Inclusion Criteria

Inclusion criteria:

- Diagnosis of PMF or Post-PV MF or Post-ET MF, according to the 2008 World Health
Organization and IWG-MRT response criteria

- Subjects who previously received Ruxolitinib treatment for PMF or Post-PV MF or
Post-ET MF or PV or ET for at least 14 days (exposure of <14 days is allowed for
subjects who discontinued Ruxolitinib due to intolerability or allergy) and
discontinued the treatment for at least 14 days prior to the first dose of SAR302503

- MF classified as Intermediate-1 with symptoms, Intermediate-2 or high-risk by Dynamic
International Prognostic Scoring System (Passamonti et al., Blood 2010)

- Spleen ≥5 cm below costal margin as measured by palpation

- Male and female subjects ≥18 years of age

- Signed written informed consent

Exclusion criteria:

- Splenectomy

- Eastern Cooperative Oncology Group (ECOG) performance status of >2 before the first
dose of SAR302503 at Cycle 1 Day1

- The following laboratory values within 14 days prior to the initiation of SAR302503:

- Absolute Neutrophil Count (ANC) <1.0 x 10exp9/L

- Platelet count <50 x 10exp9/L

- Serum creatinine >1.5 x Upper limit of normal (ULN)

- Serum amylase and lipase >1.5 x ULN

- Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) ≥2.5 x ULN

- Total bilirubin ≥3.0 x ULN

- Subjects with total bilirubin between 1.5-3.0 x ULN must be excluded if the direct
bilirubin fraction is ≥25% of the total

- Subjects with known active (acute or chronic) Hepatitis A, B, or C; and Hepatitis B
and C carriers

- Prior history of chronic liver disease (eg, chronic alcoholic liver disease,
autoimmune hepatitis, sclerosing cholangitis, primary biliary cirrhosis,
hemachromatosis, non-alcoholic steatohepatitis [NASH])

- Subjects with any other prior malignancies are not eligible, except for the
following: adequately treated basal cell or squamous cell skin cancer, in situ
cervical cancer, or other cancer from which subject has been disease-free for at
least 5 years

- Any chemotherapy, immunomodulatory drug therapy (eg, thalidomide, interferon-alpha),
Anagrelide, immunosuppressive therapy, corticosteroids >10 mg/day prednisone or
equivalent, or growth factor treatment (eg, erythropoietin), or hormones (eg,
androgens, danazol) within 14 days prior to initiation of SAR302503; darbepoetin use
within 28 days prior to initiation of SAR302503.The only chemotherapy allowed will be
hydroxyurea within 1 day prior to initiation of SAR302503

- Uncontrolled congestive heart failure (New York Heart Association Classification 3 or
4), angina, myocardial infarction, cerebrovascular accident, coronary/peripheral
artery bypass graft surgery, transient ischemic attack, or pulmonary embolism within
3 months prior to initiation of SAR302503

The above information is not intended to contain all considerations relevant to a
patient's potential participation in a clinical trial.