Methodological considerations in the design of trials for safety assessment of new drugs and chemical entities

Improved semi-parametric inference for a mixture model of responses from a control versus treatment group trial

The mixture of a distribution of responses from untreated patients and a shift of that distribution is a useful model for the responses from a group of treated patients. The mixture model accounts for the fact that not all the patients in the treated group will respond to the treatment and consequently their responses follow the same distribution as the responses from untreated patients. The treatment effect in this context consists of both the fraction of the treated patients that are responders and the magnitude of the shift in the distribution for the responders. In this article, we introduce inference based on a pseudo-likelihood approach and compare it with an existing method of moment approach. An extensive simulation study is used to compare robust performance of the two approaches regarding point estimation, confidence regions, and confidence intervals. The methods are demonstrated on an illustrative blood pressure data set.

An evaluation of a supratherapeutic dose of inclisiran on cardiac repolarization in healthy volunteers: A phase I, randomized study

Inclisiran is a small interfering RNA molecule that has been shown to provide an effective and sustained reduction in low-density lipoprotein cholesterol levels. This study aimed to determine whether a supratherapeutic dose of inclisiran affects cardiac repolarization and conduction in healthy volunteers. A phase I, randomized, double-blind, double-dummy, placebo- and positive-controlled, three-way crossover study was performed in 48 healthy volunteers. Volunteers were assigned to three treatments in a randomized sequence: a supratherapeutic dose of inclisiran sodium (900 mg), placebo, or moxifloxacin 400 mg as a positive control, with a minimum 7-day washout period between treatments. Continuous electrocardiogram monitoring was performed from >60 min before dosing until 48 h after dosing. Pharmacokinetics, pharmacodynamics, and safety were also assessed. Inclisiran, at a supratherapeutic dose, did not show a clinically significant effect on the QT interval (Fridericia correction formula [QTcF]; maximal placebo- and baseline-corrected change: 2.5 ms [90% confidence interval: 0.6, 4.5]) near the maximal plasma concentrations at 4 h. In addition, inclisiran did not show any effects on other electrocardiogram intervals or ST- and T-wave morphology. The positive control, moxifloxacin, demonstrated the expected changes in QTcF interval, validating the adequate sensitivity of the study. A supratherapeutic dose of inclisiran sodium (900 mg) had no effect on the QTcF interval or other electrocardiogram parameters, providing additional insight and reassurance regarding the safety profile of inclisiran.

Epistemic risk and nonepistemic values in end-of-life care

Some have questioned the extent of medical intervention at the end of people's lives, arguing that we often intervene in the dying process in ways which are harmful, inappropriate, or undignified. In this paper, I argue that over-treatment of dying is a function of the way in which clinicians manage epistemic risk-the risk of being wrong. When making any scientific decision-whether making inferences from empirical data, or determining a plan for medical treatment-there is always a degree of uncertainty: in other words, there is always a possibility we make the wrong decision. As philosophers of science such as Justin Biddle have argued, there is no way to resolve epistemic risk without weighing up the consequences of being wrong. This requires us to draw upon other, non-epistemic considerations, like social and ideological values; as such, questions of epistemic risk cannot be answered solely with reference to epistemic considerations such as evidence. In this paper, I explore how epistemic risk arises in end-of-life care, highlighting how clinicians face epistemic risk when diagnosing patients as dying and when determining whether a particular treatment is futile. I argue that there is no clear cut-off between reversible and irreversible illness, nor between useful and futile treatment. Clinicians who diagnose a patient as dying thus risk failing to provide treatment which could be beneficial; conversely, clinicians who determine that a patient has a potentially reversible illness risk subjecting them to futile treatment that may be painful or distressing. Having outlined where and how epistemic risk arises in end-of-life care, I turn my attention to the values and norms which shape clinicians' management of epistemic risk. I highlight how societal attitudes towards death, the medicalisation of dying, and the practice of defensive medicine all contribute to clinicians erring on one side of epistemic caution, minimising the risk that they miss or fail to treat illness. By applying the concept of epistemic risk to end-of-life care, I offer a novel lens through which to view medical decision-making in dying patients.

ECG-based heartbeat classification for arrhythmia detection: A survey

An electrocardiogram (ECG) measures the electric activity of the heart and has been widely used for detecting heart diseases due to its simplicity and non-invasive nature. By analyzing the electrical signal of each heartbeat, i.e., the combination of action impulse waveforms produced by different specialized cardiac tissues found in the heart, it is possible to detect some of its abnormalities. In the last decades, several works were developed to produce automatic ECG-based heartbeat classification methods. In this work, we survey the current state-of-the-art methods of ECG-based automated abnormalities heartbeat classification by presenting the ECG signal preprocessing, the heartbeat segmentation techniques, the feature description methods and the learning algorithms used. In addition, we describe some of the databases used for evaluation of methods indicated by a well-known standard developed by the Association for the Advancement of Medical Instrumentation (AAMI) and described in ANSI/AAMI EC57:1998/(R)2008 (ANSI/AAMI, 2008). Finally, we discuss limitations and drawbacks of the methods in the literature presenting concluding remarks and future challenges, and also we propose an evaluation process workflow to guide authors in future works.

The role of concentration-effect relationships in the assessment of QTc interval prolongation

Population pharmacokinetic and pharmacokinetic-pharmacodynamic (PKPD) modelling has been widely used in clinical research. Yet, its application in the evaluation of cardiovascular safety remains limited, particularly in the evaluation of pro-arrhythmic effects. Here we discuss the advantages of disadvantages of population PKPD modelling and simulation, a paradigm built around the knowledge of the concentration-effect relationship as the basis for decision making in drug development and its utility as a guide to drug safety. A wide-ranging review of the literature was performed on the experimental protocols currently used to characterize the potential for QT interval prolongation, both pre-clinically and clinically. Focus was given to the role of modelling and simulation for design optimization and subsequent analysis and interpretation of the data, discriminating drug from system specific properties. Cardiovascular safety remains one of the major sources of attrition in drug development with stringent regulatory requirements. However, despite the myriad of tests, data are not integrated systematically to ensure accurate translation of the observed drug effects in clinically relevant conditions. The thorough QT study addresses a critical regulatory question but does not necessarily reflect knowledge of the underlying pharmacology and has limitations in its ability to address fundamental clinical questions. It is also prone to issues of multiplicity. Population approaches offer a paradigm for the evaluation of drug safety built around the knowledge of the concentration-effect relationship. It enables quantitative assessment of the probability of QTc interval prolongation in patients, providing better guidance to regulatory labelling and understanding of benefit/risk in specific populations.

Not-in-trial simulation I: Bridging cardiovascular risk from clinical trials to real-life conditions

AIMS

The assessment of heart rate-corrected QT (QTc) interval prolongation relies on the evidence of drug effects in healthy subjects. This study demonstrates the relevance of pharmacokinetic-pharmacodynamic (PKPD) relationships to characterize drug-induced QTc interval prolongation and explore the discrepancies between clinical trials and real-life conditions.

METHODS

d,l-Sotalol data from healthy subjects and from the Rotterdam Study cohort were used to assess treatment response in a phase I setting and in a real-life conditions, respectively. Using modelling and simulation, drug effects at therapeutic doses were predicted in both populations.

RESULTS

Inclusion criteria were shown to restrict the representativeness of the trial population in comparison to real-life conditions. A significant part of the typical patient population was excluded from trials due to weight and baseline QTc interval criteria. Relative risk was significantly different between sotalol users with and without heart failure, hypertension, diabetes and myocardial infarction (P < 0.01). Although drug effects do cause an increase in the relative risk of QTc interval prolongation, the presence of diabetes represented an increase from 4.0 [95% confidence interval (CI) 2.7-5.8] to 6.5 (95% CI 1.6-27.1), whilst for myocardial infarction it increased from 3.4 (95% CI 2.3-5.13) to 15.5 (95% CI 4.9-49.3).

CONCLUSIONS

Our findings show that drug effects on QTc interval do not explain the observed QTc values in the population. The prevalence of high QTc values in the real-life population can be assigned to co-morbidities and concomitant medications. These findings substantiate the need to account for these factors when evaluating the cardiovascular risk of medicinal products.

Assessment of primary healthcare professionals' management of hypertensive patients with riser pattern

BACKGROUND

Ambulatory blood pressure monitoring (ABPM) was implemented in our primary care setting four years ago. Since then, 450 ABPMs have been performed and 69 riser subjects identified. The riser pattern is an independent risk factor for both incidence of cardiovascular events and their associated mortality.

OBJECTIVE

The purpose of this study was to assess the amount of control of essential hypertension (EH) among riser patients and to evaluate how our health professionals manage therapeutic changes in riser individuals.

MATERIALS AND METHODOLOGY

This retrospective study involved 34,289 inhabitants served in a centre in the Barcelona metropolitan area. EH individuals (450) were recruited and ABPM was performed following guidelines of the MAPAPRES (www.cardiorisc.com/MP/index_MP.asp).

RESULTS

Good control of blood pressure was observed in 46% of dipper and non-dipper subjects but only 35% of riser subjects had blood pressures within good control ranges. The measured cardiovascular risk was either high or very high in 35% of riser individuals. Changes in medication were introduced in riser patients with both good and poor blood pressure control. A second follow-up ABPM was done in only 27% of the riser individuals. In these subjects, therapeutic changes successfully modified ABPM patterns in 87% of cases.

CONCLUSIONS

Therapeutic changes in riser patients were introduced when these subjects were poorly controlled and these changes were highly effective. Additional ABPM to confirm the effectiveness of therapeutic changes was only performed in some individuals. Thus, for management of riser patients, more specific training of health professionals is needed.

Impact of periictal interventions on respiratory dysfunction, postictal EEG suppression, and postictal immobility

PURPOSE

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of epilepsy-related mortality. Seizure-related respiratory dysfunction (RD), the duration of postictal generalized electroencephalography (EEG) suppression (PGES), and duration of postictal immobility (PI) may be important in the pathophysiology of SUDEP. Periictal interventions may reduce the risk of SUDEP.

METHODS

We assessed the impact of periictal nursing interventions on RD, PGES, and PI duration in patients with localization-related epilepsy and secondarily generalized convulsions (GCs) recorded during video-EEG telemetry in the epilepsy monitoring unit. Video-EEG data were retrospectively reviewed. Interventions including administration of supplemental oxygen, oropharyngeal suction, and patient repositioning were evaluated. Interventions were performed based on nursing clinical judgment at the bedside and were not randomized. The two-sided Wilcoxon rank-sum test was used to compare GCs with and those without intervention. Robust simple linear regression was used to assess the association between timing of intervention and duration of hypoxemia (SaO(2) < 90%), PGES, and PI using data from only the first GC for each patient.

KEY FINDINGS

Data from 39 patients with 105 GCs were analyzed. PGES >2 s occurred following 31 GCs in 16 patients. There were 21 GCs with no intervention (NOINT) and 84 GC with interventions (INT). In the INT group, the duration of hypoxemia was shorter (p = 0.0014) when intervention occurred before hypoxemia onset (mean duration 53.1 s) than when intervention was delayed (mean duration 132.42 s). Linear regression indicated that in GCs with nursing interventions, earlier intervention was associated with shorter duration of hypoxemia (p < 0.0001) and shorter duration of PGES (p = 0.0012). Seizure duration (p < 0.0001) and convulsion duration (p = 0.0457) were shorter with earlier intervention. PI duration was longer for GCs with PGES than GCs without PGES (p < 0.0001). The mean delay to first active nonrespiratory movement following GCs with PGES was 251.96 s and for GC without PGES was 66.06 s. The duration of PI was positively associated with lower SaO(2) nadir (p = 0.003) and longer duration of oxygen desaturation (p = 0.0026). There was no association between PI duration and seizure duration (p = 0.773), between PI duration and PGES duration (p = 0.758), or between PI duration and the timing of first intervention relative to seizure onset (p = 0.823). PGES did not occur in the NOINT group. The mean duration of desaturation was longer (110.9 vs. 49.9 s) (p < 0.0001), mean SaO(2) nadir was lower (72.8% vs. 79.7%) (p = 0.0086), and mean end-tidal CO(2) was higher (58.6 vs. 50.3 mmHg) (p = 0.0359) in the INT group compared with the NOINT group. The duration of the seizure or of the convulsive component was not significantly different between the INT and NOINT groups.

SIGNIFICANCE

Early periictal nursing intervention was associated with reduced duration of RD and reduced duration of PGES. These findings suggest the possibility that such interventions may be effective in reducing the risk of SUDEP in the outpatient setting. Validation of these preliminary data with a prospective study is needed before definitive conclusions can be reached regarding the efficacy of periictal interventions in reducing the risk of SUDEP.

Assessing the probability of drug-induced QTc-interval prolongation during clinical drug development

Early in the course of clinical development of new non-antiarrhythmic drugs, it is important to assess the propensity of these drugs to prolong the QT/QTc-interval. The current regulatory guidelines suggest using the largest time-matched mean difference between drug and placebo (baseline-adjusted) groups over the sampling interval, thereby neglecting any potential exposure-effect relationship and nonlinearity in the underlying physiological fluctuation in QT values. Thus far, most of the attempted models for characterizing drug-induced QTc-interval prolongation have disregarded the possibility of model parameterization in terms of drug-specific and system-specific properties. Using a database consisting of three compounds with known dromotropic activity, we built a bayesian hierarchical pharmacodynamic (PD) model to describe QT interval, encompassing an individual correction factor for heart rate, an oscillatory component describing the circadian variation, and a truncated maximum-effect model to account for drug effect. The explicit description of the exposure-effect relationship, incorporating various sources of variability, offers advantages over the standard regulatory approach.

Seizure-related cardiac repolarization abnormalities are associated with ictal hypoxemia

PURPOSE

Cardiac arrhythmias and respiratory disturbances have been proposed as likely causes for sudden unexpected death in epilepsy. Oxygen desaturation occurs in one-third of patients with localization-related epilepsy (LRE) undergoing inpatient video-electroencephalography (EEG) telemetry (VET) as part of their presurgical workup. Ictal-related oxygen desaturation is accompanied by hypercapnia. Both abnormal lengthening and shortening of the corrected QT interval (QTc) on electrocardiography (ECG) have been reported with seizures. QTc abnormalities are associated with increased risk of sudden cardiac death. We hypothesized that there may be an association between ictal hypoxemia and cardiac repolarization abnormalities.

METHODS

VET data from patients with refractory LRE were analyzed. Consecutive patients having at least one seizure with accompanying oxygen desaturation below 90% and artifact-free ECG data were selected. ECG during the 1 min prior to seizure onset (PRE) and during the ictal/postictal period with accompanying oxygen desaturation below 90% (DESAT) was analyzed. Consecutive QT and RR intervals were measured. In the same patients, DESAT seizures were compared with seizures without accompanying oxygen desaturation below 90% (NODESAT). For NODESAT seizures, QT and RR intervals for 2 min after seizure onset were measured.

KEY FINDINGS

Thirty-seven DESAT seizures were analyzed in 17 patients with localization-related epilepsy. A total of 2,448 QT and RR intervals were analyzed during PRE. During DESAT, 1,554 QT and RR intervals were analyzed. Twelve of the 17 patients had at least one NODESAT seizure. A total of 19 NODESAT seizures were analyzed, including 1,558 QT and RR intervals during PRE and 3,408 QT and RR intervals during NODESAT. The odds ratio for an abnormally prolonged (>457 ms) QTcH (Hodges correction method) during DESAT relative to PRE was 10.64 (p < 0.0001). The odds ratio for an abnormally shortened (<372 ms) QTcH during DESAT relative to PRE was 1.65 (p < 0.0001). Seizure-related shortening and prolongation of QTc during DESAT were also observed when Fridericia correction of the QT was applied. During DESAT seizures, the mean range of QT values (QTr) (61.14 ms) was significantly different from that during PRE (44.43 ms) (p = 0.01). There was a significant association between DESAT QTr and oxygen saturation nadir (p = 0.025) and between DESAT QTr and duration of oxygen desaturation (p < 0.0001). Both QTcH prolongation and shortening also occurred with NODESAT seizures. A seizure-associated prolonged QTcH was more likely during DESAT than NODESAT, with an odds ratio of 4.30 (p < 0.0001). A seizure-associated shortened QTcH was more likely during DESAT than NODESAT with an odds ratio of 2.13 (p < 0.0001).

SIGNIFICANCE

We have shown that the likelihood of abnormal QTcH prolongation is increased 4.3-fold with seizures that are associated with oxygen desaturation when compared with seizures that are not accompanied with oxygen desaturation. The likelihood of abnormally shortened QTcH increases with seizures that are accompanied by oxygen desaturation with an odds ratio of 2.13 compared with that in seizures without desaturations. There is a significant association between the depth and duration of oxygen desaturation and QTr increase. These findings may be related to the pathophysiology of SUDEP.

A pilot study of QT interval analysis in overweight and obese youth

This descriptive pilot study examined if manual corrected QT (QTc) interval measures obtained from a standard 12-lead electrocardiogram (ECG) correlated with automated 24-hour ambulatory Holter QTc measures in 30 overweight and obese youth aged 12-17 years. In addition, we sought to determine if a significant difference existed between the means of manual 12-lead ECG versus automated 24-hour ambulatory Holter measures. Spearman's rho correlation coefficient revealed there was little if any correlation between manual 12-lead ECG and automated 24-hour ambulatory Holter QTc measures (r = .179, p = .345). In addition, a significant difference existed between QTc measures obtained from the manual 12-lead ECG in comparison to the automated 24-hour ambulatory Holter measures (p = .01). The manual 12-lead ECG and automated 24-hour ambulatory Holter analysis methods should not be used for comparison of QTc measures in overweight and obese youth.

Too long or too short? New insights into abnormal cardiac repolarization in people with chronic epilepsy and its potential role in sudden unexpected death

SUMMARY

Sudden unexpected death in epilepsy (SUDEP) is probably caused by periictal cardiorespiratory alterations such as central apnea, bradyarrhythmia, and neurogenic pulmonary edema. These alterations may occur in people with epilepsy and vary in duration and severity. Seizure-related ventricular tachyarrhythmias have also been hypothesized to be involved in SUDEP, but compelling evidence of these, or of predisposition to these, is lacking. Ventricular tachyarrhythmias are facilitated by pathologic cardiac repolarization. Electrocardiography (ECG) indicators of pathologic cardiac repolarization, such as prolongation or shortening of QT intervals as well as increased QT dispersion, are established risk factors for life-threatening tachyarrhythmia and sudden cardiac death (SDC). Abnormalities in cardiac repolarization have recently been described in people with epilepsy. Importantly, periictal ventricular tachycardia and fibrillation have also been reported in the absence of any underlying cardiac disease. Therefore, pathologic cardiac repolarization could promote SCD in people with epilepsy and could be one plausible cause for SUDEP. Herein, we review abnormal cardiac repolarization in people with epilepsy, describe the putative contribution of antiepileptic drugs, and discuss the potential role of pathologic cardiac repolarization in SUDEP. Based on these, measures to reduce the risk of or prevent SUDEP may include antiarrhythmic medication and implantation of cardiac combined pacemaker-defibrillator devices.

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.

Lengthening of corrected QT during epileptic seizures

PURPOSE

To measure the corrected QT cardiac repolarization time before and during epileptic seizures.

METHODS

Thirty-nine video-EEG/ECG/SAO(2) (electroencephalography/electrocardiography/oxygen saturation) telemetry patients were included in this prospective study. Epileptic seizures were identified both clinically and electrographically. RR intervals and associated QT intervals were measured 5 min prior to the onset of the identified seizure. Consecutive RR and associated QT intervals were then measured from the seizure onset until the seizure had ended and the EEG had resumed its preseizure trace. Averaged RR and QT intervals over nine consecutive beats were applied to Bazett's, Hodge's, Fridericia's, and Framingham's formulas to compare the corrected QT values before and during the seizures.

RESULTS

A total of 156 seizures had corrected QT analysis performed. Nine generalized tonic-clonic seizures (5 patients), 34 absences (6 patients), 12 tonic seizures (6 patients), 27 temporal lobe seizures (14 patients), 58 frontal lobe seizures (4 patients), and 16 subclinical seizures (4 patients). All formulae reported a statistically significant difference in corrected QT (p < 0.001) during total seizure data compared to total preseizure values. According to Bazett's formula, 21 seizures (nine patients) transiently increased their corrected QT beyond normal limits, with a maximum corrected QT of 512 ms during a right temporal lobe seizure.

CONCLUSION

Significant lengthening of corrected QT cardiac repolarization time occurred during some epileptic seizures in this study. Prolonged corrected QT may have a role in sudden unexplained death in epilepsy (SUDEP).

Recent Advances of Intervention to Inhibit Progression of Carotid Intima-Media Thickness in Patients With Type 2 Diabetes Mellitus

BACKGROUND AND PURPOSE

Type 2 diabetes is associated with a high cardiovascular morbidity and mortality. Recent advances of intervention studies in type 2 diabetes with use of carotid intima-media thickness (CIMT) measurement as a surrogate end point may allow for better understanding of the undetermined process of atherosclerosis, the effect of interventions, and the usefulness of CIMT to inhibit events of cardiovascular disease.

SUMMARY OF REVIEW

Data were available from 11 studies (n=1578) in subjects with type 2 diabetes (including impaired glucose tolerance, n=132) that evaluated the effect of interventions on change in CIMT. The overall weighed rate of change in mean CIMT based on data among control groups (ie, type 2 diabetes without interventions) was 0.034 mm/y (95% CI, 0.029 to 0.039; median SD, 0.054), in which mean HbA(1c) was 7.86% (95% CI, 7.72 to 8.00; median SD, 1.5). A significant close correlation of HbA(1c) with rate of CIMT change was found (R(2)=0.35, P=0.01). Agents for lowering of blood glucose, platelet activation, or blood pressure significantly reduced the CIMT increase, independent of blood glucose control. This implies that other mechanisms of such agents to diminish CIMT increase should be explored.

CONCLUSIONS

CIMT measurement may contribute to elucidating the short- and/or long-term effect of interventions on the rate of change in CIMT in relation to the levels of various risk factors. Although the method needs further standardization, pharmacological interventions are likely to inhibit progression of CIMT, leading to a reduction of cardiovascular events.