Total Synthesis of an Epothilone Analogue Based on the Amide-Triazole Bioisosterism.

Epothilones are 16-membered macrolides that act as microtubule-targeting agents to tackle cancer. Many synthetic analogues have been investigated for their activity, yet often based on macrolide structures. A notable exception is Ixabepilone, an azalide whose metabolic stability and pharmacokinetics are significantly improved. Exploiting the amide-triazole bioisosterism, in this work we report the synthesis of the first generation of epothilones lacking the macrolide or azalide structure, with the ester or amide linkage replaced by a triazole unit. Together with the synthesis of this new analogue, computational and biological evaluations have been performed too.

Ixabepilone related angiographically silent macular edema.

INTRODUCTION: We present a single-eyed case with a previous diagnosis of breast cancer who had intraretinal cystoid changes associated with the systemic administration of ixabepilone in her only seeing eye. To our best knowledge, this is the first reported case describing this phenomenon related to the ixabepilone administration. CASE DESCRIPTION: A 54-year-old woman with a history of breast cancer was examined due to visual deterioration in her only good left eye. The patient had undergone cataract surgery and lens implantation in her right eye following a childhood accident, but subsequently had developed a refractory glaucoma and lost her right vision. Six cycles of 40 mg/m2 systemic ixabepilone (3-hly intravenous infusion once every 3 weeks) had been administered within the past six months. Her visual decline started two weeks following the last treatment session. She was offered intravitreal anti-vascular endothelial growth factor injection elsewhere. Fluorescein angiogram showed no dye leakage whereas spectral-domain optical coherence tomography demonstrated parafoveal intraretinal cystoid changes. En-face optical coherence tomography revealed petaloid type roundish hyporeflective areas at the level of superficial and deep vascular plexus. Ixabepilone-associated cystoid maculopathy was suspected as she received only ixabepilone for the chemotherapy in the last six months. We thus recommended her not to continue ixabepilone therapy. Ten weeks after the ixabepilone cessation, intraretinal cystoid changes had resolved completely. CONCLUSION: Angiographically silent intraretinal cystoid changes may develop in association with the use of ixabepilone. Referral to an ophthalmologist should be considered for the patients experiencing visual complaints as ixabepilone cessation may lead to visual improvement and avoid unnecessary treatment.

Microtubule-Targeting Agents: Disruption of the Cellular Cytoskeleton as a Backbone of Ovarian Cancer Therapy.

Microtubules are dynamic polymers composed of α- and ß-tubulin heterodimers. Microtubules are universally conserved among eukaryotes and participate in nearly every cellular process, including intracellular trafficking, replication, polarity, cytoskeletal shape, and motility. Due to their fundamental role in mitosis, they represent a classic target of anti-cancer therapy. Microtubule-stabilizing agents currently constitute a component of the most effective regimens for ovarian cancer therapy in both primary and recurrent settings. Unfortunately, the development of resistance continues to present a therapeutic challenge. An understanding of the underlying mechanisms of resistance to microtubule-active agents may facilitate the development of novel and improved approaches to this disease.

The ixabepilone and vandetanib combination shows synergistic activity in docetaxel-resistant MDA-MB-231 breast cancer cells.

BACKGROUND: The lack of drug targets is an obstacle to the treatment of patients with triple-negative breast cancer (TNBC). At present, non-specific cytotoxic drugs are first-line agents, but the development of resistance is a major problem with these agents. The epidermal growth factor receptor (EGFR) is a potential target in some TNBCs, because its tyrosine kinase activity drives tumorigenesis. Thus, small molecule inhibitors of the EGFR in combination with cytotoxic agents could be important for the treatment of TNBCs. METHODS: The present study evaluated the efficacies of clinically approved EGFR inhibitors in combination with the cytotoxic agent ixabepilone in parental and docetaxel-resistant MDA-MB-231 cells (231C and TXT cells, respectively). Cell viability was assessed using MTT reduction assays, cell death pathways were evaluated using annexin V/7-aminoactinomycin D staining and flow cytometry and Western immunoblotting was used to assess the expression of pro- and anti-apoptotic proteins in cells. RESULTS: Ixabepilone and the EGFR inhibitors gefitinib and vandetanib inhibited 231C and TXT cell proliferation, but the alternate EGFR inhibitors erlotinib and lapatinib were poorly active. Using combination analysis, ixabepilone/vandetanib was synergistic in both cell types, whereas the ixabepilone/gefitinib combination exhibited antagonism. By flow cytometry, ixabepilone/vandetanib enhanced 231C and TXT cell death over that produced by the single agents and also enhanced caspase-3 cleavage and the pro/anti-apoptotic Bcl-2 protein ratios over ixabepilone alone. CONCLUSIONS: These findings suggest that the ixabepilone/vandetanib combination may have promise for the treatment of patients with drug-resistant TNBC.

Microtentacle Formation in Ovarian Carcinoma.

BACKGROUND: The development of chemoresistance to paclitaxel and carboplatin represents a major therapeutic challenge in ovarian cancer, a disease frequently characterized by malignant ascites and extrapelvic metastasis. Microtentacles (McTNs) are tubulin-based projections observed in detached breast cancer cells. In this study, we investigated whether ovarian cancers exhibit McTNs and characterized McTN biology. METHODS: We used an established lipid-tethering mechanism to suspend and image individual cancer cells. We queried a panel of immortalized serous (OSC) and clear cell (OCCC) cell lines as well as freshly procured ascites and human ovarian surface epithelium (HOSE). We assessed by Western blot ß-tubulin isotype, α-tubulin post-translational modifications and actin regulatory proteins in attached/detached states. We studied clustering in suspended conditions. Effects of treatment with microtubule depolymerizing and stabilizing drugs were described. RESULTS: Among cell lines, up to 30% of cells expressed McTNs. Four McTN morphologies (absent, symmetric-short, symmetric-long, tufted) were observed in immortalized cultures as well as ascites. McTN number/length varied with histology according to metastatic potential. Most OCCC overexpressed class III ß-tubulin. OCCC/OSC cell lines exhibited a trend towards more microtubule-stabilizing post-translational modifications of α-tubulin relative to HOSE. Microtubule depolymerizing drugs decreased the number/length of McTNs, confirming that McTNs are composed of tubulin. Cells that failed to form McTNs demonstrated differential expression of α-tubulin- and actin-regulating proteins relative to cells that form McTNs. Cluster formation is more susceptible to microtubule targeting agents in cells that form McTNs, suggesting a role for McTNs in aggregation. CONCLUSIONS: McTNs likely participate in key aspects of ovarian cancer metastasis. McTNs represent a new therapeutic target for this disease that could refine therapies, including intraperitoneal drug delivery.

Microtubule-Interfering Drugs: Current and Future Roles in Epithelial Ovarian Cancer Treatment.

Taxanes and epothilones are chemotherapeutic agents that ultimately lead to cell death through inhibition of normal microtubular function. This review summarizes the literature demonstrating their current use and potential promise as therapeutic agents in the treatment of epithelial ovarian cancer (EOC), as well as putative mechanisms of resistance. Historically, taxanes have become the standard of care in the front-line and recurrent treatment of epithelial ovarian cancer. In the past few years, epothilones (i.e., ixabepilone) have become of interest as they may retain activity in taxane-treated patients since they harbor several features that may overcome mechanisms of taxane resistance. Clinical data now support the use of ixabepilone in the treatment of platinum-resistant or refractory ovarian cancer. Clinical data strongly support the use of microtubule-interfering drugs alone or in combination in the treatment of epithelial ovarian cancer. Ongoing clinical trials will shed further light into the potential of making these drugs part of current standard practice.

Ixabepilone: Overview of Effectiveness, Safety, and Tolerability in Metastatic Breast Cancer.

Treatment algorithms for metastatic breast cancer describe sequential treatment with chemotherapy and, if appropriate, targeted therapy for as long as the patient receives benefit. The epothilone ixabepilone is a microtubule stabilizer approved as a monotherapy and in combination with capecitabine for the treatment of metastatic breast cancer in patients with demonstrated resistance to anthracyclines and taxanes. While chemotherapy and endocrine therapy form the backbone of treatment for metastatic breast cancer, the epothilone drug class has distinguished itself for efficacy and safety among patients with disease progression during treatment with chemotherapy. In phase III trials, ixabepilone has extended progression-free survival and increased overall response rates, with a manageable toxicity profile. Recent analyses of subpopulations within large pooled datasets have characterized the clinical benefit for progression-free survival and overall survival for ixabepilone in special populations, such as patients with triple-negative breast cancer or those who relapsed within 12 months of prior treatment. Additional investigation settings for ixabepilone therapy discussed here include adjuvant therapy, weekly dosing schedules, and ixabepilone in new combinations of treatment. As with other microtubule stabilizers, ixabepilone treatment can lead to peripheral neuropathy, but evidence-based management strategies may reverse these symptoms. Dose reductions did not appear to have an impact on the efficacy of ixabepilone plus capecitabine. Incorporation of ixabepilone into individualized treatment plans can extend progression-free survival in a patient population that continues to represent an unmet need.

A Phase II Study of the Efficacy and Safety of Chloroquine in Combination With Taxanes in the Treatment of Patients With Advanced or Metastatic Anthracycline-refractory Breast Cancer.

INTRODUCTION: Chemotherapy eliminates most of the cancer cells except those with potential for self-renewal and tumor initiation, called cancer stem cells (CSCs). Chloroquine, through bioinformatics, was found to be a potential agent to target CSCs. We designed a phase II trial to test the efficacy and safety of chloroquine in combination with taxane or taxane-like chemotherapy agents in patients with advanced or metastatic breast cancer who are refractory to anthracycline-based chemotherapy. PATIENTS AND METHODS: Female patients ≥ 18 years of age who had received prior anthracycline chemotherapy were enrolled in this study. Chloroquine 250 mg was given daily orally with either docetaxel or paclitaxel or nab-paclitaxel or ixabepilone every 3 weeks. The maximum number of 3-week cycles allowed was 6. The primary efficacy endpoint was the objective response rate (ORR). The secondary efficacy endpoints included progression-free survival (PFS) and safety analysis. RESULTS: Thirty-eight patients were enrolled in the study, and 31 patients were evaluated for response. The median age was 54.1 years (range, 31.7-78.1 years). The ORR was 45.16% (95% confidence interval [CI], 29.2%-62.2%), which was higher than the expected ORR of 30% (P = .03). Patients were followed for a median of 25.4 months and experienced a median PFS of 12.4 months (95% CI, 4.9-24.6 months) and a median OS of 25.4 months (95% CI, 13.7-83.5 months). The combination was well-tolerated, with only 13.15% of patients experiencing grade ≥ 3 adverse events. CONCLUSION: A combination of chloroquine with taxane or taxane-like chemotherapy was efficacious in patients with locally advanced or metastatic breast cancer with prior anthracycline-based chemotherapy.

A multi-scale systems pharmacology approach uncovers the anti-cancer molecular mechanism of Ixabepilone.

It has been realized that FDA approved drugs may have more molecular targets than is commonly thought. Thus, to find the exact drug-target interactions (DTIs) is of great significance for exploring the new molecular mechanism of drugs. Here, we developed a multi-scale system pharmacology (MSSP) method for the large-scale prediction of DTIs. We used MSSP to integrate drug-related and target-related data from multiple levels, the network structural data formed by known drug-target relationships for predicting likely unknown DTIs. Prediction results revealed that Ixabepilone, an epothilone B analog for treating breast cancer patients, may target Bcl-2, an oncogene that contributes to tumor progression and therapy resistance by inhibiting apoptosis. Furthermore, we demonstrated that Ixabepilone could bind with Bcl-2 and decrease its protein expression in breast cancer cells. The down-regulation of Bcl-2 by Ixabepilone is resulted from promoting its degradation by affecting p-Bcl-2. We further found that Ixabepilone could induce autophagy by releasing Beclin1 from Beclin1/Bcl-2 complex. Inhibition of autophagy by knockdown of Beclin1 or pharmacological inhibitor augmented apoptosis, thus enhancing the antitumor efficacy of Ixabepilone against breast cancer cells in vitro and in vivo. In addition, Ixabepilone also decreases Bcl-2 protein expression and induces cytoprotective autophagy in human hepatic carcinoma and glioma cells. In conclusion, this study not only provides a feasible and alternative way exploring new molecular mechanisms of drugs by combing computation DTI prediction, but also reveals an effective strategy to reinforce the antitumor efficacy of Ixabepilone.

Taxane and epothilone-induced peripheral neurotoxicity: From pathogenesis to treatment.

Taxane-induced peripheral neurotoxicity (TIPN) is the most common non-hematological side effect of taxane-based chemotherapy, and may result in dose reductions and discontinuations, having as such a detrimental effect on patients' overall survival. Epothilones share similar mechanism of action with taxanes. The typical TIPN clinical presentation is mainly comprised of numbness and paresthesia, in a stocking-and-glove distribution and may progress more proximally over time, with paclitaxel being more neurotoxic than docetaxel. Motor and autonomic involvement is less common, whereas an acute taxane-induced acute pain syndrome is frequent. Patient reported outcomes questionnaires, clinical evaluation, and instrumental tools offer complementary information in TIPN. Its electrodiagnostic features include reduced/abolished sensory action potentials, and less prominent motor involvement, in keeping with a length-dependent, axonal dying back predominately sensory neuropathy. TIPN is dose-dependent and may be reversible within months after the end of chemotherapy. The single and cumulative delivered dose of taxanes is considered the main risk factor of TIPN development. Apart from the cumulative dose, other risk factors for TIPN include demographic, clinical, and pharmacogenetic features with several single-nucleotide polymorphisms potentially linked with increased susceptibility of TIPN. There are currently no neuroprotective strategies to reduce the risk of TIPN, and symptomatic treatments are very limited. This review critically examines the pathogenesis, incidence, risk factors (both clinical and pharmacogenetic), clinical phenotype and management of TIPN.

Mitochondrial dysfunction in the pathogenesis of chemotherapy-induced peripheral neuropathy.

Several first-line chemotherapeutic agents, including taxanes, platinum agents and proteasome inhibitors, are associated with the dose-limiting side effect of chemotherapy-induced peripheral neuropathy (CIPN). CIPN predominantly manifests as sensory symptoms, which are likely due to drug accumulation within peripheral nervous tissues rather than the central nervous system. No treatment is currently available to prevent or reverse CIPN. The causal mechanisms underlying CIPN are not yet fully understood. Mitochondrial dysfunction has emerged as a major factor contributing to the development and maintenance of CIPN. This chapter will provide an overview of both clinical and preclinical data supporting this hypothesis. We will review the studies reporting the nature of mitochondrial dysfunction evoked by chemotherapy in terms of changes in mitochondrial morphology, bioenergetics and reactive oxygen species (ROS) generation. Furthermore, we will discuss the in vivo effects of pharmacological interventions that counteract chemotherapy-evoked mitochondrial dysfunction and ameliorate pain-like behavior.

Identification of high-risk drugs related to chemotherapy-induced peripheral neuropathy in Cancer Therapy Evaluation Program-sponsored phase I trials.

BACKGROUND: Chemotherapy-induced peripheral neuropathy (CIPN) is a significant and debilitating side effect. However, there have been no studies of the relative risk of CIPN with known causative agents. We examined the risk of CIPN in patients taking such agents as a part of the National Cancer Institute (NCI) Cancer Therapy Evaluation Program-sponsored phase I trials. METHODS: CIPN events in each patient were graded according to the Clinical Terminology of Common Adverse Effects and compared among several high-risk chemotherapeutic agent groups, adjusting for possible confounding factors. Patients receiving tubulin-targeted agents were analysed separately for specific background factors associated with CIPN. RESULTS: In 135 phase I clinical trials, 259 of 3614 patients were identified as developing CIPN during chemotherapy. Tubulin-targeting agents and proteasome inhibitors were identified as high-risk agents (hazard ratio 9.04 and 5.01, respectively) for CIPN, whereas platinum-complex agents and thalidomide analogues imparted lower risk (hazard ratio 1.52 and 1.11, respectively). Age, sex and medical history of diabetes were not significantly related to CIPN. CIPN developed over time as the number of chemotherapy cycles increased. Among patients with CIPN, treatment with tubulin-targeting agents resulted in a significantly higher rate of chemotherapy schedule modification compared with treatments with other chemotherapeutic agents. CONCLUSIONS: Tubulin-targeting agents and proteasome inhibitors were associated with a greatly increased risk of CIPN compared with other agents. CIPN tended to develop in later chemotherapy cycles. These findings will help to minimise the risk of CIPN by encouraging increased surveillance and earlier dose adjustment of high-risk agents in phase I trials.

UCBG 2-08: 5-year efficacy results from the UNICANCER-PACS08 randomised phase III trial of adjuvant treatment with FEC100 and then either docetaxel or ixabepilone in patients with early-stage, poor prognosis breast cancer.

PURPOSE: UNICANCER-PACS08 compared adjuvant FEC (5-FU; epirubicin; cyclophosphamide) then docetaxel to FEC then ixabepilone in poor prognosis early breast cancer (BC). We evaluated whether replacing docetaxel with ixabepilone would increase 5-year disease-free survival (DFS). PATIENTS AND METHODS: Triple-negative breast cancer (TNBC) or oestrogen receptor (ER)+/progesterone receptor (PR)-/HER2- BC patients were randomised to receive standard FEC (3 cycles) followed by 3 cycles of either docetaxel (100 mg/m2) or ixabepilone (40 mg/m2). Radiotherapy was mandatory after conservative surgery; ER+ patients received endocrine therapy. RESULTS: Seven hundred sixty-two patients were enrolled between October 2007 and September 2010. Baseline characteristics were balanced between arms. Median follow-up was 66.7 months. Median DFS was not reached; 5-year DFS rate was 76% with docetaxel and 79% with ixabepilone (hazard ratio [HR] = 0.80; 95% confidence interval [CI] = 0.58-1.10; p = 0.175). Median overall survival (OS) was not reached; 5-year OS rate was 86% versus 84% (HR = 0.97; 95% CI = 0.66-1.42; p = 0.897). TNBC patients treated with ixabepilone had a 23% lower risk of relapse compared to docetaxel (HR for DFS = 0.77; 95% CI = 0.53-1.11; p = 0.168). DFS was longer with ixabepilone than docetaxel in patients with grade II-III lymphocytic infiltration (HR = 0.55; 95% CI = 0.29-1.05; p = 0.063). All patients experienced ≥1 adverse events (AEs): 75% reported grade III-IV AEs and two (<1%) had grade V AEs (both with neutropenia and infection receiving ixabepilone). CONCLUSION: After adjuvant FEC, ixabepilone was comparable to docetaxel for treating poor prognosis early BC patients. The benefit of ixabepilone in subgroups (patients with TNBC and grade II-III lymphocytic infiltration) requires further evaluation.

Differential Morphological and Biochemical Recovery from Chemotherapy-Induced Peripheral Neuropathy Following Paclitaxel, Ixabepilone, or Eribulin Treatment in Mouse Sciatic Nerves.

The reversibility of chemotherapy-induced peripheral neuropathy (CIPN), a disabling and potentially permanent side effect of microtubule-targeting agents (MTAs), is becoming an increasingly important issue as treatment outcomes improve. The molecular mechanisms regulating the variability in time to onset, severity, and time to recovery from CIPN between the common MTAs paclitaxel and eribulin are unknown. Previously (Benbow et al. in Neurotox Res 29:299-313, 2016), we found that after 2 weeks of a maximum tolerated dose (MTD) in mice, paclitaxel treatment resulted in severe reductions in axon area density, higher frequency of myelin abnormalities, and increased numbers of Schwann cell nuclei in sciatic nerves. Biochemically, eribulin induced greater microtubule-stabilizing effects than paclitaxel. Here, we extended these comparative MTD studies to assess the recovery from these short-term effects of paclitaxel, eribulin, and a third MTA, ixabepilone, over the course of 6 months. Paclitaxel induced a persistent reduction in axon area density over the entire 6-month recovery period, unlike ixabepilone- or eribulin-treated animals. The abundance of myelin abnormalities rapidly declined after cessation of all drugs but recovered most slowly after paclitaxel treatment. Paclitaxel- and ixabepilone- but not eribulin-treated animals exhibited increased Schwann cell numbers during the recovery period. Tubulin composition and biochemistry rapidly returned from MTD-induced levels of α-tubulin, acetylated α-tubulin, and end-binding protein 1 to control levels following cessation of drug treatment. Taken together, sciatic nerve axons recovered more rapidly from morphological effects in eribulin- and ixabepilone-treated animals than in paclitaxel-treated animals and drug-induced increases in protein expression levels following paclitaxel and eribulin treatment were relatively transient.

A phase II study of frontline paclitaxel/carboplatin/bevacizumab, paclitaxel/carboplatin/temsirolimus, or ixabepilone/carboplatin/bevacizumab in advanced/recurrent endometrial cancer.

OBJECTIVE: Paclitaxel and carboplatin (PC) is a standard initial therapy for advanced endometrial cancer. We evaluated the efficacy and tolerability of incorporating three novel agents into initial therapy. METHODS: In this randomized phase II trial, patients with chemotherapy-naïve stage III/IVA (with measurable disease) and stage IVB or recurrent (with or without measurable disease) endometrial cancer were randomly assigned to treatment with PC plus bevacizumab (Arm 1), PC plus temsirolimus (Arm 2) or ixabepilone and carboplatin (IC) plus bevacizumab (Arm 3). The primary endpoint was progression-free survival (PFS). Comparable patients on the PC Arm of trial GOG209 were used as historical controls. Secondary endpoints were response rate, overall survival (OS), and safety. RESULTS: Overall, 349 patients were randomized. PFS duration was not significantly increased in any experimental arm compared with historical controls (p > 0.039). Treatment HRs (92% CI) for Arms 1, 2, and 3 relative to controls were 0.81 (0.63-1.02), 1.22 (0.96-1.55) and 0.87 (0.68-1.11), respectively. Response rates were similar across arms (60%, 55% and 53%, respectively). Relative to controls, OS duration (with censoring at 36 months), was significantly increased in Arm 1 (p < 0.039) but not in Arms 2 and 3; the HRs (92% CIs) were 0.71 (0.55-0.91), 0.99 (0.78-1.26), and 0.97 (0.77-1.23), respectively. No new safety signals were identified. Common mutations and rates of mismatch repair protein loss are described by histotype. Potential predictive biomarkers for temsirolimus and bevacizumab were identified. CONCLUSION: PFS was not significantly increased in any experimental arm compared to historical controls. NRG Oncology/Gynecologic Oncology Group Study GOG-86P.

Phase IB trial of ixabepilone and vorinostat in metastatic breast cancer.

PURPOSE: To translate promising preclinical data on the combination of vorinostat and ixabepilone for metastatic breast cancer (MBC) into clinical trials. METHODS: We conducted a randomized two-arm Phase IB clinical trial of ascending doses of vorinostat and ixabepilone in prior -treated MBC patients. To determine the maximum tolerated dose (MTD), 37 patients were randomized to schedule A: every-3-week ixabepilone + vorinostat (days 1-14), or schedule B: weekly ixabepilone + vorinostat (days 1-7; 15-21) Pharmacokinetics were assessed. Nineteen additional patients were randomized to schedule A or B and objective response rate (ORR), clinical benefit rate (CBR), toxicity, progression-free survival (PFS), and overall survival (OS) were assessed. RESULTS: The schedule A MTD was vorinostat 300 mg daily (days 1-14), ixabepilone 32 mg/m2 (day 2); 21-day cycle 27% dose-limiting toxicities (DLTs). The schedule B MTD was vorinostat 300 mg daily (days 1-7; 15-21), ixabepilone 16 mg/m2 (days 2, 9, 16); 28-day cycle; no DLTs. Vorinostat and ixabepilone clearances were 194 L/h and 21.3 L/h/m2, respectively. Grade 3 peripheral sensory neuropathy was reported in 8% (A) and 21% (B) of patients. The ORR and CBR were 22 and 22% (A); 30 and 35% (B). Median PFS was 3.9 (A) and 3.7 (B) months. OS was 14.8 (A) and 17.1 (B) months. CONCLUSIONS: We established the MTD of vorinostat and ixabepilone. This drug combination offers a novel therapy for previously treated MBC patients. The potential for lower toxicity and comparable efficacy compared to current therapies warrants further study.

Ixabepilone and Carboplatin for Hormone Receptor Positive/HER2-neu Negative and Triple Negative Metastatic Breast Cancer.

BACKGROUND: Hormonal therapies and single-agent sequential chemotherapeutic regimens are the standards of care for HER2- metastatic breast cancer (MBC). However, treating patients with hormone-refractory and triple negative (TN) MBC remains challenging. We report the results of combined ixabepilone and carboplatin in a single-arm phase II trial. PATIENTS AND METHODS: In the present prospective analysis of hormone receptor-positive (HR+)/HER2- and TN MBC cohorts, patients could have received 0 to 2 chemotherapy regimens for MBC before enrollment. All patients received ixabepilone 20 mg/m2 and carboplatin (area under the curve, 2.5) on days 1 and 8 every 21 days. The primary endpoint was the objective response rate (ORR). The secondary objectives included progression-free survival (PFS), clinical benefit rate (CBR), overall survival (OS), and toxicity. RESULTS: We enrolled 54 HR+ and 49 TN patients (median, 1 previous chemotherapy regimen for metastatic disease; most in addition to adjuvant chemotherapy). The ORR was 34% and 30.4% for the HR+ and TN patients, respectively, with a corresponding CBR of 56.6% and 41.3%. The ORRs were similar in taxane-pretreated patients (ORR, 31.4% and 28.6% for HR+ and TN patients, respectively). The median OS was 17.9 months for HR+ patients and 12.5 months for TN patients. The median PFS was similar for both groups at 7.6 months. Grade 3/4 nonhematologic toxicities included neuropathy (9%) and fatigue (8%). Nine patients developed grade 3/4 neuropathy, 7 of whom had received previous taxane treatment. CONCLUSION: Ixabepilone plus carboplatin is active even in later-line HR+ and TN disease. Toxicities were manageable without cumulative myelosuppression. This combination is a reasonable option for those patients with MBC who require combination chemotherapy.

Kinetic-Pharmacodynamic Model of Chemotherapy-Induced Peripheral Neuropathy in Patients with Metastatic Breast Cancer Treated with Paclitaxel, Nab-Paclitaxel, or Ixabepilone: CALGB 40502 (Alliance).

Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting toxicity caused by several chemotherapeutic agents. Currently, CIPN is managed by empirical dose modifications at the discretion of the treating physician. The goal of this research is to quantitate the dose-CIPN relationship to inform the optimal strategies for dose modification. Data were obtained from the Cancer and Leukemia Group B (CALGB) 40502 trial, a randomized phase III trial of paclitaxel vs. nab-paclitaxel vs. ixabepilone as first-line chemotherapy for locally recurrent or metastatic breast cancer. CIPN was measured using a subset of the Functional Assessment of Cancer Therapy-Gynecologic Oncology Group Neurotoxicity (FACT-GOG-NTX) scale. A kinetic-pharmacodynamic (K-PD) model was utilized to quantitate the dose-CIPN relationship simultaneously for the three drugs. Indirect response models with linear and Smax drug effects were evaluated. The model was evaluated by comparing the predicted proportion of patients with CIPN (score ≥8 or score ≥12) to the observed proportion. An indirect response model with linear drug effect was able to describe the longitudinal CIPN data reasonably well. The proportion of patients that were falsely predicted to have CIPN or were falsely predicted not to have CIPN was 20% or less at any cycle. The model will be utilized to identify an early time point that can predict CIPN at later time points. This strategy will be utilized to inform dose adjustments to prospectively manage CIPN. Clinicaltrials.gov ID: NCT00785291.

TITAN: phase III study of doxorubicin/cyclophosphamide followed by ixabepilone or paclitaxel in early-stage triple-negative breast cancer.

PURPOSE: Ixabepilone is a microtubule stabilizer with activity in taxane-refractory metastatic breast cancer and low susceptibility to taxane-resistance mechanisms including multidrug-resistant phenotypes and high ß-III tubulin expression. Since these resistance mechanisms are common in triple-negative breast cancer (TNBC), ixabepilone may have particular advantages in this patient population. This study evaluated the substitution of ixabepilone for paclitaxel following doxorubicin/cyclophosphamide (AC) in the adjuvant treatment of early-stage TNBC. METHODS: Patients with operable TNBC were eligible following definitive breast surgery. Patients were randomized (1:1) to receive four cycles of AC followed by either four cycles (12 weeks) of ixabepilone or 12 weekly doses of paclitaxel. RESULTS: 614 patients were randomized: 306 to AC/ixabepilone and 308 to AC/paclitaxel. At a median follow-up of 48 months, 59 patients had relapsed (AC/ixabepilone, 29; AC/paclitaxel, 30). The median time from diagnosis to relapse was 20.8 months. The 5-year disease-free survival (DFS) rates of the two groups were similar [HR 0.92; ixabepilone 87.1% (95% CI 82.6-90.5) vs. paclitaxel 84.7% (95% CI 79.7-88.6)]. The estimated 5-year overall survival (OS) rates were also similar [HR 1.1; ixabepilone 89.7% (95% CI 85.5-92.7) vs. paclitaxel 89.6% (95% CI 85.0-92.9)]. Peripheral neuropathy was the most common grade 3/4 event. Dose reductions and treatment discontinuations occurred more frequently during paclitaxel treatment. CONCLUSIONS: Treatment with AC/ixabepilone provided similar DFS and OS in patients with operable TNBC when compared to treatment with AC/paclitaxel. The two regimens had similar toxicity, although treatment discontinuation, dose modifications, and overall peripheral neuropathy were more frequent with AC/paclitaxel. TRIAL REGISTRATION: Clinical Trials.gov Identifier, NCT00789581.

Zampanolide, a Microtubule-Stabilizing Agent, Is Active in Resistant Cancer Cells and Inhibits Cell Migration.

Zampanolide, first discovered in a sponge extract in 1996 and later identified as a microtubule-stabilizing agent in 2009, is a covalent binding secondary metabolite with potent, low nanomolar activity in mammalian cells. Zampanolide was not susceptible to single amino acid mutations at the taxoid site of ß-tubulin in human ovarian cancer 1A9 cells, despite evidence that it selectively binds to the taxoid site. As expected, it did not synergize with other taxoid site microtubule-stabilizing agents (paclitaxel, ixabepilone, discodermolide), but surprisingly also did not synergize in 1A9 cells with laulimalide/peloruside binding site agents either. Efforts to generate a zampanolide-resistant cell line were unsuccessful. Using a standard wound scratch assay in cell culture, it was an effective inhibitor of migration of human umbilical vein endothelial cells (HUVEC) and fibroblast cells (D551). These properties of covalent binding, the ability to inhibit cell growth in paclitaxel and epothilone resistant cells, and the ability to inhibit cell migration suggest that it would be of interest to investigate zampanolide in preclinical animal models to determine if it is effective in vivo at preventing tumor growth and metastasis.