Evaluation of Biomarkers Associated With Response to Subsequent Therapies in Subjects With HER2-Positive Metastatic Breast Cancer

This study was designed to address the post-authorization measures as agreed with the Committee for Medicinal Products for Human Use (CHMP). Recruitment of subjects into this study was challenging, and following agreement with the European Medicines Agency (EMA) enrollment into this study was halted after the enrollment of 42 of the 225 planned subjects. The primary endpoint of the study evaluated changes in expression of biomarkers associated with immunomodulation between a pre-treatment biopsy and the disease progression biopsy. Secondary efficacy endpoints included overall response rate, clinical benefit rate and progression-free survival (PFS), as well as safety/tolerability. All subjects received study treatment until disease progression, death, unacceptable toxicity, or subject withdrawal. In case of disease progression during the treatment period, the subject was followed-up for 30 days for safety evaluation. In case of study treatment discontinuation for any reasons other than disease progression, the subject was followed-up for safety and efficacy assessments until disease progression, new anticancer therapy, death, withdrawal of consent or end of study, whichever came first. This study supported a better understanding of the rapidly accumulating evidence for the importance of the immune microenvironment in HER2-positive breast cancer and the observed immunomodulation in the neoadjuvant setting could be confirmed in the advanced setting and supported the putative mechanism of action of HER2 dual blockade and its potential function on the tumor microenvironment. No formal comparisons between treatment arms were undertaken.