During the 6MWD, participants were asked to walk, at their own preferred speed, up and down a fixed distance until they were told to stop after 6 minutes. The participants were warned of the time and were told that they may stop earlier if they feel unable to continue. The total distance walked within 6 minutes (or until the participant stopped in case of early termination of the test), the 6MWD, was recorded in meters as well as any falls. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

The Intent-to-Treat (ITT) Population comprised all participants who received at least one dose of study medication and for whom at least one post-Baseline efficacy assessment was available. Only those participants available at the specified time point were analyzed.

The NSAA is a functional scale devised from the Hammersmith Scale of Motor Ability specifically for use in ambulant children with Duchenne muscular dystrophy (DMD). It consists of 17 activities graded 0 (unable to perform), 1 (performs with modifications), 2 (normal movement). The scale assesses activities required to remain functionally ambulant (e.g. rise from the floor), activities that can be difficult even early in the disease (e.g. standing on heels) and activities that are known to progressively deteriorate over time (stand from a chair, walk). NSAA total score was achieved by adding the responses of all activities, ranging from 0 to 34, with a score of 34 implying normal function and lower score implying more severe symptoms. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48. A positive change from Baseline indicated improvement.

ITT Population. Only those participants available at the indicated time point were analyzed.

The participant was asked to ascend four steps. Time was recorded with a stopwatch from the initiation of movement until the participant stood on the fourth step. A flight of steps with handrail was used for this test. Number of stairs ascended per second was calculated as 4 divided by the time to ascend 4 complete stairs. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT population. Only those participants available at the indicated time point were analyzed.

The participant was instructed to perform the test bare foot. No aids or orthoses were allowed. The participant was asked to traverse a marked 10-meter measured walkway as quickly as he safely could. Time was recorded to one tenth of a second with a stop watch from when his first foot crossed the start line until when the second foot crossed the finish line. If the wall was touched, it was noted how often. Care was taken to ensure that the participant was safe when completing this test. The assessor walked nearby to provide emergency help if needed, but did not support or provide manual assistance to the participant in any way. If the participant could not complete the 10-meter walk, the total distance was recorded. 10 minute walk/run speed was equal to 10 divided by time taken to complete 10 minute walk/run. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the indicated time point were analyzed.

The participant stood from a standardized supine position as quickly as possible when told to go. Time was recorded with a stopwatch from the initiation of movement until the assumption of upright standing. No aids or orthoses are allowed. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the indicated time point were analyzed.

The participant was asked to descend four steps. Time was recorded with a stopwatch from the initiation of movement until the participant stood on the fourth step. A flight of steps with handrail was used for this test. Number of stairs descended per second was calculated as 4 divided by the time to descend 4 complete stairs. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the indicated time point were analyzed.

Muscle strength was recorded by handheld myometry using a micro force evaluation testing 2 (FET2) myometer. Upper and lower limb proximal muscles were evaluated including knee flexors, knee extensors, elbow flexors, elbow extensors, shoulder abductors and hip flexors. The muscle strength total score (pounds) was the sum of the 12 individual muscle strength tests. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the indicated time point were analyzed.

All participants were ambulant when entered into the study; however they could have become non-ambulant at some time during the study. The date was recorded and the variable time to loss of ambulation was calculated as: time to loss of ambulation = date of loss of ambulation - date of first dose. Median and interquartile range i.e. 1st and 3rd quartile is presented.

ITT Population.

The number of accidental falls occurring during the 6MWD were counted. Data has been presented for the number of participants who experienced accidental falls (from 0 to 1) during the 6MWD assessment.

ITT Population. Only those participants with data available at the indicated time point were analyzed.

Creatine kinase is a muscle-specific enzyme; its level in serum is considered to reflect the extent of muscle damage. In the blood samples drawn to this purpose, the serum level of creatine kinase were measured. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the indicated time point were analyzed.

The FEV1 is the volume of air forcefully exhaled in 1 second, whereas the FVC is the volume of air that can be maximally forcefully exhaled using non-invasive spirometry was conducted to determine actual and percentage values for FVC and FEV1. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the specified time point were analyzed.

Biopsies were taken from their tibialis anterior muscle and few were taken from quadriceps. Total muscle ribonucleic acid (RNA) was isolated from muscle tissue sections and was analyzed by reverse transcriptase polymer chain reaction (RT-PCR). RT-PCR analysis focused on the area flanking the targeted exon 51 was performed to detect specific exon 51 skipping in muscle. Depending on the participants mutation different sets of DMD-gene specific RT and PCR primers were used. Sequence analysis was performed on isolated PCR products to confirm specific exon 51 skip band detection.

ITT Population. Only those participants with data available at the indicated time point were analyzed.

PedsQL version 3.0 scale is used to measure pediatric quality of life in children with neuromuscular disorders. The 25-item PedsQL encompasses 3 scales About My/My Childs Neuromuscular Disease (17 items), Communication (3 items), About Our Family Resources (5 items). A 5-point response scale is utilized (where 0=never a problem; 4=almost always a problem). It was assessed both by child and parent. PedsQL total score was calculated by reverse scoring individual items and linearly transforming the score to a 0-100 scale, where higher scores indicated better health-related quality of life. To reverse score individual items, the 0-4 scale items were transformed to a 0-100 scale as follows: 0=100, 1=75, 2=50, 3=25, and 4=0. Total score was then calculated as sum of items divided by number of items answered. Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48. A positive change from Baseline indicated improvement.

ITT Population. Only those participants available at the specified time point were analyzed.

The PF also called peak expiratory flow rate (PEFR) is a participants maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a participants ability to breathe out air. PCF was measured for participants wearing a nose clip and performing a maximum cough into a pocket peak flow meter. Baseline was defined as participants randomization assessment at Visit 3 (Day 0). Change from Baseline was calculated by subtracting the Baseline value from the value at Week 48.

ITT Population. Only those participants available at the specified time point were analyzed.

The CGI-I is scored based on the clinician's reflection of the participant's current overall clinical condition compared to the overall clinical condition just prior to the initiation of medication use (i.e., the period prior to Randomization). The CGI-I is rated without regard to the clinician's belief that any clinical changes are or are not due to medication and without consideration of the etiology of the symptoms. The CGI-I is measured on a 7-point Likert scale (where 1=very much improved, 2=much improved, 3=minimally improved, 4=no change, 5=minimally worse, 6=much worse, 7=very much worse). The score ranged from 1-7, where lower score indicated more improvement and higher score indicated less improvement.

ITT Population. Only those participants with data available at the indicated time point were analyzed.

A 15-item HUI questionnaire assessed Health-related quality of life (HRQoL). Responses from 15-item HUI were used to quantify HRQoL according to 2 health status classification systems, HUI Mark 2 (HUI2) and HUI Mark 3 (HUI3). HUI2 assessed 7 HRQoL dimensions: sensation, mobility, emotion, cognition, self care, pain and fertility. HUI3 assessed 8 HRQoL dimensions: vision, hearing, speech, ambulation, dexterity, emotion, cognition and pain. Both HUI2 (range from -0.03 to 1.0) and HUI3 (range from -0.36 to 1.0) utility scores were calculated using algorithms incorporating community-derived preference weights. A utility value of 1.0 represented perfect health and a utility value of 0.0 represented death. Lowest possible HUI2 score was -0.03 and for HUI3 score was -0.36, where scores less than 0 represented health states considered worse than death. Change from Baseline was calculated by subtracting Baseline value from Week 48 value. A positive change from Baseline indicated improvement.

ITT Population. Only those participants with data available at the specified time points were analyzed.

An AE is any untoward medical occurrence in a clinical investigation participant, temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease (new or exacerbated) temporally associated with the use of a medicinal product. An SAE is any untoward medical occurrence that, at any dose results in death, is life-threatening, requires hospitalization or prolongation of existing hospitalization, results in disability/incapacity, is a congenital anomaly/birth defect.

The Safety Population comprised of all participants who received at least one dose of study medication.

Blood pressure SBP, DBP and HR were recorded after five minutes of rest in a semi-supine position. The following changes from Baseline (Day 0) in vital signs were considered to be of potential clinical concern: DBP was defined as high (increase from Baseline >=20 and >=40 millimeters of mercury [mmHg] and low (decrease from Baseline >=20 and >=40 mmHg), SBP high (increase from Baseline >=10 and >=20 mmHg and low (decrease from Baseline >=10 and >=20 mmHg) and for HR high (increase from Baseline >=20 and >=40 beats per minute [bpm] and low (decrease from Baseline >=20 and >=40 bpm). Only those parameters for which a value of PCC was reported at any visit post-Baseline is presented.

Safety Population.

ECG measurements were carried out and the clinical interpretation of the ECG by the investigator was recorded as normal, abnormal but not clinically significant and abnormal clinically significant. The PCC ranges include, QT interval corrected for heart rate by Bazett's formula (QTcB) or QT interval corrected for heart rate by Fridericia's formula (QTcF) >450 milliseconds and any increase from Baseline of QTcB or QTcF. Participants were categorized as abnormal clinically significant based on the investigator's judgment and PCC ranges. Data has been presented for number of participants with abnormal clinically significant findings at any visit post-Baseline.

Safety Population.

Laboratory samples were collected for analysis of hematology parameters. The PCC values for hematology parameters: hematocrit was 1.02 x Upper limit of normal (ULN), for hemoglobin was 1.03 x ULN, for lymphocytes was 0.81 x lower limit of normal (LLN), for platelet count was 0.67 x LLN and 1.57 x ULN, for total neutrophils was 0.83 x LLN, and that for white blood cell count was 0.67 x LLN and value of 1.82 x ULN. Only those parameters for which a value of PCC was reported at any visit post-Baseline have been presented.

Safety Population.

Laboratory samples were collected for analysis of coagulation parameters. The PCC values for coagulation parameters activated partial thromboplastin time (aPTT) was 1.5 x ULN and aPTT ratio also known as international normalized ration (INR) was 1.2 x ULN. Only those parameters for which a value of PCC was reported at any visit post-Baseline is presented.

Safety Population.

Laboratory samples were collected for analysis of chemistry parameters. The PCC values for chemistry parameters for alanine amino transferase (ALT) plus total bilirubin (TB) was >=1.5 x ULN for TB and >=2 x ULN for ALT, for albumin was 0.86 x LLN, for asparatate amino transferase (AST) was >=2 x ULN, for calcium was 0.91 x LLN and 1.06 x ULN, for glucose was 0.71 x LLN and 1.41 x ULN, for phosphorus was 0.80 x LLN and 1.14 x ULN, for sodium was 0.96 x LLN and 1.03 x ULN, for potassium was 0.86 x LLN and 1.10 x ULN and that for alkaline phosphatase was >=2x ULN. Only those parameters for which a value of PCC was reported at any visit post-Baseline is presented.

Safety Population.

Urine samples were collected for analysis of abnormal urine parameters. Quantitative examination included the assessment for urine albumin excretion rate, urine alpha-1-microglobulin, urine creatinine excretion-24 hour and urine protein excretion-24 hour. Only those parameters for which a value of >reference range high was reported at any visit post-Baseline is presented.

Safety Population. Only those participants available at the specified time points were analyzed.

Blood samples for pharmacokinetic assessment were taken at Week 0 (Randomization) at 0.5, 1, 3 hours post-dose and at Week 8,12, 24, 36 and 47 at pre-dose, and between 1 and 4 hours post-dose. Data has been presented for plasma concentrations of GSK2402968 following subcutaneous administration.

The Pharmacokinetic Population comprised all participants who were randomized to the study and from whom at least one blood sample was obtained for assessment of GSK2402968 concentration. Only those participants available at the specified time points were analyzed.