A Study to Investigate Efficacy and Safety of OG-6219 BID in 3 Dose Levels Compared With Placebo in Participants Aged 18 to 49 With Moderate to Severe Endometriosis-related Pain

Inclusion Criteria:

• Pre-menopausal females of age 18 to 49 years old (inclusive) at the time of signingInformed Consent (V1).

• Surgically (laparoscopy or laparotomy) diagnosed with endometriosis

• Moderate to severe endometriosis-related pelvic pain

• Regular menstrual cycles

• Is not expected to undergo a planned gynecological surgery or other surgicalprocedures for treatment of endometriosis during study participation.

• Normal breast exam at V1. In participants of ≥40 years mammography orcontrast-enhanced breast MRI performed within the last 12 months prior to Screening (V1) without clinically significant abnormal findings.

• Agree not to participate in another interventional study while participating in thepresent study.

• Able and willing to adhere to study procedures, including

• agree to use 2 forms of non-hormonal contraception throughout the study

• Must be willing and able to provide signed informed consent before any study-relatedactivities

• Has demonstrated compliance with ≥75% of eDiary entries

• Has a negative pregnancy test

Exclusion Criteria:

• Surgical history of hysterectomy and/or bilateral oophorectomy

• Chronic pelvic and/or non-pelvic pain not caused by endometriosis that requireschronic analgesic or other chronic therapy

• Undiagnosed (unexplained), abnormal vaginal bleeding not associated withendometriosis within the past 6 months before screening.

• Presence of high-risk human papillomavirus (HPV).

• Has an active sexually transmitted infection (STI) (eg, gonorrhea, chlamydia, ortrichomonas).

• Intends to become pregnant or breast feed during study participation or has a knownor suspected pregnancy.

• History of malignancy (except for basal cell or squamous cell skin cancer) beforesigning informed consent.

• History of family history of hereditary abnormal hemoglobin or an enzyme deficiencythat can result in methemoglobinemia.

• Has a medical condition associated with hemolytic anemia

• Known human immunodeficiency virus infection, and/or acute or active,recurrent/relapsing, or chronic infection (eg, hepatitis A, B, or C virus)

• Has a clinically significant abnormal ECG or QT interval prolongation

• Used any medication that is either a sensitive substrate, moderate, or stronginhibitor or inducer of CYP3A4 within 30 days or 10 half-lives (whichever is longer)prior to the planned first day of dosing.