Parts A and B will include a screening period (up to 28 days) and a 12-week treatment period. A subject with no serious adverse drug reactions and who is expected to benefit from continued treatment in the opinion of the investigator will have the opportunity to participate in the long-term extension (Part C). If the subject is not a candidate for or chooses not to participate in the long-term extension (Part C), a post-treatment period of 4 weeks will commence that concludes with an end-of-study visit.