New Treatments for Rheumatoid Arthritis

1. PHM142 Fall 2013 Coordinator: Dr. Jeffrey Henderson Instructor: Dr. David Hampson New Treatments forRheumatoid Arthritis Presented by: Ariel Kwan Christine Terzievski Rebecca Babaei-Rad Vivian Tsoi Course: Biochem PHM142 Presented on: Oct 23, 2013

2. What is Rheumatoid Arthritis (RA)? • an immune-mediated, progressive disease • CD4+ T-cells, activated B-lymphocytes, and plasma cells/macrophages are present in the synovium of patients diagnosed with RA • Cytokine secretion by these activated cells leads to an inflamed synovium and the formation of pannus – leading to joint destruction

3. Pathogenesis of RA

4. Current Therapy of RA • NSAIDs, glucocorticoids • DMARDS as methotrexate,leflunomide, plaquenil, sulfasalazine • Newer biological agents with specific molecular targets in RA pathogenesis: • TNF-α antagonist/inhibitor • Interleukin (IL) inhibitor and receptor antagonist • B cell inhibitor (anti-CD20 antibodies) • T cell directed therapies • New molecules targeting JAKs

5. What is TNFα?

6. TNF-α Inhibitor • TNF-α inhibitor binds TNF-α and prevents its interaction with its receptors • Many are monoclonal antibodies, some are receptor fusion proteins • Therapeutic goal is the removal of TNF-α from inflammation sites • The first clinically successful, cytokine-specific therapy for RA (Lasker Award 2003) • Used in combination with a DMARD • Rapid onset of action (expected effect or improved symptoms in 1-3 weeks)

7. Mode of TNFα Inhibitor Action

8. TNF-α Inhibitor Drugs

9. Adverse Effects of TNF-α Inhibitors • Injection site reactions • Increased risk of bacterial, viral, and/or fungal infections • Bone marrow suppression • Generation of antibodies to drugs, resulting in reduced efficacy over time • Drug-induced lupus-like syndromes • Emergence of lymphoma and skin cancers over long-term use

10. Interleukins • The body’s immune response involves the activation and release of cytokines (messengers) such as TNF and interleukins, from macrophages • Leukocytes release a variety of interleukins to communicate with additional leukocytes (hence the name) • Perpetuate the immune response (inflammation) • IL-1 and IL-6 are particularly important as these the both involved in some way with inflammation of the joints • Macrophage  IL-6 • Macrophage and T-cells  IL-1

11. Interleukin Receptor Inhibitors • Usually only used if patient has not improved after using other anti-inflammatory medication such as TNF antagonists • Should not be given while still using TNF antagonists due to adverse reactions that have been observed

12. Tocilizumab • Generic Name: Tocilizumab • Brand Name: Actemra • Interleukin receptor inhibitor, specifically for IL-6 binding • Given intravenously on a per month basis • Dosage: usually 20mg/ml • Adverse Effects Include: risk of contracting tuberculosis, reduced platelet level in blood, risk of hypertension

13. Tocilizumab Mode of Action • Drug binds IL-6 receptors • Prevents cytokine IL-6 from binding receptor • Cell-to-cell communication is inhibited • Inhibits production of more T and B cells and aids to decrease inflammation at the joints

14. Interleukin Receptor Inhibitors • In areas of body where IL are seen to be uncontrolled and released with no threat from invader, intensive tissue damage can be seen • IL receptor inhibitors have proved to be quite successful in individuals with RA in relieving inflammation • Additionally, shown to have beneficial effect on preventing bone degradation in RA patients as well

15. B-Cell Inhibitors • B-Cell • Type of lymphocyte • Produces antibodies • Express Fc receptors • Express CD20 on cell surface • Phosphoprotein • Spans the membrane four times • Little known except it might function as a Ca2+ ion channel

16. B-Cell Inhibitors • Why target B-cells? • Evidence for production of rheumatoid factor (RF) • Autoantibody which binds to Fc region of IgG • Depletion of B-cells is accompanied by reduction of inflammation • Secrete cytokines which interact with cells involved in autoimmune response • Ie. TNF-alpha and chemokines • How to target B-cells? • CD20 • Found exclusively on B-cells • Not shed from B cells • Expressed at high levels

17. B-Cell Inhibitors • Rituximab • Chimeric/fusion protein • Antibody consisting of human IgG-1 constant regions and murine (mouse) variable regions • Mouse variable regions come from antibody that recognizes CD20 • Also binds to Fc receptors

18. B-Cell Inhibitors • Complement-dependent cytotoxicity (CDC) • Innate immunity • C1q • Serum protein which binds to Fc region rituximab • Triggers cascade resulting in C5b • C5b triggers membrane attack complex (MAC) formation • MEC forms transmembrane channels in the bilayer resulting in cell lysis

19. Complement-dependent cytotoxicity

20. B-Cell Inhibitors • Antibody-dependent cell-mediated cytotoxicity (ADCC) • Adaptive immunity • Natural killer (NK) cells, granulocytes, macrophages all express Fc receptors of IgG • Once bound, lyse B-cell using respective effector mechanisms • Induction of apoptosis • Little known about specifics

21. T-Cell Directed Therapy • T-cell • Type of lymphocyte • Have a T-cell receptor on its surface • Various types, including cytotoxic, helper, natural killer, memory, and regulatory • Cytotoxic T cells destroy infected cells • Also known as CD8+T cells because they express CD8 protein on the cell surface • Bind to an antigen associated with MHC Class I 18

23. T-Cell Activation • T-cell activation requires 2 signals: • 1st signal: The antigen presented by the MHC is recognized by the T-cell receptor • 2nd signal: Co-stimulatory molecules CD80 and CD86 on APCs bind to CD28, an auto-regulatory protein, on the T-cell surface • T-cells have an intrinsic mechanism to terminate T-cell activation, which regulates immune activation

24. Regulating T-cell Activation • T-cell regulation occurs via the Cytotoxic T-Lymphocyte Associated Antigen-4 (CTLA-4) molecule • CTLA-4 acts as a negative regulator of CD28-mediated T-cell stimulation • Antagonizes the CD80/CD86:CD28 binding pathway by binding CD80/CD86 • Greater affinity for CD80/CD86 than CD28 • Leads to the down-regulation of T-cell activation

25. Abatacept • Classified as a biological disease-modifying anti-rheumatic drug (DMARD) • Used to treat RA in patients who had failed to respond to other DMARDs or TNF inhibitors • Consists of the extracellular domain of CTLA-4 and a modified Fc fragment of IgG1 to prevent antibody dependent cell-mediated cytotoxicity • Has a novel mechanism of action that mimics CTLA-4’s action 22

26. Mechanism of Action • Abatacept interrupts the CD80/CD86: CD28 pathway • i.e. It does not allow the 2nd signal in T-cell activation to occur • Abatacept binds to co-stimulatory proteins CD80 and CD86, preventing CD28 from binding • Thus, T-cell activation is inhibited 23

27. Effects of Abatacept • Inhibits the proliferation of T-cells in vitro and in vivo • Reduces the amount of circulating CD8+CD28- T cells, which suppresses the number of CD4+T cells produced • Reduces adhesion and migratory capacity of monocytes and the inflammatory activity of synovial macrophages • Regulates the function of CD4+T cells 24

28. Overview of Abatacept’s Mechanism of Action

29. Janus Kinase Inhibitors (JAKs) • New molecular approach to treating RA • Inhibit the activity of the janus kinase (JAK) family to down regulate inflammatory reactions • JAK inhibitors include: • Tofacitinib • VX-509 (Vertex) • Baricitinib

30. JAK Family • Tyrosine kinase proteins • Family includes: • JAK1 • JAK2 • JAK3 • TYK2 • Plays an important role in mediating the intracellular signal transduction of cytokines

31. JAK Proteins • Acting in pairs, JAK proteins facilitate the phosphorylation of intracellular proteins • Phosphorylation of the signal transducer and activator of transcription (STAT) leads to altered gene transcription • STAT controls autoimmune and inflammatory responses 26

32. Tofacitinib • Small, non-biologic DMARD with demonstrated efficacy in treating RA • Interferes with the signalling pathways of JAK1 and JAK3 • JAK3 associates with the Ɣ-chain of common cytokine receptors • These receptors are used by interleukins to regulate lymphocyte activation and production • Inhibition leads to anti-inflammatory and immunosuppressive effects

33. Tofacitinib: Inhibiting JAK-Dependent STAT Pathways

34. Summary

35. Summary of RA Treatment • RA is an auto-immune disease with upstream mechanisms of activated macrophages, activated B cells and activated T cells; resulting in downstream cytokine production and destruction signaling pathways. • Activated macrophages secrete (downstream) inflammatory cytokines TNF-α, and IL-6 and IL-1. • TNF-α inhibitors  etanercept, infliximab, adalimumab • IL-6 receptor antagonist  tocilizumab • IL-1 receptor antagonist  anakinra • Activated B cells contribute to inflammation and destruction by producing autoantibodies (RF) and cytokine IL-6 • Bind to CD20 antigen on B Cell and depletes B cells  rituximab • Activated (CD4+) T cells activate macrophages and B cells • Upstream regulation of T Cell activation pathway  abatacept • Downstream signaling pathways (RANK, MMPs) • JAK inhibitors to down regulate inflammatory responses  tofacitinib

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37. References Larrick JW. Native interleukin 1 inhibitors. Immunology Today 10(2): 61-66, 1989. Li H et al. Store-operated cation entry mediated by CD20 in membrane rafts. The Journal of Biological Chemistry 278(43): 42427-42434, 2003. Mola EM et al. Abatacept use in rheumatoid arthritis: evidence review and recommendations. Rheumatol Clin. 1: 5-17, 2013. Najafian N, et al. Regulatory functions of CD8+CD28- T cells in an autoimmune disease model. J Clin Invest. 112: 1037-48, 2003. Pappas DA et al. Immune modulation of rheumatoid arthritis. Best Practice & Research Clinical Rheumatology 25: 873-889, 2011. Rezvani AR and Maloney DG. Rituximab resistance. Best Practice and Research Clinical Haematology 24(2): 203-216, 2011. Scott DL et al. Rheumatoid arthritis. The Lancet 376(9746): 1094-1108, 2010. Shaw T et al. B-cell therapy for rheumatoid arthritis: the rituximab (anti-CD20) experience. Annals of the rheumatic diseases 62(2): ii55-ii59, 2003. Tayar JH and Suarez-Almazor ME. New understanding and approaches to treatment in rheumatoid arthritis. British Medical Bulletin 94: 201-204, 2010. Willey, J.M., Woolverton, C.J., Sherwood, L.M. (2011). Prescott’s Microbiology (8th ed.). New York, NY: McGraw-Hill.

38. Image Credits(in order of appearance in presentation) • http://www.medscape.org/viewarticle/505489_3 • http://www.sciencedirect.com/science/article/pii/S0264410X13009110 • http://www.leidenuniv.nl/en/researcharchive/index.php3-c=446.htm • www.remicade.com • http://3scorporation.com/products/actemra-80-mg-vial-5-ml/ • http://www.actemrahcp.com/about-actemra/actemra-moa.html • http://www.sciencedirect.com/science/article/pii/S1471489210000068 • http://archive.ispub.com/journal/the-internet-journal-of-rheumatology/volume-5-number-2/management-of-inadequate-response-to-tnf-antagonist-therapy-in-rheumatoid-arthritis-what-are-the-options.html#sthash.LcCZjZcm.dpbs