Clinical trial NCT01668667: Gabapentin Enacarbil (GSK1838262) Adult Restless Leg Syndrome (RLS) Post Marketing Commitment Study
Official title: Randomized, Double-Blind, Placebo-Controlled, Fixed-Dose, Parallel-Group Study to Compare the Efficacy, Tolerability, and Safety of 3 Doses of Gabapentin Enacarbil (GSK1838262) With Placebo in Treatment of Moderate-to-Severe Primary RLS
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: PHASE4
Conditions: Restless Legs Syndrome
Keywords: gabapentin enacarbil
Horizant
Lead sponsor: XenoPort, Inc.
Sponsor class: INDUSTRY
First posted: 2012-08-20
Enrollment: 501
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: Gabapentin enacarbil (GEn; GSK1838262; HORIZANT), at a dose of 600 mg/day, is currently approved in the United States for the treatment of adults with moderate-to-severe primary Restless Legs Syndrome (RLS). The aim of this study is to compare the efficacy, tolerability, and safety of GEn at lower doses (450 and 300 mg/day) as well as the already approved dose of 600 mg/day versus placebo for the treatment of subjects with moderate to severe primary RLS. This study is being conducted as a post-marketing commitment (PMC) as a condition of the approval of HORIZANT tablets (NDA 022399).

Detailed description: This is a Phase IV randomized, double-blind, placebo-controlled, fixed-dose, parallel group study to assess the efficacy, tolerability, and safety of 3 doses of GEn (600, 450, and 300 mg/day) compared with placebo in the treatment of subjects with moderate-to-severe primary RLS.

The study will include 9 visits over approximately 14 weeks for eligible subjects including a 1-week Screening Period, a 12-week Treatment Period, and a 1 week Follow up Period. Screening will occur within 1 week of the first scheduled dose of study medication. The total duration of the study, from the first subject enrolled to the last subject completed will be approximately 2 years.

Eligible subjects (at least 18 years of age) must have:

* a diagnosis of RLS according to the IRLSSG Diagnostic Criteria
* a history of RLS symptoms for at least 15 nights in the prior month or, if on treatment, this frequency of symptoms before treatment was started
* documented RLS symptoms for at least 4 of the 7 consecutive evenings/nights during the Screening Period, and a total RLS severity score of at least 15 on the International Restless Legs Syndrome (IRLS) Rating Scale at the screening and baseline visits

Approximately 498 subjects will be enrolled, randomly assigned to treatment groups, and receive study medication once daily for 12 weeks. Subjects will be randomly assigned to receive 1 of the 4 following treatment groups in a ratio of 1:1:1:1:

* GEn 600 mg/day
* GEn 450 mg/day
* GEn 300 mg/day
* Matching placebo

Subjects will be instructed to take their study medication once daily with food in the evening at approximately 5 PM. Each tablet must be swallowed whole and not divided, crushed, or chewed.

Each subject, regardless of treatment assignment, will take 3 tablets of study medication (1 tablet from Bottle A, 1 tablet from Bottle B, and 1 tablet from Bottle C) once daily continuing through the end of the Treatment Period (Week 12). Subjects will return to the study site for a follow-up visit (Visit 9, Week 13) approximately 1 week after the last dose of study medication.

Each subject's participation in the study will be approximately 14 weeks unless they withdraw early from the study. For subjects who complete the study, Visit 9 (which can occur between Day 86 and 92) will be considered their end-of-study visit.

Eligibility criteria: Inclusion Criteria:

* Men or women 18 years of age or older
* History of RLS symptoms for at least 15 nights/month
* Documented RLS symptoms, using the 7-day RLS Symptom Record, for at least 4 of the 7 consecutive evenings/nights during the night
* Total RLS severity score of 15 or greater on the International RLS (IRLS) Rating Scale at Visit 1 and at Visit 2
* Discontinuation of dopamine agonists and/or gabapentin , or other treatments for RLS (e.g. opioids, benzodiazepines) at least 2 weeks prior to Baseline
* If taking any prescription medication, therapy must have been stabilized for at least 3 months prior to Screening with no anticipated changes for the duration of the study
* Female subjects are eligible if of non-childbearing potential or not lactating, has a negative pregnancy, and agrees to use a highly effective method for avoiding pregnancy
* Body mass index of 34 or below
* Estimated creatinine clearance of ≥60 mL/min
* Provides written consent in accordance with all applicable regulatory requirements

Exclusion Criteria:

* History of a sleep disorder that may affect the assessment of RLS
* History of RLS symptom augmentation or end-of-dose rebound with previous dopamine agonist treatment
* Neurologic disease or movement disorder
* Other medical conditions or drug therapy that could affect RLS efficacy assessments or may present a safety concern
* Have clinically significant or unstable medical conditions
* Have active suicidal plan/intent or has had active suicidal thoughts in the past 6 months; has a history of suicide attempt

Primary outcomes:
measure: The Change From Baseline to the End of Treatment in the International Restless Legs Syndrome (IRLS) Rating Scale Score
timeFrame: Baseline, 12 weeks
measure: The Proportion of Subjects at the End of Treatment Who Are Responders With Either "Much Improved" or "Very Much Improved" on the Investigator-rated Clinical Global Impression of Improvement (CGI-I)
timeFrame: 12 weeks
Secondary outcomes:
measure: The Dose-response Relationship of Change From Baseline in IRLS Rating Scale Total Score at End of Treatment
timeFrame: Baseline, 12 Weeks
measure: The Dose-response Relationship for Investigator-rated CGI-I Scale at End of Treatment
timeFrame: 12 Weeks
Other outcomes:
Locations:
city: Phoenix
country: United States
facility: GSK Investigational Site
state: Arizona
city: Phoenix
country: United States
facility: GSK Investigational Site
state: Arizona
city: Tucson
country: United States
facility: GSK Investigational Site
state: Arizona
city: Little Rock
country: United States
facility: GSK Investigational Site
state: Arkansas
city: Santa Monica
country: United States
facility: GSK Investigational Site
state: California
city: Colorado Springs
country: United States
facility: GSK Investigational Site
state: Colorado
city: Denver
country: United States
facility: GSK Investigational Site
state: Colorado
city: DeLand
country: United States
facility: GSK Investigational Site
state: Florida
city: Tampa
country: United States
facility: GSK Investigational Site
state: Florida
city: Atlanta
country: United States
facility: GSK Investigational Site
state: Georgia
city: Woodstock
country: United States
facility: GSK Investigational Site
state: Georgia
city: Lenexa
country: United States
facility: GSK Investigational Site
state: Kansas
city: Topeka
country: United States
facility: GSK Investigational Site
state: Kansas
city: Crestview Hills
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facility: GSK Investigational Site
state: Kentucky
city: Louisville
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facility: GSK Investigational Site
state: Kentucky
city: Metairie
country: United States
facility: GSK Investigational Site
state: Louisiana
city: Chevy Chase
country: United States
facility: GSK Investigational Site
state: Maryland
city: Bingham Farms
country: United States
facility: GSK Investigational Site
state: Michigan
city: Omaha
country: United States
facility: GSK Investigational Site
state: Nebraska
city: Las Vegas
country: United States
facility: GSK Investigational Site
state: Nevada
city: Albuquerque
country: United States
facility: GSK Investigational Site
state: New Mexico
city: Hickory
country: United States
facility: GSK Investigational Site
state: North Carolina
city: Raleigh
country: United States
facility: GSK Investigational Site
state: North Carolina
city: Winston-Salem
country: United States
facility: GSK Investigational Site
state: North Carolina
city: Cincinnati
country: United States
facility: GSK Investigational Site
state: Ohio
city: Cleveland
country: United States
facility: GSK Investigational Site
state: Ohio
city: Middleburg Heights
country: United States
facility: GSK Investigational Site
state: Ohio
city: Oklahoma City
country: United States
facility: GSK Investigational Site
state: Oklahoma
city: Duncansville
country: United States
facility: GSK Investigational Site
state: Pennsylvania
city: Lafayette Hill
country: United States
facility: GSK Investigational Site
state: Pennsylvania
city: Warwick
country: United States
facility: GSK Investigational Site
state: Rhode Island
city: Columbia
country: United States
facility: GSK Investigational Site
state: South Carolina
city: Greer
country: United States
facility: GSK Investigational Site
state: South Carolina
city: Mount Pleasant
country: United States
facility: GSK Investigational Site
state: South Carolina
city: Jackson
country: United States
facility: GSK Investigational Site
state: Tennessee
city: Austin
country: United States
facility: GSK Investigational Site
state: Texas
city: Fort Worth
country: United States
facility: GSK Investigational Site
state: Texas
city: San Angelo
country: United States
facility: GSK Investigational Site
state: Texas
city: San Antonio
country: United States
facility: GSK Investigational Site
state: Texas
city: San Antonio
country: United States
facility: GSK Investigational Site
state: Texas
city: Murray
country: United States
facility: GSK Investigational Site
state: Utah
city: Charlottesville
country: United States
facility: GSK Investigational Site
state: Virginia
Study officials:
affiliation: GlaxoSmithKline
name: GSK Clinical Trials
role: STUDY_DIRECTOR
References: