169 
 
Guidance for Industry 
 
Drug Substance Chemistry, Manufacturing,  
and Controls Information 
 
 
 
Submit comments on this guidance at any time.  Submit written comments to the Division of 
Dockets Management (HFA-305), Food and Drug Administration, 5630 Fishers Lane, Room 
1061, Rockville, MD 20852.  Comments may also be submitted electronically on the Internet at 
http://www.regulations.gov.  All written comments should be identified with the Docket No.  
FDA-2003-D-0243 (formerly 2003D-0571). 
For  further  information  regarding  this  document,  contact  Alem  Ghiorghis,  Center  for 
Veterinary  Medicine  (HFV-143),  Food  and  Drug  Administration,  7500  Standish  Place, 
Rockville, MD 20855, (240) 276-8266, E-mail: alem.ghiorghis@fda.hhs.gov. 
Additional copies of this guidance document may be requested from the Communications Staff 
(HFV-12), Center for Veterinary Medicine, Food and Drug Administration, 7519 Standish 
Place, Rockville, MD 20855, and may be viewed on the Internet at either 
http://www.fda.gov/AnimalVeterinary/default.htm or http://www.regulations.gov.   
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Veterinary Medicine (CVM) 
August 6, 2010 Contains Nonbinding Recommendations 
 
 
 
TABLE OF CONTENTS1 
 
 
I.  INTRODUCTION.............................................................................................................1 
II.  BACKGROUND................................................................................................................3 
A.  The Common Technical Document  Quality (CTD-Q) Format.............................................3 
B.  Content of an Application..............................................................................................................4 
C.  Additional Guidance......................................................................................................................4 
D.  References to Other Applications or Master Files (MFs)...........................................................4 
1. Other Applications...........................................................................................................................4 
2. Master Files (MFs)...........................................................................................................................4 
III.  GENERAL INFORMATION (S.1)..................................................................................6 
A.  Nomenclature (S.1.1)......................................................................................................................7 
B.  Structure (S.1.2)..............................................................................................................................7 
C.  General Properties (S.1.3)..............................................................................................................7 
IV.  MANUFACTURE (S.2)....................................................................................................8 
A.  Manufacturers (S.2.1)....................................................................................................................8 
B.  Description of Manufacturing Process and Process Controls (S.2.2)........................................9 
1. Flow Diagram..................................................................................................................................9 
2. Description of the Manufacturing Process and Process Controls.................................................10 
3. Reprocessing, Reworking, Recycling, Regeneration, and Other Operations.................................13 
C.  Control of Materials (S.2.3).........................................................................................................16 
1.  Starting Materials.........................................................................................................................16 
2. Reagents, Solvents, and Auxiliary Materials..................................................................................17 
3. Diluents..........................................................................................................................................18 
D.  Controls of Critical Steps and Intermediates (S.2.4).................................................................18 
E.  Process Validation and/or Evaluation (S.2.5)............................................................................20 
F.  Manufacturing Process Development (S.2.6).............................................................................21 
V.  CHARACTERIZATION (S.3).......................................................................................21 
A.  Elucidation of Structure and Other Characteristics (S.3.1).....................................................21 
1. Elucidation of Structure.................................................................................................................21 
2. Physicochemical Characterization.................................................................................................22 
3. Biological and Other Relevant Characteristics.............................................................................23 
B.  Impurities (S.3.2)..........................................................................................................................23 
VI.  CONTROL OF DRUG SUBSTANCE (S.4)..................................................................25 
                                                 
1 Alphanumeric designations in parentheses that follow headings show where information should be placed in 
applications that are submitted in Common Technical Document (CTD) format. 
  i Contains Nonbinding Recommendations 
 
 
 
A.  Specification (S.4.1)......................................................................................................................25 
B.  Analytical Procedures (S.4.2)......................................................................................................30 
C.  Validation of Analytical Procedures (S.4.3)...............................................................................31 
D.  Batch Analyses (S.4.4)..................................................................................................................31 
1. Batch Analysis Reports...................................................................................................................31 
2. Collated Batch Analyses Data........................................................................................................32 
E.  Justification of Specification (S.4.5)............................................................................................32 
VII.  REFERENCE STANDARDS OR MATERIALS (S.5)................................................35 
VIII.  CONTAINER CLOSURE SYSTEM (S.6)....................................................................35 
IX.  STABILITY (S.7)............................................................................................................35 
A.  Stability Summary and Conclusions (S.7.1)...............................................................................35 
B.  Postapproval Stability Protocol and Stability Commitment (S.7.2)........................................35 
C.  Stability Data (S.7.3)....................................................................................................................36 
1. Primary Stability Studies................................................................................................................36 
2. Supporting Stability Studies...........................................................................................................36 
3. Stress Studies..................................................................................................................................37 
X.  APPENDICES (A)...........................................................................................................37 
A.  Facilities and Equipment (A.1)....................................................................................................37 
B.  Adventitious Agents Safety Evaluation (A.2).............................................................................38 
1. Nonviral Adventitious Agents.........................................................................................................39 
2. Viral Adventitious Agents...............................................................................................................39 
XI.  REGIONAL INFORMATION (R)................................................................................40 
A.  Executed Production Records (R.1.S)........................................................................................40 
B.  Comparability Protocols (R.2.S).................................................................................................40 
C.  Methods Validation Package (R.3.S)..........................................................................................40 
XII.  LITERATURE REFERENCES (3.3)............................................................................41 
ATTACHMENT 1:......................................................................................................................42 
STARTING MATERIALS FOR SYNTHETIC DRUG SUBSTANCES...............................42 
ATTACHMENT 2:......................................................................................................................50 
STARTING MATERIALS OF PLANT OR ANIMAL ORIGIN...........................................50 
GLOSSARY.................................................................................................................................53 
  ii Contains Nonbinding Recommendations 
 
 
 
Guidance for Industry2 
 
Drug Substance 
Chemistry, Manufacturing, and Controls Information 
 
 
 
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 
 
Information on the chemistry, manufacturing, and controls (CMC) for the drug substance must 
be submitted to support the approval of original new animal drug applications (NADAs) and 
abbreviated new animal drug applications (ANADAs).3  This guidance provides 
recommendations on the CMC information for drug substances that should be submitted to 
support these applications.  The guidance is structured to facilitate the preparation of applications 
submitted in Common Technical Document (CTD) format.   
 
This guidance addresses the information to be submitted for drug substances to ensure continued 
drug substance and drug product quality (i.e., the identity, strength, quality, purity, and potency).  
This guidance provides recommendations on the information that should be included for the 
following topics:  
 
  Nomenclature, structure, and general drug substance properties 
  Manufacture 
  Characterization 
  Control of drug substance 
  Reference standards or materials 
  Container closure system 
  Stability 
 
The recommendations provided in this guidance apply to the following types of drug substances: 
 
                                                 
2 This guidance has been prepared by the Office of New Animal Drug Evaluation in the Center for Veterinary 
Medicine at the Food and Drug Administration. 
 
3 See 21 CFR 514.1(b). 
  1 Contains Nonbinding Recommendations 
 
 
 
 
  Drug substances manufactured by chemical synthesis 
  Highly purified and well-characterized drug substances derived from plants or animals 4 
  Semisynthetic drug substances manufactured by the chemical modification of a highly 
purified and well-characterized intermediate derived from plants or animals 
  The synthetic portion of the manufacturing process for semisynthetic drug substances 
manufactured by the chemical modification of an intermediate produced by conventional 
fermentation.   
 
The guidance does not provide specific recommendations relating to the following: 
 
  Monoclonal antibodies 
  Peptides 
  Oligonucleotides 
  Radiopharmaceuticals 
  Medical gases 
  Drug substances that are not well characterized (e.g., botanicals, some proteins) derived 
from plants or animals 
  Drug substances derived using transgenic technology 
  Drug substances derived directly from or manufacturing operations involving 
fermentation (conventional fermentation or using rDNA technology) or tissue or cell 
culture.   
 
More detailed guidance on the content of an application may be available in separate guidance 
documents (see section II.C).  Applicants with drug substances not specifically covered by this 
(Drug Substance guidance) or another guidance can apply the content recommendations in this 
guidance, as scientifically appropriate, and/or can contact the appropriate review teams for 
guidance. 
 
FDAs guidance documents, including this guidance, do not establish legally enforceable 
responsibilities.  Instead, guidances describe the Agencys 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. 
 
 
 
 
 
 
                                                 
4 For purposes of this guidance, drug substances derived from plants or animals does not include materials produced 
by plant cell fermentation, animal cell or tissue culture, or through use of transgenic technology (e.g., 
biotechnology-derived protein drug products). 
  2 Contains Nonbinding Recommendations 
 
 
 
II.  BACKGROUND 
 
A.  The Common Technical Document  Quality (CTD-Q) Format 
 
In November 2000, the International Conference on Harmonisation of Technical 
Requirements for Registration of Pharmaceuticals for Human Use (ICH) issued 
harmonized guidance for the format of drug product applications (i.e., Common 
Technical Document (CTD)).  The CTD describes a format for applications that 
(supplemented with regional information) can be used for submission to the regulatory 
authorities in the United States, European Union, and Japan.  One focus of this effort was 
harmonizing the format for quality information (i.e., chemistry, manufacturing, and 
controls) that will be submitted in an application.  FDAs guidance on M4Q:  The CTD  
Quality describes the format for the quality information submitted in Module 3 of an 
application and provides additional information on formatting aspects of an application.  
The information in animal drug applications is commonly presented in the order of the 
required CMC information specified under section  514.1(b)(4) and (5).  Although the 
CTD-Q format was developed for human drugs, the drug substance information to 
support NADAs and ANADAs can be formatted according to the CTD-Q format or any 
alternative format that provides the appropriate information to support the application. 
Applicants should review FDAs guidance on M4Q:  The CTD  Quality and other 
related CTD guidance documents for detailed formatting recommendations on preparing 
an application in CTD format. 
 
 
This Drug Substance guidance has been organized in a format conforming to Module 3 of 
the CTD, and it provides CMC content recommendations specific to drug substance, 
including recommendations for the Appendices, Regional Information, and Literature 
References sections.  Alphanumeric designations in parentheses corresponding to the 
CTD format follow relevant headings and text to show where information is to be placed 
in the CTD.5  Recommendations specific to drug product, including recommendations for 
the Appendices, Regional Information and Literature References sections, will be 
provided in the Drug Product guidance.  
 
  Multiple Drug Substances in an Application 
 
When an application is submitted for a drug product involving two or more drug 
substances (e.g., combination drug product, copackaged drug products), information for 
each drug substance should be presented separately in the application.  Information 
presented separately means one complete S section for one drug substance followed by 
other complete S sections for additional drug substances.  All of the information pertinent 
to each one of the drug substances (general information, manufacture, characterization, 
                                                 
5  Arabic numbers have been assigned to specific sections of the CTD.  For example, the designation 3.2 before S, P, 
A, and R indicates Module 3, Body of Data section 2.  Where this guidance discusses Module 3, Body of Data 
section 2, for brevity, the initial designation 3.2 is not repeated throughout the rest of the guidance (e.g., 3.2.S.1.3 
reads S.1.3).  
  3 Contains Nonbinding Recommendations 
 
 
 
control, standards, container closure system, and stability) should be provided in a single 
section. 
 
B.  Content of an Application 
 
The application should include information in every S subsection for each of the drug 
substances and manufacturing schemes (e.g., alternative processes, manufacturing site) 
intended for approval under the application.  Information should be provided in the 
Appendices, Regional Information, and Literature References sections for each of the 
drug substances and manufacturing schemes, as appropriate.  If an Appendices or 
Regional Information subsection or the Literature References section is not applicable, 
this should be stated in the application.  
 
C.  Additional Guidance 
 
 
This guidance references ICH guidance documents cited in the CTD-Q and FDAs 
guidances on general technical topics (i.e., stability, container closure systems, analytical 
procedures and methods validation, sterilization process validation, drug master files, and 
environmental assessments) rather than incorporating this detailed information.  These 
guidances are referenced in the text and/or listed at the end of a section.  An applicant 
should refer to these guidances for recommendations on the detailed information that 
should be included in the application to address the general technical topic.   
 
 
FDA continues to update existing and publish new guidance documents.  An applicant 
should use current guidance when preparing an NADA or ANADA submission.6  
 
D.  References to Other Applications or Master Files (MFs) 
 
1.  Other Applications 
 
CVM discourages the reference of NDAs or ANDAs for drug substance information.  In 
these instances, CVM recommends that the drug substance information be included in a 
master file or incorporated in the applicants NADA or ANADA.  Copies of letters of 
authorization (LOAs) should be submitted in the appropriate section of an NADA or 
ANADA. 
 
2.  Master Files (MFs) 
 
This guidance describes chemistry, manufacturing, and controls information for drug 
substances that should be submitted to the Agency as part of the process of seeking the 
approval of an NADA or ANADA. When a drug substance is manufactured by a firm 
                                                 
6
Current guidance documents are available on the Internet 
http://www.fda.gov/AnimalVeterinary/GuidanceComplianceEnforcement/GuidanceforIndustry/default.htm.  
  4 Contains Nonbinding Recommendations 
 
 
 
other than the applicant, much of this information is frequently provided by reference to 
one or more Type II MFs rather than directly in an application.  The CMC information in 
a Type II MF can be organized in CTD-Q format.  Under FDA's regulations, an 
application can incorporate by reference all or part of the contents of any MF to address 
particular drug substance issues if the MF holder provides written authorization (i.e., 
LOA) to the applicant and the authorization is included in the application (in the 
appropriate section of an NADA or ANADA).  The authorization must specifically 
identify the material being incorporated by reference (514.1(a)).  The incorporated 
material should be identified by name, reference number, volume and page number of the 
MF, and date of submission.  See the guidance Preparation and Submission of Veterinary 
Master Files for more information.   
 
Both the applicant and the drug substance manufacturer (MF holder) contribute to 
establishing and maintaining the identity, strength, quality, purity, and potency of the 
applicant's drug products by manufacturing and controlling the drug substance in 
accordance with the information submitted in the application and, by reference, in the 
MF.  The following recommendations pertain to location of information in the MF and/or 
application when an applicant and Type II MF holder are different firms. 
 
  General Information (S.17):  Both the MF and the application should include this 
information.  These sections should contain similar, though not necessarily identical, 
information.  For example, if an applicant performed screening studies and 
established the existence of multiple polymorphs, information concerning these 
polymorphs might be present in the application but not in the MF. 
 
  Manufacture (S.2):  The application should identify in S.2.1 the manufacturers of 
each drug substance with appropriate administrative information (see section IV.A).  
The MF should include this information for its manufacturing operations and any 
contract facilities that are used (e.g., intermediate manufacturers, laboratories).  In 
general, a MF can be referenced for the information recommended in S.2.2 through 
S.2.6.  However, the information should be augmented by the applicant, as 
appropriate.  For example, if the applicant micronizes drug substance purchased from 
a MF holder the information on the micronization process should be included in the 
application. 
 
  Characterization (S.3):  In general, a MF can be referenced for this information.  
However, the information should be augmented by the applicant, as appropriate.  For 
example, characterization information on physical properties critical to the applicants 
product, such as solid state form or particle size distribution, should be included in 
S.3.1 by the applicant under certain circumstances (e.g., applicant manipulates the 
physical property (micronizes), the MF holder has not characterized the physical 
property).  Furthermore, information on an applicants studies to characterize 
impurities (S.3.2) can be warranted to support the applicants drug substance controls. 
                                                 
7 Alphanumeric designations in parentheses that follow headings show where information should be placed in 
applications that are submitted in Common Technical Document (CTD) format. 
  5 Contains Nonbinding Recommendations 
 
 
 
 
  Control of Drug Substance (S.4):  In general, information recommended in S.4 
should be provided in both the MF and the application.  However, reference to a MF 
can be appropriate for some of the information in S.4.2 through S.4.5 if the MF 
holder and applicant are working together to develop the drug substance controls.  
Both the MF and the application should include a drug substance specification 
(S.4.1).  The MF could include more than one drug substance specification if the 
holder sells different technical grades of the drug substance (e.g., micronized and 
nonmicronized).  
 
  Reference Standards (S.5):  In general, information should be provided in both the 
MF and the application.  However, reference to a MF can be appropriate for some of 
the information if the MF holder and applicant are working together to develop the 
reference standard. 
 
  Container Closure System (S.6):  In general, MFs can be referenced for this 
information.  However, the information should be augmented by the applicant, as 
appropriate. 
 
  Stability (S.7):  In general, MFs can be referenced for this information.  However, 
the information should be augmented by the applicant, as appropriate.  For example, 
an applicant might perform stress studies to support the analytical procedures it used 
to control the drug substance.  
 
  Appendices (A):  In general, MFs can be referenced for this information.  However, 
the information should be augmented by the applicant, as appropriate. 
 
  Regional Information (R): Comparability protocols can be included in both the MF 
and application (R.2.S).  A methods validation package should be included in the 
application (R.3.S).  
 
  Literature References (3.3):  Both the MF and the application should include 
literature references as warranted.   
 
Type II MFs for drug substance intermediates can also be submitted in the CTD-Q 
format.  However, not all sections of the CTD-Q format would apply (e.g., S.4).  The 
CMC information provided to support an intermediate should be appropriate for the 
particular situation (e.g., process, complexity of the molecule). 
 
 
III.  GENERAL INFORMATION (S.1) 
 
General information on the nomenclature, structure, and general properties of the drug substance, 
should be provided in S.1. 
 
  6 Contains Nonbinding Recommendations 
 
 
 
A.  Nomenclature (S.1.1) 
 
All appropriate names or designations for the drug substance should be provided in S.1.1. 
Any codes, abbreviations, or nicknames used in the application to identify the drug 
substance should also be listed, including the following, if they exist or have been 
proposed.  A name that has not yet been finalized should be identified as proposed in the 
list.   
 
  United States Adopted Name (USAN) 
  Compendial name8   
  Chemical names (e.g., Chemical Abstracts Service (CAS), International Union of 
Pure and Applied Chemistry (IUPAC)) 
  Company names or laboratory codes 
  Other nonproprietary names (e.g.,  International Nonproprietary Name (INN), 
British Approved Name (BAN), Japanese Accepted Name (JAN))  
  Chemical Abstracts Service (CAS) Registry Number 
 
B.  Structure (S.1.2) 
 
Information on the chemical structure of the drug substance should be provided in S.1.2.  
This information should include: 
 
  one or more drawings to show the overall chemical structure of the drug substance, 
including stereochemistry  
  molecular formula 
  molecular weight  
 
For a naturally derived protein drug substance, the information should include: 
 
  the schematic amino acid sequence indicating glycosylation sites or other 
posttranslational modifications  
  a general description of the molecule (e.g., shape, disulfide bonds, subunit 
composition) 
  number of amino acid residues  
  molecular weight 
 
C.  General Properties (S.1.3) 
 
A list should be provided of the general physicochemical properties of the drug 
substance.  Other relevant properties of the drug substance should also be listed.  
Relevant properties are those physical, chemical, biological and microbiological 
attributes relating to the identity, strength, quality, purity, and/or potency of the drug 
                                                 
8 A compendial name is a name that appears in an official compendium as defined in the Federal Food, Drug, and 
Cosmetic Act (e.g., United States Pharmacopeia (USP)) ( 201(j) (21 U.S.C. 32(i)). 
  7 Contains Nonbinding Recommendations 
 
 
 
substance and, as appropriate, drug product.  The information should include, as 
appropriate: 
 
  A general description (e.g., appearance, color, physical state) 
  Melting or boiling points 
  Optical rotation 
  Solubility profile (aqueous and nonaqueous, as applicable) 
  Solution pH 
  Partition coefficients 
  Dissociation constants 
  Identification of the physical form (e.g., polymorph, solvate, or hydrate) that will be 
used in the manufacture of the drug product 
  Biological activities 
 
For a naturally derived protein drug substance, additional information should be included, 
such as: 
 
  Isoelectric point 
  Extinction coefficient 
  Any unique spectral characteristics  
 
If the drug substance can exist in more than one physical form, the information included 
in S.1.3 should be for the form (or forms) of the drug substance that will be used in the 
manufacture of the drug product.  Detailed information on the characterization (e.g., X-
ray powder diffraction data, thermal analysis curves) of these and other physical forms 
and conditions required to produce one form or another should be provided in S.3.1. 
 
 
IV.  MANUFACTURE (S.2) 
 
Information concerning the manufacture of the drug substance, as described below, should be 
provided in S.2. 
 
A.  Manufacturers (S.2.1) 
 
The name, address, and manufacturing responsibility should be provided for each firm 
(including contract manufacturers and testing laboratories) and each site (i.e., facility) 
that will be involved in the manufacturing or testing of the drug substance.  Each site 
should be identified by the street address, city, state, and, when available, the drug 
establishment registration number.9  The addresses should be for the location where the 
relevant manufacturing or testing operation will be performed.  Addresses for corporate 
headquarters or offices need not be provided.  Building numbers or other specific 
                                                 
9 See 21 CFR part 207 for registration requirements for producers of drugs.  The registration number is the seven- 
digit central file number (CFN) or ten-digit FDA Establishment Identifier (FEI). 
  8 Contains Nonbinding Recommendations 
 
 
 
identifying information should be provided for multifacility campuses.  For sites 
processing sterile drug substances, the sterile processing area (e.g., room) should also be 
included.  Addresses for foreign sites should be provided in comparable detail, and the 
name, address, and phone number of the U.S. agent for each foreign drug establishment, 
as required under 21 CFR 207.40(c), should be included.   
 
To facilitate preapproval inspection related activities, it is recommended that the name, 
telephone number, fax number and e-mail address of a contact person be provided for 
each site listed in the application.  Facilities should be ready for inspection when the 
application is submitted to FDA. 
 
B.  Description of Manufacturing Process and Process Controls (S.2.2) 
 
The description of the drug substance manufacturing process represents the applicants 
commitment for the manufacture of the drug substance.  A flow diagram and a complete 
description of the processes and process controls that will be used to manufacture the 
drug substance or derive it from a biological source should be provided in S.2.2.  If 
alternative processes are to be used, the information should be provided for each 
alternative.  If justification for an alternative process is warranted, the information should 
be included in S.2.2 (e.g., comparative impurity data on intermediates) or can be cross- 
referenced if provided elsewhere in the application (e.g., S.4.4). 
  
1.  Flow Diagram10 
 
A flow diagram that gives the steps of the process and shows where materials enter the 
process should be provided.  The entire manufacturing process should be depicted (i.e., 
starting materials through drug substance release testing).  See Attachments 1 and 2 for 
information on starting materials.  The flow diagram can be supplemented with 
information presented in tabular form, if appropriate.  The flow diagram should include: 
 
  Each manufacturing step with identification of those steps that are critical.  These 
manufacturing steps can include reaction, workup (e.g., extraction), isolation (e.g., 
centrifugation, distillation), purification (e.g., chromatography, electrophoresis), 
processing (e.g., micronization), drug substance release testing. 
  The name or code number of the material being processed in each manufacturing 
step, as appropriate 
  Chemical structure (including stereochemical configuration where applicable) or 
biological identification of starting materials, intermediates, structurally complex 
reagents, postsynthesis materials, and the drug substance  
                                                 
10 Headings that are not followed by alphanumeric designations (i.e., non-CTD-Q headings) are included in this 
document for ease of providing recommendations on the information that should be included under a CTD-Q 
heading (in this instance Description of Manufacturing Process and Process Controls (S.2.2)).  An application 
submitted in CTD-Q format need not include these non-CTD-Q headings.  An applicant can physically or 
electronically separate information under a CTD-Q heading as it chooses.  However, once a particular approach is 
adopted, the same approach should be used throughout the life of the application. 
  9 Contains Nonbinding Recommendations 
 
 
 
  Molecular formula and molecular weight of chemical starting materials, 
intermediates, postsynthesis materials, and drug substance 
  Solvents, reagents, and auxiliary materials used in each manufacturing step 
  Critical process controls and the points at which they are conducted  
  Operating parameters (e.g., temperature, pH, pressure) for each manufacturing step  
  An indication of whether intermediates are used in situ or isolated before being used 
in the next reaction step and which intermediates are considered the final 
intermediates 
  Expected yield (percent) for each reaction step  
Reagents and other materials should not be identified using only trade (i.e., proprietary) 
names.  If a reaction results in a mixture of products (e.g., two or more isomers), each 
component of the mixture should be indicated in the flow diagram.  However, 
information on side products and impurities should be provided in S.3.2 (see sectionV.B).   
 
2.  Description of the Manufacturing Process and Process Controls 
 
A narrative description of the manufacturing process that represents the sequence of 
manufacturing steps undertaken and the scale of production should be provided.  This 
description should provide more detail than that given in the flow diagram.  The 
description should identify all process controls and the associated numeric ranges, limits, 
or acceptance criteria.  Furthermore, any process controls that are considered critical 
process controls should be highlighted.  See below for additional information on process 
controls.  The detailed description of the manufacturing process and process controls 
should include: 
 
  A detailed description of each manufacturing step  
  Starting materials or intermediate used in each step, with chemical or biological 
names and quantities specified 
  Solvents, reagents, and auxiliary materials used in each step, with chemical or 
biological names and quantities specified 
  Type of equipment (e.g., Centrifuge) used, including materials of construction when 
critical  
  Identification of the manufacturing steps that are considered critical  
  All process controls and their associated numeric ranges, limits, or acceptance 
criteria, with critical process controls highlighted  
  Type of analytical procedure (e.g., HPLC) used for each process test  
  Identification of intermediates, postsynthesis materials, and unfinished drug substance 
that are tested (details should be provided in S.2.4)  
  10 Contains Nonbinding Recommendations 
 
 
 
  Identification of manufacturing steps that involve recycling of filtrates (mother 
liquors) to recover reactants, intermediates, or drug substance, including for the 
purpose of producing or isolating additional crystals (i.e., Second crops) and the 
process controls on such operation (see section IV.B.3.c) 
  Identification of manufacturing steps that use recovered solvents or auxiliary 
materials (see section IV.B.3.c) 
  Identification of manufacturing steps that involve fraction collection (e.g., 
Chromatographic purification), the process controls on such operations, and the 
disposition of unused fractions (e.g., Recycling) 
  Identification of processes that involve combining intermediate or drug substance 
batches, drug substance and a diluent, or two or more drug substances  
  Yield ranges (weight and percent) for each manufacturing step 
 
Moreover for drug substance derived from a biological source or a semisynthetic drug 
substance, the description should include information on the processing operations 
conducted on the biological starting material and other procedures such as: 
 
  Storage and transportation conditions for biological starting materials 
  Preparation procedures (e.g., cleaning, drying) 
  Isolation processes (e.g., grinding, cell lysis, extraction from biomass) 
  Holding times and storage conditions during manufacture 
  Procedures used to maintain traceability of all intermediate and drug substance 
batches back to the batches of the starting material 
 
Information assessing the risk with respect to potential contamination with adventitious 
agents should be provided in Appendix A.2 of the application when appropriate (see 
section X.B of this guidance).  A statement should be provided that bovine-derived 
materials from bovine spongiform encephalopathy (BSE) countries as defined by the U.S. 
Department of Agriculture (9 CFR 94.11) are not used or manipulated in the same 
facility.  Submission of additional facility information could be warranted for multi-use 
facilities where there is a potential for cross-contamination with adventitious agents (see 
sections X.A  and X.B).  Additional facilities information for drug substances derived 
from biological sources should be included in A.1, when appropriate. 
 
Differences between the manufacturing process described in S.2.2  and the manufacturing 
process used to produce the primary stability batches should be discussed in S.2.6. (see 
section IV.F).  
 
  Process Controls 
 
  11 Contains Nonbinding Recommendations 
 
 
 
Process controls is an all-inclusive term used to describe the controls used during 
production to monitor and, if appropriate, adjust the process and/or to ensure that an 
intermediate, postsynthesis material, or unfinished drug substance with an established 
specification or the drug substance will conform to its respective specification. The term 
includes: 
 
  Operating parameters  conditions that can be adjusted to control the manufacturing 
process (e.g., temperature, pH, time, mixing speed) 
  Environmental controls  conditions associated with the manufacturing facility (e.g., 
temperature, humidity, clean room classification) 
  Process tests  measures used to monitor and assess the performance of an on-going 
manufacturing operation (e.g., analysis to determine concentration of reactant or 
product, measuring hydrogen gas uptake during hydrogenation) 
  In-process material tests  measures used to assess the quality attributes and/or the 
suitability for use in the manufacturing process of an isolated intermediate, 
postsynthesis material, or unfinished drug substance  
 
Steps in the process should have the appropriate process controls identified.  Associated 
numeric values can be presented as an expected range.  Process tests and in-process 
material tests can be performed on-line, at-line, or off-line.  All process controls, critical 
or otherwise, should be included in the description of the manufacturing process.  
 
Depending on the drug substance and the manufacturing process, a particular process 
control may or may not be critical as illustrated in the following examples:  
 
  A mixing speed or temperature can be critical for manufacturing steps for protein 
drug substances, but may not be critical for similar operations performed on a 
synthetic chemical 
  The humidity to which a powder is exposed during processing can be critical, but 
may not be critical if the powder is nonhygroscopic 
  The clean room classification can be critical for certain steps in the manufacture of a 
sterile drug substance, but may not be critical for steps before the drug substance is 
rendered sterile or for a nonsterile drug substance  
  An end-of-reaction test used to determine impurity levels can be critical, but an end-
of reaction test to maximize yield may not be critical 
 
All of the operating parameters, environmental conditions, and process tests that ensure 
each critical manufacturing step is properly controlled should be specifically identified as 
critical in the flow diagram and description of the manufacturing process in this section 
of the application (S.2.2) and in S.2.4.  All tests on intermediates, postsynthesis materials, 
and unfinished drug substance should be listed in the description of the manufacturing 
process in S.2.2 and described in S.2.4.  A summary of where information on drug 
  12 Contains Nonbinding Recommendations 
 
 
 
substance quality controls should be located in applications submitted in CTD-Q format 
is provided in Figure 1. 
Figure 1 
 
 
 
3.  Reprocessing, Reworking, Recycling, Regeneration, and Other Operations 
 
Reprocessing should be described in S.2.2, when appropriate.  When used, reworking, 
recycling, regeneration, and salvaging operations should be described in S.2.2.  These 
operations should be adequately controlled to ensure that there is no adverse effect on the 
identity, quality, purity, or potency of the drug substance.  Moreover, reprocessing and 
reworking operations should be capable of producing an improvement in one or more 
quality attributes without having an adverse effect on others.  Information (e.g., 
comparative analytical data) to support the appropriateness of these operations should be 
included in S.2.2 or can be cross-referenced in S.2.2 if information is provided elsewhere 
in the application.  If the operation involves critical manufacturing steps or intermediates, 
information should also be provided in S.2.4.  However, validation data, when warranted 
to support the operation, should be provided in S.2.5. (see section IV.E for possible 
situations when process validation information is warranted.) 
 
a.  Reprocessing  
 
Reprocessing is the introduction of an intermediate or drug substance, including 
one that does not conform to a standard or specification, back into the process and 
  13 Contains Nonbinding Recommendations 
 
 
 
repeating a crystallization or other appropriate chemical or physical manipulations 
(e.g., distillation, filtration, chromatography, milling) that are part of the approved 
manufacturing process.  See section IV.B.3.e for recommendations on chemical or 
physical manipulations performed after quality control release of the material.   
 
Continuation of a manufacturing step after a process test has shown that the step 
is incomplete is considered to be part of the normal process and is not 
reprocessing.  Repetition of a single reaction step should be carefully evaluated 
with respect to the potential formation of by-products and over-reacted materials.  
Repetition of multiple reaction steps is considered to be reworking, rather than 
reprocessing (see section IV.B.3.b).  
 
For most intermediates and drug substances, reprocessing need not be described 
in the application.  In general, the documentation of and data to support the 
reprocessing of a production batch should be retained by the manufacturer and be 
available for review by FDA upon request.  However, if there is a significant 
potential for the reprocessing operation to adversely affect the identity, strength, 
quality, purity, or potency of the drug substance, the reprocessing operations 
should be described and justified in this section (S.2.2) of the application.  For 
example, CVM would consider reprocessing proteins to be reprocessing 
operations that should be described in the application.  
 
Reprocessing is considered a nonroutine event.  If frequent reprocessing is 
expected, the procedures should be included as part of the manufacturing process 
described in the application.  Depending on the frequency and type of 
reprocessing, a reprocessing operation that is included in the application can be 
(1) specified for use under certain circumstances (e.g., repetition of a purification 
step when impurities are found at or above a designated level) or (2) incorporated 
into the existing manufacturing process and performed on each batch when 
reprocessing occurs for the majority of batches. 
  
b.  Reworking 
 
Reworking is subjecting an intermediate or drug substance that does not conform 
to a standard or specification to one or more manufacturing steps that are different 
from the manufacturing process described in the application to obtain acceptable 
quality intermediate or drug substance.  Repetition of multiple reaction steps is 
considered to be reworking because the material to be reintroduced into the 
process is not similar to the original reactant.  Repetition of multiple reaction 
steps is discouraged because of concerns relating to unexpected impurities and 
degradants.   
 
Reworking is considered a nonroutine event.  In general, reworking operations are 
developed postapproval, and the application is updated through submission of a 
prior approval supplement that provides test results and, if appropriate, 
  14 Contains Nonbinding Recommendations 
 
 
 
new or updated analytical procedures that are demonstrated to be appropriate to 
evaluate the effect of the reworking procedure on the identity, quality, purity, or 
potency of the drug substance.  However, if reworking operations are anticipated 
at the time of the original submission, they should be described in this section of 
the application (S.2.2) with justification for the reworking operation.  
   
c.  Recovery 
 
The use of recovered solvents and recycling of filtrates (mother liquors) to 
recover reactants, intermediates, or drugs substance, including for the purpose of 
producing or isolating additional crystals (i.e., second crops), should be described 
in S.2.2.  Recovery operations should be adequately controlled so impurity levels 
do not increase over time.   
 
Recovered solvents can be used with or without further processing to improve the 
quality of the solvent as long as the quality of the recovered solvent is appropriate 
for its intended use.  The use of recovered solvents, including the point at which 
they might be used in the process, should be included in the description of the 
manufacturing process.  The solvent recovery operation itself need not be 
described in detail.  However, information should be provided on whether (1) any 
processing is done to improve the quality of the recovered solvent with a brief 
description of the process (e.g., distillation) and (2) the recovered solvent comes 
only from the manufacture of this drug substance or can come from other sources.  
Appropriate specifications for recovered solvents should be included in S.2.3. 
 
Recycling of filtrates should be included in the description of the manufacturing 
process if these operations are performed.  Information should be provided on the 
maximum number of times material will be recycled and for the process controls 
for such operations.  Data on impurity levels should be provided to justify 
recycling of filtrates. 
 
d.  Regeneration 
 
The regeneration of materials such as column resins and catalysts should be 
described in S.2.2 if these operations are performed.  The process controls for 
regeneration operations should be provided.  Controls on regenerated material can 
include, for example, a maximum number of times the material will be 
regenerated and/or tests to determine the continued suitability (e.g., column 
efficiency) of the material.  When appropriate, specifications for regenerated 
materials should be included in S.2.3  
 
e.  Other Operations 
 
The recommendations for reworking apply to (1) recovery of drug substance from 
drug product or drug product in-process materials or (2) a drug substance, after it 
has been released by the quality control department, that undergoes processing to 
  15 Contains Nonbinding Recommendations 
 
 
 
bring the material back into conformance with its specification (e.g., purification 
of aged material to decrease the level of degradation products to conform with the 
approved acceptance criteria).  The recommendations for reworking operations 
apply irrespective of whether the operation repeats steps that are part of the 
approved manufacturing process (see section IV.B.3.b).  
 
C.  Control of Materials (S.2.3) 
 
Information on the materials (starting materials, reagents, solvents, auxiliary materials, 
and diluents) that will be used to manufacture the drug substance or derive it from a 
biological source, including purification, should be provided in S.2.3.  Information 
indicating where each material is used in the manufacturing process should be provided 
in the flow diagram and in the narrative description of the manufacturing process (S.2.2).  
 
When appropriate, specific tests and acceptance criteria to control microbial 
contamination should be included in the specification for materials used to manufacture 
drug substances.  For materials of biological origin, information assessing the risk with 
respect to potential contamination with adventitious agents should be provided in 
Appendix A.2 of the application when appropriate (see section X.B). 
 
1.   Starting Materials 
 
For application purposes, starting materials mark the beginning of the manufacturing 
process described in an application.  The starting material for application purposes can 
differ from the active pharmaceutical ingredient (API) starting material, which marks the 
point in the manufacturing process from which appropriate GMP should be applied (as 
defined in ICH Q7A:  Good Manufacturing Practice Guidance for Active 
Pharmaceutical Ingredients).  In general, the starting material and API starting material 
should be the same for a synthetic drug substance.  However for a drug substance derived 
from a biological source, the starting material (e.g., plant) and API starting material (e.g., 
extract) can be different.  In this case, information on the biological source (e.g., potential 
pathogens, herbicides, pesticides) is warranted in the application so FDA can evaluate the 
suitability of the biological source as a starting material for drug manufacture (see 
Attachment 2).  The recommendations for starting materials provided in this guidance are 
for application purposes.  See ICH Q7A for recommendations on API starting materials.  
 
Starting materials for a synthetic drug substance are chemical compounds of defined 
molecular structure that contribute to the structure of the drug substance.  A proposed 
starting material for a synthetic drug substance should be chosen so that sufficient 
information will be available to FDA on the manufacturing process to evaluate the safety 
and quality of the drug substance.  The FDA considers (1) cells; (2) plants, plant parts, 
macroscopic fungi, or algae; or (3) animal tissues, organs, or body fluid from which the 
drug substance is derived to be the starting material for a drug substance derived from a 
biological source.  For semisynthetic processes, information should be provided for the 
biological source starting material and starting materials of synthetic origin, if there are 
any.  
  16 Contains Nonbinding Recommendations 
 
 
 
 
The following information should be included in the application to support the proposed 
starting materials:  
 
  A list of proposed starting materials and/or information on plant or animal starting 
materials 
  A flow diagram 
  A specification for each starting material 
  Justification for the proposed starting materials, when appropriate 
 
More detailed information and recommendations on the information to support proposed 
starting materials for synthetic drug substances and starting materials of plant or animal 
origin are included in Attachment 1 and 2, respectively. 
 
2.  Reagents, Solvents, and Auxiliary Materials 
 
The following information should be submitted in S.2.3 for reagents, solvents, and other 
auxiliary materials (e.g., filter aids, decolorizing agents) used in the manufacture of a 
drug substance. When contamination with viral adventitious agents or transmissible 
spongiform encephalopathy (TSE) agents is a concern, additional information may be 
warranted (see section X.A and X.B).  Information on the manufacture of certain reagents 
(e.g., those produced by rDNA technology) may be warranted and when warranted, this 
information should be included in S.2.3.  
 
a.  List of Reagents, Solvents, and Auxiliary Materials 
 
A list of reagents, solvents, and other auxiliary materials used in the manufacture 
of a drug substance should be provided.  
 
b.  Specification 
 
A specification should be provided for each material.  The specification sheet 
should list all tests to which the material will conform and the associated 
acceptance criteria and should also include a reference to the analytical 
procedures that will be used to perform each test.  At a minimum, the reference 
should identify the type of analytical procedure used (e.g., GC, HPLC).  
 
The tests and acceptance criteria in each specification should be appropriate for 
the kind of material and its intended use, and should be consistent with the quality 
of the material used to manufacture the batches of drug substance used to 
establish the specification for the drug substance (see sections VI.A, VI.D, and 
VI.E).  For example, extensive purity testing of an inorganic base used to adjust 
pH would not normally be warranted, but testing of enantiomeric purity might be 
appropriate for an optically active organic acid used in a resolution step.  
 
  17 Contains Nonbinding Recommendations 
 
 
 
Water used in the manufacture of drug substances should be of appropriate quality 
for its intended use.   
 
3.  Diluents 
 
Occasionally the drug substance used to manufacture a drug product is dispersed in a 
diluent (e.g., conjugated estrogens, nitroglycerin).  Information on the controls for the 
diluent (e.g., lactose, dextrose) should be included in S.2.3.  The information should be 
provided at the same level of detail as for a drug product excipient.  Recommendations on 
control of excipients will be provided in section VI of the Drug Product guidance, when 
finalized.  
 
 
 
D.  Controls of Critical Steps and Intermediates (S.2.4) 
 
In this section of the application, all critical operating parameters, environmental 
controls, process tests and all tests performed on intermediates, postsynthesis materials, 
and unfinished drug substance should be listed and their associated numeric ranges, 
limits, or acceptance criteria should be identified.  Any of the tests and associated 
numeric ranges, limits, or acceptance criteria for intermediates, postsynthesis materials, 
or unfinished drug substance that are judged to be non-critical can be indicated as such. 
FDA recommends that the noncritical be listed separately from the critical tests to 
distinguish them from the critical tests that constitute the specification for the 
intermediate, postsynthesis material, or unfinished drug substance. 
 
For all critical process controls, the associated numeric ranges, limits, or acceptance 
criteria should be justified and a brief description of the test provided.  Any experimental 
data to support the justification should be included in this section (S.2.4) as well.  For 
critical operating parameters and environmental conditions, numeric ranges, limits, or 
acceptance criteria typically can be based on the experience gained during the 
development of the manufacturing process.  (See section IV.E for possible exceptions 
when process validation information is warranted.)  Critical process control values from 
relevant batches (i.e., those for which batch analyses have been provided in S.4.4) should 
be provided as part of the justification.  Additional information should be provided in this 
section (S.2.4) under the following circumstances. 
 
  Biological Tests 
 
Analytical procedures and associated validation information should be provided for 
biological tests.11 
 
                                                 
11 The term biological tests includes biological (e.g., animal, cells), biochemical (e.g., enzyme reaction rates), and 
immunochemical procedures.  In this circumstance, procedures from an official compendium to assess pyrogen, 
bacterial endotoxin, sterility, and microbial levels are excluded from this definition. 
  18 Contains Nonbinding Recommendations 
 
 
 
  Tests Used In Lieu of Drug Substance Tests 
 
In some cases, results from tests performed during the manufacturing process (e.g., 
process tests, tests on intermediates, postsynthesis materials, or unfinished drug 
substance) can be used in lieu of testing the drug substance to satisfy a test listed in the 
drug substance specification.  For example, testing to determine the level of a residual 
solvent on an isolated intermediate may be sufficient to satisfy a test listed in the drug 
substance specification provided in S.4.1.  This approach, however, should be supported 
with data that demonstrate that test results or drug substance performance characteristics 
do not undergo an adverse change from the in-process stage to drug substance.  These 
data, along with the analytical procedure and associated validation information, should be 
provided in S.2.4.  Information should be included in the method validation package 
(R.3.S), as appropriate.  When the same analytical procedure is used for both the in-
process test and the drug substance test, the acceptance criterion for the in-process test 
should be identical to or tighter than the acceptance criterion in the drug substance 
specification.  Tests performed in-process in lieu of testing the drug substance should be 
included in the drug substance specification (S.4.1) and the results of such tests should be 
included in the batch analysis report (e.g., certificate of analysis)). 
 
  Intermediates 
 
When warranted, a specification should be established for an isolated intermediate to 
ensure that it has appropriate quality attributes for further downstream processing.  A 
specification for an intermediate should usually include testing for assay and impurities.  
The specification should be provided in S.2.4.  
 
For a semisynthetic drug substance, FDA recommends that the following information be 
provided in S.2.4 for the intermediate used at the beginning of the synthetic operations:  
 
  The chemical name, CAS Registry Number, structure (including amino acid 
sequence, if appropriate), molecular formula, and molecular weight 
  Evidence supporting the chemical structure 
  Information concerning impurities 
  The proposed specification for the intermediate 
 
Because the intermediate is obtained from a plant or animal, the evaluation of potential 
impurities should not be limited to structurally related organic compounds, residual 
solvents, and inorganic impurities.  Other potential sources of impurities (e.g., pesticide 
or herbicide residues in plant-sourced intermediates) should also be considered and 
discussed.  Information concerning the removal or inactivation of adventitious agents in 
intermediates obtained from animal sources should be provided in Appendix A.2 as 
appropriate.  The need for heavy metals testing should be considered due to the 
concentration of metals by some plant species. 
 
  Postsynthesis Materials 
  19 Contains Nonbinding Recommendations 
 
 
 
 
For synthetic or semisynthetic drug substances, a postsynthesis material is a material that 
appears in the process after the final intermediate and before the drug substance 
(unfinished drug substance or form of drug substance used to produce the drug product).  
Postsynthesis materials can differ from the drug substance, for example, in 
stereochemical identity, solid state form, or either the absence of a counterion or the 
presence of a counterion different from that in the drug substance. Although firms have 
sometimes referred to such materials as intermediates, these materials do not meet the 
definition of intermediate and final intermediate provided in this guidance for synthetic or 
semisynthetic drug substances.  If a specification for a postsynthesis material is 
established, this specification should be included in S.2.4.    
 
There is no distinction between intermediates, final intermediate, and postsynthesis 
materials for drug substances derived from biological sources.   The in-process materials 
are referred to as intermediates (see discussion above on intermediates for guidance). 
 
  Unfinished drug substance 
 
Multiple forms (i.e., technical grades) of the drug substance may be part of the 
manufacturing process described in the application.  For example, an applicant might 
purchase a drug substance from a MF holder and then micronize or further purify the 
drug substance for use in its drug product.  If a specification for an unfinished drug 
substance is established, this specification should be included in S.2.4.  The specification 
for the form of the drug substance used to produce the drug product should be included in 
S.4.1. 
 
E.  Process Validation and/or Evaluation (S.2.5) 
 
Validation information relating to the adequacy and efficacy of any sterilization process 
(e.g., drug substance, packaging components) should be submitted in this section of the 
application for sterile drug substances.  Furthermore, if a step in the manufacturing 
process is designed to reduce the amount of microbial contamination, such as for certain 
drug substances derived from biological sources, information to support the 
appropriateness of the step should be included. Submission of other manufacturing 
process validation information in the application is not necessary for most drug 
substances.12  However, for naturally derived protein drug substances, information 
concerning the evaluation of purification processes related to the removal of impurities 
should be provided in this section. When applicable, validation information should be 
provided for processes used to control adventitious agents.  This information should be 
included in A.2. 
 
Submission of validation information for reprocessing and reworking operations usually 
is not warranted.  However, it can be warranted when the reprocessing or reworking 
                                                 
12 All manufacturing processes should be validated.  However, in most cases, the validation information is reviewed 
during facility audits.    
  20 Contains Nonbinding Recommendations 
 
 
 
operation is of the type for which process validation information is submitted when 
routinely performed or when the reprocessing or reworking operations have a significant 
potential to affect the identity, strength, quality, purity, or potency of the product (e.g., 
naturally derived protein drug substances).     
 
F.  Manufacturing Process Development (S.2.6) 
 
A description of the manufacturing process for the drug substance throughout the various 
development phases should be provided in S.2.6.  The primary focus of this description 
should be the relationship between changes in the manufacturing process or 
manufacturing site and any associated changes in the chemical or physical properties of 
the drug substance.  Manufacturing changes associated with changes in the impurity 
profiles of intermediates should also be described.  Information for early manufacturing 
processes (i.e., those used prior to the manufacture of drug substance batches for which 
chemistry, clinical, or toxicity data will be submitted in the application) need not be 
provided. If in vitro studies (e.g., dissolution) or in vivo studies (e.g., bioequivalence) on 
the drug product were warranted because of a change in the drug substance 
manufacturing process, the study results should be summarized,13 and a cross-reference 
to the studies (with study numbers) should be provided in S.2.6. 
 
The primary stability batches should be manufactured using the same manufacturing 
processes (e.g., synthetic route) and procedures and a method of manufacture that 
simulate the process intended for production batches as described in S.2.2.  Section 2.6 of 
the application should contain a description of any significant differences between the 
process used to produce the primary stability batches and the process described in S.2.2 
(see section IV.B).  The description should include an explanation for the differences. 
 
 
V.  CHARACTERIZATION (S.3) 
 
A.  Elucidation of Structure and Other Characteristics (S.3.1) 
 
Data and analysis to support the elucidation of the structure and other characteristics of 
the drug substance should be provided in S.3.1.  Summary information relating to these 
characteristics should be included in S.1.2 and S.1.3.  Key physicochemical 
characteristics of the drug substance that can influence the performance or 
manufacturability of the drug product should be discussed in P.2.1.1 for NADAs and 
ANADAs or the appropriate section of the NADA or ANADA. 
 
1.  Elucidation of Structure 
 
                                                 
13 Here and elsewhere in the guidance when a summary of clinical or nonclinical information is recommended, the 
summary information or a cross-reference to the appropriate summary information in Module 2 of a CTD formatted 
NDA or ANDA can be provided in the specified Module 3 section.  
  21 Contains Nonbinding Recommendations 
 
 
 
The chemical structure of the drug substance should be confirmed using physical and 
chemical techniques such as elemental analysis, mass spectrometry (MS), nuclear 
magnetic resonance (NMR) spectroscopy, ultraviolet (UV) spectroscopy, infrared (IR) 
spectroscopy, X-ray crystallography, and other tests (e.g., functional group analysis, 
derivatization, complex formation).  Issues such as counterion stoichiometry, 
regiochemistry, geometric and configurational isomerism, and absolute stereochemistry 
should be addressed.  When the drug substance consists of more than one molecular 
species, information confirming the structure of each should be provided.  The 
elucidation of structure of synthetic and semisynthetic drug substances, including 
stereochemistry, can be supported by the chemical structures of synthetic precursors.  The 
amount of data warranted to support the elucidation of structure can vary depending on 
the complexity of the molecule. 
 
For naturally derived proteins, the primary, secondary, tertiary and, if applicable, 
quaternary structures should be confirmed using appropriate techniques such as amino 
acid compositional analysis, full amino acid sequencing, peptide mapping, and mass 
spectrometry.  Additional tests (e.g., isoforms analysis, carbohydrate composition or 
sequence) may be warranted for glycoproteins.  For naturally derived protein drug 
substances, additional information on structural characterization can be found in VICH 
GL-40 Specifications: Test Procedures and Acceptance Criteria for New 
Biotechnological/Biological Veterinary Medicinal Products. 
 
2.  Physicochemical Characterization 
 
Detailed information on and data to support the physicochemical characterization of the 
drug substance should be provided in S.3.1.  This information should include data to 
support the general properties listed in S.1.3 (e.g., optical rotation, solubility profile, 
dissociation constant) as well as information and data on more complex physicochemical 
properties that are not included in the list of general properties (e.g., heterogeneity of 
naturally derived proteins).  Information can include data from various analytical 
procedures such as X-ray diffraction (single crystal or powder), thermal analysis (e.g., 
differential scanning calorimetry, thermal gravimetric analysis, hot-stage microscopy), 
particle size analysis, or other spectroscopic techniques (e.g. IR, Raman, solid-state 
NMR, mass).  Moreover, for proteins information can include data from techniques such 
as electrophoresis (e.g., sodium dodecyl sulfate (SDS)-polyacrylamide gel, capillary), 
isoelectric focusing, optical analysis (e.g., circular dichroism), column chromatography 
(e.g., size exclusion, reverse phase-HPLC, ion exchange), and Western-blot.  
 
The kind and extent of the physicochemical characterization information that should be 
provided depends on (1) the type of drug substance (e.g., synthetic molecule, protein), (2) 
the type of dosage form in which the drug substance will be used, (3) the ability or 
tendency of the drug substance to occur in one or more solid state forms, and (4) the 
importance of the differences in physical characteristics of the different forms to the 
stability, dissolution, or bioavailability of the drug product.  The information in S.3.1 can 
be cited elsewhere in the application, for example, to justify proposed process controls or 
lack thereof (see section IV.D), or the presence or absence of tests for physical 
  22 Contains Nonbinding Recommendations 
 
 
 
characterization in the proposed drug substance specification (see sections VI.A and 
VI.E).14 
 
Based on the above stated considerations, an applicant or drug substance manufacturer 
should investigate whether a drug substance is capable of existing in different solid state 
forms.  Solid state form in this context refers to amorphous and crystalline forms, 
hydrates, and solvates. The information can include studies of (1) the conditions that lead 
to the formation of one or another solid state form or (2) the conditions under which one 
solid state form can be converted or equilibrated with another.  Applicants do not need to 
investigate the occurrence of different forms under conditions that deviate significantly 
from the conditions used in the manufacturing processes for the drug substance and drug 
product.  However, screening a variety of solvents with different polarities and hydrogen-
bonding properties can be valuable for early detection of other polymorphs.   
At an appropriate stage of development, the potential for interconversion of solid state 
forms should usually be investigated in stability studies.  A summary of these 
investigations should be included in S.3.1 of the application even if no other forms were 
found.  Information on differences in particle size distribution or crystal habit (shape) can 
also be important in some circumstances.  
 
In some cases, characterization of the drug substance will be insufficient to conclude 
whether the physical properties of the drug substance will have an impact on the 
dissolution or bioavailability of the drug product, and further studies on the drug product 
itself should be conducted.  A summary of these studies should be provided in the 
appropriate section of the NADA or ANADA. 
 
3.  Biological and Other Relevant Characteristics  
 
Information on the elucidation of other relevant characteristics should be provided as 
appropriate.  For example, information on biological activity, purity (e.g., product-related 
substances), and when appropriate, immunochemical properties should be provided for 
naturally derived protein drug substances.  
 
B.  Impurities (S.3.2) 
 
Information on drug substance impurities should be provided in S.3.2.  The applicant 
should summarize the actual and potential impurities most likely to arise during 
manufacture, purification, and storage of the drug substance.  Impurities of all kinds (e.g., 
organic, inorganic, residual solvents) should be discussed.  For drug substances of 
biological origin and semisynthetic drug substances, the description of impurities should 
include, if appropriate, those related to the natural origin of the material (e.g., pesticide 
residues, heavy metals due to the concentration of metals by certain plant species, related 
                                                 
14 ICH Q6A Specifications: Test Procedures and Acceptance Criteria for New Drug Substances and New Drug 
Products: Chemical Substances provides guidance on how to decide what controls on solid state form or particle 
size are appropriate. Although this guidance applies only to new drug substances of synthetic chemical origin, the 
same principles for evaluating solid state form can be used, when appropriate, for other types of drug substances. 
  23 Contains Nonbinding Recommendations 
 
 
 
substances whose concentrations vary with changes in harvesting conditions (species, 
location, season, organ)).  The discussion should identify organic impurities as:  
 
  Impurities observed in the drug substance (both identified and unidentified) 
  Substances that are considered potential impurities but that have not been observed in 
the batches of drug substance manufactured 
  Impurities that were once present in the drug substance but that have been eliminated 
by process modifications 
  Degradation products observed in stability and stress studies on the drug substance or 
following processing (e.g., micronization) 
  
The type of information provided for each impurity can vary with the nature of the 
impurity, the analytical procedure by which it is detected, whether it is actually present in 
significant quantities in the drug substance, whether it has been identified, and the 
methods used to identify the impurity.  
 
Evaluation of inorganic impurities and residual solvents should primarily be guided by 
knowledge of the method of manufacture of the drug substance.  Factors that should be 
considered in evaluating potential sources of organic impurities include the route of 
synthesis, impurities in the starting materials or biological source materials, possible side 
reactions, and potential degradation pathways.  
 
Attempts should be made to identify all impurities found in significant quantities in the 
drug substance.  The studies to characterize these impurities should be described.  FDA 
regulates a variety of drug substances; no single recommendation applies to all drug 
substances for the level of an impurity that would warrant identification.  
Recommendations on identification levels may be provided for specific situations.  For 
example, VICH GL-10(R) Impurities in New Veterinary Drug Substances recommends 
thresholds for the identification and qualification of organic impurities for synthetic new 
drug substances.  As discussed in the guidance, however, those thresholds are not 
necessarily appropriate for potential impurities that are expected to be unusually potent.  
An applicant is encouraged to discuss any questions about the identification of impurities 
with the appropriate review divisions.   
 
The following are typical of the information that should be provided for impurities: 
 
  Identity of the impurity or potential impurity (chemical name and structure) 
  Analytical procedure used to detect or search for the impurity or potential impurity 
  An indication as to whether a potential impurity was actually detected in significant 
quantities in the drug substance (a detailed accounting of the impurities found in 
various batches should be provided in S.4.4) 
  Structural characterization data and/or other data on the physical or chemical 
properties of the impurity or potential impurity 
  Summary of the route of synthesis or method of preparation if the impurity or 
potential impurity was independently prepared 
  24 Contains Nonbinding Recommendations 
 
 
 
  A summary of the attempts made to identify an impurity if it has not been possible to 
identify it 
  A table listing the qualified level of expected impurities with a cross-reference to the 
appropriate studies (including study numbers and batch numbers).  A similar table 
should be provided in section 3.4 of module 4.  
 
For naturally derived protein drug substances, additional information on product-related 
and process-related impurities should be provided as recommended in the VICH GL-40 
Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological 
Veterinary Medicinal Products. 
 
Information concerning the removal or inactivation of adventitious agents in drug substances 
obtained from animal sources (including semisynthetics that originate from an animal source) 
should be provided in Appendix A.2 of the application (see section X.B). Additional guidance is 
available in: 
 
  VICH:  GL10(R) Impurities in New Veterinary Drug Substances 
  VICH:  GL17 Stability Testing of New Biotechnological/Biological Veterinary Medicinal 
Products 
  VICH:  GL18 Impurities:  Residual Solvents in New Veterinary Medicinal Products, Active 
Substances, and Excipients 
 
 
 
VI.  CONTROL OF DRUG SUBSTANCE (S.4) 
 
A.  Specification (S.4.1) 
 
The proposed specification for the drug substance should be provided.  The drug 
substance specification of the drug substance manufacturer, drug product manufacturer, 
and/or applicant should be included in this section, as appropriate.  The specification 
included in this section (S.4.1) should be for the drug substance used to produce the drug 
product.  If the drug substance is processed (e.g., micronized) before it is used to 
manufacture the drug product, the specification for the unfinished drug substance, if there 
is one, should be included in section in S.2.4.  If a physical mixture of two or more drug 
substances is used to produce the drug product, the specifications for the individual drug 
substances should be included in S.4.1 of the application.  The specification for the 
mixture should be include in P.3.4 of the application. 
 
The specification establishes criteria to which each batch of drug substance should 
conform to be considered acceptable for its intended use.  Conformance to specification 
means that the drug substance, when tested according to the listed analytical procedures, 
will meet the listed acceptance criteria.  A specification is one part of the strategy to 
control drug substance quality.  The specification is proposed and justified by the drug 
substance manufacturer and applicant.  Drug substance specifications are part of the 
  25 Contains Nonbinding Recommendations 
 
 
 
approved application.  Specifications are established to confirm the quality of drug 
substances rather than to establish full characterization and should focus on those 
characteristics found to be useful in ensuring the quality of the drug substance as it relates 
to safety and efficacy of the drug product.   Information on periodic quality indicator tests 
is provided below. 
 
The specification sheet should list all tests to which each batch of a drug substance will 
conform and the associated acceptance criteria and should also include a reference to the 
analytical procedures that will be used to perform each test.  Acceptance criteria are 
numerical limits, ranges, or other criteria for the tests described.  If an analytical 
procedure will be used only to generate stability data the analytical procedure should be 
described in S.7.3.  Justified interim acceptance criteria and tests with sunset provisions 
should be included in the specification (see section VI.E).  The specification from the 
applicant and/or drug product manufacturer should identify the tests that it will routinely 
perform and the test results that will be accepted from the drug substance manufacturers 
certificate of analysis (COA).15  Presentation of information in a tabular format is 
suggested.  The specification sheet should also identify: 
 
  Tests that can be performed in-process (e.g., Process tests, intermediate tests, 
postsynthesis material tests, unfinished drug substance tests) in lieu of testing the 
drug substance (the results of such tests should be included in the batch analysis 
report (e.g., Certificate of analysis))   
  All analytical procedures that will be used for a test; identifying which are regulatory 
and which are alternative analytical procedures when multiple analytical procedures 
can be used for a test16  
  Acceptance criteria for the test using the regulatory analytical procedure and 
acceptance criteria for any alternative analytical procedures  
  Release and shelf-life acceptance criteria when both are used 
An illustrative example of a specification sheet is provided in tables 1 and 2, below. 
 
 
 
 
 
 
 
                                                 
15 The applicant and/or drug product manufacturer must establish the reliability of the suppliers analyses through 
appropriate validation of the suppliers test results at appropriate intervals (21 CFR 211.84(d)(2)).  The reliability of 
the analyses need not be established at the time the application is submitted.  However, the specification should 
indicate the tests that will be performed once the reliability of the suppliers results has been established in 
accordance with current good manufacturing practices. 
16 Certain General Chapters in the USP contain a statement that the text of the USP is harmonized with the 
corresponding texts of the European Phamacopoeia (EP) and the Japanese Pharmacopoeia (JP).   However, where 
a difference appears, or in the event of dispute, the result obtained from the USP procedure is conclusive.   
  26 Contains Nonbinding Recommendations 
 
 
 
                                        Table 1:  Specification for Synthesized Drug Substance X 
Tests  Acceptance Criteria  Regulatory  Alternative 
Analytical  Analytical 
Procedure   Procedure 
Appearance  White crystalline powder  Visual   
Identification Tests   Regulatory Analytical Procedure:    (All performed)   
(1)  Retention time of the major peak in     
the chromatogram of the assay  (1)  HPLC, AP1 #  Near Infrared 
preparation corresponds to that in the  EFG  Analysis2 , AP # 
chromatogram of the standard  (2)  Infrared  ABC 
preparation obtained as specified in  Absorption, 
the assay.  USP <197M> 
(2)  Spectra is similar to that of  (3)  Sulfate, USP 
corresponding preparation  of the  <191> 
reference standard   
(3)  Responds to the tests for sulfate 
 
Alternative Analytical Procedure:  
Conforms to established spectral library 
Melting Range  100 to 102C  AP #BCD   USP <741>, 
  Class Ib  
Residue on Ignition  NMT3  0.1%  USP <281>,   
ignition temp. 
225C 
Heavy Metals  0.001%  USP <231>,   
Method II 
Loss on Drying  NMT 1.0%  USP <731>, dry at   
45C to a constant 
weight  
Assay  NLT4 98.0% and NMT 102.0% of  HPLC, AP # EFG   
C H N O , calculated on the dried basis 
x x x x.  
Organic Impurities     HPLC; AP # EFG   
Specified Impurities       
 Impurity A  NMT 0.3%     
 Impurity B  NMT 0.4%     
 Impurity at RRT5 XX   NMT 0.3%     
Unspecified Impurities       
 Any Unspecified  NMT 0.1%     
Total Organic Impurities  NMT 1.0%     
Residual Solvent A  NMT 200 ppm in Drug Substance X or  GC, AP # XYZ   
  NMT 200 ppm in Intermediate C     
Particle Size Distribution    Brand X Particle   
(D)  Size Analyzer 
AP # LMN 
 D (10%)  NMT 5 microns     
 D (50%)  NMT 10 microns     
 D (90%)   NMT 30 microns     
1 AP = Analytical Procedure 
2 Test will be performed on-line during final drying operation. 
3 NMT = not more than 
4 NLT = not less than 
5 RRT = relative retention time 
  27 Contains Nonbinding Recommendations 
 
 
 
 
 
Table 2:  Specification for a Highly Purified Naturally Derived Protein Drug Substance Y1 
Tests  Acceptance criteria  Regulatory Analytical 
Procedure (AP)2 
Appearance  White lyophilized powder  Visual  
Identification Tests: 
Identification Test #1  Retention time of the major peak corresponds to  RP-HPLC3, AP # A123 
that of the reference standard 
Identification Test #2  Retention time of the major peak corresponds to  SE-HPLC4, AP # B345 
that of the reference standard 
Identification Test #3   Major bands of sample correspond to major  Isoform pattern by isoelectric 
bands of the reference standard and account for  focusing/Coomassie Blue 
NLT5 85% of total signal  staining and scanning, AP # 
C678 
Assays: 
Monomer   NLT 95%   SE-HPLC, AP # B345 
Specific Biological Activity  20,000-30,000 International Units (IU)/mg  Mouse Bioassay, AP # D901 
and Lowry, AP# D902  
Purity Tests: 
Dimers and aggregates  NMT6 2%  SE-HPLC, AP # B345 
Oxidized Forms   Area of the peaks corresponding to oxidized  RP-HPLC, AP # E234 
forms is NMT 3% of the sum of peak areas of 
intact and oxidized products 
Electrophoretic purity  No additional significant band (NMT 2%) when  SDS-PAGE7 dissociated and 
compared to the profile of the reference  non-dissociated/silver stain, AP 
# F567 
Bacterial endotoxins  NMT 100 Endotoxin Units (EU)/mg  USP <85>, Gel-Clot 
Techniques 
Microbial Limits  NMT 10 Colony Forming Units (CFU)/10 mg  USP <61>, Plate Method 
Absence of specified indicator organisms 
Water Content  NMT 5% (w/w)  USP <921>, Method Ia 
pH  7.0-8.0 in a solution containing 10 mg of Drug  USP<791> 
Substance Y/mL 
1This is an example specification and is not intended to imply that these are the typical tests and acceptance criteria 
for a naturally derived protein drug substance.  The tests and acceptance criteria appropriate for a particular naturally 
derived protein drug substance depend on the biological source, manufacturing process, and its intended use.  For 
example, (1) residual monoclonal antibody (mAbs) should be monitored for drug substances purified by affinity 
chromatography using mAbs; (2) for proteins that are not as highly purified, less vigorous acceptance criteria for 
purity tests may be appropriate; and (3) the need for bacterial endotoxins and microbial limits testing and the 
associated acceptance criteria depend on the route of administration of the drug product and the controls used during 
the manufacture of the drug product. 
2There are no alternative analytical procedures specified for Drug Substance Y 
3RP-HPLC = reverse phase high-pressure liquid chromatography 
4SE-HPLC = size exclusion high-pressure liquid chromatography 
5 NLT = not less than 
6 NMT = not more than 
7SDS-PAGE =  Sodium dodecyl sulfate polyacrylamide gel electorphoresis 
 
 
 
  Periodic Quality Indicator Tests 
  28 Contains Nonbinding Recommendations 
 
 
 
 
The CGMP regulations require that each batch of drug substance will be tested for 
conformity with the appropriate written specification; a batch that does not meet  the 
specification must not be used to manufacture the drug product (21 CFR 211.84).  
Occasionally and when justified, other tests and associated acceptance criteria and 
analytical procedures that assess drug substance quality can be included in the application 
and not be listed in the drug substance specification.  These tests, referred to as periodic 
quality indicator tests (PQITs), augment the drug substance specification.  A PQIT is 
performed at release on preselected batches and/or at predetermined intervals, rather than 
on a batch-to-batch basis.  A PQIT can be warranted when a test, performed and reported 
as part of the batch analysis, has value as an indicator of drug substance quality, but 
information indicates that the test need not to be performed on each batch of drug 
substance considering the specific drug products in which the drug substance is used.  
Designation of certain tests such as for description, identification, assay, or impurities as 
PQITs would not be considered appropriate.  PQITs, along with the drug substance 
specification, form a basis for approving the application (see, for example, section 
505(b)(1)(D) and 505(d)(3) of the Federal Food, Drug, and Cosmetic Act).17 
 
Sufficient data should be available to support a proposal to designate a test as a PQIT.  If 
sufficient data (e.g., data from multiple batches, all proposed manufacturing sites and 
processes) are available, a PQIT proposal can be included in the original application. A 
proposal for a PQIT should include: 
 
  The reason the PQIT is being proposed 
  Justification and data to support the periodic testing 
  The protocol (e.g., Frequency) for performing the test, including when postapproval 
changes are implemented 
  A commitment 
 
The commitment should state that: 
 
  The PQIT will be performed according to the protocol approved in the application. 
  Failure to meet the acceptance criteria for the PQIT will be handled (e.g., 
Investigation, batch rejection decision) in the same manner as a failure of a test 
included in the drug substance specification and the PQIT will be performed on each 
subsequent batch until the failure is resolved. 
  Any investigation will assess the effect on all batches produced, in particular, the 
batches between the last batch tested with a passing test result and the batch that 
failed. 
  If the result of the investigation confirms a batch failure or is inconclusive, a changes- 
being-effected supplement will be submitted to include the test in the drug substance 
specification. 
                                                 
17 21 U.S.C. 355 (b)(1) and 355 (d)(3). 
  29 Contains Nonbinding Recommendations 
 
 
 
 
A list of PQITs, with associated acceptance criteria and reference to analytical 
procedures, should be included in S.4.1 of the application.  The protocol and commitment 
should also be included in S.4.1.   Data and justification to support the designation of a 
PQIT should be included in S.4.4 and S.4.5, as appropriate.  The recommendations on 
CMC information that should be provided in S.4.2 and S.4.3 also apply to PQITs. 
  
It is recognized that only limited data may be available at the time of submission of an 
application.  Therefore, this concept would generally be implemented postapproval once 
sufficient data are available and after approval of a prior approval supplement. 
 
 
 
B.  Analytical Procedures (S.4.2) 
 
The analytical procedures used for testing a drug substance should be provided.  
Recommendations on the content and format of analytical procedures submitted in 
NADAs and ANADAs will be provided in a forthcoming FDA guidance on Analytical 
Procedures and Methods Validation:  Chemistry, Manufacturing, and Controls 
Documentation.  Information should be provided for all analytical procedures listed in the 
specification (S.4.1).  The following additional guidance is provided on submitting 
analytical procedure information from published sources. 
 
  Analytical Procedures from an Official Compendium or Another FDA-
Recognized Standard Reference 
 
If the analytical procedure used is in the current revision of an official compendium or 
another FDA-recognized standard reference (e.g., AOAC International Book of Methods) 
and the referenced analytical procedure is not modified, the analytical procedure need not 
be provided.  A specific citation to the analytical procedure is sufficient.18  When a 
general chapter or monograph included in an official compendium or other FDA 
recognized standard reference allows for the use of more than one analytical procedure 
for a test, the specific analytical procedure that will be used should be cited here (S.4.2) 
and in the specification (S.4.1).  For example, when using USP <921> Water 
Determination, the method should be specified (e.g., Method Ia).   If an analytical 
procedure is based on one of these sources but has been modified, the analytical 
procedure should be provided. 
 
  Analytical Procedures from Other Published Sources 
 
Analytical procedures from any other published source (e.g., another countrys 
compendium, scientific journal) should be provided. 
                                                 
18 The current revision of an analytical procedure in a compendial monograph or general chapter should be used.  
Therefore, when citing an official compendium, the version of the compendium should not be included in the 
citation.  For example, the USP should be cited rather than USP 25.   
  30 Contains Nonbinding Recommendations 
 
 
 
 
 
C.  Validation of Analytical Procedures (S.4.3) 
 
Analytical validation information, including experimental data (e.g., representative 
chromatograms with peak identification), for the analytical procedures used for testing 
the drug substance should be provided.  Validation of an analytical procedure is the 
process of demonstrating that analytical procedures are suitable for their intended use.  
This information should be provided for all analytical procedures listed in the 
specification (S.4.1).  Stability data (S.7.3), including data from stress studies, should be 
used to support the validation of the analytical procedures.   
 
D.  Batch Analyses (S.4.4) 
 
A description of relevant batches and results of batch analyses should be provided.   
Batch analysis reports (e.g., certificates of analysis (COAs)) should be provided for all 
drug substance batches used for (1) nonclinical studies (i.e., pharmacology and/or 
toxicology), (2) drug product clinical efficacy and safety, bioavailability, bioequivalence, 
and (3) primary stability studies.  Batch analysis data should also be provided for any 
other batches that are being used to establish or justify specifications and/or evaluate 
consistency in manufacturing.  The batch analysis reports and collated batch analyses 
data should include a description of the batches.  This information can be presented (1) 
with the batch data as space permits or (2) in a separate table with only the batch identity 
being included with the batch data.  The description should include: 
 
  Batch identity (i.e., batch number) and size 
  Date of manufacture 
  Site of manufacture 
  Manufacturing process (e.g., synthetic route A), where applicable 
  Use of batch (e.g., bioavailability, stability) 
 
Test results should be expressed numerically or qualitatively (e.g., white crystalline 
powder), as appropriate.  We discourage the use of terms such as conforms or meets 
specification.     
 
1.  Batch Analysis Reports 
 
The batch analysis reports should include results from all tests performed on the batch, 
including tests that are not part of the proposed specification.  References to analytical 
procedures should be provided. 
 
A summary of any changes in the analytical procedures should be provided if the 
analytical procedures (1) changed over the course of generating the batch analyses data 
and/or (2) are different from the analytical procedure included in S.4.2.  The summary 
should identify when an analytical procedure changed, the differences between the 
  31 Contains Nonbinding Recommendations 
 
 
 
analytical procedures, and the impact of the differences with respect to the data being 
reported.  For example, a summary could state that the solvent system for the assay was 
changed on December 15, 1999, from A to B so that impurities Y and Z that co-elute 
using System A could be quantitated separately.  If there are significant differences in the 
analytical procedures (e.g., different fundamental principles such as titration and HPLC), 
a more detailed summary describing the changes may be warranted.  
 
2.  Collated Batch Analyses Data 
 
Presentation of results from all batches for a particular test in tabular and/or graphical 
format is often helpful in justifying the acceptance criteria.  Collated batch analyses data 
are not warranted for all tests.  However, collated data should be provided for assay and 
impurities (e.g., degradation products, residual solvents) and should be considered for 
other tests such as water content. 
 
 
 
Additional guidance is available in: 
  VICH:  GL10(R) Impurities in New Veterinary Drug Substances 
  VICH:  GL18 Impurities:  Residual Solvents in New Veterinary Medicinal Products, 
Active Substances, and Excipients 
 
 
E.  Justification of Specification (S.4.5) 
 
Justification for the proposed drug substance specifications should be provided.  The 
justification should be based on relevant development data (S.2.6), information on 
impurities (S.3.2), standards in an official compendium, batch analyses data (S.4.1), and 
stability studies (S.7), toxicology data, and any other relevant data.  The discussion in this 
section should unify data and information that are located in other sections of the 
application, either by reference or in summary.  When justifying the specification, an 
applicant should consider data from (1) drug substance batches used in evaluating clinical 
efficacy and safety, bioavailability, and/or bioequivalence, (2) primary stability batches, 
and (3) relevant development and process validation batches, when available.  If multiple 
drug substance manufacturing sites or processes are planned, it can be valuable to 
consider data from these sites and processes in establishing the tests and acceptance 
criteria.  This is particularly true when there is limited initial experience with the 
manufacture of the drug substance at any particular site or by any particular method.  
Justification for an in-process test that is used in lieu of a drug substance test should be 
included in S.2.4. 
 
  Tests 
 
Inclusion of a test in the drug substance specification need not be justified.  However, 
exclusion of a test that is normally performed on a type of drug substance, one that is 
  32 Contains Nonbinding Recommendations 
 
 
 
recommended in a relevant FDA guidance, or one that was reported in the batch analyses 
(S.4.4) should be justified.  Justification for the designation of a test as a periodic quality 
indicator test also should be provided (see section VI.A). 
 
Occasionally, it may appear that a test performed and reported as part of the batch 
analyses may not be necessary or that a drug substance characteristic may not be critical 
to the quality of the specific drug products in which the drug substance is used.  For 
example, the available test results for heavy metals may be very low or below the limit of 
detection of the analytical procedure for the batches produced in support of the 
application indicating that there may be no need to perform the test.  However, it is not 
certain if the same type of results will continue to be observed for production batches 
because (1) limited data are available at the time the application is submitted and/or (2) 
the manufacturing process for production batches will be different (e.g., scale, 
equipment) from that used to produce the batches used to support the application and the 
effect, if any, of the differences has yet to be characterized.  In these or similar 
circumstances, an applicant could propose a sunset test protocol for a test, which would 
provide for the test to be dropped from the specification after an agreed number of 
production batches have met certain criteria.19  The proposal should include the (1) 
reason why the sunset provision is being proposed; (2) number of consecutive production 
batches that will be tested before inclusion of the test in the drug substance specification 
is reevaluated; (3) criteria that would be achieved, including data analysis plan, for the 
test to be dropped; and (4) postapproval reporting mechanism for notifying FDA of the 
test results when the criteria have been achieved.  A sunset test protocol could also be 
considered when FDA requests that a test be added to the specification.  
 
  Acceptance Criteria 
 
Justification should be provided for all proposed acceptance criteria included in the drug 
substance specification.  Results from nonclinical (pharmacology and/or toxicology), 
clinical, and stability studies and manufacturing and analytical capability should be 
considered when proposing acceptance criteria.  Proposed acceptance criteria can include 
a reasonable allowance for analytical and manufacturing variability.  The justification 
should discuss the basis of the proposed acceptance criteria from the perspectives of 
available data and analytical and manufacturing capability and variability.  Furthermore, 
any statistical approaches that are used to establish the acceptance criteria should be 
described.  
 
Occasionally, an applicant may wish to propose interim acceptance criteria for a specific 
test because there is some uncertainty whether the same type of results will continue to be 
observed for subsequent drug substance batches.  This uncertainty often occurs when (1) 
there are limited data available at the time the application is submitted and/or (2) the 
manufacturing process for production batches will be different (e.g., scale, equipment) 
from that used to produce the batches used to support the application and the effect, if 
                                                 
19 A proposal to drop a test, based on historical data, can also be submitted postapproval in a prior approval 
supplement. 
  33 Contains Nonbinding Recommendations 
 
 
 
any, of the differences has yet to be characterized.  The proposal should include the (1) 
reason why the interim acceptance criteria are being proposed, (2) number of consecutive  
batches from each process (if alternative processes are used) that will be tested and/or the 
time frame before the acceptance criteria will be finalized, (3) data analysis plan, and (4) 
proposed reporting mechanisms for finalizing the acceptance criteria when the proposed 
final acceptance criteria are tighter, broader, or the same as the interim acceptance 
criteria.  An applicant should not propose using interim acceptance criteria as a substitute 
for providing recommended or agreed upon (e.g., at pre-NADA meetings) information in 
an application.  For example, proposing interim acceptance criteria would not be 
appropriate when the stability data package recommended in the VICH guidance GL3(R) 
Stability Testing of New Veterinary Drug Substance and Medicinal Products has not been 
provided.20   
The proposed acceptance criteria for impurities should not be greater than the levels 
qualified through nonclinical or clinical studies presented in the NADA.  The qualified 
level of each impurity that is individually listed in the drug substance specification should 
be provided in S.3.2.  Appropriate qualified levels can be obtained from published 
toxicology studies or guidance documents.  Acceptance criteria for residual solvents 
should generally be based upon manufacturing capability.  An applicant should consider 
the contribution of residual solvents in its drug product excipients when proposing 
acceptance criteria for residual solvents in the drug substance.  See VICH GL18 
Impurities:  Residual Solvents in New Veterinary Medicinal Products, Active Substances, 
and Excipients. 
 
  Analytical Procedures 
 
The analytical procedures listed in the drug substance specification normally need not be 
justified because the appropriateness of the procedure is supported by information in 
S.4.2, S.4.3, and R.3.S.  In some instances, however, justification for the type of 
analytical procedure used would be warranted.  For example, justification should be 
provided for the use of a nonstability-indicating assay procedure.  The justification 
should explain the scientific reasons why a stability indicating procedure is not viable or 
warranted (e.g., inorganic salts) and, when appropriate, which analytical procedures 
complement the assay procedure by qualitatively and/or quantitatively monitoring 
impurities, including degradants. 
 
 
Additional guidance is available in: 
 
  VICH:  GL10(R) Impurities in New Veterinary Drug Substances 
  VICH:  GL18 Impurities:  Residual Solvents in New Veterinary Medicinal Products, 
Active Substances, and Excipients 
 
 
                                                 
20 For those applications that fall within the scope of these guidances. 
  34 Contains Nonbinding Recommendations 
 
 
 
 
VII.  REFERENCE STANDARDS OR MATERIALS (S.5) 
 
Information on the reference standards or reference materials used for testing of the drug 
substance (active moiety) should be provided.  If the reference standard is obtained from an 
official source, this should be stated.  When the reference standard is not from an official source, 
it should be fully characterized.  A list of any available reference standards for impurities and 
intermediates should be included in S.5. 21 
 
 
 
VIII.  CONTAINER CLOSURE SYSTEM (S.6) 
 
A description of the container closure system for the drug substance should be provided, 
including the identity of materials of construction of each primary packaging component and its 
specification.  The same type of information should be provided for functional secondary 
packaging components as is provided for primary packaging components.  For nonfunctional 
secondary packaging components (e.g., those that do not provide additional protection), only a 
brief description should be provided.  The suitability of the container closure system should be 
discussed with respect to, for example, choice of materials, protection from moisture and light, 22  
compatibility of the materials of construction with the drug substance, including sorption to 
container and leaching, and/or safety of materials of construction.  Stability data used to support 
the suitability of the container closure systems should be provided in S.7.3 and referenced in S.6.  
 
 
 
IX.  STABILITY (S.7) 
 
Information relating to the stability of the drug substance should be provided in S.7.  
 
A.  Stability Summary and Conclusions (S.7.1) 
 
The types of studies conducted, protocols used, and the results of the studies should be 
summarized.  The discussion should include for example (1) a summary of stability 
batches tested, storage conditions used, attributes tested, shelf-life acceptance criteria, test 
schedule, amount of data available, and analysis of data (including a summary of the 
statistical analysis if performed) and (2) conclusions regarding the label storage 
conditions and retest or expiration dating period, as appropriate.  
 
B.  Postapproval Stability Protocol and Stability Commitment (S.7.2) 
 
                                                 
21 Whether or not information is included in the application, complete records must be maintained of any testing and 
standardization of laboratory reference standards (21 CFR 211.194(c)). 
22 Data, such as light transmission data, would be provided in S.6.  Results from photostability studies, when 
warranted, should be provided in S.7.3 and cross-referenced in this section (S.6).  
  35 Contains Nonbinding Recommendations 
 
 
 
A postapproval stability protocol and stability commitment should be provided. 
 
C.  Stability Data (S.7.3) 
 
Results of stability studies, including statistical analysis if performed, should be 
presented in an appropriate format (e.g. tabular, graphical, narrative).  An applicant 
should propose a retest or expiration dating period and appropriate label storage 
conditions for the drug substance.  There should be a direct link between the proposed, 
retest or expiration dating period and proposed label storage conditions and the 
demonstrated stability characteristics of the drug substance.  
 
1.  Primary Stability Studies 
 
The results from long-term, accelerated and, when performed, intermediate studies 
undertaken on primary batches should be provided.  Stability study reports should also be 
included. 
 
The analytical procedures used to generate the data should be identified.   Information on 
the analytical procedures used to generate the data should be included in this section of 
the application as follows: 
 
  The analytical procedure, validation of analytical procedures and justification of 
acceptance criteria, as appropriate, should be included if the analytical procedure 
listed in the stability protocol is different from the analytical procedure described in 
S.4 for the corresponding test (i.e., batch release versus stability analytical 
procedure), or if a test included in the stability protocol is not described in S.4.  
 
  A summary of any changes in the analytical procedures should be provided if the 
analytical procedure was changed over the course of generating the stability data.  
The summary should identify when an analytical procedure changed, the differences 
between the analytical procedures, and the impact of the differences with respect to 
the data being reported.  For example, a summary could state that the solvent system 
for the assay was changed on December 15, 1999, from A to B so that impurities Y 
and Z that co-elute using System A could be quantitated separately.  If there are 
significant differences in the analytical procedures (e.g., different fundamental 
principles such as titration and HPLC) a more detailed summary describing the 
changes may be warranted. 
 
2.  Supporting Stability Studies 
 
Data, other than those from primary stability studies, that support the analytical 
procedures, the proposed retest date or shelf life, and label storage statements can be 
provided.  Such data can include, for example, stability data on small-scale batches of 
drug substance or manufacturing processes not proposed for production batches.  
Stability data to support holding times for intermediates or during processing should also 
  36 Contains Nonbinding Recommendations 
 
 
 
be provided in this section when warranted (e.g. certain proteins).  The analytical 
procedures should be identified, and when analytical procedures are different from those 
described elsewhere in the application, information should be provided on the analytical 
procedures to the extent warranted to support the use of the data.   
 
3.  Stress Studies  
 
Any results from drug substance stress testing should be provided in this section of the 
application.  The design of the stress studies should be discussed briefly.  The 
information should be used, as appropriate, to support the validation of analytical 
procedures (S.4.3), the impurities acceptance criteria and/or characterization of expected 
impurities (S.3.2, S.4.1), justification of the drug product specification (S.4.5), and 
stability summary and conclusions (S.7.1 and S.7.3). 
 
 
Additional guidance is available in: 
 
  VICH:  GL1 Validation of Analytical Procedures:  Definition and Terminology 
  VICH:  GL2 Validation of Analytical Procedures:  Methodology 
  VICH:  GL3(R) Stability Testing of New Veterinary Drug Substance and Medicinal Products
  VICH:  GL5 Stability Testing: Photostability Testing of New Veterinary Drug Substance and 
Medicinal Products 
  VICH:  GL17 Stability Testing of New Biotechnological/Biological Veterinary Medicinal 
Products 
 
 
 
X.  APPENDICES (A) 
 
When warranted, information relating to both drug substances and drug products should be 
included in the appropriate section of the NADA or ANADA according to 21 CFR 514.1(b)(4 
and 5).  If drug substance and drug product information is provided in an appendix, the preferred 
presentation is drug substance information followed by drug product information (e.g., A.1 drug 
substance then drug product, followed by A.2).  The recommendations provided below relate to 
drug substances.  Recommendations on the information to include in the Appendices for drug 
products will be provided in the forthcoming drug product guidance. 
 
A.  Facilities and Equipment (A.1) 
 
Information on facilities and equipment, in addition to the information provided in other 
sections of the application (e.g., S.2.1, S.2.2), is usually not needed.  However, for 
naturally derived protein drug substances, or when contamination with viral adventitious 
agents or transmissible spongiform encephalopathy (TSE) agents is a concern, additional 
information can be warranted and should be included in this section of the application.  
 
  37 Contains Nonbinding Recommendations 
 
 
 
  Viral Adventitious Agents and TSE Agents 
 
All developmental or marketed drug substances manufactured or processed in the same 
areas as the applicants drug substance should be identified when there is potential for 
cross-contamination with TSE agents or viral adventitious agents.  Information should be 
included on the design features of the facility and procedures to prevent cross-
contamination of areas and equipment. 
 
If bovine-derived materials from BSE countries as defined by the U.S. Department of 
Agriculture (9 CFR 94.11) are used or manipulated in the same facility, additional 
information should be provided, such as whether dedicated equipment is used.  
 
  For Naturally Derived Protein Drug Substances  
 
A diagram should be provided illustrating the manufacturing flow, including movement 
of raw materials, personnel, waste, and intermediates in and out of the manufacturing 
areas.  Information should be presented with respect to adjacent areas or rooms that may 
be of concern for maintaining integrity of the drug substance (e.g., cross contamination). 
 
Information on all development or marketed drug substances manufactured or 
manipulated in the same areas as the applicants drug substance should be included. 
 
A summary description of the product-contact equipment and its use (dedicated or multi-
use) should be provided.  Information on preparation, cleaning, sterilization, and storage 
of specified equipment and materials should be included, as appropriate. 
 
Information should be included on procedures (e.g., cleaning and production scheduling) 
and design features of the facility (e.g., area classifications) to prevent contamination or 
cross-contamination of areas and equipment where drug substance manufacturing is 
performed. 
 
For biotechnology-derived protein drug substances, additional recommendations will be 
provided in the forthcoming guidance on the submission of CMC information for a 
therapeutic recombinant DNA-derived product or a monoclonal antibody for in vivo use. 
 
B.  Adventitious Agents Safety Evaluation (A.2) 
 
Information assessing the risk with respect to potential contamination with adventitious 
agents should be provided.  The recommendations provided below relate to the drug 
substance.  Recommendations on the information to include in A.2 for drug product will 
be provided in the forthcoming drug product guidance.  For example, if viral safety 
evaluation studies are performed as part of the drug substance manufacturing (e.g., 
assessment of a starting material from an animal source), the applicant should refer to the 
drug substance guidance.  However, an applicant should refer to the forthcoming drug 
  38 Contains Nonbinding Recommendations 
 
 
 
product guidance for recommendations when the studies are performed as part of the 
drug product manufacturing (e.g., assessment of a biotechnology-derived excipient).  
 
For synthetic or semisynthetic drug substances, reduced testing of materials or drug 
substance and/or validation of removal and/or inactivation of adventitious agents can be 
appropriate in certain instances, with justification.  Such instances can include synthetic 
steps that inactivate adventitious agents.  Early dialog with FDA is encouraged in these 
circumstances. 
 
Furthermore, for biotechnology-derived protein drug substances, additional 
recommendations will be provided in the forthcoming guidance on the submission of 
CMC information for a therapeutic recombinant DNA-derived product or a monoclonal 
antibody for in vivo use. 
 
1.  Nonviral Adventitious Agents 
 
The detailed information regarding the routine manufacturing control of adventitious 
agents, such as bacteria, mycoplasma, and fungi, typically using well-established (e.g., 
pharmacopoeial) analytical procedures, should be provided in the appropriate sections 
within Module 3.2.S.  If well-established (e.g., pharmacopoeial) analytical procedures are 
not used, more detailed information regarding the analytical procedures used should also 
be included in 3.2.S. 
 
With respect to other nonviral adventitious agents, such as transmissible spongiform 
encephalopathy agents and prions, the detailed information should be placed in 3.2.A.2. 
 
Certifications and/or certificates relating to the use of bovine-derived materials and 
sourcing of materials from BSE countries as defined by the U.S. Department of 
Agriculture (9 CFR 94.11) should be provided, as appropriate. 
 
2.  Viral Adventitious Agents  
 
Detailed information from viral safety evaluation studies should be provided in this 
section.  Viral evaluation studies should demonstrate that the materials used in production 
are considered safe and that the approaches used to test, evaluate, and eliminate the 
potential risks during manufacturing are suitable.   
 
Information essential to evaluate the virological safety of materials of animal or human 
origin (e.g., biological fluid, tissue, organ) should be provided.  See related information 
in section IV.C. 
 
The selection of virological tests that are conducted during manufacturing  (e.g., 
unprocessed bulk, post viral clearance testing) should be justified.  The type of test, 
sensitivity and specificity of the test, if applicable, and frequency of testing should be 
included.  Test results to confirm, at an appropriate stage of manufacture (including drug 
substance release if possible), that the product is free from viral contamination should be 
  39 Contains Nonbinding Recommendations 
 
 
 
provided.  (See related information in section.)  Results for viral testing of unprocessed 
bulk should be included. 
 
The rationale and action plan for assessing viral clearance and the results and evaluation 
of the viral clearance studies should be provided.  Data can include those that 
demonstrate the validity of the scaled-down model compared to the commercial scale 
process; the adequacy of viral inactivation or removal procedures for manufacturing 
equipment and materials; and manufacturing steps that are capable of removing or 
inactivating viruses (see related information in section IV.E). 
 
 
 
XI.  REGIONAL INFORMATION (R) 
 
When warranted, information relating to both drug substances and drug products should be 
included in the appropriate section of the NADA or ANADA according to 21 CFR 514.1(b)(4 
and 5).  The recommendations provided below relate to drug substances.  Recommendations on 
the information to include in the Regional Information section for drug products will be provided 
in the forthcoming drug product guidance. 
 
A.  Executed Production Records (R.1.S) 
 
An executed batch record is not required, but if an executed production record is 
provided for illustrative purposes, it should be included in R.1.S. 
 
B.  Comparability Protocols (R.2.S) 
 
A comparability protocol is a protocol describing the specific tests and studies and 
acceptance criteria to be achieved to demonstrate the lack of adverse effect for specified 
types of postapproval manufacturing changes on the identity, quality, purity, and potency 
of the drug substance as these factors may relate to the safety and effectiveness of the 
drug product.  Comparability protocols are optional.  If a comparability protocol is 
proposed, it should be included in this section (R.2.S).   Approval of a comparability 
protocol can justify a reduced reporting category for the particular postapproval change 
described in the protocol. 
 
C.  Methods Validation Package (R.3.S) 
 
Methods validation is the process of demonstrating that analytical procedures are suitable 
for their intended use.  Part of the methods validation process can include FDA 
laboratory analysis to demonstrate that an analytical procedure is reproducible by 
laboratory testing.  
 
 
 
  40 Contains Nonbinding Recommendations 
 
 
 
XII.  LITERATURE REFERENCES (3.3) 
 
When warranted, references to the scientific literature relating to both drug substances and drug 
products should be included in the appropriate section of the NADA or ANADA according to 21 
CFR 514.1(b)(4 and 5).  
 
The full bibliographic reference should be cited close to where the reference appears in the text 
of the application (e.g., in a footnote or section endnote).  The full text of the literature cited 
(e.g., journal article) should be included in the Literature References section, except when 
otherwise indicated.  For example, as previously stated in this guidance, monographs from an 
official compendium need not be included in the application. 
 
  41 Contains Nonbinding Recommendations 
 
 
 
ATTACHMENT 1:   
STARTING MATERIALS FOR SYNTHETIC DRUG SUBSTANCES 
 
A starting material for a synthetic drug substance is a chemical compound of defined molecular 
structure that contributes to the structure of the drug substance.  A reagent that contributes a 
minor structural element to the drug substance (e.g., hydride ion) is not considered to fall within 
the meaning of starting material. A synthesis can be linear or convergent.  Therefore, an 
applicant should propose one or more starting materials to mark the beginning of each synthesis 
branch.  
 
The description of the manufacturing process in an application begins with the starting material 
or materials.  Appropriate GMPs, as defined in ICH Q7A, can apply to the manufacturing steps 
after introduction of the starting material.  Because there is limited FDA oversight of the 
manufacturing of the starting material, the starting material should be selected and controlled so 
that the risk from future changes in the quality of the starting material affecting the identity, 
quality, purity, or potency of the drug substance is minimized.  A proposed starting material 
should be chosen so that sufficient information will be available to the FDA on the 
manufacturing process to evaluate the safety and quality of the drug substance.  A drug substance 
that is used to synthesize another drug substance is not an appropriate candidate for designation 
as a starting material.  An applicant can discuss the selection of proposed starting materials prior 
to submitting its application.  
 
The extent of information that should be submitted in the application to justify the proposed 
starting materials depends on whether or not the chemical has a significant nonpharmaceutical 
market.  FDA will consider the justification provided to support a proposed starting material as 
well as other relevant information such as the proposed starting material specification and 
controls on manufacturing steps downstream from the proposed starting material when 
evaluating the appropriateness of a proposal to designate a chemical as a starting material.    
 
  Starting Materials with a Significant Nonpharmaceutical Market 
 
A significant nonpharmaceutical market is considered to exist if the quantity of the chemical 
needed for the production of the drug substance represents only a small fraction of the chemical's 
total market.  This is true whether the chemical is made by the drug substance manufacturer for 
its own use or is obtained from another firm.  If the quality of the chemical made for the 
nonpharmaceutical market is insufficient to ensure consistent quality of the drug substance and 
the chemical is further processed to produce material of higher quality, the purification 
operations should be described as part of the manufacturing process of the drug substance 
(S.2.2).   See section II of this attachment for recommendations on the documentation that should 
be provided for these starting materials.  
 
  Starting Materials without a Significant Nonpharmaceutical Market 
 
A chemical should not be considered to have a significant nonpharmaceutical market if (1) the 
only market for the chemical is to manufacture drug substance; (2) the drug substance 
  42 Contains Nonbinding Recommendations 
 
 
 
manufacturer had to synthesize the chemical, or arrange for another firm to synthesize it, to 
produce drug substance for clinical trials; (3) an existing manufacturer of the chemical had to 
scale up its process to produce sufficient quantities of drug substance for clinical trials; or (4) the 
method of manufacture was provided by the drug substance manufacturer to the other firms that 
manufacture the chemical.  See sections I and II of this attachment, respectively, for selection 
principles and recommendations on the documentation that should be provided for these starting 
materials. 
 
***** 
I.  SELECTION PRINCIPLES FOR STARTING MATERIALS WITHOUT A 
SIGNIFICANT NONPHARMACEUTICAL MARKET 
 
Each proposed starting material without a significant nonpharmaceutical market should be 
evaluated with respect to the selection principles described in sections I.A through I.D.  These 
principles are intended to assist an applicant in proposing starting materials at a point in the 
process that ensures the following: 
 
  Sufficient information is submitted in the application for FDA to evaluate the safety and 
quality of the drug substance. 
  Future changes in the manufacture of the starting material are unlikely to affect the safety or 
quality of the drug substance.  
 
The selection principles should be discussed when justifying proposed starting materials (see  
II.D.2 of this attachment).  If a proposed starting material is inconsistent with a selection 
principle, this should be justified or the applicant should consider proposing as a starting material 
a chemical earlier in the manufacturing process that is consistent with the selection principles. 
 
A.  Propinquity 
 
A chemical proposed as a starting material should be separated from the final 
intermediate by several reaction steps that result in isolated and purified intermediates.  
Having several reaction steps and associated purification and isolation steps separating 
the starting material and the final intermediate reduces the risk that changes in the 
manufacturing steps prior to the starting material would adversely affect the identity, 
quality, purity, or potency of the drug substance as these factors relate to the safety and 
efficacy of the drug product.  For example, the risk of a new starting material impurity 
(e.g., from a new source or different manufacturing process) being carried over to the 
drug substance decreases as the number of manufacturing steps between the starting 
material and the final intermediate increase.  
 
A reaction followed by multiple purifications should be counted as a single reaction step.  
The reaction step that produces the final intermediate can be counted as a reaction step 
for purposes of evaluating propinquity if the final intermediate is isolated and purified.  
An interconversion of a salt to or from its free acid or base form should not be counted as 
a reaction step for the purpose of evaluating propinquity. 
  43 Contains Nonbinding Recommendations 
 
 
 
 
Isolated and purified intermediates are typically obtained by filtration or centrifugation, 
fractional distillation from a mixture, or chromatographic procedures.  A key element in 
each of these examples is that some removal of organic impurities usually results from 
the isolation operation.  An operation should not be considered to produce an isolated and 
purified intermediate if some purification of this nature does not simultaneously take 
place.  For example, evaporating solvent from a reaction mixture or the extraction work 
up of a reaction mixture is not considered to produce an isolated and purified 
intermediate.  
 
B.  Isolated and Purified 
 
A chemical proposed as a starting material should be an isolated and purified substance. 
Identification of an isolated and purified substance as the starting material, as opposed to 
an in situ and/or crude substance reduces the risk of degradants and/or impurities 
affecting the identity, quality, purity, or potency of the drug substance.   
 
C.  Carryover of Impurities 
 
A chemical proposed as a starting material should not be the source of significant levels 
of impurities in the drug substance.  Robust acceptance criteria for starting material 
impurities reduces the risk of a new starting material impurity (e.g., from a new source or 
different manufacturing process) and/or its associated reaction by-products being carried 
over to the drug substance in levels that warrant identification and qualification from a 
safety perspective.    
 
For purposes of selecting proposed starting materials, a significant level is considered to 
be greater than 0.10 percent in the drug substance (0.20 percent for veterinary drug 
substances not used in human drug products) of any of the following impurities:  
 
  The proposed starting material  
  Impurities in the proposed starting material 
  Synthetic derivatives of impurities in the proposed starting material 
 
Moreover, a proposed starting material should be at or before the point in the 
manufacturing process where transmissible spongiform encephalopathy (TSE) agents can 
be introduced into the process.  For example, if a chemical is produced using an enzyme 
that can introduce TSE agents into the process, the proposed starting material should be 
prior to the enzymatic step regardless of whether the chemical is consistent with all other 
selection principles.  
 
D.  Complexity of Structure 
 
A chemical proposed as a starting material should be readily distinguishable from 
potential isomers and analogs so that adequate controls can be established for the starting 
  44 Contains Nonbinding Recommendations 
 
 
 
materials.  There is increased risk to the identity, quality, purity, or potency of the drug 
substance if a chemical cannot be readily distinguished from its potential isomers and 
analogs.  Moreover, a chemical with a complex molecular structure (e.g., multiple chiral 
centers) are usually produced through complex synthetic pathways, which can also 
increase the risk.  A proposed starting material typically should possess only a limited 
number of functional groups and structural features that can result in geometric or 
stereoisomerism  for it to be considered readily distinguishable.  It is impossible to set 
meaningful limits on the maximum number of such elements that a starting material can 
possess to be considered readily distinguishable.  However, data demonstrating that 
instrumental techniques commonly used for identification tests (e.g., ultraviolet-visible 
spectrophotometry, infrared spectroscopy) are specific can be provided to justify 
proposed starting materials that the Agency might otherwise consider to be too complex.  
If advanced techniques suitable for complex structures (1H-NMR, 13C-NMR, 2D NMR, 
mass spectrometry, elemental analysis, X-ray crystallography, chiral HPLC) are needed 
to distinguish the proposed starting material from potential isomers and analogs, the 
chemical is not an appropriate candidate for designation as a starting material. 
 
 
II.  DOCUMENTATION  
 
Applicants should provide the following information in S.2.3:  
 
A.  List of Proposed Starting Materials 
 
The chemical name, CAS Registry Number, structure, molecular formula, molecular 
weight, and relevant physical characteristics (e.g., appearance, physical state, melting or 
boiling range) should be provided for each proposed starting material. 
 
B.  Flow Diagram of the Complete Synthesis 
 
A flow diagram should be provided showing the complete route of synthesis of the drug 
substance.  Each synthesis branch should begin with chemicals that have a significant 
nonpharmaceutical market, regardless of whether these chemicals are being proposed as 
starting materials.  The proposed starting materials should be highlighted in the flow 
diagram.  
 
If all of the proposed starting materials have significant nonpharmaceutical markets, this 
flow diagram should be the same as the flow diagram provided in S.2.2.  The flow 
diagram in S.2.2 can be cross-referenced.   
 
  45 Contains Nonbinding Recommendations 
 
 
 
C.  Specifications 
 
A specification for each proposed starting material should be provided.  Each 
specification should be based on the quality of the material used to prepare the batches of 
drug substance used to establish the specification for the drug substance (see sections 
VI.A, VI.D, and VI.E of this guidance).  
 
Identification tests for a proposed starting material should be specific and should be able 
to discriminate between it and any related compounds that are likely to be present.  More 
than one identification test may be appropriate.  Tests to confirm the presence of a 
counter ion (e.g., sodium, chloride) should be included in addition to other identity tests.  
 
The specification for a proposed starting material generally should include individual 
limits on impurities and a limit on total impurities.  A limit on unspecified impurities 
should also be considered.  Acceptance criteria for residual solvents and inorganic 
impurities should also be considered, taking into account the potential for carryover.   
Moreover, FDA recommends that acceptance criteria be established for all organic 
impurities that occur above 0.10 percent and that a limit of NMT 0.10 percent be 
established for unspecified organic impurities when there is greater potential for 
impurities originating from the starting material to carryover to the drug substance (0.20 
percent for a veterinary drug substance not used in human drug products).  There can be a 
greater potential for carryover (1) when the proposed starting material is the first isolated 
and purified chemical (counting backwards from the drug substance) consistent with the 
selection principle concerned with the carryover of impurities or (2) based on the 
proximity of the starting materials to the drug substance.  
 
D.  Justification 
 
1.  Starting Materials with a Significant Nonpharmaceutical Market 
 
When a significant nonpharmaceutical market exists for a proposed starting material, the 
discussion of the relationship between the proposed starting materials and the selection 
principles described in section I of this attachment need not be provided.  However, an 
applicant should be prepared to provide documentation demonstrating that a significant 
nonpharmaceutical market exists for a proposed starting material.  Documentation is 
more likely to be requested for proposed starting materials with complex molecular 
structures within a few steps of the drug substance and/or where the extent of use in 
nonpharmaceutical markets is less obvious.  When warranted, this documentation should 
typically consist of the following: 
 
  A description of the uses other than for drug substance production 
  Examples of manufacturers who are able to provide quantities suitable for both 
drug substance production and other markets 
  Confirmation that (1) the drug substance manufacturer did not synthesize the 
chemical, or arrange for another firm to synthesize it, to produce drug substance 
  46 Contains Nonbinding Recommendations 
 
 
 
for clinical trials; (2) an existing manufacturer of the chemical did not scale up its 
process to produce sufficient quantities of drug substance for clinical trials; and 
(3) the method of manufacture was not provided by the drug substance 
manufacturer to the other firms that manufacture the chemical (i.e., no technology 
transfer occurred). 
 
2.  Starting Materials without a Significant Nonpharmaceutical Market 
 
The justification for starting materials without a significant nonpharmaceutical market 
should discuss the relationship between each proposed starting material and the selection 
principles.   
 
Data (e.g., carryover of impurities) used to justify the proposed starting material should 
be from batches manufactured by the proposed manufacturing process.  If data from 
batches produced by other manufacturing processes are also used, the data should be 
clearly identified as supporting data and the differences in these manufacturing processes 
and the proposed manufacturing process should be described. 
 
a.  Propinquity 
 
The flow diagram provided in S.2.3 will indicate the separation between the final 
intermediate and the proposed starting material.  A cross-reference to the flow 
diagram in S.2.3 is sufficient.  
 
b.  Isolated and Purified Substances 
 
The starting material specification and the flow diagrams provided in S.2.3 should 
indicate whether a proposed starting material is an isolated and purified substance.  
Therefore, cross-reference to this information is sufficient.    
 
c.  Carryover of Impurities 
 
Impurities reported in S.3.2 that are found in the drug substance at levels greater 
than 0.10 percent (0.20 percent for a veterinary drug substance not used in human 
drug products) should be listed in S.2.3, or a cross-reference should be provided 
to the information in S.3.2.  For each of the listed impurities, information should 
be provided to demonstrate that the impurity did not originate from the proposed 
starting material.  Such information should consist of, for example: 
 
  Analytical data demonstrating that the impurity is not present in the 
proposed starting material 
  Data indicating that the impurity originates as part of the synthetic process 
after the introduction of the proposed starting material 
  47 Contains Nonbinding Recommendations 
 
 
 
  Analytical data to show that the bulk of the impurity found in the drug 
substance originates from sources other than the proposed starting 
material, when the assignment of the source of an impurity in the drug 
substance is uncertain (e.g., An impurity might logically result from the 
degradation of the proposed starting material, the drug substance, or any 
of the intermediates in between)  
 
If changes were made in the manufacturing process that follows the introduction 
of the starting material (e.g., by the addition of a purification procedure or by the 
repetition of an existing procedure on a routine basis) so that the proposed starting 
material is not a significant source of impurities in the drug substance, this should 
be clearly stated in the discussion.  
 
If a firm is not able to identify one or more of the impurities present above 0.10 
percent in the synthetic drug substance (0.20 percent for a veterinary drug 
substance not used in human drug products), an empirical approach can be 
attempted provided that the proposed starting material can be demonstratively 
purified by recrystallization or some other technique.  Two samples of the 
proposed starting material, one the quality of the material used to prepare the 
batches of drug substance used to establish the specification for the drug 
substance (see sections VI.A, VI.D, and VI.E of this guidance) and one highly 
purified, can be converted under identical conditions at bench scale to drug 
substance.  If the unidentified impurities are present in both samples of drug 
substance, this would indicate that they do not originate from impurities in the 
proposed starting material.  If this approach is used, applicants should provide a 
report documenting all salient aspects of the experiment.  
 
d.  Complexity of Structure 
 
Information on the complexity of the structure of the starting material need not be 
provided for proposed starting materials that possess only a limited number of 
functional groups and structural features that can result in geometric or 
stereoisomerism.  However, if the chemical structure of the proposed starting 
material is sufficiently complex, information should be provided to support that 
the starting material is readily distinguishable from potential isomers and analogs 
using common instrumental techniques (e.g., ultraviolet-visible 
spectrophotometry, infrared spectroscopy).  Applicants should provide data (e.g., 
analytical, spectra) comparing the proposed starting material to a reasonable 
selection of isomers and analogs to demonstrate that the identification tests for the 
proposed starting material are sufficiently specific. 
 
 
  48 Contains Nonbinding Recommendations 
 
 
 
III.  POSTAPPROVAL ISSUES 
 
When a starting material has been designated in and approved as part of an application, 
postapproval changes to the manufacturing process of the approved starting materials, including 
changes in the route of its synthesis, need not be reported to the Agency unless a commitment to 
report such changes was included in the approved application.  Changes in the specification of an 
approved starting material and changes to the manufacturing process of the drug substance 
following the introduction of the starting material should be reported to the Agency in 
accordance with applicable regulations and guidances.  
 
It is valuable for drug substance manufacturers to maintain close communication with 
manufacturers of starting materials.  The quality of a starting material can be affected by changes 
in manufacturing process (e.g., changes in solvents, purification, catalysts, route of synthesis), 
and knowledge that a change has taken place can assist a drug substance manufacturer in 
maintaining a valid starting material specification.  
 
  49 Contains Nonbinding Recommendations 
 
 
 
ATTACHMENT 2:    
STARTING MATERIALS OF PLANT OR ANIMAL ORIGIN 
 
 
The FDA considers (1) cells; (2) plants, plant parts, macroscopic fungi, or algae; or (3) animal 
tissues, organs, or body fluid from which the drug substance is derived  to be starting material for 
a drug substance derived from a biological source.  Identification of the biological source is 
warranted to ensure the identity, quality, and purity of the drug substance and to address critical 
safety issues (e.g., viruses, residual pesticides).  The term drug substance derived from a 
biological source includes drug substances that are the chemical obtained directly from the 
biological source and semisynthetic drug substances that are produced by modification of a 
chemical (i.e., intermediate) obtained from the biological source.  A semisynthetic drug 
substance can have more than one starting material, depending on the number of branches in the 
synthetic portion of the manufacturing process.  A drug substance is considered semisynthetic 
when at least one of the starting materials is of biological origin.  
 
The recommendations in Attachment 2 do not pertain to: 
  
  Starting materials that are highly purified chemicals obtained from biological sources that 
had significant nonpharmaceutical markets before they were used in the drug substance 
synthesis (e.g., Sucrose, tartaric acid).  
  Starting materials of synthetic origin for semisynthetic drug substances 
  Cells used in fermentation processes 
  Cells or tissue used in cell culture processes 
  Transgenic plants or animals 
 
The recommendations in Attachment 1 apply to starting materials of biological origin that have 
significant nonpharmaceutical markets and starting materials of synthetic origin for 
semisynthetic drug substances.  Starting materials for antibiotics and other cellular metabolites 
produced by microorganisms using conventional fermentation processes will be covered by a 
forthcoming guidance.  
 
I.  DOCUMENTATION  
 
Applicants should provide the following information in S.2.3 for plant or animal starting  
materials.  For semisynthetic drug substances the information recommended in Attachment 1 
should be provided for the starting materials of synthetic origin, if there are any, in addition to 
the information provided for the plant or animal starting materials.  
 
A.  Information on Plant or Animal Starting Materials 
 
The following should be provided for plant starting materials: 
 
  Biological identification (i.e., Family, genus, species, variety) and the process for 
confirming taxonomic authenticity 
  50 Contains Nonbinding Recommendations 
 
 
 
  Part of the plant used (e.g., Seed, flower, roots, all) 
  Geographic areas of harvesting (e.g., Countries, provinces, states) 
  Growing season and harvest time 
  List of pesticides and herbicides that may be used in the geographic areas of 
harvesting  
  Supplier (i.e., Company with overall responsibility for collecting biomass, not 
individual harvesters, plantation owners, or subcontractors) 
 
The following should be provided for animal starting materials: 
 
  Biological identification (i.e., Species)  
  Specific part of animal used (e.g., Pancreas, bone, urine) 
  Country of origin23  
  A list of known diseases or pathogens associated with the type of animal  
  Criteria for ensuring animal health  
  For animals that are consumed for food, a statement of compliance with USDA or 
equivalent requirements 
  Supplier (i.e., Company with overall responsibility for collecting biomass, not 
individual farmers or subcontractors) 
 
B.  Flow Diagram of the Manufacturing Process 
 
When the drug substance is the chemical obtained directly from the biological source this 
flow diagram should be the same as the flow diagram in S.2.2.  The flow diagram in S.2.2 
can be cross-referenced.    
 
For semisynthetic drug substances, the flow diagram should depict the manufacturing 
process that results in the chemical (i.e., intermediate) from the biological source and the 
synthetic part of the manufacturing process.  See Attachment 1, Section II. B for 
recommendations on the flow diagram for the synthetic part of the manufacturing 
process. 
 
C.  Specifications for Plant or Animal Starting Materials 
 
The specification for the starting material should be based on the quality of the material 
used to prepare the batches of drug substance used to establish the specification for the 
drug substance (see sections V.A, V.D, and V.E of this guidance).  The specification for 
plant starting materials should include identity tests for determining taxonomic 
authenticity and, when appropriate, screening for pesticides and herbicides.  The 
specification for the animal starting material should include screening for adventitious 
agents, when appropriate.   
                                                 
23 Bovine-derived materials should not be from bovine spongiform encephalopathy (BSE) countries as defined by 
the U.S. Department of Agriculture (9 CFR 94.11) unless otherwise exempted by the Agency. 
 
  51 Contains Nonbinding Recommendations 
 
 
 
 
A chemical substance (e.g., plant extract) used to produce a semisynthetic drug substance 
or a crude drug substance derived from a plant or animal starting material is considered 
an intermediate.  Information on the intermediate, including the specification, should be 
provided in S.2.4.   
 
 
II.  ENVIRONMENTAL ASSESSMENT 
 
All  NADAs and ANADAs must include either an environmental assessment (EA) or claim of 
categorical exclusion from the requirement to provide an environmental assessment (21 CFR 
25.15(a)).  Environmental information should be included in the Environmental Impact section 
of an NADA or ANADA.  Applicants should refer to the VICH guidance GL6 Environmental 
Impact Assessments (EIAs) for Veterinary Medicinal Products (VMPs) and 21 CFR part 25 for 
additional information on environmental assessments.  
 
 
III.  POSTAPPROVAL ISSUES  
 
Changes in the information on plant or animal starting materials (see section I.A of this 
attachment) should be reported to the Agency in a prior approval supplement.  The supplement 
should include a new or revised environmental assessment or claim of categorical exclusion from 
the requirement to provide an environmental assessment, as appropriate.  Information should also 
be provided concerning the potential for the change to result in new impurities or higher levels of 
known impurities.  A change that is merely editorial or administrative (e.g., a change in 
ownership of the supplier with no change in the process for overseeing collection of biomass) 
can be submitted in an annual report. 
  52 Contains Nonbinding Recommendations 
 
 
 
GLOSSARY 
 
 
Adventitious Agents:  For the purpose of this guidance, pathogenic viruses and non-viral agents 
(e.g., transmissible spongiform encephalopathy agents, pathogenic bacteria, mycoplasma) in 
plants, animals, or cells or any materials derived therefrom, used in the manufacture of human 
drug substances or products 
 
Alternative Processes:  Two or more manufacturing processes described in an application that 
can be used to prepare the same intermediate or drug substance   
 
Auxiliary Materials:  Substances (e.g., charcoal, filter aid) used during the manufacturing 
process of a drug substance that are not normally considered to be starting materials, 
intermediates, reagents, solvents, catalysts, or diluents 
 
Critical: Describes a process step or process control (e.g., process condition, test requirement, or 
other relevant parameter or item) that must be controlled within predetermined criteria to ensure 
that the drug substance meets its specification 
 
Crystal Shape (Habit):  Crystals with the same internal structure but different external shape 
because different crystal faces have developed during growth 
 
Degradation Product:  A molecule resulting from a chemical change in the drug molecule 
brought about over time and/or by the action of, for example, light, temperature, pH, water, 
and/or by reaction with an excipient (or diluent), another drug substance, and/or the immediate 
container closure system.  Also called decomposition product. 
 
Drug Substance:  An active ingredient that is intended to furnish pharmacological activity or 
other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease or to 
affect the structure or any function of the human body, does not include intermediates used in the 
synthesis of such ingredient (21 CFR 314.3(b)).   The term drug substance can also be used to 
refer to a physical mixture of two or more drug substances used to produce a fixed-combination 
drug product.     
 
Final Intermediate:  In reference to synthetic and semisynthetic drug substances, the last 
compound synthesized before the chemical reaction that produces the molecule or ion 
responsible for the physiological or pharmacological action of the drug substance.  The chemical 
reaction that transforms the final intermediate into a form of the drug substance involves more 
than a change in salt form (including a salt with hydrogen or coordination bonds) or other 
noncovalent derivatives (such as complex chelates or clathrates). 
 
Identification Threshold:  A limit above (>) which an impurity should be identified (VICH 
GL10) 
 
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In-process Material Tests:  Measures used to assess the quality attributes of an intermediate, 
postsynthesis material, or unfinished drug substance and/or their suitability for use in the 
manufacturing process  
 
In Situ Intermediate:  An intermediate that is not isolated.  It is normally, but not necessarily, in 
solution 
 
Intermediate:   
 
  For synthetic drug substances, a material produced during steps of the synthesis of a drug 
substance that undergoes further molecular change before it becomes a drug substance.  
Intermediates may or may not be isolated (VICH GL10(R)) 
 
  For drug substances derived from a biological source, a material produced during the 
manufacturing process of a drug substance that undergoes further purification or molecular 
modification before it becomes a drug substance  
 
Intermediate Tests:  Measures used to assess the quality attributes of an intermediate and/or its 
suitability for use in the manufacturing process  
 
Operating Parameters:  Conditions that can be adjusted to control the manufacturing process 
(e.g.,  temperature, pressure, pH, time, mixing speed) 
 
Particle Size Distribution:  A measurement of the relative proportion of particles in a sample as 
a function of size 
 
Physical Properties:  Attributes such as physical state, melting point, boiling point, solubility, 
hygroscopicity, color, density, refractive index, partition coefficient, crystal shape, solid state 
form, and particle size distribution 
 
Polymorphic Forms:  Different crystalline forms of the same drug substance.  These can 
include solvation or hydration products (also known as pseudo-polymorphs) and amorphous 
forms  
Postsynthesis Material:  For synthetic or semisynthetic drug substances, a postsynthesis 
material is a material that appears in the process after the final intermediate and before the drug 
substance (unfinished drug substance or form of drug substance used to produce the drug 
product).  Postsynthesis materials can differ from the drug substance, for example, in 
stereochemical identity, solid state form, or either the absence of a counterion or the presence of 
a counterion different from that in the drug substance. Although firms have sometimes referred 
to such materials as intermediates, these materials do not meet the definition of intermediate and 
final intermediate provided in this guidance for synthetic or semisynthetic drug substances. 
Postsynthesis Material Tests:  Measures used to assess the quality attributes of a postsynthesis 
material and/or its suitability for use in the manufacturing process  
 
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Process Controls:  An all-inclusive term used to describe the controls used during production to 
monitor  and,  if  appropriate,  adjust  the  process  and/or  to  ensure  an  intermediate  with  an 
established specification or the drug substance will conform to its respective specification.  The 
term includes operating parameters, environmental controls, process tests, intermediate tests, 
postsynthesis materials tests, and unfinished drug substance tests.  
Process Tests:  Measures used to monitor and assess the performance of the process (e.g., a test 
to evaluate reaction progress) 
 
Reaction Step:  A unit operation or number of unit operations that effect a change in the 
molecular structure of a starting material or intermediate.  More than one reaction step can take 
place sequentially in a single reaction vessel. 
 
Residual Solvents:  Organic volatile chemicals that are used or produced in the manufacture of 
drug substances or excipients, or in the preparation of drug products, that are not completely 
removed by practical manufacturing techniques (VICH GL18) 
 
Retest Period: The period of time during which the drug substance is expected to remain within 
its specification and, therefore, can be used in the manufacture of a given drug product, provided 
that the drug substance has been stored under the defined conditions. After this period, a batch of 
drug substance destined for use in the manufacture of a drug product should be retested for 
compliance with the specification and then used immediately. A batch of drug substance can be 
retested multiple times and a different portion of the batch used after each retest, as long as it 
continues to comply with the specification.  For most biotechnological/biological substances 
known to be labile, it is more appropriate to establish a shelf life than a retest period.  The same 
may be true for certain antibiotics (VICH GL3(R)). 
 
Semisynthetic Drug Substance:  A drug substance where structural elements have been 
introduced by a combination of chemical synthesis and elements of biological origin 
 
Solid State Form:  A particular crystalline or noncrystalline structure of a solvated or 
nonsolvated drug substance.  This can include polymorphs, pseudopolymorphs (hydrates or 
solvates), and amorphous forms. 
 
Specification:  The quality standard (i.e., tests, analytical procedures, and acceptance criteria) 
provided in an application to confirm the quality of drug substances, drug products, 
intermediates, raw materials, reagents and other components including container closure system 
and in-process materials.  A specification sheet includes the list of tests, reference to analytical 
procedures, and acceptance criteria. 
 
Starting Material:  Materials that mark the beginning of the manufacturing process as described 
in an application.  A starting material for a synthetic drug substance is a chemical compound of 
defined molecular structure that contributes to the structure of the drug substance.  The starting 
material for a drug substance obtained from a biological source is considered to consist of the (1) 
cells; (2) plants, plant parts, macroscopic fungi, or algae; or (3) animal tissues, organs, or body 
fluid from which the drug substance is derived.  
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Synthesis Branch:  A portion of a convergent synthesis that ends with an intermediate that is to 
be covalently joined with another intermediate or starting material in the next step of the 
synthesis 
 
Unfinished Drug Substance:  A form of the drug substance that is further processed to produce 
the form of the drug substance used to manufacture the drug product 
 
Unfinished Drug Substance Tests: Measures used to assess the quality attributes of an 
unfinished drug substance and/or its suitability for use in the manufacturing process  
 
Validation:  A documented program that provides a high degree of assurance that a specific 
process, method, or system will consistently produce a result meeting predetermined acceptance 
criteria  
 
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