A Study for Safety and Effectiveness of IMC-A12 by Itself or Combined With Antiestrogens to Treat Breast Cancer

Breast cancer is the most common form of malignancy affecting women worldwide, with
approximately 178,480 new cases of invasive breast cancer and 62,030 new cases of in situ
breast cancer expected in the United States (US) in 2007. Approximately 40,460 women are
expected to die of breast cancer in the coming year, making the disease the second leading
cause of cancer-related mortality among women (trailing only cancers of the lung and
bronchus). However, thanks in part to recent advances in treatment, mortality rates
associated with breast cancer have declined consistently since 1990.

Surgical resection and other treatments may particularly benefit patients whose disease is
identified prior to metastasis; the 5-year survival rate for patients diagnosed with
locoregionally advanced disease is 83%. However, women with distant metastases at diagnosis
have a much poorer outlook, with a 5-year survival rate of only 26% and a median survival of
approximately 2 years. Treatment of advanced disease may include first-line chemotherapy
utilizing an anthracycline (eg, doxorubicin or epirubicin), antibody therapy, limited
surgery, taxanes, and other cytotoxic agents. As complete responses are rare, these
treatments are not generally employed as curative but in an effort to prolong life and
provide symptom palliation.

Approximately two-thirds of all breast cancers are positive for expression of the estrogen
receptor.For patients whose tumors are positive for this receptor or the progesterone
receptor, the preferred first-line treatment comprises blockade of estradiol synthesis or
hormone receptor activity using aromatase inhibitors or antiestrogen agents. Although
endocrine therapies are useful and well-tolerated, most patients respond to this form of
treatment for about 12-18 months before developing refractory disease. New therapies able to
provide additional benefit to patients with hormone receptor-positive,
antiestrogen-refractory, advanced and metastatic breast cancer are required.

Inclusion Criteria:

- The patient has histologically or cytologically-confirmed invasive breast cancer,
which at the time of study entry is either stage III (locally advanced) disease not
amenable to curative therapy or stage IV disease. Histological confirmation of
recurrent/metastatic disease is not required if clinical evidence of stage IV disease
recurrence is available

- Tumors are positive for estrogen receptors (ER), progesterone receptors (PgR), or both
(ie, 10% or more of infiltrating cancer cells exhibit nuclear staining for ER and/or
PgR; positive biochemical test results are also acceptable)

- The patient has received prior antiestrogen therapy:

1. With at least one antiestrogen agent (with or without ovarian suppression)
administered for ≥ 3 months in the adjuvant or metastatic setting; and

2. Experienced disease progression while on or within 12 months after receiving the
last dose of endocrine therapy

- The patient is postmenopausal and/or meets at least one of the following criteria:

1. Age ≥ 18 years with an intact uterus and amenorrhea for ≥ 12 months, with
estradiol and/or follicle-stimulating hormone (FSH) values in the postmenopausal
range

2. History of bilateral oophorectomy

3. History of bilateral salpingo-oophorectomy

4. History of radiation castration and amenorrheic for ≥ 3 months

- The patient has fasting serum glucose < 120 mg/dL or below the ULN

Exclusion Criteria:

- The patient has received more than two regimens of prior chemotherapy in the
metastatic (or locally advanced and inoperable breast cancer) and adjuvant setting

- The patient has poorly controlled diabetes mellitus. Patients with a history of
diabetes mellitus are allowed to participate, provided that their blood glucose is
within normal range (fasting glucose at study entry < 120 mg/dL or below ULN) and that
they are on a stable dietary and/or therapeutic regimen for this condition

- The patient is known to be positive for infection with the human immunodeficiency
virus