This is a multicenter study to evaluate the efficacy and safety of 2 different doses of DR-3001. For eligible subjects the duration of the study will be approximately 20 weeks; this will consist of a 4-week screening period, a 12-week treatment period and a 4-week follow-up period. Subjects will have physical and laboratory exams, including blood draws at each scheduled visit. Subjects will be required to insert a vaginal ring (replacing it every 4 weeks) and to keep a daily record of their toilet voids (including time,type and volume) for 3 days at several specified time points.