Immunopathogenesis of SLE and Rationale for Biologic Therapy

Immunopathogenesis of SLE and Rationale for Biologic Therapy Peter Lipsky, MD Editor, Arthritis Research and Therapy Bethesda, MD Environmental Triggers, Gender, and Genetic Factors Contribute to SLE Pathogenesis Environmental Triggers UV light Cigarette smoking Infection and toll-like receptor stimulation Multiple Genetic Polymorphisms Subjected to Epigenetic Regulation Sex Hormone Interactions Female predominance Immune dysregulation SLE Guggino G, et al. Clin Dev Immunol 2011; DOI:10.1155/2012/135932; Mok CC and Lau CS. J Clin Pathol 2003;56(7):481 90 2

B-Cell Function in Immune Responses Activate antigen presenting cell function Antigen presentation Regulate T cell activation, anergy or differentiation (Bregs) Antibody production Regulate FDC differentiation and lymphoid organisation Produce cytokines FDC = follicular dendritic cell Lipsky PE. Nat Immunol 2001;2:764 6. B Cells and Systemic Lupus Erythematosus Murine models show that genetic manipulations which enhance B-cell function in mice with specific genetic backgrounds can result in: autoantibody formation often an SLE-like disease but not inflammatory arthritis In humans, a role for B cells in SLE can be proven by showing that interventions that target B cells specifically alter disease manifestations A role for B cells in SLE has been demonstrated by clinical improvement upon therapeutic B-cell targeting with belimumab However, besides the production of autoantibodies, the contribution of enhanced B-cell function to the pathogenesis of SLE remains uncertain and the specific B-cell subsets involved as well as the functions of B cells in SLE have not been resolved Isenberg DA. J Rheumatol Suppl 2006;77:24-8. Dörner T, et al. Autoimmun Rev 2009;9:82-9.

Normal B Cell Maturation and Stimulation 5 Effector B Cell Subsets Memory B Cells Generated during T cell-dependent responses Antigen specific Specialized for heightened secondary responses to antigen Usually express post-switch mutated B cell receptors Resistant to standard immunosuppressive therapy, rituximab and belimumab Immunoglobulin Secreting Cells (Plasma Cells and Plasmablasts) Plasmablasts Short-lived dividing cells that secrete large amounts of antibody transiently Generated during T cell-independent and T cell-dependent responses Antigen specific Secrete IgM ( TI) or IgG (TD) that is either minimally (TI) or heavily (TD) Sensitive to immunosuppressive therapy, rituximab, belimumab Plasma Cells Long-lived non-dividing cells that reside in specific niches and secrete large amounts of antibody continuously without antigenic stimulation Generated during TD responses Antigen specific Secrete IgG and IgA that is heavily mutated Resistant to immunosuppressive therapy, rituximab, belimumab 6

CD27 Circulating B-Cell Sub-Sets Plasma cells Normal Post-switch memory Pre-switch memory 100,000 10,000 1,000 0 Immature CD27-IgDcells memory cells 0 1,000 10,000 100,000 lgd Naïve Immature Cells Dörner T, et al. Arthritis Res Ther 2009;11:247-57. B-cell Hyper-reactivity: a Contributing Factor in SLE BONE MARROW CIRCULATION LYMPHOID TISSUE GERMINAL CENTER T Cell Help (Costimulation and Cytokine Production) Memory Cell Autoreactive Memory B cells Autoantigen Short-lived Plasmablast Stem Cell/ B-cell Precursor Immature B cell Naïve B cell Naïve Follicular B cell Long-lived Plasma Cell Autoreactive Plasma cells & Autoantibodies Kalled SL. Semin Immunol 2006;18:290 296; Pisetsky DS, et al. Nat Rev Rheumatol 2011;7(9):551 556; Mietzner B, et al. Proc Natl Acad Sci U S A 2008;105(28):9727 9732 8

CD27 CD27 B Cell Abnormalities in Active SLE Normal SLE Plasma cells Post-switch memory Pre-switch memory 100,000 100,000 10,000 10,000 1,000 1,000 0 CD27-IgDmemory cells Naïve Immature cells 0 0 1,000 10,000 100,000 lgd 0 1,000 10,000 100,000 lgd Dörner T, et al. Arthritis Res Ther 2009;11:247-57. T-Cell-Dependent Generation of High Avidity Autoantibodies within GCs Antigenic stimulation T Cell help (PTPN22, IL-21) Naïve B cell activation GC REACTION Clonal expansion Somatic hypermutation Class switch recombination Selection of autoreactive clones apoptosis clearance of apoptotic material Intrinsic B Cell hyper-responsiveness (BANK1, BLK, IL-21R, FcRG2b, TLR7, PTPN22, CD40, Lyn, TNFAIP3, Blimp1) AUTOANTIBODY SECRETING PLASMA CELLS AUTOANTIGEN REACTIVE MEMORY B CELLS Dörner T, et al. Arthritis Res Ther 2009;11:247-57.

Generation of Ig Secreting Cells T Independent Response T Dependent Response Short-lived low avidity IgM secreting plasmablast Short-lived low/high avidity IgM/IgG secreting plasmablast Blood Germinal Center Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108 Generation of Ig Secreting Cells T Independent Response T Dependent Response Short-lived low avidity IgM secreting plasmablast Short-lived low/high avidity IgM/IgG secreting plasmablast Blood Germinal Center Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108

Generation of Ig Secreting Cells T Independent Response T Dependent Response Short-lived low avidity IgM secreting plasmablast T FH Cell Blood Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108 Generation of Ig Secreting Cells T Independent Response T Dependent Response Short-lived low avidity IgM secreting plasmablast ICOS : ICOSL T FH Cell Blood Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108

ICOS:ICOSLigand ICOS (Inducible T cell Stimulator(CD278) is a member of the CD28/CTLA-4 family expressed on activated T cells ICOS Ligand (CD275) is a member of the CD80/86 family and is expressed on B lineage cells, dendritic cells, macrophages, endothelial cells Critically involved in the generation of T FH Cells by upregulating bcl6 In mice, absence leads to markedly decreased germinal center reactions and decreased levels of IgG1 and IgE following immunization. In humans, loss of function mutations associated with a subset of CVID Over expression of ICOS results in a lupus like syndrome Generation of Ig Secreting Cells T Independent Response T Dependent Response Short-lived low avidity IgM secreting plasmablast ICOS : ICOSL T FH Cell Blood CXCR5:CXCL13 Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108

CXCR5: CXCL13 CXCR5 (CD185) is a G protein-coupled seven transmembrane receptor expressed by B cells, central memory CD4 T cells and T FH cells CXCR5 specifically recognizes CXCL13 produced by FDC and stromal cells CXCR5:CXCL13 interactions control co-localization of activated T FH cells and B cells in the initiation of GC reactions In the absence of CXCR5:CXCL13 interactions, GC formation and T cell dependent antibody responses do not occur Generation of Ig Secreting Cells T Independent Response T Dependent Response CD40 : CD154 Short-lived low avidity IgM secreting plasmablast ICOS : ICOSL T FH Cell Blood CXCR5:CXCL13 Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108

CD40: CD154 CD40( TNFRSF5) is expressed by B cells, antigen presenting cells and endothelial cells CD40 interacts with CD154(CD40L, TNFSF5) expressed on activated T cells, platelets CD40-CD154 interactions are essential for GC formation In the absence of CD154 in mice or humans(higm1), there is no GC formation, class switch recombination, somatic hypermutation or generation of memory B cells Generation of Ig Secreting Cells T Independent Response T Dependent Response CD40 : CD154 Short-lived low avidity IgM secreting plasmablast ICOS : ICOSL T FH Cell IL-21 Blood CXCR5:CXCL13 Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108

IL-21 Discovered 2000 Type-I-Cytokine Common-Cytokine-Receptor g-chain IL-2Ra IL-15Ra IL-2 IL-4 IL-7 IL-9 IL-15 IL-21 IL-2Rb g c IL-4R g c IL-7R g c IL-9R g c IL-2Rb g c IL-21R g c Properties of IL-21/IL-21R 1. IL-21, a type 1 cytokine is produced by CD4 + T cells after antigen activation and also CD8 + T cells and NKT cells. It is constitutively expressed by CXCR5 + T Follicular Helper Cells(T FH, T H21 ). The IL-21 gene is located in 4q27. 2. IL-21R is a composite receptor composed of the specific IL-21R and the γ C chain. Signaling involves STAT3 >STAT1>>>STAT5. IL-21R is expressed by lymphohemopoietic cells, but also by epithelial cells, keratinocytes, and synovial fibroblasts and is induced by antigen/mitogen stimulation and IL-21. The IL21R gene is located in 16p11.

Major Actions of IL-21 T Cells/NK Cells Promotes survival and expansion of CD8 + T Cells and NK Cells Promotes differentiation of Th17 Cells B Cells Promotes expansion and differentiation of naïve and memory B Cells into Ig secreting plasma cells. IL-21 and SLE IL-21 drives extensive plasma cell differentiation and Ig production from stimulated murine and human naïve and memory cells Levels of IL-21 are markedly elevated in BXSB mice, sanroque mice and SLE patients SLE is associated with a polymorphism in the IL-21 gene and the IL- 21R gene Blocking IL-21 is effective therapy in MRL lpr/lpr mice, and lupus in BXSByaa mice is prevented by deletion of the IL-21R

Generation of Ig Secreting Cells T Independent Response Short-lived low avidity IgM secreting plasmablast T Dependent Response CD40 : CD154 ICOS : ICOSL T FH Cell IL-21 Blood CXCR5:CXCL13 BAFF/BLyS Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108 The BAFF/BLyS-APRIL System PMNs, Myeloid cells, Stromal cells, T cells Furin Furin BAFF/BLyS (TNFSF13B) APRIL (TNFSF13A) Belimumab, BAFF-R-Ig Atacicept 1 BAFF-R TACI BCMA PG (TNFRSF13C) (TNFRSF13B) (TNFRSF17[13A]) Naïve Memory Plasma cells B CELLS Cancro MP, et al. J Clin Invest 2009;119:1066-73. Ng LG, et al. Mol Immunol 2005;42:763-72. Treml JF, et al. Cell Biochem Biophys 2009;53:1-16.

The Roles of BAFF/BLyS and APRIL and Their Receptors in B- Cell Biology: Lessons from Genetically Altered Mice Cytokines: BAFF/BLyS controls the development and survival of conventional (B2) B cells and marginal zone (MZ) B cells APRIL is involved in the switch to IgA and in plasma cell survival Optimal plasma cell survival requires both BAFF/BLyS and APRIL B-cell memory does not depend upon either BAFF/BLyS or APRIL Receptors: BAFF-R controls the development and survival of conventional (B2) and MZ B cells TACI, BCMA are involved in regulating the expansion of the B-cell pool BCMA contributes to plasma-cell survival Mackay F, et al. J Exp Med 1999;190:1697-710. Ramanujam M, et al. J Clin Invest 2006;116:724-34. Miller JP, et al. J Immunol 2006;176:6405-10. Castigli E, et al. Proc Natl Acad Sci 2004;101:3903-8. O Connor BP, et al. J Exp Med 2004;199:91-7. Treml JF, et al. Cell Biochem Biophys 2009;53:1-16. BAFF/BLyS and Autoimmunity In mouse models, overexpression of BAFF/BLyS can lead to the development of an SLE-like disease BAFF/BLyS and APRIL blockade suppresses some animal models of SLE and inflammatory arthritis Mackay F, et al. J Exp Med 1999;190:1697-710. Khare SJ, et al. Proc Natl Acad Sci U S A. 2000;97:3370-5. Gross JA, et al. Nature 2000;404:995-9. Ramanujam M, et al. J Clin Invest 2006;116:724-34. Xiao Y, et al. Eur J Immunol 2008;38:3450-8. Wang H, et al. Nat Immunol 2001;2:632-7.

Percent change in naïve B cells Percent change in memory B cells Percent change in CD20 count Percent change in activated B cells The Rationale for BAFF/BLyS and APRIL Blockade in SLE Data from murine models Elevated levels of BAFF/BLyS and APRIL in subjects with SLE In SLE, BAFF/BLyS levels correlate with anti-dna titers and disease activity Dörner T. Arth Res Ther. 2009:11:247-257;404:995-9; Mackay F, et al. J Exp Med 1999;190:1697-710. Khare SJ, et al. Proc Natl Acad Sci U S A. 2000;97:3370-5; Ramanujam M, et al. J Clin Invest 2006;116:724-34. Cheema G, et al. Arthritis Rheum 2001;44:1313-19; Petri M, et al. Arthritis Rheum 2008;58:2453-9. Belimumab Induced Changes in B-Cell Subsets in Subjects with SLE Belimumab Placebo 1.0 mg/kg 4.0 mg/kg 10.0 mg/kg All active 100 B cells 100 Activated 50 50 0 0 50 50 100 100 0 28 56 84 112 168 224 280 336 0 28 56 84 112 168 224 280 336 Time (day) Time (day) 100 50 Naïve 100 50 Memory 0 0 50 50 100 100 0 28 56 84 112 168 224 280 336 0 28 56 84 112 168 224 280 336 Time (day) Time (day) Phase 2 Wallace D, et al. Arthritis Rheum 2009;61:1168-78.

Median % change Median % change The Effect of Belimumab on Circulating Plasma Cells CD19 + / CD27 BR /CD38 BR plasma cells 20 Placebo Belimumab 1 mg/kg Belimumab 10 mg/kg + 0 20 40 60 80 0 8 24 52 76 BLISS-76 p<0.001; + p<0.01;*p<0.05 Study week Petri M, et al. Oral presentation at APLAR 2010. Abstract 0281. The Effect of Belimumab on Serum IgG Levels Serum IgG levels 20 Placebo Belimumab 1 mg/kg Belimumab 10 mg/kg 10 0 10 20 30 0 8 24 40 52 BLISS-52 p<0.001; + p<0.01;*p<0.05 Study week Levy R, et al. Poster presentation at EULAR 2010. Abstract SAT0205.

Median (%) change (positive at baseline) The Effect of Belimumab on Autoantibody Titers Placebo Belimumab Belimumab 52 112 160 208 Week * * * 0-10 -20-30 -40-50 -60 Anti-RNP Anti-Sm Anti-dsDNA Anti-cardiolipin IgG Phase 2 Petri MA, et al. Arthritis Rheum 2009;60(Suppl.10):Abstract 2069. BAFF/BLyS Blockade in SLE 2 replicate studies show significant, although moderate benefit These results demonstrate a role for B cells in some patients with SLE

Generation of Ig Secreting Cells T Independent Response Short-lived low avidity IgM secreting plasmablast T Dependent Response CD40 : CD154 ICOS : ICOSL T FH Cell IL-21 Blood CXCR5:CXCL13 IL-6 BAFF/BLyS Germinal Center Short-lived low/high avidity IgM/IgG secreting plasmablast Anti-dsDNA Long-lived high avidity IgG secreting plasma cell Bone marrow/malt Anti-Sm/RNP Nat Rev Rheum Nat. Rev. Rheumatol.doi:10.1038/nrrheum.2011.108 IL-6 in Human SLE Systemic Increased serum IL-6 levels in active lupus Increased IL-6 production by T and B cells Increased expression of IL-6R by B cells in active lupus Blocking IL-6 decreases spontaneous Ig and antidsdna production ex vivo Effects on kidney IL-6 increases mesangial cell proliferation Increased IL-6 expression in lupus kidneys Increased urinary IL-6 levels during active lupus nephritis

ESR Week 0 ESR Week 6 ESR Week 14 ESR Week 20 Fibr Week 0 Fibr Week 6 Fibr Week 14 Fibr Week 20 Cell Mean Cell Mean Tocilizumab in SLE: Phase I study Open label, inter-group dose escalating design 2 mg/kg: 4 subjects 4 mg/kg: 6 subjects 8 mg/kg 6 subjects Seven bi-weekly infusions 2 months follow-up Patients with mild-to-moderate disease No other immunosuppressive therapy except moderate doses of prednisone (< 0.3 mg/kg) Primary outcome: safety Secondary outcomes: Clinical efficacy Biologic effect 16 patients completed the study GG Illei et al. Arthritis Rheum 62:542, 20 Impact of Tocilizumab: Acute Phase Reactants Interaction Line Plot for ESR Effect: Category for ESR Error Bars: ± 1 Standard ESR Error(s) Inclusion criteria: Completers from Final MRA efficacy data compacted.svd 55 50 45 40 35 30 25 20 15 10 5 300 275 Interaction Line Plot for Fibr Effect: Category for Error Bars: ± Fibrinogen 1 Standard Error(s) Inclusion criteria: Completers from Final MRA efficacy data compacted.svd 450 425 400 375 350 325 250 225 200 Therapy Cell Therapy Cell GG Illei et al. Arthritis Rheum 62:542, 20

SLEDAI Week 0 SLEDAI Week 6 SLEDAI Week 14 SLEDAI Week 20 SLAM Week 0 SLAM Week 6 SLAM Week 14 SLAM Week 20 Cell Mean Cell Mean DNA Week 0 DNA Week 6 DNA Week 14 DNA Week 20 Cell Mean Impact of Tocilizumab in SLE: Anti-dsDNA 500 Interaction Line Plot for DNA Effect: Category for DNA Error Bars: ± 1 Standard Error(s) Inclusion criteria: Completers from Final MRA efficacy data compacted.svd 450 400 350 300 250 200 150 100 Cell Therapy GG Illei et al. Arthritis Rheum 62:542, 20 Impact of Tocilizumab: Disease Activity Interaction Line Plot for SLEDAI Effect: Category for SLEDAI Error Bars: ± 1 Standard Error(s) Inclusion criteria: Completers from Final MRA efficacy data compacted.svd 11 10 Interaction Line Plot for SLAM Effect: Category for SLAM Error Bars: ± 1 Standard Error(s) Inclusion criteria: Completers from Final MRA efficacy data compacted.svd 8 7.5 9 8 7 7 6.5 6 5.5 6 5 5 4.5 4 4 Cell Therapy SLEDAI Cell Therapy SLAM GG Illei et al. Arthritis Rheum 62:542, 20

Blockade of IL-6R with Tocilizumab Normalizes Circulating Plasma Cells in SLE GG Illei et al. Arthritis Rheu 62:542, 2010 Efficacy of Tocilizumab in SLE Prompt decrease in acute phase reactants Decrease in anti-dsdna antibodies Improvement in overall disease activity Normalization of circulating B cell subsets These results indicate: IL-6 plays an important role in lupus pathogenesis IL-6 may be a good target for therapeutic intervention.