The 6-minute walk test (6MWT) is used as a clinical endpoint to evaluate drug 
efficacy in Duchenne Muscular Dystrophy (DMD) trials. A model was developed 
using digitized 6MWT data that estimated two slopes and two intercepts to 
characterize 6MWT improvement during development and 6MWT decline. Mean baseline 
6MWT was 362 (±87) meters. The model predicted an improvement at a rate of 20 
meters/year (95% confidence interval (CI) = 9.4-30) up until 10 years old (95% 
CI = 6.78-13.1), and then a decline at a rate of 85 meters/year (95% 
CI = 72-98). Interpatient slope variability for improvement and decline were 
similar at 21.9 percentage of coefficient of variation (%CV) and 23.3%CV, 
respectively. Model simulations using age demographics from a previous DMD 
natural history study could reasonably predict the trend in improvement and 
decline in the 6MWT. This model can be used to quantitate individual patient 
trajectories, identify prognostic factors for disease progression, and evaluate 
drug effect.