 This is a Phase 2, multi-center, double-blind, randomized, placebo-controlled, dose-ranging, parallel-group study. The PK and PKPD relationship of AKR-501 will also be studied. Approximately 65 eligible patients will be randomized in a 3:3:3:3:1 ratio in a double-blinded fashion into one of five parallel treatment groups to receive daily doses of either AKR-501 2.5, 5, 10 or 20 mg or placebo for 28 days, respectively. Each AKR-501 dosing group will consist of 15 patients while the placebo group will consist of 5 patients. All study patients will be evaluated weekly Days 3, 5, 7, 14, 21 and 28 for safety, efficacy, and Days 7, 14, 21, and 28 AKR-501 pharmacokinetics while receiving study treatment with a final assessment for safety and effectiveness to be done 2 weeks after the last study dose Day 42. 