This study will evaluate the efficacy and safety of an investigational medication compared with placebo in the treatment of pain associated with endometriosis.

Inclusion Criteria:

• Menstruating female 18-50 years of age,
• Regular cycle length of 21 to 35 days with menstrual bleeding that typically lasts no more than 7 days,
• Has pain associated with endometriosis,
• Has a documented history consistent with endometriosis,

Exclusion Criteria:

• Is pregnant or lactating,
• Has a history of or has active thrombosis