• Difference between the 50 mg Proellex group and placebo group in the Month 4 subject diary composite pain score [ Time Frame: 4 months ] [ Designated as safety issue: No ]
  
• Difference between the 25 mg and 50 mg Proellex groups and placebo group in the Month 4 subject diary composite pain score [ Time Frame: 4 months ] [ Designated as safety issue: No ]
  

• Difference between each treatment group in the subject diary composite pain score at the monthly visits [ Time Frame: monthly ] [ Designated as safety issue: No ]
  
• Time to pain-free assessments using the composite pain score as determined by data recorded in the subject diaries [ Time Frame: days ] [ Designated as safety issue: No ]
  
• Duration of pain-free assessments using the composite pain score as determined by data recorded in the subject diaries [ Time Frame: days ] [ Designated as safety issue: No ]
  
• The number of days with pain as determined by data recorded in the subject diaries, analyzed between treatment groups at the monthly visits [ Time Frame: days ] [ Designated as safety issue: No ]
  

Inclusion Criteria:

• Premenopausal women aged 18-48 inclusive
• Endometriosis documented by laparoscopic or surgical assessment within the past ten (10) years
• Clinical symptoms of endometriosis for at least the past three (3) months
• Endometriosis symptoms
• Must be sexually active unless sexually inactive for endometriosis-related dyspareunia
• Must have a regular or steady menstrual cycle lasting from 24 to 36 days and a detectable ovulation during the baseline period using an ovulation monitoring kit (for timing of endometrial biopsy)
• Other inclusion criteria may apply

Exclusion Criteria:

• Six (6) months or more without a menstrual period, or
• Prior hysterectomy or
• Prior bilateral oophorectomy
• Diagnosis of osteopenia
• Present history or condition that causes non-endometriosis-related dyspareunia
• Presence of excessive bleeding or menorrhagia
• Abnormal screening endometrial biopsy
• Other exclusion criteria may apply