancer

Epothilones are a new group of microtubule-stabilizing agents that have demonstrated antitumor activity in taxane-resistant models. Taxanes remain some of the most active cytotoxic agents in current cancer therapy. Primary or acquired resistance to taxanes in tumor cells partly prevents their long-term efficacy. Certain side effects, such as myelosupression or irreversible neuropathy, can also limit prolonged taxane administration. Epothilone B (EPO906; patupilone), a natural compound, and its semisynthetic derivative, ixabepilone (BMS-247550), differ in their pharmacokinetic and toxicity profiles. Ovarian cancer patients frequently relapse after first-line treatment based on platinum–taxane doublets. Therefore, epothilones might represent a therapeutic alternative in this setting. Patupilone and ixabepilone have undergone parallel clinical development, but their future role in ovarian cancer therapeutics remains ill defined.

Synergistic activity of ixabepilone plus other anticancer agents: preclinical and clinical evidence

Ixabepilone demonstrates marked synergistic activity in combination with capecitabine, which served as the rationale for the evaluation of this combination in the clinic. Ixabepilone plus capecitabine is currently approved for patients with locally advanced or metastatic breast cancer (MBC) progressing after treatment with an anthracycline and a taxane; approval was based on the results of two phase III trials comparing the combination with capecitabine monotherapy. An array of preclinical studies in multiple solid tumor types show that ixabepilone demonstrates therapeutic synergy with targeted therapies including trastuzumab, bevacizumab, brivanib, and cetuximab; with immune-modulating agents such as anti-CTLA-4 antibody; and with other chemotherapy drugs such as irinotecan and epirubicin. Notably, experiments in several xenograft models show that ixabepilone provides greater antitumor synergism when combined with bevacizumab than either paclitaxel or nab-paclitaxel combined with bevacizumab. These preclinical findings provide a foundation for ongoing phase II clinical trials using ixabepilone in combination with trastuzumab or lapatinib in HER2-positive breast cancer; with bevacizumab in breast cancer, endometrial cancer, renal cancer, and non-small cell lung cancer (NSCLC); with cetuximab in breast cancer, NSCLC, and pancreatic cancer; and with brivanib, dasatinib, sorafinib, sunitinib, or vorinostat in MBC. Preliminary results from several of these trials suggest that ixabepilone-based combinations have promising anticancer activity.

Horizon scanning for novel therapeutics for the treatment of prostate cancer

IMPORTANCE OF THE FIELD

Treatment options for patients with advanced prostate cancer (PCa) remain limited. Improved understanding of the underlying molecular drivers of prostate cancer pathogenesis, progression and resistance development has provided the fundamental basis for rational targeted drug design.

AREAS COVERED IN THIS REVIEW

This review will discuss the most recent developments in the field of prostate cancer therapies including key findings such as the identification of ETS gene rearrangements, the dissection of prostate cancer molecular heterogeneity and the discovery that castration-resistant prostate cancer (CRPC) remains androgen-driven despite the androgen-depleted milieu, thus making androgen receptor signaling a continued focus of molecularly targeted treatments. A multitude of new molecularly targeted agents are in clinical development and are highly likely to change the current treatment paradigm.

WHAT THE READER WILL GAIN

This review will outline the current clinical development of molecular targeted treatments in CRPC.

TAKE HOME MESSAGE

Unraveling the complex molecular biology that underpins this heterogeneous disease may pave the way to personalized therapy with a wide range of rationally targeted agents and combination treatments. In conclusion, we can predict that the rational clinical development of new targeted drugs will improve the outcome of men with prostate cancer in the years ahead.

Bladder cancer: can we move beyond chemotherapy?

Since the advent of cisplatin-based chemotherapy, cytotoxic combination chemotherapy remains the mainstay of treatment for locally advanced and metastatic urothelial malignancies. The current paradigm of combining novel agents with cytotoxic chemotherapy without any understanding of the underlying biology of urothelial cancer has limited the impact of developing novel agents for this disease. Current research investigating the biology of bladder cancer, including the role of p53, EMT, EGFR-related pathways, and anti-angiogenic pathways, may potentially impact the future development of novel agents targeting urothelial malignancies. Additionally, the use of novel gene therapy to mediate enhanced interferon expression in the bladder using adenoviral vectors, and enhancing tumor recognition strategies using the immune system with vaccines and anti-CTLA4 antibodies, are of interest. It is hoped that through these efforts we may soon move beyond the traditional cytotoxic chemotherapy paradigm, developing combinations that are more active and less toxic for all patients with urothelial cancer.

Update on castrate-resistant prostate cancer: 2010

PURPOSE OF REVIEW

Prostate cancer remains a medical dilemma and a major cause of morbidity and mortality in many western countries. It represents the most common cancer in US men, with an estimated 192 280 new cases diagnosed in 2009. The median survival for men with metastatic castrate-resistant prostate cancer is 1-2 years, with improvements in survival seen primarily with docetaxel-based therapies. The purpose of this article is to discuss developments of novel agents in the field of metastatic castration-resistant prostate cancer (CRPC), including new cytotoxic agents, immune-based therapies, circulating tumor markers and targeting agents.

RECENT FINDINGS

During this past year, several promising approaches yielded disappointing results in the phase III setting (GVAX); nonetheless, expectations for other agents (Abiraterone, MDV3100, Zibotentan, immunotherapy agents) still remain high.

SUMMARY

Systemic therapy options are limited in CRPC and survival benefit remains to be seen with the new therapies. Circulating tumor cells continue to provide important prognostic information and will likely become an important aspect of future clinical decision-making.

Update on options for treatment of metastatic castration-resistant prostate cancer

BACKGROUND

Prostate cancer is one of the most common cancers in men in US and European countries. Despite having a favorable prognosis, the incidence of incurable metastatic disease and mortality in the US is about 28,000 per year. Although hormone-based androgen deprivation therapies typically result in rapid responses, nearly all patients eventually develop progressive castration-resistant disease state. With readily available prostate-specific antigen (PSA) testing, most of these patients are asymptomatic and manifest progression simply as a rising PSA. In patients with castration-resistant prostate cancer (CRPC), the median survival is about 1-2 years, with improvements in survival seen mostly with docetaxel-based regimens. The purpose of this article is to review the recent developments in the treatment of advanced CRPC.

RECENT FINDINGS

Since the two landmark trials (TAX-327 and Southwest Oncology Group 99-16) in CRPC, several newer cytotoxic drugs (epothilones, satraplatin), targeted agents (abiraterone, MDV3100) and vaccines have been tested in phase II and III setting with promising results.

CONCLUSIONS

The role of newer agents in the treatment of CRPC still needs to be validated by phase III trials, which are currently ongoing. Whilst the novel biomarkers, 'circulating tumor cells', have been shown to provide important prognostic information and are anticipated to be incorporated in future clinical decision-making, their exact utility and relevance calls for a larger prospective validation.

A phase II trial of the epothilone B analog ixabepilone (BMS-247550) in patients with metastatic melanoma

Background

Ixabepilone (BMS-247550), an epothilone B analog, is a microtubule stabilizing agent which has shown activity in several different tumor types and preclinical models in melanoma. In an open label, one-arm, multi-center phase II trial the efficacy and toxicity of this epothilone was investigated in two different cohorts: chemotherapy-naïve (previously untreated) and previously treated patients with metastatic melanoma.

Methodology/Principal Findings

Eligible patients had histologically-confirmed stage IV melanoma, with an ECOG performance status of 0 to 2. Ixabepilone was administered at a dose of 20 mg/m² on days 1, 8, and 15 during each 28-day cycle. The primary endpoint was response rate (RR); secondary endpoints were time to progression (TTP) and toxicity. Twenty-four patients were enrolled and 23 were evaluable for response. Initial serum lactate dehydrogenase (LDH) levels were elevated in 6/11 (55%) of the previously treated and in 5/13 (38%) of the previously untreated patients. No complete or partial responses were seen in either cohort. One patient in the previously treated group developed neutropenia and fatal septic shock. Seventeen patients (8 in the previously untreated group and 9 in the previously treated group) progressed after 2 cycles, whereas six patients (3 in each group) had stable disease after 2–6 cycles. Median TTP was 1.74 months in the previously untreated group (95% CI = 1.51 months, upper limit not estimated) and 1.54 months in the previously treated group (95% CI = 1.15 months, 2.72 months). Grade 3 and/or 4 toxicities occurred in 5/11 (45%) of previously untreated and in 5/13 (38%) of previously treated patients and included neutropenia, peripheral neuropathy, fatigue, diarrhea, and dyspnea.

Conclusions/Significance

Ixabepilone has no meaningful activity in either chemotherapy-naïve (previously untreated) or previously treated patients with metastatic melanoma. Further investigation with ixabepilone as single agent in the treatment of melanoma is not warranted.

Trial registration

Clinical Trials.gov NCT00036764

Emerging drugs for prostate cancer

Prostate cancer mortality usually occurs as a result of castrate resistant disease. Many approaches are currently being evaluated to improve the treatment of this condition. These include drugs that induce androgen deprivation, that is, LHRH antagonists; more active or less toxic chemotherapy agents; immunologic approaches, including passive and active immunization; drugs that target the androgen receptor and/or androgen synthesis; drugs that target specific pathways, including tyrosine kinase inhibitors, angiogenesis inhibitors, endothelin antagonists and matrix metalloproteinase inhibitors; and antioxidants and cell cycle inhibitors. Many of these agents seem promising. The rationale, biologic activity and therapeutic results of these emerging drugs are reviewed.

[Palliative systemic therapy of castration-resistant prostate cancer: current developments]

Androgen withdrawal or surgical castration remains the standard therapy for advanced prostate cancer disease. Even for castration-resistant prostate cancer the therapeutic option of docetaxel-based chemotherapy is well studied and defined. Facing disease progression after docetaxel-based therapy there are multiple options to continue therapy but the evidence level is rather poor. In the last few years targeted therapy and immunomodulation have been the focus of clinical trials. The presented manuscript intends to provide an overview of classical cytostatic agents, endothelin inhibitors, immunotherapy, modified hormone therapy, multikinase inhibitors and radionuclide approaches which are currently under investigation for implementation in the clinical setting.