A Study Looking the Incidence and Severity of Diarrhea in Patients With Early-Stage HER2+ Breast Cancer Treated With Neratinib and Loperamide

Open to people ages 18 years and up

1. Aged ≥18 years at signing of informed consent
2. Histologically confirmed stage 1 through stage 3c primary adenocarcinoma of the breast
3. Documented HER2 overexpression or gene-amplified tumor by a validated approved method
4. Patients must have completed a course of prior adjuvant trastuzumab or experienced side effects that resulted in early discontinuation of trastuzumab that have since resolved
5. The last dose of trastuzumab must have been given >2 weeks and ≤1 year (365 days) from enrollment
6. Physician assessment confirming that the patient is negative for local or regional recurrence of disease or metastatic disease at the time of study entry, including:
7. Per standard of care, bone scan or positron emission tomography (PET) scan;required only if alkaline phosphatase (ALP) is ≥2 x upper limit of normal (ULN)and/or there are symptoms of metastatic bone disease. A confirmatory imaging study is required if the results from the bone scan are questionable.
8. Per standard of care, computed tomography (CT), magnetic resonance imaging (MRI)or ultrasound of the abdomen and chest; required only if aspartate aminotransferase (AST)/alanine aminotransferase (ALT) or ALP is ≥2 x ULN.
9. Other radiologic assessments may be performed to rule out underlying breast cancer recurrence if indicated and as per standard of care (for patients enrolled starting with Amendment 6.1).
10. Left ventricular ejection fraction (LVEF) ≥50% measured by multiple-gated acquisition scan (MUGA) or echocardiogram (ECHO)
11. Eastern Cooperative Oncology Group (ECOG) status of 0 to 1
12. 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 are considered postmenopausal if they are ≥12 months without menses, in the absence of endocrine or anti-endocrine therapies.]
13. . Women of childbearing potential must agree and commit to the use of a highly effective non-hormonal method of contraception, ie, intrauterine device, bilateral tubal ligation, vasectomized partner, or abstinence (only when it is the preferred lifestyle of the patient), from the time of informed consent until 28 days after the last dose of the investigational products. Man (male patient) with female partner of childbearing potential must agree and commit to use condom and the female partner must agree and commit to use a highly effective method of contraception (ie, any of the above methods, or for females, hormonal contraception associated with inhibition of ovulation) while on treatment and for 3 months after last dose of investigational products.
14. . Recovery (ie, to Grade 1 or baseline) from all clinically significant AEs related to prior therapies (excluding alopecia, neuropathy, and nail changes)
15. . Provide written, informed consent to participate in the study and follow the study procedures