USING BIOMARKERSUSING BIOMARKERS

FORFOR

EARLY PHASE DOSE SELECTIONEARLY PHASE DOSE SELECTIONWITHWITH

PROTEIN ANTAGONIST DRUGSPROTEIN ANTAGONIST DRUGS

Ivan Nestorovivan.nestorov@biogenidec.com

TALK FRAMEWORKTALK FRAMEWORK

• Setting the stage: introductions and definitions

• PK and binding as major early markers

• Biological activity as validation for binding

• Walk-through example

• Regulatory implications

THERAPEUTIC PROTEINSTHERAPEUTIC PROTEINSafter B.M. Rao, D.A. Laufenburger, K.D. Wittrup. Integrating cell-level kinetic modeling into after B.M. Rao, D.A. Laufenburger, K.D. Wittrup. Integrating cell-level kinetic modeling into the design of engineered protein therapeutics. Nature Biotechnology. 23: 191-194, 2005.the design of engineered protein therapeutics. Nature Biotechnology. 23: 191-194, 2005.

• Antagonists (e.g. antibodies, soluble receptors) - block native protein interactions by binding to target protein(s)– Examples – anti-TNF, anti-VEGF, anti-BLyS/APRIL

• Agonists (e.g. cytokines, growth factors) - stimulate cell surface receptors– Examples – erythropoietin, rhGH, G-CSF, IL-2

• Targeting agents (e.g. antibodies, immunotoxins) – target specific cell surface antigens or deliver therapeutic agents– Examples – anti-CD20

BAFF-R

BCMA

TACI

B-Cell

APRIL

BLyS (BAFF)

Heterotrimer

B cell differentiation

B cell survivalAntibody

productionIg class switch

EXAMPLES:BLYS/APRIL antagonist (atacicept)

THE RESPONSE CASCADEM Danhof, G Alvan, SG Dahl, J Kuhlmann, G Paintaud. Mechanism-based pharmacokinetic-

pharmacodynamic modeling-a new classification of biomarkers. Pharm Res. 2005; 22:1432-1437.

PHASE 1 DATA

HOW TO USE THIS INFORMATION FOR DOSAGE REGIMEN DESIGN IN PHASE 2/3?

Atacicept exposure–response cascade (RA)

BLyS/APRILInhibition

DOSE & Freq.

MoABiomarkers

DiseaseBiomarkers

ClinicalMarkers

ClinicalEndpoints

FREE DRUGFREE TARGET

COMPLEX

Binding &Inhibition

Biological activity

Disease related activity

Clinical activity

Clinical efficacy

IgXFACS

IgX RFACPA

ESR, CRPJOINT CNTS

ACRXX%DAS28

THERAPEUTIC PROTEINSTHERAPEUTIC PROTEINS• Large molecules, slow PK and PD

• Specific binding to targets dominant (by engineering)

• Target load often:– Significant (in molar concentration terms)– Distributed across various tissues– Constantly renewed by endogenous production of targets– Endogenous production may be boosted by depletion

• Nonspecific binding sometimes negligible (!!! check)

• No P450 metabolism, but Ab’s to drug possible

• Protein drug metabolism often capacity limited

PK & TARGET BINDING: PK & TARGET BINDING: MAJOR EARLY MARKERSMAJOR EARLY MARKERS

• Free drug PK is expected to be nonlinear– Unless nonlinearity is overwhelmed– Or unless total drug is measured– PK Assays are critical

• Dosing should be targeted at the saturation– Below saturation – sub-therapeutic regimen– Above saturation – waste of drug and/or potential

over-inhibition– Saturation – both in blood and tissues– Saturation is a dynamic process – at all times

FREEDRUG PK

TISSUES, SoA

ABSORPTIONSITE

BLOOD

L1 KIN

ETICS

BIN

DIN

G T

OL

1 &

L2

TISSUES,

SoA

BLOOD

L2 KIN

ETICS

TISSUES,

SoA

BLOODen

dogenous

product

ion

BINDING EQUILIBRIUM:

• Binding affinity

• Drug & ligand concentrations– Systemically

– In tissues

• Dosing schedule

• Endogenous ligand production– Systemically

– In tissues

PK & BINDING

FREEDRUG PK

TISSUES, SoA

ABSORPTIONSITE

BLOOD

L1 KIN

ETICS

BIN

DIN

G T

OL

1 &

L2

TISSUES,

SoA

BLOOD

L2 KIN

ETICS

TISSUES,

SoA

BLOODen

dogenous

product

ion

PK, BINDING & DOSINGOBJECTIVE:

• Adequate binding– Process in time– At Sites of Action

– Not necessarily complete binding of ligand

• Markers of PK/binding– Free drug– Total drug– Complex concentration

– Free ligand concentration

• Means to achieve goal:– Type of dosing regimen– Dosing levels– Dosing frequency– Mode of administration

0

200

400

600

800

1000

0 14 28 42 56 70 84 98 112 126

Time [days]

Ata

cice

pt/B

LyS

Com

plex

[U

/mL]

ACCUMULATION OF COMPLEX P.P. Tak, et al. Atacicept in patients with rheumatoid arthritis: an exploratory, multicenter, double-blind, placebo-controlled,

dose – escalating, single and repeat dose phase 1b study. Accepted Arthr. & Rheum. ar-06-1723, 2007.

BLyS Concentration after Rituximab in RAG. Cambridge et al. Circulating Levels of B Lymphocyte Stimulator in Patients With Rheumatoid Arthritis

Following Rituximab Treatment. Arthritis and Rheumatism 54: 723-732 (2006).

BLyS accummulation rate in serum: ~0.08 ng/mL/day

DESIGN SO FAR:DESIGN SO FAR:

• Type of dosage: Loading - Maintenance– Eliminate initial target ligand load– Boost the redistribution of target ligand – Compensate endogenous ligand production

• Dose levels and dosing frequency ???

• Mode of administration: ???

RECEPTOR MEDIATED PKA. Munafo, A. Priestley, I. Nestorov, J. Visich, M. Rogge. Safety, pharmacokinetics and

pharmacodynamics of atacicept in healthy volunteers. Eur. J. Clin. Pharm. 63:647-656 (2007).

1

10

100

1000

10000

100000

0 7 14 21 28 35 42 49

Time [days]

Fre

e at

acic

ept

[ng

/mL

]

2.1 mg

70 mg

210 mg

630 mg

0

50

100

150

200

250

300

0 50 100 150 200 250 300

Time [days]

Ata

cice

pt:B

LyS

Com

plex

[U/m

L]

Atacicept/BLyS ComplexFree Atacicept

QUIZ:DOSING FREQUENCY?

1

10

100

1000

0 7 14 21 28 35 42 49 56 63 70 77 84Time [days]

Fre

e d

rug

[n

g/m

L]

0

40

80

120

160

Dru

g/T

arg

et c

om

ple

x [U

/mL

]

Free drug

Drug/Target Complex

Terminal Halflife:20-30 days

1

10

100

1000

0 7 14 21 28 35 42 49 56 63 70 77 84Time [days]

Fre

e d

rug

[n

g/m

L]

0

40

80

120

160

Dru

g/T

arg

et c

om

ple

x [U

/mL

]

Free drug

Drug/Target Complex

30-40% incompleteinhibition

Next dose?

QUIZ:DOSING FREQUENCY?

Biological activity tracks target ligand binding

20

40

60

80

100

120

0 7 14 21 28 35 42 49 56 63

Time [days]

IgM

[%

of

Bas

elin

e]

18 mg/kg IV

4x3 mg/kg SC

4x1 mg/kg SC0

150

300

450

600

750

0 7 14 21 28 35 42 49 56 63 70 77 84

Time [days]

Ata

cice

pt:

BL

yS C

om

ple

x [U

/mL

]

More frequent dosing at smaller doses yields better effect

Biological Activity Drug-Ligand Complex

DESIGN SO FAR:DESIGN SO FAR:• Biological activity tracks binding

• Type of dosage: Loading - Maintenance– Eliminate initial ligand load– Boost the redistribution of ligand – Compensate endogenous ligand production

• Dose levels and dosing frequency– More frequent smaller doses yield higher biological activity

compared to less frequent higher doses– Single dose saturation – between 75 and 210 mg– Dosing interval to maximize inhibition – 7 – 14 days– What doses / dosing intervals???

• Mode of administration: ???

S.C. ADMINISTRATION of PROTEIN DRUGS

• Uptake by lymphatic system

• Poorly quantified

• Dependent on MW

• Lymphatic & blood circulation closely interwined

• Consider kinetic vs dynamic rates

• Lymph can be SoAS.C. injection

10

100

1000

10000

100000

1000000

0 7 14 21 28 35 42

Time [days]

Free

ata

cice

pt [n

g/m

L]

9 mg/kg S.C.

9 mg/kg I.V.

20

40

60

80

100

120

0 7 14 21 28 35 42Time [days]

IgM

[%

of

Ba

se

line

]

… but biological activity is the same …

S.c. Atacicept systemic bioavailability is ~ 35 - 40% …

COMPARING S.C. COMPARING S.C. && I.V. ADMINISTRATION I.V. ADMINISTRATION

10

100

1000

10000

100000

1000000

0 7 14 21 28 35 42

Time [days]

Fre

e a

tac

ice

pt

[ng

/mL

]

9 mg/kg S.C.

9 mg/kg I.V.

0

100

200

300

400

0 7 14 21 28 35 42

Time [days]

Ata

cice

pt:

BL

yS C

om

ple

x [U

/mL

]

… because target binding is the same!

COMPARING S.C. COMPARING S.C. && I.V. ADMINISTRATION I.V. ADMINISTRATION

DESIGN SO FAR:DESIGN SO FAR:

• Biological activity tracks binding

• Type of dosage: Loading - Maintenance– Eliminate initial ligand load– Boost the redistribution of ligand – Compensate endogenous ligand production

• Dose levels and dosing frequency– More frequent smaller doses yield higher biological

activity compared to less frequent higher doses– Single dose saturation – between 75 and 210 mg– Dosing interval to maximize inhibition – 7 – 14 days– What doses / dosing intervals???

• Mode of administration: SC

TIME TO BECOME QUANTITATIVE…

ATACICEPT PATACICEPT Pop PK/PD MODELop PK/PD MODELI. Nestorov et al. Population modeling of the relationship between TACI‑Ig exposure and biomarker response in patients with

rheumatoid arthritis (RA). Population Analysis Group in Europe meeting PAGE 2006, June 14-16, 2006.

Abs.Site

Central Peripheral

IgM, IgG, IgA

CIC

CIK syn 50

1 max

offK

CL

QKa

Vc Vp

DOSE

0

20

40

60

80

100

0 14 28 42 56 70 84 98 112 126 140 154 168

Time [days]

25 mg

50 mg

75 mg

150 mg

500 mg

Varying doses, same dosing frequency (QW)

Simulations: Dose saturation of effect

Going beyond 150 mg

for QW not justified

IgM

[%

of

bas

elin

e]

DESIGN COMPLETEDESIGN COMPLETE• Biological activity tracks binding

• Type of dosage: Loading - Maintenance– Eliminate initial ligand load– Boost the redistribution of ligand – Compensate endogenous ligand production

• Dose levels and dosing frequency– More frequent smaller doses yield higher biological activity

compared to less frequent higher doses– Single dose saturation – between 75 and 210 mg– Dosing interval to maximize inhibition – 7 – 14 days– Dosing frequency – once weekly (QW)– Dose levels for Phase 2/3 study: 25, 75 and 150 mg

• Mode of administration: SC

REGULATORY ACTIONREGULATORY ACTION

PHASE 1

CONCLUSIONSCONCLUSIONS

• PK and target binding are major early biomarkers for protein antagonists

• Saturation of binding can be used for early phase dosage regimen design

• Population PK/PD modeling helps quantify saturation

• Mechanistic validation should be implemented as much as possible