BACKGROUND AND OBJECTIVES:Vamorolone demonstrated similar efficacy for Duchenne muscular dystrophy (DMD) compared with prednisone in a 24-week exploratory analysis and may reduce key side effects compared with classic corticosteroids. In this study, we compare the efficacy and anthropometric effect of vamorolone 6 mg/kg/d with prednisone 0.75 mg/kg/d and deflazacort 0.9 mg/kg/d in steroid-naïve boys aged 4 to <7 years using data from 2 trials. METHODS:VISION-DMD was a phase 2b, 48-week randomized, double-blind trial assessing vamorolone 2 and 6 mg/kg/d vs placebo and prednisone 0.75 mg/kg/d to 24 weeks. Finding the Optimum Steroid Regimen for DMD (FOR-DMD) was a double-blind, parallel-group randomized trial comparing daily prednisone 0.75 mg/kg/d, daily deflazacort 0.9 mg/kg/d, and intermittent prednisone 0.75 mg/kg (10/10 days on/off). Entropy balancing generated weighted data for mixed model for repeated measures analyses that compared VISION-DMD vamorolone 6 mg/kg/d efficacy and anthropometric outcomes with FOR-DMD prednisone and deflazacort outcomes at 6 and 12 months. Inclusion criteria were boys with genetically confirmed DMD, age 4 to <7 years, ambulatory, and able to complete a time-to-stand (TTSTAND) assessment in <10 seconds at baseline. RESULTS:All interventions showed motor improvements relative to baseline at 6 and 12 months. Using the weighted cohorts and at 12 months, vamorolone 6 mg/kg/d (n = 28) had similar changes in TTSTAND velocity, the primary motor endpoint component in both trials, vs daily prednisone (n = 50) or deflazacort (n = 55; mean baseline age 5.42 years all groups), but with CIs overlapping minimal clinically important thresholds of 0.023 rises per second (TTSTAND velocity least squares mean [LSM] difference [95% CI]: vamorolone 6 mg/kg/d vs prednisone 0.75 mg/kg/d, 0.004 rises per second [-0.025 to 0.032] and vs deflazacort 0.9 mg/kg/d, 0.001 rises per second [-0.027 to 0.028]). Body mass index (BMI) Z-scores increased in all groups, greatest with vamorolone (12-month LSM difference [95% CI]: vamorolone vs prednisone 0.57 [0.24-0.90]; vamorolone vs deflazacort 0.29 [0.03-0.56]), whereas growth slowdown occurred in prednisone- and deflazacort-treated boys but not vamorolone (12-month LSM difference in height Z-scores [95% CI]: vamorolone vs prednisone 0.57 [0.24-0.90]; vamorolone vs deflazacort 0.72 [0.53-0.91]). DISCUSSION:Vamorolone demonstrated numerically similar TTSTAND velocity changes to prednisone and deflazacort at 1 year; however, interpretations of differences are limited by 95% CIs crossing minimally important difference thresholds. Further evidence of the growth-protective effect of vamorolone was observed; however, all treatments increased BMI. Vamorolone provides a linear growth-protective classic corticosteroid alternative. TRIAL REGISTRATION INFORMATION:NCT03439670; NCT01603407. CLASSIFICATION OF EVIDENCE:This Class III study did not definitively identify differences in efficacy between vamorolone and classic corticosteroids but found that vamorolone protects linear growth in boys with DMD.

Vamorolone is a dissociative glucocorticoid receptor agonist for treating Duchenne muscular dystrophy (DMD). The VBP15-006 study assessed vamorolone safety, tolerability, and pharmacokinetics in 2- to < 4 and 7- to < 18-year-old boys with DMD. Results for 7- to < 18-year-old boys, either corticosteroid (CS)-untreated or switching from prior CS treatment, are reported here. Exploratory objectives included efficacy and pharmacodynamic biomarkers related to safety. In this phase II, open-label, multiple-dose study, participants received 2 or 6 mg/kg/day vamorolone for 12 weeks, followed by treatment in an expanded access protocol (EAP Canada). 34 participants (12 CS-untreated, 22 CS-treated) aged 7- to < 18 years were enrolled. Most treatment-emergent adverse events were mild. All 34 participants completed VBP15-006 and entered EAP Canada. During EAP Canada, CS-untreated participants maintained stable linear growth, while CS-treated participants exhibited catch-up growth consistent with serum bone biomarkers (median total vamorolone exposure 1.3 and 1.7 years, respectively). Some weight gain occurred, especially in CS-untreated participants receiving 6 mg/kg/day. Dose-dependent adrenal suppression occurred in CS-untreated and CS-treated participants; 2 individuals who switched from deflazacort to vamorolone 2 mg/kg/day had generalized weakness consistent with adrenal insufficiency. Vamorolone showed dose-dependent pharmacokinetics, rapid clearance, and no accumulation. There were no relevant efficacy changes in CS-treated and CS-untreated groups at either dose. Vamorolone demonstrated a consistent safety profile in 7- to < 18-year-old boys with DMD. Switching to 6 mg/kg/day vamorolone appeared to mitigate adrenal insufficiency risk. There was no negative effect on growth, and catch-up growth occurred in previously CS-treated individuals switching to vamorolone. ClinicalTrials.gov: NCT05185622, NCT03863119. First submitted 09-11-2021.

Genetic modifiers of Duchenne muscular dystrophy (DMD) that alter disease severity or response to therapy have been reported using natural history or registry data sets of older corticosteroid-treated patients. We tested associations of genetic modifiers on motor function outcomes in young (4 to < 7 years) steroid naïve clinical trial participants. Participants in clinical trials (VBP15-002/003 [n = 48]; VBP15-004 [n = 121]; DNA available for n = 110) were genotyped for eight published genetic modifier loci, and associations of genotypes with baseline motor function defined via an age-adjusted linear model. Corticosteroid drug response was modeled by genotype-stratified placebo vs. steroid treatment at 12- and 24-weeks posttreatment (mixed model for repeated measures). Serum proteome profiles (SomaScan) were stratified by modifier genotype, and modifier-associated biomarkers mapped to muscle cell types using snSeq datasets. Two loci showed association with baseline motor outcomes (LTBP4, DYNLT5). LTBP4 genotype (rs1131620) was associated with baseline (pretreatment) motor function for all five motor tests studied (time to stand from supine velocity, time to run/walk 10 m velocity, time to climb 4 stairs velocity, 6-min walk distance, and NorthStar Ambulatory Assessment). DYNLT5 genotype (rs1060575) was associated with time to stand from supine velocity, time to climb 4 stairs velocity, and time to run/walk 10 m velocity. Stratification of baseline proteome profiles by LTBP4 genotype and mapping of genotype-associated serum proteins to specific cell types in muscle (snRNAseq) suggested that IL-23, IL-6, and IL-17D interacting pathways in muscle capillaries are contributors to disease progression. In contrast, the DYNLT5 genotype was associated with proteosome and chaperonin pathways. Trial Registration: clinicaltrials.gov identifier: NCT02760264, NCT02760277, NCT03439670.

BACKGROUND AND OBJECTIVES:Vamorolone is a dissociative corticosteroid (CS) approved by the US Food and Drug Administration in 2023 for treating Duchenne muscular dystrophy (DMD). This study evaluated the safety, tolerability, and pharmacokinetics (PK) of vamorolone in young boys with DMD; exploratory objectives included efficacy and patient-reported outcomes. METHODS:A 12-week, phase II, open-label, multiple-dose study (VBP15-006) enrolled CS-naive boys with DMD aged 2-<4 years in Canada. Participants received 2 or 6 mg/kg/d oral vamorolone. An ongoing expanded access protocol (EAP) provided longer-term data. Primary end points were the occurrence of treatment-emergent adverse events (TEAEs) and changes from baseline to week 12 in height, weight, and body mass index (BMI); other end points included PK and effects of vamorolone on muscle function. RESULTS:Twenty boys (mean age [SD] 3.4 [0.39] years) with similar baseline characteristics were enrolled; all completed VBP15-006 and 19 continued to receive vamorolone through EAP Canada. TEAEs were mostly mild, with no deaths, serious TEAEs, or TEAEs leading to drug discontinuation during VBP15-006. TEAEs were more frequent with 6 mg/kg/d vamorolone than with 2 mg/kg/d, with gastrointestinal disorders and infections/infestations, respectively, most reported. Vamorolone use was associated with morning serum cortisol reductions in all patients, more pronounced with 6 mg/kg/d. Stable growth trajectories were observed at both doses throughout VBP15-006 and the EAP Canada follow-up period, with a total median (Q1; Q3) exposure to vamorolone of 2 years (1.7; 2.3). By EAP Canada last visit, 8/19 patients had weight and BMI z-scores changes >0.5, suggestive of excessive weight gain over time. Vamorolone displayed a dose-dependent PK profile with rapid absorption and no accumulation. Dose-dependent improvements in motor function (measured by Bayley-III gross motor scaled score) were observed. Glucose metabolism and bone turnover biomarkers remained stable. Ease of administration was rated favorably. DISCUSSION:Vamorolone was well tolerated in 2-<4-year-old boys with DMD, with no new safety concerns identified. A dose-dependent PK profile was observed, consistent with previous studies. Exploratory evidence suggested dose-dependent improvements in gross motor function. These findings are consistent with potential therapeutic benefit of vamorolone for young boys with DMD. TRIAL REGISTRATION INFORMATION:ClinicalTrials.gov: NCT05185622 (VBP15-006; clinicaltrials.gov/study/NCT05185622), NCT03863119 (EAP; clinicaltrials.gov/study/NCT03863119). First submitted November 9, 2021. First patient enrolled: March 21, 2022. CLASSIFICATION OF EVIDENCE:The VBP15-006 study provides Class IV evidence that in boys with DMD aged 2-<4 years, 12-week treatment with vamorolone was not associated with serious adverse events or changes in weight, height, or BMI. Gastrointestinal events and infections were the most reported TEAEs.

Background: Becker’s muscular dystrophy (BMD) is a clinically heterogeneous dystrophinopathy caused by in-frame mutations in the dystrophin gene, resulting in variable disease severity. This variability limits the effectiveness of standardized functional measures for tracking progression. Circulating biomarkers, including urinary titin fragments generated during muscle injury, offer a promising noninvasive approach for assessing disease status. Methods: Mass spectrometry-based urinary proteomic profiling identified titin fragments as candidate biomarkers of muscle injury in BMD. Titin fragments were validated in urine samples from 50 BMD subjects (33 ambulatory, 17 non-ambulatory) and 11 age-matched healthy controls using targeted mass spectrometry and ELISA. Results: Urinary titin levels were significantly elevated by 4.75-fold and 2.47-fold in ambulatory and non-ambulatory BMD patients, respectively, compared with healthy controls. Titin levels also distinguished ambulatory from non-ambulatory BMD patients, demonstrating potential utility for monitoring disease progression and therapeutic response. Conclusions: Urinary titin fragments represent a promising noninvasive biomarker for BMD, with potential applicability to related neuromuscular disorders and clinical trials evaluating disease progression and treatment efficacy.

Corticosteroids are among the most highly prescribed drugs. Chronic treatment with corticosteroids causes osteopenia, as well as growth failure in children. Our goal was to identify serum biomarkers of prednisone-related perturbations of bone and/or cartilage metabolism associated with growth failure in children. We utilized longitudinal serum samples from a double-blind, placebo- and prednisone-controlled trial of vamorolone in 4 to < 7 years children with Duchenne muscular dystrophy assayed by proteomic methods. Vamorolone is a recently approved bone-sparing corticosteroid that has been shown to have similar efficacy as prednisone but does not cause growth failure. The study included a 24-week Period 1 (placebo, prednisone [0.75 mg/kg/day], vamorolone [6 mg/kg/day]), and a 24-week Period 2 where placebo and vamorolone groups crossed over to vamorolone. Clinical laboratory measures of ALP, osteocalcin, P1NP, and CTX1 showed significant reductions with prednisone, but were unchanged by vamorolone treatment or placebo. Proteomics studies of serum proteins reduced by prednisone, but not vamorolone or placebo, identified 10 proteins where mutations in the corresponding genes are known to cause genetic disorders of cartilage and/or bone (collagens [COL2A1, Chondrocalcin, COL6A1, COL9A1, COL10A1, COL11A2], aggrecan core protein [ACAN], biglycan [BGN], osteopetrosis-associated transmembrane protein 1 [OSTM1], and noggin [NOG]). On transitioning from prednisone to vamorolone, all 10 biomarkers returned to baseline levels. Non-human (animal) studies have shown that traditional corticosteroids cause apoptosis of terminal hypertrophic chondrocytes associated with growth failure. Our clinical trial studies suggest that the 10 novel, corticosteroid-related biomarkers likely reflect the induction of apoptosis in terminal hypertrophic chondrocytes and osteoblasts by traditional corticosteroids. Vamorolone may spare chondrocytes and osteoblasts from this apoptosis, consistent with maintenance of normal growth in vamorolone-treated children.Trial registration The clinical trial registration (clinicaltrials.gov) is NCT03439670 ( https://www.clinicaltrials.gov/study/NCT03439670 ).

Loss-of-function variants of the CHKB gene cause an autosomal recessive disease described as an early onset congenital megaconial (large peripheral mitochondria) muscular dystrophy. CHKB encodes choline kinase β, the first enzyme in the biochemical pathway for synthesis of the major membrane phospholipid phosphatidylcholine. Chkb -/- mice recapitulate the human disease with affected skeletal muscle displaying a decrease in strength, myofiber atrophy, megaconial mitochondria, fat accumulation within muscle cells, and an increase in muscle injury. Here, we assessed the therapeutic potential of an AAV therapy for the treatment of CHKB-mediated muscular dystrophy. Chkb -/- mice were injected once suborbitally with three different doses of recombinant AAV9 (rAAV9) encoding human CHKB under control of a constitutive and ubiquitous promoter (AAV9-CHKB). The AAV9-CHKB-treated mice were biochemically and phenotypically indistinguishable from the wild type mice. In the Chkb -/- mouse model, all doses resulted in expression of the CHKB protein and restored choline kinase β enzyme activity, body and muscle weight, and normal muscle cell physiology, and they prevented lipid metabolism imbalance and increased the capacity to walk. These findings point to AAV9-mediated gene therapy as a potential treatment for CHKB-mediated disease.

Muscle inflammation is one of the hallmarks of Duchenne muscular dystrophy (DMD). Dystrophin-deficient skeletal muscle cells produce higher levels of pro-inflammatory cytokines such as interleukin 1β (IL-1β) in response to toll-like receptor stimulation compared to normal muscle skeletal cells. IL- 1β induces the human skeletal muscle secretion of the myokine Interleukin-6 (IL-6). Here, we evaluated the effect of a human IgG1κ monoclonal antibody (canakinumab (Ilaris®)) that specifically blocks the IL-1β effect on IL-6 secretion by human skeletal muscle cells. Canakinumab is an excellent candidate for therapeutic repositioning to treat DMD because it is an FDA-approved drug to treat periodic fever syndromes and systemic juvenile idiopathic arthritis. Unlike previous generations of IL-1 inhibitors, canakinumab is highly specific for the IL-1β ligand, has a longer half-life, and does not interfere with other IL-1-activated inflammatory pathways. Following cell culture optimization and viability assays to assess toxicity, skeletal muscle cells were stimulated with IL-1β (10 ng/mL) for 48 hours in the presence of nine concentrations of canakinumab ranging from 0.001 nM to 1000 nM, and IL-6 production was measured with an enzyme-linked immunosorbent assay. Pre-incubation of myoblasts with canakinumab before IL-1β-stimulation, significantly reduced IL-6 production at concentrations of 1, 10, 100, 250, and 1000 nM relative to controls, yielding an IC50 of 0.264 nM. On the other hand, co-incubation of canakinumab with IL-1β before addition to myoblasts resulted in a significant inhibition with the IC50 reducing to 0.126 nM, less than half of the previous method. Canakinumab also did not affect myotube viability at 10 nM and was also able to significantly reduce the production of IL-6, when the cells were stimulated with IL-1β (10 ng/ml). Taken together, our results show that canakinumab is a potent inhibitor of IL-1β signaling in muscle cells. These results align with previously published pre-clinical work with other IL-1 inhibitors in the mdx mouse model and support further investigation into the clinical utility of repositioning canakinumab to treat DMD.

The effect of vamorolone, the first dissociative corticosteroid for Duchenne muscular dystrophy (DMD), at the mineralocorticoid receptor (MR) was investigated in the Phase 1 mechanistic LIONHEART study and using serum samples from boys with DMD in the pivotal VISION-DMD trial. In LIONHEART, 30 healthy adult males were randomized 1:1:1 to vamorolone 20 mg/kg, eplerenone 200 mg, or no treatment arms. A fludrocortisone challenge was administered between -9 h and 24 h after treatment. The LIONHEART primary outcome was urinary Na+/K+ ratio; additional outcomes were pharmacokinetics, urine Na+ and K+ concentrations, and safety. In VISION-DMD, boys with DMD aged 4-7 years were treated with vamorolone 2 or 6 mg/kg/d for 48 weeks or with prednisone 0.75 mg/kg/d or placebo for 24 weeks followed by vamorolone 2 or 6 mg/kg/d for 20 weeks following a 4-week washout. Serum sample analysis from VISION-DMD used the SomaScan® 7 K assay. In LIONHEART, vamorolone reversed the decrease in urinary Na+/K+ ratio induced by fludrocortisone, confirming vamorolone MR antagonism. The maximum MRA effect of vamorolone was observed at 4-6 h post dose and was detectable until approximately 10 h post dose. Vamorolone reversed fludrocortisone induced Na+ retention with no evidence of decreased potassium excretion. Vamorolone 20 mg/kg was well tolerated, and results were consistent with known PK parameters. The VISION-DMD results showed vamorolone-specific increases in renin serum levels, as well as klotho, and calcium carrier proteins fetuin A and B, consistent with an MR antagonist effect. The available data confirm the MR antagonistic effect of vamorolone in humans. LIONHEART: NCT06649409; VISION-DMD: NCT03439670.

IntroductionTo further advance our understanding of Muscular Dystrophies (MDs) and Spinocerebellar Ataxias (SCAs), it is necessary to identify the biological patterns associated with disease pathology. Although progress has been made in the fields of genetics and transcriptomics, there is a need for proteomics and metabolomics studies. The present study aimed to be the first to document serum metabolic signatures of MDs (DMD, BMD, and LGMD 2A) SCAs (SCA 1-3), from a South Asian perspective.MethodsA total of 28 patients (SCA 1-10, SCA 2-2, SCA 3-2, DMD-10, BMD-2, LGMD-2) and eight controls (aged 8–65 years) were included. Metabolomic analysis was performed by Ultrahigh Performance Liquid Chromatography-Tandem Mass Spectroscopy (UPLC-MS/MS), with support from the Houston Omics Collaborative.Results and discussionAmino acid metabolism was the primary altered super pathway in DMD followed by carbohydrate metabolism and lipid metabolism. In contrast, BMD and LGMD 2A exhibited a more prominent alteration in lipid metabolism followed by amino acid metabolism. In SCAs, primarily lipid, amino acid, peptide, nucleotide, and xenobiotics pathways are affected. Our findings offer new insights into the variance of metabolite levels in MD and SCA, with substantial implications for pathology, drug development, therapeutic targets and clinical management. Intriguingly, this study identified two novel metabolites associated with SCA. This pilot cross-sectional study warrants further research involving larger groups of participants, to validate our findings.

CONTEXT:Vamorolone, a novel "dissociative" steroid, demonstrated similar efficacy in muscle function relative to prednisone 0.75 mg/kg/day but improved linear growth and bone turnover markers in a randomized trial of pediatric Duchenne muscular dystrophy (DMD). OBJECTIVES:To determine the frequency of adrenal suppression (AS) induced by vamorolone and prednisone in pediatric DMD and to assess cortisol thresholds using a monoclonal antibody immunoassay. METHODS:Post hoc analysis of cortisol levels was performed on data from a randomized, double-blind, placebo- and prednisone-controlled 24-week trial of vamorolone with a 24-week crossover extension. Morning and ACTH-stimulated cortisol levels were measured using the Elecsys II immunoassay, with AS defined as a stimulated cortisol of <500 nmol/L ("historical threshold") and <400 nmol/L ("revised threshold"). RESULTS:Mean age at enrolment was 5.41 ± 0.86 years (n = 118). At week 24, the proportion of participants with AS using the historical and revised cortisol thresholds, respectively, were as follows: prednisone 0.75 mg/kg/day = 100% (25/25) and 92.0% (23/25); vamorolone 6 mg/kg/day = 95.2% (20/21) and 90.5% (19/21); vamorolone 2 mg/kg/day = 84.2% (16/19) and 47.5% (9/19); and placebo = 20.0% (4/20) and 0% (0/20). Morning and peak ACTH-stimulated cortisol were strongly correlated in steroid-treated boys (Spearman correlation week 48 = 0.83). CONCLUSION:AS after vamorolone and prednisone was frequent and vamorolone-associated AS appeared dose-dependent. A lower stimulated cortisol threshold may be appropriate when using a monoclonal assay. We recommend hydrocortisone for glucocorticoid stress dosing in patients receiving vamorolone.

Background and Objectives:Understanding the reliability of outcomes used in clinical care and trials is important to delineate intervention-induced change from random variability. Reliability, sensitivity, and clinical meaningfulness of change are all key aspects of choosing the most appropriate outcome measure for a clinical trial. Common outcome measures to monitor progression and treatment effect in Duchenne muscular dystrophy (DMD) include measures of strength (myometry) and motor function tests: stand from supine velocity (STANDV), North Star Ambulatory Assessment (NSAA), 6-minute walk distance (6MWD), 10-m run/walk (RWV), and 4-stair climb velocity (CLIMBV). Our objective was to present test-retest reliability of common outcome measures using pretreatment measurements and to provide insights into missing measurements. Methods:Data were used on outcome measures in steroid-naïve, 4 to <7 years participants with DMD in 2 multisite, multicountry vamorolone trials (VBP15-002 [n = 48 participants] and VBP15-004 [n = 121 participants]). Bland-Altman analysis, the coefficient of variation, and the intraclass correlation coefficient (ICC) were used. Results:Based on the ICC, NSAA, RWV, and CLIMBV have good reliability, whereas the 6MWD and STANDV have moderate reliability. Two different techniques were used for myometry in VBP15-002 (CINRG Quantitative Measurement System [CQMS]) and VBP15-004 (MicroFET2 handheld digital muscle dynamometer [HHD]). Reliability of myometry ranged from poor to moderate, and CQMS did not show improved reliability over HHD. The 6MWD and myometry showed the highest rates of missingness. Because of similar age ranges and harmonized outcomes, our findings were compared with the FOR-DMD cohort. Myometry and CLIMBV were not in FOR-DMD; reliability findings were concordant for the 4 outcomes in common. For most outcomes, we found reduced reliability compared with previous studies in older age groups. Discussion:Reliable outcome measures, appropriate for the age of patients, are key to improving power in clinical trials, leading to fewer participants needed and reducing patient and site burden. We found NSAA, RWV, and CLIMBV to be the most reliable. This should be considered in the context of sensitivity to drug effect, and clinical meaningfulness of changes observed: all 5 motor outcomes were sensitive to drug effect of vamorolone and prednisone, whereas myometry was not.

Background and Objectives Duchenne muscular dystrophy (DMD) is caused by pathogenic variants of the DMD gene, leading to the loss of dystrophin. Clinical variability in DMD can complicate interpretation of interventional data in clinical trials. One source of clinical variability is allelic heterogeneity (different pathogenic variants with different effects on dystrophin protein expression). We sought to determine whether gene variant classes in clinical trial participants potentially affect clinical trial data interpretation. Methods We analyzed 186 vamorolone trial participants with DMD (VBP15-002/003; VBP15-004) who were 4 to <7 years old and steroid-na & iuml;ve at baseline. We stratified participants into gene variant classes by either variant location in the gene affecting different gene promoters (5 ' [Dp427-only] vs 3 ' [Dp427+other isoforms]) or residual dystrophin levels (null vs possible non-null [5 ' gene variants, exon 44 skippable, splice site]). We evaluated associations with baseline motor outcomes and treatment response (prednisone and vamorolone). Results Participants with variants in ex63 and downstream (null for Dp427+Dp140+Dp71 protein isoforms) showed poorer baseline motor outcomes for time to stand from supine velocity than those with variants in ex1-44 (Dp427 only). No significant baseline differences were found between likely null and possible non-null variants. Participants with only Dp427 involvement showed significantly better treatment response for the 6-minute walk distance. Most of the comparisons of baseline motor function and treatment response were similar between variant classes. Discussion The large variation in baseline motor function in young, steroid-na & iuml;ve patients with DMD is only minimally explained by different gene variant classes. While there is strong literature support for 3 ' variants leading to a more severe motor and cognitive DMD phenotype, we found this variant class under-represented in our clinical trials. This suggests that they may fail inclusion criteria (failure to follow commands; poor motor function). Subgroup analyses in DMD clinical trials at a young age range based on gene variant class may not reveal significant differences and would be relatively noninformative.

Purpose: This study defines correlative and causal relationships between muscle strength and size before and after unilateral resistance training (RT) in a large cohort of healthy adults, focusing on sex differences within these relationships. Methods: Results from 1233 participants (504 males and 729 females) in a retrospective analysis were included. Maximal voluntary isometric contraction strength (MVC), one-repetition maximum strength (1RM), biceps cross-sectional area (CSA) and elbow flexor volume (VOL) measures of the non-dominant and dominant arm were evaluated from baseline and after 12-wk RT twice per week. Correlations of MVC and VOL and 1RM and VOL were calculated in the whole cohort and within each sex independently. Causal analysis modeling was used to infer mechanistic relationships among variables. Results: Absolute muscle strength and size related to one another both at baseline and following training, however correlation strength in each sex were weak. After RT, MVC relative change and VOL relative change correlations were correlated for the whole cohort (r=0.16; p<0.001) and females (r=0.18; p<0.001), but not in males (r=0.11; p=0.07). No significant correlations for relative change in 1RM and VOL were observed for the whole cohort or within sex. Causal discovery determined that change in VOL caused significant change in 1RM (but not MVC) and age was identified as a potential cause. Conclusions: Sex differences occur in muscle size and strength relationship adaptations following resistance training, most notably the absence of significant relationships between relative size and strength changes in men. Simpson's paradox bias, where assessing the combined data of males and females (also affecting overall sample size) affects identifies patterns differently than assessing relationships within each sex, may partially explain our findings.

Oxidative stress has long been implicated in Parkinson's disease (PD) pathogenesis, although the sources and regulation of reactive oxygen species (ROS) production are poorly defined. Pathogenic mutations in the gene encoding leucine-rich repeat kinase 2 (LRRK2) are associated with increased kinase activity and a greater risk of PD. The substrates and downstream consequences of elevated LRRK2 kinase activity are still being elucidated, but overexpression of mutant LRRK2 has been associated with oxidative stress, and antioxidants reportedly mitigate LRRK2 toxicity. Here, using CRISPR-Cas9 gene-edited HEK293 cells, RAW264.7 macrophages, rat primary ventral midbrain cultures, and PD patient-derived lymphoblastoid cells, we found that elevated LRRK2 kinase activity was associated with increased ROS production and lipid peroxidation and that this was blocked by inhibitors of either LRRK2 kinase or NADPH oxidase 2 (NOX2). Oxidative stress induced by the pesticide rotenone was ameliorated by LRRK2 kinase inhibition and was absent in cells devoid of LRRK2. In a rat model of PD induced by rotenone, a LRRK2 kinase inhibitor prevented the lipid peroxidation and NOX2 activation normally seen in nigral dopaminergic neurons in this model. Mechanistically, LRRK2 kinase activity was shown to regulate phosphorylation of serine-345 in the p47(phox) subunit of NOX2. This, in turn, led to translocation of p47(phox) from the cytosol to the membrane-associated gp91(phox) (NOX2) subunit, activation of the NOX2 enzyme complex, and production of ROS. Thus, LRRK2 kinase activity may drive cellular ROS production in PD through the regulation of NOX2 activity.

Background: Dilated cardiomyopathy (DCM) is a major complication of, and leading cause of mortality in Duchenne muscular dystrophy (DMD). Its severity, age at onset, and rate of progression display wide variability, whose molecular bases have been scarcely elucidated. Potential DCM-modifying factors include glucocorticoid (GC) and cardiological treatments, DMD mutation type and location, and variants in other genes. Methods and Results: We retrospectively collected 3138 echocardiographic measurements of left ventricular ejection fraction (EF), shortening fraction (SF), and end-diastolic volume (EDV) from 819 DMD participants, 541 from an Italian multicentric cohort and 278 from the Cooperative International Neuromuscular Group Duchenne Natural History Study (CINRG-DNHS). Using generalized estimating equation (GEE) models, we estimated the yearly rate of decrease of EF (–0.80%) and SF (–0.41%), while EDV increase was not significantly associated with age. Utilizing a multivariate generalized estimating equation (GEE) model we observed that mutations preserving the expression of the C-terminal Dp71 isoform of dystrophin were correlated with decreased EDV (–11.01 mL/m 2 , p = 0.03) while for dp116 were correlated with decreased EF (–4.14%, p = <0.001). The rs10880 genotype in the LTBP4 gene, previously shown to prolong ambulation, was also associated with increased EF and decreased EDV (+3.29%, p = 0.002, and –10.62 mL/m 2 , p = 0.008) with a recessive model. Conclusions: We quantitatively describe the progression of systolic dysfunction progression in DMD, confirm the effect of distal dystrophin isoform expression on the dystrophin-deficient heart, and identify a strong effect of LTBP4 genotype of DCM in DMD. Keywords Duchenne muscular dystrophy , dilated cardiomyopathy , genetic modifiers , , , glucocorticoid treatment

Background and ObjectivesVamorolone is a dissociative agonist of the glucocorticoid receptor that has shown similar efficacy and reduced safety concerns in comparison with prednisone in Duchenne muscular dystrophy (DMD). This study was conducted to determine the efficacy and safety of vamorolone over 48 weeks and to study crossover participants (prednisone to vamorolone; placebo to vamorolone).MethodsA randomized, double-blind, placebo-controlled and prednisone-controlled clinical trial of 2 doses of vamorolone was conducted in participants with DMD, in the ages from 4 years to younger than 7 years at baseline. The interventions were 2 mg/kg/d of vamorolone and 6 mg/kg/d of vamorolone for 48 weeks (period 1: 24 weeks + period 2: 24 weeks) and 0.75 mg/kg/d of prednisone and placebo for the first 24 weeks (before crossover). Efficacy was evaluated through gross motor outcomes and safety through adverse events, growth velocity, body mass index (BMI), and bone turnover biomarkers. This analysis focused on period 2.ResultsA total of 121 participants with DMD were randomized. Vamorolone at a dose of 6 mg/kg/d showed maintenance of improvement for all motor outcomes to week 48 (e.g., for primary outcome, time to stand from supine [TTSTAND] velocity, week 24 least squares mean [LSM] [SE] 0.052 [0.0130] rises/s vs week 48 LSM [SE] 0.0446 [0.0138]). After 48 weeks, vamorolone at a dose of 2 mg/kg/d showed similar improvements as 6 mg/kg/d for North Star Ambulatory Assessment (NSAA) (vamorolone 6 mg/kg/d-vamorolone 2 mg/kg/d LSM [SE] 0.49 [1.14]; 95% CI -1.80 to 2.78, p = 0.67), but less improvement for other motor outcomes. The placebo to vamorolone 6 mg/kg/d group showed rapid improvements after 20 weeks of treatment approaching benefit seen with 48-week 6 mg/kg/d of vamorolone treatment for TTSTAND, time to run/walk 10 m, and NSAA. There was significant improvement in linear growth after crossover in the prednisone to vamorolone 6 mg/kg/d group, and rapid reversal of prednisone-induced decline in bone turnover biomarkers in both crossover groups. There was an increase in BMI after 24 weeks of treatment that then stabilized for both vamorolone groups.DiscussionImprovements of motor outcomes seen with 6 mg/kg/d of vamorolone at 24 weeks of treatment were maintained to 48 weeks of treatment. Vamorolone at a dose of 6 mg/kg/d showed better maintenance of effect compared with vamorolone at a dose of 2 mg/kg/d for most (3/5) motor outcomes. Bone morbidities of prednisone (stunting of growth and declines in serum bone biomarkers) were reversed when treatment transitioned to vamorolone.Trial Registration InformationClinicalTrials.gov Identifier: NCT03439670.Classification of EvidenceThis study provides Class I evidence that for boys with DMD, the efficacy of vamorolone at a dose of 6 mg/kg/d was maintained over 48 weeks.

Background: Dilated cardiomyopathy (DCM) is a major complication of, and leading cause of mortality in Duchenne muscular dystrophy (DMD). Its severity, age at onset, and rate of progression display wide variability, whose molecular bases have been scarcely elucidated. Potential DCM-modifying factors include glucocorticoid (GC) and cardiological treatments, DMD mutation type and location, and variants in other genes. Methods and Results: We retrospectively collected 3138 echocardiographic measurements of left ventricular ejection fraction (EF), shortening fraction (SF), and end-diastolic volume (EDV) from 819 DMD participants, 541 from an Italian multicentric cohort and 278 from the Cooperative International Neuromuscular Group Duchenne Natural History Study (CINRG-DNHS). Using generalized estimating equation (GEE) models, we estimated the yearly rate of decrease of EF (–0.80%) and SF (–0.41%), while EDV increase was not significantly associated with age. Utilizing a multivariate generalized estimating equation (GEE) model we observed that mutations preserving the expression of the C-terminal Dp71 isoform of dystrophin were correlated with decreased EDV (–11.01 mL/m2, p = 0.03) while for dp116 were correlated with decreased EF (–4.14%, p = <0.001). The rs10880 genotype in the LTBP4 gene, previously shown to prolong ambulation, was also associated with increased EF and decreased EDV (+3.29%, p = 0.002, and –10.62 mL/m2, p = 0.008) with a recessive model. Conclusions: We quantitatively describe the progression of systolic dysfunction progression in DMD, confirm the effect of distal dystrophin isoform expression on the dystrophin-deficient heart, and identify a strong effect of LTBP4 genotype of DCM in DMD.