A Prospective, Multicenter, Randomized, Open-label, Active-controlled, 2-parallel Group, Phase III Study to Compare Efficacy and Safety of Masitinib at 7.5 mg/kg/Day to Imatinib at 400 or 600 mg in Treatment of Patients With Gastro-intestinal Stromal Tumour in First Line Medical Treatment

Inclusion Criteria:

1. Histologically proven, metastatic or locally advanced non resectable, or recurrent
post surgery GIST

2. Naïve patient or patient previously treated with imatinib as neoadjuvant/adjuvant who
relapsed after imatinib discontinuation

3. C-Kit (CD117) positive tumours detected immuno-histochemically or PDGF positive if
c-kit negative

4. Man or woman, age >18 years

5. Man and woman of childbearing potential, (entering the study after a menstrual period
and who have a negative pregnancy test) must agree to use two methods (one for the
patient and one for the partner) of medically acceptable forms of contraception
during the study and for 3 months after the last treatment intake

6. Patient able and willing to comply with study procedures as per protocol

7. Patient able to understand, sign, and date the written voluntary informed consent
form at screening visit prior to any protocol-specific procedures

Exclusion Criteria:

1. Patient previously treated by tyrosine kinase inhibitors except imatinib in case of
inclusion criteria 2

2. Patient treated for a cancer other than GIST within 5 years before enrolment, with
the exception of basal cell carcinoma or cervical cancer in situ

3. Patient with active central nervous system (CNS) metastasis or with history of CNS
metastasis

4. Patient with grade III/IV cardiac problems as defined by the New York Heart
Association Criteria. (i.e. congestive heart failure, myocardial infarction within 6
months before baseline) Patient with any condition that the physician judges could be
detrimental to subjects participating in this study; including any clinically
important deviations from normal clinical laboratory values or concurrent medical
events Previous treatment

5. Treatment with any investigational agent within 4 weeks prior baseline

6. Treatment by imatinib as neoadjuvant/adjuvant therapy within 4 weeks prior baseline