Inclusion Criteria:

1. Male subjects aged ≥ 18 years and female subjects who must be postmenopausal (at
least 12 months consecutive amenorrheic or have had a bilateral oophorectomy or, if
they have had a hysterectomy but with ovaries intact, then females must be age 55 or
older and with postmenopausal follicle-stimulating hormone [FSH] levels).

2. Subject is a candidate for chemotherapy in the adjuvant setting.

• Adjuvant therapy must begin within 84 days of the final surgical procedure for
breast cancer.

3. Histologically confirmed Stage I to II invasive breast cancer. Subjects may have more
than one synchronous primary breast tumor.

4. Receptor Status:

- HER2-normal as determined by a negative fluorescence in situ hybridization
(FISH) result or 0 to 1+ by immunohistochemistry (IHC) staining result

- ER-positive, node-negative or ER-positive Grade 1 or 2 node-positive breast
cancer

5. ECOG performance status of 0 or 1

6. Adequate renal function as evidenced by serum creatinine ≤ 1.5 mg/dL or calculated
creatinine clearance ≥ 50 mL/min per the Cockcroft and Gault formula

7. Adequate bone marrow function as evidenced by ANC ≥ 1.5 x 109/L, hemoglobin ≥ 10.0
g/dL, and platelet count ≥ 100 x 109/L

8. Adequate liver function as evidenced by bilirubin ≤ 1.5 times the upper limits of
normal (ULN) and alkaline phosphatase, alanine aminotransferase (ALT), and aspartate
aminotransferase (AST) ≤ 3 x ULN

9. Male subjects must have had a successful vasectomy (confirmed azoospermia), or their
female partners must not be of childbearing potential, or male subjects must agree to
use and have their female partners use a highly effective method of contraception
(e.g., total abstinence, an intrauterine device, a double-barrier method [such as
condom plus diaphragm with spermicide] throughout the entire study period and for 30
days after study drug discontinuation..

10. Voluntary agreement to provide written informed consent and willingness and ability
to comply with all aspects of the protocol

Exclusion Criteria:

1. Stage III and IV invasive breast cancer

2. Prior chemotherapy, radiation therapy, immunotherapy or biotherapy for current breast
cancer

3. Nonmalignant systemic disease (cardiovascular, renal, hepatic, etc) that would
preclude any of the study therapy drugs

4. Subjects with a concurrently active second malignancy other than adequately treated
nonmelanoma skin cancers or in situ cervical cancer

5. Subjects with pre-existing neuropathy > Grade 2

6. Subjects with known positive human immunodeficiency virus (HIV) status

7. Females of childbearing potential. Females will be considered to be of childbearing
potential unless they are postmenopausal (at least 12 months consecutive amenorrheic
or have had a bilateral oophorectomy or, if they have had a hysterectomy but with
ovaries intact, then females must be age 55 or older and with postmenopausal FSH
levels).

8. Subjects with current gastrointestinal disease or other condition resulting in an
inability to take or absorb oral medications

9. Subjects with known allergy or hypersensitivity to eribulin mesylate or its
excipients, or to fluoropyrimidine therapy (with or without documented
dihydropyrimidine dehydrogenase [DPD] deficiency)

10. A clinically significant electrocardiogram (ECG) abnormality, including a marked
baseline prolongation of QT/QTc interval (time between the start of the Q wave and
the end of the T wave / QT interval corrected for heart rate) (e.g., repeated
demonstration of a QTc interval > 500 ms)

11. Any medical or other condition which, in the opinion of the investigator, would
preclude participation in a clinical trial