A Phase I Study of BTRC4017A in Participants With Locally Advanced or Metastatic HER2-Expressing Cancers

Inclusion Criteria

- 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
- 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

Exclusion Criteria

- Pregnant or breastfeeding, or intending to become pregnant during the study or within
140 days after the last dose of BTRC4017A

- Significant cardiopulmonary dysfunction

- Known clinically significant liver disease

- Positive for acute or chronic Hepatitis B virus (HBV) infection

- Acute or chronic Hepatitis C virus (HCV) infection

- Human Immunodeficiency Virus (HIV) seropositivity

- Poorly controlled Type 2 diabetes mellitus

- History of ventricular dysrhythmias or risk factors for ventricular dysrhythmias

- Current treatment with medications that are well known to prolong the Q-wave/T-wave
(QT) interval

- Known clinically significant liver disease

- Primary central nervous system (CNS) malignancy, untreated CNS metastases, or active
CNS metastases (progressing or requiring corticosteroids for symptomatic control)

- Leptomeningeal disease

- Spinal cord compression that has not definitively treated with surgery and/or
radiation

- History of autoimmune disease

- Prior allogeneic stem cell or solid organ transplantation