Analysis Evaluates Efficacy of Eribulin in Metastatic HER2-low Breast Cancer Across Three Studies (Presentation: #259P)

NUTLEY, N.J., Sept. 10, 2022 /PRNewswire/ -- Eisai announced today results from a post-hoc analysis of three randomized, pivotal, Phase 3 studies (EMBRACE trial/Study 305, Study 301, and Study 304) evaluating the efficacy of eribulin mesylate (marketed as HALAVEN^®) versus other chemotherapies (Treatment of Physician's Choice [TPC], capecitabine, and vinorelbine, respectively) in patients living with metastatic breast cancer (mBC) whose tumors have low or no HER2 expression. These data were presented as a poster (Presentation: #259P) at the European Society for Medical Oncology (ESMO) Annual Meeting (#ESMO22), held virtually and in-person in Paris, France from September 9-13, 2022.

The HER2-low breast cancer subtype is a newly defined subset consisting of tumors that would have previously been considered HER2-negative based on an immunohistochemistry (IHC) assay and an in situ hybridization (ISH) assay. HER2-low tumors express low amounts of the HER2 protein, but not enough to be considered HER2-positive. HER2-low is defined as an IHC of 1+ or 2 with a negative ISH. Of the approximate 288,000 new cases of female breast cancer expected to be diagnosed in the U.S. in 2022, it is estimated that approximately 80-85% of patients would previously have been considered to have the HER2-negative subtype. Of those patients, about 60% would now be considered to have the HER2-low subtype.

"In this post-hoc analysis, the outcomes seen in mBC patients whose tumors are considered HER2-low are consistent with the results of the three pivotal Phase 3 clinical trials," said Dr. Takashi Owa, Chief Scientific Officer, Senior Vice President, Eisai Co., Ltd. "As the oncology community's understanding of mBC continues to evolve, it's important that we continue to evaluate the role of existing therapies in new contexts to contribute to the body of knowledge that is available to health care professionals."

The post-hoc analysis included data from three trials— eribulin vs. TPC (NCT00388726, EMBRACE trial/Study 305), eribulin vs. capecitabine (NCT00337103, Study 301), and eribulin vs. vinorelbine (NCT02225470, Study 304) in patients with locally recurrent or mBC who had prior lines of chemotherapy treatments (≤2 for Study 301; 2-5 for Study 304 and EMBRACE Trial/Study 305) including an anthracycline and a taxane. A total of 1,589 eligible patients were enrolled in the EMBRACE trial/Study 305, Study 301, and Study 304, and baseline characteristics were generally balanced between treatment arms in all studies.

Median overall survival (OS), median progression free survival (PFS) and objective response rate (ORR) were analyzed. PFS and ORR were measured per Response Evaluation Criteria in Solid Tumors Version (RECIST) (v1.0 for EMBRACE trial/Study 305 and Study 301; v1.1 for Study 304) by independent imaging review. ORR was measured in evaluable patients (EMBRACE trial/Study 305) and in the intent-to-treat population (Study 301 and Study 304).

In the post-hoc analysis, OS, PFS, and ORR among patients with HER2-low or HER2-negative status were generally similar to those of the eribulin treatment arms overall in each of the EMBRACE trial/Study 305, Study 301 and Study 304. Efficacy results for patients with HER2-low and HER2-negative status across all three studies are summarized in the table below:

Metastatic breast cancer (mBC) is an advanced stage of the disease that occurs when cancer spreads beyond the breast to other parts of the body. It is estimated there were more than 2,261,000 new cases of breast cancer and more than 684,000 deaths from the disease globally in 2020. In 2022, it is estimated that approximately 288,000 women will be diagnosed with breast cancer in the United States and over 43,000 women will die from the disease. It is estimated that 30% of people with early-stage breast cancers will go on to develop metastatic disease, and approximately 6% of women with breast cancer will have metastatic disease at the time of diagnosis. Metastatic breast cancer has a poor prognosis compared to non-metastatic breast cancer. The estimated 5-year relative survival rate for women with mBC is 28%.

HALAVEN (eribulin mesylate) Injection is indicated for the treatment of patients with metastatic breast cancer (mBC) who have previously received at least 2 chemotherapeutic regimens for the treatment of metastatic disease. Prior therapy should have included an anthracycline and a taxane in either the adjuvant or metastatic setting.

Eribulin is a microtubule dynamics inhibitor in the halichondrin class with a novel mechanism of action, developed in-house by Eisai. Structurally, eribulin is a simplified and synthetically produced version of halichondrin B, a natural product isolated from the marine sponge Halichondria okadai. Eribulin is believed to work by inhibiting the growth phase of microtubule dynamics which prevents cell division. In addition, non-clinical studies showed eribulin's unique actions in the tumor microenvironment such as an increase in vascular perfusion and permeability in tumor cores, promotion of the epithelial state, decrease in capacity of breast cancer cells to migrate, etc.

Neutropenia: Severe neutropenia (ANC <500/mm3) lasting >1 week occurred in 12% of patients with mBC. Febrile neutropenia occurred in 5% of patients with mBC and 2 patients (0.4%) died from complications. Patients with mBC with elevated liver enzymes >3 × ULN and bilirubin >1.5 × ULN experienced a higher incidence of Grade 4 neutropenia and febrile neutropenia than patients with normal levels. Monitor complete blood cell counts prior to each dose, and increase the frequency of monitoring in patients who develop Grade 3 or 4 cytopenias. Delay administration and reduce subsequent doses in patients who experience febrile neutropenia or Grade 4 neutropenia lasting >7 days.

Peripheral Neuropathy: Grade 3 peripheral neuropathy occurred in 8% of patients with mBC (Grade 4=0.4%) and 22% developed a new or worsening neuropathy that had not recovered within a median follow-up duration of 269 days (range 25-662 days). Neuropathy lasting >1 year occurred in 5% of patients with mBC. Patients should be monitored for signs of peripheral motor and sensory neuropathy. Withhold HALAVEN in patients who experience Grade 3 or 4 peripheral neuropathy until resolution to Grade 2 or less.

Embryo-Fetal Toxicity: HALAVEN can cause fetal harm when administered to a pregnant woman. Advise females of reproductive potential to use effective contraception during treatment with HALAVEN and for at least 2 weeks following the final dose. Advise males with female partners of reproductive potential to use effective contraception during treatment with HALAVEN and for 3.5 months following the final dose.

QT Prolongation: Monitor for prolonged QT intervals in patients with congestive heart failure, bradyarrhythmias, drugs known to prolong the QT interval, and electrolyte abnormalities. Correct hypokalemia or hypomagnesemia prior to initiating HALAVEN and monitor these electrolytes periodically during therapy. Avoid in patients with congenital long QT syndrome.

In patients with mBC receiving HALAVEN, the most common adverse reactions (≥25%) were neutropenia (82%), anemia (58%), asthenia/fatigue (54%), alopecia (45%), peripheral neuropathy (35%), nausea (35%), and constipation (25%). Febrile neutropenia (4%) and neutropenia (2%) were the most common serious adverse reactions. The most common adverse reaction resulting in discontinuation was peripheral neuropathy (5%).

Lactation: Because of the potential for serious adverse reactions in breastfed infants from eribulin mesylate, advise women not to breastfeed during treatment with HALAVEN and for 2 weeks after the final dose.

Hepatic and Renal Impairment: A reduction in starting dose is recommended for patients with mild or moderate hepatic impairment and/or moderate or severe renal impairment.

For more information about HALAVEN, click here for the full Prescribing Information.

HALAVEN^® is a registered trademark used by Eisai Inc. under license from Eisai R&D Management Co., Ltd.

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