Guidance for Industry 
 
Q5E Comparability of 
Biotechnological/Biological 
Products Subject to Changes in 
Their Manufacturing Process  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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) 
 
June 2005 
ICH 
 
 
   
Guidance for Industry 
 
Q5E Comparability of 
Biotechnological/Biological 
Products Subject to Changes in 
Their Manufacturing Process  
 
 
 
 
 
Additional copies are available from: 
 
Office of Training and Communication 
Division of Drug Information, HFD-240 
Center for Drug Evaluation and Research 
Food and Drug Administration 
5600 Fishers Lane 
Rockville, MD  20857 
(Tel) 301-827-4573 
 http://www.fda.gov/cder/guidance/index.htm 
 
Office of Communication, Training and  
Manufacturers Assistance, HFM-40  
Center for Biologics Evaluation and Research 
 Food and Drug Administration 
1401 Rockville Pike, Rockville, MD 20852-1448  
 http://www.fda.gov/cber/guidelines.htm.   
 (Tel) Voice Information System at 800-835-4709 or 301-827-1800 
 
 
 
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) 
 
June 2005 
ICH 
 
  Contains Nonbinding Recommendations 
 
 
TABLE OF CONTENTS 
 
 
 
I.  INTRODUCTION (1) .......................................................................................................1 
A.  Objectives of the Guidance (1.1)...........................................................................................1 
B.  Background (1.2)..................................................................................................................2 
C.  Scope (1.3)............................................................................................................................2 
D.  General Principles (1.4)........................................................................................................3 
II.  GUIDANCE (2)..................................................................................................................4 
A.  Considerations for the Comparability Exercise (2.1) ............................................................4 
B.  Quality Considerations (2.2).................................................................................................5 
1. Analytical Techniques (2.2.1)..................................................................................................5 
2. Characterization  (2.2.2).........................................................................................................6 
3. Specifications (2.2.3)..............................................................................................................8 
4. Stability (2.2.4)......................................................................................................................8 
C.  Manufacturing Process Considerations (2.3)........................................................................9 
D.  Demonstration of Comparability During Development (2.4)...............................................10 
E.  Nonclinical and Clinical Considerations (2.5).....................................................................11 
1. Factors To Be Considered in Planning Nonclinical and Clinical Studies (2.5.1).......................11 
2. Type of Studies (2.5.2)..........................................................................................................12 
GLOSSARY (3)............................................................................................................................13 
REFERENCES (4).......................................................................................................................14 
  Contains Nonbinding Recommendations 
 
1
Guidance for Industry  
 
Q5E Comparability of Biotechnological/Biological Products 
Subject to Changes in Their Manufacturing Process  
 
 
 
 
This guidance represents the Food and Drug Administration's (FDA'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.  
You can use an alternative approach if the approach satisfies the requirements of the applicable statutes 
and regulations.  If you want to discuss an alternative approach, contact the FDA staff responsible for 
implementing this guidance.  If you cannot identify the appropriate FDA staff, call the appropriate 
number listed on the title page of this guidance.  
 
 
 
I.  INTRODUCTION (1) 2 
 
 A.  Objectives of the Guidance (1.1) 
 
The objective of this document is to provide principles for assessing the comparability of 
biotechnological/biological products before and after changes are made in the manufacturing 
process for the drug substance or drug product.  Therefore, this guidance is intended to assist 
manufacturers of biotechnological/biological products in the collection of relevant technical 
information that serves as evidence that the manufacturing process changes will not have an 
adverse impact on the quality, safety, and efficacy of the drug product.  The document does not 
prescribe any particular analytical, nonclinical, or clinical strategy. The main emphasis of the 
document is on quality aspects. 
 
FDA's guidance documents, including this guidance, do not establish legally enforceable 
responsibilities.  Instead, guidances describe the Agency's current thinking on a topic and should 
be viewed only as recommendations, unless specific regulatory or statutory requirements are 
cited.  The use of the word should in Agency guidances means that something is suggested or 
recommended, but not required. 
                                                 
1  This guidance was developed within the Expert Working Group (Quality) of 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 Steering Committee at Step 4 of the ICH process, November 2004.  At Step 4 of the process, 
the final draft is recommended for adoption to the regulatory bodies of the European Union, Japan, and the United 
States. 
2  Arabic numbers reflect the organizational breakdown in the document endorsed by the ICH Steering Committee 
at Step 4 of the ICH process, November 2004.  
 
  1 Contains Nonbinding Recommendations 
 
B.  Background (1.2) 
 
Manufacturers3 of biotechnological/biological products frequently make changes to 
manufacturing processes4 of products5 both during development and after approval.  Reasons for 
such changes include improving the manufacturing process, increasing scale, improving product 
stability, and complying with changes in regulatory requirements.  When changes are made to 
the manufacturing process, the manufacturer generally evaluates the relevant quality attributes of 
the product to demonstrate that modifications did not occur that would adversely impact6 the 
safety and efficacy of the drug product.  Such an evaluation should indicate whether or not 
confirmatory nonclinical or clinical studies are appropriate. 
While ICH documents have not specifically addressed considerations for demonstrating 
comparability between prechange and postchange product, several ICH documents have 
provided guidance for technical information and data to be submitted in marketing applications 
that can also be useful for assessing manufacturing process changes (see section IV (4.0)  
References).  This document builds upon the previous ICH guidances and provides additional 
direction regarding approaches to: 
  Comparing postchange product to prechange product following manufacturing 
process changes; and  
  Assessing the impact of observed differences in the quality attributes caused by 
the manufacturing process change for a given product as it relates to safety and 
efficacy of the product.  
 
C.  Scope (1.3) 
 
The principles adopted and explained in this document7 apply to: 
  Proteins and polypeptides, their derivatives, and products of which they are 
components, e.g., conjugates.  These proteins and polypeptides are produced from 
recombinant or non-recombinant cell-culture expression systems and can be 
                                                 
3   For convenience, when the term manufacturer is used, it is intended to include any third party having a 
contractual arrangement to produce the intermediates, drug substance, or drug product on behalf of the marketing 
authorization holder (or the developer, if prior to market authorization). 
 
4   For convenience, when the term manufacturing process(es) is used, it also includes facilities and equipment that 
might impact on critical processing parameters and, thereby, on product quality. 
 
5   For convenience, when the term product is used without modifiers, it is intended to refer to the intermediates, 
drug substance, and drug product. 
 
6  Improvement of product quality is always desirable and encouraged.  If the results of the comparability exercise 
indicate an improved quality suggesting a significant benefit in efficacy and/or safety, the pre- and postchange 
product may not be comparable.  However, this result could be considered acceptable.  The manufacturer is advised 
to consult the appropriate regional regulatory authority. 
 
7  This document applies to situations in which all three of the bulleted conditions are present. 
 
  2 Contains Nonbinding Recommendations 
 
highly purified and characterized using an appropriate set of analytical 
procedures; 
  Products where manufacturing process changes are made by a single 
manufacturer, including those made by a contract manufacturer, who can directly 
compare results from the analysis of prechange and postchange product; and  
  Products where manufacturing process changes are made in development or for 
which a marketing authorization has been granted. 
The principles outlined in this document might also apply to other product types, such as proteins 
and polypeptides isolated from tissues and body fluids.  Manufacturers are advised to consult 
with the appropriate regional regulatory authority to determine applicability. 
 
D.  General Principles (1.4) 
 
The goal of the comparability exercise is to ensure the quality, safety, and efficacy of drug 
product produced by a changed manufacturing process through collection and evaluation of the 
relevant data to determine whether there might be any adverse impact on the drug product due to 
the manufacturing process changes.   
The demonstration of comparability does not necessarily mean that the quality attributes of the 
prechange and postchange product are identical, but that they are highly similar and that the 
existing knowledge is sufficiently predictive to ensure that any differences in quality attributes 
have no adverse impact upon safety or efficacy of the drug product.   
A determination of comparability can be based on a combination of analytical testing, biological 
assays, and, in some cases, nonclinical and clinical data.  If a manufacturer can provide 
assurance of comparability through analytical studies alone, nonclinical or clinical studies with 
the postchange product are not warranted.  However, where the relationship between specific 
quality attributes and safety and efficacy has not been established, and differences between 
quality attributes of the pre- and postchange product are observed, it might be appropriate to 
include a combination of quality, nonclinical, and/or clinical studies in the comparability 
exercise. 
To identify the impact of a manufacturing process change, a careful evaluation of all foreseeable 
consequences for the product should be performed. In consideration of this evaluation, 
appropriate criteria to define highly similar postchange product can be established.  Generally, 
quality data on the pre- and postchange product are generated, and a comparison is performed 
that integrates and evaluates all data collected, e.g., routine batch analyses, in-process control, 
process validation and/or evaluation data, characterization and stability, if appropriate.  The 
comparison of the results to the predefined criteria should allow an objective assessment of 
whether or not the pre- and postchange product are comparable.   
Following the evaluation of the quality attributes, the manufacturer could be faced with one of 
several outcomes, including:  
  Based on appropriate comparison of relevant quality attributes, pre- and postchange 
product are highly similar and considered comparable, i.e., no adverse impact on 
safety or efficacy profiles is foreseen.  
  3 Contains Nonbinding Recommendations 
 
  Although the pre- and postchange product appear highly similar, the analytical 
procedures used are not sufficient to discern relevant differences that can impact the 
safety and efficacy of the product. The manufacturer should consider employing 
additional testing (e.g., further characterization) or nonclinical and/or clinical studies 
to reach a definitive conclusion.  
  Although the pre- and postchange product appear highly similar, some differences 
have been observed in the quality attributes of the prechange and postchange product; 
but it can be justified that no adverse impact on safety or efficacy profiles is expected, 
based on the manufacturers accumulated experience, relevant information, and data.  
In these circumstances, pre- and postchange product can be considered comparable. 
  Although the pre- and postchange product appear highly similar, some differences 
have been identified in the comparison of quality attributes and a possible adverse 
impact on safety and efficacy profiles cannot be excluded. In such situations, the 
generation and analysis of additional data on quality attributes are unlikely to assist in 
determining whether pre- and postchange product are comparable.  The manufacturer 
should consider performing nonclinical and/or clinical studies.  
  Differences in the quality attributes are so significant that it is determined that the 
products are not highly similar and are therefore not comparable.  This outcome is not 
within the scope of this document and is not discussed further. 
 
II.  GUIDANCE (2) 
 
A.  Considerations for the Comparability Exercise (2.1) 
 
The goal of the comparability exercise is to ascertain that pre- and postchange drug product are 
comparable in terms of quality, safety, and efficacy.  To meet this goal, the product should be 
evaluated at the process step most appropriate to detect a change in the quality attributes.  This 
may entail evaluating the product at multiple stages of manufacture.  For example, even though 
all process changes occurred in the manufacture of the drug substance, in cases where the drug 
product could be impacted by the change, it might be appropriate to collect data on both the drug 
substance and the drug product to support the determination of comparability.  Comparability 
can often be deduced from quality studies alone (limited or comprehensive analysis, as 
appropriate), but might sometimes need to be supported by comparability bridging studies.  The 
extent of the studies necessary to demonstrate comparability will depend on: 
  The production step where the changes are introduced; 
  The potential impact of the changes on the purity as well as on the 
physicochemical and biological properties of the product, particularly considering 
the complexity and degree of knowledge of the product (e.g., impurities, product- 
related substances); 
  The availability of suitable analytical techniques to detect potential product 
modifications and the results of these studies; and  
  The relationship between quality attributes and safety and efficacy, based on 
overall nonclinical and clinical experience. 
  4 Contains Nonbinding Recommendations 
 
When considering the comparability of products, the manufacturer should evaluate, for example: 
  Relevant physicochemical and biological characterization data regarding quality 
attributes;  
  Results from analysis of relevant samples from the appropriate stages of the 
manufacturing process (e.g., intermediate, drug substance, and drug product);  
  The need for stability data, including those generated from accelerated or stress 
conditions, to provide insight into potential product differences in the degradation 
pathways of the product and, hence, potential differences in product-related 
substances and product-related impurities;  
  Batches used for demonstration of manufacturing consistency;   
  Historical data that provide insight into potential drift of quality attributes with 
respect to safety and efficacy, following either a single or a series of 
manufacturing process changes.  That is, the manufacturer should consider the 
impact of changes over time to confirm that an unacceptable impact on safety and 
efficacy profiles has not occurred. 
In addition to evaluating the data, manufacturers should also consider: 
  Critical control points in the manufacturing process that affect product 
characteristics, e.g., the impact of the process change on the quality of  in-process 
materials, as well as the ability of downstream steps to accommodate material 
from a changed cell culture process;  
  Adequacy of the in-process controls including critical control points and in-
process testing:  In-process controls for the postchange process should be 
confirmed, modified, or created, as appropriate, to maintain the quality of the 
product;  
  Nonclinical or clinical characteristics of the drug product and its therapeutic 
indications (see section II.E (2.5) of this guidance.  
 
B.  Quality Considerations (2.2) 
 
1.  Analytical Techniques (2.2.1) 
 
The battery of tests for the comparability exercise should be carefully selected and optimized to 
maximize the potential for detecting relevant differences in the quality attributes of the product 
that might result from the proposed manufacturing process change.  To address the full range of 
physicochemical properties or biological activities, it might be appropriate to apply more than 
one analytical procedure to evaluate the same quality attribute (e.g., molecular weight, 
impurities, secondary/tertiary structures).  In such cases, each method should employ different 
physicochemical or biological principles to collect data for the same parameter to maximize the 
possibility that differences in the product caused by a change in the manufacturing process might 
be detected.   
 
  5 Contains Nonbinding Recommendations 
 
It can be difficult to ensure that the chosen set of analytical procedures for the prechange product 
will be able to detect modifications of the product due to (1) the limitations of the assays (e.g., 
precision, specificity, and detection limit) and (2) the complexity of some products due to 
molecular heterogeneity.  Consequently, the manufacturer should determine: 
 
  Whether or not existing tests remain appropriate for their intended use or should 
be modified.  For example, when the manufacturing process change gives rise to a 
different impurity profile in the host cell proteins, manufacturers should confirm 
that the test used to quantitate these impurities is still suitable for its intended 
purpose.  It might be appropriate to modify the existing test to detect the new 
impurities;  
  The need to add new tests as a result of changes in quality attributes that the 
existing methods are not capable of measuring.  That is, when specific changes in 
quality attributes are expected as a result of a process change (e.g., following 
addition of a new raw material or modification of a chromatographic purification 
step), it might be appropriate to develop new analytical procedures, i.e., to employ 
additional analytical techniques above and beyond those used previously for 
characterization or routine testing. 
The measurement of quality attributes in characterization studies does not necessarily entail the 
use of validated assays, but the assays should be scientifically sound and provide results that are 
reliable. Those methods used to measure quality attributes for batch release should be validated 
in accordance with ICH guidances (ICH Q2A, Q2B, Q5C, Q6B), as appropriate.   
 
2.  Characterization  (2.2.2) 
 
Characterization of a biotechnological/biological product by appropriate techniques, as described 
in ICH Q6B, includes the determination of physicochemical properties, biological activity, 
immunochemical properties (if any), purity, impurities, contaminants, and quantity.   
 
When a manufacturing process change has been made that has the potential to have an impact on 
quality attributes, a complete or limited (but rationalized) repetition of the characterization 
activity conducted for the market application is generally warranted to directly compare the 
prechange and postchange product.  However, additional characterization might be indicated in 
some cases.  For example, when process changes result in a product characterization profile that 
differs from that observed in the material used during nonclinical and clinical studies or other 
appropriate representative materials (e.g., reference materials, marketed batches), the 
significance of these alterations should be evaluated.  Results of comprehensive characterization 
of the material used in pivotal clinical trials could provide a useful point of reference for 
subsequent comparability exercises. 
 
Each of the following criteria should be considered as a key point in the conduct of the 
comparability exercise: 
 
  Physicochemical Properties 
 
  6 Contains Nonbinding Recommendations 
 
The manufacturer should consider the concept of the desired product (and its variants) as defined 
in ICH Q6B when designing and conducting a comparability exercise.  The complexity of the 
molecular entity with respect to the degree of molecular heterogeneity should also be considered. 
Following a manufacturing process change, manufacturers should attempt to determine that 
higher order structure (secondary, tertiary, and quaternary structure) is maintained in the product.  
If the appropriate higher order structural information cannot be obtained, a relevant biological 
activity assay (see biological activity below) could indicate a correct conformational structure. 
  
  Biological Activity  
 
Biological assay results can serve multiple purposes in the confirmation of product quality 
attributes that are useful for characterization and batch analysis, and, in some cases, could serve 
as a link to clinical activity.  The manufacturer should consider the limitations of biological 
assays, such as high variability, that might prevent detection of differences that occur as a result 
of a manufacturing process change.   
 
In cases where the biological assay also serves as a complement to physicochemical analysis 
(e.g., as a surrogate assay for higher order structure), the use of a relevant biological assay with 
appropriate precision and accuracy might provide a suitable approach to confirm that change in 
specific higher order structure has not occurred following manufacturing process changes.  
Where physicochemical or biological assays are not considered adequate to confirm that the 
higher order structure is maintained, it might be appropriate to conduct a nonclinical or clinical 
study. 
 
When changes are made to a product with multiple biological activities, manufacturers should 
consider performing a set of relevant functional assays designed to evaluate the range of 
activities.  For example, certain proteins possess multiple functional domains that express 
enzymatic and receptor mediated activities. In such situations, manufacturers should consider 
evaluating all relevant functional activities.  
 
Where one or more of the multiple activities are not sufficiently correlated with clinical safety or 
efficacy or if the mechanism of action is not understood, the manufacturer should justify that 
nonclinical or clinical activity is not compromised in the postchange product. 
 
  Immunochemical Properties   
 
When immunochemical properties are part of the characterization (e.g., for antibodies or 
antibody-based products), the manufacturer should confirm that postchange product is 
comparable in terms of the specific properties. 
  7 Contains Nonbinding Recommendations 
 
 
  Purity, Impurities, and Contaminants   
 
The combination of analytical procedures selected should provide data to evaluate whether a 
change in purity profile has occurred in terms of the desired product.   
 
If differences are observed in the purity and impurity profiles of the postchange product relative 
to the prechange product, the differences should be evaluated to assess their potential impact on 
safety and efficacy.  Where the change results in the appearance of new impurities, the new 
impurities should be identified and characterized when possible.  Depending on the impurity type 
and amount, it might be appropriate to conduct nonclinical or clinical studies to confirm that 
there is no adverse impact on safety or efficacy of the drug product.   
 
Contaminants should be strictly avoided and/or suitably controlled with appropriate in-process 
acceptance criteria or action limits for drug substance or drug product.  New contaminants 
should be evaluated to assess their potential impact on the quality, safety and efficacy of the 
product. 
 
3.  Specifications (2.2.3) 
 
The tests and analytical procedures chosen to define drug substance or drug product 
specifications alone are generally not considered adequate to assess the impact of manufacturing 
process changes since they are chosen to confirm the routine quality of the product rather than to 
fully characterize it.  The manufacturer should confirm that the specifications after the process 
change are appropriate to ensure product quality. Results within the established acceptance 
criteria, but outside historical manufacturing control trends, might suggest product differences 
that warrant additional study or analysis.  Modification, elimination, or addition of a test (i.e., in 
the specification) might be indicated where data suggest that the previous test is no longer 
relevant for routine batch analysis of the postchange product.  For example, the elimination of 
bovine serum from the cell culture process would remove the need for related analyses.  
However, a widening of the acceptance criteria is generally not considered appropriate unless 
justified.  In some cases, additional tests and acceptance criteria on the relative amount of 
specific new impurities might be appropriate if the impurity profile is different following the 
manufacturing process changes.  When evaluating both the test methods and acceptance criteria 
for the postchange product, it is important to consider the general principles for setting 
specifications as defined in Q6B, i.e., the impact of the changes on the validated manufacturing 
process, characterization studies, batch analysis data, stability data, and nonclinical and clinical 
experience.   
4.  Stability (2.2.4) 
 
For certain manufacturing process changes, even slight modifications of the production 
procedures might cause changes in the stability of the postchange product.  Any change with the 
potential to alter protein structure or purity and impurity profiles should be evaluated for its 
impact on stability, since proteins are frequently sensitive to changes, such as those made to 
buffer composition, processing and holding conditions, and the use of organic solvents.  
Furthermore, stability studies might be able to detect subtle differences that are not readily 
  8 Contains Nonbinding Recommendations 
 
detectable by the characterization studies.  For example, the presence of trace amounts of a 
protease might only be detected by product degradation that occurs over an extended time 
period; or, in some cases, divalent ions leached from the container closure system might change 
the stability profile because of the activation of trace proteases not detected in stability studies of 
the prechange product. Therefore, real-time/real temperature stability studies on the product 
potentially affected by the change should be initiated, as appropriate. 
Accelerated and stress stability studies are often useful tools to establish degradation profiles and 
provide a further direct comparison of prechange and postchange product.  The results thus 
obtained might show product differences that warrant additional evaluation and also identify 
conditions indicating that additional controls should be employed in the manufacturing process 
and during storage to eliminate these unexpected differences.  Appropriate studies should be 
considered to confirm that suitable storage conditions and controls are selected.  
ICH Q5C and Q1A(R) should be consulted to determine the conditions for stability studies that 
provide relevant data to be compared before and after a change. 
 
C.  Manufacturing Process Considerations (2.3) 
 
A well-defined manufacturing process with its associated process controls ensures that 
acceptable product is produced on a consistent basis.  Approaches to determining the impact of 
any process change will vary with respect to the specific process, the product, the extent of the 
manufacturers knowledge of and experience with the process, and development data generated.  
The manufacturer should confirm that the process controls in the modified process provide at 
least similar or more effective control of the product quality, compared to those of the original 
process.    
A careful consideration of potential effects of the planned change on steps downstream and 
quality parameters related to these steps is extremely important (e.g., for acceptance criteria, in-
process specification, in-process tests, in-process hold times, operating limits, and 
validation/evaluation, if appropriate).  This analysis will help identify which tests should be 
performed during the comparability exercise, which in-process or batch release acceptance 
criteria or analytical procedures should be reevaluated, and which steps should not be impacted 
by the proposed change.  For example, analysis of intermediates might suggest potential 
differences that should be evaluated to determine the suitability of existing tests to detect these 
differences in the product.  The rationale for excluding parts of the process from this 
consideration should be justified.  
While the process will change and the associated controls might be redefined, the manufacturer 
should confirm that prechange and postchange product are comparable.  To support the 
comparison, it is often useful to demonstrate, for example, that specific intermediates are 
comparable or that the modified process has the capability to provide appropriate levels of 
removal for process- and product-related impurities, including those newly introduced by the 
process change.  To support process changes for approved products, data from commercial-scale 
batches are generally indicated. 
The process assessment should consider such factors as the criticality of the process step and 
proposed change, the location of the change and potential for effects on other process steps, and 
  9 Contains Nonbinding Recommendations 
 
the type and extent of change.  Information that can aid this assessment is generally available 
from several sources.  The sources can include knowledge from process development studies, 
small scale evaluation/validation studies, experience with earlier process changes, experience 
with equipment in similar operations, changes in similar manufacturing processes with similar 
products, and literature.  Although information from external sources is useful to some extent, it 
is within the context of the specific manufacturing process and specific product that the change 
should be assessed. 
When changes are made to a process, the manufacturer should demonstrate that the associated 
process controls, including any new ones, provide assurance that the modified process will also 
be capable of providing comparable product.  The modified process steps should be reevaluated 
and/or revalidated, as appropriate.  The in-process controls, including critical control points and 
in-process testing, should ensure that the postchange process is well controlled and maintains the 
quality of the product.  Typically, reevaluation/revalidation activities for a simple change might 
be limited to the affected process step if there is no evidence to indicate that there is an impact on 
the performance of subsequent (downstream) process steps or on the quality of the intermediates 
resulting from the subsequent steps.  When the change considered affects more than a single 
step, more extensive analysis of the change and resultant validation might be appropriate.   
Demonstration of state of control with the modified/changed manufacturing process might 
include, but is not limited to, such items as: 
  Establishment of modified specifications for raw, source and starting materials, 
and reagents; 
  Appropriate bioburden and/or viral safety testing of the postchange cell banks and 
cells at the limit of in vitro cell age for production;  
  Adventitious agent clearance;  
  Removal of product- or process-related impurities, such as residual host cell DNA 
and proteins; and  
  Maintenance of the purity level. 
For approved products, an appropriate number of postchange batches should be analyzed to 
demonstrate consistent performance of the process. 
To support the analysis of the changes and the control strategy, the manufacturer should prepare 
a description of the change that summarizes the prechange and the postchange manufacturing 
process and that clearly highlights modifications of the process and changes in controls in a side-
by-side format. 
 
D.  Demonstration of Comparability During Development (2.4) 
 
During product development, it is expected that multiple changes in the manufacturing process 
will occur that could impact drug product quality, safety, and efficacy.  Comparability exercises 
are generally performed to demonstrate that nonclinical and clinical data generated with 
prechange product are applicable to postchange product in order to facilitate further development 
and, ultimately, to support the marketing authorization.  Comparability studies conducted for 
  10 Contains Nonbinding Recommendations 
 
products in development are influenced by factors such as the stage of product development, the 
availability of validated analytical procedures, and the extent of product and process knowledge, 
which are limited at times due to the available experience that the manufacturer has with the 
process.   
Where changes are introduced in development before nonclinical studies, the issue of assessing 
comparability is not generally raised because the manufacturer subsequently conducts 
nonclinical and clinical studies using the postchange product as part of the development process.  
During early phases of nonclinical and clinical studies, comparability testing is generally not as 
extensive as for an approved product.  As knowledge and information accumulate, and the 
analytical tools develop, the comparability exercise should utilize available information and will 
generally become more comprehensive. Where process changes are introduced in late stages of 
development and no additional clinical studies are planned to support the marketing 
authorization, the comparability exercise should be as comprehensive and thorough as one 
conducted for an approved product.  Some outcomes of the comparability studies on quality 
attributes can lead to additional nonclinical or clinical studies. 
 
In order for a comparability exercise to occur during development, appropriate assessment tools 
should be used.  Analytical procedures used during development might not be validated, but 
should always be scientifically sound and provide results that are reliable and reproducible.  Due 
to the limitations of the analytical tools in early clinical development, physicochemical and 
biological tests alone might be considered inadequate to determine comparability; therefore, 
bridging nonclinical and/or clinical studies, as appropriate, might be needed.  
E.  Nonclinical and Clinical Considerations (2.5) 
 
1.  Factors To Be Considered in Planning Nonclinical and Clinical Studies (2.5.1) 
 
Determinations of product comparability can be based solely on quality considerations (see 
section 2.2) if the manufacturer can provide assurance of comparability through analytical 
studies as suggested in this document.  Additional evidence from nonclinical or clinical studies is 
considered appropriate when quality data are insufficient to establish comparability. The extent 
and nature of nonclinical and clinical studies will be determined on a case-by-case basis in 
consideration of various factors, which include among others:  
 Quality findings  
  Drug product  The type, nature, and extent of differences between the 
postchange product and the prechange product with respect to quality attributes 
including product-related substances, the impurity profile, stability, and 
excipients.  
For example, new impurities could warrant toxicological studies for qualification; 
  Results of the evaluation/validation studies on the new process including the 
results of relevant in-process tests; 
  Availability, capabilities, and limitations of tests used for any comparability 
studies. 
  11 Contains Nonbinding Recommendations 
 
The nature and the level of knowledge of the product 
  Product complexity, including heterogeneity and higher order structure  
Physicochemical and in vitro biological assays might not be able to detect all 
differences in structure and/or function; 
  Structure-activity relationship and strength of the association of quality attributes 
with safety and efficacy; 
  Relationship between the therapeutic protein and endogenous proteins and the 
consequences for immunogenicity; 
  Mode(s) of action (unknown vs. known, single vs. multiple active sites). 
Existing nonclinical and clinical data relevant to the product, aspects of product 
use, and product class 
  Therapeutic indications/target patient groups  The impact of possible 
differences can vary between patient groups, e.g., risk for unintended 
immunogenicity. It may be appropriate to consider the consequences  separately 
for each indication; 
  Posology, e.g., dosing regimen, route of administration  The risk of certain 
possible consequences of a difference, such as immunogenicity, could be higher 
with chronic administration as compared to short-term administration; 
subcutaneous administration might induce immunogenicity more often than 
intravenous administration;  
  The therapeutic window/dose-response curve  The impact of a certain change 
could be different for products that have a wide therapeutic window as compared 
to those with a more narrow window. The safety or efficacy of products with a 
steep or a bell-shaped dose-response curve can be affected by minor changes in 
pharmacokinetics or receptor-binding;   
  Previous experience, e.g., immunogenicity, safety  The experience with the 
original product or with other products in the same class can be relevant, 
especially with regard to rare adverse effects, e.g., knowledge about the 
consequences of immunogenicity; 
  Pharmacokinetic (PK)/pharmacodynamic (PD) relation, distribution, clearance. 
 
2.  Type of Studies (2.5.2) 
 
The nonclinical and clinical studies referred to in this document might include, depending on the 
situation, PK studies, PD studies, PK/PD studies, clinical efficacy studies, specific safety studies, 
immunogenicity studies, and pharmacovigilance studies. The purpose of these studies is to 
enable comparison of pre- and postchange product. Where appropriate, these studies should be 
direct comparative studies. 
 
  12 Contains Nonbinding Recommendations 
 
GLOSSARY (3) 
 
Comparability Bridging Study:  A study performed to provide nonclinical or clinical data that 
allows extrapolation of the existing data from the drug product produced by the current process 
to the drug product from the changed process. 
 
Comparable:  A conclusion that products have highly similar quality attributes before and after 
manufacturing process changes and that no adverse impact on the safety or efficacy, including 
immunogenicity, of the drug product occurred. This conclusion can be based on an analysis of 
product quality attributes.  In some cases, nonclinical or clinical data might contribute to the 
conclusion. 
 
Comparability Exercise:  The activities, including study design, conduct of studies, and 
evaluation of data, that are designed to investigate whether the products are comparable. 
 
Quality Attribute:  A molecular or product characteristic that is selected for its ability to help 
indicate the quality of the product.  Collectively, the quality attributes define identity, purity, 
potency, and stability of the product, and safety with respect to adventitious agents.  
Specifications measure a selected subset of the quality attributes. 
  13 Contains Nonbinding Recommendations 
 
 
 
REFERENCES (4) 
 
Viral Safety Evaluation of Biotechnology Products Derived From Cell Lines of Human or 
Animal Origin (Q5A). 
Quality of Biotechnological Products:  Analysis of the Expression Construct in Cells Used for 
Production of r-DNA Derived Protein Products (Q5B).  
Quality of Biotechnological Products:  Stability Testing of Biotechnological/Biological Products 
(Q5C). 
Quality of Biotechnological Products:  Derivation and Characterization of Cell Substrates Used 
for Production of Biotechnological/Biological Products (Q5D). 
Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological 
Products (Q6B). 
Good Manufacturing Practice Guidance for Active Pharmaceutical Ingredients (Q7A). 
Text on Validation of Analytical Procedures (Q2A).  
Validation of Analytical Procedures: Methodology (Q2B). 
Common Technical Document for the Registration of Pharmaceuticals for Human Use (M4Q).  
Stability Testing of New Drug Substances and Products (Q1AR). 
Preclinical Safety Evaluation of Biotechnology-Derived Pharmaceuticals (S6). 
Statistical Principles for Clinical Trials (E9). 
Choice of Control Group and Related Issues in Clinical Trials (E10). 
 
  
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