title: Effects of glucocorticoids and idebenone on respiratory function in patients with duchenne muscular dystrophy.
abstract: In Duchenne muscular dystrophy (DMD) progressive weakness of respiratory muscles leads to a restrictive pulmonary syndrome that contributes to early morbidity and mortality. Currently no curative treatment exists for DMD. In a Phase II randomized placebo-controlled study (DELPHI) in 21 DMD boys at age 8-16 years, idebenone (450 mg/d) showed trends of efficacy for cardiac and respiratory endpoints. Since the DELPHI study population comprised both glucocorticoid-naïve subjects and glucocorticoid-users, we now report a post-hoc analysis investigating the effects of glucocorticoids and idebenone on markers of respiratory weakness, particularly peak expiratory flow (PEF) percent predicted (PEF%p). Baseline values of PEF%p correlated well with the percent predicted values for maximal inspiratory mouth pressure (MIP%p), forced vital capacity (FVC%p), and forced expired volume in 1 sec (FEV1%p). Baseline PEF%p and FVC%p were significantly higher in patients on concomitant glucocorticoids compared to glucocorticoid-naïve patients. In the latter subgroup, idebenone caused a 8.0 ± 12.1% improvement in PEF%p, whilst patients on placebo declined by -12.3 ± 17.9% (P < 0.05) in the course of the 12 month study. In patients receiving concomitant glucocorticoids, PEF%p remained stable (-0.4 ± 14.6%) in the idebenone group compared to a decline by -6.2 ± 12.4% (P = 0.24) in the placebo group. Idebenone showed a trend for efficacy on FVC%p only in glucocorticoid-naïve patients. Because of the study limitations, these data are exploratory and preclude any firm conclusions. In conclusion, PEF appears to be a sensitive respiratory function parameter that could be a valid and clinically relevant endpoint in intervention studies in DMD. In DELPHI the effect size of idebenone on PEF%p was significantly larger in steroid-naive patients, possibly indicating a maximum treatment effect reached by steroids or steroid-mediated suppression of idebenone's effects. The impact of standard care glucocorticoids on respiratory function will have to be considered in the planning of future interventional trials in DMD.
authors.affiliation: Department of Child Neurology, University Hospitals Leuven, Belgium. gunnar.buyse@uzleuven.be
authors.forename: Gunnar M
authors.initials: GM
authors.lastname: Buyse
authors.forename: Nathalie
authors.initials: N
authors.lastname: Goemans
authors.forename: Marleen
authors.initials: M
authors.lastname: van den Hauwe
authors.forename: Thomas
authors.initials: T
authors.lastname: Meier
mesh_terms: D000293:Adolescent; D000975:Antioxidants / Q000627:therapeutic use; D002648:Child; D004311:Double-Blind Method; D005938:Glucocorticoids / Q000627:therapeutic use*; D006801:Humans; D008168:Lung / Q000187:drug effects / Q000503:physiopathology; D008297:Male; D053580:Muscle Strength / Q000187:drug effects; D020388:Muscular Dystrophy, Duchenne / Q000188:drug therapy* / Q000503:physiopathology*; D012119:Respiration / Q000187:drug effects*; D012129:Respiratory Function Tests / Q000379:methods / Q000706:statistics & numerical data; D012132:Respiratory Muscles / Q000187:drug effects; D014451:Ubiquinone / Q000031:analogs & derivatives* / Q000627:therapeutic use; D014797:Vital Capacity / Q000187:drug effects
chemical_list: D000975:Antioxidants; D005938:Glucocorticoids; D014451:Ubiquinone; C036619:idebenone
keywords: Duchenne muscular dystrophy; glucocorticoids; idebenone; peak expiratory flow; respiratory function