Pharmacotherapeutic group: Other antineoplastic agents, ATC code: L01XX41
Eribulin mesilate is a microtubule dynamics inhibitor belonging to the halichondrin class of antineoplastic agents. It is a structurally simplified synthetic analogue of halichondrin B, a natural product isolated from the marine sponge Halichondria okadai.
Eribulin inhibits the growth phase of microtubules without affecting the shortening phase and sequesters tubulin into non-productive aggregates. Eribulin exerts its effects via a tubulin-based antimitotic mechanism leading to G2/M cell-cycle block, disruption of mitotic spindles, and, ultimately, apoptotic cell death after prolonged and irreversible mitotic blockage.
Clinical efficacy
Breast cancer
The efficacy of eribulin in breast cancer is primarily supported by two randomized Phase 3 comparative studies.
The 762 patients in the pivotal Phase 3 EMBRACE study (Study 305) had locally recurrent or metastatic breast cancer, and had previously received at least two and a maximum of five chemotherapy regimens, including an anthracycline and a taxane (unless contraindicated). Patients must have progressed within 6 months of their last chemotherapeutic regimen. The HER2 status of the patients was: 16.1% positive, 74.2% negative and 9.7% unknown, whilst 18.9% of patients were triple negative. They were randomized 2:1 to receive either eribulin, or treatment of physician's choice (TPC), which consisted of 97% chemotherapy (26% vinorelbine, 18% gemcitabine, 18% capecitabine, 16% taxane, 9% anthracycline, 10% other chemotherapy), or 3% hormonal therapy.
The study met its primary endpoint with an overall survival (OS) result that was statistically significantly better in the eribulin group compared to TPC at 55% of events.
This result was confirmed with an updated overall survival analysis carried out at 77% of events.
Study 305 - Updated Overall Survival ( ITT Population)

By independent review, the median progression free survival (PFS) was 3.7 months for eribulin compared to 2.2 months for the TPC arm (HR 0.865, 95% CI: 0.714, 1.048, p=0.137). In response evaluable patients, the objective response rate by the RECIST criteria was 12.2% (95% CI: 9.4%, 15.5%) by independent review for the eribulin arm compared to 4.7% (95% CI: 2.3%, 8.4%) for the TPC arm.
The positive effect on OS was seen in both taxane-refractory and non-refractory groups of patients. In the OS update, the HR for eribulin versus TPC was 0.90 (95% CI: 0.71, 1.14) in favour of eribulin for taxane-refractory patients and 0.73 (95% CI: 0.56, 0.96) for patients not taxane-refractory.
The positive effect on OS was seen both in capecitabine-naïve and in capecitabine pre-treated patient groups. The updated OS analysis showed a survival benefit for the eribulin group compared to TPC both in capecitabine pre-treated patients with a HR of 0.787 (95% CI: 0.645, 0.961), and for the capecitabine-naïve patients with a corresponding HR of 0.865 (95% CI: 0.606, 1.233).
The second Phase 3 study in earlier line metastatic breast cancer, Study 301, was an open-label, randomized, study in patients (n=1102) with locally advanced or metastatic breast cancer to investigate the efficacy of eribulin monotherapy compared to capecitabine monotherapy in terms of OS and PFS as co-primary endpoint.
Patients had previously received up to three prior chemotherapy regimens, including both an anthracycline and a taxane and a maximum of two for advanced disease, with the percentage who had received 0, 1 or 2 prior chemotherapy treatments for metastatic breast cancer being 20.0%, 52.0% or 27.2% respectively. The HER2 status of the patients was: 15.3% positive, 68.5% negative and 16.2% unknown, whilst 25.8% of patients were triple negative.
Study 301 - Overall Survival (ITT Population)

Progression free survival assessed by independent review was similar between eribulin and capecitabine with medians of 4.1 months vs 4.2 months (HR 1.08; [95% CI: 0.932, 1.250]) respectively. Objective response rate as assessed by independent review was also similar between eribulin and capecitabine; 11.0% (95% CI: 8.5, 13.9) in the eribulin group and 11.5% (95% CI: 8.9, 14.5) in the capecitabine group.
The overall survival in patients in HER2 negative and HER2 positive patients in the eribulin and control groups in Study 305 and Study 301 is shown below:
| Efficacy Parameter | Study 305 Updated Overall Survival ITT Population |
| HER2 Negative | HER2 Positive |
| | Eribulin (n = 373) | TPC (n = 192) | Eribulin (n = 83) | TPC (n = 40) |
| Number of Events | 285 | 151 | 66 | 37 |
| Median months | 13.4 | 10.5 | 11.8 | 8.9 |
| Hazard Ratio (95% CI) | 0.849 (0.695, 1.036) | 0.594 (0.389, 0.907) |
| p-value (log rank) | 0.106 | 0.015 |
| Efficacy Parameter | Study 301 Overall Survival ITT Population |
| HER2 Negative | HER2 Positive |
| | Eribulin (n = 375) | Capecitabine (n = 380) | Eribulin (n = 86) | Capecitabine (n = 83) |
| Number of Events | 296 | 316 | 73 | 73 |
| Median months | 15.9 | 13.5 | 14.3 | 17.1 |
| Hazard Ratio (95% CI) | 0.838 (0.715, 0.983) | 0.965 (0.688, 1.355) |
| p-value (log rank) | 0.030 | 0.837 |
Note: Concomitant anti-HER2 therapy was not included in Study 305 and Study 301.
Liposarcoma
In liposarcoma the efficacy of eribulin is supported by the pivotal Phase 3 sarcoma study (Study 309). The patients in this study (n=452) had locally recurrent, inoperable and/or metastatic soft tissue sarcoma of one of two subtypes – leiomyosarcoma or liposarcoma. Patients had received at least two prior chemotherapy regimens, one of which must have been an anthracycline (unless contraindicated).
Patients must have progressed within 6 months of their last chemotherapeutic regimen. They were randomized 1:1 to receive either eribulin 1.23 mg/m2 on days 1 and 8 of a 21 day cycle or dacarbazine 850 mg/m2, 1000 mg/m2 or 1200 mg/m2 (dose determined by the investigator prior to randomization), every 21 days.
In Study 309, a statistically significant improvement in OS was observed in patients randomized to the eribulin arm compared to the control arm. This translated into a 2 month improvement in median OS (13.5 months for eribulin treated patients vs. 11.5 months for dacarbazine treated patients). There was no significant difference in progression-free survival or overall response rate between the treatment arms in the overall population.
Treatment effects of eribulin were limited to patients with liposarcoma (45% dedifferentiated, 37% myxoid/round cell and 18% pleomorphic in Study 309) based on pre-planned subgroup analyses of OS and PFS. There was no difference in efficacy between eribulin and dacarbazine in patients with advanced or metastatic leiomyosarcoma.
| | Study 309 Liposarcoma Subgroup | Study 309 Leiomyosarcoma Subgroup | Study 309 ITT Population |
| Eribulin (n=71) | Dacarbazine (n=72) | Eribulin (n=157) | Dacarbazine (n=152) | Eribulin (n=228) | Dacarbazine (n=224) |
| Overall survival |
| Number of Events | 52 | 63 | 124 | 118 | 176 | 181 |
| Median months | 15.6 | 8.4 | 12.7 | 13.0 | 13.5 | 11.5 |
| Hazard Ratio (95% CI) | 0.511 (0.346, 0.753) | 0.927 (0.714, 1.203) | 0.768 (0.618, 0.954) |
| Nominal p- value | 0.0006 | 0.5730 | 0.0169 |
| Progression-free survival |
| Number of Events | 57 | 59 | 140 | 129 | 197 | 188 |
| Median months | 2.9 | 1.7 | 2.2 | 2.6 | 2.6 | 2.6 |
| Hazard Ratio (95% CI) | 0.521 (0.346, 0.784) | 1.072 (0.835, 1.375) | 0.877 (0.710, 1.085) |
| Nominal p- value | 0.0015 | 0.5848 | 0.2287 |
Study 309 - Overall Survival in the Liposarcoma Subgroup

Study 309 – Progression Free Survival in the Liposarcoma Subgroup
Paediatric population
Breast Cancer
The European Medicines Agency has waived the obligation to submit the results of studies with the reference medicinal product containing eribulin in all subsets of the paediatric population in the indication of breast cancer (see section 4.2 for information on paediatric use).
Soft Tissue Sarcoma
Efficacy of eribulin was assessed but not established in three open-label studies:
Study 113 was a Phase 1, open-label, multicentre, dose-finding study that assessed eribulin in paediatric patients with refractory or recurrent solid tumours and lymphomas but excluding CNS tumours. A total of 22 paediatric patients (age range: 3 to 17 years) were enrolled and treated. The patients were administered eribulin intravenously on Days 1 and 8 of a 21-day cycle at three dose levels (0.97, 1.23 and 1.58 mg/m2). The maximum tolerated dose (MTD)/recommended Phase 2 dose (RP2D) of eribulin was determined as 1.23 mg/m2 on Days 1 and 8 of a 21-day cycle.
Study 223 was a Phase 2, open-label, multicentre study that assessed the safety and preliminary activity of eribulin in paediatric patients with refractory or recurrent rhabdomyosarcoma (RMS), non-rhabdomyosarcoma soft tissue sarcoma (NRSTS) or Ewing sarcoma (EWS). Twenty-one paediatric patients (age range: 2 to 17 years) were enrolled and treated with eribulin at a dose of 1.23 mg/m2 intravenously on Days 1 and 8 of a 21-day cycle (the RP2D from Study 113). No patient achieved confirmed partial response (PR) or complete response (CR).
Study 213 was a Phase 1/2, open-label, multicentre study to evaluate the safety and efficacy of eribulin in combination with irinotecan hydrochloride in paediatric patients with relapsed/refractory solid tumours and lymphomas but excluding CNS tumours (Phase 1), and to assess the efficacy of the combination treatment in paediatric patients with relapsed/refractory RMS, NRSTS and EWS (Phase 2). A total of 40 paediatric patients were enrolled and treated in this study. In Phase 1, 13 paediatric patients (age range: 4 to 17 years) were enrolled and treated; the RP2D was determined as eribulin 1.23 mg/m2 on Days 1 and 8 with irinotecan hydrochloride 40 mg/m2 on Days 1 to 5 of a 21-day cycle.
In Phase 2, 27 paediatric patients (age range: 4 to 17 years) were enrolled and treated at the RP2D. Three patients had confirmed PR (1 patient in each of the RMS, NRSTS, and EWS histology cohorts). The objective response rate (ORR) was 11.1%.
No new safety signals were observed in the three paediatric studies (see section 4.8); however, due to the small patient populations no firm conclusions can be made.