Inclusion Criteria:

- Histological or cytological confirmation of oestrogen receptor positive (ER+) and/or
progesterone receptor positive (PgR+), human epidermal growth factor receptor 2
(HER2) negative breast cancer.

- Availability of archival tumour tissue (the tissue block or slides will be sent to
the central laboratory for analysis).

- Postmenopausal women. The investigator must confirm postmenopausal status.
Postmenopausal status is defined either by:

- Age ≥ 55 years and one year or more of amenorrhea

- Age < 55 years and one year or more of amenorrhea and postmenopausal levels of
FSH and LH per local institutional standards

- Prior hysterectomy and has postmenopausal levels of FSH and LH per local
institutional standards Surgical menopause with bilateral oophorectomy

- Disease progression following prior therapy with NSAI, defined as:

- Recurrence while on or after completion of an adjuvant treatment including
letrozole or anastrozole, or

- Progression while on or following the completion of letrozole or anastrozole
treatment for locally advanced or metastatic breast cancer

Note: Non-steroidal aromatase inhibitors (i.e. letrozole or anastrozole) do not have to be
the last treatment prior to enrollment. Other prior anticancer therapy, e.g. tamoxifen,
fulvestrant, exemestane are also allowed. Patients must have recovered to grade 1 or
better from any adverse events (except alopecia) related to previous therapy prior to
enrollment.

- Radiological evidence of recurrence or progression on last systemic therapy prior to
enrollment.

Patients must have:

- At least one lesion that can be accurately measured or

- Bone lesions: lytic or mixed (lytic + sclerotic) in the absence of measurable disease

- Adequate bone marrow and coagulation function as shown by:

- Absolute neutrophil count (ANC) ≥ 1.5 109/L

- Platelets ≥ 100 ×109/L

- Hemoglobin (Hb) ≥ 9.0 g/dL

- INR ≤ 2 .

- Adequate liver function as shown by:

- Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 ULN
(or ≤ 5 if hepatic metastases are present)

- Total serum bilirubin ≤ 1.5 × ULN (≤ 3 × ULN for patients known to have Gilbert
Syndrome)

- Adequate renal function as shown by:

- Serum creatinine ≤ 1.5 × ULN - Fasting serum cholesterol ≤ 300 mg/dl or 7.75 mmol/L
and fasting triglycerides ≤ 2.5 × ULN. In case one or both of these thresholds are
exceeded, the patient can only be included after initiation of statin therapy and
when the above mentioned values have been achieved

Exclusion Criteria:

- HER2-overexpressing patients by local laboratory testing (IHC 3+ staining or in situ
hybridization positive).

- Pre-menopausal, pregnant, lactating women.

- Known hypersensitivity to mTOR inhibitors, e.g. sirolimus (rapamycin) or to their
excipients.

- Known hypersensitivity to exemestane, to the active substance or to any of the
excipients.

- Patients with rare hereditary problems of galactose intolerance, Lapp lactase
deficiency or glucose galactose malabsorption.

- Radiotherapy within four weeks prior to enrollment except in case of localized
radiotherapy for analgesic purpose or for lytic lesions at risk of fracture which can
then be completed within two weeks prior to enrollment. Patients must have recovered
from radiotherapy toxicities prior to enrollment.

- Currently receiving hormone replacement therapy, unless discontinued prior to
enrollment.

- Patients receiving concomitant immunosuppressive agents or chronic corticosteroids
use, at the time of study entry except in cases outlined below:

Prolonged systemic corticosteroid treatment during study, except for topical applications
(e.g. rash),inhaled sprays (e.g. obstructive airways diseases), eye drops or local
injections (e.g. intra-articular) should not be given. However:

- short duration (<2 weeks) of systemic corticosteroids is allowed (e.g. chronic
obstructive pulmonary disease, anti-emetic)

- low doses of corticosteroids for brain metastasis treatment is allowed

- Patients with symptomatic visceral metastasis (e.g. significant dyspnoea related to
pulmonary lymphangitic carcinomatosis and lung metastases or clinically meaningful
symptomatic liver metastasis)

- Symptomatic brain or other CNS metastases.

- Active, bleeding diathesis, or on oral anti-vitamin K medication (except low dose
warfarin, LMWH and acetylsalicylic acid or equivalent, as long as the INR is 2.0)

- Any severe and / or uncontrolled medical conditions such as:

- Unstable angina pectoris, symptomatic congestive heart failure, myocardial
infarction ≤6 months prior to enrollment, serious uncontrolled cardiac
arrhythmia

- Uncontrolled diabetes as defined by fasting serum glucose > 1.5 × ULN

- Acute and chronic, active infectious disorders (except for Hep B and Hep C
positive patients) and nonmalignant medical illnesses that are uncontrolled or
whose control may be jeopardized by the complications of this study therapy

- Impairment of gastrointestinal function or gastrointestinal disease that may
significantly alter the absorption of study drugs (e.g., ulcerative disease,
uncontrolled nausea, vomiting, diarrhoea, malabsorption syndrome)

- Significant symptomatic deterioration of lung function. If clinically indicated,
pulmonary function tests including measures of predicted lung volumes, DLco, O2
saturation at rest on room air should be considered to exclude restrictive
pulmonary disease, pneumonitis or pulmonary infiltrates.

- Patients being treated with drugs recognized as being strong inhibitors or
inducers of the isoenzyme CYP3A (rifabutin, rifampicin, clarithromycin, ketoconazole,
itroconazole, voriconazole, ritinavir, telithromycin) within the last 5 days prior to
enrollment