XP13512 (Gabapentin Enacarbil) Extension Study in Patients With Restless Legs Syndrome.

• Change From Baseline in the International Restless Legs Syndrome Rating Scale (IRLS) at Week 52 Using Observed Case (OC) [ Time Frame: Baseline and Week 52 ] [ Designated as safety issue: No ]
  The IRLS rating scale is a measure of RLS disease severity. The score reflects participant-reported assessment of primary sensory and motor features and associated sleep problems in RLS. Also, items are included that assess the impact of symptoms on participants' mood, daily life, and activities. The total score on the IRLS ranges from 0 to 40, with higher values representing more severe RLS symptoms. Change from baseline was calculated as the Week 52 value minus the baseline value. Change scores with higher value represents greater improvement in RLS symptoms.
  
  
• Number of Participants Classified as Responders to Treatment on the Investigator-rated Clinical Global Impressions of Improvement (CGI-I) at Each Visit Using OC [ Time Frame: Weeks 0, 1, 4, 12, 24, 36, and 52 ] [ Designated as safety issue: No ]
  The CGI-I is a widely used tool designed to allow clinicians to rate the severity of illness and the change over time based on a seven-point rating scale, with a score of 1 being "very much improved" and a score of 7 being "very much worse" compared to the start of the study. Responders on the CGI-I are defined as those with a score of 1 or 2, corresponding to "very much improved" or "improved," respectively.
  
  

• Change From Baseline in the IRLS Rating Scale Score at Each Visit Using OC [ Time Frame: Weeks 0, 1, 4, 12, 24, and 36 ] [ Designated as safety issue: No ]
  The IRLS rating scale is a measure of RLS disease severity. The score reflects participant-reported assessment of primary sensory and motor features and associated sleep problems in RLS. Also, items are included that assess the impact of symptoms on participants' mood, daily life, and activities. The total score on the IRLS ranges from 0 to 40, with higher values representing more severe RLS symptoms. Change from baseline was calculated as the value at each visit minus the baseline value. Change scores with higher values represent greater improvement in RLS symptoms.
  
  
• Number of Participants in Each Category of the Investigator-rated CGI-I by Visit Using OC [ Time Frame: Weeks 0, 1, and 52 ] [ Designated as safety issue: No ]
  The CGI-I is a widely used tool designed to allow clinicians to rate the severity of illness and the change over time based on a seven-point rating scale, with a score of 1 being "very much improved," 2 being "much improved," 3 being "minimally improved," 4 being "no change," 5 being "minimally worse," 6 being "much worse," and 7 being "very much worse" compared to the start of the study.
  
  
• Number of Participants Classified as Responders to Treatment on the Participant-rated CGI-I at Each Visit Using OC [ Time Frame: Weeks 0, 1, 4, 12, 24, 36, and 52 ] [ Designated as safety issue: No ]
  The Participant-rated CGI-I is a self-reported measure completed by the participant, who rates the change from the start of the study in the severity of their illness using a seven-point rating scale, with a score of 1 being "very much improved" and a score of 7 being "very much worse". Responders on the Participant-rated CGI-I are defined as those with a score of 1 or 2, corresponding to "very much improved" and "improved," respectively.
  
  
• Number of Participants in Each Category of the Participant-rated CGI-I by Visit Using OC [ Time Frame: Weeks 0, 1, and 52 ] [ Designated as safety issue: No ]
  The Participant-rated CGI-I is a self-reported measure completed by the participant who rates the change from the start of the study in the severity of their illness using a seven-point rating scale, with a score of 1 being "very much improved," 2 being "much improved," 3 being "minimally improved," 4 being "no change," 5 being "minimally worse," 6 being "much worse," and 7 being "very much worse" compared to the start of the study.
  
  
• Number of Participants With no Reported RLS Symptoms During Each of the 4-hour Periods From the 24-hour RLS Record at Week 52 Using OC Data [ Time Frame: Week 52 ] [ Designated as safety issue: No ]
  In the 24-Hour RLS Record (diary), participants report the presence and severity of RLS symptoms (none, mild, moderate, or severe) for a 24-hour period, in 30-minute increments. The period was divided into 7 four-hour intervals (8 AM to 12PM, 12 to 4PM, 4 to 8PM, 6 to 10PM, 8 to 12 Midnight, Midnight to 4AM, 4 to 8AM).
  
  
• Median Time to Onset of the First RLS Symptom Using the RLS Symptom Record at Weeks 24 and 52 [ Time Frame: Weeks 24 and 52 ] [ Designated as safety issue: No ]
  The 24-Hour RLS Record is a diary in which participants report the presence and severity of RLS symptoms for a 24-hour period, in 30-min increments, beginning at 8AM on the day prior to the visit.
  
  
• Overall Quality of Life (QoL) Impact Score of the RLS Quality of Life Questionnaire at Weeks 24 and 52 [ Time Frame: Weeks 24 and 52 ] [ Designated as safety issue: No ]
  The RLS QoL is an 18-item scale assessing the impact of RLS on daily life, emotional well-being, social and work life. Responses range from 1 (not at all/never) to 5 (a lot/all of the time). Ten items contribute to a single summary score, the Overall Life Impact, which is standardized to range from 0-100, with lower scores representing better QoL.
  
  
• Mean Change From Baseline at Week 24 and Week 52 in Work Productivity and Activity Impairment Questionnaire (WPAI:SHP) Summary Scores [ Time Frame: Baseline and Weeks 24 and 52 ] [ Designated as safety issue: No ]
  The WPAI:SHP estimates work productivity and social activities lost over the past week due to RLS symptoms. Each summary score is expressed as a percentage and ranges from 0 to 100, with higher scores indicating more work missed; a negative change from baseline indicates less work missed. Change = the observed value at the current visit minus the observed value at Week 0. Change is calculated only for participants who had a value at both the current visit and at Week 0.
  
  
• Mean Change From Baseline at Week 24 and Week 52 in Work Productivity and Activity Impairment Questionnaire (WPAI:SHP) Individual Items: Hours of Work Missed Due to RLS, Hours of Work Missed Due to Other Reason, and Hours Actually Worked [ Time Frame: Baseline and Weeks 24 and 52 ] [ Designated as safety issue: No ]
  The WPAI:SHP estimates work productivity and social activities lost over the past week due to RLS symptoms. Change is calculated as the observed value at Week 24/52 minus the observed value at baseline. Absenteeism is recorded as the number of hours missed from work. W, Week; hr, hour.
  
  
• Mean Change From Baseline at Weeks 24 and 52 in Work Productivity and Activity Impairment Questionnaire (WPAI:SHP) Individual Item: RLS Affected Productivity [ Time Frame: Baseline and Weeks 24 and 52 ] [ Designated as safety issue: No ]
  The WPAI:SHP estimates work productivity and social activities lost over the past week due to RLS symptoms. Change is calculated as the observed value at Week 52 minus the observed value at baseline. Productivity affected while working is estimated on a 0 (no effect) to 10 scale (completely preventing productivity).
  
  

Study XP055 is a multicenter, open-label, 52-week extension study of XP13512 (Gabapentin Enacarbil [GEn]) given once daily to eligible subjects with Restless Legs Syndrome (RLS) who had previously completed 1 of the following studies and met eligibility criteria: XP052 (110963 [NCT00298623]), XP053 (111460 [NCT00365352]), XP081 (111462 [NCT01332305]), and XP083 (111463 [NCT01332318]).