Baseline and EOMT values are the calculated means of the daily 24-hour API scores for each participant during the last 7 days prior to randomization (Baseline) and the earliest date of Week 13 visit/Withdrawal visit/last dose of study drug (EOMT). Participants used a hand-held diary to rate their average pain intensity over the preceding 24 hours, using an 11-point PI-Numerical Rating Scale (0=no pain, 10=pain as bad as you can imagine). LOCF was used if less than 4 days of diary data were provided. Change from baseline was calculated as EOMT score minus Baseline score.

ITT Population: all randomized participants who took at least one dose of investigational product and provided at least one post-baseline efficacy measurement.

Night-time is defined as the time between going to bed at night and rising in the morning. Participants recorded night-time API on a daily basis in the morning upon awakening using an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline wss calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 2400 mg group and one in the 3600 mg group who did not complete enough post-baseline morning diaries to calculate an API for the EOMT timepoint.

Current pain is defined as the participant's assessment of pain intensity "right now." Participants recorded their current morning pain intensity in the morning upon wakening using an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 2400 mg group and one in the 3600 mg group who did not complete enough post-baseline morning diaries to calculate an API for the EMOT timepoint.

Night-time worst pain is defined as the participant's assessment of their worst pain between going to bed at night and rising in the morning. Participants recorded night-time worst pain in the morning upon awakening using an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 2400 mg group and one in the 3600 mg group who did not complete enough post-baseline morning diaries to calculate an API for the EMOT timepoint.

Participants assessed sleep interference due to pain on a daily basis using the 11-point NRS (0=pain does not interfere with sleep, 10=pain completely interferes with sleep). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 2400 mg group and one in the 3600 mg group who did not complete enough post-baseline morning diaries to calculate a score for the EMOT timepoint.

Day-time is defined as the time between rising in the morning and going to bed at night. Participants recorded day-time API on a daily basis in the evening before bedtime using an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 1200 mg group and two in the 2400 mg group who did not complete enough post-baseline evening diaries to calculate an API for the EOMT timepoint.

Current pain is defined as the participant's assessment of pain intensity "right now." Participants recorded their current evening pain intensity in the evening before bedtime using an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 1200 mg group and two in the 2400 mg group who did not complete enough post-baseline evening diaries to calculate a score for the EMOT timepoint.

Day-time worst pain is defined as the participant's assessment of their worst pain between rising in the morning and going to bed at night. Participants recorded day-time worst pain in the evening before bedtime using an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 1220 mg group and two in the 2400 mg group who did not complete enough post-baseline evening diaries to calculate a score for the EOMT timepoint.

The NPS assesses pain qualities and consists of 11-items, 10 assessed on an 11-point NRS (0=no impact to 10=greatest impact); and 1 open-ended question not used in score calculation. 4 summary scores are calculated: NPS 10 (items 1-7, 9-11), NPS 8 (8 pain descriptor items), NPS Non-Allodynic (NA) (8 NA items), and NPS 4 (4 pain quality items); and range from 0 to 100 (0=no impact and 100=greatest impact). The analysis is based on the change from baseline (BL) (EOMT score minus the BL score) using an ANCOVA model with BL value, BMI, grouped center as covariates.

ITT Population. The NPS summary included a subset of the ITT Population that completed an NPS assessment at both Baseline and Week 13/Withdrawal.

The SF-MPQ, a general pain instrument, assesses the characteristics and intensity of pain and consists of 15-items assessed on a 4-point scale (0=none, 1=mild, 2=moderate, and 3=severe). 3 summary scores are calculated: sensory score (sum of items 1-11, range 0-33), affective score (sum of items 12-15, range 0-12), total score (sum of items 1-15, range 0-45), where lower scores = lower pain/impact. Analysis is based on the change from baseline (BL) (EOMT score minus the BL score) using an ANCOVA model with BL value, BMI, grouped center as covariates.

ITT Population. The SF-MPQ analysis included a subset of the ITT Population who completed a SF-MPQ assessment at both Baseline and the Week 13/Withdrawal Visit.

Dynamic allodynia (pain in response to a standardized light touch stimulus, a foam brush applied with light pressure to the site of maximum pain) was assessed by an 11-point PI-NRS (0=no pain, 10=pain as bad as you can imagine). Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. The NRS analysis included a subset of the ITT Population who completed that NRS at both the Baseline and the Week13/Withdrawal Visit.

The PGIC is a single-item questionnaire designed to provide an overall assessment of treatment from the participant's perspective since the start of the study. It is measured on a 7-point scale, where 1=very much improved and 7=very much worse. A participant is considered a responder if they have a response of "very much improved" or "much improved." EOMT response is defined as the score recorded at the Week13/Withdrawal visit.

ITT Population. The PGIC analysis included a subset of the ITT Population who completed the PGIC questionnaire at the end of treatment.

Baseline and EOMT scores are the calculated means of the 24-hour average pain scores for each participant during the last 7 days prior to randomization and EOMT, respectively. Percent reduction from baseline was calculated as the [(EOMT score minus the baseline score)divided by the baseline score], multiplied by 100. The PI-NRS is an 11-point scale (0=no pain, 10=pain as bad as you can imagine) by which a participant assesses their 24-hour average pain intensity.

ITT Population. There was one participant in the GEn 1200 mg and one in the GEn 2400 mg group who did not have enough data available to calculate the percent reduction.

Sustained improvement in the 24-hour average pain intensity score is defined as at least 2 consecutive days on which the 24-hour average pain intensity score is >=2 points less than the mean 24-hour average pain intensity score at baseline. Time to onset is measured from baseline and was calculated as the first day of event minus the last day of baseline and is expressed in days. Baseline score is the calculated mean of the 24-hour average pain score for each participant during the last 7 days prior to randomization.

ITT Population

Mean daily use of rescue medication (milligrams of acetaminophen) was calculated by determining the average number of tablets taken per day of rescue medication (Commerical Tylenol) during treatment and multiplying that by 500 mg. Baseline and EOMT are as defined for the primary endpoint. Change from baseline was calculated as the EOMT score minus the baseline score. An ANCOVA model with baseline value, BMI, grouped center as covariates was used.

ITT Population. There was one participant in the GEn 1200 mg and two in the GEn 2400 mg group who did not have enough data available to calculate the rescue mediation consumed while on treatment.

The BPI, a general pain instrument, assesses the severity and interference of pain; and consists of 6 items assessed on an 11-point NRS (0=no impact and 10=greatest impact). 2 summary scores are calculated: BPI Severity Score (average of first 4 items) and BPI Interference Score (average of 7 responses to item 6); where each summary score ranges from 0 to 10 (0=no impact and 10=greatest impact). Analysis of this endpoint is based on the change from baseline (BL) (EOMT score minus the BL score) using an ANCOVA model with BL value, BMI, grouped center as covariates.

ITT Population. Not all participants completed a BPI assessment at both Baseline and Week 13/Withdrawal; as such, the number analyzed is different from the full ITT Population counts.

The SF-36 is a general health-related quality of life instrument consisting of 36 items with various response options (Yes/No, 5- to 6-point Likert scale). Summary scores are calculated for 8 domains and 2 components (physical and mental); where scores range from 0 to 100 (higher scores = better quality of life). Analysis of this endpoint is based on the change from baseline (BL) (EOMT score minus the BL score) using an ANCOVA model with BL value, BMI, grouped center as covariates.

ITT Population. Not all participants completed an SF-36 at both Baseline and Week 13/Withdrawal; as such, the number analyzed is different from the full ITT Population counts.

The POMS-B, an emotional functioning instrument, assesses mood, tension, and other psychological symptoms and consists of 30-items assessed on a 5-point scale (0=not at all to 4=extremely). 6 summary scores are calculated: Tension/Anxiety, Depression/Rejection, Anger/Hostility, Vigor/Activity, Fatigue/Inertia, and Confusion/Bewilderment; and range from 0-20 (higher scores = more negative mood state). Analysis of this endpoint is based on the change from baseline (BL) (EOMT score minus the BL score) using an ANCOVA model with BL value, BMI, grouped center as covariates.

ITT Population. Not all participants completed a POMS-B at both Baseline and Week 13/Withdrawal; as such, the number analyzed is different from the full ITT Population counts.

The CGIC is a single-item questionnaire designed to provide an overall assessment of treatment from the clinician's perspective since the start of the study. It is measured on a 7-point scale, where 1=very much improved and 7=very much worse. A participant is considered a responder if they have a response of "very much improved" or "much improved." EOMT response is defined as the score recorded at the Week13/Withdrawal visit.

ITT Population. The CGIC analysis included a subset of the ITT Population who completed the PGIC questionnaire at the end of treatment.