Effect of levetiracetam on cardiac repolarization in healthy subjects: a single-dose, randomized, placebo- and active-controlled, four-way crossover study

Sudden Cardiac Death or Ventricular Arrythmia in Patients Taking Levetiracetam or Oxcarbazepine

BACKGROUND AND OBJECTIVES

Levetiracetam is a widely used antiseizure medication. Recent concerns have been raised regarding the potential prolongation of the QT interval by levetiracetam and increased risk of sudden cardiac death. This could have profound implications for patient safety and for prescribing practice. This study assessed the potential association of levetiracetam with cardiac outcomes related to QT interval prolongation. We compared outcomes of patients taking levetiracetam with those taking oxcarbazepine as a comparator medication that has not been associated with prolongation of the QT interval.

METHODS

The sample included patients who were newly prescribed levetiracetam or oxcarbazepine from January 31, 2010, to December 31, 2019, using administrative claims data from the OptumLabs Data Warehouse (OLDW). The analysis focused on a combined endpoint of sudden cardiac death or ventricular arrythmia, which are both linked to QT interval prolongation. We used a new user design and selected oxcarbazepine as an active comparator with levetiracetam to minimize bias. We used propensity score weighting to balance the levetiracetam and oxcarbazepine cohorts and then performed weighted Cox regressions to evaluate the association of levetiracetam with the combined endpoint.

RESULTS

We identified 104,655 enrollees taking levetiracetam and 39,596 enrollees taking oxcarbazepine. At baseline, enrollees taking levetiracetam were older, more likely to have diagnosed epilepsy, and more likely to have diagnosed comorbidities including hypertension, cerebrovascular disease, and coronary artery disease. In the main analysis, we found no significant difference between levetiracetam and oxcarbazepine in the rate of the combined endpoint for the Cox proportional hazards model (hazard ratio [HR] 0.79, 95% CI 0.42-1.47) or Cox regression with time-varying characteristics (HR 0.78, 95% CI 0.41-1.50).

DISCUSSION

When compared with oxcarbazepine, levetiracetam does not correlate with increased risk of ventricular arrythmia and sudden cardiac death. Our finding does not support the concern for cardiac risk to indicate restriction of levetiracetam use nor the requirement of cardiac monitoring when using it.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that sudden cardiac death and ventricular arrythmia are not more frequent in patients older than 17 years newly prescribed levetiracetam, compared with those prescribed oxcarbazepine.

Effect of levetiracetam therapy on electrocardiographic parameters

AIM

The purpose of this study was to compare the electrocardiographic parameters before and at the sixth month of treatment of patients diagnosed with epilepsy and who were started on levetiracetam therapy.

METHODS

The files of 30 patients diagnosed with epilepsy and on levetiracetam therapy were examined in this study. Clinical findings, electroencephalography (EEG), cranial magnetic resonance imaging (MRI) and electrocardiography (ECG) data before and at the sixth month of treatment were recorded.

RESULTS

The patients' mean age was 10.93 ± 3.74 (4-17) years; 16 (53.33%) patients were boys. In total, 13 (43.3%) were found to experience focal seizures, and 17 (56.7%) generalized epilepsy-type seizures. Comparison of the ECG parameters (PR interval, QTc, QT interval, and QRS duration) revealed a shortening in the PR interval and QTc values at the sixth month of treatment, although the changes were not statistically significant. No significant differences in terms of gender and epilepsy types were observed between the ECG parameters before treatment and at the sixth month (p > 0.05).

CONCLUSION

In this study, levetiracetam was found to have no effect on ECG parameters.

Testing the nonclinical Comprehensive In Vitro Proarrhythmia Assay (CiPA) paradigm with an established anti-seizure medication: Levetiracetam case study

Levetiracetam (LEV), a well-established anti-seizure medication (ASM), was launched before the original ICH S7B nonclinical guidance assessing QT prolongation potential and the introduction of the Comprehensive In Vitro Proarrhythmia Assay (CiPA) paradigm. No information was available on its effects on cardiac channels. The goal of this work was to "pressure test" the CiPA approach with LEV and check the concordance of nonclinical core and follow-up S7B assays with clinical and post-marketing data. The following experiments were conducted with LEV (0.25-7.5 mM): patch clamp assays on hERG (acute or trafficking effects), NaV 1.5, CaV 1.2, Kir 2.1, KV 7.1/mink, KV 1.5, KV 4.3, and HCN4; in silico electrophysiology modeling (Virtual Assay® software) in control, large-variability, and high-risk human ventricular cell populations; electrophysiology measurements in human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and dog Purkinje fibers; ECG measurements in conscious telemetered dogs after single oral administration (150, 300, and 600 mg/kg). Except a slight inhibition (<10%) of hERG and KV 7.1/mink at 7.5 mM, that is, 30-fold the free therapeutic plasma concentration (FTPC) at 1500 mg, LEV did not affect any other cardiac channels or hERG trafficking. In both virtual and real human cardiomyocytes, and in dog Purkinje fibers, LEV induced no relevant changes in electrophysiological parameters or arrhythmia. No QTc prolongation was noted up to 2.7 mM unbound plasma levels in conscious dogs, corresponding to 10-fold the FTPC. Nonclinical assessment integrating CiPA assays shows the absence of QT prolongation and proarrhythmic risk of LEV up to at least 10-fold the FTPC and the good concordance with clinical and postmarketing data, although this does not exclude very rare occurrence of QT prolongation cases in patients with underlying risk factors.

Effects of levetiracetam treatment on autonomic nervous system functions in pediatric epilepsy patients

BACKGROUND

This study investigated the effects of levetiracetam (LEV) treatment on cardiac rhythm and heart rate variability.

METHODS

The study included two groups of patients diagnosed with non-lesional epilepsy who had not yet been treated and who presented to the outpatient pediatric neurology clinic at Van Training and Research Hospital, Van, Turkey, between 2019 and 2020. The heart rate variability (HRV) of 47 patients in the first group, before and at the 3rd month of treatment, and intravenous (IV) LEV loading in 13 patients in the second group was evaluated by Holter electrocardiography (ECG).

RESULTS

It was determined that the values of triangular index, standard deviation of the RR intervals over a 24-hour period (SDNN), standard deviation of all 5-minute mean RR intervals (SDANN), mean of standard deviations of all normal RR intervals (SDNNI), the percentage of RR intervals with >50-millisecond variation (PNN50), and the square root of mean squared differences of successive RR intervals (RMSSD). HRV of 47 patients under LEV treatment significantly increased in the 3rd month of treatment compared to baseline (p < 0.05). No difference was found in HRV between the intravenous loading and the control group (p > 0.05).

CONCLUSIONS

Our study suggests that the sympathovagal balance before treatment in the patient group is in favor of the sympathetic nervous system and that the sympathovagal imbalance improves after treatment. Our results show that LEV monotherapy and loading have no negative effect on HRV and potential cardiac arrhythmia risk in children with epilepsy.

Cardiac adverse effects of antiseizure medications

INTRODUCTION

Patients with severe epilepsy are at increased risk of cardiovascular disease and arrhythmias. Although antiseizure medications (ASMs) may have indirect protective effects against cardiovascular events by reducing seizure frequency and hence sudden death in epilepsy, some of them exert cardiotoxic effects.

AREAS COVERED

Patients with epilepsy, mainly those with severe forms, are at higher risk of cardiac disease because their heart can have structural alterations and electrical instability as a consequence of repeated seizures. Some ASMs have direct protective effects through anti-inflammatory, antioxidant, hypotensive, and lipid-reducing properties. Antiseizure medications can also have toxic cardiac effects including both long-term consequences, such as the increased risk of atherogenesis and subsequent cardiovascular disease due to the influence on lipid profile and pro-inflammatory milieu, and immediate effects as the increased risk of potentially fatal arrhythmias due to the influence on ion channels. Sodium channel blocking ASMs may also affect cardiac sodium channels and this effect is particularly observed in subjects with genetic mutations in cardiac ion channels. Fenfluramine cause valvulopathies in obese subjects and this effect need to be evaluated in epilepsy patients.

EXPERT OPINION

For the selection of treatment, cardiotoxic effects of ASMs should be considered; cardiac monitoring of treatment is advisable.

Research implications of the FDA ECG warehouse and related resources

The electrocardiogram is often used as an efficacy endpoint for comparing new drugs or as an indicator for cardiovascular safety in both studies of arrhythmic and non-arrhythmic novel drugs. The FDA ECG Warehouse data are owned by the submitting entities, generally pharmaceutical company manufacturers. However, a subset of these ECG data was released with permission from the data owners to the CSRC for access by investigators, equipment manufacturers and algorithm developers for CSRC-approved research and development studies. This article provides an overview of the Cardiac Safety Research Consortium (CSRC) ECG Warehouse, including data availability, completed and ongoing projects, as well as future growth potential amidst an ever expanding FDA ECG Warehouse. Given that current ICH E14 guidelines request that sponsors submitting new drug applications assess the effects on the QT interval using a thorough QT (TQT) or dose-ranging study with concentration-QT analysis during early clinical development to assess cardiac risk, developing novel methods to determine cardiovascular safety, as well as understanding current ECG collection and analysis methods are prudent. The ability to utilize previously collected ECG data for secondary analyses improves cardiovascular safety by multiplying the scientific contribution of the original research.

Comorbidity between epilepsy and cardiac arrhythmias: Implication for treatment

Epilepsy is often comorbid with either neurological or nonneurological diseases. The association between epilepsy and cardiac arrhythmias is not infrequent, mostly in patients with severe forms of epilepsy or critically ill. Remarkably, these medical conditions share many similarities. Vascular and genetic disorders may predispose to both seizures and abnormalities of cardiac electrophysiology. Repeated and uncontrolled seizures may favor potentially life-threatening arrhythmias. Antiepileptic drugs (AEDs) may facilitate the occurrence of cardiac arrhythmias by acting on ionic channels at heart level. Antiarrhythmic drugs (AADs) can have effects on ionic channels expressed in the brain, as suggested by their efficacy in treating patients with rare forms of epilepsy; AADs may also be proconvulsant, mainly during their overdosage. In clinical practice, the AEDs with the lowest risk to influence cardiac electrophysiology are to be preferred in patients presenting with either seizures or arrhythmias. Traditional AEDs should be avoided because of their arrhythmogenic properties and enzyme-inducing effects, which may make ineffective the concomitant treatment with AADs. Some of the newer AEDs can rarely affect cardiac rhythm, and electrocardiogram (ECG) monitoring should be warranted.

Severe hypoglycemia-induced sudden death is mediated by both cardiac arrhythmias and seizures

We previously demonstrated that insulin-induced severe hypoglycemia-associated sudden death is largely mediated by fatal cardiac arrhythmias. In the current study, a pharmacological approach was taken to explore the potential contribution of hypoglycemic seizures and the sympathoadrenergic system in mediating severe hypoglycemia-associated sudden death. Adult Sprague-Dawley rats were randomized into one of four treatment groups: 1) saline (SAL), 2) anti-arrhythmic (β₁ blocker atenolol), 3) antiseizure (levetiracetam), and 4) combination antiarrhythmic and antiseizure (β₁ Blocker+Levetiracetam). All rats underwent hyperinsulinemic severe hypoglycemic clamps for 3.5 h. When administered individually during severe hypoglycemia, β₁ blocker reduced 2nd and 3rd degree heart block by 7.7- and 1.6-fold, respectively, and levetiracetam reduced seizures 2.7-fold, but mortality in these groups did not decrease. However, it was combined treatment with both β₁ blocker and levetiracetam that remarkably reduced seizures and completely prevented respiratory arrest, while also eliminating 2nd and 3rd degree heart block, leading to 100% survival. These novel findings demonstrate that, in mediating sudden death, hypoglycemia elicits two distinct pathways (seizure-associated respiratory arrest and arrhythmia-associated cardiac arrest), and therefore, prevention of both seizures and cardiac arrhythmias is necessary to prevent severe hypoglycemia-induced mortality.

Humans Vary, So Cardiac Models Should Account for That Too!

The utilization of mathematical modeling and simulation in drug development encompasses multiple mathematical techniques and the location of a drug candidate in the development pipeline. Historically speaking they have been used to analyze experimental data (i.e., Hill equation) and clarify the involved physical and chemical processes (i.e., Fick laws and drug molecule diffusion). In recent years the advanced utilization of mathematical modeling has been an important part of the regulatory review process. Physiologically based pharmacokinetic (PBPK) models identify the need to conduct specific clinical studies, suggest specific study designs and propose appropriate labeling language. Their application allows the evaluation of the influence of intrinsic (e.g., age, gender, genetics, disease) and extrinsic [e.g., dosing schedule, drug-drug interactions (DDIs)] factors, alone or in combinations, on drug exposure and therefore provides accurate population assessment. A similar pathway has been taken for the assessment of drug safety with cardiac safety being one the most advanced examples. Mechanistic mathematical model-informed safety evaluation, with a focus on drug potential for causing arrhythmias, is now discussed as an element of the Comprehensive in vitro Proarrhythmia Assay. One of the pillars of this paradigm is the use of an in silico model of the adult human ventricular cardiomyocyte to integrate in vitro measured data. Existing examples (in vitro—in vivo extrapolation with the use of PBPK models) suggest that deterministic, epidemiological and clinical data based variability models can be merged with the mechanistic models describing human physiology. There are other methods available, based on the stochastic approach and on population of models generated by randomly assigning specific parameter values (ionic current conductance and kinetic) and further pruning. Both approaches are briefly characterized in this manuscript, in parallel with the drug-specific variability.

Effects of phenobarbital and levetiracetam on PR and QTc intervals in patients with post-stroke seizure

BACKGROUND AND OBJECTIVES

Sudden unexplained/unexpected death (SUDEP) is related to high mortality in patients with epilepsy. The prolongation of QT interval, involved in cardiac arrhythmia-related SUDEP, may be precipitated by antiepileptic drugs (AEDs). In this study, we evaluated the effects of phenobarbital and levetiracetam on PR-QTc intervals in patients with post-stroke seizures.

METHODS

We performed an open-label, parallel group, prospective, multicenter study between June 2009 and December 2013 in patients older than 18 years of age with a clinical diagnosis of post-stroke seizure and treated with phenobarbital or levetiracetam. In order to exclude a role of cerebral post-stroke injury on modulation of PR and QTc intervals, patients with cerebral post-stroke injury and without seizures were also enrolled as controls.

RESULTS

Interictal electrocardiography analysis revealed no significant difference in PR interval between patients treated with an AED (n = 49) and control patients (n = 50) (181.25 ± 12.05 vs. 182.4 ± 10.3 ms; p > 0.05). In contrast, a significantly longer QTc interval was recorded in patients treated with an AED compared with control patients (441.2 ± 56.6 vs. 396.8 ± 49.3 ms; p < 0.01). Patients treated with phenobarbital showed a significantly longer QTc interval than patients treated with levetiracetam (460.0 ± 57.2 vs. 421.5 ± 50.1 ms; p < 0.05).

CONCLUSIONS

The study reported that in patients with late post-stroke seizures, phenobarbital prolonged QTc interval more so than levetiracetam.

Electrocardiographic safety of cangrelor, a new intravenous antiplatelet agent: a randomized, double-blind, placebo- and moxifloxacin-controlled thorough QT study

Cangrelor is an intravenous P2Y12 inhibitor under investigation as an antiplatelet drug in the setting of acute coronary syndromes. To determine the electrophysiologic safety of parenteral cangrelor, cardiac repolarization effects were measured in 67 healthy volunteers (aged 18-45 years) in a randomized crossover design, including 4 treatment sequences of therapeutic cangrelor, supratherapeutic cangrelor, placebo, and moxifloxacin (positive control). Triplicate electrocardiogram measurements and pharmacokinetic samples were collected at baseline and 9 time points postdose on day 1. For both cangrelor and moxifloxacin, time-matched, placebo-adjusted change in QT from baseline was evaluated using an individual (QTcI) heart rate correction. After cangrelor dosing, change in QTcI was <5 ms at all times points and all corresponding upper 2-sided 90% confidence intervals (CIs) were <10 ms. Although moxifloxacin failed to show a lower CI >5 ms, expected time trends and lower CI >4.0 ms demonstrate assay sensitivity. QTcI was not affected by plasma concentrations of cangrelor metabolites, and cangrelor had no other adverse effects on electrocardiographic parameters. Clinically, cangrelor exposure was well tolerated. Thus, this thorough QT study demonstrated that therapeutic and supratherapeutic cangrelor doses do not adversely affect cardiac repolarization in normal volunteers (clinicaltrials.gov; identifier NCT00699504).

Comparison of two methods of estimating reader variability in QT interval measurements in thorough QT/QTc studies

BACKGROUND

Two methods of estimating reader variability (RV) in QT measurements between 12 readers were compared.

METHODS

Using data from 500 electrocardiograms (ECGs) analyzed twice by 12 readers, we bootstrapped 1000 datasets each for both methods. In grouped analysis design (GAD), the same 40 ECGs were read twice by all readers. In pairwise analysis design (PAD), 40 ECGs analyzed by each reader in a clinical trial were reanalyzed by the same reader (intra-RV) and also by another reader (inter-RV); thus, variability between each pair of readers was estimated using different ECGs.

RESULTS

Inter-RV (mean [95% CI]) between pairs of readers by GAD and PAD was 3.9 ms (2.1-5.5 ms) and 4.1 ms (2.6-5.4 ms), respectively, using ANOVA, 0 ms (-0.0 to 0.4 ms), and 0 ms (-0.7 to 0.6 ms), respectively, by actual difference between readers and 7.7 ms (6.2-9.8 ms) and 7.7 ms (6.6-9.1 ms), respectively, by absolute difference between readers. Intra-RV too was comparable.

CONCLUSIONS

RV estimates by the grouped- and pairwise analysis designs are comparable.

Design and analysis considerations for thorough QT studies employing conventional (10 s, 12-lead) ECG recordings

The QT interval from the ECG cannot be measured precisely. The relationship of the QT interval to the RR interval within individuals across time and different RR values, and across individuals eludes complete understanding. Intrinsic beat-to-beat variability in QT interval corrected for heart rate (QTc interval) is not trivial. Therefore, it is difficult to determine a valid and reliable estimate of the time for ventricular repolarization based on the QTc interval. Yet, it must be demonstrated that a drug does not result in an increase in the QTc interval that exceeds 5 ms with some reasonable degree of certainty to be quite confident that the drug does not convey some risk of ventricular tachydysrhythmia due to delayed ventricular repolarization. This demonstration can be a Herculean task due to the magnitude of variability in the QTc interval. Design features and analytical methods that might be used in the thorough QT study to improve the chances of demonstrating the true relationship between a drug and QTc interval are reviewed.

Interictal 12-lead electrocardiography in patients with epilepsy

Interictal electrocardiographic predictors of sudden unexpected death in epilepsy (SUDEP) are unknown. This study was designed to identify the unique features of the interictal 12-lead electrocardiogram (EKG) in patients with epileptic seizures. We conducted a retrospective chart review of adult patients below the age of 65 admitted to our epilepsy monitoring unit. Using EEG telemetry data, we classified patients as having nonepileptic seizures (NESs), probable epilepsy (PE), or definite epilepsy (DE) and analyzed 12-lead EKGs obtained on admission. Patients with NESs were assigned as the control group. We included patients taking antipsychotic and/or antidepressant medications but excluded patients with medical conditions or taking other medications that would otherwise confound EKG measurements. Out of the 1007 charts reviewed, 195 patients were included in our analysis, and extensive subgroup analyses were performed. We found that patients with definite localization-related epilepsy displayed a significantly longer average PR interval (162.1 ms) than patients with NESs (148.8 ms). This effect was pronounced in female patients and did not vary with the number of antiepileptic drugs (AEDs) prescribed. In contrast to previous studies, mean QTc intervals were not significantly different between DE (428 ms) and NESs (422.6 ms). However, within females, this difference reached statistical significance (DE: 434.6 ms, NESs: 424.6 ms). Antiepileptic drug polytherapy was associated with a significantly lower QTc interval (416 ms in patients on 4-6 drugs and 436.4 ms in patients on 0-1 drugs). Levetiracetam was the most commonly used AED and was associated with the longest average PR (163 ms) and QTc (432 ms) intervals. The mean QRS axis displayed a significant leftward shift in patients with localization-related epilepsy (35.6° versus 54.3° in patients with NESs) and also in female patients with DE (42.1° versus 55.4° in female patients with NESs). No differences were observed between patients with left versus right hemisphere seizure foci. Overall, these findings may reflect cardiac structural changes and/or alterations in autonomic tone that deserve closer study. Further, longer-term prospective studies are required to understand how these electrocardiographic signatures may predict sudden unexpected death in epilepsy.

Insulin at normal physiological levels does not prolong QT(c) interval in thorough QT studies performed in healthy volunteers

AIMS

Food is known to shorten the QT(c) (QT(c)I and QT(c)F) interval and has been proposed as a non-pharmacological method of confirming assay sensitivity in thorough QT (TQT) studies and early phase studies in medicines research. Intake of food leads to a rise in insulin levels together with the release of C-peptide in equimolar amounts. However, it has been reported that euglycaemic hyperinsulinemia can prolong the QT(c) interval, whilst C-peptide has been reported to shorten the QT(c) interval. Currently there is limited information on the effects of insulin and C-peptide on the electrocardiogram (ECG). This study was performed to assess the effect of insulin, glucose and C-peptide on the QT(c) interval under the rigorous conditions of a TQT study.

METHODS

Thirty-two healthy male and female, Caucasian and Japanese subjects were randomized to receive six treatments: (1) placebo, (2) insulin euglycaemic clamp, (3) carbohydrate rich 'continental' breakfast, (4) calorie reduced 'American' FDA breakfast, (5) moxifloxacin without food, and (6) moxifloxacin with food. Measurements of ECG intervals were performed automatically with subsequent adjudication in accordance with the ICH E14 guideline and relevant amendments.

RESULTS

No effect was observed on QT(c)F during the insulin euglycaemic clamp period (maximal shortening of QT(c) F by 2.6 ms, not significant). Following ingestion of a carbohydrate rich 'continental' breakfast or a calorie reduced 'American' FDA standard breakfast, a rapid increase in insulin and C-peptide concentrations were observed. Insulin concentrations showed a peak response after the 'continental' breakfast observed at the first measurement time point (0.25 h) followed by a rapid decline. Insulin concentrations observed with the 'American' breakfast were approximately half of those seen with the 'continental' breakfast and showed a similar pattern. C-peptide concentrations showed a peak response at the first measurement time point (0.25 h) with a steady return to baseline at the 6 h time point. The response to the 'continental' breakfast was approximately double that of the 'American' FDA breakfast. A rapid onset of the effect on QT(c) F was observed with the 'continental' breakfast with shortening by >5 ms in the time interval from 1 to 4 h. After the 'American' FDA breakfast, a similar but smaller effect was seen.

CONCLUSIONS

The findings of this study demonstrate that there was no change in QT(c) during the euglycaemic clamp. Given that insulin was raised to physiological concentrations comparable with those seen after a meal, whilst the release of C-peptide was suppressed, insulin appears to have no effect on the QT(c) interval in either direction. The results suggest a relationship exists between the shortening of QT(c) and C-peptide concentrations and indicate that glucose may have a QT(c) prolonging effect, which will require further research.

QTc prolongation by antiepileptic drugs and the risk of torsade de pointes in patients with epilepsy

Sudden unexpected death in epilepsy (SUDEP) is the most common epilepsy-related cause of death. While the precise pathophysiological mechanisms underlying SUDEP are still uncertain, impaired cardiac function including seizure-induced arrhythmias has received increased attention. In addition, the potential role of antiepileptic drugs has been suggested. While the preponderance of clinical data would suggest that use of most antiepileptic drugs does not pose excessive additional risk of QT prolongation, available data also do not provide sufficient evidence that these drugs are entirely free of risk in all patients. In particular, the potential for these medications, either alone or in combination, to prolong the QT interval should be considered. This review will discuss mechanisms for drug-induced QT prolongation and its relationship to potentially fatal arrhythmias such as torsades de pointes.

Wild type and K897T polymorphisms of the hERG gene: modeling the APD in Caucasians

The presented study aims to assess the possibility of simulating changes in cardiac cell electrophysiology due to K897T polymorphism in the Caucasian population. In the first part of the experiment, the parameters of the equations describing channel gating were fitted to the experimental data. Then, the action potentials of midmyocardial cells of 100 individuals were simulated in the in vitro - in vivo extrapolation system - ToxComp. Mean APD90 for the entire simulated population is 352.05 ms (SD = 21.69 ms). Mean APD90 for the 80 individuals with the WT version of the hERG gene and for the 20 K897T homo- and heterozygotes is respectively 349.08 ms (SD = 21.09 ms) and 363.95ms (SD = 20.41 ms). The ToxComp system can be useful in predicting the impact of genetic variability on drug triggered cardiac cell electrophysiology interference.

Choice of an alternative lead for QT interval measurement in serial ECGs when Lead II is not suitable for analysis

INTRODUCTION

Conventionally, QT interval is measured in lead II. There are no data to select an alternative lead for QT measurement when it cannot be measured in Lead II for any reason.

METHODS AND RESULTS

We retrospectively analyzed ECGs from 1906 healthy volunteers from 41 phase I studies. QT interval was measured on the median beat in all 12 leads. The mean difference in QT interval between lead aVR and in Lead II was the least, followed by aVF, V5, V6 and V4; lead aVL had maximum difference. The T wave was flat (<0.1 mV) in Lead II in 6.9% of ECGs; it was also flat in 20% of these ECGs (1.4% of all ECGs) in Leads aVR, aVF and V5.

CONCLUSIONS

When QT interval cannot be measured in Lead II, the best alternative leads are aVR, aVF, V5, V6 and V4 in that sequence. It differs maximally from that in Lead II in Lead aVL.

Detection of QT prolongation using a novel electrocardiographic analysis algorithm applying intelligent automation: prospective blinded evaluation using the Cardiac Safety Research Consortium electrocardiographic database

BACKGROUND

The Cardiac Safety Research Consortium (CSRC) provides both "learning" and blinded "testing" digital electrocardiographic (ECG) data sets from thorough QT (TQT) studies annotated for submission to the US Food and Drug Administration (FDA) to developers of ECG analysis technologies. This article reports the first results from a blinded testing data set that examines developer reanalysis of original sponsor-reported core laboratory data.

METHODS

A total of 11,925 anonymized ECGs including both moxifloxacin and placebo arms of a parallel-group TQT in 181 subjects were blindly analyzed using a novel ECG analysis algorithm applying intelligent automation. Developer-measured ECG intervals were submitted to CSRC for unblinding, temporal reconstruction of the TQT exposures, and statistical comparison to core laboratory findings previously submitted to FDA by the pharmaceutical sponsor. Primary comparisons included baseline-adjusted interval measurements, baseline- and placebo-adjusted moxifloxacin QTcF changes (ddQTcF), and associated variability measures.

RESULTS

Developer and sponsor-reported baseline-adjusted data were similar with average differences <1 ms for all intervals. Both developer- and sponsor-reported data demonstrated assay sensitivity with similar ddQTcF changes. Average within-subject SD for triplicate QTcF measurements was significantly lower for developer- than sponsor-reported data (5.4 and 7.2 ms, respectively; P < .001).

CONCLUSION

The virtually automated ECG algorithm used for this analysis produced similar yet less variable TQT results compared with the sponsor-reported study, without the use of a manual core laboratory. These findings indicate that CSRC ECG data sets can be useful for evaluating novel methods and algorithms for determining drug-induced QT/QTc prolongation. Although the results should not constitute endorsement of specific algorithms by either CSRC or FDA, the value of a public domain digital ECG warehouse to provide prospective, blinded comparisons of ECG technologies applied for QT/QTc measurement is illustrated.

Levetiracetam: a review of its use in epilepsy

Levetiracetam (Keppra®, E Keppra®) is an established second-generation antiepileptic drug (AED). Worldwide, levetiracetam is most commonly approved as adjunctive treatment of partial onset seizures with or without secondary generalization; other approved indications include monotherapy treatment of partial onset seizures with or without secondary generalization, and adjunctive treatment of myoclonic seizures associated with juvenile myoclonic epilepsy and primary generalized tonic-clonic (GTC) seizures associated with idiopathic generalized epilepsy. Levetiracetam has a novel structure and unique mechanisms of action. Unlike other AEDs, the mechanisms of action of levetiracetam appear to involve neuronal binding to synaptic vesicle protein 2A, inhibiting calcium release from intraneuronal stores, opposing the activity of negative modulators of GABA- and glycin-gated currents and inhibiting excessive synchronized activity between neurons. In addition, levetiracetam inhibits N-type calcium channels. Levetiracetam is associated with rapid and complete absorption, high oral bioavailability, minimal metabolism that consists of hydrolysis of the acetamide group, and primarily renal elimination. It lacks cytochrome P450 isoenzyme-inducing potential and is not associated with clinically significant pharmacokinetic interactions with other drugs, including other AEDs. The efficacy of oral immediate-release levetiracetam in controlling seizures has been established in numerous randomized, double-blind, controlled, multicentre trials in patients with epilepsy. Adjunctive levetiracetam reduced the frequency of seizures in paediatric and adult patients with refractory partial onset seizures to a significantly greater extent than placebo. Monotherapy with levetiracetam was noninferior to that with carbamazepine controlled release in controlling seizures in patients with newly diagnosed partial onset seizures. Levetiracetam also provided seizure control relative to placebo as adjunctive therapy in patients with idiopathic generalized epilepsy with myoclonic seizures or GTC seizures. In addition, patients receiving oral levetiracetam showed improvements in measures of health-related quality of life relative to those receiving placebo. Although treatment-emergent adverse events were commonly reported in the clinical trials of levetiracetam, the overall proportion of patients who experienced at least one treatment-emergent adverse event was broadly similar in the levetiracetam and placebo treatment groups, with most events being mild to moderate in severity. Levetiracetam is not associated with cognitive impairment or drug-induced weight gain, but has been associated with behavioural adverse effects in some patients.

Highly automated QT measurement techniques in 7 thorough QT studies implemented under ICH E14 guidelines

Thorough QT (TQT) studies are designed to evaluate potential effect of a novel drug on the ventricular repolarization process of the heart using QTc prolongation as a surrogate marker for torsades de pointes. The current process to measure the QT intervals from the thousands of electrocardiograms is lengthy and expensive. In this study, we propose a validation of a highly automatic-QT interval measurement (HA-QT) method. We applied a HA-QT method to the data from 7 TQT studies. We investigated both the placebo and baseline-adjusted QTc interval prolongation induced by moxifloxacin (positive control drug) at the time of expected peak concentration. The comparative analysis evaluated the time course of moxifloxacin-induced QTc prolongation in one study as well. The absolute HA-QT data were longer than the FDA-approved QTc data. This trend was not different between ECGs from the moxifloxacin and placebo arms: 9.6 ± 24 ms on drug and 9.8 ± 25 ms on placebo. The difference between methods vanished when comparing the placebo-baseline-adjusted QTc prolongation (1.4 ± 2.8 ms, P = 0.4). The differences in precision between the HA-QT and the FDA-approved measurements were not statistically different from zero: 0.1 ± 0.1 ms (P = 0.7). Also, the time course of the moxifloxacin-induced QTc prolongation adjusted for placebo was not statistically different between measurements methods.

Levofloxacin can be used effectively as a positive control in thorough QT/QTc studies in healthy volunteers

AIMS

To characterize the effects of levofloxacin on QT interval in healthy subjects and the most appropriate oral positive control treatments for International Conference on Harmonization (ICH) E14 QT/QTc studies.

METHODS

Healthy subjects received a single dose of levofloxacin (1000 or 1500 mg), moxifloxacin (400 mg) or placebo in a four-period crossover design. Digital 12-lead ECGs were recorded in triplicate. Measurement of QT interval was performed automatically with subsequent manual onscreen over-reading using electronic callipers. Blood samples were taken for determination of levofloxacin and moxifloxacin concentrations.

RESULTS

Mean QTcI (QT interval corrected for heart rate using a correction factor that is applicable to each individual) was prolonged in subjects receiving moxifloxacin 400 mg compared with placebo. The largest time-matched difference in QTcI for moxifloxacin compared with placebo was observed to be 13.19 ms (95% confidence interval 11.21, 15.17) at 3.5 h post dose. Prolonged mean QTcI was also observed in subjects receiving levofloxacin 1000 mg and 1500 mg compared with placebo. The largest time-matched difference in QTcI compared with placebo was observed at 3.5 h post dose for both 1000 mg and 1500 mg of levofloxacin [mean (95%) 4.42 ms (2.44, 6.39) in 1000 mg and 7.44 ms (5.47, 9.42) in 1500 mg]. A small increase in heart rate was observed with levofloxacin during the course of the study. However, moxifloxacin showed a greater increase compared with levofloxacin.

CONCLUSIONS

Both levofloxacin and moxifloxacin can fulfil the criteria for a positive comparator. The ICH E14 guidelines recommend a threshold of around 5 ms for a positive QT/QTc study. The largest time-matched difference in QTc for levofloxacin suggests the potential for use in more rigorous QT/QTc studies. This study has demonstrated the utility of levofloxacin on the assay in measuring mean QTc changes around 5 ms.

Safety and tolerability of commonly prescribed oral antibiotics for the treatment of respiratory tract infections

Recent data suggest that adverse events (AEs) associated with the use of antimicrobial drugs are a major safety concern, with antibiotics implicated in a significant proportion (approximately 20%) of all drug-related emergency department visits in the United States. Although most of these visits are attributable to allergic reactions (79%), certain commonly prescribed antibiotics are notable contributors to conditions that range in nature from gastrointestinal to neurologic and/or psychiatric--particularly after ED visits are adjusted per outpatient prescription visits. This article reviews medically significant AEs of agents included in the major antimicrobial classes--AEs that may be underappreciated by general practitioners. Considerable attention is devoted to the fluoroquinolone agents. Also discussed are the assessment procedures of regulatory agencies in Europe and the United States that are in place to evaluate antimicrobial safety more accurately. Offsetting potential risks and benefits associated with currently available antimicrobials in a climate in which new agents are desperately needed to combat continually evolving multiresistant pathogens remains an interesting dilemma in antimicrobial therapy.

The thorough QT/QTc study 4 years after the implementation of the ICH E14 guidance

The ICH E14 guidance on how to clinically assess a new drug's liability to prolong the QT interval was adopted in May 2005. A centre-piece of the guidance was the establishment of one single trial, the 'thorough QT/QTc study', intended to confidently identify drugs that may cause QT prolongation. Initially perceived as a great challenge, this study has rapidly become a standard component of all clinical development programs for new molecular entities. The study is normally conducted in healthy volunteers, includes both a positive and a negative (placebo) control and is stringently powered to exclude an effect on the QTc interval exceeding 10 ms. The E14 guidance was intentionally not very prescriptive and allowed sponsors and service providers to explore new methodologies. This has allowed for a rapid development of new methods during the first years after the guidance's implementation, such as computer-assisted algorithms for QT measurements. Regulators have worked in close collaboration with pharmaceutical industry to set standards for the design and conduct of the 'thorough QT/QTc study', which therefore has evolved as a key component of cardiac safety assessment of new drugs. This paper summarizes the requirements on the 'thorough QT/QTc study' with emphasis on the standard that has evolved based on interactions between regulators and sponsors and the experience from a large number of completed studies.

Absence of effect of telbivudine on cardiac repolarization: results of a thorough QT/QTc study in healthy participants

The effect of telbivudine on cardiac repolarization was evaluated in healthy participants at clinical and supratherapeutic doses. Sixty-two participants were enrolled, stratified by sex, and randomized according to a crossover design among 4 treatment sequences: placebo, a single moxifloxacin 400-mg dose as positive calibrator, and telbivudine 600 and 1800 mg/d for 7 days. Intensive time-matched electrocardiogram measurements and pharmacokinetic sampling were performed at baseline and on day 7 over 24 hours. For telbivudine and moxifloxacin, time-matched, placebo-adjusted change from baseline in QT was calculated and corrected using Fridericia's formula (QTcF). While moxifloxacin produced the expected significant changes in QTcF, none of the changes in QTcF for either doses of telbivudine exceeded 5 ms, and none of the associated upper 1-sided 95% confidence intervals (CI) exceeded the limit of 10 ms. There was no increase in QTcF with increasing plasma telbivudine. The supratherapeutic dose of telbivudine was well tolerated with a safety profile similar to the clinical dose despite a 3-fold increase in plasma exposure. This study therefore met the criteria for a negative thorough QT study. Telbivudine had no adverse effect on cardiac repolarization in healthy participants, even at supratherapeutic exposure, suggesting a broad safety margin.

Update on the evaluation of a new drug for effects on cardiac repolarization in humans: issues in early drug development

Following reports of death from cardiac arrhythmias with drugs like terfenadine and cisapride, the International Conference for Harmonization formulated a guidance (E14) document. This specifies that all new drugs must undergo a 'thorough QT/QTc' (TQT) study to detect drug-induced QT prolongation, a surrogate marker of ventricular tachycardia, especially torsades de pointes (TdPs). With better understanding of data from several completed TQT studies, regulatory requirements have undergone some changes since the E14 guidance was implemented in October 2005. This article reviews the implications of the E14 guidance and the changes in its interpretation including choice of baseline QT, demonstration of assay sensitivity, statistical analysis of the effect of new drug and positive control, and PK-PD modelling. Some issues like use of automated QT measurements remain unresolved. Pharmaceutical companies too are modifying Phase 1 studies to detect QTc liability early in order to save time and resources. After the E14 guidance, development of several drugs that prolong QTc by >5 ms is being abandoned by sponsors. However, all drugs that prolong the QT interval do not increase risk of TdP. Researchers in regulatory agencies, academia and industry are working to find better biomarkers of drug-induced TdP which could prevent many useful drugs from being prematurely abandoned. Drug-induced TdP is a rare occurrence. With fewer drugs that prolong QT interval reaching the licensing stage, knowing which of these drugs are torsadogenic is proving to be elusive. Thus, paradoxically, the effectiveness of the E14 guidance itself has made prospective validation of new biomarkers difficult.

Effect of brivaracetam on cardiac repolarisation--a thorough QT study

OBJECTIVES

To assess the effect on cardiac repolarisation of the investigational synaptic vesicle protein 2A (SV2A) ligand brivaracetam.

RESEARCH DESIGN AND METHODS

Subjects received double-blind, multiple bid doses of placebo (n = 53), brivaracetam 75 mg (n = 39) or brivaracetam 400 mg (n = 40), or open-label single-dose moxifloxacin 400 mg (positive control, n = 52). Continuous 12-lead ECG recordings were performed at baseline and after last dosing, using a Mortara Holter device. Plasma samples were obtained before and up to 12 h after last dosing for drug determination. Triplicate ECGs were extracted before each sample, and read centrally in a blinded manner. QT was corrected using a centre- and gender-specific correction (QTc(SS) ).

MAIN OUTCOME MEASURES

The primary endpoint was the largest time-matched mean difference of QTc(SS) change from baseline between drug and placebo (maximum DeltaDeltaQTc(SS)). The same approach was adopted using the Fridericia's correction (QTc(F)). The relationships between DeltaQTc(SS) and plasma concentration of brivaracetam and moxifloxacin were fitted to a straight line using linear least-squares regression.

RESULTS

Mean maximum DeltaDeltaQTc(SS) for brivaracetam 75 and 400 mg bid, and moxifloxacin 400 mg was 0.2 ms, -1.1 ms and 12.4 ms, respectively. The one-sided 95% upper limit for 75 mg and 400 mg brivaracetam was 4.3 ms and 3.0 ms, respectively; the one-sided 95% lower limit for moxifloxacin was 8.6 ms. After brivaracetam no QTc(SS) intervals > 480 ms or changes from baseline of > 60 ms were observed. DeltaQTc(SS) did not increase with plasma concentration of brivaracetam, whereas there was a statistically significant rise with increasing moxifloxacin concentrations.

CONCLUSIONS

The study was found to be valid in terms of assay sensitivity and the results demonstrated the absence of effects of brivaracetam on cardiac repolarisation. These results suggest that no intensive cardiac monitoring is required during the subsequent stages of brivaracetam development.