This phase I trial is evaluating a new intravenous drug (BTRC4017A) in patients with locally advanced or metastatic HER2-expressing cancersA Phase I, Open-Label, Dose-Escalation Study of the Safety and Pharmacokinetics of BTRC4017A Administered Intravenously in Patients With Locally Advanced or Metastatic HER2-Expressing Cancers

Inclusion

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
• Life expectancy of at least 12 weeks
• Adequate hematologic and end-organ function
• Acute, clinically significant treatment-related toxicity from prior therapy must have resolved to Grade </=1 prior to study entry
• Left Ventricular Ejection Fraction (LVEF) >/=50%

HER2-Expressing Breast Cancer-Specific Inclusion Criteria

• Locally tested, Human Epidermal Growth Factor Receptor 2 (HER2)-expressing BC
• Locally advanced or metastatic BC that has relapsed or is refractory to established therapies

HER2-Expressing Gastric/Gastroesophageal (GEJ) Cancer-Specific Inclusion Criteria

• Adenocarcinoma of the stomach or GEJ with inoperable locally advanced or recurrent and/or metastatic disease, not amenable to curative therapy
• HER2-expressing tumor (primary tumor or metastasis) as assessed by local lab testing
• HER2-positive gastric/GEJ cancer must have received prior trastuzumab, cisplatin (or carboplatin or oxaliplatin or investigational platinum agent) and 5-fluorouracil (5-FU)/capecitabine

HER2-Positive Solid Tumor Specific Inclusion Criteria

• HER2-positive tumor (primary tumor or metastasis) as assessed by local (non-central) laboratory testing
• Locally advanced, recurrent, or metastatic incurable malignancy that has progressed after at least one available standard therapy; or for whom standard therapy has proven to be ineffective or intolerable, or is considered inappropriate; or for whom a clinical trial of an investigational agent is a recognized standard of care; or for whom a clinical trial of an investigational agent is considered an acceptable treatment option