A Clinical Study of KLH-2109 in Patients With Endometriosis

Inclusion Criteria: Premenopausal women aged 18 years or older (at the time of consent) with endometriosis who meet any of the following inclusion criteria.: * A diagnosis of endometriosis by laparotomy or laparoscopy within 5 years before the start of the screening period; * Ovarian chocolate cyst confirmed by MRI performed within 1 year before the start of the screening period or ultrasonography (transvaginal, transabdominal, or transrectal) carried out at the start of the screening period; or * Any of induration of the pouch of Douglas, limitation of uterine mobility, and pelvic tenderness based on the result of pelvic/rectal examination at the start of the screening period and a diagnosis of clinical endometriosis Exclusion Criteria: 1. Patients with undiagnosed abnormal genital bleeding 2. Patients with abnormal uterine bleeding or anovulatory bleeding judged to be severe by the principal investigator or subinvestigator 3. Patients with concomitant chronic abdominal pain not attributable to endometriosis (such as irritable bowel syndrome \[IBS\] and interstitial cystitis) 4. Patients with concomitant pelvic inflammatory disease or a history of pelvic inflammatory disease within 8 weeks before obtaining informed consent