Phase I/IIa Trial of Gemcitabine Plus Trastuzumab and Pertuzumab in Previously Treated Metastatic HER2+ Breast Cancer

Inclusion Criteria

• Adult males or females (aged 18 or older) with histologically confirmed, metastatic human epidermal growth factor receptor 2 (HER2)+ (by immunohistochemistry (IHC) 3+ or fluorescence in situ hydridization (FISH) ratio ≥ 2.0) breast cancer
• Have progressed on at least one prior line of chemotherapy plus HER2 directed therapy such as trastuzumab and/or pertuzumab in the metastatic setting. T-DM1 would count as a line of therapy and patients previously treated with T-DM1 are eligible.
• Have not been treated with gemcitabine in the metastatic setting
• Measurable disease per Response Evaluation in Solid Tumors (RECIST) 1.1 criteria
• Eastern Cooperative Oncology Group (ECOG) performance status 2≤
• Left Ventricular Ejection Fraction (LVEF) ≥ 50% at baseline as determined by either echocardiogram (ECHO) or multiple gated acquisition scan (MUGA)
• Adequate bone marrow function as indicated by the following: absolute neutrophil count (ANC) >1500/µL; Platelets ≥100,000/µL; Hemoglobin >10 g/dL
• Adequate renal function, as indicated by creatinine ≤1.5x upper limit of normal (ULN)
• Adequate liver function, as indicated by bilirubin ≤1.5x ULN, aspartic transaminase (AST) or alanine transaminase (ALT) <2x ULN unless related to metastatic breast cancer to the liver (in which case AST/ALT < 5x ULN is allowed).
• Signed informed consent
• Adequate birth control in sexually active women of childbearing potential

Exclusion Criteria

• Active uncontrolled infection or major concurrent illness which in the opinion of the investigator would render the participant unsafe to proceed with the study
• Uncontrolled central nervous system (CNS) metastases. Treated, non-progressing CNS disease (documented by brain magnetic resonance imaging [MRI]) off corticosteroids for at least 1 month potential participants are eligible.
• Women who are pregnant or lactating
• Prior chemotherapy within the last 3 weeks (last 6 weeks for nitrosureas/mitomycin)
• Prior radiation therapy within the last 4 weeks; prior radiation therapy to indicator lesion (unless objective disease recurrence or progression within the radiation portal has been documented since completion of radiation)
• Other concomitant active malignancies
• History of significant cardiac disease, cardiac risk factors or uncontrolled arrhythmias
• Ejection fraction <50% or below the lower limit of the institutional normal range, whichever is lower
• Hypersensitivity to any of the study medications
• Untreated psychiatric conditions preventing informed consent