This study is an open-label, multicentric, phase IIIb study of NILOTINIB administered orally at the dose of 300 mg twice daily (total daily dose 600 mg daily) for 24 months (study core), and indefinitely if it is in the interest of the patient (the drug will be given free-of-charge after 24 months to all those patients achieving the CMR4 at 24 months and in absence of safety concerns). Nilotinib dose is increased to 400 mg BID in case of suboptimal response or failure (with the exception of patients who will fail for progression to ABP: in case of progression to ABP, the patient will not be treated with study drug and the choice of the treatment will be up to the physician).