 Following randomization, subjects will return within seven business days for a Baseline Day 1 visit, at which time study medication will be dispensed and subjects will enter a 26 week treatment phase. During the treatment phase, subjects will receive study drug once daily for 24 weeks and then taper off of study drug over the following 2 weeks by receiving study drug once every other day for one week and then every 3 days for one week. Following completion of the treatment phase, subjects will enter a 4-week off-treatment follow-up phase. 