A Randomized, Double-Blind, Multi-Center Phase II Trial of Exemestane (Aromasin®) Plus Dasatinib Versus Exemestane Plus Placebo in Advanced Estrogen Receptor-Positive Breast Cancer After Disease Progression on a Non-Steroidal Aromatase Inhibitor (NSAI)

Inclusion Criteria:

- Histologically-documented invasive estrogen receptor positive breast cancer , with
tumor tissue from prior surgery available for analysis

- Prior therapy with a non-steroidal aromatase inhibitor

- Recurrent or progressive advanced breast cancer (locally-advanced or metastatic)

- Documented breast cancer with tumor ≤ 28 days prior to study entry

- Women who are NOT of childbearing potential

- Must be able to take oral medication

- Performance Status 0 or 1

Exclusion Criteria:

- Pleural or pericardial effusion or ascites (of any etiology; Grade ≥ 1) within 6
months prior to study entry

- Any chemotherapy, immunotherapy < 6 months before study entry. Any targeted therapy
(eg. lapatinib) < 6 months before study entry, unless given in combination with an
NSAI

- Any antitumor therapy, including radiotherapy or hormonal therapy, within 15 days
prior to study entry

- Prior exposure to exemestane, any Src-family kinase inhibitor including dasatinib, to
agents intended to control osteolytic disease other than bisphosphonates, or to any
investigational agent for breast cancer

- Concurrent or previous malignant disease requiring chemotherapy or radiation
treatment within the prior 3 years

- Significant bleeding disorder, or ongoing or recent clinically-significant
gastrointestinal bleeding

- Any serious cardiac condition, including congestive heart failure or myocardial
infarction within 6 months, uncontrolled angina, or Class III or IV heart disease as
defined by the New York Heart Association, baseline ejection fraction ≤ 40%,
diagnosed congenital long QT syndrome, clinically-significant ventricular arrhythmias
(such as ventricular tachycardia, ventricular fibrillation, or Torsades de Pointes),
QTc interval > 450 msec at baseline (Fridericia correction)

- Hematologic abnormality Grade ≥ 2

- Hypocalcemia of Grade ≥ 1

- Any Chemistry abnormality of Grade ≥ 2 [except Grade 2 indirect bilirubin permitted
if diagnosed Gilbert's disease]

- Pregnant Women and Women of Childbearing Potential (WOCBP)

- Extremely lactose intolerant, in the judgment of treating physician (100 mg dasatinib
contains 135 mg lactose, posing a problem only if intolerance is severe)

- Receiving any of the following concomitant medications: Category I drugs that are
generally accepted to have a risk of causing Torsades de Pointes including: (Subjects
must discontinue drug use at least 7 days prior to starting dasatinib)

- Potent inhibitors of CYP3A4 isoenzyme

- Prisoners or subjects who are involuntarily incarcerated; or subjects who are
compulsorily detained for treatment of either a psychiatric or physical (eg,
infectious disease) illness