Phase 1/2, open-label, multi-center, trial, aiming at to identify the most efficacious dose combination that also satisfies certain safety requirements. It consists in a dose finding study to assess the safety of the combination of different doses of both ruxolitinib and peg-IFN alpha-2a, and a secondary randomized evaluation of the optimal doses found in the first part of the study to a total maximal number of 42 evaluable patients.