Recent advances in Fc receptor-dependent therapies

Alan H. Lazarus, PhD

Canadian Blood ServicesSt. Michael’s HospitalUniversity of Toronto

CBS Transfusion Medicine Resident Scientific SessionNov 2, 2010

Outline

•Mechanisms of platelet destruction in ITP

•Recent advances in:

• Fc receptor blockade• IVIg• anti-D• Inhibition of Fc receptor signaling

•Conclusions

Immune thrombocytopenic purpura (ITP)

Platelet

An Fc-independent mechanism of potential immune thrombocytopenia-ROS

Zang W et al, Blood 2008Li Z et al, J Biol Chem 2008Li Z et al, Blood 2009

GPIIbIIIa

ROSROSHCVHCV

Wright JF et al, Br J Haem 1996Wright JF et al, Br J Haem 1996VZVVZV

QuinineQuininePeterson, Blood 2008

Fc-independent immune thrombocytopenia-GPIb

Platelet

Nieswandt et al Blood 2000Webster et al Blood 2006Go et al Haematologica 2007

GPIb

Carbohydrates important for IgG function?

Fc

F(ab’)2

Albert H et al. PNAS 2008;105:15005-15009

©2008 by National Academy of Sciences

IgG subclass-specific effects of EndoS-mediated hydrolysis of the IgG-associated sugar side chain.

A potential alternative mechanism of platelet destruction?Cell Mediated Immunity

Olsson et al, Nature Medicine 2003Zhang et al, Eur J Haem 2006

An alternative mechanism which may contribute to immune thrombocytopenia?

PLTPLTPLT

MK in Bone MarrowMK in Bone Marrow

Decreased platelet production due to antibody and/or T cells inhibiting or destroying MK

Mechanism Fc receptors Reference

classic anti-IIbIIIa yes Harrington Experiment 1951

anti-IIbIIIa (49-66) no Zhang, 2008 Li, 2008 Li, 2009

anti-GPIb no Nieswandt, 2000 Webster, 2006 Go, 2007

T cells no Olsson, 2003 Zhang, 2006Chow, 2010

Direct effect on MK ? Chang 2003McMillan 2004Houwerzijl 2004

Outline

•Mechanisms of platelet destruction in ITP

•Recent advances in:

• Fc receptor blockade• IVIg• anti-D• Inhibition of Fc receptor signaling

+other potential Fc receptors for IgG (FCRL’s)

Fc receptor blockade

•Antibody specific for FcRIIIa worked in refractory ITP (Clarkson, 1986)

•Antibody specific for FcRI worked in ITP (Terjanian, 2000 abstract in Blood)

•Humanized antibody for FcRIIIa (GMA161& 3G8) worked but with side effects (Bussel, 2006 & Nakar, 2009 abstracts in Blood)

Fc receptor blockade

• Clodronate is effective in a mouse model of passive ITP (Alves-Rosa 2000, 2002; Deng & Balthasar 2005, 2007; Li 2006)

Taken from, www.clodronateliposomes.org

Outline

•Mechanisms of platelet destruction in ITP

•Recent advances in:

• Fc receptor blockade• IVIg• anti-D• Inhibition of Fc receptor signaling

IVIg is IgG

Fc

F(ab’)2

Intravenous Immunoglobulin

How does IVIg work?

What does IVIg bind to?

• Other antibodies [Schussler, 1997]• Glycolipids [Vuist, 1997]• Superantigens [Takei, 1993]• HLA antigens [Glotz, 1993]• DNA & Phospholipid [Krause, Blank, Shoenfeld. 1998]• Fas/FasL [Viard, 1998, Prasad, 1998, Altznauer, 2003]• IgE Fc receptor & Tetanus toxoid [Horn, 1999]• Galactose disaccharides [Barreau, 2000]• Auto-antigens [reviewed in St-Amour, 2009]• Red Blood cells [Salama, 1984]• ……

Theories of IVIg action

• Fc receptor blockade• Inhibitory FcγRIIB expression• Regulation of cytokine production• Anti-idiotypic antibodies• Inhibits complement activation• Clearance of pathogenic antibody-FcRn.• Apoptosis• IVIg possesses anti-inflammatory sugars• IVIg forms soluble immune complexes• Dendritic cells

Hypothesis

Can antibodies which form an immune complex ameliorate ITP?

Teeling et al, Blood 2001

Experimental Design

Cell-associated:

(anti-D like effect)

OVA

Soluble:

A murine model of Passive Immune Thrombocytopenia

Anti-PLT

24h

FSC

SS

CRavetch et al (NY)

Bleeker et al (Amsterdam)

Balthasar & Deng (Buffalo)

Lemieux & Bazin (Quebec City)

Webster et al (Toronto)

Ravetch et al (NY)

Bleeker et al (Amsterdam)

Balthasar & Deng (Buffalo)

Lemieux & Bazin (Quebec City)

Webster et al (Toronto)

0 1 2 3 40

200

400

600

800

1000

***

***

***

***

anti-platelet antibody

Tre

atm

en

t

Pla

tele

t cou

nt x

109 /L

Inhibitory FcγRIIB

Activating FcγR

FcγRIIB-/- mice

0 1 2 3 40

200

400

600

800

1000

anti-platelet antibody

Tre

atm

en

t

0 1 2 3 40

200

400

600

800

1000

*** ***

anti-platelet antibody

Tre

atm

en

t

If IVIg functions via the formation of an immune complex, could these complexes be reacted with cells which could then be

adoptively transferred to recipients?

Mix Wash Load

Inject

Amelioration of ITP?

Adoptive-transfer of IVIg effects with leukocytes

Siragam et al, Nature Medicine 2006

Proposed model of IVIg action in murine ITP

Siragam et al, J Clin Invest 2005

Siragam et al, Nat Med 2006

Tha-In et al, Blood 2007

Ephrem et al, Blood 2008

Aubin et al, Blood 2010

ITP

Park-Min, Immunity 2007

Outline

•Mechanisms of platelet destruction in ITP

•Recent advances in:

• Fc receptor blockade• IVIg• anti-D• Inhibition of Fc receptor signaling

Nil IVIg 30-F1 TER119 M1/690

50

100

150

200

* *

Fc R

IIIA

Ex

pre

ss

ion

Anti-D-like antibodies reduce the ability to detectactivating Fcγ receptors on macrophages

Song et al, Blood 105:1546-8, 2005

Does anti-D ameliorate ITP via the same mechanism as IVIg?

Cooper et al, Br J Haem 2004

IVIG

Anti-D

IL-10

IL-10 MCP-1 IL-6 TNFα

2 hr

Of the 6 patients in the study who had failed to respond to IVIG andanti-D given as single agents, 5 of them responded when given in combination.

Blood 2007

Outline

•Mechanisms of platelet destruction in ITP

•Recent advances in:

• Fc receptor blockade• IVIg• anti-D• Inhibition of Fc receptor signaling

•Conclusions

A new therapeutic intervention based upon the mouse model of ITP?

Platelet phagocytosis in ITP

syksyksyksyk

R406R406

Braselmann, et al. J Pharmacol Exp Ther, 2006Braselmann, et al. J Pharmacol Exp Ther, 2006

Inhibition of syk ameliorates murine ITP

0

200

400

600

800

1000

Treatment Nil IVIg2 g/kg

Vehicle R78825 mg/kg

R78840 mg/kg

Unmanipulated

Pla

tele

t co

un

t x

109 /L

Podolanczuk, A. et al. Blood 2009;113:3154-3160

Copyright ©2009 American Society of Hematology. Copyright restrictions may apply.

Podolanczuk, A. et al. Blood 2009;113:3154-3160

syk inhibition in 16 adult refractory ITP patients

Conclusions

•Multiple potential mechanisms of thrombocytopenia in ITP.

•The mechanism of IVIg remains unclear but may work via an Fc receptor-dependent cellular pathway (DC)

•Anti-D appears to work via a mechanism distinct from IVIg

•Inhibition of Fc receptor signaling or function could be a potential therapy in ITP

Andrew R CrowDr. Zhong-Wei ChaiSara SuppaXi ChenJoan LegardaPatrick Mott

Thank you!Thank you!Dr. John FreedmanDr. Bernadette GarveyDr. John SempleDr. Heyu NiDr. Valery LeytinDr. Margaret Rand

Derry Roopenian

Jim BusselAnna Podolanczuk