Inclusion Criteria:

- Signed and dated informed consent form

- Women ≥ 18 years, negative pregnancy test at screening life expectancy of at least 6
months

- Locally advanced (stage IIIb) or metastatic (stage IV) and not curable adenocarcinoma
of the breast

- Measurable disease, defined as at least one lesion that is measurable in one
dimension (RECIST)

- HER-2/neu expression 1+ or 2+ / FISH negative

- Estrogen Receptors (ERs) and/or Progesterone Receptors (PRs) positive

- Prior adequate endocrine therapy for advanced or metastatic disease

- Disease progression during or after endocrine therapy

- No prior treatment with mouse or rat antibodies

- ECOG performance score of ≤ 1

- Adequate hematological, liver and kidney function

Exclusion Criteria:

- Women who are pregnant or breast-feeding

- Known HIV infection or Presence of autoimmune disease or other Concurrent
non-malignant co-morbidities that are uncontrolled

- History or symptoms indicative of brain or CNS metastases

- Prior diagnosis of any malignancy not cured by surgery alone less than 5 years before
study entry (except in situ carcinoma of the cervix or adequately treated basal cell
carcinoma of the skin)

- Documented acute or chronic infection requiring antibiotic treatment

- Any concurrent chemo-, hormonal, immuno- or corticoid therapy

- Any prior chemotherapy for advanced or metastatic disease

- Any concurrent investigational treatment for advanced or metastatic disease

- History of relevant cardiovascular disease as follows:

- Left ventricular ejection fraction (LVEF) below the institution's lower limit of
normal, based on echocardiography (ECG) at rest

- Uncontrolled or symptomatic congestive heart failure (New York Heart Association
(NYHA) > 2

- Uncontrolled or symptomatic arrhythmia and/or angina pectoris

- Myocardial infarction during the last 2 years