Relationship between quantitative strength and functional outcomes in the phase 2 FORTITUDE-ALS trial.

OBJECTIVE: To assess the relationship among measurements of strength, function, and quality of life in an amyotrophic lateral sclerosis (ALS) clinical trial. METHODS: In the FORTITUDE-ALS clinical trial (NCT03160898), 456 participants in the full-analysis set were treated with either reldesemtiv or placebo for 12 weeks; this post hoc analysis included all participants regardless of treatment assignments. Assessments included slow vital capacity (SVC), the ALS Functional Rating Scale-Revised (ALSFRS-R), and the 5-item ALS Assessment Questionnaire (ALSAQ-5). Muscle strength was measured quantitatively with hand-held dynamometry, and grip strength with a dedicated dynamometer. The relationship between strength and ALSFRS-R fine and gross motor domain scores, or responses to ALSAQ-5 questions on hand function and walking, was assessed with Spearman's rank correlation. The relationship between mean upper- or lower-extremity muscle strength and specific ALSFRS-R domains was modeled using principal-components analysis. RESULTS: Upper-extremity muscle strength and hand grip were highly correlated with ALSFRS-R fine motor scores and the ALSAQ-5 hand function question. Similarly, lower-extremity strength correlated well with ALSFRS-R gross motor domain and the ALSAQ-5 walking question. For SVC, correlation was poor with the ALSFRS-R respiratory domain, but stronger with the total score, potentially reflecting the insensitivity of the respiratory questions in the scale. Upper- and lower-extremity strength were both strong predictors of ALSFRS-R domain scores. CONCLUSIONS: In this analysis of data from an ALS clinical trial, muscle strength quantified by dynamometry was strongly correlated with functional capacity. These results suggest that muscle strength directly relates to specific functions of importance to people with ALS.

COURAGE-ALS: a randomized, double-blind phase 3 study designed to improve participant experience and increase the probability of success.

Objective: To determine the target population and optimize the study design of the phase 3 clinical trial evaluating reldesemtiv in participants with amyotrophic lateral sclerosis (ALS).Methods: We evaluated the phase 2 study of reldesemtiv, FORTITUDE-ALS, to inform eligibility criteria and design features that would increase trial efficiency and reduce participant burden of the phase 3 trial.Results: In FORTITUDE-ALS, the effect of reldesemtiv was particularly evident among participants in the intermediate- and fast-progressing tertiles for pre-study disease progression. These participants most often had symptom onset ≤24 months and an ALS Functional Rating Scale-Revised (ALSFRS-R) total score ≤44 at baseline. Compared with the overall FORTITUDE-ALS population, the subgroup meeting these criteria declined by fewer ALSFRS-R points at 12 weeks (difference of least-squares mean [SE] versus placebo 1.84 [0.49] and 0.87 [0.35] for the overall population). These inclusion criteria will be used for the phase 3 clinical trial, COURAGE-ALS, in which the primary outcome is the change in ALSFRS-R total score at week 24. We also measure durable medical equipment use and evaluate strength in muscles expected to change rapidly. To reduce participant burden, study visits are often remote, and strength evaluation is simplified to reduce time and effort.Conclusions: In COURAGE-ALS, the phase 3 clinical trial to evaluate reldesemtiv, the sensitivity of detecting a potential treatment effect may be increased by defining eligibility criteria that limit the proportion of participants who have slower disease progression. Implementing remote visits and simplifying strength measurements will reduce both site and participant burden.ClinicalTrials.gov identifiers: NCT03160898 (FORTITUDE-ALS) and NCT04944784 (COURAGE-ALS).

Health utilities and quality-adjusted life years for patients with amyotrophic lateral sclerosis receiving reldesemtiv or placebo in FORTITUDE-ALS.

AIMS: To estimate the health utilities and quality-adjusted life years (QALYs) in patients with amyotrophic lateral sclerosis (ALS) receiving reldesemtiv versus placebo in FORTITUDE-ALS. MATERIALS AND METHODS: We performed a post hoc analysis of clinical trial data from FORTITUDE-ALS (NCT03160898). This Phase IIb, double-blind, randomized, dose-ranging, placebo-controlled, parallel-group, 12-week trial evaluated reldesemtiv in patients with ALS. Health utilities from the five-level version of the EuroQol five-dimensional questionnaire (EQ-5D-5L) were estimated using ALS Functional Rating Scale-Revised (ALSFRS-R) scores collected during the trial. QALYs were estimated using the area under the curve method. RESULTS: The full analysis set consisted of 456 patients (reldesemtiv n = 342, placebo n = 114), who received at least one dose of the double-blind study drug, and had ALSFRS-R assessed at baseline and at least one post-baseline assessment. The difference in EQ-5D-5L utility least-squares (LS) mean change from baseline to week 12 for reldesemtiv versus placebo, adjusted for baseline values, was statistically significant (0.03, 95% confidence interval [CI]: 0.01, 0.05; p = .0008). The incremental QALY of reldesemtiv versus placebo adjusted for baseline utility values showed a modest, but statistically significant, difference (0.004, 95% CI: 0.001, 0.007; p = .0058). CONCLUSIONS: This post hoc analysis of FORTITUDE-ALS suggests that reldesemtiv showed a modest but significant benefit in health utilities and QALYs compared with placebo. Future long-term studies that include direct collection of EQ-5D-5L data will be needed to confirm our findings. CLINICALTRIALS.GOV IDENTIFIER: NCT03160898.

MiToS and King's staging as clinical outcome measures in ALS: a retrospective analysis of the FORTITUDE-ALS trial.

OBJECTIVE: To evaluate the Milano-Torino staging (MiToS) and King's staging systems as potential outcome measures for clinical trials in amyotrophic lateral sclerosis (ALS) by assessing these outcomes in FORTITUDE-ALS. METHODS: This was a post hoc analysis of the phase 2b FORTITUDE-ALS trial (NCT03160898), a double-blind, randomized, dose-ranging, placebo-controlled, parallel-group study of reldesemtiv in patients with ALS. The treatment period was 12 weeks, with a follow-up assessment at week 16. Patients were retrospectively classified into MiToS and King's stages. Outcomes were the mean time maintaining baseline stage and risk of progression from the baseline stage to a later stage. RESULTS: The full analysis set consisted of 456 patients randomized 3:1 (reldesemtiv n = 342, placebo n = 114) who received at least one dose of double-blind study drug and had at least one post-baseline assessment. At baseline, MiToS and King's stages were balanced between the reldesemtiv and placebo groups: >99% of patients were in MiToS stage 0 or 1 and King's stage 1, 2 or 3. Time of maintaining the baseline stage was similar in both groups, for each staging system. The two staging systems exhibited considerably disparate results for risk of progression from baseline to a later stage: hazard ratio (HR) = 0.62 (95% confidence interval [CI] 0.38, 0.99) for MiToS and HR = 0.96 (95% CI 0.63, 1.44) for King's. CONCLUSION: This exploratory analysis showed the feasibility of MiToS and King's staging as potential outcome measures in ALS. Additional studies of these staging systems are needed to further explore their utility in ALS clinical trials.

Prescription and acceptance of durable medical equipment in FORTITUDE-ALS, a study of reldesemtiv in ALS: post hoc analyses of a randomized, double-blind, placebo-controlled clinical trial.

Objective: To evaluate the possible effect of reldesemtiv, a fast skeletal muscle troponin activator, on prescription and acceptance of durable medical equipment (DME) in the FORTITUDE-ALS trial. Methods: Health economic outcome information was collected in FORTITUDE-ALS (NCT03160898); sites recorded if and when DME, specifically manual or power wheelchairs, gastrostomy tubes, noninvasive ventilators, or augmentative language devices, was prescribed by a physician and accepted by the patient (DME-PAP) during the trial. Acceptance was defined as the patient agreeing the item was needed. Cox regression analysis compared time to DME-PAP for each reldesemtiv dose with placebo. Post hoc analyses evaluated all reldesemtiv doses compared with placebo. Results: At least one DME item was prescribed and accepted by 33/114 (28.9%) of placebo patients, 19/112 (17.0%) of patients receiving reldesemtiv 150 mg bid, 24/113 (21.2%) receiving 300 mg bid, and 29/117 (24.8%) receiving 450 mg bid. The proportion of new DME-PAP was significantly lower in patients receiving reldesemtiv 150 mg bid vs placebo (17.0% vs 28.9%, p = 0.032). The hazard ratio versus placebo for accepting at least one DME item for all reldesemtiv doses combined was 0.61 (confidence interval: 0.39, 0.96, p = 0.032). 25% of placebo patients were prescribed and agreed to obtain a DME item by 84 days; this threshold was met for reldesemtiv-treated patients at 120 days. Conclusions: Results suggest ALS patients receiving reldesemtiv may have lower risk of and delayed need for DME related to impaired mobility, breathing, swallowing, or speaking; this delay is consistent with other measures indicating delay in disease progression.

Noninvasive ventilation use by patients enrolled in VITALITY-ALS.

Objectives: To evaluate the prescribing practices of noninvasive ventilation (NIV) and patient compliance during VITALITY-ALS. Methods: VITALITY-ALS enrolled patients with a slow vital capacity (SVC) ≥70% of predicted who were not using NIV at screening. Physicians prescribed NIV without restriction following randomization. Reason(s) for NIV prescription, dates prescribed and initiated, and compliance were recorded. Compliance was recorded as prescribed but never initiated, used ≥2 h/24 h, used ≥4 h/24 h, or used ≥22 h/24 h. In addition to other outcome measures, SVC and the revised ALS functional rating scale (ALSFRS-R) were performed at all visits. Patients were followed up to 56 weeks. Results: 565 patients were randomized and dosed with placebo or tirasemtiv in VITALITY-ALS; 195 (34.5%) were prescribed NIV: of these, 78.5% used it for ≥2 h/24 h, 71.3% for ≥4 h/24 h, and 11.8% for ≥22 h/24 h. The three most common reasons NIV was prescribed were decline in vital capacity, respiratory symptoms, and sleep-related symptoms. During the trial, 179/565 (31.7%) patients had a decline of SVC below 50%; of these patients, 122/179 (68.2%) were prescribed NIV. Reasons for prescribing NIV were different for patients from North America compared with Europe. Conclusions: Despite allowing for NIV initiation at any point following randomization in VITALITY-ALS, only slightly more than two out of three patients whose SVC fell below 50% were prescribed NIV; this was similar in Europe and in North America. Underutilization of NIV could influence survival outcomes in patients with ALS including those involved in clinical trials.

Reldesemtiv in Patients with Spinal Muscular Atrophy: a Phase 2 Hypothesis-Generating Study.

This phase 2, double-blind, placebo-controlled, hypothesis-generating study evaluated the effects of oral reldesemtiv, a fast skeletal muscle troponin activator, in patients with spinal muscular atrophy (SMA). Patients ≥ 12 years of age with type II, III, or IV SMA were randomized into 2 sequential, ascending reldesemtiv dosing cohorts (cohort 1: 150 mg bid or placebo [2:1]; cohort 2: 450 mg bid or placebo [2:1]). The primary objective was to determine potential pharmacodynamic effects of reldesemtiv on 8 outcome measures in SMA, including 6-minute walk distance (6MWD) and maximum expiratory pressure (MEP). Changes from baseline to weeks 4 and 8 were determined. Pharmacokinetics and safety were also evaluated. Patients were randomized to reldesemtiv 150 mg, 450 mg, or placebo (24, 20, and 26, respectively). The change from baseline in 6MWD was greater for reldesemtiv 450 mg than for placebo at weeks 4 and 8 (least squares [LS] mean difference, 35.6 m [p = 0.0037] and 24.9 m [p = 0.058], respectively). Changes from baseline in MEP at week 8 on reldesemtiv 150 and 450 mg were significantly greater than those on placebo (LS mean differences, 11.7 [p = 0.038] and 13.2 cm H2O [p = 0.03], respectively). For 6MWD and MEP, significant changes from placebo were seen in the highest reldesemtiv peak plasma concentration quartile (Cmax > 3.29 µg/mL; LS mean differences, 43.3 m [p = 0.010] and 28.8 cm H2O [p = 0.0002], respectively). Both dose levels of reldesemtiv were well tolerated. Results suggest reldesemtiv may offer clinical benefit and support evaluation in larger SMA patient populations.

A Phase 2, Double-Blind, Randomized, Dose-Ranging Trial Of Reldesemtiv In Patients With ALS.

OBJECTIVE: To evaluate safety, dose response, and preliminary efficacy of reldesemtiv over 12 weeks in patients with amyotrophic lateral sclerosis (ALS). Methods: Patients (≤2 years since diagnosis) with slow upright vital capacity (SVC) of ≥60% were randomized 1:1:1:1 to reldesemtiv 150, 300, or 450 mg twice daily (bid) or placebo; active treatment was 12 weeks with 4-week follow-up. Primary endpoint was change in percent predicted SVC at 12 weeks; secondary measures included ALS Functional Rating Scale-Revised (ALSFRS-R) and muscle strength mega-score. Results: Patients (N = 458) were enrolled; 85% completed 12-week treatment. The primary analysis failed to reach statistical significance (p = 0.11); secondary endpoints showed no statistically significant effects (ALSFRS-R, p = 0.09; muscle strength mega-score, p = 0.31). Post hoc analyses pooling all active reldesemtiv-treated patients compared against placebo showed trends toward benefit in all endpoints (progression rate for SVC, ALSFRS-R, and muscle strength mega-score (nominal p values of 0.10, 0.01 and 0.20 respectively)). Reldesemtiv was well tolerated, with nausea and fatigue being the most common side effects. A dose-dependent decrease in estimated glomerular filtration rate was noted, and transaminase elevations were seen in approximately 5% of patients. Both hepatic and renal abnormalities trended toward resolution after study drug discontinuation. Conclusions: Although the primary efficacy analysis did not demonstrate statistical significance, there were trends favoring reldesemtiv for all three endpoints, with effect sizes generally regarded as clinically important. Tolerability was good; modest hepatic and renal abnormalities were reversible. The impact of reldesemtiv on patients with ALS should be assessed in a pivotal Phase 3 trial. (ClinicalTrials.gov Identifier: NCT03160898).

A phase III trial of tirasemtiv as a potential treatment for amyotrophic lateral sclerosis.

Objective: To assess the efficacy of tirasemtiv, a fast skeletal muscle troponin activator, vs. placebo in patients with amyotrophic lateral sclerosis. Methods: VITALITY-ALS (NCT02496767) was a multinational, double-blind, randomized, placebo-controlled clinical trial. Participants tolerating 2 weeks of open-label tirasemtiv (125 mg twice daily) were randomized 3:2:2:2 to placebo or one of three target tirasemtiv dose levels, using an escalating dosage protocol lasting 28 days. The primary outcome measure was changed in slow vital capacity (SVC) at 24 weeks. Secondary endpoints included a change in muscle strength and time to respiratory milestones of disease progression. Results: Of 744 participants, 565 tolerated open-label tirasemtiv and received randomized treatment. By 24 weeks, 23 (12.2%) placebo-treated participants discontinued study treatment vs. 129 (34.2%) randomized to tirasemtiv. SVC declined by 14.4% (95% CI: −16.8, −11.9) in the placebo group and 13.4% (95% CI: −15.3, −11.6) in the tirasemtiv group (p = 0.56). Secondary endpoints did not show significant differences. However, participants who tolerated tirasemtiv at their randomized dose showed a numeric trend toward a dose-related slowing of decline in SVC (p = 0.11). Dizziness, fatigue, nausea, weight loss, and insomnia occurred more frequently on tirasemtiv. Serious adverse events were similar across groups. Conclusions: Tirasemtiv did not alter the decline of SVC or significantly impact secondary outcome measures. Poor tolerability of tirasemtiv may have contributed to this result. However, participants tolerating their intended dose exhibited a trend toward treatment benefit on SVC, suggesting the underlying mechanism of action may still hold promise, as is being tested with a different fast skeletal muscle troponin activator (NCT03160898).

Relationships between slow vital capacity and measures of respiratory function on the ALSFRS-R.

OBJECTIVE: As declining respiratory muscle function commonly leads to disability and death in amyotrophic lateral sclerosis (ALS), respiratory measurements such as slow vital capacity (SVC) may predict disease progression. This study evaluated the relationship between SVC and symptoms measured by the revised ALS Functional Rating Scale (ALSFRS-R). METHODS: About 453 ALS placebo-treated patients from the EMPOWER trial (NCT01281189) were evaluated. Correlations between %predicted SVC and individual respiratory ALSFRS-R subdomain items, respiratory subdomain score (maximum score of 12), and total ALSFRS-R score (maximum score of 48) were evaluated using the Pearson correlation coefficient. Pearson's chi-squared test was used to evaluate changes from baseline to week 48 in ALSFRS-R respiratory symptom and respiratory subdomain scores in patients with baseline %predicted SVC above/below the median at baseline and with more slowly/more rapidly decreasing %predicted SVC. RESULTS: The %predicted SVC showed significant correlations with dyspnea, orthopnoea, respiratory insufficiency, respiratory subdomain score, and total ALSFRS-R score (all p < 0.0001). Patients with baseline SVC values < median were significantly more likely than those with baseline SVC ≥ median to have a change in total ALSFRS-R respiratory subdomain score from 12 to <12 (40.9% vs. 30.2%, p = 0.0358) and from ≥10 to <10 (41.6% vs. 24.4%, p = 0.0005). Additionally, patients with smaller declines in SVC over time were significantly more likely to have smaller decreases in their respiratory subdomain scores (p < 0.0001). CONCLUSIONS: The higher correlation between %predicted SVC and specific ALSFRS-R symptom scores in patients with rapidly versus more slowly progressing disease reinforces the importance of continually monitoring respiratory function throughout the disease course.

VITALITY-ALS, a phase III trial of tirasemtiv, a selective fast skeletal muscle troponin activator, as a potential treatment for patients with amyotrophic lateral sclerosis: study design and baseline characteristics.

OBJECTIVE: To assess the efficacy of tirasemtiv, a fast skeletal muscle troponin activator, vs. placebo on respiratory function and other functional measures in patients with amyotrophic lateral sclerosis (ALS). This study was designed to confirm and extend results from a large phase IIb trial and maximize tolerability with a slower dose escalation. METHODS: VITALITY-ALS (NCT02496767) was a multinational, double-blind, randomized, placebo-controlled, parallel-group study in ALS patients. Participants who tolerated two weeks of open-label tirasemtiv (125 mg twice a day) were randomized 3:2:2:2 to placebo or one of three target total daily dose levels of tirasemtiv (250, 375, or 500 mg). Participants randomized to tirasemtiv escalated their dose every two weeks to their target dose level or maximum tolerated dose. The primary outcome measure was change in slow vital capacity from baseline to 24 weeks. Secondary endpoints assessed the effect of tirasemtiv on muscle strength and certain respiratory milestones of disease progression. A four-week randomized withdrawal phase followed 48 weeks of treatment to evaluate the possibility of sustained benefit or rebound decline. RESULTS: Data collection will be complete in the fourth quarter of 2017. CONCLUSIONS: VITALITY-ALS was a phase III trial designed to evaluate the efficacy, safety, and tolerability of tirasemtiv in ALS.

Association Between Decline in Slow Vital Capacity and Respiratory Insufficiency, Use of Assisted Ventilation, Tracheostomy, or Death in Patients With Amyotrophic Lateral Sclerosis.

Importance: The prognostic value of slow vital capacity (SVC) in relation to respiratory function decline and disease progression in patients with amyotrophic lateral sclerosis (ALS) is not well understood. Objective: To investigate the rate of decline in percentage predicted SVC and its association with respiratory-related clinical events and mortality in patients with ALS. Design, Setting, and Participants: This retrospective study included 893 placebo-treated patients from 2 large clinical trials (EMPOWER and BENEFIT-ALS, conducted from March 28, 2011, to November 1, 2012, and from October 23, 2012, to March 21, 2014, respectively) and an ALS trial database (PRO-ACT, containing studies completed between 1990 and 2010) to investigate the rate of decline in SVC. Data from the EMPOWER trial (which enrolled adults with possible, probable, or definite ALS; symptom onset within 24 months before screening; and upright SVC at least 65% of predicted value for age, height, and sex) were used to assess the relationship of SVC to respiratory-related clinical events; 456 patients randomized to placebo were used in this analysis. The 2 clinical trials included patients from North America, Australia, and Europe. Main Outcomes and Measures: Clinical events included the earlier of time to death or time to decline in the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) respiratory subdomain, time to onset of respiratory insufficiency, time to tracheostomy, and all-cause mortality. Results: Among 893 placebo-treated patients with ALS, the mean (SD) patient age was 56.7 (11.2) years, and the mean (SD) SVC was 90.5% (17.1%) at baseline; 65.5% (585 of 893) were male, and 20.5% (183 of 893) had bulbar-onset ALS. In EMPOWER, average decline of SVC from baseline through 1.5-year follow-up was -2.7 percentage points per month. Steeper declines were found in patients older than 65 years (-3.6 percentage points per month [P = .005 vs <50 years and P = .007 vs 50-65 years) and in patients with an ALSFRS-R total score of 39 or less at baseline (-3.1 percentage points per month [P < .001 vs >39]). When the rate of decline of SVC was slower by 1.5 percentage points per month in the first 6 months, risk reductions for events after 6 months were 19% for decline in the ALSFRS-R respiratory subdomain or death after 6 months, 22% for first onset of respiratory insufficiency or death after 6 months, 23% for first occurrence of tracheostomy or death after 6 months, and 23% for death at any time after 6 months (P < .001 for all). Conclusions and Relevance: The rate of decline in SVC is associated with meaningful clinical events in ALS, including respiratory failure, tracheostomy, or death, suggesting that it is an important indicator of clinical progression.

CK-2127107 amplifies skeletal muscle response to nerve activation in humans.

INTRODUCTION: Three studies evaluated safety, tolerability, pharmacokinetics, and pharmacodynamics of CK-2127107 (CK-107), a next-generation fast skeletal muscle troponin activator (FSTA), in healthy participants. We tested the hypothesis that CK-107 would amplify the force-frequency response of muscle in humans. METHODS: To assess the force-frequency response, participants received single doses of CK-107 and placebo in a randomized, double-blind, 4-period, crossover study. The force-frequency response of foot dorsiflexion following stimulation of the deep fibular nerve to activate the tibialis anterior muscle was assessed. RESULTS: CK-107 significantly increased tibialis anterior muscle response with increasing dose and plasma concentration in a frequency-dependent manner; the largest increase in peak force was ∼60% at 10 Hz. DISCUSSION: CK-107 appears more potent and produced larger increases in force than tirasemtiv-a first-generation FSTA-in a similar pharmacodynamic study, thereby supporting its development for improvement of muscle function of patients. Muscle Nerve 57: 729-734, 2018.

Acute Treatment With Omecamtiv Mecarbil to Increase Contractility in Acute Heart Failure: The ATOMIC-AHF Study.

BACKGROUND: Omecamtiv mecarbil (OM) is a selective cardiac myosin activator that increases myocardial function in healthy volunteers and in patients with chronic heart failure. OBJECTIVES: This study evaluated the pharmacokinetics, pharmacodynamics, tolerability, safety, and efficacy of OM in patients with acute heart failure (AHF). METHODS: Patients admitted for AHF with left ventricular ejection fraction ≤40%, dyspnea, and elevated plasma concentrations of natriuretic peptides were randomized to receive a double-blind, 48-h intravenous infusion of placebo or OM in 3 sequential, escalating-dose cohorts. RESULTS: In 606 patients, OM did not improve the primary endpoint of dyspnea relief (3 OM dose groups and pooled placebo: placebo, 41%; OM cohort 1, 42%; cohort 2, 47%; cohort 3, 51%; p = 0.33) or any of the secondary outcomes studied. In supplemental, pre-specified analyses, OM resulted in greater dyspnea relief at 48 h (placebo, 37% vs. OM, 51%; p = 0.034) and through 5 days (p = 0.038) in the high-dose cohort. OM exerted plasma concentration-related increases in left ventricular systolic ejection time (p < 0.0001) and decreases in end-systolic dimension (p < 0.05). The adverse event profile and tolerability of OM were similar to those of placebo, without increases in ventricular or supraventricular tachyarrhythmias. Plasma troponin concentrations were higher in OM-treated patients compared with placebo (median difference at 48 h, 0.004 ng/ml), but with no obvious relationship with OM concentration (p = 0.95). CONCLUSIONS: In patients with AHF, intravenous OM did not meet the primary endpoint of dyspnea improvement, but it was generally well tolerated, it increased systolic ejection time, and it may have improved dyspnea in the high-dose group. (Acute Treatment with Omecamtiv Mecarbil to Increase Contractility in Acute Heart Failure [ATOMIC-AHF]; NCT01300013).

A randomized, placebo-controlled, double-blind phase IIb trial evaluating the safety and efficacy of tirasemtiv in patients with amyotrophic lateral sclerosis.

Our objectives were to evaluate the safety and tolerability of tirasemtiv over 12 weeks and its effect on the revised ALS Functional Rating Scale (ALSFRS-R) and other secondary functional measures. This randomized, double-blind, placebo-controlled trial enrolled adults with ALS and slow vital capacity (SVC) > 50% from 73 centers in eight countries. Patients who tolerated open-label tirasemtiv 125 mg b.i.d. for one week were randomized to double-blind treatment either to placebo or tirasemtiv, escalating to a maximum tolerated dose up to 250 mg b.i.d. The primary endpoint was the change from baseline in ALSFRS-R; secondary endpoints included SVC, maximum voluntary ventilation, sniff nasal inspiratory pressure, isometric muscle strength, and sub-maximum handgrip fatigue. Of 711 patients enrolled, 596 were randomized and received at least one dose of double-blind treatment. The primary endpoint showed no treatment effect (tirasemtiv: -2.98 ± 0.28, placebo: -2.40 ± 0.25, p = 0.114); however, SVC and muscle strength declined significantly more slowly on tirasemtiv (95% CI p = 0.0006, p = 0.0158, respectively). Dropouts and serious adverse events occurred more frequently in the tirasemtiv group. In conclusion, this was a negative study with respect to the primary endpoint; however, the effects on SVC and muscle strength suggest a potentially important effect of tirasemtiv warranting further evaluation over a longer period in ALS.

Safety and tolerability of omecamtiv mecarbil during exercise in patients with ischemic cardiomyopathy and angina.

OBJECTIVES: The goal of this study was to assess the safety and tolerability of omecamtiv mecarbil treatment during symptom-limited exercise in patients with ischemic cardiomyopathy and angina. These patients may have increased vulnerability to prolongation of the systolic ejection time. BACKGROUND: Omecamtiv mecarbil is a selective cardiac myosin activator that augments cardiac contractility in patients with systolic heart failure through a dose-dependent increase in systolic ejection time. METHODS: In this double-blind, placebo-controlled study, patients with chronic heart failure were randomized 2:1 to receive omecamtiv mecarbil or placebo in 2 sequential cohorts of escalating doses designed to achieve plasma concentrations previously shown to increase systolic function. Patients underwent 2 symptom-limited exercise treadmill tests (ETTs) at baseline (ETT1 and ETT2) and again before the end of a 20-h infusion of omecamtiv mecarbil (ETT3). RESULTS: The primary pre-defined safety endpoint (i.e., the proportion of patients who stopped ETT3 because of angina at a stage earlier than baseline) was observed in 1 patient receiving placebo and none receiving omecamtiv mecarbil. No dose-dependent differences emerged in the proportion of patients stopping ETT3 for any reason or in the pattern of adverse events. CONCLUSIONS: Doses of omecamtiv mecarbil producing plasma concentrations previously shown to increase systolic function were well tolerated during exercise in these study patients with ischemic cardiomyopathy and angina. There was no indication that treatment increased the likelihood of myocardial ischemia in this high-risk population. (Pharmacokinetics [PK] and Tolerability of Intravenous [IV] and Oral CK-1827452 in Patients With Ischemic Cardiomyopathy and Angina; NCT00682565).

Effect of tirasemtiv, a selective activator of the fast skeletal muscle troponin complex, in patients with peripheral artery disease.

Tirasemtiv (CK-2017357), a novel small-molecule activator of the fast skeletal muscle troponin complex, slows the rate of calcium release from troponin, thus sensitizing fast skeletal muscle fibers to calcium. In preclinical studies, tirasemtiv increased muscle force and delayed the onset and reduced the extent of muscle fatigue during hypoxia in vitro and muscle ischemia in situ. This study evaluated the effect of single doses of tirasemtiv on measures of skeletal muscle function and fatigability in patients with stable calf claudication due to peripheral artery disease (PAD). Sixty-one patients with an ankle-brachial index ≤0.90 in the leg with claudication received single double-blind doses of tirasemtiv 375 mg and 750 mg and matching placebo in random order about 1 week apart. After 33 patients were treated, the 750 mg dose was decreased to 500 mg due to adverse events and these dose groups were combined for analysis. On each study day, bilateral heel-raise testing was performed before and at 3 and 6 hours after dosing; a 6-minute walk test was performed at 4 hours after dosing. Claudicating calf muscle performance was increased at the highest dose and plasma concentration of tirasemtiv; however, the 6-minute walk distance decreased with both the dose and plasma concentration of tirasemtiv, possibly due to dose-related adverse events, particularly dizziness, that could impede walking ability. In conclusion, the mechanism of fast skeletal muscle troponin activation improved muscle function but not 6-minute walking distance in patients with claudication due to PAD. CLINICALTRIALSGOV IDENTIFIER NCT01131013:

Tirasemtiv amplifies skeletal muscle response to nerve activation in humans.

INTRODUCTION: In this study we tested the hypothesis that tirasemtiv, a selective fast skeletal muscle troponin activator that sensitizes the sarcomere to calcium, could amplify the response of muscle to neuromuscular input in humans. METHODS: Healthy men received tirasemtiv and placebo in a randomized, double-blind, 4-period, crossover design. The deep fibular nerve was stimulated transcutaneously to activate the tibialis anterior muscle and produce dorsiflexion of the foot. The force-frequency relationship of tibialis anterior dorsiflexion was assessed after dosing. RESULTS: Tirasemtiv increased force produced by the tibialis anterior in a dose-, concentration-, and frequency-dependent manner with the largest increases [up to 24.5% (SE 3.1), P < 0.0001] produced at subtetanic nerve stimulation frequencies (10 Hz). CONCLUSIONS: The data confirm that tirasemtiv amplifies the response of skeletal muscle to nerve input in humans. This outcome provides support for further studies of tirasemtiv as a potential therapy in conditions marked by diminished neuromuscular input.

The relationship between tirasemtiv serum concentration and functional outcomes in patients with ALS.

Tirasemtiv is a fast skeletal muscle activator that increases efficiency of muscle contraction. Both single and repeated dose studies suggested beneficial effects on measures of function, muscle strength and endurance. As the outcomes measured were identical in previous studies and the duration of all studies was 21 days or less, we pooled data from all studies and assessed the relationship between outcomes and plasma tirasemtiv concentration to assess consistency of observations as well as to increase sensitivity. We pooled data for ALSFRS-R, three pulmonary function measures, quantitative muscle strength, and submaximal handgrip endurance. Up to 855 values from 143 patients were plotted against tirasemtiv concentrations. Linear associations between tirasemtiv concentrations and changes from baseline of clinical measures were estimated using a repeated-measures mixed model. Trends toward improvement were noted in all measures except for vital capacity, despite the fact that time was not included as a factor so that any time-related decline acted to reduce the magnitude of any noted trend. In conclusion, tirasemtiv appears to have concentration-dependent beneficial effects on both function and measures of strength and endurance when administered for up to 21 days, even when time is eliminated as a cofactor. These findings further support the development of this agent in ALS.