Thorough QT Studies: Questions and Quandaries

Evaluation of cardiac parameters and other safety outcomes of brolucizumab treatment in patients with neovascular age-related macular degeneration

This was a prospective, single‐dose, single‐arm, open‐label, non‐randomized, multicenter clinical study to determine cardiovascular safety after a single brolucizumab 6 mg intravitreal injection in neovascular age‐related macular degeneration patients (N = 14). Electrocardiogram (ECG) data were collected at different time points using 12‐lead Holter and standard ECG, and patients were followed up to 8 days (end of study) for any signs of ocular and non‐ocular adverse events (AEs). No clinically meaningful changes were observed in cardiac parameters. No patient had a ≥30 msec change from baseline in heart rate–corrected QT using Fridericia's formula (QTcF), and no patient had a new QTcF value of ≥450 msec between 20 and 24 h after treatment. No deaths or serious AEs were reported during the study period. These results are in line with the absence of new cardiovascular safety signal based on the ECG recordings collected over the first year of the pivotal studies performed with brolucizumab in DME.

Trial Registration: ClinicalTrials.gov identifier: NCT03954626.

Importance of QT/RR hysteresis correction in studies of drug-induced QTc interval changes

QT/RR hysteresis and QT/RR adaptation are interlinked but separate physiological processes signifying how quickly and how much QT interval changes when heart rate changes, respectively. While QT interval duration is, as a rule, corrected for heart rate in terms of the QT/RR adaptation, the correction for QT/RR hysteresis is frequently omitted in studies of drug-induced QTc changes. This study used data from previously conducted thorough QT studies to investigate the extent of QTc errors caused by omitting the correction for QT/RR hysteresis, particularly in small clinical investigations. Statistical modeling approach was used to generate 11,000 simulated samples of 10-subject studies in which mixed effect PK/PD models were used to estimate drug-induced QTc changes at mean maximum plasma concentration of investigated compounds. Calculations of QTc intervals involving and omitting QT/RR hysteresis correction were compared. These comparisons showed that ignoring QT/RR hysteresis has two undesirable effects: (A) In the design of subject-specific heart rate corrections (needed in studies of drugs that change heart rate) omission of QT/RR hysteresis may lead to signals of QTc prolongation of more than 10 ms to be missed. (B) Irrespective of whether the investigated drug changes heart rate, omission of QT/RR hysteresis causes the widths of the confidence intervals of the PK/PD predicted QTc interval changes to be increased by 20–30% on average (exceeding 50% in some cases). This may lead to a failure of excluding meaningful QTc prolongation which would be excluded if using hysteresis correction. The study concludes that correction for QT/RR hysteresis should be incorporated into future studies of drug-induced QTc changes. Subject-specific heart rate corrections that omit hysteresis correction may lead to erroneously biased conclusions. Even when using universal (e.g. Fridericia) heart rate correction, hysteresis correction decreases the confidence intervals of QTc changes and thus helps avoiding false positive outcomes.

Influence of Meals and Glycemic Changes on QT Interval Dynamics

Thorough QT/QTc studies have become an integral part of early drug development programs, with major clinical and regulatory implications. This analysis expands on existing pharmacodynamic models of QT interval analysis by incorporating the influence of glycemic changes on the QT interval in a semimechanistic manner. A total of 21 healthy subjects enrolled in an open-label phase 1 pilot study and provided continuous electrocardiogram monitoring and plasma glucose and insulin concentrations associated with a 24-hour baseline assessment. The data revealed a transient decrease in QTc, with peak suppression occurring approximately 3 hours after the meal. A semimechanistic modeling approach was applied to evaluate temporal delays between meals and subsequent changes that might influence QT measurements. The food effect was incorporated into a model of heart rate dynamics, and additional delayed effects of the meal on QT were incorporated using a glucose-dependent hypothetical transit compartment. The final model helps to provide a foundation for the future design and analysis of QT studies that may be confounded by meals. This study has significant implications for QT study assessment following a meal or when a cohort is receiving a medication that influences postprandial glucose concentrations.

Model-Based Evaluation of Exenatide Effects on the QT Interval in Healthy Subjects Following Continuous IV Infusion

Investigation of the cardiovascular proarrhythmic potential of a new chemical entity is now an integral part of drug development. Studies suggest that meals and glycemic changes can influence QT intervals, and a semimechanistic model has been developed that incorporates the effects of changes in glucose concentrations on heart rate (HR) and QT intervals. This analysis aimed to adapt the glucose-HR-QT model to incorporate the effects of exenatide, a drug that reduces postprandial increases in glucose concentrations. The final model includes stimulatory drug effects on glucose elimination and HR perturbations. The targeted and constant exenatide plasma concentrations (>200 pg/mL), via intravenous infusions at multiple dose levels, resulted in significant inhibition of glucose concentrations. The exenatide concentration associated with 50% of the stimulation of HR production was 584 pg/mL. After accounting for exenatide effects on glucose and HR, no additional drug effects were required to explain observed changes in the QT interval. Resulting glucose, HR, and QT profiles at all exenatide concentrations were adequately described. For therapeutic agents that alter glycemic conditions, particularly those that alter postprandial glucose, the QT interval cannot be directly compared to that with placebo without first accounting for confounding factors (eg, glucose) either through mathematical modeling or careful consideration of mealtime placement in the study design.

Thorough QT (TQT) studies: concordance with torsadogenesis and an evolving cardiac safety testing paradigm

Since 2005, when the International Conference on Harmonisation (ICH) E14 guideline was adopted, no drug has been withdrawn because of QTc prolongation or torsade de pointes arrhythmia. There are, however, costs associated with this success. In addition to the time and money invested, thorough QT (TQT) studies have limited the efficiency of the drug development pipeline. In this paper, we discuss the relevance of TQT trials as a tool for proarrhythmic risk prediction as a part of the debate regarding their usefulness.

Considerations for assessing the potential effects of antidiabetes drugs on cardiac ventricular repolarization: A report from the Cardiac Safety Research Consortium

Thorough QT studies conducted according to the International Council on Harmonisation E14 guideline are required for new nonantiarrhythmic drugs to assess the potential to prolong ventricular repolarization. Special considerations may be needed for conducting such studies with antidiabetes drugs as changes in blood glucose and other physiologic parameters affected by antidiabetes drugs may prolong the QT interval and thus confound QT/corrected QT assessments. This review discusses potential mechanisms for QT/corrected QT interval prolongation with antidiabetes drugs and offers practical considerations for assessing antidiabetes drugs in thorough QT studies. This article represents collaborative discussions among key stakeholders from academia, industry, and regulatory agencies participating in the Cardiac Safety Research Consortium. It does not represent regulatory policy.

Clinical ECG Assessment

With the adoption of the ICH E14 guidance, the thorough QT/QTc (TQT) study has become the focus of clinical assessment of an NCE's effects on ECG parameters. The TQT study is used as a guide to the liability of a drug to cause proarrhythmias on the basis of delayed cardiac repolarization. Around 300 TQT studies have been performed since 2005 and through interactions between sponsors and regulators, especially FDA's Interdisciplinary Review Team (IRT) for QT studies. These studies can today be performed more effectively and with great confidence in the generated data. This chapter will discuss technical features and the design and analysis of TQT studies, how assay sensitivity is demonstrated, and examples from recently conducted studies. ECG assessment for drugs that cannot be safely given to healthy volunteers is also addressed, and examples from studies in cancer patients and in healthy volunteers with tyrosine kinase inhibitors are discussed. The TQT study is resource intensive and designed to solely evaluate whether an NCE prolongs the QTc interval. If data with similar confidence can be generated from other studies that are routinely performed as part of the clinical development, this would represent a more optimal use of human resources. Methods and approaches to increase the confidence in ECG data derived from "early QT assessment" in single-ascending/multiple-ascending dose studies are therefore discussed, and a path toward replacing the TQT study using these approaches will be outlined.

Evaluation of Assay Sensitivity and the Concentration-Effect Relationship of Moxifloxacin in a QT/QTc Study in Japan

To investigate the potential for a QT/QTc study in Japan, a randomized, single-blind, crossover study was conducted using moxifloxacin in 64 healthy Japanese male volunteers. A 12-lead Holter electrocardiogram was used to test a relatively small population at each of 4 incorporated clinical research units to confirm the assay sensitivity and efficiency. Moxifloxacin (400 mg) significantly prolonged QT intervals, as previously reported, with small variations in this study. In addition, the placebo-adjusted mean QTcF changes from predose baseline showed that the lower bounds of the 1-sided 95% confidence interval exceeded 5 milliseconds at all of the clinical research units. The data also indicated statistically significant concentration-QT relationships in 3 of the 4 research units by separate analysis. These findings and the small amount of variability in this study suggest the feasibility of conducting a high-quality QT/QTc study in Japan.

Circadian Variation and Baseline Definition in Parallel-Group Thorough QT Studies

For thorough QT (TQT) studies employing a parallel-group design, there has been a clear regulatory preference for the use of time-matched, rather than time-averaged, baseline values to account for circadian variation when estimating the magnitude of the drug effect on the QT interval. In this paper, both historical data from parallel-group TQT studies and simulated data from assumed circadian models are utilized to comprehensively assess the performance characteristics of 3 repeated-measures analysis of covariance models. The results indicate that each analysis model performs adequately in the absence of an observed time-matched baseline imbalance between the treatment groups. However, the analysis model with time-matched baseline as a covariate performs poorly under the setting of an observed time-matched baseline imbalance between the treatment groups. The analysis model with time-averaged baseline as a covariate and the analysis model with both time-matched and time-averaged baselines as covariates provide unbiased estimates of the treatment difference and properly control the type I error rate, regardless of an observed time-matched baseline imbalance or within-patient variation in circadian parameters.

Cardiac Safety Research Consortium: can the thorough QT/QTc study be replaced by early QT assessment in routine clinical pharmacology studies? Scientific update and a research proposal for a path forward

The International Conference on Harmonization E14 guidance for the clinical evaluation of QT/QTc interval prolongation requires almost all new drugs to undergo a dedicated clinical study, primarily in healthy volunteers, the so-called TQT study. Since 2005, when the E14 guidance was implemented in United States and Europe, close to 400 TQT studies have been conducted. In February 2012, the Cardiac Safety Research Consortium held a think tank meeting at Food and Drug Administration's White Oak campus to discuss whether "QT assessment" can be performed as part of routine phase 1 studies. Based on these discussions, a group of experts convened to discuss how to improve the confidence in QT data from early clinical studies, for example, the First-Time-in-Human trial, through collection of serial electrocardiograms and pharmacokinetic samples and the use of exposure response analysis. Recommendations are given on how to design such "early electrocardiogram assessment," and the limitation of not having a pharmacologic-positive control in these studies is discussed. A research path is identified toward collecting evidence to replace or provide an alternative to the dedicated TQT study.

ICH E14-compatible holter bin method and its equivalence to individual heart rate correction in the assessment of drug-induced QT changes

INTRODUCTION

The Holter bin method evaluates QT interval changes in the presence of heart rate changes without correcting the QT interval. However, the method does not allow time-matched comparisons, thus contradicting available guidance and good practice. We report a modification of the methods that allows time-matched comparisons without any heart rate correction.

METHODS AND RESULTS

The modified Holter bin method (a) finds matching baseline heart rates for each QT reading on treatment and (b) calculates ΔQT values from the QT intervals on baseline and on treatment that match in heart rates. The difference between ΔQT values on active treatment and placebo provides the ΔΔQT value. The method was compared with the individual correction method in the data of the mirabegron thorough QT study in which supratherapeutic doses of this β3-adrenoceptor agonist led to substantial heart rate changes. The modified Holter bin method reproduced closely the results obtained with the individual heart rate correction. At all time points of the mirabegron study, the differences between the mean ΔΔQT values by the Holter bin method and the individual correction method were below 1 millisecond. Compared to the individual correction, the Holter bin method led to slight increases in the standard deviations of ΔΔQT values, but these were on average below 0.25 millisecond.

CONCLUSIONS

The Holter bin methodology can be modified to make it compatible with the available guidance and with good practice of clinical investigations. The results obtained with the modified Holter bin method are practically the same as with individualized heart rate corrected QT intervals. The close correspondence between the 2 methods demonstrates that the present possibilities of comparing QT interval duration in the presence of experiment-induced heart rate differences are not influenced by methodological artifacts.

The effects of moxifloxacin on QTc interval in healthy Korean male subjects

BACKGROUND AND OBJECTIVE

Moxifloxacin 400 mg is a widely used positive control in thorough QT (TQT) studies, but its QT-prolonging effects in Korean subjects have not been studied. The present study was conducted to collect pilot data in Korean subjects after moxifloxacin administration to evaluate the adequacy of moxifloxacin as a positive control.

METHODS

Thirty-eight, healthy, Korean, male subjects were recruited for pharmacokinetic (PK) blood sampling and electrocardiography (ECG) recordings at three different study sites. On day 1, a baseline 12-lead ECG was recorded, and on day 2, ECG recordings were conducted after placebo, or moxifloxacin 400- or 800-mg administration. Baseline-corrected, placebo-adjusted, corrected QT (ΔΔQTc) values were calculated. Blood samples were collected after moxifloxacin administration and PK parameters were assessed.

RESULTS

A total of 33 subjects completed the study. The largest time-matched ΔΔQTc occurred approximately 4 h after dosing, with ΔΔQTcI (QT interval corrected by individual QT-RR regression model) values of 11.66 ms (moxifloxacin 400 mg) and 20.96 ms (800 mg). The mean and 90 % confidence intervals of ΔΔQTcI did not include zero at any of the measurement time points. There was a positive correlation between plasma moxifloxacin concentration and ΔΔQTcI (r = 0.422). Dose-proportional PK profiles were observed.

CONCLUSION

Moxifloxacin 400 mg is an adequate positive control in Korean TQT studies. Our results indicate that moxifloxacin 400 mg can be used to evaluate the cardiac safety of a drug in Korean subjects.

Exenatide at therapeutic and supratherapeutic concentrations does not prolong the QTc interval in healthy subjects

Aims

Exenatide has been demonstrated to improve glycaemic control in patients with type 2 diabetes, with no effect on heart rate corrected QT (QT_c) at therapeutic concentrations. This randomized, placebo- and positive-controlled, crossover, thorough QT study evaluated the effects of therapeutic and supratherapeutic exenatide concentrations on QT_c.

Methods

Intravenous infusion was employed to achieve steady-state supratherapeutic concentrations in healthy subjects within a reasonable duration (i.e. days). Subjects received exenatide, placebo and moxifloxacin, with ECGs recorded pre-therapy and during treatment. Intravenous exenatide was expected to increase heart rate to a greater extent than subcutaneous twice daily or once weekly formulations. To assure proper heart rate correction, a wide range of baseline heart rates was assessed and prospectively defined methodology was applied to determine the optimal QT correction.

Results

Targeted steady-state plasma exenatide concentrations were exceeded (geometric mean ± SEM 253 ± 8.5 pg ml⁻¹, 399 ± 11.9 pg ml⁻¹ and 627 ± 21.2 pg ml⁻¹). QT_cP, a population-based method, was identified as the most appropriate heart rate correction and was prespecified for primary analysis. The upper bound of the two-sided 90% confidence interval for placebo-corrected, baseline-adjusted QT_cP (ΔΔQT_cP) was <10 ms at all time points and exenatide concentrations. The mean of three measures assessed at the highest steady-state plasma exenatide concentration of ∼500 pg ml⁻¹ (ΔΔQT_cP^avg) was −1.13 [−2.11, −0.15). No correlation was observed between ΔΔQT_cP and exenatide concentration. Assay sensitivity was confirmed with moxifloxacin.

Conclusions

These results demonstrated that exenatide, at supratherapeutic concentrations, does not prolong QT_c and provide an example of methodology for QT assessment of drugs with an inherent heart rate effect.

Update on the cardiac safety of moxifloxacin

Cardiac safety was compared in patients receiving moxifloxacin and other antimicrobials in a large patient population from Phase II-IV randomized active-controlled clinical trials. Moxifloxacin 400 mg once-daily monotherapy was administered orally (PO) or sequentially (intravenous/oral, IV/PO). Across 64 trials, 21,298 patients received PO therapy (10,613 moxifloxacin, 10,685 comparators) while 6846 received sequential IV/PO therapy (3431 moxifloxacin, 3415 comparators). Treatment-emergent cardiac adverse event (AE) rates were similar for moxifloxacin and comparators in PO (6.6% vs 5.8%) and IV/PO (11.0% vs 12.0%) trials. Treatment-emergent cardiac adverse drug reactions were rare in PO (moxifloxacin 3.2% vs comparators 2.4%) and IV/PO (moxifloxacin 1.4% vs comparators 1.5%) patients. There were five (<0.02%) treatment-emergent drug-related deaths due to cardiac events out of 28,144 patients; one PO patient died treated with comparators, one patient died treated with IV/PO moxifloxacin, and three patients died after treatment with IV/PO comparators. Only one case of treatment-related non-fatal torsade de pointes occurred in the comparator arm. Incidence rates of cardiac AEs remained low in populations at elevated risk of cardiac events predisposed to QTc prolongation (i.e. community-acquired pneumonia patients admitted to the intensive care unit and/or mechanical ventilation, patients with documented prolongation of baseline QTc interval, women, and patients ≥ 65 years old). There was no evidence of unexpected cardiac events. After moxifloxacin treatment, an expected small prolongation in QTcB and QTcF was found. This analysis of numerous clinical trials shows the favorable cardiac safety profile of moxifloxacin, when used appropriately and according to its label, versus other antibiotics.

Proarrhythmic safety of repeat doses of mirabegron in healthy subjects: a randomized, double-blind, placebo-, and active-controlled thorough QT study

Potential effects of the selective β(3)-adrenoceptor agonist mirabegron on cardiac repolarization were studied in healthy subjects. The four-arm, parallel, two-way crossover study was double-blind and placebo- and active (moxifloxacin)-controlled. After 2 baseline ECG days, subjects were randomized to one of eight treatment sequences (22 females and 22 males per sequence) of placebo crossed over with once-daily (10 days) 50, 100, or 200 mg mirabegron or a single 400-mg moxifloxacin dose on day 10. In each period, continuous ECGs were recorded at two baselines and on the last drug administration day. The lower one-sided 95% confidence interval for moxifloxacin effect on QTcI was >5 ms, demonstrating assay sensitivity. According to ICH E14 criteria, mirabegron did not cause QTcI prolongation at the 50-mg therapeutic and 100-mg supratherapeutic doses in either sex. Mirabegron prolonged QTcI interval at the 200-mg supratherapeutic dose (upper one-sided 95% CI >10 ms) in females, but not in males.

Definitions and mechanisms of drug hypersensitivity

Adverse drug reactions are a difficult problem faced by clinicians in everyday practice. The mechanisms of drug hypersensitivity are not well understood. This is reflected by difficulties in their classification, which is mainly based upon the current knowledge of immunologic and nonimmunologic mechanisms, onset of symptoms (immediate or nonimmediate) and morphology. For the individual patient, the correct diagnosis and classification is important because strict avoidance of the offending drug might be of vital importance. Considerable experience is required to guide management, to interpret results of investigations and to undertake drug challenges. This article summarizes the current knowledge regarding definitions and mechanisms. However, the field of drug hypersensitivity is rapidly expanding. Modern drugs such as biological agents bare hypersensitivity risks that are potentially mediated by, so far, unknown mechanisms.

Practice and challenges of thorough QT studies

The drug-induced Torsade de Pointes (TdP) tachycardia is a known regulatory problem which led to the concept of the so-called thorough QT (TQT) studies now required for practically every new pharmaceutical compound. This review summarizes the concept of the TQT studies, their statistical evaluation, and related pharmacodynamic /pharmacokinetic modeling. The review also lists suggestions of how to make TQT studies more efficient and how to improve the interpretation of clinical data obtained during drug development to identify drugs prone to TdP induction more effectively.

Assessment of the sensitivity of detecting drug-induced QTc changes using subject-specific rate correction

AIMS

To quantify the sensitivity of QT heart-rate correction methods for detecting drug-induced QTc changes in thorough QT studies.

METHODS

Twenty-four-hour Holter ECGs were analyzed in 66 normal subjects during placebo and moxifloxacin delivery (single oral dose). QT and RR time series were extracted. Three QTc computation methods were used: (1) Fridericia's formula, (2) Fridericia's formula with hysteresis reduction, and (3) a subject-specific approach with transfer function-based hysteresis reduction and three-parameter non-linear fitting of the QT-RR relation. QTc distributions after placebo and moxifloxacin delivery were compared in sliding time windows using receiver operating characteristic (ROC) curves. The area under the ROC curve (AUC) served as a measure to quantify the ability of each method to detect moxifloxacin-induced QTc prolongation.

RESULTS

Moxifloxacin prolonged the QTc by 10.6 ± 6.6 ms at peak effect. The AUC was significantly larger after hysteresis reduction (0.87 ± 0.13 vs. 0.82 ± 0.12, p<0.01) at peak effect, indicating a better discriminating capability. Subject-specific correction further increased the AUC to 0.91 ± 0.11 (p<0.01 vs. Fridericia with hysteresis reduction). The performance of the subject-specific approach was the consequence of a substantially lower intra-subject QTc standard deviation (5.7 ± 1.1 ms vs. 8.8 ± 1.2 ms for Fridericia).

CONCLUSION

The ROC curve provides a tool for quantitative comparison of QT heart rate correction methods in the context of detecting drug-induced QTc prolongation. Results support a broader use of subject-specific QT correction.

Conventional QT variability measurement vs. template matching techniques: comparison of performance using simulated and real ECG

Increased beat-to-beat variability in the QT interval (QTV) of ECG has been associated with increased risk for sudden cardiac death, but its measurement is technically challenging and currently not standardized. The aim of this study was to investigate the performance of commonly used beat-to-beat QT interval measurement algorithms. Three different methods (conventional, template stretching and template time shifting) were subjected to simulated data featuring typical ECG recording issues (broadband noise, baseline wander, amplitude modulation) and real short-term ECG of patients before and after infusion of sotalol, a QT interval prolonging drug. Among the three algorithms, the conventional algorithm was most susceptible to noise whereas the template time shifting algorithm showed superior overall performance on simulated and real ECG. None of the algorithms was able to detect increased beat-to-beat QT interval variability after sotalol infusion despite marked prolongation of the average QT interval. The QTV estimates of all three algorithms were inversely correlated with the amplitude of the T wave. In conclusion, template matching algorithms, in particular the time shifting algorithm, are recommended for beat-to-beat variability measurement of QT interval in body surface ECG. Recording noise, T wave amplitude and the beat-rejection strategy are important factors of QTV measurement and require further investigation.

Methodologies to characterize the QT/corrected QT interval in the presence of drug-induced heart rate changes or other autonomic effects

This White Paper, written collaboratively by members of the Cardiac Safety Research Consortium from academia, industry, and regulatory agencies, discusses different methods to characterize the QT effects for drugs that have a substantial direct or indirect effect on heart rate. Descriptions and applications are provided for individualized QT-R-R correction, Holter bin, dynamic QT beat-to-beat, pharmacokinetic-pharmacodynamic modeling, and QT assessment at constant heart rate. Most of these techniques are optimally performed using continuous electrocardiogram data obtained in clinical studies designed to characterize a drug's effect on the QT interval. An important study design element is the collection of drug-free data over a range of heart rates seen on treatment. The range of heart rates is increased at baseline by using ambulatory electrocardiogram recordings in addition to those collected under semisupine, resting conditions. Discussions in this study summarize areas of emerging consensus and other areas in which consensus remains elusive and provide suggestions for additional research to further increase our knowledge and understanding of this topic.

Effect of nalmefene 20 and 80 mg on the corrected QT interval and T-wave morphology: a randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study

BACKGROUND

Nalmefene is an orally administered competitive opioid receptor antagonist targeted at reducing alcohol consumption in alcohol-dependent patients. As part of the regulatory requirements for drug approval, the potential of novel compounds for causing unwanted proarrhythmia should be studied in a thoroughly designed clinical QT/corrected QT (QTc) study (International Conference on Harmonisation [ICH] E14 guideline).

OBJECTIVE

This study was designed to evaluate whether nalmefene 20 and 80 mg/day induced changes in cardiac repolarization biomarkers indicative of proarrhythmia (the QTc interval and T-wave morphology).

METHODS

This was a prospective, randomized, double-blind, parallel-group, placebo- and moxifloxacin-controlled, single-centre study carried out in a clinical pharmacology unit. The study included 270 healthy male and female subjects (age 18-45 years). The subjects were randomized to a 7-day treatment period of placebo, nalmefene 20 mg/day or nalmefene 80 mg/day, or placebo for 6 days followed by a single dose of moxifloxacin 400 mg on day 7. Serial triplicate ECGs were obtained over a 24-hour period at protocol-defined time-points. The primary protocol-defined endpoint was the largest time-matched baseline- and placebo-adjusted mean difference in the individually heart rate-corrected QT interval (QTcNi) recorded at any of the 12 ECG time-points distributed over a 24-hour period on day 7 of treatment. Secondary endpoints included a similar analysis using the Fridericia- (QTcF) and Bazett-corrected (QTcB) intervals. An explorative analysis included quantitative assessment of T-wave morphology using the T-wave morphology composite score (MCS) to assess for differences between treatment groups and placebo on day 7 of treatment. The frequency of outliers in the QTc intervals, the pharmacokinetics of nalmefene and the tolerability of nalmefene were also assessed.

RESULTS

Nalmefene was rapidly absorbed with a time to reach maximum plasma concentration of 2.2 hours and a dose-proportionate relationship between dose administered and exposure. The largest baseline- and placebo-adjusted mean changes from baseline in the individualized QTcNi (primary endpoint) were 5.45 ms (90% CI 1.52, 9.37) and 5.57 ms (90% CI 1.62, 9.52) for nalmefene 20 and 80 mg/day, respectively, with study sensitivity confirmed by the expected largest increase in mean QTcNi of 10.15 ms (90% CI 5.67, 14.63) for moxifloxacin. Quantitative assessment using the T-wave MCS demonstrated the largest baseline- and placebo-adjusted increase in MCS to be non-significantly different from the intra-subject variability of triplicate recordings in the placebo group. No deaths or serious adverse events occurred in the study.

CONCLUSION

This thorough QT/QTc study was a negative study in accordance with the ICH E14 guideline, meaning that nalmefene has no clinically relevant effect on the QTc interval and T-wave morphology. The study predicts no concern over proarrhythmia or need for intensive QTc monitoring with the use of nalmefene in clinical practice.

Evaluation of the effect of dapagliflozin on cardiac repolarization: a thorough QT/QTc study

INTRODUCTION

Dapagliflozin is a first-in-class sodium-glucose transporter 2 (SGLT2) inhibitor under investigation for the treatment of type 2 diabetes mellitus. A thorough QTc study was conducted, according to International Conference on Harmonization E14 guidelines, to characterize the effect of dapagliflozin on cardiac repolarization.

METHODS

The present study was a double-blind, four-period, placebo-controlled crossover study at a single-center inpatient clinical pharmacology unit. The study enrolled 50 healthy men who were randomized to receive sequences of single doses of dapagliflozin 150 mg, dapagliflozin 20 mg, moxifloxacin 400 mg, and placebo. The sequences were randomized based on the Williams design for a cross-over study to reduce the "carryover" effects from drug-to-drug even with sufficient washout periods. Digital 12-lead electrocardiograms were recorded at nine time points over 24 hours in each period. QT intervals were corrected for heart rate using a study-specific correction factor (QTcX) and Fridericia's formula.

RESULTS

For dapagliflozin, the upper bound of the one-sided 95% confidence interval (CI) for time-matched, placebo-subtracted, baseline adjusted QTc intervals (ΔΔQTc) was <10 ms. ΔΔQTc was independent of dapagliflozin concentrations. No QTc thresholds >450 ms or QTc increases >30 ms were observed. Moxifloxacin increased the mean QTcX interval by 7.7 ms (lower bound 90% CI, 6.2 ms) over 1-4 hours after dosing, confirming assay sensitivity.

CONCLUSION

Dapagliflozin, at supratherapeutic doses, does not have a clinically significant effect on the QT interval in healthy subjects.

Assessing QT interval prolongation and its associated risks with antipsychotics

Several antipsychotics are associated with the ventricular tachycardia torsade de pointes (TdP), which may lead to sudden cardiac death (SCD), because of their inhibition of the cardiac delayed potassium rectifier channel. This inhibition extends the repolarization process of the ventricles of the heart, illustrated as a prolongation of the QT interval on a surface ECG. SCD in individuals receiving antipsychotics has an incidence of approximately 15 cases per 10,000 years of drug exposure but the exact association with TdP remains unknown because the diagnosis of TdP is uncertain. Most patients manifesting antipsychotic-associated TdP and subsequently SCD have well established risk factors for SCD, i.e. older age, female gender, hypokalaemia and cardiovascular disease. QT interval prolongation is the most widely used surrogate marker for assessing the risk of TdP but it is considered somewhat imprecise, partly because QT interval changes are subject to measurement error. In particular, drug-induced T-wave changes (e.g. flattening of the T-wave) may complicate the measurement of the QT interval. Furthermore, the QT interval depends on the heart rate and a corrected QT (QTc) interval is often used to compensate for this. Several correction formulas have been suggested, with Bazett's formula the most widely used. However, Bazett's formula overcorrects at a heart rate above 80 beats per minute and, therefore, Fridericia's formula is considered more appropriate to use in these cases. Several other surrogate markers for TdP have been developed but none of them is clinically implemented yet and QT interval prolongation is still considered the most valid surrogate marker. Although automated QT interval determination may offer some assistance, QT interval determination is best performed by a cardiologist skilled in its measurement. A QT interval >500 ms markedly increases the risk for TdP and SCD, and should lead to discontinuation of the offending drug and, if present, correction of underlying electrolyte disturbances, particularly serum potassium and magnesium derangements. Before prescribing antipsychotics that may increase the QTc interval, the clinician should ask about family and personal history of SCD, presyncope, syncope and cardiac arrhythmias, and recommend cardiology consultation if history is positive.

Systematic decrements in QTc between the first and second day of contiguous daily ECG recordings under controlled conditions

BACKGROUND

Many thorough QT (TQT) studies use a baseline day and double delta analysis to account for potential diurnal variation in QTc. However, little is known about systematic changes in the QTc across contiguous days when normal volunteers are brought into a controlled inpatient environment.

METHODS

Two separate crossover TQT studies included 2 days of no treatment lead-in days with ECG collection preceding periods of drug treatment . In the first study, there were two pairs of such contiguous days with 10 replicate electrocardiograms (ECGs) collected at six time points, and in the second study, there were four pairs of contiguous days with nine replicate ECGs collected at five time points. These lead-in day pairs provided the opportunity to evaluate any systematic changes across contiguous first and second days of an inpatient environment. Within-patient consistency of change across pairs of days as well as within day, diurnal variation could also be evaluated.

RESULTS

Modest (4.2 ms [range 1.9-6.5 ms]) but consistent decreases (significant [P < 0.05] for all 32 comparisons) were observed (probability: ≤5.4 × 10(-16)). Although group behavior with respect to QTc was consistent, individual subjects demonstrated substantial variability across pairs of days. Evidence of diurnal variation was weak and inconsistent. Magnitude of any diurnal variation was less than magnitude of change across days.

CONCLUSIONS

Subjects show a systematic decrease in QTc from first day to second day of inpatient status and do not demonstrate a significant diurnal pattern. The magnitude of this systematic change is sufficient to influence QTc study interpretation.

Covariate analysis of QTc and T-wave morphology: new possibilities in the evaluation of drugs that affect cardiac repolarization

This study adds the dimension of a T-wave morphology composite score (MCS) to the QTc interval-based evaluation of drugs that affect cardiac repolarization. Electrocardiographic recordings from 62 subjects on placebo and 400 mg moxifloxacin were compared with those from 21 subjects on 160 and 320 mg D,L-sotalol. T-wave morphology changes, as assessed by DeltaMCS, are larger after 320 mg D,L-sotalol than after 160 mg D,L-sotalol; and the changes associated with 160 mg D,L-sotalol are, in turn, larger than those associated with moxifloxacin and placebo. Covariate analyses of DeltaQTc and DeltaMCS showed that changes in T-wave morphology are a significant effect of D,L-sotalol. By contrast, moxifloxacin was found to have no significant effect on T-wave morphology (DeltaMCS) at any given change in QTc. This study offers new insights into the repolarization behavior of a drug associated with low cardiac risk vs. one associated with a high risk and describes the added benefits of a T-wave MCS as a covariate to the assessment of the QTc interval.