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

The purpose of this global Phase 2 study is to determine the efficacy, safety, and tolerability of 3 dose levels of OG-6219 in pre-menopausal women between 18 and 49 years of age (inclusive), who have moderate to severe endometriosis-related pain.

This is a global multicenter, Phase 2a/b, randomized, double-blind, Placebo-controlled study to assess the efficacy, safety, and tolerability of 3 dose levels of OG-6219, in pre-menopausal women 18 to 49 years of age (inclusive), who have been surgically diagnosed with endometriosis with moderate to severe endometriosis-related pain. This study includes treatment lasting approximately 16 weeks in total and is followed by a Safety Follow-up visit.

Pre-menopausal females aged 18 to 49 years old (inclusive), who have been surgically diagnosed with endometriosis will be screened and randomly assigned to study treatment. A minimum subset of 10 participants per treatment group (including Placebo group) will be voluntarily enrolled for optional intensive PK sampling for the entire duration of the study.

Eligibility Criteria:
Inclusion Criteria:

* Pre-menopausal females of age 18 to 49 years old (inclusive) at the time of signing Informed 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 surgical procedures for treatment of endometriosis during study participation.
* Normal breast exam at V1. In participants of ≥40 years mammography or contrast-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 the present 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-related activities
* 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 requires chronic analgesic or other chronic therapy
* Undiagnosed (unexplained), abnormal vaginal bleeding not associated with endometriosis within the past 6 months before screening.
* Presence of high-risk human papillomavirus (HPV).
* Has an active sexually transmitted infection (STI) (eg, gonorrhea, chlamydia, or trichomonas).
* Intends to become pregnant or breast feed during study participation or has a known or suspected pregnancy.
* History of malignancy (except for basal cell or squamous cell skin cancer) before signing informed consent.
* History of family history of hereditary abnormal hemoglobin or an enzyme deficiency that 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 strong inhibitor or inducer of CYP3A4 within 30 days or 10 half-lives (whichever is longer) prior to the planned first day of dosing.