The objective of this study is to determine the safety and efficacy of 3 asoprisnil doses (0.5 mg, 1.5 mg, and 5.0 mg) for 12 weeks in women with endometriosis.

Endometriosis, the presence of endometrial tissue outside the uterus, is a progressive, estrogen-dependent disease that occurs in menstruating women of reproductive age. Although all major endometriosis therapies are effective for the treatment of pain, no single treatment is superior to others in terms of efficacy. The major drawbacks of the current medical therapies are severe side effects such as hot flushes and osteoporosis. The objective of this study is to determine if a dose-response relationship exists between asoprisnil and endometriosis-associated pelvic pain and dysmenorrhea or to establish the lowest effective dose of asoprisnil in the treatment of pelvic pain and dysmenorrhea associated with endometriosis. Women with surgically confirmed endometriosis will be administered asoprisnil 0.5, 1.5, and 5 mg tablets or a placebo once daily for 3 months and efficacy will be assessed by improvement in pelvic pain, dysmenorrhea, dyspareunia, bleeding, analgesic use, global efficacy, and quality of life questionnaires. Safety will be based on assessments of the endometrium, lipid profiles, adverse events, and changes from baseline laboratory values and vital signs.

Inclusion Criteria:

• Premenopausal women (18-40 years)
• Surgically confirmed endometriosis within 3 years
• History of menstrual cycles between 21 and 35 days
• Moderate or severe pelvic pain OR moderate or severe dysmenorrhea OR moderate or severe pelvic tenderness accompanied by at least mild non-menstrual pelvic pain
• Negative pregnancy test
• Agrees to use double barrier method of contraception
• Pap smear with no evidence of malignancy or pre-malignant changes
• Ultrasound with no significant gynecological disorder.
• Otherwise in good health

Exclusion Criteria:

• Less than 3 months after having a baby or breast-feeding
• Any abnormal lab or procedure result the study-doctor considers important
• Severe reaction(s) to hormone therapy
• Anticipated need for excluded hormonal therapy or unapproved narcotics
• Current use of an IUD
• History or prolactinoma