• For the extension cohort to be conducted at the IUSCCC (N=12), patients with histologically documented metastatic or unresectable breast or gastrointestinal cancer will be enrolled.

• For the expansion cohort (N=30), patients with either histologically documented metastatic or unresectable breast cancer (N=15), or histologically documented metastatic or unresectable gastrointestinal cancer (N=15) be enrolled. All patients enrolled to this cohort are required to have measurable disease. Note: Measurable disease is defined as ≥ 1 lesions that can be accurately measured in ≥ 1 dimensions as ≥ 20 mm with conventional techniques or as ≥ 10 mm with spiral CT scan.

• Patients must have received or refused first line standard systemic therapy for their metastases (if applicable) and patients with histologically confirmed pancreatic and esophageal cancers must have received no more than two prior cytotoxic chemotherapy regimens in the last two years after standard therapy. Patients with histologically confirmed breast, and gastrointestinal cancers must have received no more than three prior cytotoxic chemotherapy regimens in the last two years after standard therapy.

• Progressive disease after at least one line of standard therapy.

• Patients with pancreatic and esophageal cancers must have received no more than two prior cytotoxic chemotherapy regimens in the last two years. Patients with breast and gastrointestinal cancers must have received no more than three prior cytotoxic chemotherapy regimens in the last two years.

• Patients are required to have HER-2 (IHC 1+, 2+ and 3+) or EGFR over-expression (FISH and IHC) to be enrolled on this study.

∙ If the patient has had HER-2 expression measured prior to enrollment, the report alone will be accepted on the expansion phase of the study.

‣ If the patient has had EGFR expression measured prior to enrollment, the report alone will be accepted on the dose escalation phase of the study.

‣ If the patient has not had HER-2 or EGFR expression measured prior to enrollment on this study, it would be obligatory for the patient to have the tests performed to justify their status. HER-2 status can be performed by a variety of tests. Either IHC or FISH assay are acceptable if breast tumor tissues (previously frozen) are available. The test can be done at IUSCCC or elsewhere if the patient is from out of town.

• Patients with prior history of treated brain metastases who are off steroids and have stable metastatic brain disease for at least 3 months are eligible.

• Patients must be ambulatory with an ECOG performance status 0, 1, or 2 (appendix II).

• Patients must have adequate organ function as defined by:

∙ ANC ≥ 1,000/mm³, platelet count \> 700,000/mm³.

‣ Serum bilirubin \< 1.5 mg%, regardless of whether patients have liver involvement secondary to tumor. ALT must be \< 2 times upper limit of normal.

‣ Creatinine \<1.5 mg/dl or calculated creatinine clearance \> 60 ml/min

⁃ Patients must be at least 3 weeks past any prior surgery, cytotoxic, chemotherapy, other immunotherapy, hormonal therapy, or radiation therapy. Patients having been treated with monoclonal antibodies may enter the trial after a specified period of time (2 times the mean half life of the agent). Patients must have recovered from any toxicity of prior therapy prior to enrolling on study except for neuropathy where patients need to recover to less than grade 2.

• Patients with hormone receptor positive breast cancer who are on stable endocrine therapy are eligible if their tumor has some expression of HER-2 based on IHC of 1+ or 2+.

⁃ Patients must be at least 18 years of age.

⁃ Women of child-bearing potential must not be pregnant and must have a negative pregnancy test (Women of childbearing potential definition: (ECOG definition)).

⁃ Men and women must agree to practice effective contraception while on this study.

⁃ Patients must obtain a base line Echocardiogram or MUGA and require the left ventricular ejection fraction to be within normal limits (or 50% or higher).

⁃ Ability to understand and the willingness to sign a written informed consent document.

⁃ The patient must be aware that his/her disease is neoplastic in nature and willingly consent after being informed of the procedure to be followed, the experimental nature of the therapy, alternatives, potential benefits, side-effects, risks, and discomforts.