Synergistic antitumor activity of ixabepilone (BMS-247550) plus bevacizumab in multiple in vivo tumor models

Randomised phase II trial of weekly ixabepilone ± biweekly bevacizumab for platinum-resistant or refractory ovarian/fallopian tube/primary peritoneal cancer

BACKGROUND

This multi-center RP2 study assessed activity/safety of ixabepilone + bevacizumab compared to ixabepilone in platinum-resistant/refractory ovarian/fallopian tube/primary peritoneal cancer. Additional objectives were to examine the role of prior bevacizumab and taxanes, and explore class III-ß-tubulin (TUBB3) as a predictive biomarker.

METHODS

Participants were randomised to receive ixabepilone 20 mg/m2 days 1, 8, 15 with (IXA + BEV) or without (IXA) bevacizumab 10 mg/kg days 1, 15 every 28 days. Patients were stratified by prior BEV. The primary endpoint was PFS. OS, safety, and ORR served as secondary endpoints.

RESULTS

Among 76 evaluable patients who received IXA + BEV (n = 39) compared to IXA (n = 37), the ORR was 33% (n = 13) versus 8% (n = 3)(P = 0.004), durable at 6 months in 37% (n = 14) and 3% (n = 1) (P < 0.001). BEV significantly improved PFS (median:5.5 vs 2.2 months, HR = 0.33, 95%CI 0.19-0.55, P < 0.001) and OS (median:10.0 vs 6.0 months, HR = 0.52, 95%CI 0.31-0.87, P = 0.006). Both regimens were well-tolerated. TUBB3 expression did not predict response. Subgroup analyses revealed minimal effect of prior BEV or taxane resistant/refractory status on response to IXA + BEV.

CONCLUSIONS

IXA + BEV is a well-tolerated, effective combination for platinum/taxane-resistant ovarian cancer that extends PFS and likely OS relative to IXA monotherapy. Prior receipt of BEV should not preclude the use of IXA + BEV. TUBB3 is not a predictive biomarker.

CLINICAL TRIAL REGISTRATION

NCT3093155.

Dietary 2-deoxy-D-glucose impairs tumour growth and metastasis by inhibiting angiogenesis

Accumulating evidence suggests the antiangiogenic potential of the glycolytic inhibitor 2-deoxy-D-glucose (2-DG) among the anticancerous properties of this drug. In the present studies, we investigated the antiangiogenic effects of dietary 2-DG on tumour (Lewis lung carcinoma [LLC]) as well as ionising radiation-induced angiogenesis in mouse models. Dietary 2-DG reduced the serum vascular endothelial growth factor levels (∼40%) in LLC-bearing mice along with a significant inhibition of tumour growth and metastases. In vivo Matrigel plug assays showed significant decrease in vascularisation, Fluorescein isothiocyanate (FITC)-dextran fluorescence and factor VIII-positive cells in the plugs from 2-DG-fed mice, supporting the notion that dietary 2-DG significantly suppresses the tumour-associated and radiation-induced angiogenesis. 2-DG inhibited the glucose usage and lactate production as well as ATP levels of human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner, accompanied by growth inhibition and loss of viability in vitro. Furthermore, 2-DG inhibited the capillary-like tube formation in Matrigel as well as migration and transwell invasion by HUVECs, which are functional indicators of the process of angiogenesis. These results suggest that dietary 2-DG inhibits processes related to angiogenesis, which can impair the growth and metastasis of tumours.

Endocrine Toxicity of Cancer Immunotherapy Targeting Immune Checkpoints

Immune checkpoints are small molecules expressed by immune cells that play critical roles in maintaining immune homeostasis. Targeting the immune checkpoints cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD-1) with inhibitory antibodies has demonstrated effective and durable antitumor activity in subgroups of patients with cancer. The US Food and Drug Administration has approved several immune checkpoint inhibitors (ICPis) for the treatment of a broad spectrum of malignancies. Endocrinopathies have emerged as one of the most common immune-related adverse events (irAEs) of ICPi therapy. Hypophysitis, thyroid dysfunction, insulin-deficient diabetes mellitus, and primary adrenal insufficiency have been reported as irAEs due to ICPi therapy. Hypophysitis is particularly associated with anti-CTLA-4 therapy, whereas thyroid dysfunction is particularly associated with anti-PD-1 therapy. Diabetes mellitus and primary adrenal insufficiency are rare endocrine toxicities associated with ICPi therapy but can be life-threatening if not promptly recognized and treated. Notably, combination anti-CTLA-4 and anti-PD-1 therapy is associated with the highest incidence of ICPi-related endocrinopathies. The precise mechanisms underlying these endocrine irAEs remain to be elucidated. Most ICPi-related endocrinopathies occur within 12 weeks after the initiation of ICPi therapy, but several have been reported to develop several months to years after ICPi initiation. Some ICPi-related endocrinopathies may resolve spontaneously, but others, such as central adrenal insufficiency and primary hypothyroidism, appear to be persistent in most cases. The mainstay of management of ICPi-related endocrinopathies is hormone replacement and symptom control. Further studies are needed to determine (i) whether high-dose corticosteroids in the treatment of ICPi-related endocrinopathies preserves endocrine function (especially in hypophysitis), and (ii) whether the development of ICPi-related endocrinopathies correlates with tumor response to ICPi therapy.

A Phase II Multi-Center Study of Bevacizumab in Combination with Ixabepilone in Subjects with Advanced Renal Cell Carcinoma

Lessons Learned.

Accrual to renal cell carcinoma trials remains a challenge despite the lack of prolonged response to the available treatments.

The observation of three responses among the 30 patients with median progression‐free survival and overall survival of 8.3 and 15 months, respectively, indicates the combination has some activity, but it is not sufficient for further development.

Background.

Treatment of metastatic renal cell carcinoma (mRCC) remains suboptimal. Preclinical data have previously shown that ixabepilone, a microtubule‐stabilizing agent approved for the treatment of breast cancer, is active in taxane‐sensitive and ‐resistant cells. In this single‐arm phase II trial, we investigated a combination of ixabepilone plus bevacizumab in patients with refractory mRCC.

Methods.

We enrolled 30 patients with histologically confirmed mRCC, clear cell subtype, who had not been previously treated with ixabepilone or bevacizumab but had received at least one prior U.S. Food and Drug Administration (FDA)‐approved treatment for renal cell carcinoma (RCC). The treatment regimen consisted of 6 mg/m² ixabepilone per day for 5 days and 15 mg/kg bevacizumab every 21 days. After 6 cycles, the treatment interval could be extended to every 28 days. The primary endpoint was the objective response rate according to the Response Evaluation Criteria in Solid Tumors (RECIST). Secondary endpoints were progression‐free survival (PFS), overall survival (OS), and the toxicity of the combination.

Results.

The median number of prior therapies was two (range per patient one to five). Patients received a median of 8 cycles of ixabepilone plus bevacizumab (range 2–54). The median follow‐up was 36.4 months (range 23.5–96.5). Nineteen patients (63.3%) had stable disease as a best response. Three patients (10%) had a partial response. The median PFS was 8.3 months (95% confidence interval [CI], 4.9–10.6) and the median OS was 15.0 months (95% CI, 11.3–28.8). The total number of cycle for safety evaluation was 289. Grade 3/4 adverse events (>5% incidence) included lymphopenia (16.7%), hypertension (6.7%), and leukopenia (6.7%).

Conclusion.

The combination of ixabepilone and bevacizumab was well tolerated, with modest activity in second ‐ or later‐line mRCC, but it is not recommended as a therapy without further clinical development. Alternative combinations with these agents could be explored in future studies.

Systematic review of ixabepilone for treating metastatic breast cancer

BACKGROUND

Ixabepilone is now a Food and Drug Administration-approved therapeutic option for patients with metastatic breast cancer (MBC) whose disease has progressed despite prior anthracycline and taxane therapy. We conducted a systematic review and meta-analysis to systematically evaluate the efficacy and safety of ixabepilone for treating metastatic breast cancer.

METHODS

A systematic review and meta-analysis were conducted. Randomized controlled studies applying ixabepilone for treating MBC were included. The primary outcome was Overall Survival (OS). The authors of primary articles were contacted and methodological quality was evaluated. Subgroups were drawn based on intervention measures; heterogeneity and bias were discussed.

RESULTS

Eight studies with 5247 patients were included. Compared with a weekly schedule, a triweekly schedule of ixabepilone was better at improving overall response rate (ORR), while there were no differences in improving OS and progression-free survival (PFS). Ixabepilone plus capecitabine was superior to capecitabine monotherapy in improving OS, PFS and ORR. Paclitaxel was more effective than ixabepilone in terms of OS and PFS. There was no difference in the improvement of ORR, clinical benefit rate (CBR) and disease control rate (DCR) between ixabepilone and eribulin.

CONCLUSIONS

Current evidence suggests that a triweekly schedule of ixabepilone is more effective than weekly dosing in improving ORR. Use of ixabepilone in combination with capecitabine possesses superior clinical efficacy to the use of capecitabine alone. Paclitaxel was more effective than ixabepilone in terms of OS and PFS. The efficacy and safety between ixabepilone and eribulin were identical.

Evaluation of the pharmacokinetics of ixabepilone for the treatment of breast cancer

INTRODUCTION

Chemotherapeutic agents, such as anthracyclines, taxanes and fluoropyrimidines, have significantly improved the outcome of breast cancer patients. However, mechanisms of resistance limit the effectiveness of these drugs. The microtubule-stabilizing agent ixabepilone has been approved for treatment of metastatic breast cancer (MBC) patients resistant or refractory to taxanes, anthracycline and capecitabine.

AREAS COVERED

In this review, we summarized data on pharmacodynamics, pharmacokinetics, preclinical and clinical studies of ixabepilone in breast cancer. This article was compiled through searches on ixabepilone up to March 2015 in the PubMed and the clinicaltrials.gov databases; the FDA and European Medicine Agency (EMA) websites; and the ASCO and AACR proceedings.

EXPERT OPINION

Ixabepilone is a well-tolerated and effective drug in MBC at the approved dose. The most important challenges that ongoing clinical trials are still addressing are: the optimal dosing schedule that might improve the risk/benefit ratio, the clinical efficacy of ixabepilone in early breast cancer, the efficacy in triple-negative breast cancer (TNBC) patients and the identification of biomarkers predictive of response.

Sorafenib Plus Ixabepilone as First-Line Treatment of Metastatic HER2-Negative Breast Cancer: A Sarah Cannon Research Institute Phase I/II Trial

BACKGROUND

The purposes of the present phase I/II trial were (1) to define tolerable doses of ixabepilone and sorafenib when used in combination and (2) to evaluate the efficacy and toxicity of this combination in the treatment of patients with human epidermal growth factor receptor-negative metastatic breast cancer (MBC).

PATIENTS AND METHODS

The eligible patients had human epidermal growth factor receptor-negative MBC and had not received previous chemotherapy in the metastatic setting. All patients received ixabepilone intravenously on day 1 of each 21-day treatment cycle; sorafenib was administered orally twice daily. Patients in phase II received the maximum doses identified in phase I. The patients were reevaluated after the completion of 3 treatment cycles; treatment continued until disease progression or intolerable toxicity. A total of 67 patients were required in phase II to demonstrate increased median progression-free survival from 4.2 to 6.2 months (90% power, α = 0.05).

RESULTS

Ten patients entered the phase I portion; the maximum tolerated doses were ixabepilone 32 mg/m(2) and sorafenib 400 mg orally twice daily. A total of 76 patients were treated at the phase II dose. The median progression-free survival was 4.8 months (95% confidence interval, 3.5-6.3 months). The overall response rate was 37%. The regimen was difficult to tolerate for many patients; 20 patients discontinued because of toxicity, and dose reductions were frequent. The common toxicities included neutropenia, fatigue, rash, and neuropathy.

CONCLUSION

The combination of ixabepilone and sorafenib was poorly tolerated as first-line treatment of patients with MBC. The activity of the combination was similar to the activity previously reported with single-agent ixabepilone or taxanes. Further development of this combination is not recommended.

A Phase I Clinical, Pharmacokinetic, and Pharmacodynamic Study of Weekly or Every Three Week Ixabepilone and Daily Sunitinib in Patients with Advanced Solid Tumors

PURPOSE

To evaluate the safety, MTD, pharmacokinetics/pharmacodynamics, and early clinical activity of ixabepilone given either weekly or every 3 weeks in combination with daily sunitinib in patients with advanced solid tumors.

EXPERIMENTAL DESIGN

Eligible patients received either weekly (schedule A) or every 3 weeks (schedule B) ixabepilone at escalating doses (schedule A: 7.5, 15, or 20 mg/m(2); schedule B: 20, 30, or 40 mg/m(2)), and oral sunitinib (37.5 mg daily), starting on day 8 of cycle 1. Dose-limiting toxicities (DLT) were assessed during cycle 1.

RESULTS

The ixabepilone and sunitinib combination was fairly well tolerated. DLTs were observed in 3 subjects (1 in schedule 3A and 2 in schedule 3B). The most common grade 3-4 hematologic and nonhematologic adverse events were leukopenia and fatigue, respectively. Four patients (3 in schedule A) achieved a partial response, while 13 patients had stable disease. Nine of 17 heavily pretreated colorectal cancer patients had clinical benefit. Coadministration of sunitinib with ixabepilone on a weekly (but not every 3 week) schedule was associated with a significant increase in the half-life and a significant decrease in the clearance of ixabepilone. Correlative studies demonstrated a significant association between higher baseline plasma angiogenic activity (PAA) and clinical benefit in schedule A patients. Weekly, but not every 3 weeks, ixabepilone led to a significant decrease in PAA postbaseline.

CONCLUSIONS

Coadministration of ixabepilone with sunitinib has acceptable toxicity and encouraging clinical activity in heavily pretreated patients, particularly in patients with metastatic colorectal cancer. Clin Cancer Res; 22(13); 3209-17. ©2016 AACR.

Mechanism of action of ixabepilone and its interactions with the βIII-tubulin isotype

Ixabepilone (Ixempra, BMS-247550), a semisynthetic analog of epothilone B, is a microtubule-targeted drug in clinical use for treatment of metastatic or locally advanced breast cancer. Ixabepilone's binding and mechanism of action on microtubules and their dynamics, as well as its interactions with isotypically altered microtubules, both in vitro and in tumor cells, have not been described. Microtubules are dynamic polymers of the protein tubulin that function in mitosis, intracellular transport, cell proliferation, and migration. They continually undergo dynamic instability, periods of slow growth and rapid shortening that are crucial to these cell functions. We determined ixabepilone's microtubule binding and polymerization effects in vitro and also determined its effects on inhibition of dynamic instability in vitro and in cells, both with and without removal of the βIII isotype of tubulin. The βIII isotype of tubulin is associated with drug resistance and tumor aggressivity. We found that removal (in vitro) and knockdown (in cells) of βIII-tubulin led to increased inhibition of microtubule dynamic instability by ixabepilone. Depletion of βIII-tubulin from MCF7 human breast cancer cells also induced increased mitotic arrest by ixabepilone. Thus, βIII-tubulin expression suppresses the antitumor effects of ixabepilone, indicating that increased βIII-tubulin may be an important contributor to the development of resistance to ixabepilone.

Epothilones

Epothilones A and B are naturally occurring microtubule stabilizers with nanomolar or even sub-nanomolar activity against human cancer cells in vitro and potent in vivo antitumor activity against multidrug-resistant tumors. Over the last decade, ten epothilonetype agents have entered clinical trials in humans; of these, the epothilone B lactam ixabepilone (BMS-247550; Ixempra®) was approved by the FDA for breast cancer treatment in 2007. Numerous synthetic and semisynthetic analogs of epothilones have been prepared and their in vitro and (in selected cases) in vivo biological activity has been determined, producing a wealth of SAR information on this compound family. This chapter will provide a brief summary of the in vitro and in vivo biological properties of epothilone B (Epo B). The major part of the discussion will then be organized around those epothilone analogs that have entered clinical development. For each analog the underlying synthetic chemistry and the most important preclinical features will be reviewed, together with the properties of some important related structures.

Targeted therapy in uterine serous carcinoma: an aggressive variant of endometrial cancer

Uterine serous carcinoma (USC) is a highly aggressive variant of endometrial cancer. Although it only represents less than 10% of all cases, it accounts for a disproportionate number of deaths from endometrial cancer. Comprehensive surgical staging followed by carboplatin and paclitaxel chemotherapy represents the mainstay of USC therapy. Vaginal cuff brachytherapy is also of potential benefit in USC. Recent whole-exome sequencing studies have demonstrated gain of function of the HER2/NEU gene, as well as driver mutations in the PIK3CA/AKT/mTOR and cyclin E/FBXW7 oncogenic pathways in a large number of USCs. These results emphasize the relevance of these novel therapeutic targets for biologic therapy of chemotherapy-resistant recurrent USC.

Drug interactions with sunitinib

PURPOSE

Sunitinib is a tyrosine kinase inhibitor indicated for the treatment of gastrointestinal stromal tumor, advanced renal cell carcinoma, and pancreatic neuroendocrine tumors. The aim of this article is to describe the pharmacological interactions between sunitinib and commonly prescribed drugs.

METHOD

We reviewed available information on pharmacological interactions between sunitinib and concomitantly prescribed drugs. Drugs were grouped into different therapeutic groups according to the Anatomical Therapeutic Chemical (ATC) classification.

RESULTS

Sunitinib interacts with CYP3A4 inducers or inhibitors and with P-glycoprotein and ABCG2 substrates. Pharmacodynamic interactions with drugs have also been found.

CONCLUSION

Current information on drug interactions between sunitinib and other drugs is scarce and most of the times it is difficult to apply to clinical practice. Even so, this difficulty in managing drug interactions should not be a reason to ignore them as they can help to explain intolerances and treatment failures.

AMG 900, a small-molecule inhibitor of aurora kinases, potentiates the activity of microtubule-targeting agents in human metastatic breast cancer models

Breast cancer is the most prevalent malignancy affecting women and ranks second in cancer-related deaths, in which death occurs primarily from metastatic disease. Triple-negative breast cancer (TNBC) is a more aggressive and metastatic subtype of breast cancer that is initially responsive to treatment of microtubule-targeting agents (MTA) such as taxanes. Recently, we reported the characterization of AMG 900, an orally bioavailable, potent, and highly selective pan-Aurora kinase inhibitor that is active in multidrug-resistant cell lines. In this report, we investigate the activity of AMG 900 alone and in combination with two distinct classes of MTAs (taxanes and epothilones) in multidrug-resistant TNBC cell lines and xenografts. In TNBC cells, AMG 900 inhibited phosphorylation of histone H3 on Ser(10), a proximal substrate of Aurora-B, and induced polyploidy and apoptosis. Furthermore, AMG 900 potentiated the antiproliferative effects of paclitaxel and ixabepilone at low nanomolar concentrations. In mice, AMG 900 significantly inhibited the growth of MDA-MB-231 (F(11); parental), MDA-MB-231 (F(11)) PTX-r (paclitaxel-resistant variant), and DU4475 xenografts. The combination of AMG 900 with docetaxel enhanced tumor inhibition in MDA-MB-231 (F(11)) xenografts compared with either monotherapy. Notably, combining AMG 900 with ixabepilone resulted in regressions of MDA-MB-231 (F(11)) PTX-r xenografts, in which more than 50% of the tumors failed to regrow 75 days after the cessation of drug treatment. These findings suggest that AMG 900, alone and in combination with MTAs, may be an effective intervention strategy for the treatment of metastatic breast cancer and provide potential therapeutic options for patients with multidrug-resistant tumors.

EZH2 inhibition: targeting the crossroad of tumor invasion and angiogenesis

Tumor angiogenesis and metastatic spreading are two highly interconnected phenomena, which contribute to cancer-associated deaths. Thus, the identification of novel strategies to target angiogenesis and metastatic spreading is crucial. Polycomb genes are a set of epigenetic effectors, structured in multimeric repressive complexes. EZH2 is the catalytic subunit of Polycomb repressive complex 2 (PRC2), which methylates histone H3 lysine 27, thereby silencing several tumor-suppressor genes. EZH2 is essential for cancer stem cell self-renewal. Interestingly, cancer stem cells are thought to be the seeds of metastatic spreading and are able to differentiate into tumor-associated endothelial cells. Pre-clinical studies showed that EZH2 is able to silence several anti-metastatic genes (e.g., E-cadherin and tissue inhibitors of metalloproteinases), thereby favoring cell invasion and anchorage-independent growth. In addition, EZH2 seems to play a crucial role in the regulation of tumor angiogenesis. High EZH2 expression predicts poor prognosis, high grade, and high stage in several cancer types. Recently, a small molecule inhibitor of PRC2 (DZNeP) demonstrated promising anti-tumor activity, both in vitro and in vivo. Interestingly, DZNeP was able to inhibit cancer cell invasion and tumor angiogenesis in prostate and brain cancers, respectively. At tumor-inhibiting doses, DZNeP is not harmful for non-transformed cells. In the present manuscript, we review current evidence supporting a role of EZH2 in metastatic spreading and tumor angiogenesis. Using Oncomine datasets, we show that DZNeP targets are specifically silenced in some metastatic cancers, and some of them may inhibit angiogenesis. Based on this evidence, we propose the development of EZH2 inhibitors as anti-angiogenic and anti-metastatic therapy.

A randomized, phase II, three-arm study of two schedules of ixabepilone or paclitaxel plus bevacizumab as first-line therapy for metastatic breast cancer

The aim of this phase II trial was to estimate the objective response rate (ORR) of two different schedules of ixabepilone [weekly or every 3 weeks (Q3W)] combined with bevacizumab, relative to a reference arm of weekly paclitaxel and bevacizumab. Patients with human epidermal growth factor receptor 2-normal, chemotherapy-naïve metastatic breast cancer (MBC) were randomized 3:3:2 to ixabepilone 16 mg/m(2) weekly plus bevacizumab 10 mg/kg Q2W (Arm A: n = 46); ixabepilone 40 mg/m(2) Q3W (reduced to 32 mg/m(2) after four cycles of treatment) plus bevacizumab 15 mg/kg Q3W (Arm B: n = 45); or paclitaxel 90 mg/m(2) weekly plus bevacizumab 10 mg/kg intravenous infusion Q2W (Arm C: n = 32). Of 123 randomized patients, 122 were treated. All were followed for ≥19 months; 5 % of patients remained on study treatment at the time of this analysis. Grade 3 or 4 neutropenia was more common in Arm B (60 %) than Arms A (16 %) or C (22 %); other adverse events were similar. The investigator-assessed ORR was 48, 71, and 63 % for Arms A, B, and C, respectively. Median progression-free survival (randomized patients) was 9.6 months in Arm A, 11.9 months in Arm B, and 13.5 months in Arm C. In conclusion, ixabepilone Q3W plus bevacizumab has clinical activity as first-line therapy for MBC relative to paclitaxel plus bevacizumab, but with significantly greater risk of grade 3 or 4 neutropenia. In addition, these data suggest that weekly dosing of ixabepilone may be less active than Q3W dosing, but with less neutropenia.

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.

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.

Advancements in the Treatment of Metastatic Breast Cancer (MBC): The Role of Ixabepilone

Successful management of breast cancer in the metastatic setting is often confounded by resistance to chemotherapeutics, in particular anthracyclines and taxanes. The limited number of effective treatment options for patients with more aggressive biological subtypes, such as triple-negative metastatic breast cancer, is especially concerning. As such, a therapy clinically proven to be effective in this subtype would be of great value. Ixabepilone, a novel synthetic lactam analog of epothilone B, demonstrated better clinical outcomes in metastatic disease, particularly in triple-negative breast cancer. Most recently, studies have shown the activity of ixabepilone in the neoadjuvant setting, suggesting a role for this drug in primary disease. Notably, treating in the neoadjuvant setting might allow clinicians to explore the predictive value of biomarkers and response to treatment, as pharmacogenomic approaches to therapy continue to evolve. In this article, we review the efficacy and safety data of ixabepilone as a monotherapy and as a component of combination therapy for metastatic and primary breast cancer.

Beyond taxanes: the next generation of microtubule-targeting agents

Taxanes are a standard first-line option for metastatic breast cancer (MBC), but their utility may be limited by primary or acquired resistance. New microtubule-targeting agents have been developed to overcome taxane resistance and provide additional options for improving patient outcomes. This article reviews these alternative microtubule-targeting agents and their potential clinical benefits for MBC patients. Relevant clinical data were compiled through searches within PubMed and congress abstract databases. Ixabepilone, a novel microtubule-stabilizing drug approved by the US Food and Drug Administration (FDA), has proven efficacy across multiple lines of therapy, including patients with taxane-resistant/refractory disease. In phase III trials, ixabepilone plus capecitabine significantly improved progression-free survival compared with capecitabine alone in anthracycline/taxane-pretreated patients. Eribulin has recently been approved by the FDA and by the European Medicines Agency for the treatment of patients with MBC who have received at least two prior chemotherapy regimens for late-stage disease. In a phase III trial, eribulin extended overall survival compared with the physician’s treatment choice in heavily pretreated MBC patients. In addition, several investigational microtubule-targeting agents may have therapeutic potential in MBC. The development of new microtubule-targeting agents helps to address the need for additional effective regimens for patients progressing after standard treatment with anthracycline- and taxane-containing regimens.

Src family kinases and paclitaxel sensitivity

Src-family Kinases (SFKs) participate in the regulation of proliferation, differentiation, apoptosis, autophagy, adhesion, migration, invasion and angiogenesis in normal and cancer cells. Abnormal expression of SFKs has been documented in cancers that arise in breast, colon, ovary, melanocyte, gastric mucosa, head and neck, pancreas, lung, and brain. Targeting SFKs in cancer cells has been shown to be a promising therapeutic strategy in solid tumors, particularly in ovarian, colon and breast cancers. Paclitaxel is one of most widely used chemotherapeutic agents for the management of ovarian, breast, lung and head/neck cancers. As a microtubule-stabilizing agent, paclitaxel possesses both mitosis-dependent and mitosis-independent activities against cancer cells. A variety of mechanisms such as deregulation of P-glycoprotein, alteration of tubulin isotypes, alteration of microtubule-regulatory proteins, deregulation of apoptotic signaling pathways, mutation of tubulins and overexpression of copper transporters have been implicated in the development of primary or secondary resistance to paclitaxel. By affecting cancer cell survival, proliferation, autophagy, microtubule stability, motility, and/or angiogenesis, SFKs interact with mechanisms that regulate paclitaxel sensitivity. Inhibition of SFKs can potentiate the anti-tumor activity of paclitaxel by enhancing apoptosis, autophagy and microtubule stability. Based on pre-clinical observations, administration of SFK inhibitors in combination with paclitaxel could improve treatment for ovarian, breast, lung and head/neck cancers. Identification and validation of predictive biomarkers could also permit personalization of the therapy.

Comparison of neuropathy-inducing effects of eribulin mesylate, paclitaxel, and ixabepilone in mice

Chemotherapy-induced neurotoxicity is a significant problem associated with successful treatment of many cancers. Tubulin is a well-established target of antineoplastic therapy; however, tubulin-targeting agents, such as paclitaxel and the newer epothilones, induce significant neurotoxicity. Eribulin mesylate, a novel microtubule-targeting analogue of the marine natural product halichondrin B, has recently shown antineoplastic activity, with relatively low incidence and severity of neuropathy, in metastatic breast cancer patients. The mechanism of chemotherapy-induced neuropathy is not well understood. One of the main underlying reasons is incomplete characterization of pathology of peripheral nerves from treated subjects, either from patients or preclinically from animals. The current study was conducted to directly compare, in mice, the neuropathy-inducing propensity of three drugs: paclitaxel, ixabepilone, and eribulin mesylate. Because these drugs have different potencies and pharmacokinetics, we compared them on the basis of a maximum tolerated dose (MTD). Effects of each drug on caudal and digital nerve conduction velocity, nerve amplitude, and sciatic nerve and dorsal root ganglion morphology at 0.25 × MTD, 0.5 × MTD, 0.75 × MTD, and MTD were compared. Paclitaxel and ixabepilone, at their respective MTDs, produced significant deficits in caudal nerve conduction velocity, caudal amplitude and digital nerve amplitudes, as well as moderate to severe degenerative pathologic changes in dorsal root ganglia and sciatic nerve. In contrast, eribulin mesylate produced no significant deleterious effects on any nerve conduction parameter measured and caused milder, less frequent effects on morphology. Overall, our findings indicate that eribulin mesylate induces less neuropathy in mice than paclitaxel or ixabepilone at equivalent MTD-based doses.

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.

Endometrial carcinoma: a review of chemotherapy, drug resistance, and the search for new agents

The article examines current treatment options in patients with endometrial carcinoma, the role of drug resistance, and the rationale for the use of epothilones in treating this disease.

Adenocarcinoma of the endometrium represents the most common gynecologic malignancy in developed countries. Although early-stage cancers are effectively treated surgically, commonly without adjuvant therapy, the treatment of high-risk and advanced disease is more complex. Chemotherapy has evolved into an important modality in high-risk early-stage and advanced-stage disease, and in recurrent endometrial cancer. Taxane-based therapy consistently demonstrates the highest response rates in the first-line and salvage settings of endometrial cancer. Unfortunately, response to chemotherapy is modest and strategies are needed to predict chemotherapy-responsive and chemotherapy-resistant populations. Chemotherapy resistance mediated by overexpression of drug efflux pump proteins and mutations in β-tubulin isoforms in both primary and recurrent disease represent unique treatment challenges and highlight the need for new agents that are less susceptible to these known resistance pathways. Epothilone B analogs are novel cytotoxic agents with activity in solid tumors, including advanced/recurrent endometrial carcinoma, and may have unique properties that can overcome resistance in some settings. These agents alone and in combination represent a new therapeutic opportunity in endometrial carcinoma.

Optimizing ixabepilone treatment schedules in patients with advanced or metastatic breast cancer

The epothilone B analog, ixabepilone, demonstrates low susceptibility to drug resistance mechanisms and has demonstrated clinically meaningful efficacy in patients refractory to other chemotherapeutic options. Ixabepilone is approved by the FDA for treatment of patients with metastatic breast cancer (MBC) progressing after taxanes and anthracyclines, either in combination with capecitabine or as monotherapy if the patient has already progressed on capecitabine. Ixabepilone is generally well tolerated at the approved dose and administration schedule of 40 mg/m(2) every 3 weeks. The most commonly observed dose-limiting adverse events (AEs) associated with ixabepilone are myelosuppression and peripheral neuropathy. Dose modification including dose reduction and dosing schedule modification may be utilized to manage toxicities, but this must be based on careful hematologic, neurologic, and liver function monitoring. Other ixabepilone dose schedules are being evaluated to further improve the risk/benefit profile. Weekly and daily schedules of ixabepilone have shown useful efficacy and reasonable tolerability. A recent phase II trial compared the tolerability of ixabepilone dosed once weekly (16 mg/m(2) on Days 1, 8, and 15 of each 28-day cycle) or every 3 weeks (40 mg/m(2) on Day 1 of each 21-day cycle) in patients with MBC. Preliminary data showed that both dosing schedules had an acceptable safety profile; however, more AEs were reported in patients receiving ixabepilone every 3 weeks. Ixabepilone is also being evaluated in combination with other anticancer agents (e.g., bevacizumab and lapatinib), in earlier breast cancer settings and in other indications.

Neurophysiological and neuropathological characterization of new murine models of chemotherapy-induced chronic peripheral neuropathies

Cisplatin, paclitaxel and bortezomib belong to some of the most effective families of chemotherapy drugs for solid and haematological cancers. Epothilones represent a new family of very promising antitubulin agents. The clinical use of all these drugs is limited by their severe peripheral neurotoxicity. Several in vivo rat models have reproduced the characteristics of the peripheral neurotoxicity of these drugs. However, since only a very limited number of cancer types can be studied in immunocompetent rats, these animal models do not represent an effective way to evaluate, at the same time, the antineoplastic activity and the neurotoxic effects of the anticancer compounds. In this study, we characterized the neurophysiological impairment induced by chronic chemotherapy treatment in BALB/c mice, a strain suitable for assessing the activity of anticancer treatments. At the end of a 4-week period of treatment with cisplatin, paclitaxel, epothilone-B or bortezomib, sensory and sensory/motor nerve conduction velocities (NCV) were determined in the caudal and digital nerves and dorsal root ganglia (DRG) and sciatic nerves were collected for histopathological analysis. The electrophysiological studies revealed that all the compounds caused a statistically significant reduction in the caudal NCV, while impairment of the digital NCV was less severe. This functional damage was confirmed by the histopathological observations evidencing axonal degeneration in the sciatic nerve induced by all the drugs associated with pathological changes in DRG induced only by cisplatin and bortezomib. These results confirm the possibility to use our models to combine the study of the antineoplastic activity of anticancer drugs and of their toxic effects on the peripheral nervous system in the BALB/c mouse strain.

Gemcitabine and paclitaxel suppress the production of vascular endothelial growth factor induced by deferoxamine in human non-small cell lung cancer A549 cells

Vascular endothelial growth factor (VEGF) plays an important role in the process of angiogenesis in many types of cancer, including non-small cell lung cancer (NSCLC), and angiogenesis inhibitors and standard chemotherapy exhibit synergy though an unknown mechanism. We therefore hypothesized that cytotoxic chemotherapy influences VEGF production and analyzed VEGF production in an NSCLC A549 cell line after treatment with standard chemotherapy. Paclitaxel inhibited the production of VEGF in A549 cells, while cisplatin and erlotinib did not. Paclitaxel and gemcitabine inhibited deferoxamine (DFX) (known to mimic hypoxia)-induced VEGF production in A549 cells. Erlotinib also inhibited DFX-induced VEGF production in A549 cells slightly, while cisplatin did not. We subsequently examined the effect of the interaction between paclitaxel or gemcitabine and VEGF protein. Paclitaxel and gemcitabine did not directly affect the binding of VEGF. Since VEGF is known as one of the HIF-1 target genes, we examined the effect of paclitaxel and gemcitabine on HIF-1α levels induced by DFX in A549 cells. Paclitaxel and gemcitabine inhibited DFX-induced HIF-1α in A549 cells. These findings may be useful for future treatment schedules, including anti-cancer agents in NSCLC.

[Current impact of natural products in the discovery of anticancer drugs]

Since the middle of 1990s, the development of combinatorial chemistry along with the high throughput screening have led to some lack of interest for natural products from the pharmaceutical industry. Moreover, purification and optimization of natural compounds are very often difficult and animal experimentations need enough supply of natural sources or alternatively need sophisticated total synthesis. In oncology, this increased disinterest was also closely connected with the rapid expansion of monoclonal antibodies and synthetic protein kinase inhibitors. However since 2005, with the approval of five new drugs by the FDA (trabectedin, ixabepilone, temsirolimus, everolimus and Vinflunine), it appears that natural products are still present as direct or indirect sources of drugs. On the other hand, a third generation of natural product has arisen, which relies upon bioengineering using genetically altered producer organisms. This is particularly true of the polyketides where bioengineering harnesses their natural flexibility to expand their structural diversity. Several programs are going on to produce antibiotics, anticancer drugs or immunosuppressant. This combinatorial approach makes drug discovery by bioengineering complementary with conventional medicinal chemistry. With the approval of Mylotarg by the FDA, increased interest has also been devoted to immunoconjugates, which represent a way by which highly cytotoxic natural products such as dolastatin, calicheamycin, duocarmycin and maytansin may be targeted to cancer cells while limiting their side-effects.

The role of betaIII tubulin in predicting chemoresistance in non-small cell lung cancer

Lung cancer is a leading cause of death among adults. Non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases. For more than half of all patients diagnosis does not occur until the disease has metastasised. At this advanced stage, the 5-year survival rate is just 15%. Platinum-based chemotherapy forms the backbone of treatment for patients with advanced NSCLC and forms an important component of the therapeutic regimen for many patients with earlier stage disease. However, although a number of agents are available to partner the platinum-based compounds, treatment selection is largely empiric, and chemoresistance is a considerable barrier to improving outcomes. The identification of biologic and other markers to guide treatment selection, thus ensuring patients receive the most effective regimen for their individual tumour and avoid exposure to toxic agents from which they are unlikely to benefit, will be critical to improve outcomes for patients with NSCLC. The development of alternative agents for those patients who express predictors of a negative clinical response is of vital importance. A variety of biomarkers are emerging, including expression of DNA repair enzymes, ribonucleotide subunits and betaIII tubulin. Treatment algorithms based on elucidation of such markers to guide treatment selection can already be envisaged. For example, those patients with high betaIII tubulin expression should be considered for epothilone therapy as an alternative to taxane-based regimens. The epothilones may be preferred option as the evidence suggests that these agents retain activity versus taxane-resistant cancers. This paper reviews the evidence base for betaIII tubulin expression as a prognostic and predictive biomarker in NSCLC and briefly explores the implications for clinical decision making of this and other emerging biomarkers.

Contemporary pre-clinical development of anticancer agents--what are the optimal preclinical models?

The successful identification of novel effective anticancer drugs is largely dependent on the use of appropriate preclinical experimental models that should possibly mimic the complexity of different cancer diseases. The huge number of targets suitable for the design of new anticancer drugs is producing hundreds of novel molecules that require appropriate experimental models to investigate their mode of action and antitumour activity in order to select for clinical investigation the ones with higher chances of being clinically effective. However, our ability to predict the clinical efficacy of a new compound in the clinic based on preclinical data is still limited. This paper overviews the in vitro/in vivo preclinical systems that are currently used to test either compounds with an unknown mechanism of action or compounds designed to hit cancer-specific or cancer-related molecular targets. Examples of experimental models successfully used to identify novel compounds are provided. Xenografts are still the most commonly used in vivo models in drug development due to their high degree of reproducibility and because, in some cases, particularly when orthotopically transplanted, they maintain several biological properties of the human tumours they derive from. Genetic models are very useful for target validation, but are often not sufficiently reproducible to be used for drug evaluation. The variety of animal models can be effectively used to optimally test drugs that presumably act by a defined mode of action, but final success is highly dependent on the ability of drug development teams to integrate different expertises such as biology, chemistry, pharmacology, toxicology and clinical oncology into a clever and well orchestrated plan that keeps in consideration both the complexity of cancer diseases, involving alterations of different pathways, and the complexity of drugs whose pharmacological properties are crucial to obtain the desired effects.

Endothelial contractile cytoskeleton and microvascular permeability

Microvascular barrier dysfunction represents a significant problem in clinical conditions associated with trauma, burn, sepsis, acute respiratory distress syndrome, ischemia-reperfusion injury, and diabetic retinopathy. An important cellular mechanism underlying microvascular leakage is the generation of contractile force from the endothelial cytoskeleton, which counteracts cell-cell and cell-matrix adhesions leading to paracellular hyperpermeability. In this review, we present recent experimental evidence supporting the critical role of MLCK-activated, RhoA/ROCK-regulated contractile cytoskeleton in endothelial permeability response to inflammatory and thrombotic stimuli arising from thermal injury, activated neutrophils, vascular endothelial growth factor, and fibrinogen degradation products. Further understanding the molecular basis of microvascular barrier structure and function would contribute to the development of novel therapeutic targets for treating circulatory disorders and vascular injury.

Molecular mechanisms of endothelial hyperpermeability: implications in inflammation

Endothelial hyperpermeability is a significant problem in vascular inflammation associated with trauma, ischaemia-reperfusion injury, sepsis, adult respiratory distress syndrome, diabetes, thrombosis and cancer. An important mechanism underlying this process is increased paracellular leakage of plasma fluid and protein. Inflammatory stimuli such as histamine, thrombin, vascular endothelial growth factor and activated neutrophils can cause dissociation of cell-cell junctions between endothelial cells as well as cytoskeleton contraction, leading to a widened intercellular space that facilitates transendothelial flux. Such structural changes initiate with agonist-receptor binding, followed by activation of intracellular signalling molecules including calcium, protein kinase C, tyrosine kinases, myosin light chain kinase, and small Rho-GTPases; these kinases and GTPases then phosphorylate or alter the conformation of different subcellular components that control cell-cell adhesion, resulting in paracellular hypermeability. Targeting key signalling molecules that mediate endothelial-junction-cytoskeleton dissociation demonstrates a therapeutic potential to improve vascular barrier function during inflammatory injury.

Antivascular actions of microtubule-binding drugs

Microtubule-binding drugs (MBD) are widely used in cancer chemotherapy and also have clinically relevant antiangiogenic and vascular-disrupting properties. These antivascular actions are due in part to direct effects on endothelial cells, and all MBDs (both microtubule-stabilizing and microtubule-destabilizing) inhibit endothelial cell proliferation, migration, and tube formation in vitro, actions that are thought to correspond to therapeutic antiangiogenic actions. In addition, the microtubule-destabilizing agents cause prominent changes in endothelial cell morphology, an action associated with rapid vascular collapse in vivo. The effects on endothelial cells occur in vitro at low drug concentrations, which do not affect microtubule gross morphology, do not cause microtubule bundling or microtubule loss and do not induce cell cycle arrest, apoptosis, or cell death. Rather, it has been hypothesized that, at low concentrations, MBDs produce more subtle effects on microtubule dynamics, block critical cell signaling pathways, and prevent the microtubules from properly interacting with transient subcellular assemblies (focal adhesions and adherens junctions) whose subsequent stabilization and/or maturation are required for cell motility and cell-cell interactions. This review will focus on recent studies to define the molecular mechanisms for the antivascular actions of the MBDs, information that could be useful in the identification or design of agents whose actions more selectively target the tumor vasculature.