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 90-day washout interval of hormonal therapies, if applicable

- Have a history of regular menstrual cycles

- Have a body mass index < 40 kg/m^2 (inclusive)

- Have documented surgical/laparoscopy diagnosis of endometriosis with 5 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.

- Have an intrauterine device (IUD). If IUD is removed and subject completes Washout
period, subject will be eligible for study participation

- AST, ALT, or total bilirubin ≥ 2.0 × upper limit of normal (ULN) above the reference
range

- Have immunosuppression due to underlying medical condition

- QTcF or 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 surgical history of hysterectomy, bilateral oophorectomy and any other recent
major surgery

- Subject is required more than 2 weeks of continuous use of prohibited long-acting
narcotic or immediate release narcotic for treatment of endometriosis-associated pain.

- Have chronic pelvic pain for nonendometriosis related causes, which require systemic
pharmaceutical chronic therapy for pain

- Have other chronic pain syndrome which require chronic analgesic or other chronic
therapy

- Have a clinically significant gynecologic condition identified on the TVU (e.g.,
complex ovarian cyst > 3 cm or simple ovarian cyst > 5 cm, clinically significant
endometrial pathology, single fibroid ≥ 4 cm or multiple (> 4) fibroids that measure ≥
2 cm or symptomatic submucosal fibroid of any size

- Have a current history of undiagnosed abnormal genital bleeding