Phase 1b Study of Pegylated Liposomal Doxorubicin and Pembrolizumab in Endocrine-resistant Breast Cancer

Very few patients with endocrine-resistant, hormone-receptor positive metastatic breast cancer respond to single agent immunotherapy. Responses to chemotherapy are usually of short duration. Combining immunotherapy with chemotherapy that has minimal immunosuppressive effect, it may be possible to achieve higher response rates while keeping the immune-associated pattern of long durations of response. This will be a single-center phase 1b study to evaluate the tumor response and appropriate dose of a chemo-immunotherapy regime consisting of treatment with pegylated liposomal doxorubicin (PLD) and pembrolizumab-based in endocrine-resistant breast cancer (ERBC) patients. Up to 15 female patients, ages 18 and above, with pathological diagnosis of breast cancer, estrogen receptor (ER) positive, human epidermal growth factor receptor 2 (HER2-) negative subtype, stage III non-operable, or stage IV disease, who have received at least two lines of hormonal therapy, one of which included aromatase inhibitors will be eligible for enrollment to this single arm study.