If you choose to join this study, participation will consist of 5 periods: the screening period, the observation period, the study drug period, the optional continuation period, and the follow-up period. Screening Period: This period will last about 7 days and involve a visit to our clinic for a physical exam and blood draws to confirm your eligibility to take part in the study. Observation Period: This period will involve up to 4 visits, and it will be used to establish a prospective baseline of your typical routine care. During this time period (4 to 12 weeks before your first dose of study drug), you will be treated with your normal standard of care and have some extra blood tests and questionnaires. You will not get the study drug during this period. Study Drug Period: You will get the study drug during this period. It will last about a year and involve up to 26 visits to our clinic. Continuation Period: This period is optional. During this period, you can continue to take the study drug for up to 2 more years. You will continue to come in for visits similar to during the study drug period, but the visits will be less frequent. Follow-up Period: This period will last for 4 weeks after you stop taking the study drug.