Participants assessed their pelvic pain not related to menses and its impact on their daily activities at approximately the same time each day they were not having their period in an e-Diary according to the following response options:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean non-menstrual pelvic pain score is the average of the daily values reported during the 4 weeks prior to each visit, except for the week 30 value which is based on 6 weeks of data.

Participants assessed dysmenorrhea or non-menstrual pelvic pain at approximately the same time each day in an e-Diary according to the following:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean cumulative pain score is the average of the daily values for all days (menstrual and non-menstrual) reported during the 4 weeks prior to each visit.

Participants assessed dysmenorrhea or non-menstrual pelvic pain at approximately the same time each day in an e-Diary according to the following:

• 0: No discomfort
• 1: Mild discomfort, I was easily able to do the things I usually do
• 2: Moderate discomfort or pain making it difficult to do some of the things I usually do
• 3: Severe pain making it difficult to do the things I usually do

The monthly mean cumulative pain score is the average of the daily values for all days (menstrual and non-menstrual) reported during the 4 weeks prior to each visit, except for the week 30 value which is based on 6 weeks of data.

Participants assessed their dyspareunia (pain during sexual intercourse) at approximately the same time every day in an e-Diary according to the following response options:

• 0 = Absent; No discomfort during sexual intercourse
• 1 = Mild; I was able to tolerate the discomfort during sexual intercourse
• 2 = Moderate; Intercourse was interrupted due to pain
• 3 = Severe; I avoided intercourse because of pain
• Does not apply; I was not sexually active for reasons other than my endometriosis or did not have sexual intercourse

The monthly mean dyspareunia score is the average of the daily values reported during the 4 weeks prior to each visit. Responses of "does not apply" were not included in the calculations.

Participants assessed their dyspareunia (pain during sexual intercourse) at approximately the same time every day in an e-Diary according to the following response options:

• 0: Absent; No discomfort during sexual intercourse
• 1: Mild; I was able to tolerate the discomfort during sexual intercourse
• 2: Moderate; Intercourse was interrupted due to pain
• 3: Severe; I avoided intercourse because of pain
• Does not apply; I was not sexually active for reasons other than my endometriosis or did not have sexual intercourse

The monthly mean dyspareunia score is the average of the daily values reported during the 4 weeks prior to each visit, except for week 30 which is based on 6 weeks of data. Responses of "does not apply" were not included in the calculations.

Participants assessed their pelvic pain not related to menses and its impact on their daily activities at approximately the same time each day they were not having their period in an e-Diary according to the following response options:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean non-menstrual pelvic pain score is the average of the daily values reported during the 4 weeks prior to each time point.

Response is defined as the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

Participants assessed dysmenorrhea or non-menstrual pelvic pain at approximately the same time every day in an e-Diary according to the following:

• 0 = No discomfort
• 1 = Mild discomfort
• 2 = Moderate discomfort or pain
• 3 = Severe pain

The monthly mean cumulative pain score is the average of the daily values for all days (menstrual and non-menstrual) in the 4 weeks prior to each time point.

Response is the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

Participants assessed their dyspareunia (pain during sexual intercourse) at approximately the same time every day in an e-Diary according to the following response options:

• 0 = Absent; No discomfort during sexual intercourse
• 1 = Mild; I was able to tolerate the discomfort during sexual intercourse
• 2 = Moderate; Intercourse was interrupted due to pain
• 3 = Severe; I avoided intercourse because of pain
• Does not apply; I was not sexually active for reasons other than my endometriosis or did not have sexual intercourse

The monthly mean dyspareunia score is the average of the daily values reported during the 4 weeks prior to each time point.

Response is defined as the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of any analgesic use is defined as the number of days in the 4 weeks prior to each study visit that the participant reported the use of an analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of any analgesic use is defined as the number of days in the 4 weeks prior to each study visit (except for week 30 which is based on 6 weeks of data) that the participant reported the use of an analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of prescription analgesic use is defined as the number of days in the 4 weeks prior to each study visit that the participant reported the use of a prescription analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of prescription analgesic use is defined as the number of days in the 4 weeks prior to each study visit (except for week 30 which is based on 6 weeks of data) that the participant reported the use of a prescription analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of narcotic analgesic use is defined as the number of days in the 4 weeks prior to each study visit that the participant reported the use of a narcotic analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of narcotic analgesic use is defined as the number of days in the 4 weeks prior to each study visit (except for week 30 which is based on 6 weeks of data) that the participant reported the use of a narcotic analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

The CPSSS consists of 5 components that address dysmenorrhea, dyspareunia, non-menstrual pelvic pain, pelvic tenderness, and pelvic induration. Each component was scored on a scale of 0 to 3 (0 = absent, 1 = mild, 2 = moderate, and 3 = severe).

Dysmenorrhea, dyspareunia, and non-menstrual pelvic pain scores are based on the participant's assessment of symptoms during the past 28 days; pelvic tenderness and induration were assessed by the investigator based on findings associated with a pelvic examination.

The total CPSSS has a maximum possible value of 15 (total score range: 0 to 15, where a lower score indicates less signs and symptoms of endometriosis or better functioning). Individual component scores range from 0 (absent) to 3 (severe).

The CPSSS consists of 5 components that address dysmenorrhea, dyspareunia, non-menstrual pelvic pain, pelvic tenderness, and pelvic induration. Each component was scored on a scale of 0 to 3 (0 = absent, 1 = mild, 2 = moderate, and 3 = severe).

Dysmenorrhea, dyspareunia, and non-menstrual pelvic pain scores are based on the participant's assessment of symptoms during the past 28 days; pelvic tenderness and induration were assessed by the investigator based on findings associated with a pelvic examination.

The total CPSSS has a maximum possible value of 15 (total score range: 0 to 15, where a lower score indicates less signs and symptoms of endometriosis or better functioning). Individual component scores range from 0 (absent) to 3 (severe).

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

The EHP-5 is an instrument to measure health-related quality of life in women with endometriosis. The EHP-5 consists of two parts:

• A core questionnaire consisting of five questions that measure the impact of endometriosis in areas of pain, control and powerlessness, emotional well-being, social support, and self-image with five response categories for each item (Never, Rarely, Sometimes, Often, Always)
• A supplemental questionnaire consisting of six additional questions which assess the impact of endometriosis on the areas of work, relationship with children, sexual intercourse, feelings about the medical profession, treatment, and infertility with the same five response categories plus an additional response category of Not Relevant which was not scored.

The scores associated with each possible outcome category are as follows: never (0), rarely (25), sometimes (50), often (75), and always (100). A negative change from baseline score indicates improvement in quality of life.

The EHP-5 is an instrument to measure health-related quality of life in women with endometriosis. The EHP-5 consists of two parts:

• A core questionnaire consisting of five questions that measure the impact of endometriosis on areas of pain, control and powerlessness, emotional well-being, social support, and self-image with five response categories for each item (Never, Rarely, Sometimes, Often, Always)
• A supplemental questionnaire consisting of six additional questions which assess the impact of endometriosis on areas of work, relationship with children, sexual intercourse, feelings about the medical profession, treatment, and infertility with the same five response categories plus an additional response category of Not Relevant which was not scored.

The scores associated with each possible outcome category are as follows: never (0), rarely (25), sometimes (50), often (75), and always (100). A negative change from baseline score indicates improvement in quality of life.

Uterine bleeding was reported daily by participants during the study using the e-Diary.

The percentage of days a participant reported any bleeding was calculated as the total number of days the participant reported any bleeding ( light, moderate, or heavy) divided by the total number of days the participant had a non-missing e-Diary report of vaginal bleeding in the phase.

Defined as the number of days from the last dose of study drug until the start date of the first post-treatment menses.

Total of all reporting groups

Participants received 150 mg elagolix orally once a day for 8 weeks during the double-blind treatment period and continued to receive 150 mg elagolix for 16 additional weeks during the open-label treatment period.

Participants assessed dysmenorrhea (pain during menstruation) and its impact on their daily activities at approximately the same time each day of their period in an electronic diary (e-Diary) according to the following response options:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean dysmenorrhea score is the average of the daily values reported during the 4 weeks prior to each visit, except for the week 30 value which is based on 6 weeks of data.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

Participants assessed their pelvic pain not related to menses and its impact on their daily activities at approximately the same time each day they were not having their period in an e-Diary according to the following response options:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean non-menstrual pelvic pain score is the average of the daily values reported during the 4 weeks prior to each visit.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

Participants assessed their pelvic pain not related to menses and its impact on their daily activities at approximately the same time each day they were not having their period in an e-Diary according to the following response options:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean non-menstrual pelvic pain score is the average of the daily values reported during the 4 weeks prior to each visit, except for the week 30 value which is based on 6 weeks of data.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

Participants assessed dysmenorrhea or non-menstrual pelvic pain at approximately the same time each day in an e-Diary according to the following:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean cumulative pain score is the average of the daily values for all days (menstrual and non-menstrual) reported during the 4 weeks prior to each visit.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

Participants assessed dysmenorrhea or non-menstrual pelvic pain at approximately the same time each day in an e-Diary according to the following:

• 0: No discomfort
• 1: Mild discomfort, I was easily able to do the things I usually do
• 2: Moderate discomfort or pain making it difficult to do some of the things I usually do
• 3: Severe pain making it difficult to do the things I usually do

The monthly mean cumulative pain score is the average of the daily values for all days (menstrual and non-menstrual) reported during the 4 weeks prior to each visit, except for the week 30 value which is based on 6 weeks of data.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

Participants assessed their dyspareunia (pain during sexual intercourse) at approximately the same time every day in an e-Diary according to the following response options:

• 0 = Absent; No discomfort during sexual intercourse
• 1 = Mild; I was able to tolerate the discomfort during sexual intercourse
• 2 = Moderate; Intercourse was interrupted due to pain
• 3 = Severe; I avoided intercourse because of pain
• Does not apply; I was not sexually active for reasons other than my endometriosis or did not have sexual intercourse

The monthly mean dyspareunia score is the average of the daily values reported during the 4 weeks prior to each visit. Responses of "does not apply" were not included in the calculations.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with non-missing data at each time point. If a participant's responses were all "does not apply" for that month the score was treated as missing.

Participants assessed their dyspareunia (pain during sexual intercourse) at approximately the same time every day in an e-Diary according to the following response options:

• 0: Absent; No discomfort during sexual intercourse
• 1: Mild; I was able to tolerate the discomfort during sexual intercourse
• 2: Moderate; Intercourse was interrupted due to pain
• 3: Severe; I avoided intercourse because of pain
• Does not apply; I was not sexually active for reasons other than my endometriosis or did not have sexual intercourse

The monthly mean dyspareunia score is the average of the daily values reported during the 4 weeks prior to each visit, except for week 30 which is based on 6 weeks of data. Responses of "does not apply" were not included in the calculations.

Randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12 and non-missing data at each time point. If a participant's responses were all "does not apply" for that month the score was treated as missing.

Participants assessed dysmenorrhea (pain during menstruation) and its impact on their daily activities at approximately the same time each day of their period in an e-Diary according to the following response options:

• 0: No discomfort
• 1: Mild discomfort but I was easily able to do the things I usually do
• 2: Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3: Severe pain that made it difficult to do the things I usually do.

The monthly mean dysmenorrhea score is the average of the daily values reported during the 4 weeks prior to each time point.

Response was defined as the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with non-missing data at baseline and week 8.

Participants assessed their pelvic pain not related to menses and its impact on their daily activities at approximately the same time each day they were not having their period in an e-Diary according to the following response options:

• 0 = No discomfort
• 1 = Mild discomfort but I was easily able to do the things I usually do
• 2 = Moderate discomfort or pain that made it difficult to do some of the things I usually do
• 3 = Severe pain that made it difficult to do the things I usually do.

The monthly mean non-menstrual pelvic pain score is the average of the daily values reported during the 4 weeks prior to each time point.

Response is defined as the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with non-missing data at baseline and week 8.

Participants assessed dysmenorrhea or non-menstrual pelvic pain at approximately the same time every day in an e-Diary according to the following:

• 0 = No discomfort
• 1 = Mild discomfort
• 2 = Moderate discomfort or pain
• 3 = Severe pain

The monthly mean cumulative pain score is the average of the daily values for all days (menstrual and non-menstrual) in the 4 weeks prior to each time point.

Response is the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with non-missing data at baseline and week 8.

Participants assessed their dyspareunia (pain during sexual intercourse) at approximately the same time every day in an e-Diary according to the following response options:

• 0 = Absent; No discomfort during sexual intercourse
• 1 = Mild; I was able to tolerate the discomfort during sexual intercourse
• 2 = Moderate; Intercourse was interrupted due to pain
• 3 = Severe; I avoided intercourse because of pain
• Does not apply; I was not sexually active for reasons other than my endometriosis or did not have sexual intercourse

The monthly mean dyspareunia score is the average of the daily values reported during the 4 weeks prior to each time point.

Response is defined as the percentage of participants with a percent decrease from baseline in the week 8 monthly mean score that was greater than or equal to each specified threshold value (10% through 90% in steps of 10%).

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with non-missing data at baseline and week 8. If a participant's responses were all "does not apply" for that month the score was treated as missing.

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of any analgesic use is defined as the number of days in the 4 weeks prior to each study visit that the participant reported the use of an analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of any analgesic use is defined as the number of days in the 4 weeks prior to each study visit (except for week 30 which is based on 6 weeks of data) that the participant reported the use of an analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of prescription analgesic use is defined as the number of days in the 4 weeks prior to each study visit that the participant reported the use of a prescription analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of prescription analgesic use is defined as the number of days in the 4 weeks prior to each study visit (except for week 30 which is based on 6 weeks of data) that the participant reported the use of a prescription analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of narcotic analgesic use is defined as the number of days in the 4 weeks prior to each study visit that the participant reported the use of a narcotic analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

The daily use of endometriosis analgesics was reported by participants daily using the e-Diary. Participants reported whether the medication was over-the-counter (OTC) or prescription, and, if prescription, whether the medication was a narcotic.

The percentage of days of narcotic analgesic use is defined as the number of days in the 4 weeks prior to each study visit (except for week 30 which is based on 6 weeks of data) that the participant reported the use of a narcotic analgesic, divided by the number of study days in the interval that the participant provided an e-Diary report regarding the use of endometriosis analgesics (including a response of "none").

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

The CPSSS consists of 5 components that address dysmenorrhea, dyspareunia, non-menstrual pelvic pain, pelvic tenderness, and pelvic induration. Each component was scored on a scale of 0 to 3 (0 = absent, 1 = mild, 2 = moderate, and 3 = severe).

Dysmenorrhea, dyspareunia, and non-menstrual pelvic pain scores are based on the participant's assessment of symptoms during the past 28 days; pelvic tenderness and induration were assessed by the investigator based on findings associated with a pelvic examination.

The total CPSSS has a maximum possible value of 15 (total score range: 0 to 15, where a lower score indicates less signs and symptoms of endometriosis or better functioning). Individual component scores range from 0 (absent) to 3 (severe).

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at baseline and week 8.

The CPSSS consists of 5 components that address dysmenorrhea, dyspareunia, non-menstrual pelvic pain, pelvic tenderness, and pelvic induration. Each component was scored on a scale of 0 to 3 (0 = absent, 1 = mild, 2 = moderate, and 3 = severe).

Dysmenorrhea, dyspareunia, and non-menstrual pelvic pain scores are based on the participant's assessment of symptoms during the past 28 days; pelvic tenderness and induration were assessed by the investigator based on findings associated with a pelvic examination.

The total CPSSS has a maximum possible value of 15 (total score range: 0 to 15, where a lower score indicates less signs and symptoms of endometriosis or better functioning). Individual component scores range from 0 (absent) to 3 (severe).

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 24. The analysis includes participants with non-missing data for each component at baseline and week 24.

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at each time point.

The Patient Global Impression of Change (PGIC) is a questionnaire-based assessment of the change in endometriosis pain since the initiation of study drug. The participant was asked to select from one of seven response categories:

1. Very Much Improved
2. Much Improved
3. Minimally Improved
4. Not Changed
5. Minimally Worse
6. Much Worse
7. Very Much Worse

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at each time point.

The EHP-5 is an instrument to measure health-related quality of life in women with endometriosis. The EHP-5 consists of two parts:

• A core questionnaire consisting of five questions that measure the impact of endometriosis in areas of pain, control and powerlessness, emotional well-being, social support, and self-image with five response categories for each item (Never, Rarely, Sometimes, Often, Always)
• A supplemental questionnaire consisting of six additional questions which assess the impact of endometriosis on the areas of work, relationship with children, sexual intercourse, feelings about the medical profession, treatment, and infertility with the same five response categories plus an additional response category of Not Relevant which was not scored.

The scores associated with each possible outcome category are as follows: never (0), rarely (25), sometimes (50), often (75), and always (100). A negative change from baseline score indicates improvement in quality of life.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population). The analysis includes participants with non-missing data at baseline and week 8 for each question.

The EHP-5 is an instrument to measure health-related quality of life in women with endometriosis. The EHP-5 consists of two parts:

• A core questionnaire consisting of five questions that measure the impact of endometriosis on areas of pain, control and powerlessness, emotional well-being, social support, and self-image with five response categories for each item (Never, Rarely, Sometimes, Often, Always)
• A supplemental questionnaire consisting of six additional questions which assess the impact of endometriosis on areas of work, relationship with children, sexual intercourse, feelings about the medical profession, treatment, and infertility with the same five response categories plus an additional response category of Not Relevant which was not scored.

The scores associated with each possible outcome category are as follows: never (0), rarely (25), sometimes (50), often (75), and always (100). A negative change from baseline score indicates improvement in quality of life.

All randomized participants who received at least 1 dose of study drug and had at least 10 evaluable e-Diary reports during the double-blind period (intent-to-treat population) with data on or after Week 12. The analysis includes participants with non-missing data at baseline and week 24 for each question.

Uterine bleeding was reported daily by participants during the study using the e-Diary.

The percentage of days a participant reported any bleeding was calculated as the total number of days the participant reported any bleeding ( light, moderate, or heavy) divided by the total number of days the participant had a non-missing e-Diary report of vaginal bleeding in the phase.

Participants who received at least one dose of randomized, double-blind study drug (safety analysis set) with non-missing data.

Defined as the number of days from the last dose of study drug until the start date of the first post-treatment menses.

Participants who received at least one dose of randomized, double-blind study drug (safety analysis set) with non-missing post-treatment data.

Participants initially randomized to elagolix received 150 mg elagolix orally once a day for 8 weeks during the double-blind treatment period and continued to receive 150 mg elagolix for 16 additional weeks during the open-label treatment period.

Participants originally randomized to placebo were switched to receive 150 mg elagolix for 16 weeks during the open-label treatment period.