Efficacy and Safety of Ixabepilone (BMS-247550) in a Phase II Study of Patients With Advanced Breast Cancer Resistant to an Anthracycline, a Taxane, and Capecitabine

Efficacy and safety of utidelone for the treatment of patients with locally advanced or metastatic non-small-cell lung cancer who have failed standard second-line treatment: A phase 2 clinical trial (BG01-1801)

Background

Chemotherapy remains the standard-of-care for many patients with locally advanced or metastatic non-small-cell lung cancer (NSCLC), but acquired resistance presents challenges. The aim of this open-label, multicenter phase 2 clinical trial was to determine the efficacy and safety of utidelone, a novel genetically engineered epothilone analog and microtubule-stabilizing agent, as a third- or later-line treatment for locally advanced or metastatic NSCLC.

Methods

Patients who had failed standard second-line treatment (including platinum-containing chemotherapy or targeted therapy) received utidelone (40 mg/m2 via intravenous injection daily, day 1-5) every 21 days. The primary endpoint was the objective response rate (ORR). Secondary endpoints were the duration of response (DoR), progression-free survival (PFS), overall survival (OS), and safety.

Results

From March 12, 2019 to January 18, 2021, 26 pretreated patients with locally advanced or metastatic NSCLC (100% of patients had received prior platinum and 65.4% patients had received prior taxane treatment) were enrolled (80.8% of patients had adenocarcinoma). At baseline, nine (34.6%) patients had received second-line treatment, 10 (38.5%) patients had received third-line treatment, and seven (26.9%) patients had received fourth- or later-line treatment. By the data cut-off date of August 10, 2021, the median follow-up was 7.49 months (range, 1.4-26.7 months). The ORR was 15.4% (95% confidence interval [CI], 4.4%-34.9%) in the intention-to-treat (ITT) cohort (N = 26) and 19.0% (95% CI, 5.4%-41.9%) in the per-protocol (PP) cohort (N = 21). The disease control rate was 69.2% (95% CI, 48.2%-85.7%) and 81.0% (95% CI, 58.1%-94.6%) in the ITT and PP cohorts, respectively. The median DoR was 4.1 months (95% CI, 3.1-5.1 months) in the ITT cohort. The median PFS was 4.37 months (95% CI, 2.50-5.29 months) in the ITT cohort and 4.37 months (95% CI, 2.50-9.76 months) in the PP cohort. The median OS was not reached, and the 12-month OS rate was 69% (95% CI, 45.1%-84.1%). Grade 3/4 treatment-emergent adverse events occurred in 38.5% of patients, and the most common was peripheral neuropathy (23.1%, all Grade 3), which was manageable with dose modifications.

Conclusions

In this clinical trial, utidelone showed promising efficacy and had a manageable safety profile. Further clinical studies are warranted to confirm its role in NSCLC treatment.

Trial registration

No.NCT03693547; https://classic.clinicaltrials.gov.

Exploring the synthetic approaches and clinical prowess of established macrocyclic pharmaceuticals

Macrocyclic compounds, characterized by cyclic structures, often originate from either modified forms of unicyclic canonical molecules or natural products. Within the field of medicinal chemistry, there has been a growing fascination with drug-like macrocycles in recent years, primarily due to compelling evidence indicating that macrocyclization can significantly influence both the biological and physiochemical properties, as well as the selectivity, when compared to their acyclic counterparts. The approval of contemporary pharmaceutical agents like Lorlatinib underscore the notable clinical relevance of drug-like macrocycles. Nonetheless, the synthesis of these drug-like macrocycles poses substantial challenges, primarily stemming from the complexity of ring-closing reactions, which are inherently dependent on the size and geometry of the bridging linker, impacting overall yields. Nevertheless, macrocycles offer a promising avenue for expanding the synthetic toolkit in medicinal chemistry, enabling the creation of bioactive compounds. To shed light on the subject, we delve into the clinical prowess of established macrocyclic drugs, spanning various therapeutic areas, including oncology, and infectious diseases. Case studies of clinically approved macrocyclic agents illustrate their profound impact on patient care and disease management. As we embark on this journey through the world of macrocyclic pharmaceuticals, we aim to provide a comprehensive overview of their synthesis and clinical applications, shedding light on the pivotal role they play in modern medicine.

Diverse microtubule-targeted anticancer agents kill cells by inducing chromosome missegregation on multipolar spindles

Microtubule-targeted agents are commonly used for cancer treatment, though many patients do not benefit. Microtubule-targeted drugs were assumed to elicit anticancer activity via mitotic arrest because they cause cell death following mitotic arrest in cell culture. However, we recently demonstrated that intratumoral paclitaxel concentrations are insufficient to induce mitotic arrest and rather induce chromosomal instability (CIN) via multipolar mitotic spindles. Here, we show in metastatic breast cancer and relevant human cellular models that this mechanism is conserved among clinically useful microtubule poisons. While multipolar divisions typically produce inviable progeny, multipolar spindles can be focused into near-normal bipolar spindles at any stage of mitosis. Using a novel method to quantify the rate of CIN, we demonstrate that cell death positively correlates with net loss of DNA. Spindle focusing decreases CIN and causes resistance to diverse microtubule poisons, which can be counteracted by addition of a drug that increases CIN without affecting spindle polarity. These results demonstrate conserved mechanisms of action and resistance for diverse microtubule-targeted agents. Trial registration: clinicaltrials.gov, NCT03393741.

Targeting HER2-low in metastatic breast cancer: an evolving treatment paradigm

The results of the Phase III DESTINY-Breast04 trial of trastuzumab deruxtecan (T-DXd) are leading to a shift in both the classification and treatment of human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer. In this trial, T-DXd was associated with a substantial survival benefit among patients with hormone receptor-positive and hormone receptor-negative disease and low expression of HER2, a biomarker previously considered unactionable in this treatment setting. Herein, we discuss the evolving therapeutic pathway for HER2-low disease, ongoing clinical trials, and the potential challenges and evidence gaps arising with treatment of this patient population.

Selective protection of normal cells from chemotherapy, while killing drug-resistant cancer cells

Cancer therapy is limited by toxicity in normal cells and drug-resistance in cancer cells. Paradoxically, cancer resistance to certain therapies can be exploited for protection of normal cells, simultaneously enabling the selective killing of resistant cancer cells by using antagonistic drug combinations, which include cytotoxic and protective drugs. Depending on the mechanisms of drug-resistance in cancer cells, the protection of normal cells can be achieved with inhibitors of CDK4/6, caspases, Mdm2, mTOR, and mitogenic kinases. When normal cells are protected, the selectivity and potency of multi-drug combinations can be further enhanced by adding synergistic drugs, in theory, eliminating the deadliest cancer clones with minimal side effects. I also discuss how the recent success of Trilaciclib may foster similar approaches into clinical practice, how to mitigate systemic side effects of chemotherapy in patients with brain tumors and how to ensure that protective drugs would only protect normal cells (not cancer cells) in a particular patient.

Biomarkers and Treatment Strategies for Breast Cancer Recurrence

Despite recent treatment advancements, breast cancer remains a life-threatening disease. Although treatment is successful in the early stages, a significant proportion of individuals with breast cancer eventually experience a recurrence of the disease. Breast tumour recurrence poses a significant medical issue. Despite tumours being a primary cause of mortality, there remains a limited understanding of the fundamental mechanisms underlying tumour recurrence. The majority of the time, after surgery or medical treatment, this metastatic disease manifests itself after the disease is undiagnosed for a considerable amount of time. This phenomenon is commonly referred to as a relapse or recurrence. Metastatic breast cancer has the potential to recur at varying intervals, ranging from a few months to several decades following the initial diagnosis and treatment. This article aimed to summarise the primary causes of breast cancer recurrence and highlight the key issues that need to be addressed in order to effectively decrease the mortality rate among breast cancer patients. This article discusses various therapeutic approaches currently employed and emerging treatment strategies that hold the potential for the complete cure of cancer.

Randomized Phase II Study of Two Doses of Pixantrone in Patients with Metastatic Breast Cancer (NCCTG N1031, Alliance)

BACKGROUND

Anthracycline use in metastatic breast cancer (MBC) is hindered by cumulative exposure limits and risk of cardiotoxicity. Pixantrone, a novel aza-anthracenedione with structural similarities to mitoxantrone and anthracyclines, is theorized to exhibit less cardiotoxicity, mainly due to lack of iron binding. We conducted a randomized phase II study to evaluate the efficacy and safety of 2 dosing schedules of pixantrone in patients with refractory HER2-negative MBC.

METHODS

Intravenous pixantrone was administered at 180 mg/m2 every 3 weeks (group A) versus 85 mg/m2 on days 1, 8, and 15 of a 28-day cycle (group B). Primary endpoint was objective response rate (ORR) and secondary endpoints included progression-free survival (PFS), median 6-month PFS, overall survival (OS), safety, quality of life, and serial assessment of circulating tumor cells. A 20% ORR was targeted as sufficient for further testing of pixantrone in this patient population.

RESULTS

Forty-five patients were evaluable, with 2 confirmed partial responses in group A and 1 in group B. The trial was terminated due to insufficient activity. Overall median PFS and OS were 2.8 (95% confidence interval [CI]: 2.0-4.1) and 16.8 (95% CI: 8.9-21.6) months, respectively. Notable overall grade 3-4 adverse events were the following: neutrophil count decrease (62%), fatigue (16%), and decrease in ejection fraction (EF) (4%).

CONCLUSION

Pixantrone has insufficient activity in the second- and third-line MBC setting. It appears, however, to have limited cardiotoxicity. (ClinicalTrials.gov ID: NCT01086605).

The Place of Chemotherapy in The Evolving Treatment Landscape for Patients With HR-positive/HER2-negative MBC

Endocrine therapy (ET) for the treatment of patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR-positive/HER2-negative) metastatic breast cancer (MBC) has changed markedly over recent years with the emergence of new ETs and the use of molecularly targeted agents. Cytotoxic chemotherapy continues, however, to have an important role in these patients and it is important to maximize its efficacy while minimizing toxicity to optimize outcomes. This review examines current HR-positive/HER2-negative MBC clinical guidelines and addresses key questions around the use of chemotherapy in the face of emerging therapeutic options. Specifically, the indications for chemotherapy in patients with HR-positive/HER2-negative MBC and the choice of optimal chemotherapy are discussed.

Management of hormone receptor-positive, human epidermal growth factor 2-negative metastatic breast cancer

Estrogen receptor (ER) is the major driver of most metastatic breast cancers (mBCs). Endocrine therapy (ET) is the most effective treatment for ER + mBC, but its effectiveness is limited by high rates of de novo and acquired resistance. A growing understanding of the biological characteristics and complexity of the ER pathway and the mechanisms of ET resistance has led to the development of a new generation of targeted therapies. One such mechanism is the cell cycle signaling pathways, which lead to the development of cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) that have, in turn, transformed the management of such tumors. Another important mechanism is the alteration of the phosphatidylinositol 3'-kinase/AKT/mammalian target of rapamycin pathway. Drugs targeting each component of these pathways are currently used in clinical practice, and several more are in development. As a result, a myriad of new targeted therapies are consistently being added to the clinical oncologist armamentarium. Navigating the evolving and highly complex treatment landscape of HR + /HER2- mBC remains both an art and a challenge. In this review, we discuss the biological features of HR + /HER2- mBC and the different mechanisms of resistance to ET. We also discuss the management of mBC as the disease changes from endocrine-sensitive to endocrine-resistant.

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.

Peripheral Nervous System Involvement in Non-Primary Pediatric Cancer: From Neurotoxicity to Possible Etiologies

Peripheral neuropathy is a well described complication in children with cancer. Oncologists are generally well aware of the toxicity of the main agents, but fear the side effects of new drugs. As chemotherapeutic agents have been correlated with the activation of the immune system such as in Chemotherapy Induced Peripheral Neuropathy (CIPN), an abnormal response can lead to Autoimmune Peripheral Neuropathy (APN). Although less frequent but more severe, Radiation Induced Peripheral Neuropathy may be related to irreversible peripheral nervous system (PNS). Pediatric cancer patients also have a higher risk of entering a Pediatric Intensive Care Unit for complications related to therapy and disease. Injury to peripheral nerves is cumulative, and frequently, the additional stress of a malignancy and its therapy can unmask a subclinical neuropathy. Emerging risk factors for CIPN include treatment factors such as dose, duration and concurrent medication along with patient factors, namely age and inherited susceptibilities. The recent identification of individual genetic variations has advanced the understanding of physiopathological mechanisms and may direct future treatment approaches. More research is needed on pharmacological agents for the prevention or treatment of the condition as well as rehabilitation interventions, in order to allow for the simultaneous delivery of optimal cancer therapy and the mitigation of toxicity associated with pain and functional impairment. The aim of this paper is to review literature data regarding PNS complications in non-primary pediatric cancer.

Chemotherapy Options beyond the First Line in HER-Negative Metastatic Breast Cancer

Despite the recent advances in the biological understanding of breast cancer (BC), chemotherapy still represents a key component in the armamentarium for this disease. Different agents are available as mono-chemotherapy options in patients with locally advanced or metastatic BC (MBC) who progress after a first- and second-line treatment with anthracyclines and taxanes. However, no clear indication exists on what the best option is in some populations, such as heavily pretreated, elderly patients, triple-negative BC (TNBC), and those who do not respond to the first-line therapy. In this article, we summarize available literature evidence on different chemotherapy agents used beyond the first-line, in locally advanced or MBC patients, including rechallenge with anthracyclines and taxanes, antimetabolite and antimicrotubule agents, such as vinorelbine, capecitabine, eribulin, ixabepilone, and the newest developed agents, such as vinflunine, irinotecan, and etirinotecan.

Efficacy of utidelone plus capecitabine versus capecitabine for heavily pretreated, anthracycline- and taxane-refractory metastatic breast cancer: final analysis of overall survival in a phase III randomised controlled trial

BACKGROUND

Primary analysis of the phase III trial BG01-1323L demonstrated that utidelone plus capecitabine significantly improved progression-free survival (PFS) and overall response rate (ORR) versus capecitabine alone in heavily-pretreated patients with metastatic breast cancer (MBC). Here, we report the final overall survival (OS) analysis and updates of other endpoints.

PATIENTS AND METHODS

In total, 405 patients were randomised 2:1 to receive utidelone (30 mg/m² IV daily, days 1-5, over 90 min) plus capecitabine (1000 mg/m² orally b.i.d., days 1-14) or capecitabine alone (1250 mg/m² orally b.i.d., days 1-14) every 21 days. The secondary endpoint, OS, was estimated using the Kaplan-Meier product-limit approach at a two-sided alpha level of 0.05 after the prespecified 310 death events had been reached. Exploratory analyses of the primary endpoint, PFS, and the secondary endpoint, ORR, were also done. Safety was analysed in patients who had at least one dose of study drug.

RESULTS

At the final OS analysis, the median duration of follow-up was 19.6 months in the utidelone plus capecitabine group and 15.4 months in the capecitabine alone group. In the intention-to-treat population, 313 deaths had occurred at data cut-off, 203 of 270 patients in the combination group and 110 of 135 in the monotherapy group. Median OS in the combination group was 19.8 months compared with 16.0 months in the monotherapy group [hazard ratio (HR) = 0.75, 95% confidence intervals (CI) 0.59-0.94, P = 0.0142]. The updated analysis of PFS and ORR showed that the combination therapy remained superior to monotherapy. Safety results were similar to those previously reported with respect to incidence, severity and specificity. No late-emerging toxicities or new safety concerns occurred.

CONCLUSIONS

For heavily-pretreated, anthracycline- and taxane-resistant MBC patients, utidelone plus capecitabine significantly improved OS versus capecitabine alone. These results support the use of utidelone plus capecitabine as a novel therapeutic regimen for patients with MBC.

National comprehensive cancer network recommendations for drugs without US food and drug administration approval in metastatic breast cancer: A cross-sectional study

BACKGROUND

National Comprehensive Cancer Network (NCCN) guidelines can include recommendations for off-label use of anti-cancer drugs. Here, we evaluate NCCN recommendations not supported by US Food and Drug Administration (FDA) approval and explore associations with such recommendations.

METHODS

All NCCN recommendations for MBC and their supporting data were identified. Drug labels were reviewed to determine whether recommendations are FDA approved. Logistic regression was used to compare FDA approved and off-label recommendations for pre-specified categories, including drug type, tumor subtype, level of recommendation and line of therapy.

RESULTS

Of 124 recommendations identified, 68 (55%) were off-label. Chemotherapy and human epidermal growth factor receptor 2 (HER2) targeted drugs were associated with lower odds of FDA approval (OR = 0.28, p = 0.001 and OR = 0.29, 95% p = 0.005, respectively). Recommendations for endocrine therapy (OR = 3.44, p = 0.009) and non-HER2 targeted treatment (OR = 10.0, p < 0.001) were more commonly FDA approved indications. Compared to combination therapies, monotherapies were more likely to be FDA approved (OR = 3.45, p = 0.001) as were category 1 (OR = 7.63, p = 0.001) and preferred NCCN recommendations (OR = 4.07, p < 0.001). Compared to off-label recommendations, NCCN recommendations of approved drugs were based on significantly higher sample size (mean 477 vs. 342 patients, p = 0.02) and were non-significantly associated with availability of randomized data (OR = 2.0, 95% CI 0.89-4.49, p = 0.09).

CONCLUSION

More than half of all NCCN recommendations for MBC are off-label, mostly involving chemotherapy containing regimes for HER2 negative disease and combinations which include HER2-targeted drugs. Improved transparency of NCCN guidelines may result from reporting of the strength of the evidence supporting recommendations for MBC.

Management of ER positive metastatic breast cancer

There are over 2 million cases a year of breast cancer, leading to over 600,000 deaths globally [1]. Despite these large numbers, increasingly more women are being cured with early stage disease and women with advanced disease are living longer [2]. The appreciation for molecular subtypes of the disease has led to significant therapeutic advances and estrogen receptor positive (ER+) breast cancer represents the largest of these subgroups. An appreciation for the importance of estrogen signaling in ER+ dates back to 1896 when Dr. George Thomas Beatson observed impressive disease responses after performing bilateral oophorectomy in 3 women at Glasgow Cancer Hospital [3]. The evolution of treatment for advanced disease from progestins, to the selective estrogen receptor modulator tamoxifen, and subsequently the aromatase inhibitors and the selective estrogen receptor degrader fulvestrant, has been accompanied by improved efficacy and decreased side effects. While the use of these drugs has changed the natural history of both early and advanced disease, it has been long recognized that many patients will develop resistance to this approach. After many years of trying to improve on single-agent endocrine treatment, since 2012 there has been an explosion of new drugs that have shown improved efficacy in combination with endocrine approaches. The first of these to receive FDA approval was the mTOR inhibitor everolimus (2012) [4], followed by the approval of 3 cyclin-dependent kinase 4 and 6 (CDK 4/6) inhibitors [palbociclib (2015) [5], ribociclib (2018) [6], and abemaciclib (2018) [7]], and more recently the PI3-kinase inhibitor alpelisib (2019) [8]. In addition, chemotherapy is still used frequently when endocrine manipulations have been exhausted. Like other incurable malignancies, the goal in advanced ER+ breast cancer is to prolong survival and maintain quality of life. Currently, we have more tools available to achieve this than ever before and we will review the efficacy and side effect data with these agents that are driving physician choices for individual patients.

The evolving management of metastatic triple negative breast cancer

Advanced triple negative breast cancer (TNBC) is an incurable disease classified by its lack of expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2. Due to its lack of therapeutic targets, it has historically been treated with single agent chemotherapy, with combination cytotoxic therapy typically reserved for patients with high disease burdens, symptomatic disease, and/or impending visceral crisis. Recent molecular analyses have revealed that this clinical group of TNBCs is in fact quite biologically heterogeneous, with multiple TNBC subtypes defined by distinct biology and clinical behavior. Building on this biology, 2 targeted strategies are now approved for selected patients with advanced TNBC: the poly (ADP-ribose) polymerase inhibitors for advanced TNBC with a germline mutation in BRCA1/2, and the combination of the programmed death ligand 1-specific antibody atezolizumab with nab-paclitaxel for advanced TNBC that expresses programmed death ligand 1 on immune cells within the tumor. These targeted agents tend to be associated with a more favorable side effect profile and longer disease control than standard chemotherapy. A number of other targeted therapies have shown promise in early clinical trials, and several are now in definitive phase 3 testing for advanced TNBC. These include the antiapoptotic kinase inhibitors ipatisertib and capivasertib, and the antibody-drug conjugate sacituzumab govitecan-hziy. Approved biomarker-driven treatment options for this disease are thus likely to expand in the near-term. Here we review current treatment options and emerging targeted therapies for advanced TNBC. For patients who do not meet criteria for approved targeted therapies, participation in clinical trials evaluating precision medicines with candidate predictive biomarkers in advanced TNBC should be encouraged.

The role of chemotherapy in treatment of advanced breast cancer: an overview for clinical practice

This review aims to evaluate the role of chemotherapy-containing regimens in the treatment of advanced breast cancer (ABC), with the purpose to optimize selection, sequencing and duration of treatment with the currently available agents for clinical practice. Data from observational as well as randomized phase II and III studies were included. Chemotherapy yielded a median overall survival (OS) of 2 years in registration studies, with comparable efficacy of different agents. Combining chemotherapy agents did not yield OS improvement and caused greater toxicity compared with single-agent chemotherapy. Continuing chemotherapy till progression or unacceptable toxicity generated greater efficacy without detrimental impact on quality of life compared with a limited amount of cycles. In real-world studies, benefits after third-line chemotherapy were modest compared with first- and second-line. Furthermore, effects of previous chemotherapy predicted effects of next-line therapy in real-world. Physicians increasingly prescribed capecitabine or taxanes as first- or second-line chemotherapy over time.

Breast Cancer, Version 3.2020, NCCN Clinical Practice Guidelines in Oncology

Several new systemic therapy options have become available for patients with metastatic breast cancer, which have led to improvements in survival. In addition to patient and clinical factors, the treatment selection primarily depends on the tumor biology (hormone-receptor status and HER2-status). The NCCN Guidelines specific to the workup and treatment of patients with recurrent/stage IV breast cancer are discussed in this article.

Antitumor Activity and Safety of Trastuzumab Deruxtecan in Patients With HER2-Low-Expressing Advanced Breast Cancer: Results From a Phase Ib Study

PURPOSE

Trastuzumab deruxtecan (T-DXd, formerly DS-8201a) is a novel human epidermal growth factor receptor 2 (HER2)-targeted antibody drug conjugate (ADC) with a topoisomerase I inhibitor payload. A dose escalation and expansion phase I study evaluated the safety and activity of T-DXd in patients with advanced HER2-expressing/mutated solid tumors. Here, results for T-DXd at the recommended doses for expansion (RDE) in patients with HER2-low (immunohistochemistry [IHC] 1+ or IHC 2+/in situ hybridization-) breast cancer (ClinicalTrials.gov identifier: NCT02564900) are reported.

PATIENTS AND METHODS

Eligible patients had advanced/metastatic HER2-low-expressing breast cancer refractory to standard therapies. The RDE of 5.4 or 6.4 mg/kg T-DXd were administered intravenously once every 3 weeks until withdrawal of consent, unacceptable toxicity, or progressive disease. Antitumor activity and safety were assessed.

RESULTS

Between August 2016 and August 2018, 54 patients were enrolled and received ≥ 1 dose of T-DXd at the RDE. Patients were extensively pretreated (median, 7.5 prior therapies). The confirmed objective response rate by independent central review was 20/54 (37.0%; 95% CI, 24.3% to 51.3%) with median duration of response of 10.4 months (95% CI, 8.8 month to not evaluable). Most patients (53/54; 98.1%) experienced ≥ 1 treatment-emergent adverse event (TEAE; grade ≥ 3; 34/54; 63.0%). Common (≥ 5%) grade ≥ 3 TEAEs included decreases in neutrophil, platelet, and WBC counts; anemia; hypokalemia; AST increase; decreased appetite; and diarrhea. Three patients treated at 6.4 mg/kg suffered fatal events associated with T-DXd-induced interstitial lung disease (ILD)/pneumonitis as determined by an independent adjudication committee.

CONCLUSION

The novel HER2-targeted ADC, T-DXd, demonstrated promising preliminary antitumor activity in patients with HER2-low breast cancer. Most toxicities were GI or hematologic in nature. ILD is an important identified risk and should be monitored closely and proactively managed.

Efficacy and Safety of Targeting Androgen Receptor in Advanced Breast Cancer: A Systematic Review

Background::

Androgen receptor (AR) upstreams complex signaling pathways that regulate cell proliferation and contribute to breast tumorignensis. Several clinical trials were initiated to investigate the clinical relevance of targeting AR especially in hormone-receptor-negative breast cancer.

Methods::

The search was performed in PubMed and the meeting libraries of ASCO, ESMO, SABCS, ImpakT congresses from January 2005 to July 2017. The following key words were used: Breast cancer, Androgen receptor, androgen agonist/antagonist, Flutamide, Abiraterone, Bicalutamide, Enzalutamide, Enobosarm, selective androgen receptor modulator.

Results::

Screening of title/abstracts yielded a total of 20 relevant results. Of those, twelve studies were found eligible: eleven clinical trials along with one case report. Response rates ranged from 0 to 12% while clinical benefit rates reached up to 35% in 2 studies (with enzalutamide and enobosarm). Progression-free survival ranged from 2.8 to 4.5 months. The most widely used cutoff for AR expression was 10%. High expression of AR was associated with more clinical benefit. Regarding safety, anti-androgens were generally well tolerated with hot flushes, elevated transaminases and fatigue being the most commonly reported across all agents.

Conclusion::

Androgen receptor pathway targeting in advanced breast cancer remains a valid option with reasonable clinical benefit in non-selected patients. Future studies are needed to define an AR addicted cohort with better responses and outcome.

Eribulin rapidly inhibits TGF-β-induced Snail expression and can induce Slug expression in a Smad4-dependent manner

Background

Evidence shows that the anticancer effects of microtubule targeting agents are not due solely to their antimitotic activities but also their ability to impair microtubule-dependent oncogenic signalling.

Methods

The effects of microtubule targeting agents on regulators of TGF-β-induced epithelial-to-mesenchymal transition (EMT) were evaluated in breast cancer cell lines using high content imaging, gene and protein expression, siRNA-mediated knockdown and chromatin immunoprecipitation.

Results

Microtubule targeting agents rapidly and differentially alter the expression of Snail and Slug, key EMT-promoting transcription factors in breast cancer. Eribulin, vinorelbine and in some cases, ixabepalone, but not paclitaxel, inhibited TGF-β-mediated Snail expression by impairing the microtubule-dependent nuclear localisation of Smad2/3. In contrast, eribulin and vinorelbine promoted a TGF-β-independent increase in Slug in cells with low Smad4. Mechanistically, microtubule depolymerisation induces c-Jun, which consequently increases Slug expression in cells with low Smad4.

Conclusion

These results identify a mechanism by which eribulin-mediated microtubule disruption could reverse EMT in preclinical models and in patients. Furthermore, high Smad4 levels could serve as a biomarker of this response. This study highlights that microtubule targeting drugs can exert distinct effects on the expression of EMT-regulating transcription factors and that identifying differences among these drugs could lead to their more rational use.

The safety of eribulin for the treatment of metastatic breast cancer

Introduction: Eribulin mesylate is a highly potent anticancer agent approved for use in pretreated metastatic breast cancer (MBC). Clinical trials of eribulin in MBC have demonstrated activity against this tumor type, and a phase 3 study in patients with MBC previously treated with an anthracycline and a taxane showed a significant increase in overall survival (OS) with eribulin versus control regimens. Areas covered: This review presents overviews of the development of eribulin, its pharmacology, and its efficacy in MBC. A detailed review of its safety profile is presented, and the safety of eribulin is compared with other agents commonly used to treat MBC. Expert opinion: As eribulin is the only drug shown to improve OS in patients with pretreated MBC, it is an important treatment option for many patients. Eribulin is currently considered a second-line (Europe) or third-line (United States) therapy, and studies have been examining use in the first-line setting. The use of eribulin in combination with other therapies is beginning to be explored because its manageable safety profile makes it an ideal combination-treatment partner. Emerging eribulin combination-treatment data suggest a manageable toxicity profile, and eribulin is set to be a key drug for the treatment of MBC in the future.

Microtubule-Targeting Drugs: More than Antimitotics

Nature has yielded numerous compounds that bind to tubulin/microtubules and disrupt microtubule function. Even with the advent of targeted therapies for cancer, natural products and their derivatives that target microtubules are some of the most effective drugs used in the treatment of solid tumors and hematological malignancies. For decades, these drugs were thought to work solely through their ability to inhibit mitosis. Accumulating evidence demonstrates that their actions are much more complex, in that they also have significant effects on microtubules in nondividing cells that inhibit a diverse range of signaling events important for carcinogenesis. The abilities of these drugs to inhibit oncogenic signaling likely underlies their efficacy, especially in solid tumors. In this review, we describe the role of microtubules in cells, the proliferation paradox of cells in culture as compared to cancers in patients, and evidence that microtubule-targeting drugs inhibit cellular signaling pathways important for tumorigenesis. The potential mechanisms behind differences in the clinical indications and efficacy of these natural-product-derived drugs are also discussed. Microtubules are an important target for structurally diverse natural products, and a fuller understanding of the mechanisms of action of these drugs will promote their optimal use.

Profile of abemaciclib and its potential in the treatment of breast cancer

Hormone-receptor-positive breast cancer is the most common subtype of breast cancer among patients with both early-stage and metastatic disease. Recent advances in the understanding of its pathophysiology have led to the discovery and utilization of targeted inhibitors to cyclin-dependent kinases 4 and 6 (CDK4/6). There are currently three available CDK4/6 inhibitors available for use in USA: palbociclib, ribociclib, and abemaciclib. Their oral administration and tolerable toxicities make this class of agents appealing to both patients and health care providers. Abemaciclib, the most recently approved CDK4/6 inhibitor, has unique pharmacologic properties and potential toxicities. This review highlights the current understanding of abemaciclib and discusses its current and future roles in the treatment of breast cancer.

Outcome of eribulin as a late treatment line for Thai metastatic breast cancer patients

Background

We report the safety and efficacy of eribulin as a late treatment line in Thai metastatic breast cancer (MBC) patients.

Patients and methods

A total of 30 MBC patients treated with eribulin between January 2014 and January 2017 were retrospectively analyzed. The patients were scheduled to receive 1.4 mg/m² of eribulin on day 1, day 8 and subsequently every 21 days. All patients had previously received at least three chemotherapy regimens including anthracycline and taxane. Response rate and progression-free survival (PFS) were analyzed.

Results

The median age was 56 years (range, 40–74 years), with a median follow-up time of 5.7 months (range, 0.2–25 months). The overall response rate was 30% (nine patients): four patients had triple-negative breast cancer, three patients had luminal B breast cancer and two patients had luminal A breast cancer. The median PFS was 2.9 months (range, 0.2–14 months). The median number of previous chemotherapy regimens was 4 (range, 3–9). Univariate analysis showed that the number of regimens (four or fewer) prior to eribulin was statistically associated with superior PFS (P = 0.009). Multivariate analysis also showed similar statistical association between number of prior regimens (four or fewer) and better PFS adjusted by age group (≥50 years; hazard ratio = 1.29; 95% CI: 1.0–1.65; P = 0.046). There were no toxic deaths or grade 4 toxicities. Nine (30%) patients had grade 3 anemia toxicities, and the other common toxicities were leukopenia and neutropenia. Four (13%) patients required dose reduction and 16 (53%) patients required dose delay because of toxicities.

Conclusion

Eribulin is an effective drug for heavily pretreated MBC patients with tolerable toxicities. The benefit was superior in patients who received fewer than four previous chemotherapy regimens.

Abemaciclib: The Newest CDK4/6 Inhibitor for the Treatment of Breast Cancer

OBJECTIVE

To review the pharmacology, efficacy, and safety of the cyclin-dependent kinase (CDK) inhibitor, abemaciclib, in the treatment of advanced or metastatic breast cancer (MBC).

DATA SOURCES

Relevant information was identified through a MEDLINE/PubMed (January 2000 to June 2018) literature search. The new drug application, prescribing information, and abstracts and posters from scientific meetings were also reviewed.

STUDY SELECTION/DATA EXTRACTION

The literature search was limited to human studies published in the English language. Phase 1, 2, and 3 studies evaluating the pharmacology, efficacy, or safety of abemaciclib for breast cancer were included.

DATA SYNTHESIS

Abemaciclib is an oral, potent, small molecule inhibitor of CDK4 and CDK6 activity, which blocks retinoblastoma tumor suppressor protein phosphorylation and thereby prevents progression through the cell cycle. Three major clinical trials, MONARCH 1, 2, and 3, established the efficacy and safety of abemaciclib for the treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or MBC. In these trials, response rates were promising, ranging from 19.7% to 59%, and median progression-free survival was significantly prolonged over the control arm in 2 of the trials. Common adverse effects included diarrhea, neutropenia, nausea, abdominal pain, infections, and fatigue. Relevance to Patient Care and Clinical Practice: Although no head-to-head studies have been completed between the CDK4/6 inhibitors, abemaciclib may be an attractive option because of its continuous dosing and ability to be used as monotherapy.

CONCLUSIONS

Abemaciclib is an effective and well-tolerated treatment for HR-positive, HER2-negative advanced or metastatic breast cancer.

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.

Analysis of the activity and safety of weekly low-dose bevacizumab-based regimens in heavily pretreated patients with metastatic breast cancer

Background

Currently, there are no standard regimens for metastatic breast cancer patients (MBC) who have failed ≥ 3 chemotherapy treatments. The aim of this study was to assess whether weekly low‐dose bevacizumab‐based regimens were well tolerated and would improve efficacy in MBC patients who had failed numerous therapies.

Methods

Seventeen patients with MBC who were heavily pretreated with a median of five regimens of therapy (range 1–10) between 2012 and 2016 were included in the analysis. Bevacizumab was administered at a dose of 100 mg intravenously once a week combined with one or two types of chemotherapeutic drugs until confirmed disease progression or an intolerable adverse event was observed. Patient characteristics, objective response rate, clinical benefit rate, progression‐free survival, and toxicity were assessed.

Results

All 17 patients had been pretreated with taxane‐based and anthracycline‐based chemotherapy. Weekly low‐dose bevacizumab combined with one or two types of chemotherapeutic drugs, which had usually not been previously used (e.g. etoposide, irinotecan, pemetrexed, methotrexate, and nab‐paclitaxel), was administered. Three patients achieved a partial response, while one had stable disease for > 24 weeks, and the clinical benefit rate was 23.5%. Median progression‐free survival was 3.4 months (95% confidence interval 2.0–4.8). The most common hematological adverse events were neutropenia, anemia, and thrombocytopenia. Bevacizumab‐related adverse events included grade 1 bleeding (17.6%) and grade 2 hypertension (5.9%).

Conclusions

Weekly low‐dose bevacizumab combined with chemotherapy shows a relatively favorable clinical response and tolerable toxicity, providing a feasible option for heavily pretreated MBC patients.

MONARCH 1, A Phase II Study of Abemaciclib, a CDK4 and CDK6 Inhibitor, as a Single Agent, in Patients with Refractory HR+/HER2- Metastatic Breast Cancer

Purpose: The phase II MONARCH 1 study was designed to evaluate the single-agent activity and adverse event (AE) profile of abemaciclib, a selective inhibitor of CDK4 and CDK6, in women with refractory hormone receptor-positive (HR⁺), HER2^- metastatic breast cancer (MBC).Experimental Design: MONARCH 1 was a phase II single-arm open-label study. Women with HR⁺/HER2^- MBC who had progressed on or after prior endocrine therapy and had 1 or 2 chemotherapy regimens in the metastatic setting were eligible. Abemaciclib 200 mg was administered orally on a continuous schedule every 12 hours until disease progression or unacceptable toxicity. The primary objective of MONARCH 1 was investigator-assessed objective response rate (ORR). Other endpoints included clinical benefit rate, progression-free survival (PFS), and overall survival (OS).Results: Patients (n = 132) had a median of 3 (range, 1-8) lines of prior systemic therapy in the metastatic setting, 90.2% had visceral disease, and 50.8% had ≥3 metastatic sites. At the 12-month final analysis, the primary objective of confirmed objective response rate was 19.7% (95% CI, 13.3-27.5; 15% not excluded); clinical benefit rate (CR+PR+SD≥6 months) was 42.4%, median progression-free survival was 6.0 months, and median overall survival was 17.7 months. The most common treatment-emergent AEs of any grade were diarrhea, fatigue, and nausea; discontinuations due to AEs were infrequent (7.6%).Conclusions: In this poor-prognosis, heavily pretreated population with refractory HR⁺/HER2^- metastatic breast cancer, continuous dosing of single-agent abemaciciclib was well tolerated and exhibited promising clinical activity. Clin Cancer Res; 23(17); 5218-24. ©2017 AACR.

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 β-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.

Efficacy and safety of eribulin in taxane-refractory patients in the ‘real world’

Aim: Recent clinical, randomized and observational studies showed that eribulin, an analogous of Halichondrin B, was beneficial and well-tolerated in heavily pretreated metastatic breast cancer patients. Here, we aim to evaluate the effectiveness and safety of eribulin in taxane-refractory metastatic breast cancer patients. Patients & methods: In this subanalysis of the ESEMPIO study database, we selected 91 subjects with well-defined taxane refractoriness and complete data available. Results: 41 patients (45.2%) showed clinical benefit; one complete response (2.2%) and 16 partial responses (17.6%) were observed. Median progression-free survival and median overall survival were 3.1 and 11.6 months, respectively. The most experienced adverse event was asthenia/fatigue (58%), followed by neutropenia (30%). The treatment-related toxicity led to eribulin-dose reduction in 19 patients and suspension in nine. Conclusion: This study shows that eribulin is effective and well tolerated also in taxane-refractory patients in clinical practice.

Recent Advances in the Development of Antineoplastic Agents Derived from Natural Products

Through years of evolutionary selection pressures, organisms have developed potent toxins that coincidentally have marked antineoplastic activity. These natural products have been vital for the development of multiagent treatment regimens currently employed in cancer chemotherapy, and are used in the treatment of a variety of malignancies. Therefore, this review catalogs recent advances in natural product-based drug discovery via the examination of mechanisms of action and available clinical data to highlight the utility of these novel compounds in the burgeoning age of precision medicine. The review also highlights the recent development of antibody-drug conjugates and other immunotoxins, which are capable of delivering highly cytotoxic agents previously deemed too toxic to elicit therapeutic benefit preferentially to neoplastic cells. Finally, the review examines natural products not currently used in the clinic that have novel mechanisms of action, and may serve to supplement current chemotherapeutic protocols.

Phase II trial of utidelone as monotherapy or in combination with capecitabine in heavily pretreated metastatic breast cancer patients

Background

The treatment of metastatic breast cancer (MBC) remains a great clinical challenge as drug resistance frequently develops. Alternative agents that can overcome drug resistance would offer new therapeutic options. The primary aim of this phase II study was to evaluate the efficacy and safety of utidelone as a monotherapy or in combination with capecitabine in metastatic breast cancer patients previously treated with and resistant to anthracyclines and taxanes.

Methods

In two open-label, noncomparative clinical studies, patients with metastatic breast cancer who previously received anthracycline- and/or taxane-containing regimens were given (1) 25 to 35 mg/m²/day intravenously infused utidelone, once daily for 5 days, in combination with 14 days of 2000 mg/m² capecitabine, divided in two equal daily oral doses or (2) 40 mg/m²/day intravenously infused utidelone, once daily for 5 days. These regimens were administered per each 21-day treatment cycle, and the maximum of treatment cycles allowed per protocol is 6. Objective response rate (ORR), progression-free survival (PFS), and tolerability were evaluated.

Results

In the combination study, 33 patients completed a median of 6 cycles of therapy, which was the highest cycles a trial patient could receive under the criteria of the study protocol. Efficacy was evaluated (n = 32) with an ORR of 42.4 % (FAS, 95 % CI, 26.6, 60.9) and a median PFS of 7.9 (FAS, 95 % CI, 6.1, 9.8) months. The monotherapy study (n = 63) resulted in an ORR of 28.57 % (FAS, 95 % CI, 18.4, 40.6) and a median PFS of 5.4 (FAS, 95 % CI, 2.9, 9.8) months. In both studies, common toxicities associated with utidelone administration included peripheral neuropathy, fatigue, myalgia, and arthralgia, but the toxicities were limited and manageable. Notably, very mild myelosuppression, low liver and renal toxicities, and very limited gastrointestinal toxic effect were observed, in contrast to other agents in the same class.

Conclusions

Utidelone showed promising efficacy, tolerability, and advantageous safety profiles in the treatment of patients with advanced anthracycline/taxane-refractory metastatic breast cancer and may offer new treatment options to overcome drug resistance.

Trial registration

CHiCTR-TRC-13004205, registered on August 15, 2013.

GEMOX: An Active Regimen for the Treatment of Luminal and Human Epidermal Growth Factor Receptor 2-Positive Metastatic Breast Cancer

BACKGROUND

Pretreated metastatic breast cancer (MBC) remains a formidable challenge with unmet needs both in terms of prolonged survival and quality-of-life-related issues.

METHODS

We collected data from 27 MBC patients treated with gemcitabine and oxaliplatin (GEMOX) at our institution between June 2009 and April 2015. The patients were heavily pretreated, and all had previously been exposed to anthracyclines and taxanes.

RESULTS

We achieved a complete response in 1 patient (4%), a partial response in 7 patients (26%) and stable disease in 12 patients (44%), while 6 patients (22%) experienced progressive disease. The response of 1 patient (4%) could not be evaluated because she interrupted her treatment during the first cycle due to a major reaction to oxaliplatin. We observed grade 4 hypertransaminasaemia in only 1 patient (4%) and grade 2 neuropathy in 16 patients (59%). Grade 3 leuconeutropenia was observed in 5 patients (18%). The median progression-free survival was 5.9 months and the median overall survival was 9.6 months.

CONCLUSIONS

GEMOX is an efficient and well-tolerated salvage regimen for MBC patients.

Neoadjuvant Sequential Docetaxel Followed by High-Dose Epirubicin in Combination With Cyclophosphamide Administered Concurrently With Trastuzumab. The DECT Trial

To report the results of the DECT trial, a phase II study of locally advanced or operable HER2-positive breast cancer (BC) treated with taxanes and concurrent anthracyclines and trastuzumab. Eligible patients (stage IIA-IIIB HER2-positive BC, 18-75 years, normal organ functions, ECOG ≤1, and left ventricular ejection fraction (LVEF) ≥55%) received four cycles of neoadjuvant docetaxel, 100 mg/m(2) intravenously, plus trastuzumab 6 mg/kg (loading dose 8 mg/kg) every 3 weeks, followed by four 3-weekly cycles of epirubicin 120 mg/m(2) and cyclophosphamide, 600 mg/m(2) , plus trastuzumab. Primary objective was pathologic complete response (pCR) rate, defined as ypT0/is ypN0 at definitive surgery. We enrolled 45 consecutive patients. All but six patients (13.3%) completed chemotherapy and all underwent surgery. pCR was observed in 28 patients (62.2%) overall and in 6 (66.7%) from the inflammatory subgroup. The classification and regression tree analysis showed a 100% pCR rate in patients with BMI ≥25 and with hormone negative disease. The median follow up was 46 months (8-78). Four-year recurrence-free survival was 74.7% (95%CI, 58.2-91.2). Seven patients (15.6%) recurred and one died. Treatment was well tolerated, with limiting toxicity being neutropenia. No clinical cardiotoxicity was observed. Six patients (13.4%) showed a transient LVEF decrease (<10%). In one patient we observed a ≥10% asymptomatic LVEF decrease persisting after surgery. Notwithstanding their limited applicability due to the current guidelines, our findings support the efficacy of the regimen of interest in the neoadjuvant setting along with a fairly acceptable toxicity profile, including cardiotoxicity. Results on BMI may invite further assessment in future studies. J. Cell. Physiol. 231: 2541-2547, 2016. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.

A Review of Systemic Treatment in Metastatic Triple-Negative Breast Cancer

Patients with breast cancer along with metastatic estrogen and progesterone receptor (ER/PR)- and human epidermal growth factor receptor 2 (HER2)-negative tumors are referred to as having metastatic triple-negative breast cancer (mTNBC) disease. Although there have been many new treatment options approved by the Food and Drug Administration for ER/PR-positive and Her2/neu-amplified metastatic breast cancer, relatively few new agents have been approved for patients with mTNBC. There have been several head-to-head chemotherapy trials performed within the metastatic setting, and much of what is applied in clinical practice is extrapolated from chemotherapy trials in the adjuvant setting, with taxanes and anthracyclines incorporated early on in the patient's treatment course. Select synergistic combinations can produce faster and more significant response rates compared with monotherapy and are typically used in the setting of visceral threat or symptomatic disease. Preclinical studies have implicated other possible targets and mechanisms in mTNBC. Ongoing clinical trials are underway assessing new chemotherapeutic strategies and agents, including targeted therapy and immunotherapy. In this review, we evaluate the standard systemic and future treatment options in mTNBC.

Chemotherapy options for patients suffering from heavily pretreated metastatic breast cancer

The identification of additional chemotherapy agents for anthracycline- and taxane-pretreated advanced breast cancer (ABC) is an urgent medical need. Single agent chemotherapy is most times administered because combined therapy is only associated with modest, if any, improvement in median progression-free survival. Randomized trials failed to show overall survival benefit compared with single agent chemotherapy. We hope to modify the natural history of ABC by the consecutive use of treatments with documented activity in heavily pretreated patients. Quality of life remains an important end point as cure is in general not possible. We first review the activity of the approved and the most frequently used agents in heavily pretreated ABC. Thereafter, the potential role and safety profile of etirinotecan pegol is discussed given the results recently released of a Phase III trial comparing this agent to Treatment of Physician's Choice.

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.

A new approach for improving epothilone B yield in Sorangium cellulosum by the introduction of vgb epoF genes

Epothilone B has drawn great attention due to its much stronger anticancer activity and weaker side effects compared with taxol. The relative low yield of epothilone B limited its application. In this study, we report the successful introduction of the vgb gene and the epoF gene into Sorangium cellulosum So ce M4 by electroporation for the first time, which was demonstrated by Southern blot analysis. Results of qRT-PCR, SDS-PAGE and western blot analysis confirmed the transcription and expression of the vgb and epoF genes. LC-MS results showed that the epothilones B, A yields were improved and epothilones D, C yields were decreased. The yields of epothilone B were improved by 57.9 ± 0.3, 62.7 ± 0.8 and 122.4 ± 0.7 % through the introduction of vgb gene, epoF gene and both genes into strain So ce M4, respectively. Our study provides a new approach for improving epothilone B yield in S. cellulosum.

Microtubule-stabilizing agents: New drug discovery and cancer therapy

Microtubule-stabilizing agents (MSAs) have been highly successful in the treatment of cancer in the past 20years. To date, three classes of MSAs have entered the clinical trial stage or have been approved for clinical anticancer chemotherapy, and more than 10 classes of novel structural MSAs have been derived from natural resources. The microtubule typically contains two MSA-binding sites: the taxoid site and the laulimalide/peloruside site. All defined MSAs are known to bind at either of these sites, with subtle but significant differences. MSAs with different binding sites may produce a synergistic effect. Although having been extensively applied in the clinical setting, paclitaxel and other approved MSAs still pose many challenges such as multidrug resistance, low bioavailability, poor solubility, high toxicity, and low passage through the blood-brain barrier. A variety of studies focus on the structure-activity relationship in order to improve the pharmaceutical properties of these agents. Here, the mechanisms of action, advancements in pharmacological research, and clinical developments of defined MSAs during the past decade are discussed. The latest discovered MSAs are also briefly introduced in this review. The increasing number of natural MSAs indicates the potential discovery of more novel, natural MSAs with different structural bases, which will further promote the development of anticancer chemotherapy.