SOUTH PLAINFIELD, N.J., Aug. 26, 2013 /PRNewswire/ -- Data published in the medical journal Muscle & Nerve demonstrate the clinical meaningfulness of the 6-minute walk test (6MWT) as a primary endpoint to measure disease progression and walking ability in ambulatory Duchenne muscular dystrophy (DMD) trials. The research also showed that a range of 20 to 30 meters in walking ability is a clinically meaningful change, as measured by 6-minute walk distance (6MWD). This analysis is based on natural history data obtained from PTC Therapeutics' Phase 2b trial of ataluren in 174 patients with nonsense mutation Duchenne muscular dystrophy (nmDMD), the first placebo-controlled, multi-national study of a new chemical entity for DMD.
"Given that several novel approaches to the treatment of Duchenne muscular dystrophy have shown promise in preclinical and/or proof-of-concept clinical studies, the research community has faced the need to identify and develop clinically meaningful outcome measures for use in pivotal therapeutic trials. In boys with DMD, walking abnormalities are a major disease manifestation that have great importance to patients and their families," stated Dr. Craig McDonald, one of the world's leading experts in muscular dystrophy clinical endpoints and DMD natural history studies and lead author of the two publications. "We pioneered the development of the 6MWT for DMD with PTC in conjunction with the ataluren trials and I am pleased to have collaborated with the ataluren study group to demonstrate the 6MWT as a reliable, valid, and meaningful endpoint for Duchenne muscular dystrophy." Dr. McDonald added, "The data from the ataluren placebo group has recently been replicated in other natural history studies conducted by investigators in Belgium and Italy. All three data sets show a similar change in 6-minute walk distance over one year as a measure of disease progression."
The 6MWT was originally developed as an integrated assessment of cardiac, respiratory, circulatory and muscular capacity, and it has previously been used as a primary outcome in a number of clinical studies to support the regulatory approval of treatments for a number of other neuromuscular disorders. In a prior short-term study (McDonald et al 2010), the 6MWT was established as a feasible, safe and reliable outcome measure of walking ability in boys with DMD, who have not yet transitioned to full-time wheelchair use. A follow-up longitudinal study concluded that changes in 6MWD depend on stride length and age. Improvements in 6MWD were observed in both healthy subjects and patients with DMD <7 years of age, attributed to maturational development. In contrast, the walking ability of older DMD patients (≥7 years of age) worsened, while the walking ability of older healthy subjects (≥7 years of age) tended to either increase or remain stable. Subsequent studies have confirmed this observation and also demonstrated that 6MWD correlates with other clinical endpoints in DMD, such as timed function tests and the North Star Ambulatory Assessment (NSAA), as well as established patient-reported outcomes of physical function.
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