Evaluation of Neratinib for Treatment and Prevention of Subsequent CNS Event(s) in Patients With Brain Metastasis of Advanced HER2 Positive Breast Cancer

This is an open-label, non-randomised, phase II study to evaluate the efficacy of neratinib in combination with SOC systemic therapy on CNS metastasis both as for secondary prevention (cohort 1), primary treatment (cohort 2) and for the treatment of LM disease (cohort 3) in subjects with HER2 positive metastatic BC. Subjects with metastatic HER2 positive breast cancer will be eligible for the trial and will be enrolled in one of the following cohorts: Cohort 1: Eligible subjects include HER2 positive metastatic breast cancer subjects treated with at least one line of systemic anti HER2 therapy and pre-treated with local approaches at least for the previous CNS event and currently progressive but locally treated CNS metastasis. Local therapy includes: stereotactic radiosurgery (SRS) or/and WBRT or/and surgery. The study will measure the effect of the drug combination on the time to next CNS event(s). Cohort 2: Eligible subjects include HER2 positive metastatic breast cancer subjects treated with at least one line of systemic anti HER2 therapy or progressing less than 12 months after end of adjuvant therapy with a first diagnosis of brain metastases. The study will measure the objective CNS response in each subject. Cohort 3: Eligible subjects include HER2 positive metastatic breast cancer subjects treated with at least one line of systemic anti HER2 therapy with confirmed LM defined as the presence of malignant cells in the cerebrospinal fluid (CSF) or combination of typical symptoms and MRI. The study will measure the effect of the drug combination on the time to CNS progression including LM progression. As per investigator's choice, eligible subjects in all cohort will receive neratinib in combination with capecitabine or with T-DM1 or with paclitaxel or with vinorelbine as per investigator's choice. Trastuzumab can be added as per investigator's choice to those regimens except for T-DM1. At screening and during the study treatment period (every 9 weeks),