Safety and Efficacy Study of MT-2990 in Women With Endometriosis

Inclusion Criteria: * Provide written informed consent to participate in this study * Agree to approximately 30-90 day washout interval of hormonal therapies, if applicable * Have a history of regular menstrual cycles * Have a body mass index \< 45 kg/m\^2 (inclusive) * Have documented surgical/laparoscopy diagnosis of endometriosis with 10 years * Agree to use 2 forms of nonhormonal contraception throughout the study * In the Investigator's opinion, subject is able to understand the nature of the study and any risk involved in participation, and is willing to cooperate and comply with the protocol restrictions and requirements including transvaginal ultrasound. * Have moderate to severe endometrial related pain Exclusion Criteria: * Subject is pregnant, breast feeding, or planning a pregnancy. * Subject is \< 6 months postpartum, postabortion, or post-pregnancy. * Willing to remove a hormonal intrauterine device (IUD) at least 30 days prior to screening. (Non hormonal IUDs do not have to be removed) * Aspartate aminotransferase (AST), alanine aminotransferase (ALT) , or total bilirubin ≥ 2.0 × upper limit of normal (ULN) above the reference range * Have immunosuppression due to underlying medical condition * Corrected QT interval using Fridericia's formula (QTcF) or Corrected QT interval using Bazett's formula (QTcB) ≥ 450 msec or clinically important abnormal findings on the ECG * Subject is not up-to-date on breast screening according to current guidelines. * Has a surg…