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Background
Eribulin mesylate, a non-taxane microtubule dynamics inhibitor, is isolated from the sea sponge Halichondria okadai. Although the exact mechanism is unknown, it is believed that eribulin’s anti-mitotic activity works via inhibition of the growth phase of microtubule dynamics, without affecting the shortening phase, thus sequestering tubulin into non-productive aggregates. Eribulin mesylate is used in the treatment of patients with locally advanced or metastatic breast cancer who have previously been treated with at least 2 chemotherapeutic regimens, including an anthracycline and a taxane. In in-vitro studies, eribulin displayed anti-proliferative activity against human breast cancer cell lines. Regression and elimination of breast tumors were observed in human tumor xenograft models. In the randomized, open-label, multi-national, phase III EMBRACE trial in patients with locally recurrent or metastatic breast cancer, median overall survival (OS) was significantly longer in patients who received intravenous (i.v.) eribulin (n = 508) [13.1 months] compared with that in patients who received a treatment of physician's choice (n = 254) [10.6 months; hazard ratio 0.81; 95 % confidence interval [CI]: 0.66, 0.99; p = 0.041]. Prior to enrolment, subjects had received between 2 and 5 chemotherapeutic regimens, including an anthracycline and a taxane. Consistent with the findings of earlier phase I and II clinical trials, eribulin was reported to have a manageable tolerability profile in the EMBRACE trial. Peripheral neuropathy (incidence 5 %) was the most common adverse event resulting in the discontinuation of eribulin treatment. The most common grade 3/4 adverse events in the eribulin group were neutropenia, leukopenia and asthenia or fatigue (Perry, 2011). In a single-arm, multi-center open-label, phase II trial, Aogi et al (2011) evaluated the effectiveness and tolerability of eribulin in Japanese patients with heavily pre-treated metastatic breast cancer (MBC). Patients pre-treated with an anthracycline and a taxane received 1.4 mg/m(2) eribulin mesylate (2- to 5-min i.v. infusion on days 1 and 8 of a 21-day cycle). The primary efficacy end point was overall response rate (ORR) by independent review. Patients (n = 80) had received a median of 3 prior chemotherapeutic regimens (range of 1 to 5). ORR was 21.3 % [95 % CI: 12.9 to 31.8; all partial responses (PRs)], stable disease (SD) occurred in 30 patients (37.5 %) and the clinical benefit rate (complete response + PR + SD greater than or equal to 6 months) was 27.5 % (95 % CI: 18.1 to 38.6). Median duration of response was 3.9 months (95 % CI: 2.8 to 4.9), progression-free survival (PFS)was 3.7 months (95 % CI: 2.0 to 4.4) and OS was 11.1 months (95 % CI: 7.9 to 15.8). The most frequent treatment-related grade 3/4 adverse events were neutropenia (95.1 %), leukopenia (74.1 %) and febrile neutropenia (13.6 %). Grade 3 peripheral neuropathy occurred in 3.7 % of patients (no grade 4). The authors concluded that eribulin exhibited effectiveness and tolerability in Japanese patients with heavily pre-treated MBC. In a phase III open-label, randomized trial, Cortes et al (2011) compared OS of heavily pre-treated patients receiving eribulin versus currently available treatments. Women with locally recurrent or MBC were randomly allocated (2:1) to eribulin mesylate (1.4 mg/m(2) administered intravenously during 2 to 5 mins on days 1 and 8 of a 21-day cycle) or treatment of physician's choice (TPC). Patients had received between 2 and 5 previous chemotherapeutic regimens (2 or more for advanced disease), including an anthracycline and a taxane, unless contraindicated. Randomization was stratified by geographical region, previous capecitabine treatment, and human epidermal growth factor receptor 2 status. Patients and investigators were not masked to treatment allocation. The primary endpoint was OS in the intention-to-treat population. A total of 762 women were randomly allocated to treatment groups (eribulin, n = 508; TPC, n = 254). Overall survival was significantly improved in women assigned to eribulin (median 13.1 months, 95 % CI: 11.8 to 14.3) compared with TPC (10.6 months, 9.3 to 12.5; hazard ratio 0•81, 95 % CI: 0.66 to 0.99; p = 0.041). The most common adverse events in both groups were asthenia or fatigue (270 [54 %] of 503 patients on eribulin and 98 [40 %] of 247 patients on TPC at all grades) and neutropenia (260 [52 %] patients receiving eribulin and 73 [30 %] of those on TPC at all grades). Peripheral neuropathy was the most common adverse event leading to discontinuation from eribulin, occurring in 24 (5 %) of 503 patients. The authors concluded that eribulin showed a significant and clinically meaningful improvement in OS compared with TPC in women with heavily pre-treated MBC. On November 15, 2010, the Food and Drug Administration (FDA) approved eribulin mesylate (Halaven) for the treatment of patients with MBC who have received at least 2 prior chemotherapeutic regimens for late-stage disease. Before receiving Halaven, patients should have received prior anthracycline- and taxane-based chemotherapy for early- or late-stage breast cancer. The most common side effects reported by women treated with Halaven include alopecia (hair loss), anemia, asthenia (weakness), constipation, fatigue, leukopenia (a decrease in the number of white blood cells), nausea, neutropenia (a decrease in infection-fighting white blood cells), and peripheral neuropathy (nerve damage). The recommended dose of Halaven is 1.4 mg/m2 administered intravenously over 2 to 5 mins on days 1 and 8 of a 21-day cycle. The National Comprehensive Cancer Network's Drugs and Biologic Compendium (2012) lists eribulin as a preferred single agent for recurrent or metastatic breast cancer that is - Hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative with visceral crisis; or
- HER2-negative and either hormone receptor-negative or hormone receptor-positive and endocrine therapy refractory; or
- Progressive with no clinical benefit after 3 consecutive endocrine therapy regimens or with symptomatic visceral disease
Eribulin mesylate is also being investigated in the treatment of other solid tumors including head and neck cancer, non-small-cell lung cancer, ovarian cancer, pancreatic cancer, prostate cancer, and soft-tissue sarcoma. Its use for these malignancies is undergoing various phases of clinical trial. In a non-randomized multi-center phase II clinical study, Schoffski et al (2011) evaluated the activity and safety of eribulin in 4 strata of patients with different types of soft-tissue sarcoma. Patients were included if they had progressive or high-grade soft-tissue sarcoma and had received no more than 1 previous combination chemotherapy or up to 2 single drugs for advanced disease. They were stratified by the type of soft-tissue sarcoma they had. Eribulin was given intravenously at a concentration of 1.4 mg/m(2) over 2 to 5 mins at days 1 and 8 every 3 weeks to primarily assess PFS at 12 weeks (RECIST 1.0), which these researchers evaluated in all patients who started treatment. Safety analyses were done in all patients who started treatment. Of 128 patients included, 37 had adipocytic sarcoma, 40 had leiomyosarcoma, 19 had synovial sarcoma, and 32 had other sarcomas; 12 (31.6 %) of 38 patients with leiomyosarcoma evaluable for the primary endpoint, 15 (46.9 %) of 32 patients with adipocytic sarcoma, 4 (21.1 %) of 19 with synovial sarcoma, and 5 (19.2 %) of 26 in other sarcomas were progression-free at 12 weeks. The most common grade 3 to 4 adverse events were neutropenia (66 [52 %] of 127 patients evaluable for safety), leucopenia (44 [35 %]), anemia (9 [7 %]), fatigue (9 [7 %]), febrile neutropenia (8 [6 %]), abnormal alanine aminotransferase concentrations (6 [5 %]), mucositis (4 [3 %]), and sensory neuropathy (4 [3 %]). The authors concluded that eribulin deserves further study in this setting, based on PFS at 12 weeks in leiomyosarcoma and adipocytic sarcoma. In a 2-cohort phase II clinical study, Hensley et al (2012) assessed the effectiveness of eribulin in platinum-resistant and platinum-sensitive recurrent ovarian cancer. Patients with recurrent, measurable epithelial ovarian cancer who had received less than or equal to 2 prior cytotoxic regimens and who had adequate organ function were enrolled into 2 separate cohorts: (i) platinum-resistant patients (who had a progression-free interval less than 6 months after their last platinum-based therapy), and (ii) platinum-sensitive patients (who had a progression-free interval greater than or equal to 6 months after their last platinum-based therapy). Eribulin 1.4 mg/m(2) was administered over 15 mins intravenously on days 1 and 8 every 21 days. Effectiveness was determined by objective response on computed tomography studies. In the platinum-resistant cohort, 37 patients enrolled, and 36 patients were evaluable for response and toxicity. Two patients achieved a PR (5.5 %), and 16 patients (44 %) had SD as their best response. The median PFS was 1.8 months (95 % CI: 1.4 to 2.8 months). In the platinum-sensitive cohort, 37 patients enrolled, and all were evaluable for response. Seven patients achieved a PR (19 %). The median PFS was 4.1 months (95 % CI, 2.8 to 5.8 months). The major toxicity was grade 3 or 4 neutropenia (42 % of platinum-resistant patients; 54 % of platinum-sensitive patients). The authors concluded that eribulin produced an objective response in 5.5 % of women with platinum-resistant, recurrent ovarian cancer and in 19 % of women with platinum-sensitive disease. The median PFS was 1.8 months in the platinum-resistant group and 4.1 months in the platinum-sensitive group. In an open-label, single-arm phase II trial, de Bono et al (2012) evaluated eribulin mesylate in patients with metastatic castration-resistant prostate cancer (CRPC) with or without previous taxane exposure. Men with histologically proven CRPC, with or without prior taxane exposure, were enrolled in this study. Patients received eribulin mesylate 1.4 mg/m(2) as a 2- to 5-min i.v. bolus infusion on days 1 and 8 of a 21-day cycle. The primary efficacy end point was prostate-specific antigen (PSA) response rate. A total of 108 patients were assessable for safety (50 were taxane-pretreated) and 105 for efficacy in the per-protocol population. The median age of patients was 71 years and median number of cycles was 4. PSA decreases of greater than or equal to 50 % were achieved in 22.4 % and 8.5 % of taxane-naive and taxane-pretreated patients, respectively. The most common grade 3/4 adverse event was neutropenia, seen in 22.4 % of chemo-naive and 40 % of taxane-pretreated men. Grade 3 peripheral neuropathy occurred in none of the taxane-naive patients and 6.0 % of taxane-pretreated patients. The authors concluded that eribulin mesylate demonstrated activity and a relatively favorable toxicity profile in metastatic CRPC. Scarpace (2012) reviewed eribulin's medication profile, including pharmacology, pharmacokinetic properties, efficacy, and tolerability. PubMed, the Cochrane Central Register of Controlled Trials, and Clinical Trials.gov were searched from the beginning of each database through January 3, 2012, for relevant articles on human studies published in English. Search terms included eribulin, eribulin mesylate, and Halaven. Clinical trials, case reports, comparative studies, meta-analyses, evaluation studies, controlled clinical trials, and randomized controlled trials were included as search limits. The references from selected articles were also reviewed to identify additional publications. Eisai, the manufacturer of eribulin mesylate, was also contacted for information regarding trials listed in Clinicaltrials.gov but not yet published. One phase III trial was identified that evaluated eribulin for use in patients with MBC. Four phase II trials were identified that studied eribulin in patients with head and neck, pancreatic, and non-small-cell lung cancers. The median OS among previously treated MBC patients treated with eribulin was 13.1 months compared with 10.6 months (p = 0.041) with other active chemotherapy for this setting. In non-small-cell lung cancer, median OS in eribulin-treated patients has been reported as 9.4 months in an unselected population and varies according to taxane sensitivity: 12.6 months in taxane-sensitive disease versus 8.9 months in taxane-resistant disease. Patients with head and neck or pancreatic cancers did not experience improvements in response rates or survival outcomes when treated with eribulin in clinical trials. The authors noted that eribulin is approved by the FDA for patients with previously treated MBC and has demonstrated a survival benefit compared with standard treatment options in this setting. Non-small-cell lung cancer patients had improved response rates when treated with eribulin in open-label, non-randomized, phase II trials reported in abstract form. Eribulin was not effective in the treatment of head and neck, or pancreatic cancer in phase II trials.
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