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Background: Myotonic dystrophy type 1 results from an RNA gain-of-function mutation, in which DM1 protein kinase (DMPK) transcripts carrying expanded trinucleotide repeats exert deleterious effects. Antisense oligonucleotides (ASOs) provide a promising approach to treatment of myotonic dystrophy type 1 because they reduce toxic RNA levels. We aimed to investigate the safety of baliforsen (ISIS 598769), an ASO targeting DMPK mRNA., Methods: In this dose-escalation phase 1/2a trial, adults aged 20-55 years with myotonic dystrophy type 1 were enrolled at seven tertiary referral centres in the USA and randomly assigned via an interactive web or phone response system to subcutaneous injections of baliforsen 100 mg, 200 mg, or 300 mg, or placebo (6:2 randomisation at each dose level), or to baliforsen 400 mg or 600 mg, or placebo (10:2 randomisation at each dose level), on days 1, 3, 5, 8, 15, 22, 29, and 36. Sponsor personnel directly involved with the trial, participants, and all study personnel were masked to treatment assignments. The primary outcome measure was safety in all participants who received at least one dose of study drug up to day 134. This trial is registered with ClinicalTrials.gov (NCT02312011), and is complete., Findings: Between Dec 12, 2014, and Feb 22, 2016, 49 participants were enrolled and randomly assigned to baliforsen 100 mg (n=7, one patient not dosed), 200 mg (n=6), 300 mg (n=6), 400 mg (n=10), 600 mg (n=10), or placebo (n=10). The safety population comprised 48 participants who received at least one dose of study drug. Treatment-emergent adverse events were reported for 36 (95%) of 38 participants assigned to baliforsen and nine (90%) of ten participants assigned to placebo. Aside from injection-site reactions, common treatment-emergent adverse events were headache (baliforsen: ten [26%] of 38 participants; placebo: four [40%] of ten participants), contusion (baliforsen: seven [18%] of 38; placebo: one [10%] of ten), and nausea (baliforsen: six [16%] of 38; placebo: two [20%] of ten). Most adverse events (baliforsen: 425 [86%] of 494; placebo: 62 [85%] of 73) were mild in severity. One participant (baliforsen 600 mg) developed transient thrombocytopenia considered potentially treatment related. Baliforsen concentrations in skeletal muscle increased with dose., Interpretation: Baliforsen was generally well tolerated. However, skeletal muscle drug concentrations were below levels predicted to achieve substantial target reduction. These results support the further investigation of ASOs as a therapeutic approach for myotonic dystrophy type 1, but suggest improved drug delivery to muscle is needed., Funding: Ionis Pharmaceuticals, Biogen., Competing Interests: Declaration of interests CFB, LM, DAN, and SX are employees of Ionis Pharmaceuticals, which funded the trial, and own stock options in Ionis Pharmaceuticals. CAT received support from Ionis Pharmaceuticals for consultation and sponsored research and carried out collaborative research with CFB under National Institutes of Health (NIH) grant U01NS072323; provides consulting to Biogen, Vertex, Entrada, and Avidity Biosciences; received honoraria from Sanofi; served on scientific advisory boards for Dyne and Pepgen; and serves on the Myotonic Dystrophy Foundation Board. KE received consulting fees from Ionis Pharmaceuticals, Avidity, and Dyne Therapeutics; and received honoraria from the Myotonic Dystrophy Foundation and the Muscular Dystrophy Association. CH receives royalties for the use of multiple disease specific instruments; provided consultation to Biogen, Ionis Pharmaceuticals, aTyr Pharma, AMO Pharma, Acceleron Pharma, Cytokinetics, Expansion Therapeutics, Harmony Biosciences, Regeneron Pharmaceuticals, Astellas Pharmaceuticals, AveXis, Recursion Pharmaceuticals, IRIS Medicine, Takeda Pharmaceutical Company, Scholar Rock, Avidity Biosciences, Novartis Pharmaceuticals Corporation, SwanBio Therapeutics, and the Marigold Foundation; and receives grant support from the Department of Defense, Duchenne UK, Parent Project Muscular Dystrophy, Recursion Pharmaceuticals, Swan Bio Therapeutics, Neurocrine Biosciences, the National Institute of Neurological Disorders and Stroke, the Muscular Dystrophy Association, the Friedreich's Ataxia Research Alliance, Cure Spinal Muscular Atrophy, and the Amyotrophic Lateral Sclerosis Association. WDA received a consulting fee and grant funding from Avidity Biosciences and a consulting fee from Dyne Therapeutics. TA received a grant or contract from the Myotonic Dystrophy Foundation and was on the Myotonic Dystrophy Foundation scientific advisory board. JWD received consulting fees from Affinia Therapeutics and Shift Therapeutics; honoraria from Biogen and Roche Pharmaceuticals; participated in advisory boards for AMO Pharmaceuticals, Avidity Biosciences, Biogen, Cytokinetics, Epirium Bio, Ionis Pharmaceuticals, Kate Therapeutics, Novartis Gene Therapies, Roche/Genentech Pharmaceuticals, Sarepta Therapeutics, Scholar Rock, Shift Therapeutics, and Vertex Pharmaceuticals; has leadership roles for Muscular Dystrophy Association, Myotonic Dystrophy Foundation, and Cure Congenital Muscular Dystrophy. GD is an employee of Biogen and owns stock options in Biogen. TD received consulting fees from Dyne, Roche/Genentech Pharmaceuticals, Biogen, Trinds, and ATOM; speaking honoraria for Genentech, Biogen, Roche, and Sarepta; has served on Advisory boards for Novartis, Pfizer, Actigraph, Scholar Rock, Sarepta, Sanofi Genzyme, and Cytokinetics; has unpaid leadership roles for myotonic dystrophy exercise recommendations and physical therapy guidance and the CureSMA Medical Advisory Council. NEJ received royalties or licenses from University of Rochester; received consulting fees from AMO Pharma Fulcrum Therapeutics, Avidity Biosciences, Dyne, Vertex, Arthex, and Entrada; participated in a Data Safety Monitoring Board for Biogen; and owns stock or stock options in ML Bio Solutions. DJL received funding from the DuchenneXchange Advisory Council, Cure Duchenne. JMS received consulting fees from Dyne Therapeutics, Roche, Avidity, ML Bio, Fulcrum Therapeutics, MT Pharma, Sarepta, and Amylyx; payment or honorarium from MDA; and stock or stock options from Dyne Therapeutics. SHS received consulting fees from Reata Pharmaceuticals, Avidity Biosciences, and Dyne therapeutics. KMB was an employee of Ionis Pharmaceuticals at the time the trial was conducted; is a current employee of and owns stock options in Acadia Pharmaceuticals; is an advisor to non-profit organisations Myotonic Dystrophy Foundation and SMA Foundation; and is a Board Member of DTx Pharma. CFB is a Board member of Flamingo Therapeutics and Hereditary Disease Foundation. RM is the chair of three clinical trials in Duchenne muscular dystrophy funded by TRiNDS. All other authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Objective: To assess mexiletine's long-term safety and effect on 6-minute walk distance in a well-defined cohort of patients with myotonic dystrophy type 1 (DM1)., Methods: We performed a randomized, double-blind, placebo-controlled trial of mexiletine (150 mg 3 times daily) to evaluate its efficacy and safety in a homogenous cohort of adult ambulatory patients with DM1. The primary outcome was change in 6-minute walk distance at 6 months. Secondary outcomes included changes in hand grip myotonia, strength, swallowing, forced vital capacity, lean muscle mass, Myotonic Dystrophy Health Index scores, and 24-hour Holter and ECG results at 3 and 6 months., Results: Forty-two participants were randomized and 40 completed the 6-month follow-up (n = 20 in both groups). No significant effects of mexiletine were observed on 6-minute walk distance, but hand grip myotonia was improved with mexiletine treatment. There were no differences between the mexiletine and placebo groups with respect to the frequency or type of adverse events. Changes in PR, QRS, and QTc intervals were similar in mexiletine- and placebo-treated participants., Conclusions: There was no benefit of mexiletine on 6-minute walk distance at 6 months. Although mexiletine had a sustained positive effect on objectively measured hand grip myotonia, this was not seen in measures reflecting participants' perceptions of their myotonia. No effects of mexiletine on cardiac conduction measures were seen over the 6-month follow-up period., Classification of Evidence: This study provides Class I evidence that for ambulatory patients with DM1, mexiletine does not significantly change 6-minute walk distance at 6 months., (© 2020 American Academy of Neurology.)

Introduction: The prevalence and impact of symptoms affecting individuals with pediatric forms of myotonic dystrophy type-1 (DM1) are not well understood., Methods: Patients from the United States, Canada, and Sweden completed a survey that investigated 20 themes associated with pediatric-onset DM1. Participants reported the prevalence and importance of each theme affecting their lives. Surveys from participants were matched with surveys from their caregivers for additional analysis., Results: The most prevalent symptomatic themes included problems with hands or fingers (79%) and gastrointestinal issues (75%). Problems with urinary/bowel control and gastrointestinal issues were reported to have the greatest impact on patients' lives. Responses from participants and their caregivers had varying levels of agreement among symptomatic themes., Discussion: Many symptoms have meaningful impact on disease burden. The highest levels of agreement between caregivers and individuals with pediatric forms of myotonic dystrophy were found for physical activity themes., (© 2019 Wiley Periodicals, Inc.)

Introduction: The Myotonic Dystrophy Health Index (MDHI) is a disease-specific, patient-reported outcome measure. The objective of this study was to translate, evaluate, and validate a Japanese version of the MDHI (MDHI-J)., Methods: We utilized forward and backward translations and qualitative interviews with 11 myotonic dystrophy type 1 (DM1) participants. We subsequently tested the internal consistency, test-retest reliability, concurrent validity against muscle strength, and 3 quality-of-life measures, and the known-groups validity of the MDHI-J with 60 adult patients., Results: The MDHI-J was found to be culturally appropriate, comprehensive, and clinically relevant. The MDHI-J and its subscales had high internal consistency (mean Cronbach's α = 0.91), test-retest reliability (intraclass coefficient 0.678-0.915), and concurrent validity (Spearman's ρ - 0.869 to 0.904). MDHI-J scores were strongly associated with employment, duration of symptoms, and modified Rankin Scale., Discussion: The MDHI-J is suitable and valid to measure patient-reported disease burden in adult Japanese patients with DM1. Muscle Nerve 59:577-577, 2019., (© 2019 Wiley Periodicals, Inc.)

Introduction: Validation studies of disease-specific instruments for myotonic dystrophy type-1 (DM1) are required prior to their global use in clinical trials involving different cultures and countries. Here we translate and culturally adapt the Myotonic Dystrophy Health Index (MDHI), a disease-specific patient-reported outcome (PRO) measure, for a French DM1 population., Methods: Using the International Society for Pharmacoeconomics and Outcomes Research Task Force method for translation and adaptation of PRO questionnaires, we created a French translation of the MDHI. We subsequently tested this instrument in a cohort of French-speaking patients with DM1., Results: The MDHI was forward and back translated and modified by consensus to create the most compatible translation. Cognitive interviews were conducted with 5 patients with DM1 to ensure the usability and understanding of the translation., Discussion: The French version of the MDHI is an optimal translation of the original instrument that is acceptable to native patients and ready for clinical trial use. Muscle Nerve 57: 686-689, 2018., (© 2017 Wiley Periodicals, Inc.)

Introduction: Generic patient reported outcome measures have had varied success in tracking QoL in myotonic dystrophy type 1 (DM1)., Aim: To analyze changes of Individualized Neuromuscular Quality of Life questionnaire (INQoL) scores in clinic patients with DM1 over a 6-year period., Method: Patients completed the INQoL at baseline and after a 6-year period through their attendance in a neurology outpatient clinic. Severity of muscular involvement in DM1 was analyzed using the Muscular Impairment Rating Scale (MIRS)., Results: Ninety-nine DM1 patients completed a baseline visit. Sixty-seven of these patients were retested at an interval time. The overall INQoL score improved in our sample of patients (P<.05) as did the following subscales: myotonia (P<.05), pain (P<.05), activities (P<.01), social relationships (P<.01), and body image (P<.05). No changes were observed for the independence and emotions scales. There were no differences in mean change of INQoL scores between patients with worsened MIRS and those with no change in MIRS scale after follow-up (P>.05)., Conclusion: Individualized Neuromuscular Quality of Life questionnaire scores improved in our cohort of DM1 patients during a 6-year period. INQoL score did not correlate with progression of muscle weakness. This must be better understood before the selection of the instrument for use in trials to measure therapeutic benefit in DM1 patients., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The Myotonic Dystrophy Health Index (MDHI) is a disease-specific, self-reported outcome measure that assesses total disease burden and 17 areas of Myotonic Dystrophy type 1 (DM1) specific health. This study translated the MDHI into Italian and validated the instrument using a cohort of Italian DM1 patients. Italian DM1 patients were interviewed regarding the form and content of the instrument. Thirty-eight DM1 patients were subsequently recruited to test the reliability and concurrent validity of the instrument by serially completing the MDHI and a battery of clinical tests. Lastly, we determined the internal consistency of the Italian MDHI and each of its subscales. The internal consistency was excellent in the total Italian MDHI score and acceptable in all of its subscales; the test-retest reliability was high (intraclass correlation coefficient = 0.95); Italian MDHI total scores and subscales were associated with neuromuscular function, cognitive and social health, respiratory function, and quality of life. Overall, the Italian MDHI is valid and well suited to measure the multi-dimensional aspects of disease burden in Myotonic Dystrophy clinical trials., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objective: Herein, we describe the disease burden and age-related changes of congenital-onset myotonic dystrophy (CDM) in childhood., Methods: Children with CDM and age-matched controls aged 0 to 13 years were enrolled. Participants were divided into cohorts based on the following age groups: 0-2, 3-6, and 7-13 years. Each cohort received age-appropriate evaluations including functional testing, oral facial strength testing, neuropsychological testing, quality-of-life measurements, and ECG. Independent-samples t test or Wilcoxon 2-sample test was used to compare the differences between children with CDM and controls. Probability values less than 0.05 are reported as significant., Results: Forty-one participants with CDM and 29 healthy controls were enrolled. The 6-minute walk was significantly different between CDM (258.3 m [SD 176.0]) and control participants (568.2 m [SD 73.2]). The mean lip force strength was significantly different in CDM (2.1 N [SD 2.8)] compared to control participants (17.8 N [SD 7.6]). In participants with CDM, the mean IQ (65.8; SD 18.4) was 3 SDs below the mean compared to standardized norms. Measurements of grip strength, sleep quality, and quality of life were also significantly different. Strength measures (oral facial strength, grip strength, and 6-minute walk) correlated with each other but not with participant IQ., Conclusions: This work identifies important phenotypes associated with CDM during childhood. Several measures of strength and function were significantly different between participants with CDM and controls and may be useful during future therapeutic trials., (© 2016 American Academy of Neurology.)

Introduction: The Myotonic Dystrophy Health Index (MDHI) is a disease-specific patient-reported outcome measure. Here, we examine the associations between the MDHI and other measures of disease burden in a cohort of individuals with myotonic dystrophy type-1 (DM1)., Methods: We conducted a cross-sectional study of 70 patients with DM1. We examined the associations between MDHI total and subscale scores and scores from other clinical tests. Participants completed assessments of strength, myotonia, motor and respiratory function, ambulation, and body composition. Participants also provided blood samples, underwent physician evaluations, and completed other patient-reported outcome measures., Results: MDHI total and subscale scores were strongly associated with muscle strength, myotonia, motor function, and other clinical measures., Conclusions: Patient-reported health status, as measured by the MDHI, is associated with alternative measures of clinical health. These results support the use of the MDHI as a valid tool to measure disease burden in DM1 patients., (© 2015 Wiley Periodicals, Inc.)

Objective: To determine the frequency and relative importance of the most life-affecting symptoms in myotonic dystrophy type 2 (DM2) and to identify the factors that have the strongest association with these symptoms., Methods: We conducted a cross-sectional study of adult patients with DM2 from a National Registry of DM2 Patients to assess the prevalence and relative importance of 310 symptoms and 21 symptomatic themes. Participant responses were compared by age categories, sex, educational attainment, employment status, and duration of symptoms., Results: The symptomatic themes with the highest prevalence in DM2 were the inability to do activities (94.4%), limitations with mobility or walking (89.2%), hip, thigh, or knee weakness (89.2%), fatigue (89.2%), and myotonia (82.6%). Participants identified the inability to do activities and fatigue as the symptomatic themes that have the greatest overall effect on their lives. Unemployment, a longer duration of symptoms, and less education were associated with a higher average prevalence of all symptomatic themes (p < 0.01). Unemployment, a longer duration of symptoms, sex, and increased age were associated with a higher average effect of all symptomatic themes among patients with DM2 (p < 0.01)., Conclusions: The lives of patients with DM2 are affected by a variety of symptoms. These symptoms have different levels of significance and prevalence in this population and vary across DM2 subgroups in different demographic categories., (© 2015 American Academy of Neurology.)

Introduction: In preparation for clinical trials we examine the validity, reliability, and patient understanding of the Myotonic Dystrophy Health Index (MDHI)., Methods: Initially we partnered with 278 myotonic dystrophy type-1 (DM1) patients and identified the most relevant questions for the MDHI. Next, we used factor analysis, patient interviews, and test-retest reliability assessments to refine and evaluate the instrument. Lastly, we determined the capability of the MDHI to differentiate between known groups of DM1 participants., Results: Questions in the final MDHI represent 17 areas of DM1 health. The internal consistency was acceptable in all subscales. The MDHI had a high test-retest reliability (ICC = 0.95) and differentiated between DM1 patient groups with different disease severities., Conclusions: Initial evaluation of the MDHI provides evidence that it is valid and reliable as an outcome measure for assessing patient-reported health. These results suggest that important aspects of DM1 health may be measured effectively using the MDHI., (Copyright © 2013 Wiley Periodicals, Inc.)

Objective: To determine the most critical symptoms in a national myotonic dystrophy type 1 (DM1) population and to identify the modifying factors that have the greatest effect on the severity of these symptoms., Methods: We performed a cross-sectional study of 278 adult patients with DM1 from the national registry of patients with DM1 between April and August 2010. We assessed the prevalence and relative significance of 221 critical DM1 symptoms and 14 disease themes. These symptoms and themes were chosen for evaluation based on prior interviews with patients with DM1. Responses were categorized by age, CTG repeat length, gender, and duration of symptoms., Results: Participants with DM1 provided symptom rating survey responses to address the relative frequency and importance of each DM1 symptom. The symptomatic themes with the highest prevalence in DM1 were problems with hands or arms (93.5%), fatigue (90.8%), myotonia (90.3%), and impaired sleep or daytime sleepiness (87.9%). Participants identified fatigue and limitations in mobility as the symptomatic themes that have the greatest effect on their lives. We found an association between age and the average prevalence of all themes (p < 0.01) and between CTG repeat length and the average effect of all symptomatic themes on participant lives (p < 0.01)., Conclusions: There are a wide range of symptoms that significantly affect the lives of patients with DM1. These symptoms, some previously underrecognized, have varying levels of importance in the DM1 population and are nonlinearly dependent on patient age and CTG repeat length.