E14 and S7B Clinical and Nonclinical Evaluation of QT/QTc Interval Prolongation and Proarrhythmic Potential--Questions and Answers : Guidance for Industry

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E14 and S7B Clinical and Nonclinical
Evaluation of QT/QTc Interval
Prolongation and
Proarrhythmic Potential —
Questions and Answers
Guidance for Industry
U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
Center for Biologics Evaluation and Research (CBER)
August 2022
ICH

E14 and S7B Clinical and Nonclinical
Evaluation of QT/QTc Interval
Prolongation and
Proarrhythmic Potential —
Questions and Answers
Guidance for Industry
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U.S. Department of Health and Human Services
Food and Drug Administration
Center for Drug Evaluation and Research (CDER)
Center for Biologics Evaluation and Research (CBER)
August 2022
ICH

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FOREWORD
The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for
Human Use (ICH) has the mission of achieving greater regulatory harmonization worldwide to
ensure that safe, effective, and high-quality medicines are developed, registered, and maintained
in the most resource-efficient manner. By harmonizing the regulatory expectations in regions
around the world, ICH guidelines have substantially reduced duplicative clinical studies,
prevented unnecessary animal studies, standardized safety reporting and marketing application
submissions, and contributed to many other improvements in the quality of global drug
development and manufacturing and the products available to patients.
ICH is a consensus-driven process that involves technical experts from regulatory authorities and
industry parties in detailed technical and science-based harmonization work that results in the
development of ICH guidelines. The commitment to consistent adoption of these consensus-
based guidelines by regulators around the globe is critical to realizing the benefits of safe,
effective, and high-quality medicines for patients as well as for industry. As a Founding
Regulatory Member of ICH, the Food and Drug Administration (FDA) plays a major role in the
development of each of the ICH guidelines, which FDA then adopts and issues as guidance to
industry.

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TABLE OF CONTENTS
INTRODUCTION......................................................................................................................... 1
E14 QUESTIONS AND ANSWERS ........................................................................................... 2
I. 	ELECTROCARDIOGRAMS METHODOLOGY (1) .................................................. 2
II. 	SEX (2) ............................................................................................................................... 6
III. 	POSITIVE CONTROL (3)............................................................................................... 7
IV. 	STUDY DESIGN (4) ......................................................................................................... 8
V. 	USE OF CONCENTRATION RESPONSE MODELING OF QTC DATA (5) ......... 9
VI. 	SPECIAL CASES (6)...................................................................................................... 12
VII. 	ELECTROCARDIOGRAMS MONITORING IN LATE-STAGE CLINICAL
TRIALS (7) .................................................................................................................................. 14
S7B QUESTIONS AND ANSWERS......................................................................................... 16
I. 	INTEGRATED RISK ASSESSMENT (1).................................................................... 16
II. 	BEST PRACTICE CONSIDERATIONS FOR IN VITRO STUDIES (2) ................ 19
III. 	BEST PRACTICE CONSIDERATIONS FOR THE IN VIVO QT STUDIES (3) ... 24
IV. 	PRINCIPLES FOR PROARRHYTHMIA MODELS (4) ........................................... 26

Contains Nonbinding Recommendations
E14 and S7B Clinical Evaluation of QT/QTc Interval Prolongation
and Proarrhythmic Potential —
Questions and Answers
Guidance for Industry1
This guidance represents the current thinking of the Food and Drug Administration (FDA or Agency) on
this topic. It does not establish any rights for any person and is not binding on FDA or the public. You
can use an alternative approach if it satisfies the requirements of the applicable statutes and regulations.
To discuss an alternative approach, contact the FDA office responsible for this guidance as listed on the
title page.
INTRODUCTION
This question-and-answer (Q&A) document is intended to clarify key issues to facilitate
implementing the ICH guidances for industry E14 Clinical Evaluation of the QT/QTc Interval
Prolongation and Proarrhythmic Potential for Non-Antiarrhythmic Drugs (October 2005) and
S7B Nonclinical Evaluation of the Potential for Delayed Ventricular Repolarization (QT Interval
Prolongation) by Human Pharmaceuticals (October 2005).2 This guidance revises ICH E14
Q&As Q12 (5.1) and Q13 (6.1), and adds new ICH S7B Q&As Q17 (1.1) to Q30 (4.2). This
guidance finalizes the draft guidance issued in September 2020.
The contents of this document do not have the force and effect of law and are not meant to bind
the public in any way, unless specifically incorporated into a contract. This document is intended
only to provide clarity to the public regarding existing requirements under the law. FDA
guidance documents, including this guidance, should be viewed only as recommendations, unless
specific regulatory or statutory requirements are cited. The use of the word should in Agency
guidance means that something is suggested or recommended, but not required.
1 This guidance was developed within the Expert Working Groups (Efficacy and Safety) of the International Council
for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) (formerly the International
Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH)
and has been subject to consultation by the regulatory parties, in accordance with the ICH process. This document
has been endorsed by the ICH Assembly at Step 4 of the ICH process, February 2022. At Step 4 of the process, the
final draft is recommended for adoption to the regulatory bodies of the ICH regions.
2 We update guidances periodically. For the most recent version of a guidance, check the FDA guidance web page
at https://www.fda.gov/regulatory-information/search-fda-guidance-documents.
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E14 QUESTIONS AND ANSWERS
I. 	ELECTROCARDIOGRAMS METHODOLOGY (1)3
Q1. 	Please discuss who should read electrocardiograms (ECGs), including information
on the number and training of readers and the need for readers to be blinded. (1.1)
The document recommends that the reader should be skilled, but it does not identify specific
training that is needed. A technician reading with a cardiologist over-reading the document
would certainly be consistent with the guidance. The attempt of the guidance to limit the number
of readers represents an attempt to increase consistency. The guidance asks for assessment of
intra- and inter-reader variability and suggests “a few skilled readers” (not necessarily a single
reader) to analyze a whole thorough QT study, since many readers may increase variability.
Training would be another way to improve consistency.
It is recommended for the thorough QT Study that core ECG laboratories blind subject, time, and
treatment in order to reduce potential bias. The T wave analysis, which calls for all 12 leads, can
be performed after the QT analyses, and requires comparison to the baseline ECG; it can,
however, be blinded as to treatment.
Q2. 	What is the position of ICH regarding the role of the following reading methods in
the thorough QT/QTc study and other clinical trials? (1.2)
 	Fully manual
 	Fully automated
 	Manual adjudication (manual over-read, computer-assisted, semi-automated)?
The techniques currently in use for the measurement of ECG intervals can be classified into three
broad categories: (1) fully manual, (2) fully automated, and (3) manual adjudication. Within
each of these general categories, many different methodologies are subsumed that differ in terms
of lead selection, the conventions used for defining T wave offset, and the criteria for the
inclusion and exclusion of U waves.
ECG readings can be performed on the following waveform presentations:
 	Raw waveforms: ECG waveforms recorded from a single lead
 	Representative waveforms (median beats, reference cycles): Compositional waveforms
constructed by a computer-based averaging process that involves aligning and combining
data from all dominant, normally conducted raw ECG waveforms from a single lead
 	Global waveforms: Composite representation of cardiac electrical activity constructed by
superimposing representative waveforms from all or several simultaneously recorded
3 The numbers in parentheses reflect the organizational breakdown of the document endorsed by the ICH Assembly
at Step 4 of the ICH process, February 2022.
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leads to form a spatial-vector complex, by weighted averaging of individual
representative complexes with low noise and long duration, or by other methods
Fully manual
When using a fully manual reading technique, a human reader is responsible for examining the
ECG waveform and placing the fiducial points to mark the beginning and the end of the
intervals, without the assistance of a computer algorithm. Fully manual methods of fiducial
point placement can be applied to raw, representative, and global waveforms. When fully
manual measurements are made from the raw ECG waveforms in a single lead, three or more
cycles should be averaged, where available, to produce the final determination of interval
duration. An advantage of this approach is that the reader will not be influenced by prior
computer placement of the fiducial points, but a weakness can be inter- and intra-reader
variability, especially when measurements are performed over an extended time period (e.g.,
several months). Laboratories using manual reading techniques should observe standard
operating procedures based on prospectively defined criteria for determining where the fiducial
points should be placed. All readers in the laboratory should be trained in the consistent
application of these criteria.
Fully automated
Fully automated reading methods rely entirely upon a computer algorithm for the placement of
the fiducial points and the measurement of the ECG intervals. Automated ECG interval
measurements can be performed on raw, representative, or global ECG waveforms. Most digital
electrocardiographs are equipped with algorithms that perform measurements on global
waveforms. Although automated methods have the advantage of being consistent and
reproducible, they can yield misleading results in the presence of noise or when dealing with
abnormal ECG rhythms, low amplitude P or T waves, or overlapping U waves. The techniques
used for construction and measurement of representative waveforms and global waveforms vary
between different computerized algorithms and between different software versions within
individual equipment manufacturers. As a result, between-algorithm and within-manufacturer
variability of fully automated measurements can confound serial comparisons when the
equipment or algorithm is not constant.
Manual adjudication (manual over-read/computer-assisted/semi-automated)
The manual adjudication approach refers to reading methods in which a computer algorithm is
responsible for the initial placement of the fiducial points on the ECG waveform. A human
reader subsequently reviews the algorithmic placement of the fiducial points, performing
adjustments wherever the computerized measurements are considered to be inaccurate. This
approach can have the advantage of greater consistency and reproducibility than fully manual
readings, while providing an opportunity to correct any mistakes made by the algorithmic
readings. Laboratories using manual adjudication techniques should observe standard operating
procedures based on prospectively defined criteria for determining when fiducial points should
be corrected. All readers in the laboratory should be trained in the consistent application of these
criteria. The adjudication procedure should normally be performed on all waveforms being used
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for interval determination. If an alternative approach is used, such as adjudication limited to
outlier intervals above and below a reference range, this methodology should be validated as
described in E14 Q&A Q3 (1.3).
The ICH E14 guidance currently recommends either fully manual or manual adjudication
approaches for clinical trials in which the assessment of ECG safety is an important objective,
such as the thorough QT/QTc study. When the thorough QT study is positive, fully manual or
manual adjudication methods are currently recommended for an adequate sample of patients in
late phase studies (see section II.C (2.3) in the E14 guidance). When the thorough QT/QTc
study is negative, routine ECG safety assessments in late phase clinical trials using fully
automated reading methods will be adequate.
Q3. 	The ICH E14 guidance contains the following statement: “If well-characterized
data validating the use of fully automated technologies become available, the
recommendations in the guidance for the measurement of ECG intervals could be
modified.” What would be expected of a sponsor that wished to validate and apply
an automated reading method for regulatory submissions? (1.3)
Efforts to develop more sophisticated and reliable methods for automated ECG readings for both
QT interval and T wave morphology assessment are encouraged. There are at present no large-
scale studies to validate the use of fully automated reading methods in patients; however, there
are examples of thorough QT/QTc studies in healthy volunteers in which automated methods
have been used and validated for QT interval measurements against manual methods.
QT Interval measurement
There are at present no clear and widely accepted criteria for validation of new semi-automated
or automated methods, but it is expected that each would be validated independently for its
ability to detect the QT/QTc prolongation effects of drugs that are near the threshold of
regulatory concern. Data supporting the validation of a new method should be submitted and
could include descriptive statistics, Bland-Altman plots of agreement, superimposed plots of the
baseline- and placebo-adjusted QTc and the RR as a function of time, together with data from
any trials that have employed the method.
T wave morphology assessment
The suitability of automated ECG reading techniques for the assessment of morphological
abnormalities has not yet been demonstrated. If a sponsor intends to develop a fully automated
approach, without visual assessment for morphological changes, validation studies should
include a demonstration that the automated method is capable of reading and interpreting a test
set of abnormal ECGs correctly (e.g., abnormalities of T wave morphology, overlapping U
waves). As with methods for QT interval determination, there are at present no clear and widely
accepted criteria for validation of novel methods.
Because changes in morphology can affect interval measurement, fully manual or manual
adjudication (as defined in Question Q2 (1.2)) techniques should be performed if treatment-
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emergent changes in morphology are observed. If, on the other hand, no morphology changes
are observed, this would support the use of automated methodologies, provided they have been
validated.
Q4. 	How does a sponsor incorporate new technology or validate new methodology into
the measurement and/or analysis of the QT interval? (1.4)
The ICH process is better suited to the determination of regulatory policy once the science in a
particular area has become more or less clear. In general, it is not well-suited to the qualification
or validation of new technology.
Sections II.E.1 (2.5.1) and II.E.2 (2.5.2) of the ICH E14 guidance are rather discouraging about
methodology outside conventional carts and human-determined measurements. Since the ICH
E14 guidance was issued, 12-lead continuous recording devices have largely supplanted cart
recorders in thorough QT studies without a formal validation process because of their
performance in the context of a positive control. The impact of other innovative technologies
can be assessed in studies incorporating a positive control. Although some technologies could be
assessed using other techniques in the absence of a positive control, this topic is more complex
and beyond the scope of this question and answer.
Twelve-lead continuous recording devices and other new technologies can be used in late phase
clinical trials. Even though a positive control is not used in late-stage studies, the new
technology could be validated in other studies (such as the thorough QT study). In cases where a
thorough QT study is not done, a sponsor can provide alternative methods for validating the
technology.
Q5. 	The ICH E14 guidance states that QT interval corrected by Fridericia’s and
Bazett’s correction should be submitted in all applications; is this still necessary? Is
there a recommended approach to QT correction that is different from that
specified in the ICH E14 guidance? (1.5)
Changes in heart rate could variably influence a drug’s effect on repolarization (i.e., QT
interval), and correction methods with different characteristics are often applied. The principles
set below would be applicable in all clinical studies (thorough QT or other studies).
In adults, Bazett’s correction has been clearly shown to be an inferior method of correcting for
differences in heart rate among and within subjects. Therefore, QT interval data corrected using
Bazett’s corrections is no longer warranted in all applications unless there is a compelling reason
for a comparison to historical Bazett’s corrected QT data. Presentation of data with a
Fridericia’s correction is likely to be appropriate in most situations, but other methods could be
more appropriate. There is no single recommended alternative (see E14 Q&A Q4 (1.4) on
Incorporating New Technologies), but the following are some considerations:
1. 	Analyses of the same data using different models for correcting QT can generate
discordant results. Therefore, it is important that the method(s) of correction, criteria for
the selection of the method of correction, and rationale for the components of the method
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of correction be specified prior to analysis to limit bias. Model selection should be based
on objective criteria and should consider the uncertainty in parameter estimates.
Alternative methods of correction should be used only if the primary method fails the
prespecified criteria for selection of the method of correction.
2. 	Corrections that are individualized to a subject’s unique heart rate QT dynamic are not
likely to work well when the data are sparse or when the baseline data upon which the
correction is based do not cover at least the heart rate range observed in patients on the
study drug.
II. 	SEX (2)
Q6. 	There are recognized differences in the baseline QTc between men and women.
These were noted in early versions of the guidance. In the E14 guidance, however, it
is recommended that outliers be categorized as > 450, > 480, and > 500 milliseconds
(ms), regardless of sex. Can you say why there is no sex difference in the
recommendation? (2.1)
The 450, 480, and 500 ms categories refer to the values the E14 guidance suggests sponsors
might use in characterizing outliers. The numbers that were specified previously for males and
females referred to “normal” QTc values, which may differ for men and women. This section
was not included in the final guidance, however, and such considerations would be largely
irrelevant to larger durations (e.g., 480 and 500 ms). As the thorough QT/QTc study is designed
to examine the propensity of a drug to prolong the QTc interval, it is appropriate to perform the
study in healthy male or female volunteers.
Q7. 	Should we enroll both sexes in a thorough QT study, and does the study need to be
powered for independent conclusions about each sex? (2.2)
Post-pubertal males have lower heart-rate corrected QT intervals than do pre-pubertal males or
females generally. Women are generally smaller than men, so their exposure to a given fixed
dose of a drug will generally be higher, and if a drug prolongs QT, it can be expected to prolong
it more in women because of the higher exposure. It is not settled whether and how often there
are sex differences in response to QT-prolonging drugs that are not explained by exposure alone.
The thorough QT study is primarily intended to act as a clinical pharmacology study in a healthy
population using a conservative primary objective defining the drug’s effect on QT. It is
unlikely that any of a variety of baseline demographic parameters would introduce a large
difference in QT response to a drug in subpopulations defined by factors such as age, co-
morbidity, and sex that is not explained by exposure.
It is encouraged, but not mandatory, to include both men and women in the thorough QT study.
Analyses of Concentration-Response Relationship by sex can be helpful for studying the effect
of the drug on QT/QTc interval in cases where there is evidence or mechanistic theory for a sex
difference. However, the primary analysis of a thorough QT study should be powered and
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conducted on the pooled population. If the primary analysis is negative and if there is no other
evidence suggesting sex differences, subgroup analysis by sex is not expected.
III. 	POSITIVE CONTROL (3)
Q8. 	The ICH E14 guidance emphasizes the importance of assay sensitivity and
recommends the use of a positive control. In order to accept a negative thorough
QT/QTc study, assay sensitivity should be established in the study by use of a
positive control with a known QT-prolonging effect. Please clarify how to assess the
adequacy of the positive control in the thorough QT study. (3.1)
The positive control in a study is used to test the study’s ability (its assay sensitivity) to detect the
study endpoint of interest, in this case QT prolongation by about 5 ms. If the study is able to
detect such QT prolongation by the control, then a finding of no QT effect of that size for the test
drug will constitute evidence that the test drug does not, in fact, prolong the QT interval by the
amount of regulatory concern. There are two conditions required for ensuring such assay
sensitivity:
1. 	The positive control should show a significant increase in QTc, i.e., the lower bound of
the one-sided 95% confidence interval (CI) must be above 0 ms. This shows that the trial
is capable of detecting an increase in QTc, a conclusion that is essential to concluding
that a negative finding for the test drug is meaningful.
2. 	The study should be able to detect an effect of about 5 ms (the QTc threshold of
regulatory concern) if it is present. Therefore, the size of the effect of the positive control
is of particular relevance. With this aim, there are at least two approaches:
a. 	To use a positive control showing an effect of greater than 5 ms (i.e., lower bound
of a one-sided 95% CI > 5 ms). This approach has proven to be useful in many
regulatory cases. However, if the positive control has too large an effect, the
study’s ability to detect a 5 ms QTc prolongation might be questioned. In this
situation, the effect of the positive control could be examined at times other than
the peak effect to determine whether an effect close to the threshold of regulatory
concern can be detected.
b. 	To use a positive control with an effect close to 5 ms (point estimate of the
maximum mean difference with placebo close to 5 ms, with a one-sided 95% CI
lower bound > 0). In using positive controls with smaller effects, it would be very
important to have a reasonably precise estimate of the drug’s usual effect.
Importantly, whatever approach is used, the effect of the positive control (magnitude of peak and
time course) should be reasonably similar to its usual effect. Data suggesting an underestimation
of QTc might question the assay sensitivity, thus jeopardizing the interpretability of the thorough
QT study results.
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Q9. 	Please clarify the need for blinding the positive control in the thorough QT study.
(3.2)
The use of a double-blinded positive control does not appear to be essential, provided that the
reading of ECGs is performed in a blinded manner as described in E14 Q&A Q2 (1.2), and the
study is carefully designed to ensure that specified study procedures are followed uniformly.
This means that the same protocol for administering the test drug and placebo, taking blood
samples, and collecting the ECG data should also be used when giving the positive control. This
does not mean that other aspects of the study, such as the duration of treatment with the positive
control and the other treatment groups, would be identical. If blinding of the positive control is
performed, common methods include the use of double-dummy techniques and over-
encapsulation.
IV. 	STUDY DESIGN (4)
Q10. 	In the ICH E14 guidance, the recommended metric to analyze for a crossover study
is the largest time-matched mean difference between the drug and placebo
(baseline-adjusted) over the collection period. Please discuss the most appropriate
metric to assess a drug’s effect on QT/QTc interval when the data are collected in a
placebo-controlled parallel design study (i.e., when there is no corresponding
placebo value for each patient). (4.1)
Regardless of the study design, “the largest time-matched mean difference between drug and
placebo (baseline-adjusted)” is determined as follows: The mean QTc for the drug (i.e.,
averaged across the study population) is compared to the mean QTc for placebo (averaged across
the study population) at each time point. The “largest time-matched mean difference between
drug and placebo” is the largest of these differences at any time point.
The term “baseline-adjusted” in the ICH E14 guidance implies that the baseline data are taken
into account in the statistical analysis.
Differences in baseline assessment between crossover and parallel design studies are discussed in
E14 Q&A Q11 (4.2).
Q11. 	Please discuss the need for baseline measurements, and when needed, how they
should be collected, for crossover and parallel design thorough QT studies. (4.2)
Adjustment for baseline measurements is potentially useful for several purposes, including
detection of carry-over effects, reducing the influence of inter-subject differences, and
accounting for diurnal effects such as those due to food. There is no single best approach for
baseline adjustment, but all planned baseline computations should be prospectively defined in
the clinical trial protocol. Two kinds of baseline are commonly used: time-matched baseline
(taken at exactly the same time-points on the day prior to the beginning of treatment as on the
treatment day) and predose baseline (taken shortly prior to dosing). The predose baseline is used
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for adjustment for inter-subject differences but not for diurnal effects. The choice of baseline is
influenced by whether the study is parallel or crossover.
For a parallel-group study, a time-matched baseline allows the detection of differences in diurnal
patterns between subjects that would not be detected by a predose baseline. In a parallel study, a
time-matched baseline day, if performed, would ideally occur on the day before the start of the
study.
In contrast, in a crossover study, a time-matched baseline is usually not necessary because
adjustments for subject- and study-specific diurnal variation are implicit by design in the
assessment of time-matched drug-placebo differences in QT/QTc effect. The predose baseline,
therefore, is usually adequate for crossover studies.
Obtaining replicate ECG measurements (for example, the average of the parameters from about 3
ECGs) within several minutes of each nominal time point at baseline and at subsequent times
will increase the precision of the estimated changes in QT/QTc effect.
V. 	USE OF CONCENTRATION RESPONSE MODELING OF QTC DATA (5)
Q12. 	The ICH E14 guidance states (in section III (3), page 12) that analysis of the
relationship between drug concentration and QT/QTc interval changes is under
active investigation. Has this investigation yielded a reasonable approach to
concentration-response modeling during drug development? How can assessment
of the concentration-response relationship guide the interpretation of QTc data?
(5.1)
Concentration-response analysis, in which all available data across all doses are used to
characterize the potential for a drug to influence QTc, can serve as an alternative to the by-time-
point analysis or intersection-union test as the primary basis for decisions to classify the risk of a
drug. In either case, this result is an important component of the totality of evidence assessment
of the risk of QT prolongation. The overall assessment of risk of QT prolongation includes
nonclinical data, the time course of QT prolongation, the magnitude of QT prolongation,
categorical analyses of outliers, and certain adverse events in patients that can signal potential
proarrhythmic effects.
There are many different types of models for the analysis of concentration-response data,
including descriptive pharmacodynamic (PD) models (e.g., linear or Emax models), or empirical
models that link pharmacokinetic (PK) models (dose-concentration-response) with PD models. It
is recognized that concentration-response analyses of the same data using models with different
underlying assumptions can generate discordant results. Therefore, it is important that the
modeling methods and assumptions, criteria for model selection, rationale for model
components, and potential for pooling of data across studies be specified prior to analysis to limit
bias. Prospective specification of model characteristics (e.g., structural model, objective criteria,
goodness of fit) based on knowledge of the pharmacology is recommended whenever possible.
On occasion, the QT effect is not a direct function of plasma concentration. For example, drugs
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that cause QT prolongation as a result of changes in protein synthesis or trafficking or drugs with
accumulation into myocardial tissues might demonstrate hysteresis. Testing for model
assumptions, hysteresis (a plot of data by-time point and a hysteresis loop plot), and goodness of
fit should be documented.
Concentration-response analysis can be challenging when more than one molecular entity—
multiple drugs or parent plus metabolites—contributes to the QTc effect.
Dose and exposure definitions
 	Therapeutic dose: dose evaluated in phase 3 trial or recommended in
product labeling
 	Clinical exposure: mean steady-state maximum concentration (Cmax,ss ) associated
with the maximum therapeutic dose
 	High clinical exposure: exposure (Cmax ,ss ) achieved when the maximum therapeutic
dose is administered in the presence of the intrinsic or extrinsic factor (e.g., organ
impairment, drug-drug interaction, food effect) that has the largest effect on
increasing Cmax ,ss
 	Supratherapeutic dose: dose that provides exposures (mean Cmax ) exceeding the high
clinical scenario
Important considerations
Concentration-response data would not necessarily come from a dedicated QT study, nor would
it necessarily come from a single study. However, there are several new and important
considerations that are described below.
1. 	Data can be acquired from first-in human studies, multiple-ascending dose studies, or
other studies, provided that the concentrations that can be safely achieved are well above
the exposure at the maximum therapeutic dose at steady-state and reflect high clinical
exposure scenario situations such as drug-drug and drug-food interactions, organ
dysfunction, and/or genetically impaired metabolism. Whenever possible, sponsors are
encouraged to explore a wide dose range in early-phase studies to enable characterization
of effects at high concentrations.
2. 	Efficient concentration-response analysis using data acquired in studies with other
purposes should have as much quality control as is needed for a dedicated study. This
includes robust, high-quality ECG recording and analysis sufficient to support a valid
assay for ECG intervals (see the E14 guidance and E14 Q&A Q1 (1.1)).
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3. 	If there is an intention to pool ECG interval data from multiple studies, it is important to
test for heterogeneity. Pooling of studies that were not planned for this purpose can
produce bias. This potential should be critically discussed in the analysis plan.
4. 	A separate positive control would not be necessary if either of the following conditions is
met:
a. 	There are data characterizing the response at a sufficient multiple (commonly 2x)
of the high clinical exposure (see ICH E14 guidance, section II.B.2 (2.2.2)).
b. 	If the high clinical exposure has been achieved in the clinical ECG assessment but
a sufficient multiple has not been obtained (e.g., for reasons of safety or
tolerability, saturating absorption), then a nonclinical integrated risk assessment
can be used as supplementary evidence. The reason higher doses were not tested
should be adequately justified. See ICH S7B Q&A Q17 (1.1) for details; in
summary, the nonclinical studies should include: (1) a hERG assay, following
best practice considerations (see ICH S7B Q&As, section II (2)), that shows low
risk as defined in ICH S7B Q&As Q17 (1.1) and Q18 (1.2) and (2) no evidence of
QTc prolongation in an in vivo assay conducted according to ICH S7B at
exposures that cover high clinical exposures (see ICH S7B Q&As, Q17 (1.1) and
section III (3); note that some recommendations only apply to decision-making
under ICH E14 Q&A Q13 (6.1)).
Decision-making
Both the intersection-union test and the concentration-response analysis can estimate the
maximum effect of a drug treatment on the QTc interval, but they are not used to test the same
hypothesis. As mentioned above, inspection of the time course of QT prolongation is important.
However, hypothesis testing based on a by-time point analysis (intersection-union test or point
estimate and confidence intervals) is inappropriate in studies designed for a concentration-
response analysis, if not powered to assess the magnitude of QT prolongation for each time
point.
When using a concentration-response analysis as the primary basis for decisions to classify the
risk of a drug, the upper bound of the two-sided 90% confidence interval for the QTc effect of a
drug treatment as estimated by exposure-response analysis should be < 10 ms at the highest
clinically relevant exposure to conclude that an expanded ECG safety evaluation during later
stages of drug development is not needed (see the E14 guidance, section II.B.4 (2.2.4), and E14
Q&A Q16 (7.1)).
Other uses
In addition to serving as the basis for regulatory decision-making, concentration-response
analysis has established its utility in several settings enumerated below.
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Providing insight into regimens not studied directly
An understanding of the concentration-response relationship can help predict the QT effects of
doses, dosing regimens, routes of administration, or formulations that were not studied directly.
Interpolation within the range of concentrations studied is more reliable than extrapolation above
the range.
Predicting QTc effects of intrinsic and extrinsic factors that affect pharmacokinetics
Understanding the concentration-response relationship can help predict the effects of intrinsic
(e.g., cytochrome P450 isoenzyme status) or extrinsic (e.g., drug-drug PK interactions) factors,
possibly affecting inclusion criteria or dosing adjustments in later-phase studies.
VI. 	SPECIAL CASES (6)
Q13. 	The ICH E14 guidance states that in certain cases, a conventional thorough QT
study might not be feasible. In such cases, what other methods should be used for
evaluation of QT/QTc and proarrhythmic potential? (6.1)
An integrated nonclinical and clinical QT/QTc risk assessment can be particularly valuable when
a thorough QT study or concentration-QTc analysis meeting similar quality control as needed for
a dedicated study as described in E14 Q&A Q12 (5.1) is not feasible. This situation can arise
under scenarios where a placebo-controlled comparison is not possible; safety considerations
preclude administering supratherapeutic doses to obtain high clinical exposures and/or safety or
tolerability prohibit the use of the product in healthy participants. The design elements that
include placebo and healthy participant dosing assist in decreasing variability, but their absence
does not preclude interpretation.
The integrated nonclinical and clinical QT/QTc risk assessment should include:
1. 	The hERG assay, an in vivo QT assay, and any follow-up nonclinical studies, especially
those selected to overcome the challenges encountered in the clinical studies (see ICH
S7B Q&As Q17 (1.1) and Q18 (1.2)
2. 	Alternative QT clinical study designs incorporating ECG assessments with as many of
the usual “thorough QT/QTc” design features as possible (see ICH E14 guidance, section
II.B (2.2), and E14 Q&A Q12 (5.1))
In situations where it is not possible to evaluate the QT/QTc effects at high clinical exposure, it
is particularly important that the nonclinical in vivo studies are conducted at exposures covering
the high clinical exposure (see ICH E14 Q&A Q12 (5.1) for definition of high clinical exposure).
An integrated QT/QTc risk assessment can also be particularly valuable for drugs with
confounding heart rate effects that could impact accurate determination of the QTc. Advanced
methodologies for controlling (e.g., pacing) or correcting for heart rate changes in the nonclinical
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in vivo studies and/or conducting QTc assessments in the intended patient population might be
informative in this situation. If tolerance to the chronotropic effect develops with repeat dosing,
upward titration regimens can sometimes be employed to avoid or minimize the confounding
effects of drug-induced heart rate changes on the QTc assessment.
Decision-Making
A totality of evidence argument based on the results of an integrated nonclinical and clinical
QT/QTc assessment could be made at the time of marketing application.
A drug that meets the following criteria would be considered to have a low likelihood of
proarrhythmic effects due to delayed repolarization:
1. 	The nonclinical studies, following best practice considerations for in vitro studies (see
ICH S7B Q&As, section II (2)) and in vivo studies (see ICH S7B Q&As, section III (3)),
show low risk as defined in ICH S7B Q&A Q17 (1.1).
2. 	The high-quality ECG data (see ICH E14 guidance and E14 Q&As, section I (1))
collected in the alternative QT clinical assessment do not suggest QT prolongation,
generally defined under this Q&A as an upper bound of the two-sided 90% confidence
interval around the estimated maximal effect on QTc less than 10 ms, as computed by the
concentration-response analysis or the intersection-union test. If applicable, there should
be no notable imbalances between treatment/dose arms in the proportion of subjects
exceeding outlier thresholds.
3. 	A cardiovascular safety database that does not suggest increased rate of adverse events
that signal potential for proarrhythmic effects (ICH E14 guidance, section IV (4)).
When justified, a totality of evidence argument for a drug to have a low likelihood of
proarrhythmic effects due to delayed repolarization could still be made for a drug that has an
upper bound of the two-sided 90% confidence interval around the estimated maximal effect on
QTc of 10 ms or more. The determination will depend on the quality and details of the clinical
data (e.g., estimated QTc mean and upper bound values, slope of any concentration-QTc
relationship) and nonclinical data (e.g., difference between the hERG safety margin for the
investigational drug and the threshold for defining low risk).
If nonclinical studies do not show low risk (or are not performed), there is reluctance to conclude
a lack of an effect in an absence of a positive control; however, if the upper bound of the two-
sided 90% confidence interval around the estimated maximal effect on QTc is less than 10 ms,
the treatment is unlikely to have an actual mean effect as large as 20 ms.
Q14. 	The ICH E14 guidance does not address the approach to QT measurement during
drug development in the case of combination drug products. Is it recommended
that measurement of QT prolongation be performed on drug combinations? (6.2)
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In general, combinations of two or more drugs are unlikely to need a thorough QT/QTc study or
intensive late-stage monitoring, if the component drugs have been demonstrated to lack relevant
effects in thorough QT/QTc studies as described in the ICH E14 guidance.
If one or more of the component drugs have not been individually characterized for effects on the
QT/QTc interval, they may be evaluated in combination or independently.
Q15. 	Are sponsors expected to conduct thorough QT studies as part of the development
of large proteins and monoclonal antibodies? (6.3)
Large, targeted proteins and monoclonal antibodies have a low likelihood of direct ion channel
interactions and a thorough QT/QTc study is not necessary, unless the potential for
proarrhythmic risk is suggested by mechanistic considerations or data from clinical or
nonclinical studies.
VII. 	ELECTROCARDIOGRAMS MONITORING IN LATE-STAGE CLINICAL
TRIALS (7)
Q16. 	The ICH E14 guidance describes in section II.C (2.3) (Clinical Trial Evaluation
After the “Thorough QT/QTc Study”) that “adequate ECG assessment to
accomplish this [monitoring] is not fully established.” Is there now a reasonable
approach to evaluating QTc in late-stage clinical development in the case of a
finding of QT prolongation prior to late phase studies? (7.1)
Clarification of approach to evaluating QTc in late-stage clinical development
The purpose of a thorough QT study is to characterize the effect of the drug on ventricular
repolarization (QT interval). It is not the purpose of the thorough QT study to assess the risk of
torsade de pointes (TdP) in the target population, but rather to determine whether further data are
warranted to assess risk. A finding of QT prolongation above the regulatory threshold of interest
(a positive thorough QT study) might call for further electrocardiographic follow-up in late phase
studies. The extent of the follow-up would be affected by the magnitude of the estimated
prolongation at doses and concentrations at which this occurs. If prolongation is substantial at
concentrations expected to occur in clinical studies, it is important to protect patients in later
trials and to obtain further information on the frequency of marked QT prolongation. In some
cases in which there is a large margin of safety between therapeutic exposures and the exposures
that result in significant ECG interval changes, an intensive ECG follow-up strategy might not be
warranted.
The recommended intensity of the monitoring and assessment in late-stage trials will depend on:
A. The magnitude of QTc prolongation seen in the thorough QT study or early clinical
studies
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B. The circumstances in which substantial QT prolongation might occur (i.e., in ordinary
use or only when drug concentrations are markedly increased (e.g., by renal or
hepatic impairment, concomitant medications))
C. PK properties of the drug (e.g., high inter-individual variability in plasma
concentrations, metabolites)
D. Characteristics of the target patient population that would increase the proarrhythmic
risk (e.g., structural heart disease)
E. 	The presence of adverse effects that can increase proarrhythmic risk (e.g.,
hypokalemia, bradycardia, heart block)
F. 	Other characteristics of the drug (e.g., pharmacodynamics, safety pharmacology,
toxicology, drug class, hysteresis)
The following examples delineate the scope of recommended ECG investigations based on
outcome of the thorough QT study or early clinical studies. These could be modified by other
factors such as A through F above.
Examples of ECG monitoring in late stage:
1. 	The thorough QT study results in a negative finding, as defined by the E14 criteria,4 at
the therapeutic dose, but the supratherapeutic dose (relative to phase 3 dose) shows mean
QTc effects between 10 and 20 ms. If there is reasonable assurance that the higher dose
represents drug exposures that are unlikely to be seen in the patient population, only
routine ECG monitoring is recommended in late phase trials. This approach provides
reassurance for safety because patients are unlikely to experience a clinically significant
QTc effect.
2. 	The thorough QT study results in a positive finding, as defined by the E14 criteria,5 at the
therapeutic dose, with a mean prolongation < 20 ms. For drugs with this magnitude of
effect on the QTc interval, intensive monitoring of phase 3 patients is called for.
Intensive ECG monitoring in clinical trials has two main objectives. One objective is to
provide protection to patients who might have large, worrisome QT intervals > 500 ms.
A second objective is identifying the frequency of marked QT increases (e.g., prolonged
QT > 500 ms or increases in QTc > 60 ms).
Given the limitations of collecting ECGs in late-stage trials, the focus of the analysis is
on outliers, not on central tendency. Other than descriptive statistics, detailed statistical
analysis is not expected. This monitoring is intended to be performed locally, without the
involvement of a central core laboratory.
4 A negative study, as defined by the ICH E14 guidance criteria, is an upper one-sided 95% CI of QTc prolongation
effect < 10 ms.
5 Ibid.
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The timing of ECG collection should be based on the known properties of the drug. All
patients should receive baseline, steady-state, and periodic ECGs during the trial. In
addition, ECGs should be collected around Tmax at the first dose and/or around steady
state in a subgroup of patients or in dedicated studies. ECG collection at around Tmax is
not important for drugs with low fluctuations between peak and trough concentrations. If
the drug shows a delayed effect in QT prolongation, then the timing of ECG collection
should reflect this delay.
3. 	The thorough QT study results in a negative finding, as defined by the E14 criteria,6 at
the therapeutic dose, but the supratherapeutic dose shows a mean effect between 10 and
20 ms. If supratherapeutic exposure is anticipated at the clinical dose only in a well-
characterized subgroup, intensive monitoring as described in Example 2 above could be
carried out in this subset of the phase 3 population. In this case, there should be
reasonable assurance that the higher exposure is unlikely to be seen in the general patient
population. In contrast, if people in the general patient population (who cannot be readily
identified in advance) will in some cases achieve this higher exposure, intensive ECG
monitoring in the phase 3 population is expected, as in Example 2.
4. 	The therapeutic dose results in a mean QTc prolongation of > 20 ms. For drugs with
large QTc prolongation effects, intensive ECG assessment would be appropriate in all
patients in phase 2/3. Because of the risk of TdP, another important use of ECG
monitoring in late phase trials would be to assess any risk mitigation strategies (e.g.,
electrolyte monitoring, dose reduction strategies). Additional ECG assessment over and
above what is recommended earlier in this question and answer might also be called for
(e.g., 24-hour ECG recording, telemetry, multiple trough ECGs through steady state).
The sponsor is encouraged to discuss these approaches with the relevant regulatory agency or
agencies prior to initiation of the phase 3 program.
S7B QUESTIONS AND ANSWERS
I. 	INTEGRATED RISK ASSESSMENT (1)
Q17. 	What is the general strategy for use of nonclinical information as part of an
integrated risk assessment for delayed ventricular repolarization and torsade de
pointes that can inform the design of clinical investigations and interpretation of
their results? (1.1)
The ICH S7B guidance describes a nonclinical strategy for assessing risk of delayed ventricular
repolarization and QT interval prolongation (section II.C (2.3)). A mechanistic understanding of
the development of torsade de pointes (TdP) and the emergence of new types of assays have
made it possible to obtain more information to assess TdP risk from nonclinical assays.
6 Ibid.
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The in vitro IKr/hERG assay and in vivo QT assay as well as optional follow-up studies, as
described in the ICH S7B guidance, are conducted for hazard identification and risk assessment
relevant to delayed ventricular repolarization. It is generally accepted that drugs (note that the
word “drug(s)” in the S7B Q&As is used interchangeably with word “pharmaceutical(s)” in the
ICH S7B guidance) that delay ventricular repolarization may have increased risk of TdP.
In addition to supporting the planning and interpretation of First-in-Human clinical studies,
nonclinical investigations can also contribute to an integrated risk assessment for TdP in later
stages of development when clinical data are available. The following are points to consider
when using in vitro IKr/hERG data and in vivo QT data in combination with clinical QT data as
part of an integrated risk assessment for situations described in ICH E14 Q&As Q12 (5.1) and
Q13 (6.1).
1. 	To predict whether or not the hERG block poses a risk of interfering with ventricular
repolarization or TdP, evaluation of the hERG safety margin based on results of a best
practice assay (see S7B Q&As Q18 (1.2) and Q19 (2.1)) is recommended. ICH S7A
guidance, section II.F (2.6) describes considerations for when human metabolite(s)
should be assessed with in vitro systems. In these cases, the metabolite’s hERG safety
margin should also be evaluated.
2. 	In the in vivo study, the effects on the QTc interval should be assessed at exposures that
cover the anticipated high clinical exposure scenario. The adequacy of exposure to any
major human metabolites should be determined (see ICH S7A guidance, sections II.C.3.b
(2.3.3.2) and II.F (2.6), and S7B Q&A Q28 (3.5)). In addition, if the assay is to be used
as part of an integrated clinical and nonclinical risk assessment for situations where a
conventional thorough QT study is not feasible as described in ICH E14 Q&A Q13 (6.1),
the in vivo study should have sufficient sensitivity to detect a QTc prolongation effect of
a magnitude similar to dedicated clinical QT studies (see ICH S7B Q&A Q27 (3.4)). This
additional consideration (sensitivity similar to dedicated clinical QT studies) does not
apply to decision-making prior to First-in-Human studies or under ICH E14 Q&A Q12
(5.1).
A drug with low TdP risk would be expected to have (1) a hERG safety margin higher than a
threshold defined based on the safety margins computed under the same experimental protocol
for a series of drugs known to cause TdP (see ICH S7B Q&A Q18 (1.2) for additional details);
and (2) no QTc prolongation in an in vivo assay of sufficient sensitivity conducted at exposures
of parent compound and major human metabolites that exceed clinical exposures. See ICH S7A
guidance, section II.F (2.6) for considerations of human metabolite(s) in the in vitro or in vivo
nonclinical assays. If these results are used to support an integrated clinical and nonclinical risk
assessment strategy as described in ICH E14 Q&As Q12 (5.1) and Q13 (6.1), no additional
nonclinical studies are needed. When there are factors that can confound or limit the
interpretation of the nonclinical studies, such as metabolites and heart rate changes, follow-up
studies as described in the ICH S7B guidance (section II.C.5 (2.3.5)) can be performed to
address these specific issues.
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If the hERG assay and/or the in vivo QT study suggest an effect at clinical exposures, the drug
has a risk of interfering with ventricular repolarization. Under this scenario, the drug’s TdP risk
could be affected by various other factors, such as blocking of additional repolarization currents
(e.g., slow delayed rectifier potassium current [Iks]), blocking of inward currents (e.g., sodium
and L-type calcium currents), effects on the trafficking of ion channel proteins from cytoplasmic
sites to the surface membrane, metabolites with ion channel activities, and non-ion channel
mediated QT prolongation. Follow-up studies (ICH S7B guidance, section II.C.5 (2.3.5)) could
be performed to further explore the mechanisms and assess the TdP risk. If applicable, best
practice considerations should be followed for assessment of additional ion channel currents
(S7B Q&A Q19 (2.1)), in vitro cardiomyocyte assays (S7B Q&As Q20 (2.2) to Q23 (2.5)), or in
vivo studies (S7B Q&As Q24 (3.1) to Q28 (3.5)). An appropriately qualified proarrhythmia risk
prediction model (see S7B Q&As Q29 (4.1) to Q30 (4.2)) could be used according to its context
of use to assess the possibility of TdP in humans. Use of in vitro and in silico models can reduce
animal use in follow-up studies in accordance with the 3R (reduce/refine/replace) principles.
The assessment of TdP risk using these follow-up studies, although optional, can be used
together with other relevant nonclinical and clinical information to contribute to the design of
subsequent clinical investigations and interpretation of their results.
Q18. 	What is the recommended method to compute the hERG safety margin? (1.2)
A drug’s potency for hERG block, usually calculated as half-inhibitory concentration (IC50), can
be normalized to the drug’s estimated clinically relevant exposures in patients to calculate the
safety margin. As more information is obtained during the clinical development, the estimated
values of clinical exposures can be refined. When estimating hERG block potency, it is
recommended to use standardized procedures and to consider the principles described in S7B
Q&A Q19 (2.1).
The free drug exposure is computed based on the drug’s total plasma concentration and the
fraction of protein binding. Because of uncertainties in the protein binding measurements, the
unbound (free) fraction in plasma should be set to 1% if experimentally determined to be < 1%.
This approach has been used in the regulatory assessment for the risk of drug- drug interactions.
If protein binding values cannot be accurately assessed (e.g., questionable validation of the
bioanalytical method, deviations from best practices), safety margins should be calculated for
both steady-state free and total Cmax .
In terms of the exposure to use in the denominator of the safety margin calculation for supporting
decision-making under ICH E14 Q&As Q12 (5.1) or Q13 (6.1), it is generally recommended that
the high clinical exposure be used as defined in ICH E14 Q&A Q12 (5.1) (i.e., mean steady-state
maximum concentration (Cmax ,ss) when the maximum therapeutic dose is administered in the
presence of the intrinsic or extrinsic factor that has the largest effect on increasing Cmax,ss ).
To assess whether the hERG block poses a risk of delaying ventricular repolarization or TdP, the
resulting safety margin should be compared to the range of safety margins computed under the
same experimental protocol for a series of reference drugs that have known clinical TdP risk and
cover diverse electrophysiological properties. Additional pharmacological principles or
modeling can be used to justify the use of a certain safety margin threshold (e.g., relationship
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between hERG block and QTc prolongation from semi-mechanistic
pharmacokinetic/pharmacodynamic models or systems pharmacology models; see Leishman et
al. 2020,7 for examples). This should be supported by experimental data based on the principles
in these S7B Q&As (e.g., same experimental protocol applied to a series of drugs with known
clinical TdP risk).
Data supporting the safety margin threshold to define a drug as having low TdP risk should be
supplied in or appended to the submitted study report. If a recommended hERG margin
threshold is published based on principles in these S7B Q&As, a sponsor (or a contract
laboratory) seeking to use the same threshold should demonstrate that the inter-laboratory
variability of IC50s from a set of calibration drugs under the same experimental protocol does
not significantly decrease the sensitivity of the safety margin threshold for detecting drugs that
are not low risk for TdP. Appropriate statistical methods should be applied to quantify
experimental IC50 variability and calculate uncertainty of the safety margin as
confidence/credible intervals.
II. 	BEST PRACTICE CONSIDERATIONS FOR IN VITRO STUDIES (2)
Q19. 	What are some “best practice” considerations when evaluating drug potency on
affecting cardiac ionic currents using patch clamp method and overexpression cell
lines? (2.1)
As outlined in the ICH S7B guidance, the in vitro IKr/hERG assay plays a critical role in
assessing the risk for delayed repolarization and QT interval prolongation prior to first
administration in humans. Nonclinical investigations can also contribute to an integrated risk
assessment in later stages of development when clinical QT data are available. The following
“best practice” aspects should be considered when sponsors are using IKr/hERG data to support
interpretation of clinical QT data in specific scenarios as described in S7B Q&As Q17 (1.1) and
Q18 (1.2) and ICH E14 Q&As Q12 (5.1) and Q13 (6.1), and when using calcium (i.e., CaV1.2)
and sodium (i.e., NaV1.5) data to support a proarrhythmia assessment (ICH S7B Q&A Q17
(1.1)). It is not the intent of these S7B Q&As to make specific recommendations for a sponsor’s
screening activities or for all IKr/hERG assays to support first administration in humans.
Several experimental factors are known to influence the potency of drug effects on cardiac ionic
currents. These include the voltage protocols used to evoke specific ionic currents; experimental
conditions (such as recording temperature, composition of solutions, manual versus automated
assay systems); data acceptance criteria; and data analysis methods employed. Some
recommended best practices are therefore provided to enhance reproducibility of in vitro results
and the translation to clinical findings. These recommendations are generalizable to voltage
clamp experiments characterizing potency of drug inhibition (or potentiation) of cardiac currents.
7 DJ Leishman, MM Abernathy, and EB Wang, 2020, Revisiting the HERG Safety Margin After 20 Years of
Routine hERG Scrrening, Journal of Pharmacological and Toxicological Methods, 105:106900
(https://doi.org/10.1016/j.vascn.2020.106900).
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1. 	Recording temperature: The effects of some drugs are temperature-sensitive, and there is
currently no method to predict which molecules exhibit temperature-dependent effects or
the magnitude of these effects. Thus, patch clamp experiments on cells overexpressing
cardiac ion channels, including hERG, CaV1.2, and NaV1.5, should be performed at near
physiological temperature (35–37 °C).
2. 	Voltage protocol: The voltage protocols used to evoke ionic currents should approximate
the appropriate elements of a ventricular action potential and be repeated at frequencies
that are sufficient to minimize the possibility of missing the effects of a test drug at
physiologically relevant heart rates. For hERG, a stimulation frequency of 0.2 – 1 Hertz
is recommended. For CaV1.2 and NaV1.5 currents, a stimulation frequency of 0.2 Hertz
is recommended. The voltage protocol should include steps that enable monitoring of
cell health and consistent electrophysiological recordings throughout the experiment (i.e.,
estimation of input and series resistance across time). If high seal resistance is achieved,
holding current and input resistance (i.e., measures of passive membrane properties at
rest) can be used as indicators of cell health and experimental stability. After application
of the test drug and if recording quality remains acceptable, a saturating concentration of
a selective blocker should be applied to cells to determine residual background current in
individual cells. If prominent, background current should be factored into potency
determinations.
3. 	Recording quality: Seal resistance should be high enough so that the leak conductance at
all voltages specified by the voltage protocol and series resistance do not compromise
voltage control. The extent of series resistance compensation applied to optimize voltage
control should be noted. Stability of the ionic current should be demonstrated with
baseline recordings (prior to drug application) of sufficient duration to characterize drug-
independent changes (such as current run-down). The time course of drug effects should
be monitored until steady-state effect is obtained, and each cell can be exposed to one or
more drug concentrations as long as cell health and recording quality remain stable.
4. 	Primary endpoint measures: The primary derived endpoints are inhibitory concentration
such as the IC50 value (reported in both micromolar and nanogram/milliliter units) and
Hill coefficient. If 50% current inhibition could not be achieved, a justification of the
highest concentration tested should be provided together with the relation of this
concentration to therapeutic free and total drug levels. Where necessary, to isolate the
current-of-interest, the background current remaining after a high concentration of
selective blocker application should be subtracted. If current inhibition with a selective
blocker could not be achieved, leak current can be calculated and subtracted from the
current traces. This approach assumes that only the current-of-interest is voltage-
dependent, hence evidence and justification should be provided on why it was used.
5. 	Data summary: Inhibition at each drug concentration for each cell should be provided,
along with the mean values of IC50 and Hill coefficient (and appropriate measures of
data variability). To demonstrate recording quality, the study report should also contain
time-course plots of current amplitude, input resistance, holding current for individual
cells in control condition followed by drug application, and drug equilibration. If time-
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dependent changes such as current run-up or run-down in baseline condition were
corrected for drug inhibition estimation, the correction method applied should be
described.
6. 	Concentration verification: The concentration of test compound to which the cells were
exposed should be verified by applying a validated analytical method to the solution
collected from the cell chamber. Both nominal and measured concentrations should be
reported. If the nominal and measured concentrations differ significantly from each
other, measured concentrations should be used to construct the concentration-response
relationship to estimate IC50 and Hill coefficient.
7. 	Positive and negative controls: The positive control drug should be one of the “reference
drugs” referred to in S7B Q&A Q18 (1.2). The positive control drug should be tested
using sufficient replicates and two or more concentrations achieving 20-80% block, to
demonstrate consistency and reproducibility with the reference drug data. If positive
control data fall outside the range of expected values, then the study is inconclusive, and
it is not recommended that the data be used to support the purposes outlined in ICH E14
Q&As Q12 (5.1) and Q13 (6.1). Vehicle (negative) controls should be included in the
experiments. The vehicle should include all non-compound materials in the test article
solution, such as solubilizing agents and preservatives.
Q20. 	What are the relevant endpoints of an informative in vitro human cardiomyocyte
repolarization follow-up study? (2.2)
As outlined in the ICH S7B guidance, follow-up studies (section II.C.5 (2.3.5)) can include in
vitro ventricular repolarization assays. Follow-up studies are not performed for all submissions
and are often designed to address specific issues. Since implementation of the ICH S7B
guidance, new technologies have become available, including assays with human-induced
pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). S7B Q&As Q20 (2.2) to Q23 (2.5)
outline best practice considerations when in vitro cardiomyocyte assays are performed as follow-
up studies.
Drug-induced changes in the intracellular or extracellular action potential waveforms recorded
from hiPSC-CM preparations and acutely isolated adult human ventricular myocytes reflect the
integrated effect on multiple ionic currents, exchangers, and carriers. Changes in cellular
repolarization recognized as markers of ventricular proarrhythmia include delayed and abnormal
repolarization (manifest as early afterdepolarizations, triggered activity or irregular beating) and
should be noted.
Drug-induced effects on cardiomyocyte calcium handling (calcium transients, contractility, or
calcium homeostasis) could affect electrophysiological activity. These effects may manifest as
abnormal mechanical activity associated with proarrhythmic mechanisms (e.g., prolonged
contractions, single or multiple premature contractions linked to triggered electrical activity such
as early afterdepolarizations). The assessment of changes in calcium handling is useful for
describing the presence or absence of potential proarrhythmic activity. However, such measures
are inadequate to fully characterize the electrophysiological effects of a drug on repolarization.
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Q21. 	What elements of the test system should be considered for an in vitro human
cardiomyocyte repolarization assay? (2.3)
It is important to describe the biological preparation and technology platform that define baseline
electrophysiological characteristics and drug responses.
 	Biological preparation: The origins of cells studied, and human donor characteristics
should be specified. If complex preparations containing hiPSC-CMs are used (e.g., co-
cultures, organoids, engineered heart tissues), descriptions of the protocols used in
creating these preparations should be provided. For primary human cardiomyocyte
preparations, the tissue sources, harvesting, isolation, and enrichment procedures
followed should be described. Acceptable morphological and functional inclusion
criteria for the preparations as well as electrophysiologic characteristics (including
baseline action potential/field potential durations, spontaneous beat frequency and
variability (if applicable), resting membrane potential, upstroke characteristics,
conduction patterns and/or velocity) should be clearly defined. Estimates of the
proportion of preparations fulfilling criteria should be included.
 	Technology platform: The methodologies used (e.g., transmembrane potential recordings
(whole cell patch clamp, sharp electrode, or voltage-sensing dye approaches),
extracellular recordings using field potentials, visual or impedance-based motion
approaches, or calcium-sensing dyes) should be clearly described. The analysis package
used for marking and interpreting waveforms should be described, with representative
recordings (along with pertinent waveform markings) provided. A description of the
plates or chambers used (including presence or absence of flow, substrate composition,
recording electrode characteristics) should be provided.
Q22. 	What are important considerations when designing and implementing experimental
protocols for in vitro cardiomyocyte repolarization studies? (2.4)
Protocols should be designed to address a specific question (e.g., concentration-dependent effects
on repolarization). The rationale of choosing a single- or sequential-dose protocol should be
provided. Bath temperature should be stable at physiologic (35–37 ºC) temperature. The
sampling “window” for data collection should be clearly defined. Deviations from protocols
should be clearly described, along with expected consequences.
 	For spontaneously beating preparations, changes in beating rate influence repolarization
independent of direct drug effects on repolarizing currents. Spontaneous beat rates in the
absence and presence of drugs should be clearly indicated along with the extent of drug-
induced rate changes. The choice and justification of correction formula used when
assessing repolarization effects in such preparations should be provided. Due to
limitations of rate correction in spontaneously beating hiPSC-CMs, interpretation of
potential repolarization changes may not be possible when a drug causes a rate change.
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 	For paced preparations, the pacing protocol (pattern and duration) should be described
and performed in the presence and absence of test compound.
 	To demonstrate recording quality, the study report should contain time-course plots of
primary endpoints (demonstrating drug equilibration) and other parameters that can be
used to infer stability of the preparations and signal recordings.
 	Concentration-dependent repolarization effects can be derived based on vehicle-
corrected and/or baseline subtracted comparisons of drug versus vehicle treated
preparations. For higher throughput multi-well platforms, it is preferable to conduct
vehicle and test drug studies on the same plate. The number of replicates (useful for
evaluating reproducibility but not inferential statistical testing) should be reported.
Power calculations are helpful to establish statistical sensitivity to repolarization
endpoints.
 	It is important to characterize drug exposures during in vitro cardiomyocyte
repolarization studies. For well-based studies, drug exposures could be verified using
media sampled from test wells or from “satellite studies” (parallel studies using identical
protocols and study conditions conducted without measuring electrophysiologic
measurements). With continuous flow systems, the sampling of effluent from test
chambers is valuable for assessing drug exposures. Exposures should be presented as
total drug concentration and free drug concentrations (if plasma protein binding
characteristics in the media used is known).
Q23. 	How does one define biological sensitivity of a cardiomyocyte in vitro repolarization
assay? (2.5)
The electrophysiologic sensitivity of cardiomyocyte preparations should be calibrated with
established positive controls to confirm their “fit for purpose” role in defining pharmacological
block of cardiac ion channel(s). This is readily accomplished by constructing concentration-
response curves with recognized and specific ion current blocking agents.
 	At minimum, it is important to characterize sensitivity to block of the prominent outward
repolarizing current IKr/hERG with specific blocking agents (e.g., E-4031 or dofetilide)
over relevant concentration ranges.
 	Block of the inward L-type calcium current (ICaL) and late sodium current (INaL) may
mitigate delayed repolarization. Demonstrating sensitivity to specific ICaL (e.g.,
nifedipine or nisoldipine) and INaL (e.g., mexiletine or lidocaine) blocking agents is
helpful for clarifying integrated cellular electrophysiological responses of multi-channel
blocking drugs.
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III. 	BEST PRACTICE CONSIDERATIONS FOR THE IN VIVO QT STUDIES (3)
Q24. 	What are best practice considerations for species selection and general design of the
(standard) in vivo QT study? (3.1)
The most appropriate species should be selected and justified (ICH S7B guidance, section II.C
(3.1.3)). It is preferable to use the same animal species in the safety pharmacology and non-
rodent toxicity studies to facilitate understanding of the possible relationship between adverse
cardiovascular pharmacodynamic effects and structural effects on the heart, and to obtain
complementary information on systemic exposure level (toxicokinetics).
Although it is customary to use conscious freely moving telemeterized animals for the in vivo
QT studies, the choice of alternative model approaches (e.g., anesthetized or paced animals)
might be justified in certain circumstances to achieve adequate exposures or to overcome
specific compound-related challenges (e.g., changes in heart rate, tolerability, or bioavailability
limitations in conscious animals).
Q25. 	What should be considered for exposure assessment during the in vivo QT study?
(3.2)
The ICH S7B guidance states that drug exposures should include and exceed anticipated
therapeutic concentrations. If the in vivo QT data are to be used as part of an integrated risk
assessment for situations described in ICH E14 Q&As Q12 (5.1) and Q13 (6.1), the exposure
should cover the anticipated high clinical exposure scenario (see S7B Q&A Q17 (1.1)). An
assessment of exposure in the same animals used for the pharmacodynamic assessment is
encouraged. Sampling should take place at relevant timepoints and in a manner that limits
interference with the pharmacodynamic effects. This could be done by sampling complete
pharmacokinetic profiles in the same animals on a separate day after an adequate washout or
different animals. At least one pharmacokinetic sample should be obtained during the
pharmacodynamic assessment day to demonstrate consistency with the full pharmacokinetic
profiles. In certain cases, the analysis of QTc interval together with adequate pharmacokinetic
sampling makes it possible to perform dedicated exposure-response modeling similar to
concentration-QT analysis for clinical QT studies. This can be helpful when the study should be
powered to detect an effect similar to dedicated QT studies in humans (e.g., when using in vivo
QT data as part of an integrated nonclinical and clinical risk assessment as described in ICH E14
Q&A Q13 (6.1)) because it can reduce the number of animals in accordance with the 3R
(reduce/refine/replace) principles. In addition, exposure-response modeling may be helpful in
other circumstances when QT prolongation is observed or anticipated based on hERG assay
results.
Q26. 	What information is needed to support the choice of heart rate correction method in
an in vivo QT assay? (3.3)
Optimally, the sponsor should demonstrate the independence of QTc to RR (RR is the time
between heart beats, measured as R waves on the ECG) intervals observed in the study through
QTc versus RR plots accompanied by additional information (e.g., number of matched QTc-RR
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pairs, correlation metric, 95% confidence intervals, p-values). QT-RR interval relationship is
also important. Justification of correction factors used for QT measures should be provided
when test drugs affect heart rate. In certain cases, individual QT correction based on QT-RR
relationship is a preferred method because it is more accurate and sensitive than the general
methods such as Bazett, Fridericia, or Van de Water when the test drugs affect heart rate. The
main reason for not using correction formulae based on historical data is the fixed-rate correction
coefficients. Non-rodent species show species-specific and individual differences in their QT-
RR relationships.
Q27. 	How should the sensitivity of the assay be evaluated? (3.4)
The test system used for an in vivo QT assay should provide a robust response. Assay sensitivity
of relevant functional endpoints should be evaluated and reported to enable data interpretation
(in supporting initiating first-in-human studies and/or an integrated nonclinical and clinical
integrated risk assessment to be applied under the scenarios in ICH E14 Q&A Q12 (5.1) or Q13
(6.1) and contextualization. Demonstration of assay sensitivity can be achieved by defining
minimum detectable differences and testing the effects of positive controls. Statistical power
calculations could also be provided from historical data from the same laboratory using the
identical protocol. If historical positive control data are used to justify assay sensitivity or
statistical power is calculated from historical control data, then the variance of the present data
should be consistent with that seen historically.
If study results are to be used to support an integrated nonclinical and clinical risk assessment
described in ICH E14 Q&A Q13 (6.1), then the study should have sensitivity to detect a QTc
prolongation effect of a magnitude similar to dedicated clinical QT studies, taking into
consideration inter-species differences in the normal range of values for the QTc interval. The
overall sensitivity of the nonclinical assay in comparison to clinical QT studies depends on both
the electrocardiographic assessment and the exposure achieved in the in vivo assay relative to
high clinical exposure. This can help reduce the numbers of animals used in accordance with the
3R (reduce/refine/replace) principles. The following hypothetical example is offered for
consideration with recognition that the QTc threshold and exposure multiples selected for a
particular study should be justified by data obtained in the specific species tested, using
recognized reference compounds under conditions consistent with the best practice
recommendations set forth in these S7B Q&As.
 	Hypothetical Example: The minimal detectable difference might be 5 milliseconds if
drug exposure in the animal study only covers the high clinical exposure, but might be
higher if a larger multiple of high clinical exposure is achieved (e.g., 10 milliseconds if
3X high clinical exposure is achieved, or a higher QTc threshold if an even larger
multiple is achieved).
Q28. 	What are the recommended conventions for presenting the pharmacodynamic
and pharmacokinetic results of an in vivo QT assay? (3.5)
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Pharmacodynamic Content
 	Summary tables and figures showing absolute mean values, mean percentage change
from baseline, confidence intervals, and p-values for changes from baseline and vehicle
control should be included.
 	If study results are being used to support ICH E14 Q&A Q13 (6.1), then data from
positive controls should be included or appended. If historical positive controls are used,
then the variance of the present data should be consistent with that seen historically,
which can be demonstrated by reporting minimal detectable differences with by time
analysis. A statement should be provided that the data for the new drug and the historical
data were collected according to the same protocol and statistical analysis plan. If
deviations are present, they should be clearly justified. If concentration-QTc modeling is
performed, reporting should follow similar principles as for human concentration-QTc
modeling (see ICH E14 Q&A Q12 (5.1)).
Pharmacokinetic Content
 	Tabulations of summary statistics for Cmax , AUC, and Tmax for the parent drug and
metabolites along with plasma concentration versus time plots (if sufficient samples have
been collected to support their calculation) should be provided.
Individual animal data should be provided.
IV. 	PRINCIPLES FOR PROARRHYTHMIA MODELS (4)
Q29. 	The ICH S7B guidance (section III.D (3.1.4)) states that directly assessing the
proarrhythmic risk of pharmaceuticals that prolong the QT interval would be a
logical undertaking and interested parties are encouraged to develop these models
and test their usefulness in predicting risk in humans. What are general principles
to evaluate whether a proarrhythmic risk prediction model could be used as part of
an integrated risk assessment strategy? (4.1)
Different models, including in silico, in vitro, ex vivo and in vivo models, have the potential to
be used as part of an integrated risk assessment strategy to evaluate the proarrhythmic risk of
QT-prolonging pharmaceuticals in humans. Using in vitro and in silico models can also reduce
animal use in accordance with the 3R (reduce/refine/replace) principles. Because these models
have a common feature of using nonclinical experimental data as input and generating human
proarrhythmia risk prediction as output, they can generally be referred to as proarrhythmia risk
prediction models. The model input can vary among different models, for example, ion channel
pharmacology data as input to in silico models, drug-induced changes in cellular repolarization
and/or arrhythmia events as input to hiPSC-CM models, and drug- induced electrocardiographic
changes as input to ex vivo/in vivo models. However, the model output (either discrete risk
categories or continuous risk scores) is similar among different models. Such a feature makes it
possible to develop generic principles for evaluating the predictivity of proarrhythmia risk
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prediction models without specifying the type of underlying experimental data used as model
input. The following general principles should be applied to all proarrhythmia risk prediction
models intended to be used as part of an integrated risk assessment for regulatory purposes.
Although the main focus of these principles is to evaluate a model’s predictivity of TdP risk,
they are general enough to guide the development of models predicting different types of
proarrhythmia.
1. 	A defined endpoint consistent with the context of use of the model. Examples of model
endpoints (e.g., TdP risk versus QT prolongation risk) can be found in Li et al. 2020.8
2. 	A fully disclosed algorithm to translate experimental measurements (model input) to
proarrhythmia risk (model output), allowing independent reproduction of the model
development process using the associated training and validation datasets to evaluate the
model performance.
3. 	A defined domain of applicability/scope and limitations of the model. This includes the
experimental protocols to generate model input (experimental data capturing
pharmacological effects of drug), and the compounds tested should have the same
arrhythmic mechanisms covered by the model.
4. 	A prespecified analysis plan and criteria to assess model predictivity. The analysis plan
should include methods to separate the training and validation steps. In the training step,
a series of reference compounds is used to adjust the model. In the validation step,
another series of reference compounds is used to evaluate the performance of the
prespecified model. The reference compounds used for the training and validation steps
should not overlap.
5. 	A mechanistic interpretation of the model, which describes the relationship between the
model inputs and mechanism for the arrhythmia.
6. 	The uncertainty in the model inputs should be captured and propagated to the model
predictions. The experimental variability associated with model input should be
quantified using appropriate statistical methods and then translated into probabilities of
the predicted risk.
After a proarrhythmia risk prediction model has been developed, a process should be followed to
evaluate whether the model development complied with these principles. Such a process would
support that the model is qualified for the intended context of use as part of an integrated risk
assessment for regulatory purposes. Some health authorities have procedures for the formal
qualification of models that allow for a model to be used within the qualified context of use
without the regulatory authority needing to reconsider and reconfirm its suitability. Model
developers are encouraged to contact a regulatory agency about its specific model qualification
procedures. After a model has been qualified, the use of such a model is not limited to the
8 Z Li, GR Mirams, T Yoshinaga et al., 2020, General Principles for the Validation of Proarrhythmia Risk Prediction
Models: An Extension of the CiPA In Silico Strategy, Clinical Pharmacology & Therapeutics, 107(1): 102-111
(https://doi.org/10.1002/cpt.1647).
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specific facility that submitted the qualification package. However, if another facility intends to
use the qualified model, that facility should perform laboratory-specific calibration and
validation of the model using a subset of the reference compounds that were originally used to
develop the model. An illustrative process of performing laboratory-specific calibration and
validation is given in Han et al. 2020.9
Q30. 	How can a sponsor use a model for regulatory submission and what are the
limitations? (4.2)
Sponsors can use results from a qualified proarrhythmia model as one component in the totality
of evidence approach to risk assessment under the context of use for which the model was
developed and qualified. When a facility intends to use the model to produce data for regulatory
submission, a set of control compound(s) should be tested to assess the consistency between the
new data and the historical laboratory-specific validation data. The number and type of
laboratory-specific calibration and control compounds should be justified.
If a proarrhythmia model is included in a regulatory submission, proof of qualification of the
model under the guidance of the general principles in this Q&A should be provided in an
appendix to the study report. Supportive documentation could include published papers, if the
included validation dataset is described in sufficient detail to allow an independent assessment.
Importantly, the general principles for model qualification set forth in this Q&A only support the
use of a proarrhythmia risk prediction model as part of an integrated risk assessment that
incorporates all relevant nonclinical and clinical information.
9 X Han, M Samieegohar, BJ Ridder et al., 2020, A General Procedure to Select Calibration Drugs for Lab-Specific
Validation and Calibration of Proarrhythmia Risk Prediction Models: An Illustrative Example Using the CiPA
Model, Journal of Pharmacological and Toxicological Methods, 105:106890
(https://doi.org/10.1016/j.vascn.2020.106890).
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