INTERNATIONAL  CONFERENCE  ON  HARMONISATION  OF  TECHNICAL
REQUIREMENTS FOR REGISTRATION OF PHARMACEUTICALS FOR HUMAN USE
DRAFT ICH CONSENSUS PRINCIPLE
PRINCIPLES FOR CLINICAL EVALUATION OF
NEW ANTIHYPERTENSIVE DRUGS
Signed as a Principle Document
on 2 March 2000
by the ICH Steering Committee
This consensus draft text, agreed by the appropriate ICH Expert Working Group, is
transmitted by the ICH Steering Committee to the regulatory authorities of the three ICH
regions (the European Union, Japan and the USA) for internal and external consultation,
according to national or regional procedures.
This draft guidance, when finalized, will represent the Food and
Drug Administration=s current thinking on this topic.  It does not
create or confer any rights for or on any person and does not
operate to bind FDA or the public.  An alternative approach may
be used if such approach satisfies the requirements of the
applicable statutes, regulations, or both.  PRINCIPLES FOR CLINICAL EVALUATION OF
NEW ANTIHYPERTENSIVE DRUGS
Draft ICH Consensus Principle
Signed as a Principle Document, 2 March 2000, by the ICH Steering Committee
 
 TABLE OF CONTENTS
INTRODUCTION..............................................................................................................  1
1. General Principles for the Assessment of Efficacy...................................  1
2. Study Population.....................................................................................................  2
3. Assessment of Antihypertensive Effect..........................................................  2
3.1 Studies to Assess Antihypertensive Effects................................................................  2
3.2 Pharmacodynamic Studies.............................................................................................  4
3.3 Dose response relationship...........................................................................................  4
3.4 Comparison with Standard Therapy............................................................................  4
4. Assessment of Safety...............................................................................................  4
5. Co-Administration with other Antihypertensives.....................................  5
6. Fixed Combination Products..............................................................................  5
6.1 Factorial Study................................................................................................................  5
6.2 Studies in Non-responders to Each Drug....................................................................  6
APPENDIX..........................................................................................................................  7
i  PRINCIPLES FOR CLINICAL EVALUATION OF
NEW ANTIHYPERTENSIVE DRUGS
INTRODUCTION
This document provides general principles for the clinical evaluation of new anti-
hypertensive  drugs.  It  describes  core  principles  for  the  evaluation  of
antihypertensives that are accepted in the three ICH regions, but some region-specific
differences remain. These differences may be harmonized in future, but it is important
at  present  to  refer  to  existing  regional  guidelines  and  to  discuss  the  specific
requirements with regional regulatory authorities, if required. This document should
be considered together with a number of pertinent ICH guidelines:
E1  : The Extent of Population Exposure to Assess Clinical Safety.
E3  : Structure and Content of Clinical Study Reports.
E4  : Dose-Response Information to Support Drug Registration.
E5  : Ethnic Factors in Acceptability of Foreign Clinical Data.
E6  : Guideline for Good Clinical Practice.
E7  : Studies in Support of Special Populations : Geriatrics.
E8  : General Considerations for Clinical Trials.
E9  : Statistical Principles for Clinical Trials.
E10 : Choice of Control Group in Clinical Trials.
E11 : Clinical Investigation of Medicinal Products in the Pediatric Population.
There are, in addition, existing regional guidelines or draft guidelines.
CPMP: Note  for  Guidance  on  Clinical  Investigation  of  Medical  Products  in  the
Treatment of  Hypertension.
FDA: Proposed Guidelines for the Clinical Evaluation of Antihypertensive Drugs.
MHW: Guideline for the Clinical Evaluation of Antihypertensive Agents.
1. GENERAL PRINCIPLES FOR THE ASSESSMENT OF EFFICACY
The primary basis of assessment of efficacy of antihypertensive drugs is the effect of
the drug on systolic and diastolic blood pressures.  In the past the primary endpoint of
most studies was diastolic blood pressure.  Although all drugs to date have reduced
both systolic and diastolic blood pressures, the recognition of isolated or predominant
systolic hypertension as a significant and remediable risk factor demands explicit
1 Principles for Clinical Evaluation of New Antihypertensive Drugs
evaluation of the effect of a drug on systolic blood pressure.  Many clinical trials of
many  interventions  (including  low  and  high  dose  diuretics,  reserpine,  and  beta-
blockers, usually as part of combination therapy) have shown consistent beneficial
effects  on  long-term  mortality  and  morbidity,  most  clearly  on  stroke  and  less
consistently on cardiovascular events.  Whether some drugs or combinations have
better effects than others on overall outcomes or on particular outcomes is not yet
known.
Formal  mortality  and  morbidity  outcome  studies  are  not  ordinarily  required  for
approval  of  antihypertensive  drugs  and  the  kind  of  active  control  mortality  and
morbidity studies that would be convincing is not well defined.  Results of a large
number of on-going outcome studies could affect this policy and modify requirements.
It  should  be  noted  that,  even  if  an  antihypertensive  effect  has  been  proven,  a
significant  concern  about  a  detrimental  effect  on  mortality  and/or  cardiovascular
morbidity might lead to a need for outcome studies.
2. STUDY POPULATION
The patient population studied with a new antihypertensive should include a broad
range of patients with essential hypertension.  Most patients will be in the mild to
moderate range.  Studies of patients with both diastolic and systolic hypertension are
expected. More severe hypertension should also be studied.  Patients with relevant
concomitant illness (such as diabetes mellitus and coronary heart disease) should be
included unless the drugs they need would interfere with the study; e.g., for patients
with heart failure standard treatment requires use of one to several agents affecting
blood pressure that could have pharmacologic actions similar to the study drug.
In general, patients with target organ damage secondary to hypertension should not
be included in placebo-controlled trials of more than very brief duration,  although
such patients can be included in active controlled trials.  Patients from relevant
demographic subsets should be studied, including both men and women, racial/ethnic
groups pertinent to the region, and both young and older patients.  The very old or
"fragile elderly," i.e., patients >75 years old, should be included.  In general, all
population subsets should be included in the same studies, rather than conducting
studies  in  subgroups.    This  facilitates  comparisons  across  subsets  in  the  same
environment.  An exception would be severity subgroups, where study designs could
be different for different severities.  Patients with secondary hypertension, isolated
systolic  hypertension,  and  hypertension  during  pregnancy,  and  children  with
hypertension should be studied separately, if specific indications for use in those
populations are being sought.
3. ASSESSMENT OF ANTIHYPERTENSIVE EFFECT
3.1.Studies to Assess Antihypertensive Effect
The primary endpoint of studies to assess antihypertensive effect is the absolute
change  at  the  end  of  the  dosing  interval  (trough)  from  drug-free  baseline  blood
pressure compared to the change in the control group.  As a secondary endpoint
effects can also be assessed with respect to pre-defined response criteria. In general,
the effect on blood pressure at the end of the study is the primary endpoint, but the
2 Principles for Clinical Evaluation of New Antihypertensive Drugs
time  course  of  the  onset  of  the  effect  is  also  of  interest;  this  can  be  defined  by
examining trough response each week or every two weeks in some studies.  The effect
on blood pressure and the relationship of the response to dose should be characterized
in short-term studies (4-12 weeks), whose short duration allows for use of a placebo
control.    Long-term  (six  months  or  more)  studies  should  also  be  carried  out  to
demonstrate maintenance of efficacy and to look for withdrawal effects.
Because  blood  pressure  readings  (except  perhaps  ABPM  readings)  are  subject  to
systematic error (bias), because spontaneous changes in blood pressure can be large,
and because the effect of active drugs is often small (diastolic blood pressure change of
4-5 mm Hg more than placebo), studies conducted in a blinded fashion and with
placebo controls are essential (See ICH E10).  In general, short-term studies should be
placebo-controlled.  Dose-response studies and studies using an active control drug as
well as placebo are strongly encouraged. Controlled randomized short-term studies of
various designs can be useful in demonstrating effectiveness, for example (See also
Appendix):
A)  Single fixed-dose vs. placebo
B)  Optional titration (based on response) vs. placebo
C)  Forced titration vs. Placebo
D)  Fixed-dose,  dose-response  vs.  placebo  (can  use  forced  titration  to  reach  the
randomly assigned fixed maintenance dose)
E)  Any of the above designs with an active control drug
Long-term studies to show efficacy (and which are also needed for assessment of long
term safety) would usually use active controls, preferably with a placebo-controlled
randomized withdrawal study at the end of treatment to establish assay sensitivity
(See ICH E10) and assess possible withdrawal effects.  Another long-term active
control  trial  design  that  could  support  assay  sensitivity  would  be  one  in  which
patients are initially randomized to three treatments (test drug, active control drug
and a placebo), with the placebo only maintained for short time (e.g., one month).  A
long-term open exposure followed by a placebo controlled randomized withdrawal
could also show long-term efficacy.
The effect of the drug over the duration of the dosing interval has generally been
evaluated in recent years with ABPM studies (which can incorporate dose-response
elements  and  an  active  control),  but  studies  that  measure  blood  pressure  at
approximate peak and at trough (pre-dosing) blood levels can also be used.  Specific
requirements vary among regions. Additional information may be obtained from self
(home)  measurement  of  blood  pressure  with  the  help  of  automatic  devices,  but
validation of the device used is necessary. If peak and trough blood pressure effects
differ  substantially,  a  more  frequent  dosing  interval  should  be  studied.    The
trough/peak ratio should be evaluated.  Although strict rules (e.g., placebo-subtracted
trough/peak at least 50%) have been suggested, interpretation of these ratios has
generally been flexible.  The principal concern is that there needs to be an adequate
blood pressure control late in the dose interval, without an excessive fall in blood
pressure at peak resulting from a desire to have a long dose interval (e.g., to gain a
once daily dosing claim for a short - acting drug).
3 Principles for Clinical Evaluation of New Antihypertensive Drugs
Conditions of blood pressure measurement should be well described and standardized
with respect to time of day, patient position and specific measurement procedures.
3.2.Pharmacodynamic Studies
The pharmacodynamic properties of antihypertensive drugs should be characterized.
Studies should be performed to evaluate such properties as hemodynamic effects,
renal effects, and neurohumoral effects.  In general, it is useful to characterize the
magnitude, dose-response, and time-course of these effects.  These studies should
usually be placebo-controlled.
3.3.Dose Response Relationship
The dose-response (D/R) relationship for favorable (blood pressure) and unfavorable
effects of anti-hypertensive drugs should be well-characterized through randomized
fixed-dose,  D/R  studies.    In  these  studies,  a  greater  number  of  dose  groups  will
provide a better D/R assessment.  If possible, at least three doses (in addition to
placebo) should be used.  Although trials usually use a randomized parallel fixed-dose,
D/R design (See ICH E4), some studies could utilize a placebo-controlled titration
design, appropriately analyzed, to narrow the range of doses to be studied in fixed-
dose studies, and to characterize individual D/R relationships.  Either or both of these
designs can provide evidence for anti-hypertensive efficacy.  These D/R studies (See
ICH E4) should characterize critical parts of the D/R curve, allowing identification of
the lowest dose with some useful effect, a dose on the steep part of the D/R curve, and
a dose beyond which further effects are absent or small (maximum useful dose).  If
there is a positive D/R slope, a D/R study can show effectiveness even without a
placebo, but it may provide little information on the value of the lower doses (which
may then need further study).  A D/R study may be uninformative if all doses show
equal effects.
3.4.Comparison with Standard Therapy
The need for studies comparing the new drug with current standard therapy varies
among regions but comparative studies are of interest in all regions.  In order to
assess  antihypertensive  efficacy,  these  trials  need  to  document  assay  sensitivity
through a placebo arm or a terminal placebo-controlled randomized withdrawal phase.
For the short-term studies, a 3-arm design (test drug, active control drug, and placebo)
may be particularly helpful as a study that not only supports efficacy but also makes a
comparison with standard therapy.  If the effect size (vs. placebo) is unusually small, it
can be helpful to know whether this was the result of the study population, or other
study features (test and control drugs both have small effect vs. placebo), or the drug
(active control drug has a larger effect than test drug compared to placebo).  For
longer-term comparative studies, where concurrent placebo-control is not possible,
the approaches to demonstrating assay sensitivity described in Section 3.1 should be
considered.
4. ASSESSMENT OF SAFETY
ICH E1 suggests that a database of about 1500 patients (300 - 600 for 6 months, 100 for
1 year) is usually sufficient for chronically administered drugs, but as suggested in
4 Principles for Clinical Evaluation of New Antihypertensive Drugs
that guideline, this may be too small for the very long, very wide exposure in an
asymptomatic population intended for antihypertensive drugs.
In addition to the usual safety assessments, attention should be paid to excessive fall
in blood pressure (hypotension), especially on standing (orthostatic hypotension), and
rebound  phenomena.    Depending  on  the  particular  drug  and  other  observations,
studies of effects on heart rhythm or cardiac conduction, coronary steal effects, effects
on risk factors for cardiovascular disease (e.g., blood glucose, lipids), and effects on
target organ damage are of interest.
5. CO-ADMINISTRATION WITH OTHER ANTIHYPERTENSIVES
As antihypertensive treatments are often used in combination, it is important to study
the efficacy and safety of the new drug in this situation. Information on combination
use can be obtained in formal factorial studies and in combined use in the course of
long- and short-term clinical studies.  Specific requirements regarding clinical co-
administration studies may vary among regions.
Studies  in  patients  with  inadequate  blood  pressure  control  on  other  agents  will
provide information on the effect of the test drug when added to other agents (add on
studies).  Studies in which additional drugs are added to the test drug to achieve an
adequate response may also be useful.
6. FIXED COMBINATION PRODUCTS
There are two approaches to the combination studies needed to obtain safety and
efficacy data to support fixed combination products.  It is essential to consult with
regional regulatory authorities regarding the specific data needed to support the
specific indications.
6.1.Factorial Study
In a factorial study, placebo, and one or more doses of the test drug T and another
drug  D  are  studied  alone  and  in  the  combination  in  a  short-term  randomized
controlled trial.  Such a trial can be used to show that the combination has a greater
effect than either drug alone.   Most informative for identifying the appropriate
dosages for a fixed combination is a factorial D/R study in which several doses of each
drug, e.g., a test drug T and another drug D, and their combinations are compared, as
shown below.
Placebo T T T
1 2 3
D T D T D T D
1 1 1 2 1 3 1
D T D T D T D
2 1 2 2 2 3 2
D T D T D T D
3 1 3 2 3 3 3
5 Principles for Clinical Evaluation of New Antihypertensive Drugs
This design reveals D/R relationships for the test drug and other drug alone and in
combination with each dose of the other treatment and may support one or more fixed
combinations.  These studies reveal "response surface" relationships that use data
from all groups.  It may be necessary to study separately the low doses and low dose
combinations to establish their specific usefulness.
6.2.Studies in Non-responders to Each Drug
The safety and efficacy of combinations can also be assessed by examining the effect of
the combination in patients failing to respond to both of the single drugs, e.g., diastolic
blood pressure > 90 mmHg on that component.  In some cases, regional authorities
only require trials in patients failing to respond to one of the components.
6 Principles for Clinical Evaluation of New Antihypertensive Drugs
APPENDIX
SHORT-TERM STUDY DESIGNS    (T: Test Drug    P: Placebo)
A.  Single fixed-dose vs. placebo
  Group  A                   T  4mg
Group  B                    P
B.  Optional titration (based on response) vs. Placebo
                                                                T (8mg)
    Group  A          T (4mg)
                           T 2mg
    Group  B           P              P                   P
(  ):If needed to reach goal
C.  Forced titration vs. Placebo
    Group  A       T 2mg       T 4mg          T 8mg
    Group  B           P             P                 P
D. Fixed-dose,  dose-response  vs.  placebo  (can  use  forced  titration  to  reach  the
randomly assigned fixed maintenance dose)
Group  A               T 2mg
Group  B               T 4mg
Group  C               T 8mg
Group  D               P
or
Group  A       T 2mg     T 2mg       T 2mg
Group  B       T 2mg     T 4mg       T 4mg
Group  C       T 2mg     T 4mg       T 8mg       
Group  D         P             P               P
7 Principles for Clinical Evaluation of New Antihypertensive Drugs
E.  Any of the above designs with an active control drug
8