Clinical evaluation of QT/QTc prolongation and proarrhythmic potential for nonantiarrhythmic drugs: the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use E14 guideline

Effect of number of replicate electrocardiograms recorded at each time point in a thorough QT study on sample size and study cost

In a "thorough QT/QTc" (TQT) study, several replicate electrocardiograms (ECGs) are recorded at each time point to reduce within-subject variability. This decreases the sample size but increases the cost of ECG analysis. To determine the most cost-effective number of ECG replicates, the authors retrospectively analyzed data from the placebo and moxifloxacin arms of a TQT study with crossover design. Six replicate ECGs were recorded at 7 time points on day -1 (baseline day), day 1, and day 3 in 124 normal healthy volunteers who were randomized to receive moxifloxacin or placebo on day 1 and the other treatment on day 3. QT interval was corrected for heart rate by the Fridericia (QTcF) and individual subject-specific (QTcI) formulas. Within-subject and between-subject standard deviations for QTcF obtained by repeated-measures analysis of covariance were 9.5 and 13.3 milliseconds with 1 replicate; 7.8 and 12.7 milliseconds with 2 replicates; 7.3 and 12.3 milliseconds with 3 replicates; 6.9 and 12.2 milliseconds with 4 replicates; 6.8 and 11.9 milliseconds with 5 replicates; and 6.6 and 11.8 milliseconds with 6 replicates. Within- and between-subject variance with QTcI also declined with increasing replicates. Sample size benefit based on these estimates was negligible beyond 4 replicates. The study cost was least with 3 or 4 replicates, depending on per-ECG and per-subject costs.

A decade of safety-related regulatory action in the Netherlands: a retrospective analysis of direct healthcare professional communications from 1999 to 2009

BACKGROUND

As pre-approval trials are inherently limited in assessing the complete benefit-risk profile of a new drug, serious safety issues may emerge once a drug gains widespread use after approval. Regulators face the dilemma of balancing timely market access with the need for complete data on risks. This challenge has led to a life-cycle approach but, so far, few data are available on post-approval safety issues requiring regulatory action.

OBJECTIVE

The aim of this study is to determine the frequency, timing and nature of safety issues that necessitated safety-related regulatory action in the form of a Direct Healthcare Professional Communication (DHPC) issued by pharmaceutical companies in collaboration with the Dutch Medicines Evaluation Board during the past decade.

METHODS

All DHPCs issued in the Netherlands from 1 January 1999 to 1 January 2009 were retrospectively collected from the national regulatory authorities. Elapsed time between the approval date and the issue of the DHPC was determined. Characteristics of the action including the nature of the safety issue (according to Medical Dictionary for Regulatory Activities [MedDRA] terminology), type of drug and procedural aspects of the regulatory action taken were reviewed. DHPC characteristics were tabulated and explorative non-parametric tests were performed to study the effect of safety issue, drug class, drug type, orphan drug and first-in-class status on elapsed time from approval to the DHPC.

RESULTS

157 DHPCs were issued concerning 112 different active substances, approximately 9% (112/1200) of active substances available in the Netherlands in 2007. The number of DHPCs issued increased by 2.1 (95% CI 1.2, 3.1; p < 0.001) DHPCs per year over the past decade, reaching a total of 25 in 2008. The median time between approval and DHPC was 5.3 years (range 0.13-48 years). No significant trend in elapsed time to DHPC was observed in relation to the studied years (p = 0.06). One-third of all DHPCs were issued in the first 3 years after approval, but 27% (n = 43/157) of the DHPCs were issued 10 or more years after approval. Timing of DHPCs differed depending on safety issue, drug class, drug type and orphan drug status. DHPCs mostly concerned adverse events in the system organ class of 'cardiac disorders' (15%), 'injury, poisoning and procedural complications' (13%) and 'general disorders and administration site conditions' (10%). In ten cases the drug was eventually withdrawn. Withdrawal occurred a median duration of 2.4 years after registration (range of 1.5-48 years) and was most frequently due to cardiac disorders (including QT interval prolongation; four occasions) and hepatobiliary disorders (two occasions).

CONCLUSIONS

In the past decade, the number of DHPCs has increased over time. This is likely caused by a multitude of factors: increased risk awareness by the public, media, regulators and other stakeholders; the type of drugs approved, such as orphan drugs and biologicals; and the regulatory process, including conditional approvals. The number of DHPCs may in the future increase further with the possibility of screening large epidemiological databases proactively for adverse drug events. Nine percent of all marketed drugs required a safety-related action. Regulatory action is taken shortly (<3 years) after market approval nearly as often as after intermediate (3-10 years) and long-term (>10 years) market exposure. These findings underline the need for risk management during the whole life cycle of a drug.

Antimicrobials and the risk of torsades de pointes: the contribution from data mining of the US FDA Adverse Event Reporting System

BACKGROUND

Drug-induced torsades de pointes (TdP) is a complex regulatory and clinical problem due to the rarity of this sometimes fatal adverse event. In this context, the US FDA Adverse Event Reporting System (AERS) is an important source of information, which can be applied to the analysis of TdP liability of marketed drugs.

OBJECTIVE

To critically evaluate the risk of antimicrobial-induced TdP by detecting alert signals in the AERS, on the basis of both quantitative and qualitative analyses.

METHODS

Reports of TdP from January 2004 through December 2008 were retrieved from the public version of the AERS. The absolute number of cases and reporting odds ratio as a measure of disproportionality were evaluated for each antimicrobial drug (quantitative approach). A list of drugs with suspected TdP liability (provided by the Arizona Centre of Education and Research on Therapeutics [CERT]) was used as a reference to define signals. In a further analysis, to refine signal detection, we identified TdP cases without co-medications listed by Arizona CERT (qualitative approach).

RESULTS

Over the 5-year period, 374 reports of TdP were retrieved: 28 antibacterials, 8 antifungals, 1 antileprosy and 26 antivirals were involved. Antimicrobials more frequently reported were levofloxacin (55) and moxifloxacin (37) among the antibacterials, fluconazole (47) and voriconazole (17) among the antifungals, and lamivudine (8) and nelfinavir (6) among the antivirals. A significant disproportionality was observed for 17 compounds, including several macrolides, fluoroquinolones, linezolid, triazole antifungals, caspofungin, indinavir and nelfinavir. With the qualitative approach, we identified the following additional drugs or fixed dose combinations, characterized by at least two TdP cases without co-medications listed by Arizona CERT: ceftriaxone, piperacillin/tazobactam, cotrimoxazole, metronidazole, ribavirin, lamivudine and lopinavir/ritonavir.

DISCUSSION

Disproportionality for macrolides, fluoroquinolones and most of the azole antifungals should be viewed as 'expected' according to Arizona CERT list. By contrast, signals were generated by linezolid, caspofungin, posaconazole, indinavir and nelfinavir. Drugs detected only by the qualitative approach should be further investigated by increasing the sensitivity of the method, e.g. by searching also for the TdP surrogate marker, prolongation of the QT interval.

CONCLUSIONS

The freely available version of the FDA AERS database represents an important source to detect signals of TdP. In particular, our analysis generated five signals among antimicrobials for which further investigations and active surveillance are warranted. These signals should be considered in evaluating the benefit-risk profile of these drugs.

Predicting drug-induced slowing of conduction and pro-arrhythmia: identifying the 'bad' sodium current blockers

BACKGROUND AND PURPOSE

The regulatory guidelines (ICHS7B) for the identification of only drug-induced long QT and pro-arrhythmias have certain limitations.

EXPERIMENTAL APPROACH

Conduction time (CT) was measured in isolated Purkinje fibres, left ventricular perfused wedges and perfused hearts from rabbits, and sodium current was measured in Chinese hamster ovary cells, transfected with Na(v)1.5 channels.

KEY RESULTS

A total of 355 compounds were screened for their effects on CT: 32% of these compounds slowed conduction, 65% had no effect and 3% accelerated conduction. Lidocaine and flecainide, which slow conduction, were tested in more detail as reference compounds. In isolated Purkinje fibres, flecainide largely slowed conduction and markedly increased triangulation, while lidocaine slightly slowed conduction and did not produce significant triangulation. Also in isolated left ventricular wedge preparations, flecainide largely slowed conduction in a rate-dependent manner, and elicited ventricular tachycardia (VT). Lidocaine slightly slowed conduction, reduced Tp-Te and did not induce VT. Similarly in isolated hearts, flecainide markedly slowed conduction, increased Tp-Te and elicited VT or ventricular fibrillation (VF). The slowing of conduction and induction of VT/VF with flecainide was much more evident in a condition of ischaemia/reperfusion. Lidocaine abolished ischaemia/reperfusion-induced VT/VF. Flecainide blocked sodium current (I(Na)) preferentially in the activated state (i.e. open channel) with slow binding and dissociation rates in a use-dependent manner, and lidocaine weakly blocked I(Na).

CONCLUSION AND IMPLICATIONS

Slowing conduction by blocking I(Na) could be potentially pro-arrhythmic. It is possible to differentiate between compounds with 'good' (lidocaine-like) and 'bad' (flecainide-like) I(Na) blocking activities in these models.

Thorough QT Studies: Questions and Quandaries

The International Conference on Harmonisation E14 Guidance was successful in largely standardizing the conduct of the so-called thorough QT/QTc studies (TQTS). Nevertheless, there is still a spectrum of frequently encountered problems with details of design, conduct and interpretation of TQTS. Several of these challenges are reviewed here, starting with explaining that the TQTS goal is only to identify drugs for which the proarrhythmic risk might be considered excluded for the purposes of regulatory benefit-risk assessment. Suggestions are made on how to categorize and quantify or exclude proarrhythmic risk if the TQTS is positive. There is a conceptual need for TQTS, and this is discussed, together with reasons why restricted clinical registries cannot prove the absence of proarrhythmic liability of any drug. Appropriate drug doses investigated in TQTS should be derived from the maximum clinically tolerable dose rather than from the known or expected therapeutic dose. With the help of concentration-QTc modelling, the standard therapeutic dose can be omitted from TQTS, especially if the study is expected to be negative. Conditions for single-dose TQTS acceptability are reviewed. The role of the so-called positive control is assessed, contrasting the role of a same-class comparator for the investigated drug. A single 400 mg dose of moxifloxacin is advocated as the present 'gold standard' assay sensitivity test. The necessity of careful placebo control is explained and the frequency of ECG assessments is considered. The central tendency and outlier analyses are discussed, together with the correct approaches to baseline adjustment. The review concludes that the design and interpretation of TQTS must not be approached with mechanistic stereotypes, and highlights the importance of relating the QTc changes to drug plasma levels.

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.

Rupatadine: pharmacological profile and its use in the treatment of allergic rhinitis

Rupatadine is a once-daily, non-sedating, selective and long-acting new drug with a strong antagonist activity towards both histamine H1 receptors and platelet-activating factor receptors. The use of rupatadine is indicated in adult and adolescent patients (>12 years of age) suffering from intermittent and persistent allergic rhinitis. In the treatment of these conditions, rupatadine is at least as effective as ebastine, cetirizine, loratadine and desloratadine. Avery good safety profile of rupatadine has been evidenced in various studies, including a long-term (1-year) safety study. Rupatadine does not present drug-drug interactions with azithromycin, fluoxetine and lorazepam, but should not be administered concomitantly with known CYP3A4 inhibitors.

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.

Absence of QTc prolongation in a thorough QT study with subcutaneous liraglutide, a once-daily human GLP-1 analog for treatment of type 2 diabetes

The objective of this study was to establish effects of liraglutide on the QTc interval. In this randomized, placebo-controlled, double-blind crossover study, 51 healthy participants were administered placebo, 0.6, 1.2, and 1.8 mg liraglutide once daily for 7 days each. Electrocardiograms were recorded periodically over 24 hours at the end of placebo and highest dosing periods. Four different models for QT correction were used: QTci, as the primary endpoint, and QTciL, QTcF, and QTcB as secondary endpoints. The upper bound of the 1-sided 95% confidence interval for time-matched, baseline-corrected, placebo-subtracted QTc intervals was <10 ms for all 4 correction methods. Moxifloxacin (400 mg) increased QTc intervals by 10.6 to 12.3 ms at 2 hours. There was no concentration-exposure dependency on QTc interval changes by liraglutide and no QTc thresholds above 500 ms or QTc increases >60 ms. The authors conclude that liraglutide caused no clinically relevant increases in the QTc interval.

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

BACKGROUND

Nonantiarrhythmic drugs may have the potential to prolong the QT interval, leading to potentially fatal ventricular tachycardias, including torsades de pointes.

OBJECTIVE

This study evaluated the potential of the newer-generation, multiple-action antiepileptic drug levetiracetam, which binds to the synaptic vesicle protein SV2A, to affect cardiac repolarization, as detected by prolongation of the QT/corrected QT (QTc) interval.

METHODS

This was a single-dose, randomized, placebo- and active-controlled, 4-way crossover study in healthy subjects. Subjects were randomly allocated to 1 of 4 different administration sequences. Each sequence included 3 double-blind treatments (levetirace-tam 1000 mg, levetiracetam 5000 mg, and placebo) and 1 open-label treatment (moxifloxacin 400 mg). Triplicate electrocardiograms (ECGs) were obtained at baseline and at various time points over 24 hours after each treatment using continuous Holter monitoring. ECGs were read centrally in a blinded manner. Blood samples for the determination of plasma concentrations of levetiracetam and moxifloxacin were collected before dosing and at 0.5, 1, 1.5, 2, 4, 6, 12, and 24 hours after dosing, within 5 minutes after the ECG recordings. The QT interval was corrected for heart rate using a sex- and study-specific correction (QTc(ss)) as the primary outcome measure and Fridericia's correction (QTc(F))as a secondary outcome measure. The primary analysis was performed on the time-matched, baseline-subtracted QTc(ss) (DeltaQTc(ss)). The maximum DeltaQTc(ss) difference between each active treatment and placebo (DeltaDeltaTc(ss)) was derived from a mixed-effect analysis of variance. Clinical laboratory tests, standard 12-lead ECGs, and vital signs were monitored at regular intervals. Spontaneously reported adverse events were recorded throughout the study.

RESULTS

Fifty-two healthy, nonsmoking subjects (26 men, 26 women; 37 white, 9 black, 3 Hispanic, and 3 Asian/Pacific Islander) with a mean (SD) age of 28.4 (7.5) years (range, 18-45 years) and a mean weight of 71.5 (12.6) kg (range, 49-103 kg) participated in the study. Levetiracetam did not significantly prolong the QTc(ss). The upper bound of the 1-sided 95% CI for the maximum DeltaDeltaTc(ss) was 8.0 milliseconds for levetiracetam 1000 mg and 8.1 milliseconds for levetiracetam 5000 mg, with mean estimates of 4.0 and 4.1 milliseconds, respectively; similar results were obtained for the maximum DeltaDeltaQTc(F). Moxifloxacin significantly prolonged the QTc(ss), with a lower bound of the 1-sided 95% CI for the maximum DeltaDeltaQTc(ss) of 3.7 milliseconds and a mean estimate of 7.7 milliseconds. There was no statistically significant relationship between measured DeltaQTc(ss) and the levetiracetam plasma concentration, whereas a significant linear relationship was observed between measured DeltaQTc(ss) and the moxifloxacin plasma concentration (slope estimate: 4.4 milliseconds/[microg/mL]); 95% CI, 3.2-5.7; P < 0.001). No unexpected safety concerns arose based on reported adverse events, clinical laboratory evaluations, physical examinations, vital signs, or ECG monitoring during the course of the study.

CONCLUSION

This randomized, placebo- and active-controlled study in healthy adult subjects found no clinically relevant changes in the QTc interval after a single levetiracetam dose of 1000 or 5000 mg.

Collation, assessment and analysis of literature in vitro data on hERG receptor blocking potency for subsequent modeling of drugs' cardiotoxic properties

The assessment of the torsadogenic potency of a new chemical entity is a crucial issue during lead optimization and the drug development process. It is required by the regulatory agencies during the registration process. In recent years, there has been a considerable interest in developing in silico models, which allow prediction of drug-hERG channel interaction at the early stage of a drug development process. The main mechanism underlying an acquired QT syndrome and a potentially fatal arrhythmia called torsades de pointes is the inhibition of potassium channel encoded by hERG (the human ether-a-go-go-related gene). The concentration producing half-maximal block of the hERG potassium current (IC(50)) is a surrogate marker for proarrhythmic properties of compounds and is considered a test for cardiac safety of drugs or drug candidates. The IC(50) values, obtained from data collected during electrophysiological studies, are highly dependent on experimental conditions (i.e. model, temperature, voltage protocol). For the in silico models' quality and performance, the data quality and consistency is a crucial issue. Therefore the main objective of our work was to collect and assess the hERG IC(50) data available in accessible scientific literature to provide a high-quality data set for further studies.

A simple approach discriminating cardio-safe drugs from toxic ones

More than 130 FDA-approved drugs have been identified for now to prolong the QT interval and possibly lead to sudden cardiac death. Due to their toxic effect, some of these drugs have been withdrawn from the pharmaceutical market. In this study, we have formulated few rules to assess the ability to prolong QT interval and thereby discriminate between cardiotoxic and -safe drugs. These rules have clearly determined that cardio-toxic drugs are more likely to obey Lipinski rule of 5 and Oprea lead-like rule. Moreover, the cardio-toxic drugs have been found to have in common values of -0.5 to 6.5 log P, 1-5 nitrogen atoms, up to 4 oxygen atoms, 5-27 hydrophobic atoms, and 15-53 single bonds. Matthews Correlation Coefficient with the value of 0.6 was also attained and nearly 96% of the cardio-toxic drugs were successfully covered. Thus, despite the simplicity of this methodology, we have obtained interesting and informative results. The proposed set of these simple rules could be employed to infer cardio-toxicity or -safety for current and potential drugs. The present study will have important impact on decision making in the fields of drug development, molecule screening in biological assays, and other applications as well.

Comparison of QTinno, a fully automated electrocardiographic analysis program, to semiautomated electrocardiographic analysis methods in a drug safety study in healthy subjects

BACKGROUND

Improved automated methods for electrocardiographic (ECG) analysis are needed, particularly for drug development purposes.

OBJECTIVES

This study compared a novel fully automated method for ECG analysis (QTinno; NewCardio, Santa Clara, CA) to 2 semiautomated digital methods: global measurement from the earliest QRS onset to the latest T-wave offset on representative superimposed beats (global) and tangent measurement on 3 consecutive beats in one lead (tangent).

METHODS

All 3 methods were used to determine uncorrected and rate-corrected QT interval duration (QT and QTcF) and related metrics in 1422 digital 12-lead ECGs from a phase 1 drug study. Global and tangent annotations were manually adjusted by the same 3 cardiologists wherever necessary. No adjustments were made in QTinno determinations.

RESULTS

QTinno returned QTcF change from time-matched baseline (DeltaQTcF) that differed minimally from both global and tangent methods (mean pairwise difference: 0.1 millisecond between QTinno and global, 1.1 milliseconds between QTinno and tangent). The average absolute QT and QTcF intervals by QTinno were approximately 5 milliseconds longer than global and 25 milliseconds longer than by tangent. QTinno had lower intrinsic variability for DeltaQTcF than either global or tangent (between-subject SD: QTinno 4.0 milliseconds, global 5.6 milliseconds, tangent 6.4 milliseconds; within-subject SD: QTinno 4.8 milliseconds, global 7.4 milliseconds, tangent 10.6 milliseconds). All methods were robust in detecting the largest placebo-adjusted mean time-matched DeltaQTcF (15-25 milliseconds) induced by study drug.

CONCLUSIONS

The methods show good agreement for drug-induced QTc prolongation. Lower intrinsic variability of DeltaQTcF by QTinno could facilitate smaller sample sizes or increase study power in thorough QTc studies.

Does artesunate prolong the electrocardiograph QT interval in patients with severe malaria?

Several antimalarials can cause significant prolongation of the electrocardiograph QT interval, which can be associated with an increased risk of potentially lethal ventricular arrhythmias. High doses of artemether and artemotil have been associated with QT prolongation in dogs, raising the possibility of a class effect with the artemisinin derivatives. Serial electrocardiograms were recorded, and QTc interval was calculated before and after administration of artesunate by intravenous injection in patients with severe falciparum malaria in Bangladesh. Of 21 adult patients with severe malaria enrolled, 8 (38%) died. The mean QTc interval was unaffected by bolus intravenous artesunate (2.4 mg/kg). In two patients, the QTc interval exceeded 0.5 seconds, but in both cases, an alternative explanation was plausible. No effect was observed on the JTc or PR interval, QRS width, blood pressure, or heart rate. Intravenous artesunate does not have significant cardiovascular effects in patients with severe falciparum malaria.

Exposure to antibacterial agents with QT liability in 14 European countries: trends over an 8-year period

AIMS

(i) To classify antibacterial agents with QT liability on the basis of the available evidence, and (ii) to assess trends in their consumption over an 8-year period (1998-2005) in 14 European countries.

METHODS

Current published evidence on QT liability of antibiotics was retrieved through MEDLINE search and joined to official warnings from regulatory agencies. Each drug was classified according to an already proposed algorithm based on the strength of evidence: from group A (any evidence) to group E (clinical reports of torsades de pointes and warnings on QT liability). Consumption data were provided by the European Surveillance of Antibacterial Consumption (ESAC) project and were expressed as defined daily doses per 1000 inhabitants per day (DID).

RESULTS

Among 21 detected compounds, nine [six fluoroquinolones (FQs) and three macrolides (MACs)] belonged to group E. Use of group E drugs ranged from 1.3 (Sweden) to 4.1 DID (Italy) in 1998 and from 1.2 (Sweden) to 6.5 DID (Italy) in 2005. Significant exposure was observed in Italy and Spain (6.5 and 3.8 DID, respectively, in 2005). Only Denmark, Sweden and UK showed a slight decrease in use. Exposure to clarithromycin increased in 10 out of 14 countries, with a marked increment in Italy (3 DID in 2005).

CONCLUSIONS

Notwithstanding regulatory measures, in 2005 there was still significant exposure to antibacterials with strong evidence of QT liability and, in most countries, it was even increased. This warrants further investigation of appropriateness of use and suggests closer monitoring of group E drugs. Physicians should be aware when prescribing them to susceptible patients.

Cardiac arrest from acquired long QT syndrome: a case report

BACKGROUND

Many classes of medications initiated by clinicians can cause adverse events, such as cardiac disturbances. One such adverse outcome is that of acquired long QT syndrome, which can lead to arrhythmias and sudden death. When health care practitioners were surveyed about their knowledge of this condition, 20% indicated they knew very little about long QT syndromes and more than 30% failed to check on current therapy before prescribing QT-prolonging medications.

METHODS

A case will be presented to illustrate the importance of understanding this syndrome.

RESULTS

The causes and pathophysiology of acquired long QT syndrome are discussed, and the resources for clinicians to obtain more information and growing number of offending medications leading to acquired long QT syndrome are provided.

CONCLUSIONS

On-going education is needed to heighten awareness in the health care community to prevent the deleterious outcomes associated with medication induced acquired long QT syndrome.

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.

Principles of safety pharmacology

Safety Pharmacology is a rapidly developing discipline that uses the basic principles of pharmacology in a regulatory-driven process to generate data to inform risk/benefit assessment. The aim of Safety Pharmacology is to characterize the pharmacodynamic/pharmacokinetic (PK/PD) relationship of a drug's adverse effects using continuously evolving methodology. Unlike toxicology, Safety Pharmacology includes within its remit a regulatory requirement to predict the risk of rare lethal events. This gives Safety Pharmacology its unique character. The key issues for Safety Pharmacology are detection of an adverse effect liability, projection of the data into safety margin calculation and finally clinical safety monitoring. This article sets out to explain the drivers for Safety Pharmacology so that the wider pharmacology community is better placed to understand the discipline. It concludes with a summary of principles that may help inform future resolution of unmet needs (especially establishing model validation for accurate risk assessment). Subsequent articles in this issue of the journal address specific aspects of Safety Pharmacology to explore the issues of model choice, the burden of proof and to highlight areas of intensive activity (such as testing for drug-induced rare event liability, and the challenge of testing the safety of so-called biologics (antibodies, gene therapy and so on.).

Key clinical considerations for demonstrating the utility of preclinical models to predict clinical drug-induced torsades de pointes

While the QT/QTc interval is currently the best available clinical surrogate for the development of drug-induced torsades de pointes, it is overall an imperfect biomarker. In addition to low specificity for predicting arrhythmias, other issues relevant to using QT as a biomarker include (1) an apparent dissociation, for some drugs (for example, amiodarone, sodium pentobarbital, ranolazine) between QT/QTc interval prolongation and TdP risk, (2) Lack of clarity regarding what determines the relationship between QTc prolongation and TdP risk for an individual drug, (3) QT measurement issues, including effects of heart rate and autonomic perturbations, (4) the significant circadian changes to the QT/QTc interval and (5) concerns that the development, regulatory and commercial implications of finding even a mild QT prolongation effect during clinical development has significant impact the pharmaceutical discovery pipeline. These issues would be significantly reduced, clinical development simplified and marketing approval for some drugs might be accelerated if there were a battery of preclinical tests that could reliably predict a drug's propensity to cause TdP in humans, even in the presence of QTc interval prolongation. This approach is challenging and for it to be acceptable to pharmaceutical developers, the scientific community and regulators, it would need to be scientifically well validated. A very high-negative predictive value demonstrated in a wide range of drugs with different ionic effects would be critical. This manuscript explores the issues surrounding the use of QT as a clinical biomarker and potential approaches for validating preclinical assays for this purpose against clinical data sets.

Etravirine has no effect on QT and corrected QT interval in HIV-negative volunteers

BACKGROUND

Etravirine (TMC125), a next-generation nonnucleoside reverse transcriptase inhibitor, has shown antiviral efficacy in 2 large Phase 3 trials. In vitro and in vivo studies have shown that etravirine is not associated with proarrhythmic potential. Electrocardiograms (ECGs) from healthy and HIV 1-infected volunteers showed no clinically relevant changes.

OBJECTIVE

To evaluate the effect of 2 etravirine dosing regimens on QT/corrected QT interval (QTc) in HIV-negative volunteers and assess pharmacokinetic and additional safety parameters.

METHODS

A double-blind, double-dummy, randomized, placebo- and active-controlled, 4-period crossover trial was conducted in 41 HIV-negative volunteers. Participants received 4 regimens: etravirine 200 mg twice daily, etravirine 400 mg once daily, moxifloxacin 400 mg once daily (positive control), and placebo in separate 8-day sessions, with each followed by a washout period of 14 or more days. On days -1, 1, and 8 of each session, ECGs were recorded at 11 time points over 12 hours. Pharmacokinetic profiles of etravirine regimens were evaluated and safety was assessed.

RESULTS

Thirty-seven subjects completed the study. For etravirine, the upper limit of the 90% CIs of mean time-matched differences in QTc determined using Fridericia's formula (QTcF) was below 10 msec at all time points, the threshold for prolonged QT as defined by regulatory guidelines. The maximum mean (90% CI) difference of time-matched changes in QTcF versus placebo on day 1 was +0.1 msec (-2.6 to 2.9), -0.2 msec (-2.6 to 2.1), and +10.1 msec (7.3 to 12.8) for etravirine 200 mg twice daily, etravirine 400 mg once daily, and moxifloxacin, respectively. On day 8, these values were +0.6 msec (-2.1 to 3.3), -1.0 msec (-4.4 to 2.5), and +10.3 msec (6.8 to 13.9), respectively. Etravirine produced no clinically significant changes in other ECG parameters. No significant differences between males and females were observed. Both etravirine regimens had similar pharmacokinetic exposure and safety profiles.

CONCLUSIONS

Etravirine does not prolong the QTc interval. No clinically relevant ECG changes were observed in HIV-negative volunteers. Short-term dosing of etravirine in HIV-negative volunteers was generally safe and well tolerated.

Effect of single doses of maraviroc on the QT/QTc interval in healthy subjects

AIMS

To assess the effect of a single dose of maraviroc on the QTc interval in healthy subjects and to evaluate the QTc interval-concentration relationship.

METHODS

A single-dose, placebo- and active-controlled, five-way crossover study was conducted to investigate the effects of maraviroc (100, 300, 900 mg) on QTc in healthy subjects. Moxifloxacin (400 mg) was used as the active comparator. The study was double-blind with respect to maraviroc/placebo and open label for moxifloxacin. There was a 7-day wash-out period between each dose. QT interval measurements obtained directly from the electrocardiogram (ECG) recorder were corrected for heart rate using Fridericia's correction (QTcF). A placebo run-in day was conducted before period 3, when ECGs were collected at intervals while subjects were resting or during exercise. These ECGs plus other predose ECGs were used to evaluate the QT/RR relationship for each subject to enable calculation of an individual's heart rate correction for their QT measurements (QTcI). ECGs were taken at various intervals pre- and postdose in each study period. Pharmacokinetic parameters were determined for each maraviroc dose. The end-points that were evaluated were QTcF at median time to maximum concentration (T(max)) based on the machine readings and QTcI at median T(max) based on manual over-reads of the QT/RR data. A separate analysis of variance was used for each of the pair-wise comparisons for each end-point. The relationship between QTc interval and plasma concentration was also investigated using a mixed-effects modelling approach, as implemented by the NONMEM software system. A one-stage model was employed in which the relationship between QT and RR and the effects of maraviroc plasma concentration on QT were estimated simultaneously.

RESULTS

The mean difference from placebo in machine-read QTcF at median T(max) for maraviroc 900 mg was 3.6 ms [90% confidence interval (CI) 1.5, 5.8]. For the active comparator, moxifloxacin, the mean difference from placebo in machine-read QTcF was 13.7 ms. The changes from placebo for each of the end-points were similar for men and women. No subjects receiving maraviroc or placebo had a QTcF > or = 450 ms (men) or QTcF > or = 470 ms (women), nor did any subject experience a QTcF increase > or = 60 ms from baseline at any time point. Analysis based on the QTcI data obtained from the manual over-readings of the ECGs gave numerically very similar results. The QT:RR relationship was similar pre- and postdose and was not related to maraviroc concentration. The population estimate of the QT:RR correction factor was 0.324 (95% CI 0.309, 0.338). The population estimate of the slope describing the QT-concentration relationship was 0.97 micros ml ng(-1) (95% CI -0.571, 2.48), equivalent to an increase of 0.97 ms in QT per 1000 ng maraviroc plasma concentration. Most adverse events were mild to moderate in severity.

CONCLUSIONS

Single doses of maraviroc, up to and including 900 mg, had no clinically relevant effect on QTcF or QTcI. At all maraviroc doses and for both end-points, the mean difference from placebo for QTc was < 4 ms. There was no apparent relationship between QT interval and maraviroc plasma concentration up to 2363 ng ml(-1). This conclusion held in both male and female subjects, and there was no evidence of a change in the QT/RR relationship with concentration.

Quality assessment of digital annotated ECG data from clinical trials by the FDA ECG Warehouse

The FDA mandates that digital electrocardiograms (ECGs) from 'thorough' QTc trials be submitted into the ECG Warehouse in Health Level 7 extended markup language format with annotated onset and offset points of waveforms. The FDA did not disclose the exact Warehouse metrics and minimal acceptable quality standards. The author describes the Warehouse scoring algorithms and metrics used by FDA, points out ways to improve FDA review and suggests Warehouse benefits for pharmaceutical sponsors. The Warehouse ranks individual ECGs according to their score for each quality metric and produces histogram distributions with Warehouse-specific thresholds that identify ECGs of questionable quality. Automatic Warehouse algorithms assess the quality of QT annotation and duration of manual QT measurement by the central ECG laboratory.

Levocetirizine does not prolong the QT/QTc interval in healthy subjects: results from a thorough QT study

OBJECTIVE

To conduct a thorough QT study of levocetirizine, a non-sedating antihistamine, in accordance with International Conference on Harmonisation (ICH) E14 guidance.

METHODS

The study was designed as a single-dose, placebo and positive-controlled, four-way crossover, randomised trial in which 52 healthy male and female subjects participated. Levocetirizine (5 and 30 mg) and placebo were administered double-blind, and the positive control, moxifloxacin (400 mg), was open-label. Electrocardiograms (ECGs) were obtained by continuous Holter monitoring at various time points (three per time point) during a 24-h period at baseline and after each treatment. The ECGs were read centrally in a blinded manner. QT intervals were corrected for heart rate using a gender- and study-specific correction (QTcSS) and Fridericia's correction (QTcF). The largest QTc time-matched and baseline-subtracted difference between each active drug and the placebo (largest delta delta QTcSS) was derived from a mixed-effect analysis of variance.

RESULTS

The one-sided 95% upper limits of the largest delta delta QTcSS for levocetirizine were 5.7 ms (5 mg) and 3.9 ms (30 mg), with mean estimates of 2.9 and 1.1 ms, respectively. Similar results were obtained for the delta delta QTcF data. Statistically, moxifloxacin significantly lengthened the QTcSS, with a one-sided 95% lower limit of the largest delta delta QTcSS of 10.5 ms and a mean estimate of 13.4 ms. There was no relationship between the measured delta QTcSS and the plasma concentration of levocetirizine, whereas a statistically significant linear relationship was observed with the plasma concentration of moxifloxacin [slope estimate 0.004 ms/(ng/mL); 95% confidence interval: 0.003-0.005].

CONCLUSIONS

Overall, the results of this thorough QT study indicate that the methodology of the trial was valid and sensitive enough to demonstrate the absence of effect of levocetirizine at both therapeutic (5 mg) and supra-therapeutic (30 mg) doses on cardiac repolarisation.

A highly sensitive canine telemetry model for detection of QT interval prolongation: Studies with moxifloxacin, haloperidol and MK-499

INTRODUCTION

Preclinical evaluation of delayed ventricular repolarization manifests electrocardiographically as QT interval prolongation and is routinely used as an indicator of potential risk for pro-arrhythmia (potential to cause Torsades de Pointes) of novel human pharmaceuticals. In accordance with ICH S7A and S7B guidelines we evaluated the sensitivity and validity of the beagle dog telemetry (Integrated Telemetry Services (ITS)) model as a preclinical predictor of QT interval prolongation in humans.

METHODS

Cardiovascular monitoring was conducted for 2 h pre-dose and 24 h post-dosing with moxifloxacin (MOX), haloperidol (HAL), and MK-499, with a toxicokinetic (TK) evaluation in a separate group of dogs. In both cardiovascular and TK studies, MOX (0, 10, 30 and 100 mg/kg), HAL (0, 0.3, 1, 3 mg/kg) and MK-499 (0, 0.03, 0.3 and 3 mg/kg) were administered orally by gavage in 0.5% methylcellulose. Each dog received all 4 doses using a dose-escalation paradigm. Inherent variability of the model was assessed with administration of vehicle (0.5% methylcellulose) alone for 4 days.

RESULTS

Significant increases in QT(c) were evident with 10, 30 and 100 mg/kg of MOX (C(max)< or =40 microM), 0.3, 1 and 3 mg/kg of HAL (C(max)< or =0.36 microM) and 0.3 and 3 mg/kg of MK-499 (C(max)< or =825 nM) with peak increases of 45 (20%), 31 (13%), and 45 (19%) ms, respectively (p< or =0.05).

DISCUSSION

In conclusion, we have demonstrated that the ITS-telemetry beagle dog exhibits low inherent intra-animal variability and high sensitivity to detect small but significant increases in QT/QT(c) interval ( approximately 3-6%) with MOX, HAL and MK-499 in the same range of therapeutic plasma concentrations attained in humans. Therefore, this dog telemetry model should be considered an important preclinical predictor of QT prolongation of novel human pharmaceuticals.

Analysis of the nonclinical telemetered ECG: Impact of logging rate and RR bin width in the dog and cynomolgus monkey

INTRODUCTION

Species-dependent ECG differences may affect QT interval analysis. Among these are the range of QT and RR values, heart rate variability, and respiratory sinus arrhythmia (SA). Importantly, the effects of data logging rates and RR bin width (BW) on QT analysis have not been characterized in dogs and nonhuman primates.

METHODS

Digital ECGs were collected for 18-21 h in telemetered dogs (n=7) and cynomolgus monkeys (n=7) employing epicardial ECG leads and analyzed by computerized algorithms. ECG intervals were determined employing beat-to-beat (1 ms BW) and 10 s logging rates (for 1, 10, 20, and 50 ms BW). Diurnal heart rate variability was defined as the beat-to-beat RR ratio (VR) where SA was defined as >+/-10% change in VR.

RESULTS

Canine beat-to-beat QT-RR data were curvilinear and plateaued, with multiple RR values associated to any given QT for RR>or=900 ms. Cynomolgus QT-RR data collected as beat-to-beat or at a 10 s logging rate were linear for all RR intervals. During the day, SA comprised 62.9+/-2.4% and 11.4+/-6.1% of total beats in the dog and cynomolgus, respectively, with no diurnal/nocturnal differences in either species. QT interval changes varied with BW such that 5 ms resolution was maintained for BW <or=11.5 and 41 ms in the dog and cynomolgus, respectively.

DISCUSSION

Differences in the QT interval, primarily due to SA, were responsible for skewed canine beat-to-beat QT-RR relationships. A 10 s logging rate eliminated this confounding factor, enabling the derivation of accurate QT rate-corrections. Thus, the uniform application of a 10 s logging rate in conjunction with a 10 ms RR BW ensured consistent and accurate QT analysis in both species. In conclusion, optimal BWs were defined which maintained beat-to-beat accuracy, while maximizing the number of QT-RR observations incorporated into QT-RR rate-correction models, a critical factor for robust probabilistic QT rate-corrections.

Ritonavir 100 mg does not cause QTc prolongation in healthy subjects: a possible role as CYP3A inhibitor in thorough QTc studies

To assess the QTc prolongation by ritonavir (RTV) 100 mg and explore its potential use as CYP3A inhibitor in thorough QTc (TQT) studies. Randomized, crossover study of single-dose RTV 100 mg, placebo, and moxifloxacin (MFLX) 400 mg in 65 healthy subjects with serial triplicate electrocardiograms obtained for 12 h post-dose. Largest mean placebo-adjusted QTcF increase from baseline (90% confidence interval (CI)) for RTV 100 mg was noninferior to placebo (0.16 ms (-1.38, 1.69)). Study sensitivity was validated by detecting the largest mean placebo-adjusted QTcF increase from baseline (90% CI) for MFLX of 8.31 ms (6.44, 10.18). A single dose of RTV 100 mg does not cause QTc prolongation in healthy subjects. Based on the potent CYP3A4 inhibition, lack of QTc effect and better safety profile, RTV 100 mg could replace ketoconazole as the CYP3A4 inhibitor in TQT studies.

Clinical Translation of Genotyping and Haplotyping Data

The completion of the Human Genome Project has raised expectations for the translation of genomic knowledge into clinical forms that would lead to improved diagnosis of diseases and identification of new drug targets. Such an opportunity is quite challenging within science and society, although there is still uncertainty regarding its outcomes in new drug development and healthcare. Undoubtedly, however, the recent approval by the US FDA of the first two pharmacogenomic tests for genotyping drug-metabolising enzymes is expected to empower and eventually lead to general applicability of various genetic diagnostic tools to improve pharmacotherapy outcomes in the post-genomic era. To this end, the application of genomic knowledge and technologies in everyday clinical practice leads personalised medicine concepts towards the achievement of individualised drug selection and dosage profiling (i.e. pharmacotyping) for ensuring maximum drug effectiveness and safety. Within this framework, pharmacogenomic information can implement the existing clinical pharmacology experience in clinical diagnosis and drug delivery. The latter can be further advanced through the development of workflow information-based operating systems in healthcare to support the utilisation, assessment and outcome of engaged clinical and genomic information. Such a direction may help to suitably revise and adjust clinical regulatory guidelines as well as clinical pharmacology guidelines. This will further facilitate better designing of clinical trials for new drug development as well as pharmacovigilance registries and evaluation of these data. To critically describe the existing environment, this article comprehensively discusses scientific efforts aimed at making clinical translation of genotyping and haplotyping data more efficient and productive in forms that are readily applicable in everyday healthcare. In addition, specific and systematic pharmacogenomic and clinical attempts related to the development of new molecularly targeted drugs, as well as improvement of the efficacy and safety of commonly prescribed drugs, are presented. To this end, the clinical pharmacogenomic experience gained thus far in the use of tyrosine kinase inhibitors in oncology, as well as the process of empowerment through the use of genomic knowledge of the cardiac safety of drugs modulating the function of the human ether-à-go-go-related gene (HERG) potassium channel, represent examples of how the implementation of clinical experience with genomic information guides the development of new drugs and the improvement of pharmacotherapy outcomes.

Application of a probabilistic method for the determination of drug-induced QT prolongation in telemetered cynomolgus monkeys: effects of moxifloxacin

INTRODUCTION

Moxifloxacin is the most widely used positive reference agent in clinical cardiac repolarization safety studies, but it has not been characterized in the cynomolgus monkey. This important experimental animal species exhibits pronounced heart rate variability, complicating the temporal evaluation of QT interval data.

METHODS

Digitized epicardial ECGs and aortic blood pressures were collected for 20 h in telemetered cynomolgus monkeys (n=6) following the administration of either vehicle or moxifloxacin (10 or 50 mg/kg, p.o.). Moxifloxacin plasma concentrations were determined 4 h postdose. ECG intervals were analyzed by computerized algorithms. Individual probabilistic QT rate-corrections (QTc) were derived from the slopes of predose log-transformed QT-RR data where each QT value was the mean of >250 beats/RR increment. The resulting QTc was used to determine the repolarization effects of moxifloxacin, expressed as the placebo-adjusted change in QTc (DeltaQTc), and as the integrated response from 0 to 12 h (AUC(0-->12)) postdose.

RESULTS

No DeltaQTc effect was produced by 10 mg/kg moxifloxacin. However, moxifloxacin (50 mg/kg; 5.86+/-0.5 microg/mL C(max)) significantly prolonged the RR interval by 50 to 112 ms from 3.5 to 7.5 h postdose and DeltaQTc by >or=7.2 ms from 1.83 to 9.17 h, with a maximal DeltaQTc effect of +26.4 ms. No notable effects on either systemic blood pressure or body temperature occurred with either dose.

DISCUSSION

Probabilistic QT rate-corrections appear to have eliminated the confounding effects of heart rate, provided for a stable QTc baseline, and enabled the demonstration of an exposure-dependent QTc prolongation by moxifloxacin. The duration and magnitude of the QTc effect paralleled moxifloxacin pharmacokinetics, and C(max) values were similar to those achieved clinically in thorough QT/QTc studies. Thus, novel probabilistic QT rate-corrections may offer highly robust assessments of repolarization risk in both nonclinical and clinical investigations.