monoclonal antibodies: what are the pharmacokinetic and pharmacodynamic considerations for drug...

1. Introduction

2. Antibody structure

3. Antibody pharmacokinetics

4. Pharmacodynamics

5. PK/PD relationship

6. Bioanalytical approaches to

quantify mAb and its target

7. Prediction of mAb human

pharmacokinetics/

pharmacodynamics based on

preclinical information

8. FIH dose

9. Conclusion

10. Expert opinion

Review

Monoclonal antibodies: whatare the pharmacokinetic andpharmacodynamic considerationsfor drug development?Rong Deng†, Feng Jin, Saileta Prabhu & Suhasini Iyer†Department of Pharmacokinetic and Pharmacodynamic Sciences, Genentech, Inc.,

South San Francisco, CA, USA

Introduction: The number of monoclonal antibodies available for clinical use

and under development has dramatically increased in the last 10 years. Under-

standing their pharmacokinetics and pharmacodynamics is essential for

selecting the right clinical candidate, correct dose and regimen for a

target indication.

Areas covered: This article reviews the existing literature and knowledge of

monoclonal antibodies. Specifically, the authors discuss monoclonal antibod-

ies with respect to their pharmacokinetics (including absorption, distribution

and elimination) and their pharmacodynamics. The authors also look at the

pharmacokinetic/pharmacodynamic relationship, scaling from preclinical to

clinical studies and selection of the first-in-human dose.

Expert opinion: Monoclonal antibodies have complex pharmacokinetic and

pharmacodynamic characteristics that are dependent on several factors.

Therefore, it is important to improve our understanding of the pharmaco-

kinetics and pharmacodynamics of monoclonal antibodies from a basic

research standpoint. It is also equally important to apply mechanistic pharma-

cokinetic/pharmacodynamic models to interpret the experimental results and

facilitate efforts to predict the safety and efficacy of monoclonal antibodies.

Keywords: first-in-human, monoclonal antibody, pharmacodynamics, pharmacokinetics, scaling

Expert Opin. Drug Metab. Toxicol. (2012) 8(2):141-160

1. Introduction

To date, more than 20 monoclonal antibodies (mAbs) and mAb derivatives, includ-ing fusion proteins and mAb fragments, are available for a variety of therapeuticapplications (Table 1). More than 500 mAbs are in different stages of developmentas drug molecules. Pharmacokinetic (PK) and pharmacodynamic (PD) assessmentsare critical components of drug discovery and development. These assessments arecritical in the initial selection of appropriate drug candidates and their clinical devel-opment from Phase I through Phase IV. PK and PD characteristics of mAbs areunique and differ from therapeutic small molecules (Table 2); they are dependenton the structure of mAbs and their antigen targets. This review provides a brief over-view of the primary PK and PD considerations for the development oftherapeutic mAbs.

2. Antibody structure

Abs related to the immunoglobulin (Ig) superfamily are roughly Y-shaped moleculesor combinations of such molecules. There are five major classes of Igs: IgG, IgA,IgD, IgE, and IgM. IgG can be further divided into four subclasses (IgG1, IgG2,

10.1517/17425255.2012.643868 © 2012 Informa UK, Ltd. ISSN 1742-5255 141All rights reserved: reproduction in whole or in part not permitted

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IgG3 and IgG4). IgG is the predominant class, comprisingabout 80% of the Igs in human serum. Thus, IgGs and theirderivatives shape the framework for the development of ther-apeutic Abs. The general structure of an IgG with its struc-tural components is depicted in Figure 1. IgGs are composedof two identical heavy (H) chains (50 -- 55 kDa) and twoidentical light (L) chains (25 kDa), linked through disulfide(S--S) bonds at the hinge region. Approximately 110 firstamino acids of H and L chains form the variable (V) regions(VH and VL, respectively) that function as antigen-binding regions. Each V domain contains three short stretchesof peptide with hypervariable sequences (HV1, HV2 andHV3). These are known as complementarity-determiningregions (CDR), that is, the region that binds the antigen.The regions between the CDR in the V region are called theframework regions. The remaining sequences of each L chainconsist of a single constant domain (CL). The remainder ofeach H chain contains three constant regions (CH1, CH2

and CH3). Constant regions CH2 and CH3 are responsiblefor binding to complement receptor C1q. This binding acti-vates the complement cascade, or Fcg receptor (FcgR) forAb-dependent cellular cytotoxicity (ADCC), or neonatal Fc

receptor (FcRn)-mediated response, which protects IgGfrom degradation in the lysosome and is involved in the trans-port and clearance of mAb. Carbohydrate moieties that can becovalently attached to the CH2 region of the H chain impactthe effector function of an Ab. The binding characteristicsof CDR and Fc receptors affect the PK/PD behavior ofthe Ab.

3. Antibody pharmacokinetics

3.1 Antibody absorptionmAbs are large molecules with limited gastrointestinal stabilityand poor lipophilicity. This results in insufficient resistanceagainst the hostile proteolytic gastrointestinal milieu and verylimited permeation through the lipophilic intestinal wall.mAbs are, therefore, commonly administered parenterally.Although the majority of approved mAbs are registered fori.v. administration, there are many that are administered byextravascular routes (e.g., adalimumab (s.c.), efalizumab (s.c.),omalizumab (s.c.), ustekinumab (s.c.), golimumab (s.c.), cana-kinumab (s.c.), palivizumab (i.m.), ranibizumab (i.t.v.)). Thebioavailability of mAbs administered s.c. or i.m. is around50 -- 100% with the maximal plasma concentrations observed1 -- 8 days following administration [1] and is dependent onthe site of injection [1,2]. The bioavailability of PAmAb, ahuman mAb against Bacillus anthracis protective antigen, inhealthy volunteers is 50 -- 54% following i.m. administrationinto gluteus maximus and 71 -- 85% following i.m. administra-tion into vastus lateralis [2]. The mechanisms of mAbs adminis-tered through s.c. or i.m. routes are poorly understood.However, it is believed that lymphatic drainage contributes tothe absorption of mAbs after s.c. or i.m. administration butat a slow rate due to their large molecular weight [1]. Recently,it has been observed that FcRn played an important role in thebioavailability of mAbs following s.c. administration [3]. Thes.c. bioavailability of a murine mAb IgG1 was reduced signifi-cantly (about threefold) in the FcRn deficient compared withthat in the wild-type (WT) mice [3].

The volume of an s.c. injection is limited to around1 -- 1.5 ml due to physiological constraints. Therefore, unlessmAbs are highly potent, they are typically administeredthrough the i.v. route. One approach, which has been usedto overcome the s.c. dosing barrier and improve the bioavail-ability of mAbs, is the Halozyme drug delivery technology.Halozyme is a recombinant hyaluronidase that could dra-matically increase the volume of s.c. injection [4]. Theapplication of this technology in s.c. administration oftrastuzumab and rituximab is being evaluated in clinicaltrials [5].

3.2 Antibody disposition3.2.1 Antibody distributionDistribution of mAbs is a multiple-step process that includesconvection, diffusion, transcytosis, binding and catabolismat the binding site [1]. In general, the volume of distribution

Article highlights.

. The pharmacokinetic (PK) and pharmacodynamic (PD)of mAbs are often complicated. They differ fromsmall-molecule drugs and depend on both the structureof Abs and their targets.

. The general IgG structure has been well defined andeach part has its own specific functions.

. Many factors can affect the PK of mAbs including theirstructure, FcRn-binding affinity, target density, targetturnover rate, binding affinity to target, immunogenicity,glycosylation, effector function, potential off-targetbinding, charges, other concomitantly administratedmedicines, demographic factors, disease status,bioanalytical methods and others.

. Biomarkers are important PD endpoints of mAbs.Diagnostic and prognostic biomarkers are the most well-studied biomarkers in oncology and have beensuccessfully used to select patient populations fortreatment with some mAbs.

. PK of Abs often depends on PD. Understanding the PK/PD relationship is key for predicting treatment efficacyand assisting in dose optimization.

. A reliable bioanalytical method for measuring levels ofmAbs and their targets is critical for characterizing theirPK and PD, as well as understanding their PK/PDrelationships.

. Nonspecific clearance of mAbs is generally wellpredicted based on the data from cynomolgus monkeys.For specific clearance and PD of mAbs, the extrapolationto humans requires more thorough consideration due tothe complexity of the PD.

. A minimum anticipated biological effect level approachfor a first-in-human (FIH) study is valuable for mAbswith high risk.

This box summarizes key points contained in the article.

Monoclonal antibodies: what are the pharmacokinetic and pharmacodynamic considerations for drug development?

142 Expert Opin. Drug Metab. Toxicol. (2012) 8(2)

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Table

1.Thepharm

aco

kinetics/pharm

aco

dynamicsofmarketedantibodies.

Generic

name

Brand

name

Target

Antibody

type

FDA/EMA

approval

date

Indications

Administra-

tionroute

Elimination

t 1/2

Volumeof

distribution

s.c.

bioavailability

PD

biomarker

Quantitative

PK/PD

relationsh

ip

Ref.

Abciximab

ReoPro

�Glycoprotein

IIB/IIIA

receptor

Chim

eric

IgG1Fab

1994

Ischemiccardiac

complications

mg/kg,i.v.

Linear,20--30min

0.118l/kg

NA

Platelet

Yes

[115]

Adalim

umab

Humira�

TNF-a

HumanIgG1

2002

Rheumatoid

arthritis,

psoriaticarthritis,

ankylosing

spondylitis,Crohn’s

disease,psoriasis,

juvenile

idiopathic

arthritis

mg,s.c.

Linear,14days

(10--20days)

4.7

--6.0

L64%

CRP,ESR,IL-6,

MMP-1,MMP-3

currently

unknown

[54]

Alemtuzumab

Campath

�CD52

Humanized

IgG1

2001

B-cellchronic

lymphocyticleukem

ia

mg,i.v.

Nonlinear,11h

to6days

11.3

lNA

Whitebloodcell

Currently

unknown

[116]

Basilixim

ab

Sim

ulect

�IL-2

receptor

(CD25)

Chim

ericIgG1

1998

Prophylaxisof

acute

organrejection

inpatients

receiving

renaltransplantation

mg,i.v.

Linear,7.2

±3.2

days

8.6

±4.1

lNA

IL-2Ra

Yes

[73]

Bevacizumab

Avastin

�VEGF

Humanized

IgG1

2004

Colorectalcancer,

non-small-celllung

cancer,breast

cancer,glioblastoma

mg/kg,i.v.

Linear,20

(11--50)days

3.25l(m

ale),

2.66l(female)

NA

Currently

unknown

Currently

unknown

[117]

Canakinumab

Ilaris�

IL-1b

HumanIgG1

2009

Cryopyrin-associated

periodicsyndromes

mg

(WT>40kg);

mg/kg(15£

WT£40),s.c.

Linear,26days

6.01l

70%

CRP,SAA

Currently

unknown

[118]

Catumaxomab

Removab�

EpCAM/CD3

Rat-murine

IgG2

2009

Malignantascites

IP2.5

days

(0.7

--

12days)

Nopublic

data

NA

Currently

unknown

Currently

unknown

[119]

Certolizumab

pegol

Cim

zia�

TNF-a

Humanized

Fabfragment

2008

Crohn’s

disease

s.c.

14days

6--8l

80%

(76--88%

)

CRP

Currently

unknown

[120]

Cetuximab

Erbitux�

EGFR

Human/

murinechim

eric

IgG1

2004

EGFR-expressing

metastaticcolorectal

cancer,squamous

cellcarcinomaof

headandneck

cancer

mg/m

2,i.v.

Nonlinear,112h

(63--230h)when

dose

>200mg/m

2

2--3l/m

2NA

KRAS

Currently

unknown

[121,45]

Daclizumab

Zenapax�

IL-2

receptor

(CD25)

Humanized

IgG1

1997

Preventionofkidney

transplantrejection

mg/kg,i.v.

20(11--38)days

2.5

l(V

c) ’

3.4

(Vp)

NA

Currently

unknown

Currently

unknown

[122]

ADC:Antibody--drugconjugate;CD:Clusterofdifferentiation;CRP:C-reactiveprotein;EGFR:Epiderm

algrowth

factorreceptor;EpCAM:Epithelialcelladhesionmolecule;ESR:Erythrocyte

sedim

entationrate;Fab:Antigen-

bindingfraction;ICAM:Intercellularadhesionmolecule;IL:Interleukin;i.m.:Intramuscular;IP:Intraperitoneal;i.t.v.:Intravitreal;i.v.:Intravenous;

KRAS:V-Ki-ras2

Kirstenratsarcomaviraloncogenehomolog;LD

H:Lactate

dehydrogenase;

MMP:Matrixmetalloproteinase;NA:Notapplicable;PD:Pharm

acodynamic(s);PK:Pharm

acokinetic(s);q2w:Once

every

2weeks;RA:Rheumatoid

arthritis;RANKL:

ReceptoractivatorofnuclearfactorkappaBligand;RSV:Respiratory

syncytialvirus;SAA:Serum

amyloid

a;s.c.:Subcutaneous;TNF-a:

Tumornecrosisfactoralpha;uNTX/cr:Urinary-N-telopeptide/creatinineratio;V:Volumeofdistribution;Vc:Volumeofdistributionforcentralcompartment;VEGF:

Vascular

endothelialgrowth

factor;Vp:Volumeofdistributionforperipheralcompartment;Vss:Volumeofdistributionatsteadystate;Vz:Volumeofdistributionduringterm

inal(Z)phase;WT:Weight.

Deng, Jin, Prabhu & Iyer

Expert Opin. Drug Metab. Toxicol. (2012) 8(2) 143

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Table

1.Thepharm

aco

kinetics/pharm

aco

dynamicsofmarketedantibodies(continued).

Generic

name

Brand

name

Target

Antibody

type

FDA/EMA

approval

date

Indications

Administra-

tionroute

Elimination

t 1/2

Volumeof

distribution

s.c.

bioavailability

PD

biomarker

Quantitative

PK/PD

relationsh

ip

Ref.

Denosumab

Xgeva

�RANKL

HumanIgG2

2010

Preventionof

skeletal-related

events

inpatients

withbonemetastases

from

solid

tumors

s.c.

28days

119--158ml/

kg(V

ss/F)

62%

uNTX/cr

Yes

[123,124]

Eculizumab

Soliris�

Complement

protein

C5

Humanized

IgG2/4

2007

Paroxysm

al

nocturnal

hemoglobinuria

mg,i.v.

272±82h

7.7

lNA

LDH

Currently

unknown

[125]

Efalizumab

Raptiva

�CD11

Humanized

IgG1

2002

Withdrawn

in2008

Psoriasis

mg/kg,s.c.

Nonlinear,

12--44days

63.4

ml/kg(V

c)

56.4%

CD11a

Yes

[126]

Gemtuzumab

ozogamicin

Mylotarg

�CD33

Humanized

(conjugatedto

calicheamicin)

ADC

2000

Withdrawn

in2010

CD33-positive

acute

myeloid

leukemia

infirst

relapse

mg/m

2,i.v.

Nonlinear,41h

fortotalAbafter

firstdose

10lafterfirst

dose;18lafter

seconddose

(Vss)

NA

CD33

Currently

unknown

[127]

Golim

umab

Sim

poni�

TNF-a

HumanIgG1

2009

RA,psoriatic

arthritis,

ankylosing

spondylitis

mg,s.c.

14days

58--126ml/kg

53%

CRP,IL-6

MMP-3,

ICAM-1,VEGF

Currently

unknown

[76]

Ibritumomab

Tiuxetan

Zevalin

�CD20

MurineIgG2

2002/2004

Non-Hodgkin’s

lymphoma(NHL)

i.v.

30h

Nopublic

data

NA

Bcell

Yes

[128]

Inflixim

ab

Remicade�

TNF-a

Human/

murinechim

eric

IgG1

1998

Crohn’s

disease,

RA,ulcerative

colitis,psoriasis,

psoriaticarthritis,

ankylosing

spondylitis

mg/kg,i.v.

Linear,7--12days

3--6l

NA

serum

IL-6,CRP,

TNF-a

Currently

unknown

[80]

Muromonab-

CD3

Orthoclone

OKT�3

CD3

Murine

1986

Allograftrejection

mg,i.v.

18hrs

Nopublic

data

NA

Currently

unknown

Currently

unknown

[129]

Natalizumab

Tysabri�

a4subunit

ofa4

b1a4

b7integrin

Humanized

IgG4

2006

Relapsingremitting

multiple

sclerosis,

Crohn’s

disease

mg,i.v.

Multiple

sclerosis11±

4days;Crohn’s

disease

10±

7days

Multiple

sclerosis5.7

±

1.9

l,Crohn’s

disease

5.2

±

2.8

l

NA

Leukocytes

Currently

unknown

[130]


algrowth


sedim



KRAS:V-Ki-ras2


H:Lactate

dehydrogenase;

MMP:Matrixmetalloproteinase;NA:Notapplicable;PD:Pharm



every


arthritis;RANKL:

ReceptoractivatorofnuclearfactorkappaBligand;RSV:Respiratory


amyloid


Tumornecrosisfactoralpha;uNTX/cr:Urinary-N-telopeptide/creatinineratio;V:Volumeofdistribution;Vc:Volumeofdistributionforcentralcompartment;VEGF:

Vascular

endothelialgrowth





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Table

1.Thepharm

aco

kinetics/pharm

aco

dynamicsofmarketedantibodies(continued).

Generic

name

Brand

name

Target

Antibody

type

FDA/EMA

approval

date

Indications

Administra-

tionroute

Elimination

t 1/2

Volumeof

distribution

s.c.

bioavailability

PD

biomarker

Quantitative

PK/PD

relationsh

ip

Ref.

Ofatumumab

Arzerra�

CD20

HumanIgG1

2009

Chronic

lymphocytic

leukemia

refractory

to

fludarabineand

alemtuzumab

mg,i.v.

Themeant 1/2

betw

eenthe4th

and12th

infusions

wasapproximately

14days

(range:

2.3

--61.5

days).

1.7

--5.1

lNA

CD19-positive

Bcells

Currently

unknown

[131]

Omalizumab

Xolair�

IgE

Humanized

IgG1

2003

Asthma

IgElevelsand

bodyweight

stratified,s.c.

>0.5

mg/kg,

linear,26days

78±32ml/kg

62%

IgE

Currently

unknown

[43]

Palivizumab

Synagis�

Respiratory

syncytialvirus

(RSV)Fprotein

Humanized

IgG1

1998

Preventionof

seriouslower

respiratory

tract

disease

causedby

RSVin

pediatric

patients

mg/kg,i.m.

19--27days

3.99l

NA

RSV

Yes

[132]

Panitumumab

Vectibix�

EGFR

Human

IgG2

2006

Colorectalcancer

mg/kg,i.v.

Nonlinear,7.5

days

at6mg/kgq2w

3.66l(V

c),

2.58l(V

P)

NA

Skin

rash

Yes

[40]

Ranitumumab

Lucentis�

VEGF

Humanized

IgG1Fab

2006

Maculardegeneration

i.t.v.

9days

3l

NA

Centerpoint

thickness

Currently

unknown

[133]

Rituximab

Rituxan�

CD20

Chim

ericIgG1

1997

Non-Hodgkin’s

lymphoma,rheumatoid

arthritis

mgormg/m

2,

i.v.,

Nonlinear,22days

(NHL)

18days

(RA)

3.1

l(V

c)

NA

Bcell

Currently

unknown

[134]

Tocilizumab

Actemra

�IL-6

receptor

Humanized

IgG1

2010

Rheumatoid

arthritis

mg/kg,i.v.

Nonlinear8--14days

6.4

l(3.5

lVc,

2.9

lVp)

NA

CRP,rheumatoid

factor,

ESR,SAAand

increases

inhemoglobin

Currently

unknown

[135]

Tositumomab

andiodine

I131

tositumomab

Bexxar�

CD20

MurineIgG2

2003

Anti-neoplastic

radioim

munotherapeutics

i.v.

Nonlinear27h

(28--117h)

LargerV

NA

CD20

Currently

unknown

[136]

Trastuzumab

Herceptin�

HER2

Humanized

IgG1

1998

Her2

+metastatic

breast

cancer

mg/kg,i.v.

18--27days

3.02l(V

c)

3.10l(V

p)

NA

Currently

unknown

Currently

unknown

[137]

Ustekinumab

Stelara

�p40subunit

inIL-12/23

Human

2005

Moderate

tosevere

psoriasis

Bodyweight

stratifieds.c.

15--46days

56.1

to82.1

ml/kg(V

z)

57.2%

IL12/23

Currently

unknown

[138]


algrowth


sedim



KRAS:V-Ki-ras2


H:Lactate

dehydrogenase;MMP:Matrixmetalloproteinase;NA:Notapplicable;PD:Pharm



every


arthritis;RANKL:

ReceptoractivatorofnuclearfactorkappaBligand;

RSV:Respiratory


amyloid


Tumornecrosisfactoralpha;uNTX/cr:Urinary-N-telopeptide/creatinineratio;V:Volumeofdistribution;Vc:Volumeofdistributionforcentral

compartment;VEGF:

Vascularendothelialgrowth





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Table

2.Comparingthepharm

aco

kinetics

andpharm

aco

dynamicsofmonoclonalantibodiesandsm

allmolecu

ledrugs[1,75,110,50].

Small-m

olecu

le

drugs

Monoclonalantibodies

Targetis

soluble

antigen,

endogenous

levelis

low

Targetis

soluble

antigen,

endogenous

levelis

high

Targetis

cell-m

embrane

boundantigen

Targetis

cell-m

embrane

boundantigen

thatisinternalize

d

anddownregulated

Targetis

cell-m

embrane/tissu

e

boundantigen

thatcanbesh

ed

Pharm

acokinetics

Bindinggenerally

nonspecific(canaffect

multiple

enzymes)

Bindingvery

specificfortargetprotein

orantigen

Plasm

aprotein

binding

isanim

portantfactor

forPKandDDI

interpretations

Noplasm

aprotein

binding

Usually

linearPK

NonlinearPK

problematic

LinearPK

NonlinearPK

Relatively

short

t 1/2

Longt 1/2

Low

dose:short

t 1/2

Highdose:longt 1/2

Notalways

available

inorally

administered

form

Needparenteraldosing.s.c.

ori.m.ispossible

Metabolism

byP450s

orotherenzymes

Metabolism

bynonspecific

clearance

mechanisms.

NoP450sinvolved

Metabolism

by

specificandnonspecific

clearance

mechanisms.

NoP450sinvolved

Renalclearance

often

important

mAbs:

Norenalclearance

ofintact

antibody.

Maybeclearedbydamagedkidneys

Antibodyfragmentmightbeelim

inatedbyrenalclearance

Bindingto

tissues,

highVd

Distributionusually

limitedto

bloodandextracellularspace

Pharm

acodynamics

Intraandextracellular

targets

Poly-pharm

acology

maybeseen

Off-targettoxiceffects

maybeobserved

Typically

onlyextracellulartargets

withhighaffinity

Specificbindto

target.Limitedpoly-pharm

acology

Toxicity

usually

because

ofexaggeratedpharm

acologyandim

munogenicity

PK/PD

relationship

PKusually

independentofPD

PKoftenindependentofPD

PKoftendependentofPD

DDI:Drug--d

ruginteraction;i.m.:Intramuscular;mAbs:Monoclonalantibodies;

P450:CytochromeP450;PD:Pharm


acokinetic(s);s.c.:Subcutaneous;

Vd:Volumeofdistribution.



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of mAbs is relatively small due to their high molecular weightand poor lipophilicity. Typical values for the volume of distri-bution of mAbs in the central compartment (Vc) and thesteady-state volume (Vss) in humans are in the range of2 -- 3 l and 3.5 -- 7 l, respectively [1,6]. These values indicatethat distribution of mAbs is restricted to the blood streamand extracellular spaces. A low tissue:blood ratio is observedconsistently for most mAbs, typically ranging from 0.1 to0.5 [7,8]. Since the blood--brain barrier anatomically protectsthe central nervous system, mAbs have very limited penetra-tion to the brain and cerebrospinal fluid (CSF). Levels ofboth endogenous and therapeutic IgGs in CSF are in therange of only approximately 0.1 -- 1% of their respectiveserum levels [9].

The volume of distribution for some mAbs is influenced bymany other factors. These include the binding affinity, kinet-ics of antigen--mAb complex formation/dissociation, antigendistribution and receptor turnover kinetics (i.e., expressionlevel and turnover rate) for specific or nonspecific bind-ing [10,11]. For example, the tissue:blood concentration ratiosfor some mAbs against endothelial antigens are greaterthan 1, which has implications that the volume of distributionwould be 15-fold higher than the plasma volume [11].

Additionally, in contrast to a constant volume of distributionoften seen in small-molecule drugs, some mAbs exhibit dosedependency due to internalization of the antigen--mAb com-plex. Thus, a pronounced dose-dependent distribution wasobserved for the murine analog of efalizumab in mice thatcorrelated with dose-dependent tissue:blood concentrationratios for liver, spleen, bone marrow and lymph node [12].

FcRn is another factor that mediates the transport of IgGsfrom plasma to the interstitial fluid of tissues and across pla-cental barriers [13] or the vectorial transport of IgGs into thelumen of the intestine [13,14] and the lung [13,15]. However,the effects of FcRn on the tissue distribution of mAbs arenot fully understood. Recently, Yeung et al. found that ananti-vascular endothelial growth factor (VEGF) mAb Fc vari-ant with increased human FcRn-binding affinity had superiorin vivo potency in the xenograft mouse model compared withcorresponding WT anti-VEGF mAb, despite similar clearancein mice, potentially due to species-specific FcRn-bindingeffects [16].

The distribution of mAbs in tumors may be different fromnormal tissues due to a complex penetration process. Thisprocess involves plasma distribution and clearance, bloodflow through the tumor, extravasation across tumor

Antigenbinding

site

Antigenbinding

site

Fv

Fab

Fc

CH1

CH2

CH3

CL

VH VLVariableregions

Constantregions

Key Complementarity Determining Regions (CDRs)

Disulfide bond

Hinge

Figure 1. IgG1 antibody structure. Antigen is bound via the variable range of the antibody, whereas the Fc part of the IgG

determines the mode of action (also called effector function).CHn: Constant heavy chain; CL: Constant light chain; Fab: Antigen-binding fraction; Fc: Crystallizable fraction; Fv: Variable fraction; H-chain: Heavy chain

consisting of VH, CH1, CH2, CH3; L-chain: Light chain consisting of VL, CL; VH: Variable heavy chain; VL: Variable light chain.



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capillaries, convection, diffusion and binding within tumorinterstitium, and internalization and catabolism within thetumor cells. Multiple factors may influence distribution ofmAbs in tumors such as dose, diffusivity, permeability, affin-ity, antigen density and molecule size [17-19]. Scheidhauer et al.showed that 131I-labeled rituximab had decreasing ratios oftissue-to-whole-body radioactivity over time in normal organscompared with increasing ratios in tumors. This was the evi-dence of specific mAb binding [20].The relationship between the affinity of mAb for its antigen

and tumor uptake is complex. A decreased affinity is generallyconsidered undesirable. Several studies in animals showed thattumor uptake of mAbs correlated with affinity of mAbs.However, the intensity of tumor uptake of the anti-CD44 mAbs was inversely related to the affinity of the anti-CD44 mAb for its target antigen (CD44 is a cell-surfaceglycoprotein involved in cell--cell interactions, cell adhesionand migration) [21]. The hypothesis was that very high-affinity interactions between mAbs and tumor antigens mightimpair efficient penetration of the mAbs into the tumor [22].Therefore, there may be an optimal binding affinity for themAbs against the tumor antigens. A balance between the asso-ciation constant and dissociation constant determines theoptimal binding affinity. To attain maximal exposure intumor, the antibody--antigen dissociation kinetics should beslower than antigen turnover kinetics [23].

3.2.2 Antibody clearanceAb clearance primarily happens by catabolism. The catabo-lized peptide fragments and amino acids can be recycled foruse as an energy resource or for de novo protein synthesis.The small molecular weight fragments of mAbs (e.g., Faband Fv) can be filtered through the glomerulus and reab-sorbed and/or metabolized by proximal tubular cells of thenephron [1]. Therapeutic mAbs often exhibit two distinct cat-abolic pathways: i) a nonspecific clearance pathway mediatedby interaction between the Fc region of the mAb and Fcreceptors and ii) a specific clearance pathway mediated bythe specific interaction between the Fab region of the mAband its antigenic targets. The specific clearance pathway canbe saturable, depending on the dose of mAb and the expres-sion level of the target. However, the nonspecific pathwayhas a large capacity and clearance values associated with thispathway are generally linear in the therapeutic dose range of1 -- 20 mg/kg for most marketed mAbs.IgGs have a longer half-life of around 21 days compared

with other isotypes (IgA: 6 days; IgE: 2.5 days; IgM: 5 days;IgD: 3 days) with low clearance values of about 3 -- 5 ml/day/kg in humans in the linear dose range [24]. The low clear-ance may be due to the protection provided by the FcRn, aheterodimer comprising a b2-microglobulin (b2 m) lightchain and a major histocompatibility complex class I-likeheavy chain [13,25-27]. FcRn is ubiquitously expressed in cellsand tissues including vascular endothelium, professionalantigen-presenting cells, adult gut, blood--brain barrier,

kidney, lung and others [13]. Several studies have shown thatIgG clearance in b2 m knockout mice [25,26] and FcRn-heavy chain knockout mice [28] increased by 10- to 15-foldwith no changes in the elimination of other Igs. Other studiesdemonstrated that the half-life of IgGs depends on its affinityto FcRn [29-35].

Murine mAbs have shorter serum half-lives (1 -- 2 days) inhumans [36], possibly due to their low binding affinity to thehuman FcRn. Human FcRn binds human, rabbit and guineapig IgG but not rat, mouse, sheep and bovine IgG; murineFcRn binds IgGs from all these species [37]. Interestingly, thebinding affinity of human IgG to murine FcRn is greaterthan the binding of its murine analog [33]. This suggestspotential limitations of using mice as preclinical models forevaluation of PK and efficacy of human mAbs.

The interaction of FcRn with IgG is strictly pH dependent;FcRn binds to IgG at acidic pH (6.0) in the endosome andreleases IgG at physiological pH (7.4) [38]. Free IgG then pro-ceeds to the lysosome and undergoes proteolysis. Recent stud-ies demonstrate that a low binding affinity of FcRn to IgG atpH 7.4 is just as important as the increased binding affinity atpH 6.0 for decreasing clearance of mAbs [34,35]. Additionalfactors, such as association and dissociation kinetics of IgG/FcRn interaction at pH 6.0 and pH 7.4, also need to be con-sidered when determining the effects of binding affinity ofFcRn to IgG on the PK of mAbs.

Of note, the impact of FcRn-binding modulation on clear-ance of mAbs also depends on the relative contribution of theFcRn-mediated salvage pathway to overall clearance versusother elimination mechanisms. For instance, if binding to tar-get and subsequent catabolism are the dominant clearancepathway for a particular mAb, improved FcRn-binding char-acteristics may have only a marginal effect on extending thehalf-life of that mAb.

In addition to the nonspecific clearance pathway, mAbsmay also be eliminated through interaction with their targets(i.e., specific clearance pathway), which can be cell bound orsoluble (Table 2, Figure 2). Depending on the expression leveland the turnover rate of the targets, the specific clearance ofmAbs could be nonlinear at low doses when the targets arenot saturated and approach linear range at higher doseswhen the targets are saturated. Therefore, at low doses,mAbs show a shorter half-life and a faster clearance. As thedose increases, the half-life gradually increases and the clear-ance gradually decreases to a constant value [39]. Thus, toavoid wide fluctuations and high peak-to-trough concentra-tion ratios in the nonlinear range, most clinically accessiblemAbs have linear PK at therapeutic doses. One such exampleis panitumumab. When doses of panitumumab are above2 mg/kg, its exposure increases in an approximately dose-proportional manner. Therefore, to keep panitumumab PKin the linear range, it is administered at a dose level of6 mg/kg every 14 days [40,39].

mAbs against soluble antigens with low endogenouslevels (such as TNF-a, IFN-a, VEGF, IL-5) have



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dose-independent linear clearance. For example, linear PKwas observed for a humanized mAb directed to humanIL-5 following i.v. administration of across a 6000-fold doserange (0.05 -- 300 mg/kg) in cynomolgus monkeys [41]. Ada-limumab, an mAb against TNF-a, has linear PK in humans.The mean total serum clearance and the estimated meanterminal half-life of adalimumab range from 0.012 to0.017 l/h and 10.0 to 13.6 days, respectively, with an overallmean half-life of 12 days [42]. However, Abs against solubleantigens with high endogenous levels (such as IgE) exhibitnonlinear PK. Omalizumab has a linear PK only at dosesgreater than 0.5 mg/kg [43].

Dose-dependent clearance and half-life are more com-monly observed in mAbs that interact with cell membrane-expressed antigens. The binding affinity, antigen density andantigen turnover rate may influence the receptor-mediated elimination. Koon et al. demonstrated a stronginverse correlation between cellular expression of CD25+

and apparent half-life of daclizumab (an mAb specificallybinding to CD25) [44]. In patients with advanced tumorsoverexpressing EGFRs, cetuximab, an anti-epidermal growthfactor receptor (EGFR) mAb, had an approximately twofoldfaster clearance at a dose of 100 mg/m2 compared with thedose of 400 mg/m2 (0.837 vs 0.374 l/day) [45]. The disposi-tion of murine antihuman CD3 Abs may be determined bythe disappearance of their target antigens [46]. In addition,Ng et al. demonstrated that anti-CD4 mAb had approxi-mately fivefold faster total clearance at a dose of 1 mg/kg compared with the dose of 10 mg/kg (7.8 ± 0.6 vs37.4 ± 2.4 ml/day/kg) in healthy volunteers. This suggestedthat the receptor-mediated clearance was greater at the lowerdose since nonspecific clearance is constant across doselevels [47]. Using target-mediated drug disposition (TMDD)

model, Ng et al. reported that receptor-mediated clearancecontributed 41.7, 27.1 and 8.69% of total clearance at doselevels of 1, 5 and 10 mg/kg, respectively [47].

When the expression level of a target (i.e., antigen density)is modulated by an mAb, it leads to a time-dependent PK ofthat mAb. Serum concentration levels of rituximab, a chime-ric anti-CD20 mAb, were inversely correlated with tumor sizeand the number of circulating B cells in patients with non-Hodgkin’s lymphoma (NHL) [48]. After the first dose of ritux-imab, target B cells were depleted. As a result, the clearanceevaluated in the following treatment cycles was significantlyreduced compared with the first cycle (approximately fivefolddifferences) [49].

3.2.3 Other factors impacting the disposition of mAbsBesides the mechanisms discussed above, several otherfactors may play a role in determining the disposition ofmAbs [1,50-52]. These include immunogenicity of the Ab, gly-cosylation, effector function, off-target binding, charge, con-comitant medications, demographic factors, disease statusand specific population.

3.2.3.1 Immunogenicity of the AbAll currently available mAbs have exhibited some level ofimmunogenicity in humans. In general, murine mAbs aremore immunogenic than chimeric, humanized and humanmAbs [1]. From the PD perspective, immunogenicity can beeither non-neutralizing or neutralizing [53]. While non-neutralizing anti-drug antibodies (ADAs) may not decreasethe activity of mAbs, neutralizing ADAs can decrease theactivity of mAbs. An ADA, if it is a clearing or sustainingADA, may also alter clearance, plasma half-life and tissuedistribution of mAbs. Of note, the impact of ADAs on PK

Cell-bound antigenSoluble antigen Cell-bound antigen(Internalization/down-modulation)

Cell-bound antigen(Target shedding)

Cell deathCell death

Figure 2. Antigens for therapeutic antibodies.



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and PD does not always correlate. In patients with rheuma-toid arthritis (RA), adalimumab has a faster clearance withalteration in its PK due to the formation of ADAs alongwith neutralization of the antigen-binding domain [54]. Thiscould result in a loss of efficacy and impede repeated admin-istration of adalimumab [54]. ADAs can also increase the clear-ance of infliximab and result in lower trough concentrationsin patients with RA [55,56], spondyloarthritis [56], ankylosingspondylitis [57], ulcerative colitis [58] and inflammatory boweldiseases [59]. This could explain the nonresponse or loss ofresponse to treatment with infliximab in some patients [55-59].Levels of ADA are usually measured using enzyme-

linked immunosorbent assay (ELISA). Thus, the incidence ofADA for a given mAb can be influenced by the sensitivityand specificity of the assay [60]. Additionally, the results ofan assay may also be influenced by other factors includingsample handling, timing of sample collection, concomitantmedications (see discussion in 3.2.3.6) and the underly-ing disease [60]. For example, the incidence of anti-infliximabantibodies was reduced in patients with RA or spondyloarthritiswhen they were concomitantly treated with methotrexate(MTX). By contrast, other disease-modifying anti-rheumaticdrugs and prednisolone had no effect on the incidence ofanti-infliximab antibodies [55,56]. Bendtzen et al. also foundthat the high baseline activity of RA was associated withthe development of anti-infliximab antibodies [55]. Thus, thedirect comparison of the incidence of ADA for a specificmAb with the incidence of ADA for other mAb maybe misleading.

3.2.3.2 The degree and nature of Ab glycosylationConflicting results have been reported in the literature on theeffects of glycosylation on PK of mAbs. Glycosylation of IgGaffects its half-life in mice; removing the terminal sugars (sialicacid and galactose) significantly prolongs the half-life ofIgG2a due to slower uptake and degradation by lectin recep-tors in the liver [61]. However, a recent study demonstratedthat a humanized anti-amyloid beta (Ab) peptide mAb withdifferent glycans in the Fc region had the same clearance inmice [62]. In addition, the mAbs produced in Chinese hamsterovary (CHO) cell line or Escherichia coli (E. coli) have similarPK, although they have different levels of glycosylation(unpublished data at Genentech, Inc.).

3.2.3.3 Effector functionIf mAbs bind to soluble targets, they form soluble immunecomplexes. Depending on their size, these immune complexescan promote binding to the low-affinity FcgRII or FcgRIII.Once the immune complexes have been engaged by theFcgRs, the complexes are internalized by phagocytic cells. Iflevels of target are very low, changing binding affinity toFcg receptors may not affect PK of mAbs since the contribu-tion of the target-mediated clearance to the total clearance issmall. By contrast, if levels of target are high, changingbinding affinity to Fcg receptors will affect PK of mAbs.

For example, the anti-IgE mAb (IgE is a soluble target withhigh endogenous levels) with reduced binding affinity toFcg receptor had a slower clearance compared with WTanti-IgE mAb in cynomolgus monkeys [63].

When mAbs bind to cell-bound targets, the target cells canbe eliminated by ADCC through binding to the Fcg receptorson natural killer cells. Similar to soluble targets, if expressionlevels of cell-bound target are very low, changing bindingaffinity to Fcg receptors may not affect PK of mAbs. By con-trast, if expression levels of cell-bound targets are high, chang-ing binding affinity to Fcg receptors could affect PK of mAbs.For example, with a greatly reduced binding affinity to Fcgreceptor, levels of the Fc mutant (G4 variant) were approxi-mately two- to threefold higher than those of the Campath-1H WT Fc (a humanized mAb that reacts with CD52 presenton human lymphoid and myeloid cells) [64].

3.2.3.4 Off-target bindingAlthough specificity to their targets is a major characteristic ofmAbs, they may have off-target binding that may result in afaster clearance. Anti-respiratory syncytial virus mAb A4b4,developed by affinity maturation of palivizumab, had poorPK in rats and cynomolgus monkeys due to broad nonspecifictissue binding and sequestration [65]. The fast elimination of ahumanized antihuman amyloid beta peptide mAb, anti-AbAb2, in cynomolgus monkeys was linked to off-target bindingto cynomolgus monkey fibrinogen [66]. In addition, a human-ized anti-fibroblast growth factor receptor 4 (FGFR4) mAbhad fast clearance in mice that was attributable to binding tomouse complement component 3 (C3) [67].

3.2.3.5 ChargeDeliberate modification of the isoelectric point (pI) of an Abby approximately one pI unit or more can lead to noticeabledifferences in the PK of an intact Ab [68-70]. Using a human-ized anti-IL-6 receptor IgG1 as an example, Igawa et al.showed that lowering the pI point from 9.2 to 7.2 by engi-neering the V region reduced the IgG elimination in cyno-molgus monkeys [71]. By contrast, minor changes in thenature of ionic charge resulting in pI differences of less thanapproximately one pI unit are not expected to affect the bio-logical function of mAbs, including tissue retention andwhole blood clearance [68,69]. Thus, such changes in ioniccharge of mAbs may not require extensive PK comparabilityassessments [69,70].

3.2.3.6 Concomitant medicationsPK-related drug interactions are generally not expected formAbs. The classical drug--drug interactions, which occurthrough effects on enzyme systems such as the CYP450 sys-tem and transporters, are not anticipated for mAbs [72]. How-ever, there are a few exceptions. Some cytokines significantlyaffect the expression of CYP450 enzymes and can influenceexpression of drug transporters [72]. For example, cytokines,such as TNF-a, IL-6 IL-2 receptor and IL-1b, can



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downregulate the expression of multiple CYP450 enzymes inprimary human hepatocytes [72]. Therefore, the metabolismof a small-molecule drug may be indirectly affected bycertain concomitantly administered mAbs through cytokine-induced inhibition of the CYP450 superfamily. It wasproposed that the decreased clearance of ciclosporin incotreatment with basiliximab in pediatric renal transplantpatients could be caused by alteration of the CYP system,mediated by the IL-2 receptor -- the target of basiliximab [6].Some small-molecule drugs may influence the PK of concom-itantly administered mAbs by attenuating immune responseto the mAbs (development of ADA) and the expression ofFcg receptors. For example, in patients with RA, MTXreduces the apparent clearance of adalimumab after singleand multiple doses by 29 and 44%, respectively [54]. Thisobservation is consistent with the low incidence of ADA inpatients concomitantly receiving MTX and adalimumab. Inaddition, azathioprine and mycophenolate mofetil reducethe clearance of basiliximab by approximately 22 and 51%,respectively [73]. These findings could be explained by theeffects of small-molecule drugs on the expression levels ofFcg receptors. The fact that MTX can significantly impactthe expression profiles of FcgRI on monocytes in patientswith RA further supports this hypothesis [74].

3.2.3.7 Demographic factors and disease statusAnalysis of population PK has routinely been used to quantifythe covariate effects of a population on the PK parameters of adrug [75]. Body size is often a statistically significant covariateinfluencing clearance and/or volume of distribution (Vd) of adrug; yet it is not always a clinically relevant covariate [6,51].For example, population PK analyses of golimumab showedthat heavy patients have higher apparent clearance of golimu-mab [76]. However, no meaningful differences in clinical effi-cacy of golimumab were observed when different weightsubgroups were compared [76]. Thus, there is no need toadjust the dose of golimumab based on a patient’s bodyweight. Albumin, which is often an indicator of disease status,is also a significant covariate affecting clearance for severalmAbs, such as infliximab, pertuzumab and bevacizumab [51].It is believed that albumin, which binds to FcRn at differentsites than IgG, is an indicator of increased number ofFcRn [51,77]. Nevertheless, the correlation between the levelsof albumin and the clearance of pertuzumab and bevacizumabwas moderate and dose modification was not recom-mended [51]. Regardless, it has been suggested that serum lev-els of albumin are predictive factor for PK of infliximab andclinical response to infliximab in patients with ulcerativecolitis [77].

3.2.3.8 Specific populationRenal and hepatic impairment is not likely to significantlyalter PK of mAbs since kidneys and liver are not involved inthe disposition of mAbs. According to the Food and DrugAdministration (FDA) guidance, assessment of PK of mAbs

in these two special populations is not necessary [78,79]. How-ever, several studies of PK of mAbs were conducted in pediat-ric patients. Disposition of infliximab [80], bevacizumab [81]

and cetuximab [82] in pediatric patients seems to be similarto that in adults. Based on population PK analysis of omalizu-mab, no dose adjustments are necessary in patients withasthma based on age (12 -- 76 years), race, ethnicity or gen-der [43]. The PK of mAbs in pregnant women and nursingmothers is not well established due to the lack of adequateand well-controlled studies. However, it is believed thatsome PK parameters, such as Vd and clearance, aregestation-stage dependent [83]. In addition, changing PKduring the reproductive cycle has been observed in rats foran mAb against phencyclldine [84]. Since IgG is excreted inhuman breast milk, it is expected that therapeutic mAbs willalso be excreted into human breast milk. Levels of omalizu-mab in breast milk were 1.5% of those in maternal blood infemale cynomolgus monkeys receiving a subcutaneous doseof 75 mg/kg/week omalizumab [43].

4. Pharmacodynamics

PD endpoints can be biomarkers or clinical endpoints.A biomarker is a characteristic that can be objectively mea-sured and evaluated as an indicator of normal and disease pro-cesses or pharmacological responses to a therapeuticintervention. Biomarkers can be specific cells, molecules,genes, gene products, enzymes or hormones. Based on theirapplication, biomarkers can be classified as diagnostic, stagingof disease, disease prognostic or biomarkers for monitoringthe clinical response to an intervention.

Diagnostic and prognostic biomarkers are the most well-studied biomarkers in oncology. The joint approval ofHerceptin� and HercepTest� was the first example of a diag-nostic biomarker for a specific therapy. Another example ispanitumumab, an anti-EGFR mAb. KRAS mutation in thetumors of patients with metastatic colorectal cancer is a majorpredictive biomarker of resistance to panitumumab. Thus,panitumumab was approved to treat patients with the WTrather than the mutant KRAS [85].

Biomarkers are also used to monitor the clinical and bio-logical responses to treatment. For example, polymorphismin FcgRIIIA was associated with a favorable clinical responseto treatment with rituximab in patients with NHL [86,87]. Lev-els of free IgE are used as a biomarker for the treatment ofasthma with omalizumab. In patients with asthma whoresponded to treatment with omalizumab, the levels of freeIgE in serum were reduced in a dose-dependent mannerwithin 1 h following the first dose of omalizumab and thoselower levels were maintained between doses [43].

5. PK/PD relationship

As discussed previously, mAbs are target specific and thetarget-mediated clearance pathway plays an important role



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in their elimination. The changes in expression levels of targetfollowing therapeutic intervention can result in changes in thePK and subsequently the PD profiles of the mAb. Therefore,unlike small-molecule drugs, PK of mAbs is often dependenton PD.The term ‘target-mediated drug disposition’ was first intro-

duced by Levy [88] to describe drugs with PK propertiesmarkedly influenced by binding to their target. Mager et al.then described an interdependent PK/PD model that accountsfor the PK of the drug, target dynamics and their inter-action [89], which was subsequently thoroughly investigatedfor application in mAbs [47,90-92]. A schematic representationof TMDD is provided in Figure 3. TMDD is most visible atlow levels of target and increases with increasing levels of theendogenous target. This model has been used to describePK/PD relationships for multiple mAbs, such as an anti-EGFR Ab 2F8 in cynomolgus monkeys [91] and an anti-a5b1integrin mAb (volociximab) in patients with cancer [92].PD biomarkers are markers of a certain pharmacological

response that are of particular interest in dose-optimizationstudies. PD biomarkers are sometimes directly or indirectlylinked to a clinical endpoint. They typically exhibit a time-course after administration of a drug, which is often directlyrelated to the time-course of drug concentrations in plasma,sometimes with a measurable delay. For this reason, exposure(i.e., PK)--response (i.e., PD) relationships can help establishthe dose range of a drug used in clinical trials intended toestablish efficacy. For example, the higher peak and troughconcentrations of rituximab correlate significantly with betterclinical responses in patients with low-grade NHL [48].

Similarly, better clinical response and minimal residualdisease in chronic lymphocytic leukemia correlated withhigher blood concentrations of alemtuzumab, a humanizedanti-CD52 mAb [93]. Therefore, understanding the PK/PD relationship is critical for predicting efficacy anddose optimization.

6. Bioanalytical approaches to quantify mAband its target

A reliable bioanalytical method for measuring an mAb and itstarget in circulation is important for characterization of theirPK and PD and for understanding the PK/PD relationships.An mAb and its target may exist in blood in multiple forms:as free mAb, free target or mono- and/or bivalent complexesof mAb/target [94,95]. In many instances, the pharmacologiceffect of an mAb is determined by free mAb, which is thefocus form of mAb from a PK/PD perspective. Ligand-binding assays (LBA), mainly immunoassays measuringantigen--antibody interactions, are mostly used for quantifica-tion of levels of mAbs and their targets. LBA could theoreti-cally measure free, bound or total forms of therapeuticmAbs depending on reagents, format and experimental condi-tions [94,95]. Antigen-capture assay, bridging assay (antigen-capture--antigen-detection), anti-idiotype antibody-captureassay, generic assay (anti-species-capture and detection) andcompetitive assay are the five most commonly usedLBAs [94,95]. However, target interference with their quantita-tion methods is rarely evaluated. Ternant et al. reported targetinterference on the serum levels for infliximab [96],

kcp

kpc

ka

In(t)

kel ksyn

koff

kon

kintkdeg

IVInfusion

Antibodyin depot

(Ad)

Antibodyin periphery

(Ap)

Antibodyin central

(C,Vc)

Receptor(R)

Antibody–receptorcomplex

(RC)

Figure 3. Schematic representation of target-mediated drug disposition (TMDD). Ad and Ap are the amount of the free (not

bound to a target) drug in the depot and periphery compartments; C, R and RC are the concentrations of the free (not bound

to the target) drug, the target and the drug--target complex, respectively, in the central (blood) compartment; ka, kel, kpc and

kcp are the absorption, linear elimination, plasma to periphery and periphery to plasma rate constants; kon, koff and kint are

the binding, dissociation and internalization (elimination of the complex) rate constants; kdeg and ksyn are the degeneration

(elimination of the target) and target production rate constants; Vc is the central compartment volume and In(t) is the

infusion rate.



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cetuximab [97] and bevacizumab [98]. The reported level ofendogenous soluble TNF-a was much lower than theexpected steady-state exposure of infliximab. Therefore, thelikelihood of interference of TNF-a on quantitation of inflix-imab was low at this level of target antigen; the same was alsotrue for cetuximab and bevacizumab [94]. However, under cer-tain circumstances, especially when levels of soluble targets arecomparable with those of therapeutic mAbs, circulating targetcould potentially interfere with quantitation of the drug andresult in confounding PK data.

Advances in analytical technologies and techniques have ledor will lead to the development of faster, more sensitive androbust analytical assays. One such method is high performanceliquid chromatography--tandem mass spectrometry for quanti-fication of total mAb [99]. A method described by Doucet et al.[100] is based on sample digestion while keeping the mAb in theform of immunoreactive fragments, followed by ELISA.

7. Prediction of mAb humanpharmacokinetics/pharmacodynamics basedon preclinical information

Prior to the first-in-human (FIH) clinical study, a number ofpreclinical in vivo and in vitro experiments are conducted toevaluate the PK/PD, safety and efficacy of a new drug candi-date. The objective of translational research at this stage is topredict PK/PD/safety outcomes in a target patient popula-tion, acknowledging the similarities and differences betweenpreclinical and clinical settings.

Over the years, many theories and approaches have beenproposed and used for scaling preclinical PK data to humans.Allometric scaling, based on a power law relationship betweensize of the body and physiological and anatomical parameters,is the simplest and most widely used approach [101-105]. Thephysiologically based PK modeling (PBPK), species-invariant time method (Dedrick approach) [101] and nonlinearmixed-effect modeling population approach based on allome-try [102] have also been used for interspecies scaling of PK.While no single scaling method has been shown to definitivelypredict human PK in all cases, especially for small-molecule drugs, the PK for mAbs can be predicted reasonablywell. Most therapeutic mAbs bind to nonhuman primate anti-gens more often than to rodent antigens due to the greatersequence homology observed between nonhuman primatesand humans. The binding epitope, binding affinity to anti-gen, binding affinity to FcRn, tissue cross-reactivity profilesand disposition and elimination pathways of mAbs are similarin nonhuman primates and humans. It has recently beendemonstrated that clearance and distribution volume ofmAbs in humans can be reasonably projected based on datafrom nonhuman primates alone with a fixed scalingexponent [103-105].

Due to its complexity, any extrapolation of PD to humansrequires more thorough consideration than for PK. Little isknown about allometric relationships in PD parameters. It is

expected that the physiological turnover rate constants ofmost general structures and functions should be predictableamong species obeying allometric principles, whereas capacityand sensitivity tend to be similar across species [106]. Throughintegration of PK/PD modeling and interspecies scaling, thePD in humans may be predicted if the PK/PD relationshipis assumed to be similar between animal models andhumans [107,108]. For example, a PK/PD model was first devel-oped to optimize the dosing regimen of the mAb againstEGF/r3 using tumor-bearing nude mice as an animal modelof human disease [107]. This PK/PD model was subsequentlyintegrated with allometric scaling to calculate the dosingschedule required in a potential clinical trial to achieve aspecific effect [107].

In summary, species differences in antigen density,antigen--Ab binding and antigen kinetics, differences inFcRn binding between species, the immunogenicity and otherfactors must be considered during PK/PD scaling of an mAbfrom animals to humans.

8. FIH dose

The selection of the FIH dose for the first clinical trial of adrug candidate is based on combined knowledge of preclinicalPK, PD and safety. The binding specificity of mAb limits theselection of animal species for the preclinical toxicologicalevaluation to enable an FIH study. Safety evaluations aremostly performed in cynomolgus monkeys and rodents ifthe Ab cross-reacts with the target.

Even though many methods have been used to calculate thestarting dose in FIH trials, the FDA guidance [109] on selec-tion of starting dose is widely applied across the industry.Briefly, the ‘no-observed-adverse-effect level’ identified inthe most sensitive animal species is converted into a humanequivalent dose (HED) using an appropriate scaling factor.A safety factor is then applied to the HED to obtain themaximum-recommended starting dose (MRSD). In general,a safety factor of at least 10 is considered. The scaling factorcan be based on body surface area, body weight, dose or otherPK parameters, such as exposure and maximal or minimalconcentration. However, conversion factor for the body sur-face area, which gives the most conservative estimation ofthe HED, is widely used for anticancer agents. In addition,the human pharmacologically active dose (PAD) has alsobeen addressed in the FDA guidance, which mentions thatit is useful to compare human PAD with the MRSD; how-ever, few details are provided. The selection of the HED orPAD approach to determine FIH dose usually depends onthe potential mechanism of action and safety concerns associ-ated with therapeutic index for the mAbs. For example, it isoften recommended to assess the FIH dose based on a PADapproach for mAbs with high risk of immune stimulation ifthey directly interact with immune cells. Lately, the PK/PDmodeling approach has been used to support the design ofclinical trials, especially the FIH dosing rationale [110].



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Lowe et al. [111] proposed a four-step process for the anticipa-tion of a human dose for FIH trials: i) characterization ofexposure--response relationships in preclinical studies;ii) correction for interspecies differences; iii) prediction ofhuman PK; and iv) prediction of human dose--responses anddose selection for Phase I protocols. The differencesbetween animals and humans in affinity, potency, exposureand distribution have all been accounted for in this approach.The severe adverse events seen in the FIH study of an ago-

nist mAb against CD28 prompted the new European Medi-cines Agency (EMA) guidance for the FIH dose selection forcompounds with high risk, including mAbs [112]. The doseselection approach in the EMA guidance attempts to obtainthe minimum anticipated biological effect level (MABEL)by integrating all preclinical pharmacological, safety and effi-cacy data into a PK/PD modeling framework. This approachis extremely valuable for an mAb with high specificity to itstargets because toxicological effects are in many cases due toexaggerated pharmacology. However, the MABEL approachhas not been widely used for anticancer mAbs since there isconsiderably higher acceptance of toxicity to achieve thera-peutic benefit in the oncology setting. Starting doses of anti-cancer agents have traditionally been established with thegoal of escalating quickly to a maximum tolerated dose on agiven dosing regimen [113].Several approaches described above have been used in pre-

dicting the starting dose in FIH trials. Each approach has itsown advantages and disadvantages. Ultimately, selection of asuitable and safe starting dose should be based on integratedknowledge and scientific judgment.

9. Conclusion

The PK and PD of mAbs are often complicated because theydepend on both the structure of Abs and their targets. Thelong half-life and the pharmacological specificity are themost important characteristics for mAbs compared withsmall-molecule drugs (Table 2). mAbs directed against solubleantigens often exhibit linear PK, and mAbs directed againstcell-surface antigens often exhibit nonlinear PK. Many factorscan affect the PK of mAbs, including dose level, FcRn-binding affinity, target density, target turnover rate, bindingaffinity to target, immunogenicity, glycosylation, charges,other concomitantly administrated medicines, potential off-target binding, bioanalytical methods and others. Unlike thePK of small-molecule drugs, the PK of many mAbs oftendepends on PD. Thus, understanding the PK/PD relationshipof therapeutic mAbs may aid in clinical development,particularly in selecting doses for FIH and subsequentclinical studies.

10. Expert opinion

mAbs have become very attractive as therapeutics and willcontinue to be a focal area of drug discovery and

development. Several key determinants of PK of mAbs havebeen identified, validated and characterized through preclini-cal and clinical studies, as well as through the application ofmechanistic mathematical modeling. Some of these determi-nants include mAb--FcRn interaction, rates of fluid--phaseendocytosis and convection, affinity to targets, expressionand turnover rate of targets, and rate of endocytosis ofAb--target complex. However, there is growing evidence ofunexpected rapid clearance of mAbs [65-67,114]; some of thesecannot yet be explained based on the existing knowledge ofPK of mAbs [114].A deeper understanding of the relationshipbetween antibody structure and PK is needed to resolvethis issue.

Target-mediated disposition via specific (i.e., antigen) ornonspecific (i.e., Fc receptors) processes is probably themost important feature of PK and PD of mAbs. The com-plex interdependent nature between the PK and PD ofmAb can be difficult to understand. Therefore, correlatingPK with PD will help provide a holistic interpretation ofthe PK and PD of mAbs. Unfortunately, for many mAbs,the PK/PD relationship has not been elucidated thoroughlydue to a lack of knowledge of the target system or availabil-ity of appropriate laboratory tools and techniques. Thesegaps significantly limit our capability to translate lessonslearned from one development stage to the next (i.e., pre-clinical to FIH and early phase clinical to late phase clini-cal). For soluble antigens, it is widely accepted that, ondosing of mAbs, levels of free antigen could be a valid bio-marker that correlates well with drug effect. However, mea-suring levels of free antigen at therapeutic doses of mAbscould be a challenging task; a sensitive assay is required forsuch quantification. In addition, many mAbs have muchhigher affinity to their antigens compared with native poly-clonal Abs. Therefore, the binding kinetics could be veryrapid and hard to capture. Future improvements in assaysensitivity and study design to evaluate the time-course ofthe binding process could significantly aid in characterizingfree-antigen profiles. On the other hand, characterizationof the interaction between mAb and membrane-boundantigens is facing other difficulties. Since the Ab-antigenbinding, complex internalization and further downstreamdegradation and recycling process happen at the cellularlevel, they are much less accessible by conventional techni-ques. Further development and refinement of confocalimaging and other methods may provide a better way toassess these kinetic events in a more quantitative mannerand produce meaningful results. From the perspective ofsystem biology, the PBPK approach continues to be thestandard approach to evaluate PK of mAbs, expression levelof antigens and antigen turnover rate in tissue throughoutthe whole body, and correlation between these elements.Different variations of PBPK model will be developed, pos-sibly with an emphasis on particular disease-related tissueswhen in-depth knowledge regarding antigen dynamics inthese tissues has been acquired. Mechanism-based PK/PD



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modeling using various mathematical and statistical toolsremains an invaluable approach to help bridge the gap inthe translational research of mAbs. It can help not onlyin understanding the PK, PD and PK/PD relationshipbut also in designing further studies of mAbs in theirtarget populations.

We are still in the early stage of developing mAbsand fully understanding their complex PK/PD behavior.It is, therefore, important to advance our understanding

of PK and PD of mAbs from a basic research standpoint.In addition, it is equally important to apply mechanisticPK/PD models to interpret the experimental results andfacilitate efforts to predict safety and efficacy of mAbs.

Declaration of interest

R Deng, S Prabhu and S Iyer are all employees of Genentechwhile F Jin is an employee of Merck & Co.

BibliographyPapers of special note have been highlighted as

either of interest (�) or of considerable interest(��) to readers.

1. Lobo ED, Hansen RJ, Balthasar JP.

Antibody pharmacokinetics and

pharmacodynamics. J Pharm Sci

2004;93(11):2645-68.. It is the first comprehensive review

paper on antibody pharmacokinetics

and pharmacodynamics and provides

an overview of many of the

complexities associated with antibody

pharmacokinetics

and pharmacodynamics.

2. Subramanian GM, Cronin PW, Poley G,

et al. A phase 1 study of PAmAb, a fully

human monoclonal antibody against

Bacillus anthracis protective antigen, in

healthy volunteers. Clin Infect Dis

2005;41(1):12-20

3. Wang W, Wang EQ, Balthasar JP.

Monoclonal antibody pharmacokinetics

and pharmacodynamics.

Clin Pharmacol Ther 2008;84(5):548-58

4. Frost GI. Recombinant human

hyaluronidase (rHuPH20): an enabling

platform for subcutaneous drug and fluid

administration. Expert Opin Drug Deliv

2007;4(4):427-40

5. Ratner M. Roche plans for more

convenient-to-use Herceptin and

Rituxan. Nat Biotechnol 2010;28(4):298

6. Keizer RJ, Huitema AD, Schellens JH,

et al. Clinical pharmacokinetics of

therapeutic monoclonal antibodies.

Clin Pharmacokinet 2010;49(8):493-507

7. Baxter LT, Zhu H, Mackensen DG,

Jain RK. Physiologically based

pharmacokinetic model for specific and

nonspecific monoclonal antibodies and

fragments in normal tissues and human

tumor xenografts in nude mice.

Cancer Res 1994;54(6):1517-28

8. Berger MA, Masters GR, Singleton J,

et al. Pharmacokinetics, biodistribution,

and radioimmunotherapy with

monoclonal antibody 776.1 in a murine

model of human ovarian cancer.

Cancer Biother Radiopharm

2005;20(6):589-602

9. Wurster U, Haas J. Passage of

intravenous immunoglobulin and

interaction with the CNS. J Neurol

Neurosurg Psychiatry

1994;57(Suppl):21-5

10. Kairemo KJ, Lappalainen AK, Kaapa E,

et al. In vivo detection of intervertebral

disk injury using a radiolabeled

monoclonal antibody against keratan

sulfate. J Nucl Med 2001;42(3):476-82

11. Danilov SM, Gavrilyuk VD, Franke FE,

et al. Lung uptake of antibodies to

endothelial antigens: key determinants of

vascular immunotargeting. Am J Physiol

Lung Cell Mol Physiol

2001;280(6):L1335-47

12. Coffey GP, Fox JA, Pippig S, et al.

Tissue distribution and receptor-mediated

clearance of anti-CD11a antibody in

mice. Drug Metab Dispos

2005;33(5):623-9

13. Junghans RP. Finally! The Brambell

receptor (FcRB). Mediator of

transmission of immunity and protection

from catabolism for IgG. Immunol Res

1997;16(1):29-57. This article provides a historical

overview of FcRn and summarizes the

subsequent elaboration of the details of

the physiology and molecular biology

of this remarkable receptor system.

14. Dickinson BL, Badizadegan K, Wu Z,

et al. Bidirectional FcRn-dependent IgG

transport in a polarized human intestinal

epithelial cell line. J Clin Invest

1999;104(7):903-11

15. Spiekermann GM, Finn PW, Ward ES,

et al. Receptor-mediated

immunoglobulin G transport across

mucosal barriers in adult life: functional

expression of FcRn in the mammalian

lung. J Exp Med 2002;196(3):303-10

16. Yeung YA, Wu X, Reyes AE II, et al.

A therapeutic anti-VEGF antibody with

increased potency independent of

pharmacokinetic half-life. Cancer Res

2010;70(8):3269-77

17. Thurber GM, Schmidt MM,

Wittrup KD. Factors determining

antibody distribution in tumors.

Trends Pharmacol Sci 2008;29(2):57-61

18. Thurber GM, Schmidt MM,

Wittrup KD. Antibody tumor

penetration: transport opposed by

systemic and antigen-mediated clearance.

Adv Drug Deliv Rev

2008;60(12):1421-34

19. Reff ME, Heard C. A review of

modifications to recombinant antibodies:

attempt to increase efficacy in oncology

applications. Crit Rev Oncol Hematol

2001;40(1):25-35

20. Scheidhauer K, Wolf I, Baumgartl HJ,

et al. Biodistribution and kinetics of

(131)I-labelled anti-CD20 MAB

IDEC-C2B8 (rituximab) in relapsed

non-Hodgkin’s lymphoma. Eur J Nucl

Med Mol Imaging 2002;29(10):1276-82

21. Verel I, Heider KH, Siegmund M, et al.

Tumor targeting properties of

monoclonal antibodies with different

affinity for target antigen CD44V6 in

nude mice bearing head-and-neck cancer

xenografts. Int J Cancer

2002;99(3):396-402

22. Fujimori K, Covell DG, Fletcher JE,

Weinstein JN. A modeling analysis of

monoclonal antibody percolation through

tumors: a binding-site barrier.

J Nucl Med 1990;31(7):1191-8

23. Graff CP, Wittrup KD. Theoretical

analysis of antibody targeting of tumor

spheroids: importance of dosage for

penetration, and affinity for retention.

Cancer Res 2003;63:1288-96



Exp

ert O

pin.

Dru

g M

etab

. Tox

icol

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Sa

skat

chew

an o

n 05

/09/

12Fo

r pe

rson

al u

se o

nly.

24. Morell A, Terry WD, Waldmann TA.

Metabolic properties of IgG subclasses in

man. J Clin Invest 1970;49:673-80

25. Ghetie V, Hubbard JG, Kim JK, et al.

Abnormally short serum half-lives of IgG

in beta 2-microglobulin-deficient mice.

Eur J Immunol 1996;26(3):690-6

26. Junghans RP, Anderson CL. The

protection receptor for IgG catabolism is

the beta2-microglobulin-containing

neonatal intestinal transport receptor.

Proc Natl Acad Sci USA

1996;93(11):5512-16

27. Brambell F, Hemmings W, Morris I.

A theoretical model of gamma-globulin

catabolism. Nature 1964;203:1352-5

28. Roopenian DC, Christianson GJ,

Sproule TJ, et al. The MHC class I-like

IgG receptor controls perinatal IgG

transport, IgG homeostasis, and fate of

IgG-Fc-coupled drugs. J Immunol

2003;170(7):3528-33

29. Dall’Acqua WF, Kiener PA, Wu H.

Properties of human IgG1s engineered

for enhanced binding to the neonatal Fc

receptor (FcRn). J Biol Chem

2006;281(33):23514-24

30. Dall’Acqua WF, Woods RM, Ward ES,

et al. Increasing the affinity of a human

IgG1 for the neonatal Fc receptor:

biological consequences. J Immunol

2002;169(9):5171-80

31. Hinton PR, Johlfs MG, Xiong JM, et al.

Engineered human IgG antibodies with

longer serum half-lives in primates.

J Biol Chem 2004;279(8):6213-16

32. Hinton PR, Xiong JM, Johlfs MG, et al.

An engineered human IgG1 antibody

with longer serum half-life. J Immunol

2006;176(1):346-56

33. Petkova SB, Akilesh S, Sproule TJ, et al.

Enhanced half-life of genetically

engineered human IgG1 antibodies in a

humanized FcRn mouse model: potential

application in humorally mediated

autoimmune disease. Int Immunol

2006;18(12):1759-69

34. Yeung YA, Leabman MK, Marvin JS,

et al. Engineering human IgG1 affinity

to human neonatal Fc receptor: impact

of affinity improvement on

pharmacokinetics in primates. J Immunol

2009;182(12):7663-71

35. Deng R, Loyet KM, Lien S, et al.

Pharmacokinetics of humanized

monoclonal anti-tumor necrosis

factor-{alpha} antibody and its neonatal

Fc receptor variants in mice and

cynomolgus monkeys.

Drug Metab Dispos 2010;38(4):600-5

36. Dartois C, Freyer G, Michallet M, et al.

Exposure-effect population model of

inolimomab, a monoclonal antibody

administered in first-line treatment for

acute graft-versus-host disease.

Clin Pharmacokinet 2007;46:417-32

37 Ober RJ, Radu CG, Ghetie V, Ward ES.

Differences in promiscuity for

antibody-FcRn interactions across species:

implications for therapeutic antibodies.

Int Immunol 2001;13(12):1551-9

38. Roopenian DC, Akilesh S. FcRn: the

neonatal Fc receptor comes of age.

Nat Rev Immunol 2007;7(9):715-25

39. Yang BB, Lum P, Chen A, et al.

Pharmacokinetic and pharmacodynamic

perspectives on the clinical drug

development of panitumumab.

Clin Pharmacokinet 2010;49:729-40

40. Vectibix� (panitumumab): US

prescribing information. Amgen Inc.

Thounsand Oaks, CA, USA, 2011.

Available from: http://pi.amgen.com/

united_states/vectibix/vectibix_pi.pdf

[Last accessed 31 May 2011]

41. Zia-Amirhosseini P, Minthorn E,

Benincosa LJ, et al. Pharmacokinetics

and pharmacodynamics of SB-240563, a

humanized monoclonal antibody directed

to human interleukin-5, in monkeys.

J Pharmacol Exp Ther

1999;291(3):1060-7

42. den Broeder A, van de Putte L, Rau R,

et al. A single dose, placebo controlled

study of the fully human anti-tumor

necrosis factor-alpha antibody

adalimumab (D2E7) in patients with

rheumatoid arthritis. J Rheumatol

2002;29(11):2288-98

43. Xolair� (omalizumab): US prescribing

information. Genentech Inc, South San

Francisco, CA, USA & Novartis

Pharmaceuticals Corp, East Hanover, NJ,

USA,2006. Available from: http://www.

gene.com/gene/products/information/pdf/

xolair-prescribing.pdf [Last accessed

31 May 2011]

44. Koon HB, Severy P, Hagg DS, et al.

Antileukemic effect of daclizumab in

CD25 high-expressing leukemias and

impact of tumor burden on antibody

dosing. Leuk Res 2006;30(2):190-203

45. Erbitux� (cetuximab): US prescribing

information. Bristol-Myers Squibb Co,

Princeton, NJ,USA and Eli Lilly and Co,

Indianapolis, IN, USA, 2011. Available

from: http://packageinserts.bms.com/pi/

pi_erbitux.pdf [Last accessed 31 May

2011]

46. Meijer RT, Koopmans RP, ten Berge IJ,

Schellekens PT. Pharmacokinetics of

murine anti-human CD3 antibodies in

man are determined by the disappearance

of target antigen. J Pharmacol Exp Ther

2002;300(1):346-53

47. Ng CM, Stefanich E, Anand BS, et al.

Pharmacokinetics/pharmacodynamics of

nondepleting anti-CD4 monoclonal

antibody (TRX1) in healthy human

volunteers. Pharm Res

2006;23(1):95-103

48. Berinstein NL, Grillo-Lopez AJ,

White CA, et al. Association of serum

Rituximab (IDEC-C2B8) concentration

and anti-tumor response in the treatment

of recurrent low-grade or follicular

non-Hodgkin’s lymphoma. Ann Oncol

1998;9(9):995-1001

49. Li J, Levi M, Charoin J, et al. Rituximab

Exhibits A Long half-life based on a

population pharmacokinetic analysis in

Non-hodgkin’s Lymphoma (NHL)

Patients[ASH Annual Meeting]. Blood

2007;110(11):abstract No. 2371

50. Roskos LK, Davis CG, Schwab GM.

The clinical pharmacology of therapeutic

monoclonal antibodies. Drug Dev Res

2004;61:108-20

51. Dirks NL, Meibohm B. Population

pharmacokinetics of therapeutic

monoclonal antibodies.

Clin Pharmacokinet 2010;49(10):633-59

52. Tabrizi MA, Tseng CM, Roskos LK.

Elimination mechanisms of therapeutic


Drug Discov Today 2006;11(1-2):81-8

53. Rosenberg AS, Worobec A. A risk-based

approach to immunogenicity of

therapeutic protein products, Part 1:

considering consequences of theimmune

response to a protein. BioPharm Int

2004;17:22-6. Available from: http://www.

biopharminternational.com/biopharm/

article/articleDetail.jsp?id=134110 [[Last

accessed 30 September 2011]

54. Humira� (adalimumab): US prescribing

information. Abbott Laboratories,

Chicago, IL, USA, 2011. Available from:

http://www.rxabbott.com/pdf/humira.pdf




Exp

ert O

pin.

Dru

g M

etab

. Tox

icol

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Sa

skat

chew

an o

n 05

/09/

12Fo

r pe

rson

al u

se o

nly.

55. Bendtzen K, Geborek P, Svenson M,

et al. Individualized monitoring of drug

bioavailability and immunogenicity in

rheumatoid arthritis patients treated with

the tumor necrosis factor alpha inhibitor

infliximab. Arthritis Rheum

2006;54:3782-9

56. Ducourau E, Mulleman D, Paintaud G,

et al. Antibodies toward infliximab are

associated with low infliximab

concentration at treatment initiation and

poor infliximab maintenance in

rheumatic diseases. Arthritis Res Ther

2011;13:R105

57. Xu Z, Seitz K, Fasanmade A, et al.

Population pharmacokinetics of

infliximab in patients with ankylosing

spondylitis. J Clin Pharmacol

2008;48:681-95

58. Fasanmade AA, Adedokun OJ, Ford J,

et al. Population pharmacokinetic

analysis of infliximab in patients with

ulcerative colitis. Eur J Clin Pharmacol

2009;65:1211-28

59. Ternant D, Aubourg A,

Magdelaine-Beuzelin C, et al. Infliximab

pharmacokinetics in inflammatory bowel

disease patients. Ther Drug Monit

2008;30:523-9

60. Guideline On Immunogenicity

Assessment Of Biotechnology-Derived

Therapeutic Proteins E, London,UK,

2007. Available from: http://www.ema.

europa.eu/docs/en_GB/document_library/

Scientific_guideline/2009/09/

WC500003946.pdf [Last accessed

30 September 2011]

61. Newkirk MM, Novick J, Stevenson MM,

Fournier MJ. Differential clearance of

glycoforms of IgG in normal and

autoimmune-prone mice.

Clin Exp Immunol 1996;106(2):259-64

62. Huang L, Biolsi S, Bales KR,

Kuchibhotla U. Impact of variable

domain glycosylation on antibody

clearance: an LC/MS characterization.

Anal Biochem 2006;349(2):197-207

63. Boswell CA, Deng R, Lin K, et al.

In Vitro--In Vivo Correlations of

Pharmacokinetics, Pharmacodynamics,

and Metabolism for Antibody

Therapeutics. In: Mrsny RJ,

Daughtery A, editors. Proteins and

Peptides: Pharmacokinetic,

Pharmacodynamic, and Metabolic

Outcomes. 1st edition. Informa

Healthcare; 2009

64. Hutchins JT, Kull FC Jr, Bynum J, et al.

Improved biodistribution, tumor

targeting, and reduced immunogenicity

in mice with a gamma 4 variant of

Campath-1H. Proc Natl Acad Sci USA

1995;92(26):11980-4

65. Wu H, Pfarr DS, Johnson S, et al.

Development of motavizumab, an

ultra-potent antibody for the prevention

of respiratory syncytial virus infection in

the upper and lower respiratory tract.

J Mol Biol 2007;368(3):652-65

66. Vugmeyster Y, Szklut P, Wensel D, et al.

Complex pharmacokinetics of a

humanized antibody against human

amyloid beta peptide, Anti-Abeta Ab2, in

nonclinical species. Pharm Res

2011;28(7):1696-706

67. Bumbaca D, Wong A, Drake E, et al.

Highly specific off-target binding

identified and eliminated during the

humanization of an antibody against

FGF receptor 4. MAbs 2011;3:4

68. Boswell CA, Tesar DB, Mukhyala K,

et al. Effects of charge on antibody tissue

distribution and pharmacokinetics.

Bioconjug Chem 2010;21(12):2153-63

69. Khawli LA, Goswami S, Hutchinson R,

et al. Charge variants in IgG1: Isolation,

characterization, in vitro binding

properties and pharmacokinetics in rats.

MAbs 2010;2(6):613-24

70. Putnam WS, Prabhu S, Zheng Y, et al.

Pharmacokinetic, pharmacodynamic and

immunogenicity comparability assessment

strategies for monoclonal antibodies.

Trends Biotechnol 28(10):509-16

71. Igawa T, Tsunoda H, Tachibana T, et al.

Reduced elimination of IgG antibodies

by engineering the variable region.

Protein Eng Des Sel 2010;23(5):385-92

72. Seitz K, Zhou H. Pharmacokinetic

drug-drug interaction potentials for

therapeutic monoclonal antibodies: reality

check. J Clin Pharmacol

2007;47(9):1104-18. This article provides a systematic

review of the current literature and

offers some practical considerations for

the design and conduct of

pharmacokinetic drug--drug interaction

assessments involving novel


73. Simulect� (basiliximab): US prescribing

information. Novartis Pharmaceuticals

Corp, East Hanover, NJ, USA, 2005.

Available from: http://www.pharma.us.

novartis.com/product/pi/pdf/simulect.pdf


74. Bunescu A, Seideman P, Lenkei R, et al.

Enhanced Fcgamma receptor I,

alphaMbeta2 integrin receptor expression

by monocytes and neutrophils in

rheumatoid arthritis: interaction with

platelets. J Rheumatol

2004;31(12):2347-55

75. Mould DR, Sweeney KR. The

pharmacokinetics and pharmacodynamics

of monoclonal antibodies--mechanistic

modeling applied to drug development.

Curr Opin Drug Discov Devel

2007;10(1):84-96

76. Simponi� (golimumab): US prescribing

information. Centocor Ortho Biotech

Inc.,Horsham, PA, USA, 2010. Available

from: https://www.simponi.com/sites/

default/files/pdf/prescribing-information.

pdf [Last accessed 1 June 2011]

77. Fasanmade AA, Adedokun OJ, Olson A,

et al. Serum albumin concentration:

a predictive factor of infliximab

pharmacokinetics and clinical response in

patients with ulcerative colitis. Int J Clin

Pharmacol Ther 2010;48(5):297-308

78. Guidance for Industry: Pharmacokinetics

in Patients with Impaired Renal

Function ---- Study Design Data

Analysis, and Impact on Dosing and

Labeling. FDA, Washington, DC,

USA, 2010. Available from: http://

www.fda.gov/downloads/Drugs/

GuidanceComplianceRegulatoryInformation

/Guidances/UCM204959.pdf [Last accessed

31 May 2011]

79. Guidance for Industry: Pharmacokinetics

in Patients with Impaired Hepatic

Function: Study Design Data

Analysis, and Impact on Dosing and

Labeling. FDA, Washington, DC,

USA, 2003. Available from:

http://www.fda.gov/downloads/Drugs/


/Guidances/ucm072123.pdf [Last accessed

31 May 2011]

80. Remicade� (infliximab): US prescribing


Inc. Horsham, PA, USA, 2011. Available

from: http://www.remicade.com/

remicade/assets/hcp_ppi.pdf [Last

accessed 1 June 2011]

81. Glade Bender JL, Adamson PC,

Reid JM, et al. Phase I trial and

pharmacokinetic study of bevacizumab in

pediatric patients with refractory solid



Exp

ert O

pin.

Dru

g M

etab

. Tox

icol

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Sa

skat

chew

an o

n 05

/09/

12Fo

r pe

rson

al u

se o

nly.

tumors: a Children’s Oncology Group

Study. J Clin Oncol 2008;26(3):399-405

82. Trippett TM, Herzog C, Whitlock JA,

et al. Phase I and pharmacokinetic study

of cetuximab and irinotecan in children

with refractory solid tumors: a study of

the pediatric oncology experimental

therapeutic investigators’ consortium.

J Clin Oncol 2009;27(30):5102-8

83. Malek A, Sager R, Kuhn P, et al.

Evolution of maternofetal transport of

immunoglobulins during human

pregnancy. Am J Reprod Immunol

1996;36(5):248-55

84. Hubbard JJ, Laurenzana EM,

Williams DK, et al. The fate and

function of therapeutic antiaddiction

monoclonal antibodies across the

reproductive cycle of rats. J Pharmacol

Exp Ther 2011;336(2):414-22

85. Lievre A, Blons H, Laurent-Puig P.

Oncogenic mutations as predictive factors

in colorectal cancer. Oncogene

2010;29(21):3033-43

86. Cartron G, Watier H, Golay J,

Solal-Celigny P. From the bench to the

bedside: ways to improve rituximab

efficacy. Blood 2004;104(9):2635-42

87. Dall’Ozzo S, Tartas S, Paintaud G, et al.

Rituximab-dependent cytotoxicity by

natural killer cells: influence of

FCGR3A polymorphism on the

concentration-effect relationship.

Cancer Res 2004;64(13):4664-9

88. Levy G. Pharmacologic target-mediated

drug disposition. Clin Pharmacol Ther

1994;56:248-52

89. Mager DE, Jusko WJ. General

pharmacokinetic model for drugs

exhibiting target-mediated drug

disposition.

J Pharmacokinet Pharmacodyn

2001;28(6):507-32. This paper presents a review on

target-mediated drug disposition,

including concepts and applications.

90. Gibiansky L, Gibiansky E.

Target-mediated drug disposition model

for drugs that bind to more than one

target. J Pharmacokinet Pharmacodyn

2010;37:323-46

91. Lammerts van Bueren JJ, Bleeker WK,

Bogh HO, et al. Effect of target

dynamics on pharmacokinetics of a novel

therapeutic antibody against the

epidermal growth factor receptor:

implications for the mechanisms

of action. Cancer Res

2006;66(15):7630-8

92. Ng CM, Bai S, Takimoto CH, et al.

Mechanism-based receptor-binding

model to describe the pharmacokinetic

and pharmacodynamic of an anti-alpha

(5)beta (1) integrin monoclonal antibody

(volociximab) in cancer patients.

Cancer Chemother Pharmacol

2010;65(2):207-17

93. Hale G, Rebello P, Brettman LR, et al.

Blood concentrations of alemtuzumab

and antiglobulin responses in patients

with chronic lymphocytic leukemia

following intravenous or subcutaneous

routes of administration. Blood

2004;104(4):948-55

94. Kuang B, King L, Wang HF.

Therapeutic monoclonal antibody

concentration monitoring: free or total?

Bioanalysis 2:1125-40

95. Lee JW, Kelley M, King LE, et al.

Bioanalytical approaches to quantify

“total” and “free” therapeutic antibodies

and their targets: technical challenges

and PK/PD applications over the

course of drug development. AAPS J

13:99-110

96. Ternant D, Mulleman D, Degenne D,

et al. An enzyme-linked immunosorbent

assay for therapeutic drug monitoring of

infliximab. Ther Drug Monit

2006;28:169-74

97. Ceze N, Ternant D, Piller F, et al. An

enzyme-linked immunosorbent assay for

therapeutic drug monitoring of

cetuximab. Ther Drug Monit

2009;31:597-601

98. Ternant D, Ceze N, Lecomte T, et al.

An enzyme-linked immunosorbent

assay to study bevacizumab

pharmacokinetics. Ther Drug Monit

2010;32:647-52

99. Ezan E, Bitsch F. Critical comparison

of MS and immunoassays for

the bioanalysis of therapeutic

antibodies. Bioanalysis 2009;1:

1375-88

100. Doucet J, Avrameas A. A novel method

for quantitative measurement of a

therapeutic monoclonal antibody in the

presence of its target protein using

enzymatic digestion. J Pharm

Biomed Anal 2010;52(4):565-70

101. Dedrick RL. Animal scale-up.

J Pharmacokinet Biopharm

1973;1(5):435-61

102. Jolling K, Perez Ruixo JJ, Hemeryck A,

et al. Mixed-effects modelling of the

interspecies pharmacokinetic scaling of

pegylated human erythropoietin. Eur J

Pharm Sci 2005;24(5):465-75

103. Wang W, Prueksaritanont T. Prediction

of human clearance of therapeutic

proteins: simple allometric scaling

method revisited. Biopharm Drug Dispos

2010;31(4):253-63

104. Ling J, Zhou H, Jiao Q, Davis HM.

Interspecies scaling of therapeutic

monoclonal antibodies: initial look.

J Clin Pharmacol 2009;49(12):

1382-402

105. Deng R, Iyer S, Theil FP, et al.

Projecting human pharmacokinetics of

therapeutic antibodies from nonclinical

data: What have we learned? MAbs

2011;3(1):61-6

106. Mager DE, Woo S, Jusko WJ. Scaling

pharmacodynamics from in vitro and

preclinical animal studies to humans.

Drug Metab Pharmacokinet

2009;24(1):16-24

107. Duconge J, Castillo R, Crombet T, et al.

Integrated pharmacokinetic-

pharmacodynamic modeling and

allometric scaling for optimizing the

dosage regimen of the monoclonal ior

EGF/r3 antibody. Eur J Pharm Sci

2004;21(2-3):261-70

108. Kagan L, Abraham AK, Harrold JM,

Mager DE. Interspecies scaling of

receptor-mediated pharmacokinetics

and pharmacodynamics of type I

interferons. Pharm Res

2010;27(5):920-32

109. Guidance for Industry: Estimating the

Maximum Safe Starting Dose in Initial

Clinical Trials for Therapeutics in Adult

Healthy Volunteers. FDA, Washington,

DC, USA, 2005. Available from: http://

www.fda.gov/downloads/Drugs/


/Guidances/ucm078932.pdf [Last accessed

31 May 2011]

110. Agoram BM. Use of pharmacokinetic/

pharmacodynamic modelling for starting

dose selection in first-in-human trials of

high-risk biologics. Br J Clin Pharmacol

2009;67(2):153-60

111. Lowe PJ, Hijazi Y, Luttringer O, et al.

On the anticipation of the human dose

in first-in-man trials from preclinical and

prior clinical information in early drug

development. Xenobiotica

2007;37(10-11):1331-54



Exp

ert O

pin.

Dru

g M

etab

. Tox

icol

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Sa

skat

chew

an o

n 05

/09/

12Fo

r pe

rson

al u

se o

nly.

112. Guideline on strategies to identify and

mitigate risks for first-in-human clinical trials

with investigational medicinal products:

EMA, London, UK, 2007. Available from:

http://www.ema.europa.eu/docs/en_GB/

document_library/Scientific_guideline/2009/

09/WC500002988.pdf [Last accessed

31 May 2011].. EMA guidance on the FIH selection

including a discussion on

MABEL approach.

113. Reigner BG, Blesch KS. Estimating the

starting dose for entry into humans:

principles and practice. Eur J

Clin Pharmacol 2002;57(12):835-45

114. Vugmeyster Y, Guay H, Szklut P, et al.

In vitro potency, pharmacokinetic

profiles, and pharmacological activity of

optimized anti-IL-21R antibodies in a

mouse model of lupus. MAbs

2010;2(3):335-46

115. Mager DE, Mascelli MA, Kleiman NS,

et al. Simultaneous modeling of

abciximab plasma concentrations and

ex vivo pharmacodynamics in patients

undergoing coronary angioplasty.


2003;307(3):969-76

116. Mould DR, Baumann A, Kuhlmann J,

et al. Population

pharmacokinetics-pharmacodynamics of

alemtuzumab (Campath) in patients with

chronic lymphocytic leukaemia and its

link to treatment response. Br J

Clin Pharmacol 2007;64(3):278-91

117. Lu JF, Bruno R, Eppler S, et al. Clinical

pharmacokinetics of bevacizumab in

patients with solid tumors.

Cancer Chemother Pharmacol

2008;62(5):779-86

118. Ilaris� (canakinumab): US prescribing

information. Novartis Pharmaceuticals

Corp, East Hanover, NJ, USA, 2009.

Available from: http://www.pharma.us.

novartis.com/product/pi/pdf/ilaris.pdf

[Last accessed 1 June 2011]

119. Removab�: EPAR - Product

Information. EMA L, UK, 2011.

Available from: http://www.ema.europa.

eu/docs/en_GB/document_library/

EPAR_-_Product_Information/human/

000972/WC500051809.pdf [Last

accessed 12 July 2011]

120. Cimzia� (certolizumab pegol): US

prescribing information. UCB Inc,

Smyrna, GA, USA, 2008. Available

from: http://www.cimzia.com/pdf/

Prescribing_Information.pdf [Last

accessed 1 June 2011]

121. Baselga J, Pfister D, Cooper MR, et al.

Phase I studies of anti-epidermal growth

factor receptor chimeric antibody

C225 alone and in combination with

cisplatin. J Clin Oncol

2000;18(4):904-14

122. Zenapax� (daclizumab): US prescribing

information. Hoffmann-La Roche Inc.

Nutely, NJ, USA, 2005. Available from:

http://www.gene.com/gene/products/

information/zenapax/pdf/pi.pdf [Last

accessed 31 May 2011]

123. Marathe A, Peterson MC, Mager DE.

Integrated cellular bone homeostasis

model for denosumab pharmacodynamics

in multiple myeloma patients.


2008;326(2):555-62

124. Xgeva� (denosumab): US prescribing

information. Amgen Inc, Thounsand

Oaks, CA, USA, 2010. Available from:

http://pi.amgen.com/united_states/xgeva/

xgeva_pi.pdf [Last accessed 31 May

2011]

125. Soliris� (eculizumab): US prescribing

information. Alexion Pharmaceuticals

Inc, Cheshire, CT, USA, 2009. Available

from: http://www.soliris.net/Downloads/

pdf/soliris.pdf [Last accessed 31 May

2011]

126. Ng CM, Joshi A, Dedrick RL, et al.

Pharmacokinetic-

pharmacodynamic-efficacy analysis of

efalizumab in patients with moderate to

severe psoriasis. Pharm Res

2005;22(7):1088-100

127. Mylotarg� (gemtuzumab ozogamicin for

Injection): US prescribing information.

Wyeth Pharmaceuticals Inc.,Philadelphia,

PA, USA, 2010. Available from: http://

labeling.pfizer.com/showlabeling.aspx?

id=119 [Last accessed 1 June 2011]

128. Zevalin� (ibritumomab tiuxetan): US

prescribing information. Spectrum

Pharmaceuticals Inc, Irvine, CA, USA,

2010. Available from: http://www.

zevalin.com/v3/pdf/Zevalin_PI_Website.

pdf [Last accessed 1 June 2011]

129. Orthoclone OKT�3 (muromonab-

CD3): US prescribing information.

Centocor Ortho Biotech Products L.P,

Raritan, NJ, USA, 2011. Available from:

http://www.janssenbiotech.com/assets/

OKT3_PI.pdf [Last accessed 12 July

2011]

130. Tysabri� (natalizumab): US prescribing

information. Elan Pharmaceuticals Inc,

South San Francisco, CA, USA and

Biogen Idec Inc, Weston, MA, USA,

2011. Available from: http://www.tysabri.

com/en_US/tysb/site/pdfs/TYSABRI-pi.

pdf [Last accessed 31 May 2011]

131. Arzerra� (ofatumumab): US

prescribing information.

GlaxoSmithKline Research Triangle

Park, NC, USA, 2010. Available from:

http://us.gsk.com/products/assets/

us_arzerra.pdf [Last accessed 31 May

2011]

132. Synagis� (Palivizumab): US prescribing

information. MedImmune LLC,

Gaithersburg, MD, USA, 2011. Available

from: http://www.medimmune.com/pdf/

products/synagis_pi.pdf [Last accessed

31 May 2011]

133. Lucentis� (ranibizumab injection): US

prescribing information. Genentech Inc,

South San Francisco, CA, USA, 2010.

Available from: http://www.gene.com/

gene/products/information/pdf/lucentis-

prescribing.pdf [Last accessed 31 May

2011]

134. Rituxan� (rituximab): US prescribing

information. Genentech Inc, South San

Francisco, CA, USA and Biogen Idec

Inc, Weston, MA, USA, 2011. Available

from: http://www.gene.com/gene/

products/information/pdf/rituxan-

prescribing.pdf [Last accessed 31 May

2011]

135. Actemra� (tocilizumab): US

prescribing information. Chugai

Seiyaku Kabushiki Kaisha Corp.,a

member of the Roche Group,

Hoffmann-La Roche INC, Nutley, NJ,

USA, 2011. Available from: http://

www.gene.com/gene/products/

information/actemra/pdf/pi.pdf [Last

accessed 31 May 2011]

136. Bexxar� (Tositumomab and Iodine I

131 Tositumomab): US

prescribing information.

GlaxoSmithKline Research Triangle

Park, NC, USA, 2005. Available

from: http://us.gsk.com/products/

assets/us_bexxar.pdf [Last accessed

31 May 2011]

137. Bruno R, Washington CB, Lu JF, et al.

Population pharmacokinetics of trastuzumab

in patients with HER2 + metastatic breast

cancer. Cancer Chemother Pharmacol

2005;56(4):361-9



Exp

ert O

pin.

Dru

g M

etab

. Tox

icol

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Sa

skat

chew

an o

n 05

/09/

12Fo

r pe

rson

al u

se o

nly.

138. Stelara� (ustekinumab): US prescribing


Inc. Horsham, PA, USA, 2010. Available

from: http://www.stelarainfo.com/pdf/

PrescribingInformation.pdf [Last accessed

1 June 2011]

AffiliationRong Deng†1 PhD, Feng Jin2 PhD,

Saileta Prabhu1 PhD & Suhasini Iyer1 PhD†Author for correspondence1Department of Pharmacokinetic and

Pharmacodynamic Sciences, Genentech, Inc.,

1 DNA Way, Mail Stop 463A,

South San Francisco, California, 94080, USA

Tel: +650 467 3221; Fax: +650 742 5234;

E-mail: [email protected] of DMPK and Bioanalytics,

Merck Research Laboratories, Palo Alto,

CA, USA



Exp

ert O

pin.

Dru

g M

etab

. Tox

icol

. Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

ity o

f Sa

skat

chew

an o

n 05

/09/

12Fo

r pe

rson

al u

se o

nly.

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