ATTAIN: Phase III study of etirinotecan pegol versus treatment of physician's choice in patients with metastatic breast cancer and brain metastases.

The increasing incidence of breast cancer brain metastases is a major clinical problem with its associated poor prognosis and limited treatment options. The long-acting topoisomerase-1 inhibitor, etirinotecan pegol, was designed to preferentially accumulate in tumor tissue including brain metastases, providing sustained cytotoxic SN38 levels. Motivated by improved survival findings from subgroup analyses from the Phase III BEACON trial, this ongoing randomized, Phase III trial compares etirinotecan pegol to drugs commonly used for advanced breast cancer in patients with stable, treated breast cancer brain metastases who have been previously treated with an anthracycline, taxane and capecitabine. The primary end point is overall survival. Secondary end points include objective response rate, progression-free survival and time to CNS disease progression or recurrence in patients with/without CNS lesions present at study entry. Trial registration number: NCT02915744.