Evaluating longitudinal therapy effects via the North Star Ambulatory Assessment.

INTRODUCTION/AIMS: In comparative studies, treatment effects are typically evaluated at a specific time point. When data are collected periodically, an alternative, clinically meaningful approach could be used to assess the totality of treatment effects. We applied a well-developed analytical procedure for evaluating longitudinal treatment effects using North Star Ambulatory Assessment (NSAA) data for illustration. METHODS: The NSAA comprises 17 scorable items/outcomes that measure changes in motor function. Using NSAA data from the published ataluren phase 3, randomized, placebo-controlled trial (NCT01826487), cumulative counts of failures to perform each item (transition from 2/1 [able/impaired] to 0 [unable]) were collected at specified time points for each patient over 48 wk. Treatment group-wise mean cumulative item failure count curves were constructed, comparing ataluren versus placebo and deflazacort versus prednisone/prednisolone among placebo-treated patients. The steeper the curve, the worse the outcome. A clinically meaningful summary of the between-group difference was provided for each comparison. RESULTS: The curve was uniformly steeper for placebo than ataluren after 16 wk and for prednisone/prednisolone than deflazacort after 8 wk. The two curves in each comparison continued to diverge thereafter, indicating sustained treatment benefits over time. Using a unique analytical approach, cumulative failure rates were reduced, on average, by 27% for ataluren versus placebo (rate ratio, 0.73; 95% confidence interval [CI], 0.55-0.97; p = .027) and 28% for deflazacort versus prednisone/prednisolone (rate ratio, 0.72; 95% CI, 0.53-0.96; p = .028). DISCUSSION: Unlike fixed-time analyses, this analytical approach enabled demonstration of cumulative, longitudinal treatment effects over time using repeatedly measured NSAA observations.

Deflazacort vs prednisone treatment for Duchenne muscular dystrophy: A meta-analysis of disease progression rates in recent multicenter clinical trials.

INTRODUCTION: In this study we characterized disease progression over 48 weeks among boys receiving deflazacort vs prednisone/prednisolone placebo arm treatment in two recent Duchenne muscular dystrophy (DMD) clinical trials. METHODS: Ambulatory boys with DMD receiving placebo in the phase 3 ataluren (N = 115) and tadalafil (N = 116) trials were included. The trials required at least 6 months of prior corticosteroid use and stable baseline dosing. Associations between corticosteroid use and 48-week changes in ambulatory function were estimated using mixed models. Adjusted differences between corticosteroid groups were pooled in a meta-analysis. RESULTS: In the meta-analysis, deflazacort-treated patients vs prednisone/prednisolone-treated patients experienced, on average, lower declines of 28.3 meters on 6-minute walk distance (95% confidence interval [CI], 5.7, 50.9; 2.9 seconds on rise from supine [95% CI, 0.9, 4.9 seconds]; 2.3 seconds on 4-stair climb [95% CI, 0.5, 4.1 seconds]; and 2.9 [95% CI, 0.1, 5.8] points on the North Star Ambulatory Assessment linearized score). DISCUSSION: Deflazacort-treated patients experienced significantly lower functional decline over 48 weeks.

Ataluren in patients with nonsense mutation Duchenne muscular dystrophy (ACT DMD): a multicentre, randomised, double-blind, placebo-controlled, phase 3 trial.

BACKGROUND: Duchenne muscular dystrophy (DMD) is a severe, progressive, and rare neuromuscular, X-linked recessive disease. Dystrophin deficiency is the underlying cause of disease; therefore, mutation-specific therapies aimed at restoring dystrophin protein production are being explored. We aimed to assess the efficacy and safety of ataluren in ambulatory boys with nonsense mutation DMD. METHODS: We did this multicentre, randomised, double-blind, placebo-controlled, phase 3 trial at 54 sites in 18 countries located in North America, Europe, the Asia-Pacific region, and Latin America. Boys aged 7-16 years with nonsense mutation DMD and a baseline 6-minute walk distance (6MWD) of 150 m or more and 80% or less of the predicted normal value for age and height were randomly assigned (1:1), via permuted block randomisation (block size of four) using an interactive voice-response or web-response system, to receive ataluren orally three times daily (40 mg/kg per day) or matching placebo. Randomisation was stratified by age (<9 years vs ≥9 years), duration of previous corticosteroid use (6 months to <12 months vs ≥12 months), and baseline 6MWD (<350 m vs ≥350 m). Patients, parents and caregivers, investigational site personnel, PTC Therapeutics employees, and all other study personnel were masked to group allocation until after database lock. The primary endpoint was change in 6MWD from baseline to week 48. We additionally did a prespecified subgroup analysis of the primary endpoint, based on baseline 6MWD, which is reflective of anticipated rates of disease progression over 1 year. The primary analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01826487. FINDINGS: Between March 26, 2013, and Aug 26, 2014, we randomly assigned 230 patients to receive ataluren (n=115) or placebo (n=115); 228 patients comprised the intention-to-treat population. The least-squares mean change in 6MWD from baseline to week 48 was -47·7 m (SE 9·3) for ataluren-treated patients and -60·7 m (9·3) for placebo-treated patients (difference 13·0 m [SE 10·4], 95% CI -7·4 to 33·4; p=0·213). The least-squares mean change for ataluren versus placebo in the prespecified subgroups was -7·7 m (SE 24·1, 95% CI -54·9 to 39·5; p=0·749) in the group with a 6MWD of less than 300 m, 42·9 m (15·9, 11·8-74·0; p=0·007) in the group with a 6MWD of 300 m or more to less than 400 m, and -9·5 m (17·2, -43·2 to 24·2; p=0·580) in the group with a 6MWD of 400 m or more. Ataluren was generally well tolerated and most treatment-emergent adverse events were mild to moderate in severity. Eight (3%) patients (n=4 per group) reported serious adverse events; all except one event in the placebo group (abnormal hepatic function deemed possibly related to treatment) were deemed unrelated to treatment. INTERPRETATION: Change in 6MWD did not differ significantly between patients in the ataluren group and those in the placebo group, neither in the intention-to-treat population nor in the prespecified subgroups with a baseline 6MWD of less than 300 m or 400 m or more. However, we recorded a significant effect of ataluren in the prespecified subgroup of patients with a baseline 6MWD of 300 m or more to less than 400 m. Baseline 6MWD values within this range were associated with a more predictable rate of decline over 1 year; this finding has implications for the design of future DMD trials with the 6-minute walk test as the endpoint. FUNDING: PTC Therapeutics.

Deflazacort versus prednisone/prednisolone for maintaining motor function and delaying loss of ambulation: A post HOC analysis from the ACT DMD trial.

INTRODUCTION: ACT DMD was a 48-week trial of ataluren for nonsense mutation Duchenne muscular dystrophy (nmDMD). Patients received corticosteroids for ≥6 months at entry and stable regimens throughout study. This post hoc analysis compares efficacy and safety for deflazacort and prednisone/prednisolone in the placebo arm. METHODS: Patients received deflazacort (n = 53) or prednisone/prednisolone (n = 61). Endpoints included change from baseline in 6-minute walk distance (6MWD), timed function tests, estimated age at loss of ambulation (extrapolated from 6MWD). RESULTS: Mean changes in 6MWD were -39.0 m (deflazacort; 95% confidence limit [CL], -68.85, -9.17) and -70.6 m (prednisone/prednisolone; 95% CL, -97.16, -44.02). Mean changes in 4-stair climb were 3.79 s (deflazacort; 95% CL, 1.54, 6.03) and 6.67 s (prednisone/prednisolone; 95% CL, 4.69, 8.64). CONCLUSIONS: This analysis, limited by its post hoc nature, suggests greater preservation of 6MWD and 4-stair climb with deflazacort vs. prednisone/prednisolone. A head-to-head comparison will better define these differences. Muscle Nerve 58: 639-645, 2018.

Ataluren treatment of patients with nonsense mutation dystrophinopathy.

INTRODUCTION: Dystrophinopathy is a rare, severe muscle disorder, and nonsense mutations are found in 13% of cases. Ataluren was developed to enable ribosomal readthrough of premature stop codons in nonsense mutation (nm) genetic disorders. METHODS: Randomized, double-blind, placebo-controlled study; males ≥ 5 years with nm-dystrophinopathy received study drug orally 3 times daily, ataluren 10, 10, 20 mg/kg (N=57); ataluren 20, 20, 40 mg/kg (N=60); or placebo (N=57) for 48 weeks. The primary endpoint was change in 6-Minute Walk Distance (6MWD) at Week 48. RESULTS: Ataluren was generally well tolerated. The primary endpoint favored ataluren 10, 10, 20 mg/kg versus placebo; the week 48 6MWD Δ=31.3 meters, post hoc P=0.056. Secondary endpoints (timed function tests) showed meaningful differences between ataluren 10, 10, 20 mg/kg, and placebo. CONCLUSIONS: As the first investigational new drug targeting the underlying cause of nm-dystrophinopathy, ataluren offers promise as a treatment for this orphan genetic disorder with high unmet medical need.

Corticosteroids in Duchenne muscular dystrophy: major variations in practice.

INTRODUCTION: In 2004, a Cochrane Review and AAN practice parameter concluded that prednisone 0.75 mg/kg/day is of short-term efficacy in Duchenne muscular dystrophy (DMD). Subsequent efforts to standardize care for DMD indicated wide variation in corticosteroid use. METHODS: We surveyed physicians who follow patients with DMD, including: (1) clinics in the TREAT-NMD (Translational Research in Europe-Assessment and Treatment of Neuromuscular Diseases) network (predominantly Europe) and (2) U.S. MDA clinic directors. We also documented the co-administered corticosteroids in a trial of a putative treatment (ataluren) for DMD. RESULTS: Of 105 Treat-NMD clinicians, corticosteroids were not used in 10 clinics, and 29 different regimens were used--the most frequent 0.75 mg/kg/day prednisone (61 centers); 10 days on/10 days off (36 centers); 0.9 mg/kg/day deflazacort (32 centers); and 5 mg/kg/day on weekends (10 centers). Similar diversity was identified in MDA clinics and in the ataluren trial. CONCLUSIONS: Variability in corticosteroid use suggests uncertainty about risks/benefits of corticosteroid regimens for DMD.

The 6-minute walk test and other clinical endpoints in duchenne muscular dystrophy: reliability, concurrent validity, and minimal clinically important differences from a multicenter study.

INTRODUCTION: An international clinical trial enrolled 174 ambulatory males ≥5 years old with nonsense mutation Duchenne muscular dystrophy (nmDMD). Pretreatment data provide insight into reliability, concurrent validity, and minimal clinically important differences (MCIDs) of the 6-minute walk test (6MWT) and other endpoints. METHODS: Screening and baseline evaluations included the 6-minute walk distance (6MWD), timed function tests (TFTs), quantitative strength by myometry, the PedsQL, heart rate-determined energy expenditure index, and other exploratory endpoints. RESULTS: The 6MWT proved feasible and reliable in a multicenter context. Concurrent validity with other endpoints was excellent. The MCID for 6MWD was 28.5 and 31.7 meters based on 2 statistical distribution methods. CONCLUSIONS: The ratio of MCID to baseline mean is lower for 6MWD than for other endpoints. The 6MWD is an optimal primary endpoint for Duchenne muscular dystrophy (DMD) clinical trials that are focused therapeutically on preservation of ambulation and slowing of disease progression.

The 6-minute walk test and other endpoints in Duchenne muscular dystrophy: longitudinal natural history observations over 48 weeks from a multicenter study.

INTRODUCTION: Duchenne muscular dystrophy (DMD) subjects ≥5 years with nonsense mutations were followed for 48 weeks in a multicenter, randomized, double-blind, placebo-controlled trial of ataluren. Placebo arm data (N = 57) provided insight into the natural history of the 6-minute walk test (6MWT) and other endpoints. METHODS: Evaluations performed every 6 weeks included the 6-minute walk distance (6MWD), timed function tests (TFTs), and quantitative strength using hand-held myometry. RESULTS: Baseline age (≥7 years), 6MWD, and selected TFT performance are strong predictors of decline in ambulation (Δ6MWD) and time to 10% worsening in 6MWD. A baseline 6MWD of <350 meters was associated with greater functional decline, and loss of ambulation was only seen in those with baseline 6MWD <325 meters. Only 1 of 42 (2.3%) subjects able to stand from supine lost ambulation. CONCLUSION: Findings confirm the clinical meaningfulness of the 6MWD as the most accepted primary clinical endpoint in ambulatory DMD trials.

Ataluren (PTC124) induces cystic fibrosis transmembrane conductance regulator protein expression and activity in children with nonsense mutation cystic fibrosis.

RATIONALE: Nonsense (premature stop codon) mutations in mRNA for the cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis (CF) in approximately 10% of patients. Ataluren (PTC124) is an oral drug that permits ribosomes to readthrough premature stop codons in mRNA to produce functional protein. OBJECTIVES: To evaluate ataluren activity, safety, and pharmacokinetics in children with nonsense mutation CF. METHODS: Patients were assessed in two 28-day cycles, comprising 14 days on and 14 days off ataluren. Patients took ataluren three times per day (morning, midday, and evening) with randomization to the order of receiving a lower dose (4, 4, and 8 mg/kg) and a higher dose (10, 10, and 20 mg/kg) in the two cycles. MEASUREMENTS AND MAIN RESULTS: The study enrolled 30 patients (16 male and 14 female, ages 6 through 18 yr) with a nonsense mutation in at least one allele of the CFTR gene, a classical CF phenotype, and abnormal baseline nasal epithelial chloride transport. Ataluren induced a nasal chloride transport response (at least a -5-mV improvement) or hyperpolarization (value more electrically negative than -5 mV) in 50% and 47% of patients, respectively, with more hyperpolarizations at the higher dose. Improvements were seen in seven of nine nonsense mutation genotypes represented. Ataluren significantly increased the proportion of nasal epithelial cells expressing apical full-length CFTR protein. Adverse events and laboratory abnormalities were infrequent and usually mild. Ataluren pharmacokinetics were similar to those in adults. CONCLUSIONS: In children with nonsense mutation CF, ataluren can induce functional CFTR production and is well tolerated.

Meta-analyses of deflazacort versus prednisone/prednisolone in patients with nonsense mutation Duchenne muscular dystrophy.

Aim: Compare efficacies of deflazacort and prednisone/prednisolone in providing clinically meaningful delays in loss of physical milestones in patients with nonsense mutation Duchenne muscular dystrophy. Materials & methods: Placebo data from Phase IIb (ClinicalTrials.gov Identifier: NCT00592553) and ACT DMD (ClinicalTrials.gov Identifier: NCT01826487) ataluren nonsense mutation Duchenne muscular dystrophy clinical trials were retrospectively combined in meta-analyses (intent-to-treat population; for change from baseline to week 48 in 6-min walk distance [6MWD] and timed function tests). Results: Significant improvements in change in 6-min walk distance with deflazacort versus prednisone/prednisolone (least-squares mean difference 39.54 m [95% CI: 13.799, 65.286; p = 0.0026]). Significant and clinically meaningful improvements in 4-stair climb and 4-stair descend for deflazacort versus prednisone/prednisolone. Conclusion: Deflazacort provides clinically meaningful delays in loss of physical milestones over 48 weeks compared with prednisone/prednisolone for patients with nonsense mutation Duchenne muscular dystrophy.

The 6-minute walk test as a new outcome measure in Duchenne muscular dystrophy.

Walking abnormalities are prominent in Duchenne muscular dystrophy (DMD). We modified the 6-minute walk test (6MWT) for use as an outcome measure in patients with DMD and evaluated its performance in 21 ambulatory boys with DMD and 34 healthy boys, ages 4 to 12 years. Boys with DMD were tested twice, approximately 1 week apart; controls were tested once. The groups had similar age, height, and weight. All tests were completed. Boys who fell recovered rapidly from falls without injury. Mean +/- SD [range] 6-minute walk distance (6MWD) was lower in boys with DMD than in controls (366 +/- 83 [125-481] m vs. 621 +/- 68 [479-754] m; P < 0.0001; unpaired t-test). Test-retest correlation for boys with DMD was high (r = 0.91). Stride length (R(2) = 0.89; P < 0.0001) was the major determinant of 6MWD for both boys with DMD and controls. A modified 6MWT is feasible and safe, documents disease-related limitations on ambulation, is reproducible, and offers a new outcome measure for DMD natural history and therapeutic trials.

The 6-minute walk test in Duchenne/Becker muscular dystrophy: longitudinal observations.

In this study we used the 6-minute walk distance (6MWD) to characterize ambulation over time in Duchenne/Becker muscular dystrophy (DBMD). The 6MWD was assessed in 18 boys with DBMD and 22 healthy boys, ages 4-12 years, over mean [range] intervals of 58 [39-87] and 69 [52-113] weeks, respectively. Height and weight increased similarly in both groups. At 52 weeks, 6MWD decreased in 12 of 18 (67%) DBMD subjects (overall mean [range]: 357 [125-481] to 300 [0-510] meters; Δ -57 meters, -15.9%), but increased in 14 of 22 (64%) healthy subjects (overall mean [range]: 623 [479-754] to 636 [547-717] meters; Δ +13 meters, +2.1%). Two DBMD subjects lost ambulation. Changes in 6MWD depended on stride length and age; improvements usually occurred by 7-8 years of age; older DBMD subjects worsened, whereas older healthy subjects were stable. The 6MWD changes at 1 year confirm the validity of this endpoint and emphasize that preserving ambulation must remain a major goal of DBMD therapy.

Longitudinal Evaluation of Working Memory in Duchenne Muscular Dystrophy.

Objective: The developmental maturation of forward and backward digit spans-indices of working memory-in boys with nonsense (nm) Duchenne muscular dystrophy (DMD) (nmDMD) was assessed using prospective, longitudinal data. Methods: Fifty-five boys of the 57 subjects with genetically confirmed nmDMD-who were from the placebo arm of a 48-week-long phase 2b clinical trial-were evaluated. Forward and backward digit spans were obtained every 12 weeks for a total of five assessments in all study subjects. Changes in forward and backward digit spans were evaluated based on age, corticosteroid treatment, and DMD mutation location. Results: Boys with nmDMD had lower mean scores on normalized forward digit span. Normalized forward digit spans were comparable between subjects stratified by age and between corticosteroid-naïve and corticosteroid-treated subjects. When stratified by DMD mutation location, normalized forward digit spans were lower in nmDMD subjects with mutations downstream of DMD exon 30, exon 45, and exon 63, both at baseline evaluation and at follow-up evaluation at 48 weeks. On average, normalized backward digit span scores were stable over 48 weeks in these subjects. Developmental growth modeling showed that subjects with nmDMD mutations upstream of DMD exon 30, upstream of DMD exon 45, and upstream of DMD exon 63 appeared to make better gains in working memory than subjects with mutations downstream of DMD exon 30, downstream of DMD exon 45, and downstream of DMD exon 63. Conclusion: Performance in working memory shows deficits in nmDMD and differed based on nmDMD location. Maturation in cognition was seen over a 48-week period. The developmental trajectory of working memory in this cohort was influenced by DMD mutation location.

Meta-analyses of ataluren randomized controlled trials in nonsense mutation Duchenne muscular dystrophy.

Aim: Assess the totality of efficacy evidence for ataluren in patients with nonsense mutation Duchenne muscular dystrophy (nmDMD). Materials & methods: Data from the two completed randomized controlled trials (ClinicalTrials.gov: NCT00592553; NCT01826487) of ataluren in nmDMD were combined to examine the intent-to-treat (ITT) populations and two patient subgroups (baseline 6-min walk distance [6MWD] ≥300-<400 or <400 m). Meta-analyses examined 6MWD change from baseline to week 48. Results: Statistically significant differences in 6MWD change with ataluren versus placebo were observed across all three meta-analyses. Least-squares mean difference (95% CI): ITT (n = 342), +17.2 (0.2-34.1) m, p = 0.0473; ≥300-<400 m (n = 143), +43.9 (18.2-69.6) m, p = 0.0008; <400 m (n = 216), +27.7 (6.4-49.0) m, p = 0.0109. Conclusion: These meta-analyses support previous evidence for ataluren in slowing disease progression versus placebo in patients with nmDMD over 48 weeks. Treatment benefit was most evident in patients with a baseline 6MWD ≥300-<400 m (the ambulatory transition phase), thereby informing future trial design.

Effectiveness of PTC124 treatment of cystic fibrosis caused by nonsense mutations: a prospective phase II trial.

BACKGROUND: In about 10% of patients worldwide and more than 50% of patients in Israel, cystic fibrosis results from nonsense mutations (premature stop codons) in the messenger RNA (mRNA) for the cystic fibrosis transmembrane conductance regulator (CFTR). PTC124 is an orally bioavailable small molecule that is designed to induce ribosomes to selectively read through premature stop codons during mRNA translation, to produce functional CFTR. METHODS: This phase II prospective trial recruited adults with cystic fibrosis who had at least one nonsense mutation in the CFTR gene. Patients were assessed in two 28-day cycles. During the first cycle, patients received PTC124 at 16 mg/kg per day in three doses every day for 14 days, followed by 14 days without treatment; in the second cycle, patients received 40 mg/kg of PTC124 in three doses every day for 14 days, followed by 14 days without treatment. The primary outcome had three components: change in CFTR-mediated total chloride transport; proportion of patients who responded to treatment; and normalisation of chloride transport, as assessed by transepithelial nasal potential difference (PD) at baseline, at the end of each 14-day treatment course, and after 14 days without treatment. The trial was registered with who.int/ictrp, and with clinicaltrials.gov, number NCT00237380. FINDINGS: Transepithelial nasal PD was evaluated in 23 patients in the first cycle and in 21 patients in the second cycle. Mean total chloride transport increased in the first treatment phase, with a change of -7.1 (SD 7.0) mV (p<0.0001), and in the second, with a change of -3.7 (SD 7.3) mV (p=0.032). We recorded a response in total chloride transport (defined as a change in nasal PD of -5 mV or more) in 16 of the 23 patients in the first cycle's treatment phase (p<0.0001) and in eight of the 21 patients in the second cycle (p<0.0001). Total chloride transport entered the normal range for 13 of 23 patients in the first cycle's treatment phase (p=0.0003) and for nine of 21 in the second cycle (p=0.02). Two patients given PTC124 had constipation without intestinal obstruction, and four had mild dysuria. No drug-related serious adverse events were recorded. INTERPRETATION: In patients with cystic fibrosis who have a premature stop codon in the CFTR gene, oral administration of PTC124 to suppress nonsense mutations reduces the epithelial electrophysiological abnormalities caused by CFTR dysfunction.

Ataluren use in patients with nonsense mutation Duchenne muscular dystrophy: patient demographics and characteristics from the STRIDE Registry.

Aim: Strategic Targeting of Registries and International Database of Excellence (STRIDE) is an ongoing, multicenter registry providing real-world evidence regarding ataluren use in patients with nonsense mutation Duchenne muscular dystrophy (DMD) in clinical practice (NCT02369731). Here, we describe the initial demographic characteristics of the registry population. Patients & methods: Patients will be followed up from enrollment for ≥5 years or until study withdrawal. Results & conclusion: As of 9 July 2018, 213 DMD boys were enrolled from 11 countries. Mean (standard deviation) ages at first symptoms and at study treatment start were 2.7 (1.7) years and 9.8 (3.7) years, respectively. Corticosteroids were used by 190 patients (89.2%) before data cut-off. Mean (standard deviation) ataluren exposure was 639.0 (362.9) days. Six patients withdrew. STRIDE is the first drug registry for patients with DMD and represents the largest real-world registry of patients with nmDMD to date.

The relationship between deficit in digit span and genotype in nonsense mutation Duchenne muscular dystrophy.

OBJECTIVE: To evaluate the relationship between deficit in digit span and genotype in nonsense mutation (nm) Duchenne muscular dystrophy (DMD) (nmDMD). METHODS: We investigated the relationship between normalized digit-span forward (d-sf) and digit-span backward (d-sb) scores to the location of nmDMD mutations in 169 participants ≥5 to ≤20 years who participated in a phase 2b clinical trial. Because alternative promoters are found upstream of DMD exons 30, 45, and 63, we correlated d-sf and d-sb to the specific nmDMD mutation location. RESULTS: Participants with nm downstream of exon 30, downstream of exon 45, and downstream of exon 63 had significantly lower normalized d-sf scores (p < 0.0001). Participants with nm downstream of exon 45 in addition had significantly lower normalized d-sb score (p < 0.04). There was no significant difference in the normalized d-sb score in participants with mutations upstream or downstream of DMD exon 30 or upstream or downstream of DMD exon 63. CONCLUSION: Our data provide evidence that specific cognitive deficits correlate to genotype in individuals with nmDMD, highlighting the critical role of brain-specific dystrophin isoforms in the neurobiological manifestations of this disease. CLINICALTRIALSGOV IDENTIFIER: NCT02090959.

The minor gentamicin complex component, X2, is a potent premature stop codon readthrough molecule with therapeutic potential.

Nonsense mutations, resulting in a premature stop codon in the open reading frame of mRNAs are responsible for thousands of inherited diseases. Readthrough of premature stop codons by small molecule drugs has emerged as a promising therapeutic approach to treat disorders resulting from premature termination of translation. The aminoglycoside antibiotics are a class of molecule known to promote readthrough at premature termination codons. Gentamicin consists of a mixture of major and minor aminoglycoside components. Here, we investigated the readthrough activities of the individual components and show that each of the four major gentamicin complex components representing 92-99% of the complex each had similar potency and activity to that of the complex itself. In contrast, a minor component (gentamicin X2) was found to be the most potent and active readthrough component in the gentamicin complex. The known oto- and nephrotoxicity associated with aminoglycosides preclude long-term use as readthrough agents. Thus, we evaluated the components of the gentamicin complex as well as the so-called "designer" aminoglycoside, NB124, for in vitro and in vivo safety. In cells, we observed that gentamicin X2 had a safety/readthrough ratio (cytotoxicity/readthrough potency) superior to that of gentamicin, G418 or NB124. In rodents, we observed that gentamicin X2 showed a safety profile that was superior to G418 overall including reduced nephrotoxicity. These results support further investigation of gentamicin X2 as a therapeutic readthrough agent.

Safety, tolerability, and pharmacokinetics of PTC124, a nonaminoglycoside nonsense mutation suppressor, following single- and multiple-dose administration to healthy male and female adult volunteers.

Nonsense (premature stop codon) mutations are causative in 5% to 15% of patients with monogenetic inherited disorders. PTC124, a 284-Dalton 1,2,4-oxadiazole, promotes ribosomal readthrough of premature stop codons in mRNA and offers therapeutic potential for multiple genetic diseases. The authors conducted 2 phase I studies of PTC124 in 62 healthy adult volunteers. The initial, single-dose study evaluated doses of 3 to 200 mg/kg and assessed fed-fasting status on pharmacokinetics following a dose of 50 mg/kg. The subsequent multiple-dose study evaluated doses from 10 to 50 mg/kg/dose twice per day (bid) for up to 14 days. PTC124 administered orally as a liquid suspension was palatable and well tolerated through single doses of 100 mg/kg. At 150 and 200 mg/kg, PTC124 induced mild headache, dizziness, and gastrointestinal events. With repeated doses through 50 mg/kg/dose bid, reversible transaminase elevations <2 times the upper limit of normal were sometimes observed. Immunoblot analyses of peripheral blood mononuclear cell extracts revealed no protein elongation due to nonspecific ribosomal readthrough of normal stop codons. PTC124 plasma concentrations exceeding the 2- to 10-microg/mL values associated with activity in preclinical genetic disease models were safely achieved. No sex-related differences in pharmacokinetics were seen. No drug accumulation with repeated dosing was apparent. Diurnal variation was observed, with greater PTC124 exposures after evening doses. PTC124 excretion in the urine was <2%. PTC124 pharmacokinetics were described by a 1-compartment model. Collectively, the data support initiation of phase II studies of PTC124 in patients with nonsense mutation-mediated cystic fibrosis and Duchenne muscular dystrophy.

Phase 1 and pharmacokinetic study of intravenous irinotecan in refractory solid tumor patients with hepatic dysfunction.

PURPOSE: To determine the recommended starting doses and pharmacokinetics of irinotecan in cancer patients with impaired liver function treated on a weekly schedule. EXPERIMENTAL DESIGN: Patients with solid tumors who had impaired liver function were enrolled into four groups based on baseline serum total bilirubin and aspartate aminotransferase (AST)/alanine aminotransferase (ALT): Group 1 (n = 19): total bilirubin 1.5 to 3.0 x institutional upper limit of normal (IULN) and ALT/AST