This study is a multi-center, multinational, randomized, double-blind, placebo-controlled Phase II clinical trial. Study enrollment will comprise approximately 225 patients meeting study inclusion requirements. The study will be conducted at up to 80 multinational investigational sites. Eligible patients will be randomized (2:1) into one of two 6 month treatment groups. One group (approximately 150 patients) will receive R788 150 mg PO bid; the other treatment group (approximately 75 patients) will receive placebo.