5. Patients may have a contra-indication to one of the study drug or have been treated prior to enrollment with one of the study medications but failed to respond to it (according to the study definitions of failure and if they have been on the drug at the target dose or higher for 3 months or longer) or had to stop it because of an adverse event. Such patients can be enrolled directly in the second stage of the study and be randomized to receive one of the two other study drugs. The number of such patients enrolled directly in stage 2 will be capped at 10 (10% of the total recruitment target).