Safety and Efficacy of Telapristone Acetate (Proellex®) in the Treatment of Pre-Menopausal Women With Confirmed, Symptomatic Endometriosis

This study is a phase 2, 3-arm-study with an 18-week active dosing period and an option for participants to receive 2 additional 16-week cycles of active treatment at their randomized dose \[6 mg or 12 mg/day\]. Placebo participants who elect additional treatment will receive treatment at 12 mg/day. The treatment dose will remain double-blind. The study will be conducted in 3 stages. The first stage is a no treatment baseline assessment period. This stage will last as long as it takes to record at least one full menstrual cycle (ovulation until ovulation). For stage 2, following the run-in stage, at Visit 3, 60 participants will be randomized into one of 3 arms in a 1-1-1 fashion. The start of dosing should commence as soon as possible after ovulation following the end of the previous menstrual event. For stage 3, participants who are eligible to receive additional cycles of treatment and who elect to continue treatment will be scheduled within a week before the second expected menses (+/- 2 days), following the off-drug interval. Participants will receive 2 cycles of treatment separated by an off-drug interval (ODI), after which they will be followed until menses has returned.