Bispecific Antibody 
Development Programs 
 
Guidance for Industry 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
Center for Biologics Evaluation and Research (CBER) 
 
 
May 2021 
Pharmaceutical Quality/CMC 
 
35086505fnl.docx    
Bispecific Antibody 
Development Programs 
Guidance for Industry 
 
 
 
 
Additional copies are available from: 
 
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Food and Drug Administration 
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https://www.fda.gov/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/Guidances/default.htm    
 
 
 
 
 
 
U.S. Department of Health and Human Services 
Food and Drug Administration 
Center for Drug Evaluation and Research (CDER) 
Center for Biologics Evaluation and Research (CBER) 
 
 
May 2021 
Pharmaceutical Quality/CMC 
 
  Contains Nonbinding Recommendations 
 
TABLE OF CONTENTS 
 
 
 
I.  INTRODUCTION............................................................................................................. 1 
II.  BACKGROUND ............................................................................................................... 2 
A.  Monoclonal and Bispecific Antibody Development .................................................................... 2 
B.  General Considerations ................................................................................................................. 2 
C.  Regulatory Considerations ............................................................................................................ 3 
III.  SCIENTIFIC CONSIDERATIONS ................................................................................ 4 
A.  CMC Quality Considerations ....................................................................................................... 4 
B.  Nonclinical Considerations ........................................................................................................... 4 
C.  Clinical Considerations ................................................................................................................. 5 
1. Clinical Pharmacology Studies ........................................................................................................ 5 
2. Other Clinical Studies ...................................................................................................................... 6 
REFERENCES .............................................................................................................................. 7 
  Contains Nonbinding Recommendations 
 
Bispecific Antibody Development Programs 
Guidance for Industry1 
 
 
This guidance represents the current thinking of the Food and Drug Administration (FDA or Agency) on 
this topic.  It does not establish any rights for any person and is not binding on FDA or the public.  You 
can use an alternative approach if it satisfies the requirements of the applicable statutes and regulations.  
To discuss an alternative approach, contact the FDA office responsible for this guidance as listed on the 
title page.   
 
 
 
 
I.  INTRODUCTION  
 
This guidance provides recommendations to assist industry and other stakeholders involved in 
the development of bispecific antibodies.  In addition to general considerations, the guidance 
provides recommendations for specific regulatory, quality, nonclinical, and clinical 
considerations for bispecific antibody development programs.  Although this guidance is 
intended for bispecific antibodies, the principles discussed in this guidance may also inform the 
development of other types of bispecific protein products and multispecific products.2  This 
guidance does not discuss development considerations for other multitarget therapies that are 
antibody cocktails, polyclonal antibody products, or combinations of monoclonal antibodies.3    
 
This guidance focuses on a range of regulatory and scientific considerations for bispecific 
antibodies, but not on development of a particular bispecific antibody.  Of note, many aspects of 
a bispecific antibody development program will be similar to monoclonal antibody development 
programs.  This guidance discusses unique aspects for chemistry, manufacturing, and controls 
(CMC), as well as nonclinical and clinical development programs for bispecific antibodies.  
Industry and other stakeholders are encouraged to engage FDA to discuss their individual 
bispecific antibody development program.   
 
 
1 This guidance has been prepared by the Office of Medical Policy in the Center for Drug Evaluation and Research 
in cooperation with the Center for Biologics Evaluation and Research at the Food and Drug Administration.  
 
2 Examples of such products include single domain, antibody mimetics, non-antibody domain, alternative format, T-
cell receptor mimetics, non-immunoglobulin (Ig) domain and non-Ig scaffold.  Bispecific protein products target 
two antigens and, as used in this guidance, the term multispecific product refers to a therapeutic product that targets 
three or more antigens.   
 
3 In an antibody cocktail, different antibodies are mixed together during manufacturing.  In a polyclonal antibody, a 
mixture of antibodies recognizing either specific or diverse targets is obtained by purification of pooled plasma or 
serum.  In a combination of monoclonal antibodies, separate antibodies are used together.  Each of the products can 
follow its own dosing regimen or can be combined at the time of administration. 
 
  1  Contains Nonbinding Recommendations 
 
The contents of this document do not have the force and effect of law and are not meant to bind 
the public in any way, unless specifically incorporated into a contract.  This document is 
intended only to provide clarity to the public regarding existing requirements under the law.  
FDA guidance documents, including this guidance, should be viewed only as recommendations, 
unless specific regulatory or statutory requirements are cited.  The use of the word should in 
Agency guidances means that something is suggested or recommended, but not required. 
 
 
II.  BACKGROUND 
 
A.  Monoclonal and Bispecific Antibody Development  
 
Therapeutic monoclonal antibodies, first commercialized in 1986, have become a vital 
component of therapy for various diseases and conditions including, but not limited to, cancer, 
autoimmune and infectious diseases, and inflammatory conditions (Ecker et al. 2015).  The 
regulatory pathway for evaluation of monoclonal antibodies is well established, but additional 
guidance is warranted regarding antibody-based products that target more than one antigen.  
Advances in technology and an interest in novel therapies that combine targets have led to the 
development of bispecific antibodies, which are genetically-engineered, recombinant antibodies 
that consist of two distinct binding domains capable of binding two different antigens or two 
different epitopes of the same antigen (Brinkmann and Kontermann 2017; Kontermann 2012).4  
 
A scientific rationale often exists for engaging two targets in the therapeutic strategy for a 
specific disease.  Bispecific antibodies can target multiple disease-modifying molecules with 
one drug, with possible advantages over combination therapy or the use of antibody mixtures.  
The possibility of immune cell retargeting through the delivery of an effector or effector cell to 
a specific target cell or the possibility of synergistic efficacy through engagement of multiple 
targets gives bispecific antibodies the potential to advance the development of antibody-based 
therapies (Suresh et al. 2014; Kontermann 2012).  Challenges may arise in developing 
bispecific antibodies such as immunogenicity related to novel structures and complex 
structural and functional characterization.  This guidance addresses these considerations and 
provides recommendations regarding the type of data necessary to support the approval of 
bispecific antibodies.   
 
B.  General Considerations  
 
FDA anticipates there will be a spectrum of bispecific antibodies developed for the prevention, 
treatment, or diagnosis of diseases, each with unique considerations for the specific product and 
targeted indication.  Within this spectrum there are two broad categories of bispecific antibodies:  
 
(1) Bispecific antibodies that function to bridge two target cells (e.g., a bispecific antibody 
that is designed to bring immune effector cells into close contact with particular tumor-
 
4 Although this guidance focuses on bispecific antibodies, it may also apply to other novel constructs that may have 
three or more antigen-binding domains. 
 
  2  Contains Nonbinding Recommendations 
 
associated antigens to facilitate cell killing).  This type of bispecific antibodies would 
require binding to both targets at the same time for efficacy.   
 
(2) Bispecific antibodies with functions not involving bridging two target cells, such as a 
bispecific antibody that targets two soluble cytokines, binds different epitopes of the 
same tumor cell or viral antigen, or engages two different targets to mimic the function of 
an endogenous protein.  In this category, the bispecific antibody may sometimes, but not 
always, be required to bind both targets at the same time for efficacy.  
 
Within each category, potential considerations are relevant to a bispecific antibody development 
program, including determining whether both targets need to be engaged simultaneously, 
determining the affinity and on- and off-rates of each arm for its target, and determining possible 
synergy when binding both targets.  
 
FDA anticipates there will be a scientific rationale, including target(s), mechanism(s) of action, 
or increased safety and/or efficacy as compared to similar monospecific products5 to support 
development of a particular bispecific antibody.  The data supplied to support the scientific 
rationale will depend on the particular situation6 and could potentially be derived from clinical or 
animal studies7 or in vitro assays. 
 
C.  Regulatory Considerations 
 
FDAs regulation on fixed-combination prescription drugs for humans (21 CFR 300.50) does 
not apply to the development of bispecific antibodies, which are single molecules.  Although 
not generally expected, in some cases FDA may request a comparison of the bispecific 
antibody to an approved monospecific product(s) directed against the same antigenic target(s) 
to inform the benefit-risk assessment of the bispecific antibody (see section III.C.2 of this 
guidance for clinical study considerations).   
 
As noted in section I, this guidance discusses unique aspects of bispecific antibody 
development programs.  Questions about regulatory requirements for a particular bispecific 
antibody should be directed to the appropriate FDA clinical review division.  Sponsors are 
encouraged to discuss plans for their individual products with the appropriate clinical review 
division within FDA early in development.  
 
5 As used in this guidance, the term monospecific product refers to a therapeutic antibody that targets a single 
antigen. 
 
6 See the International Council for Harmonisation (ICH) guidance for industry M4E(R2):  The CTD  Efficacy (July 
2017) for more information on product development rationale.  Also see the guidance for industry Codevelopment of 
Two or More New Investigational Drugs for Use in Combination (June 2013) for more information on rationale for 
biological product development.  We update guidances periodically.  For the most recent version of a guidance, 
check the FDA guidance web page at https://www.fda.gov/regulatory-information/search-fda-guidance-documents.  
 
7 FDA encourages sponsors to consult with FDA if they wish to use a non-animal testing method they believe is 
suitable, adequate, validated, and feasible.  FDA will consider if such an alternative method could be assessed for 
equivalency to an animal testing method.  FDA supports the principles of the 3Rs, to reduce, refine, and replace 
animal use in testing when feasible.   
 
  3  Contains Nonbinding Recommendations 
 
 
 
III.  SCIENTIFIC CONSIDERATIONS     
 
Many aspects of a bispecific antibody development program will be similar to monoclonal 
antibody development programs.  This section discusses unique aspects for CMC, nonclinical 
and clinical pharmacology, and clinical development programs for bispecific antibodies.  
 
A.  CMC Quality Considerations 
 
Bispecific antibodies can exist in many different formats including, for example, tandem 
monovalent binding fragments as well as immunoglobulin G (IgG)-based antibodies where each 
arm binds a different antigen or onto which multiple additional antigen-binding domains are 
attached.  These diverse formats allow bispecific antibodies to be designed to match the 
proposed mechanism(s) of action and the intended clinical application (Spiess et al. 2015).   
 
Unique development considerations may be relevant for each of the formats, such as quality, 
stability, and production yields, but in general the products should be characterized and the 
manufacturing processes should be developed in accordance with standard monoclonal antibody 
development practices.8  Quality attributes that may affect pharmacology should be studied, 
including antigen specificity; affinity and on- and off-rates; avidity (for bispecific antibodies that 
target two molecules on the same cell); potency; product-related impurities such as aggregates, 
fragments, homodimers, and other mispaired species; stability; and half-life.  For example, in 
vitro and in vivo pharmacology studies may provide information on the relative binding activity 
and on- and off-rates for each target.  Design of the potency assay(s) will depend on the target 
product attributes.  Early in vitro studies may inform selection of an expression construct with 
optimal affinity and stability properties.  The relative amounts of homodimers should be 
assessed.  This evaluation is particularly important for effector cell engaging constructs where 
homodimers of the anti-CD3 or anti-Fc engaging arm may lead to cytokine release.  Also, novel 
structures could potentially lead to increased immunogenicity.   
 
B.  Nonclinical Considerations   
 
Nonclinical studies are generally needed to characterize the pharmacology and toxicology of 
bispecific antibodies.  The scope of the nonclinical program, including pharmacology studies and 
species selection for toxicology studies (including general and reproductive toxicology), is 
expected to be similar to that for monoclonal antibodies directed against a single target.9,10  
 
8 See Points to Consider in the Manufacturing and Testing of Monoclonal Antibody Products for Human Use 
(February 1997) for more information on product manufacturing and testing 
(available at https://www.fda.gov/media/76798/download). 
 
9 See the ICH guidance for industry S6(R1) Preclinical Safety Evaluation of Biotechnology-Derived 
Pharmaceuticals for more information (available at https://www.fda.gov/regulatory-information/search-fda-
guidance-documents/s6r1-preclinical-safety-evaluation-biotechnology-derived-pharmaceuticals).  
 
10 See the ICH guidance for industry S9 Nonclinical Evaluation for Anticancer Pharmaceuticals (March 2010) for 
more information. 
  4  Contains Nonbinding Recommendations 
 
Consideration should be given to the expression profile and specificity for each target in 
nonclinical models in order to design an appropriate toxicological assessment for the bispecific 
product.  Potential safety concerns related to the particular components of the bispecific 
antibody, if any, should be addressed, but a comparative safety assessment between the 
bispecific antibody and monospecific product(s) will likely not be recommended.  
 
In vitro and in vivo pharmacology studies may also offer the opportunity to generate nonclinical 
data supporting the scientific rationale of the bispecific antibody.  Examples include (1) showing 
that blocking two targets yields additive or synergistic efficacy compared to a monospecific 
comparator, (2) showing that simultaneous cross-linking of two receptors offers efficacy that 
cannot be achieved with a monospecific product, or (3) showing expected activation of the 
immune system for products that either directly activate the immune system or potentiate that 
activation.  These studies could also be used to select the first-in-human dose.11  
 
In general, standard nonclinical approaches to support the safety of the starting dose in the 
clinical trial will be appropriate.12  For bispecific antibodies with agonistic properties, selection 
of the initial dose using a minimally anticipated biologic effect level should be considered.13,14  
We recommend discussing dose selection with the appropriate FDA clinical review division.   
 
C.  Clinical Considerations  
 
1.  Clinical Pharmacology Studies  
 
The clinical pharmacology studies for a bispecific antibody development program should be 
similar to those for monoclonal antibodies and other therapeutic protein products.  
Pharmacodynamic assessments should take into consideration the binding to each target.    
 
Bispecific antibodies may present as a mixture of biologically active (e.g., unbound and capable 
of binding a ligand) and inactive forms (e.g., bound and not capable of binding a ligand) in 
biological matrices.  Considerations should be given to identifying the bispecific antibody 
form(s) most relevant to pharmacokinetic/pharmacodynamic assessment and to develop 
validated assays to measure the appropriate form(s) accordingly.  Therefore, more than one assay 
may be recommended to quantify appropriate forms.  In some instances, pharmacodynamic 
 
 
11 See Points to Consider in the Manufacturing and Testing of Monoclonal Antibody Products for Human Use for 
more information on product safety data. 
  
12 See the guidance for industry Estimating Maximum Safe Starting Dose in Initial Clinical Trials for Therapeutics 
in Adult Healthy Volunteers (July 2005) for more information on product dosing.  Healthy volunteers may not be 
appropriate candidates for initial clinical trials of a particular bispecific antibody because of the potential 
immunogenicity and toxicity of the bispecific antibody.   
 
13 See footnote 12. 
 
14 A retrospective analysis examining toxicity profile and approaches in selecting the first in human (FIH) dose for 
17 CD3 bispecific constructs concluded that an FIH dose at 1030% pharmacological activity was an acceptable 
approach for all constructs examined (Saber et al 2017).   
  5  Contains Nonbinding Recommendations 
 
activity measurements may be considered to develop assays to measure and quantify appropriate 
form(s) of the bispecific antibody.   
 
Bispecific antibodies possess multiple domains that function in different ways to mediate clinical 
efficacy.  An immune response to one domain may inhibit a specific function while leaving 
others intact.  When examining immune responses to bispecific antibodies, it may be appropriate 
to develop multiple assays to measure immune responses to different domains of bispecific 
antibodies.15,16  Sponsors are encouraged to discuss with FDA specific clinical pharmacology 
development plans for their individual products.  
 
2.  Other Clinical Studies  
 
FDA recommends that sponsors define the overall benefit-risk profile of the bispecific antibody.  
In many situations, the clinical studies for bispecific antibodies will compare the bispecific 
antibody to standard of care or placebo.  If monospecific products approved for the same 
indication exist and they target the same antigens as those targeted by the bispecific antibody, it 
may be possible to perform a clinical study comparing the bispecific antibody to the 
monospecific product(s).   
 
A clinical trial comparing a bispecific antibody to an approved monospecific product(s) directed 
against the same antigenic target(s) may inform the benefit-risk assessment of the bispecific 
antibody.  For example, if both targets are anticipated to be immunosuppressive, based on the 
animal/early human trials suggesting unique or greater safety concerns, a trial comparing the 
bispecific antibody to the approved monospecific product(s) may be appropriate, if feasible.  
Also, if there is a concern that only one of the bispecific antibodys targets was driving the 
efficacy results, to better inform the benefit-risk assessment of the bispecific antibody, it may be 
useful to conduct a trial with the relevant monospecific product(s).  FDA may request such 
studies in certain cases if they are viewed as potentially providing valuable information 
regarding the bispecific antibodys efficacy or safety.17,18   
 
Overall, studies conducted to inform the benefit-risk assessment and support approval will 
depend on the particular targets and other clinical considerations.  Sponsors are encouraged to 
discuss development plans for their individual products with the appropriate clinical review 
division within FDA.   
   
 
15 See the guidance for industry Immunogenicity Testing of Therapeutic Protein Products  Developing and 
Validating Assays for Anti-Drug Antibody Detection (January 2019), where assay development is covered in detail. 
 
16 See the guidance for industry Immunogenicity Assessment for Therapeutic Protein Products (August 2014) for 
more information on immunogenicity assessment.  
  
17 See the guidance for industry Providing Clinical Evidence of Effectiveness for Human Drug and Biological 
Products (May 1998) for more information on quantity of evidence to support effectiveness. 
  
18 See Points to Consider in the Manufacturing and Testing of Monoclonal Antibody Products for Human Use for 
more information on product safety testing. 
  6  Contains Nonbinding Recommendations 
 
 
 
REFERENCES 
 
 
Brinkmann, U and RE Kontermann, 2017, The Making of Bispecific Antibodies, mAbs; 
Feb/Mar; 9(2):182212, doi: 10.1080/19420862.2016.1268307. 
 
Ecker, DM, SD Jones, and HL Levine, 2015, The Therapeutic Monoclonal Antibody Market, 
mAbs, 7(1):914, doi: 10.4161/19420862.2015.989042. 
 
Kontermann R, 2012, Dual Targeting Strategies With Bispecific Antibodies, mAbs, Mar-Apr; 
4(2):182197, doi: 10.4161/mabs.4.2.19000. 
 
Saber H, Del Valle P, Ricks TK, Leighton JK., 2017, An FDA Oncology Analysis of CD3 
Bispecific Constructs and First-In-Human Dose Selection, Regul Toxicol Pharmacol; 
Nov; 90:144152, doi: 10.1016/j.yrtph.2017.09.001. 
 
Spiess, C, Q Zhai, and PJ Carter, 2015, Alternative Molecular Formats and Therapeutic 
Applications for Bispecific Antibodies, Mol Immunol, Oct; 67(2 Pt A):95106, doi: 
10.1016/j.molimm.2015.01.003. 
 
Suresh, T, LX Lee, J Joshi, and SK Barta, 2014, New Antibody Approaches to Lymphoma 
Therapy, J Hematol Oncol, Sep 9; 7:58, doi: 10.1186/s13045-014-0058-4. 
 
 
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