Capecitabine 7/7 Schedule With Neratinib in Patients With Metastatic HER2-Positive Breast Cancer

Inclusion Criteria:

- Aged ≥18 years at signing of informed consent.

- Histologically confirmed MBC, current stage IV.

- Documented HER2 overexpression (immunohistochemistry (IHC) 3+ or gene-amplified tumor
with fluorescence in situ hybridization (FISH) ratio of ≥ 2.0.

- For phase Ib, any line of prior treatments is permitted including prior neratinib and
capecitabine.

- For phase II, up to 4 prior chemotherapy-based treatments in the metastatic setting
are allowed. Patients must have had prior trastuzumab-based therapy. Prior neratinib
treatment is not permitted. Prior capecitabine is allowed, if not combined with
neratinib.

- Measurable or non-measurable disease is permitted as defined by Response Evaluation
Criteria in Solid Tumors version 1.1 (RECIST v1.1) for phase 1b. For phase 2, patients
must have measurable disease as defined in RECIST v1.1.

- Left ventricular ejection fraction (LVEF) ≥50% measured by multiple-gated acquisition
scan (MUGA) or echocardiogram (ECHO).

- Eastern Cooperative Oncology Group (ECOG) status of 0 to 1

- Hematologic parameters: white blood cell (WBC) count of > 3000/ul, absolute neutrophil
count (ANC) ≥ 1000/ul, platelets ≥ 50,000/ul, hemoglobin ≥ 8.0 g/dl

- Non-hematologic parameters: bilirubin ≤ 1.5 mg/dl, AST/ALT ≤ 3.0 x upper limit of
normal (ULN) (≤ 5.0 x ULN if liver metastases are involved)

- Creatinine ≤1.5 mg/dl Patients with "treated and stable" brain lesions of a duration
of ≥ 2 months may be enrolled.

- Negative β-human chorionic gonadotropin (hCG) pregnancy test for premenopausal women
of reproductive capacity (those who are biologically capable of having children) and
for women less than 12 months after menopause.

- Women of childbearing potential must agree and commit to the use of a highly effective
method of contraception as determined to be acceptable by the investigator, from the
time of informed consent until 28 days after the last dose of the investigational
product. Men must agree and commit to use a barrier method of contraception while on
treatment and for 3 months after last dose of investigational products.

- Provide written, informed consent to participate in the study and follow the study
procedures

Exclusion Criteria:

- Active uncontrolled cardiac disease, including cardiomyopathy, congestive heart
failure (New York Heart Association functional classification of ≥2), unstable angina,
myocardial infarction within 12 months of enrollment, or ventricular arrhythmia

- Received prior therapy resulting in a cumulative epirubicin dose >900 mg/m2 or
cumulative doxorubicin dose >450 mg/m2. If another anthracycline or more than one
anthracycline has been used, the cumulative dose must not exceed the equivalent of 450
mg/m^2 doxorubicin.

- Any major surgery ≤28 days prior to the initiation of investigational products, or
received anti-cancer therapy (including chemotherapy, biological therapy, hormonal
therapy, investigational agents, or other anti-cancer therapy) administered ≤14 days
prior to the initiation of investigational products.

- Received radiation therapy ≤14 days prior to initiation of investigational products.

- QTc interval >450 ms for men or 470 ms for women, or known history of QTc prolongation
or Torsades de Pointes.

- Active hepatitis B or C

- Active infection or unexplained fever >38.5°C (>101.3°F) within 2 weeks prior to
enrollment.

- Significant chronic gastrointestinal disorder with diarrhea as a major symptom (e.g.,
Crohn's disease, malabsorption, or Grade ≥2 diarrhea of any etiology screening).

- Known dihydropyrimidine dehydrogenase deficiency.

- Known hypersensitivity to 5-fluorouracil or to any component of the investigational
products or compounds of similar chemical composition.

- Pregnant patients or currently breast-feeding.