Muscle biopsies in clinical trials for Duchenne muscular dystrophy - Patients' and caregivers' perspective

The number of clinical trials for Duchenne muscular dystrophy is increasing. Many trials require muscle biopsies, which involve an invasive surgical procedure. Little is known about short- and long-term impacts of muscle biopsies as perceived by patients and caregivers. Therefore a survey was held among patients and their caregivers who participated in trials involving muscle biopsies, in seven countries. Seventy-eight responses were received. Analysis revealed that many patients and parents had significant anxiety before the biopsy. The main concern of caregivers was the required general anaesthesia. In most cases biopsies caused pain and temporarily hampered daily activities. The main long-term impact was scarring, although large variation in size was reported. Seventy-nine percent of caregivers were little bothered and 21% were moderately or severely bothered by the scar. Willingness to consider another biopsy in future protocols was higher for open-label studies than for placebo-controlled trials. Caregivers stressed the importance of knowing the results of biopsy analyses; only a minority actually received this information. Recommendations are made on the informed consent procedure regarding risks and consequences of muscle biopsies, and communication of results. Furthermore, efforts should be made to minimise the impact of biopsies through pain management and by considering plastic surgery

Antisense PMO cocktails effectively skip dystrophin exons 45-55 in myotubes transdifferentiated from DMD patient fibroblasts

Antisense-mediated exon skipping has made significant progress as a therapeutic platform in recent years, especially in the case of Duchenne muscular dystrophy (DMD). Despite FDA approval of eteplirsen-the first-ever antisense drug clinically marketed for DMD-exon skipping therapy still faces the significant hurdles of limited applicability and unknown truncated protein function. In-frame exon skipping of dystrophin exons 45-55 represents a significant approach to treating DMD, as a large proportion of patients harbor mutations within this "hotspot" region. Additionally, patients harboring dystrophin exons 45-55 deletion mutations are reported to have exceptionally mild to asymptomatic phenotypes. Here, we demonstrate that a cocktail of phosphorodiamidate morpholino oligomers can effectively skip dystrophin exons 45-55 in vitro in myotubes transdifferentiated from DMD patient fibroblast cells. This is the first report of substantive exons 45-55 skipping in DMD patient cells. These findings help validate the use of transdifferentiated patient fibroblast cells as a suitable cell model for dystrophin exon skipping assays and further emphasize the feasibility of dystrophin exons 45-55 skipping in patients

Evaluation of serum MMP-9 as predictive biomarker for antisense therapy in Duchenne

Duchenne Muscular Dystrophy (DMD) is a severe muscle disorder caused by lack of dystrophin. Predictive biomarkers able to anticipate response to the therapeutic treatments aiming at dystrophin re-expression are lacking. The objective of this study is to investigate Matrix Metalloproteinase-9 (MMP-9) as predictive biomarker for Duchenne. Two natural history cohorts were studied including 168 longitudinal samples belonging to 66 patients. We further studied 1536 samples obtained from 3 independent clinical trials with drisapersen, an antisense oligonucleotide targeting exon 51: an open label study including 12 patients; a phase 3 randomized, double blind, placebo controlled study involving 186 patients; an open label extension study performed after the phase 3. Analysis of natural history cohorts showed elevated MMP-9 levels in patients and a significant increase over time in longitudinal samples. MMP-9 decreased in parallel to clinical stabilization in the 12 patients involved in the open label study. The phase 3 study and subsequent extension study clarified that the decrease in MMP-9 levels was not predictive of treatment response. These data do not support the inclusion of serum MMP-9 as predictive biomarker for DMD patients