Immunomodulators Pharmacology IV (PHL 425) Dr. Abdulaziz Saeedan [PhD, Pharmacology] E-mail: a.binsaeedan@psau.edu.sa

The Immune Response - why and how ? Discriminate: Self / Non self Destroy: Infectious invaders Dysregulated self (cancers) Immunity: Innate, Natural Adaptive, Learned

ABNORMAL IMMUNE RESPONSE A. Hypersensitivity reactions: Refer to undesirable reactions produced by the normal immune system and may be damaging, uncomfortable, or occasionally fatal Type I (immediate ) e.g. Anaphylactic shock, Allergy Type II: antibody-dependent (or cytotoxic): Self-cells are marked by antibodies for destruction. e.g. cytopenia (low number of blood cells) Type III: Immune complexes: (antigen-antibody reactions) deposited in various tissues. e.g. Allergy to a medicine Type IV: Cell-mediated or delayed: these reactions are mediated by T cells, monocytes, and macrophages. e.g. Contact dermatitis

C. Immunodeficiency Diseases: B. Autoimmunity: – Autoimmune diseases arise when the body mounts an immune response against itself as a result of failure to distinguish self tissues and cells from foreign antigens. E.g. Rheumatoid Arthritis, Systemic lupus erythematosus, Diabetes Mellitus, Multiple Sclerosis etc. C. Immunodeficiency Diseases: – Occur when one or more of the components of the immune system are inactive Congenital – Severe combined immunodeficiency (SCID) E.g. Adenosine deaminase (ADA) deficiency. Deficiency of this enzyme results in an accumulation of deoxyadenosine, which in turn leads to:  1- increase in S-adenosylhomocysteine affecting the differentiations of lymphocytes 2- prevents DNA synthesis, so affecting T and B cells division. Extrinsic – Cancer and HIV causing AIDS.

Organ Transplants/Rejections: Types of Organ Transplants Autograft: tissue graft from one body site to another (same person) Isograft: graft received from a genetically identical donor (identical twin) Allograft: graft received from genetically non-identical donor (same species) Xenograft: graft received from another species of animal Transplant rejection: mediated by the immune system (especially T cells, NK, antibodies)

Cytokines Cytokines are a category of signaling molecules used extensively in intercellular communication. They are regulators of host responses to infection, immune responses, inflammation, and trauma Cytokines can be classified as proteins, peptides, or glycoproteins Cytokines include Interleukins / lymphokines Interferons (IFNs), Tumor Necrosis Factors (TNFs) (causing the apoptosis), Transforming Growth Factors (TGFs) Colony-stimulating factors (CSFs) (causing cells to proliferate and differentiate).

IMMUNOMODULATORS

DEFINITION Immunomodulators are drugs which either suppress the immune system –Immunosuppressants or stimulate the immune system –Immunostimulants

Immunosuppressant

Immunosuppressants Glucocorticoids: Prednisolone, Methylprednisolone, Prednisone. Calcineurin inhibitors Cyclosporine Tacrolimus Sirolimus Antiproliferative / antimetabolic agents Azathioprine Mycophenolate Mofetil Everolimus Others – methotrexate, cyclophosphamide, thalidomide and chlorambucil Antibodies Antithymocyte globulin (ATG) Anti CD3 monoclonal antibody: Muromonab-CD3 (OKT3) Anti IL-2 receptor antibody: Daclizumab, basiliximab Anti TNFα: Infliximab, Etanercept, Adalimumab Calcineurin activates the T cells of the immune system

MAJOR STEPS IN IMMUNE RESPONSES Antigen Antigen presenting Cell (macrophage, dendritic cell) CD4 T helper cell Primed CD4 T helper cell CD8 T cell Cytotoxic T cells Plasma cells 1 2 3 4 IL-1 IL-2 B cell CD 4 = cluster of differentiation, found on the surface of immune cells such as T helper cells, monocytes, macrophages, and dendritic cells. CD4+ T helper cells are white blood cells that are an essential part of the human immune system. They are often referred to as CD4 cells, T-helper cells or T4 cells. They are called helper cells because one of their main roles is to send signals to other types of immune cells, including CD8 killer cells. CD4 cells send the signal and CD8 cells destroy and kill the infection or virus. If CD4 cells become depleted, for example in untreated HIV infection, or following immune suppression prior to a transplant, the body is left vulnerable to a wide range of infections that it would otherwise have been able to fight.

Inhibitors of Immune Response (site of action) Antigen recognition: Immune Globulin IL-1production, cell proliferation: Corticosteroids T cell receptors/surface proteins: Muromonab-CD3 (OKT3), Anti-thymocyte globulin (ATG)  IL-2 gene expression (Cyclosporine, Tacrolimus), and IL-2 signal transduction (Sirolimus ) T cell proliferation & differentiation: Mycophenolate Azathioprine, Cyclophosphamide (all cell proliferation)

SITES OF ACTION OF IMMUNOSUPPRESSIVE DRUGS Antigen antigen presenting cell CD4 T helper Primed CD4 T helper cell CD8 T cell Cytotoxic T cells Plasma cells 1 2 3 4 IL-1 IL-2 X A B D E C

Drugs Prolonging Organ Transplantation Cyclosporine (Neoral) Tacrolimus (FK506, Prograf) Sirolimus (Rapamune) Mycophenolate mofetil (Cellcept) Prednisone, Methylprednisolone

 myasthenia gravis: neuromuscular disease that leads to varying degrees of skeletal muscle weakness ACHR: Acetylcholine receptor

Glucocorticoids Uses: Induce redistribution of lymphocytes: in peripheral blood lymphocyte counts Intracellular receptors – regulate gene transcription Down regulation of IL-1, IL-6 Inhibition of T cell proliferation Neutrophils, Monocytes display poor chemotaxis Broad anti-inflammatory effects on multiple components of cellular immunity Uses: Transplant rejection Bone Marrow transplantation Autoimmune diseases – RA, Systemic Lupus Erythematosus Psoriasis Inflammatory Bowel Disease (Crohn's disease and ulcerative colitis) , Eye conditions. Chemotaxis  is the movement of an organism in response to a chemical stimulus.

Toxicity Growth retardation Avascular Necrosis of Bone Risk of Infection Poor wound healing Cataract (a clouding of the lens in the eye which leads to a decrease in vision) Hyperglycemia Hypertension

CALCINEURIN INHIBITORS Calcineurin (CN) is a protein phosphatase which induces the transcription of interleukin-2 and activates the T cells of the immune system and can be blocked by drugs. Cyclosporine: Fat soluble peptide antibiotic Act at an early stage in the antigen receptor-induced differentiation of T cells and block their activation. Inhibit the gene transcription of IL-2, IL-3, IFN-γ, and other factors produced by antigen-stimulated T cells. Bind to the cytosolic protein cyclophilin (an immunophilin). This complex of cyclosporin and cyclophilin inhibits the phosphatase calcineurin. The drug also inhibits lymphokine production and interleukin release, leading to a reduced function of T-cells.

Uses: Organ transplantation: Kidney, Liver, Heart Rheumatoid arthritis Psoriasis and other skin conditions Aplastic anemia (is a rare disease in which the bone marrow and the hematopoietic stem cells that reside there are damaged,  causing a deficiency of all three blood cell types: RBC, WBC, and platelets). Toxicity : Renal dysfunction, Neurotoxicity, Tremor Hepatotoxicity, Hirsuitism Hypertension Hyperlipidemia Gum hyperplasia Hyperuricemia – worsens gout Calcineurin inhibitors + Glucocorticoids = Diabetogenic

Tacrolimus Macrolide antibiotic. It binds to the immunophilin FKBP1A, followed by the binding of the complex to calcineurin and the inhibition of its phosphatase activity. It prevents the cell from transitioning from the G0 into G1 phase of the cell cycle. Tacrolimus is more potent than cyclosporine and has less pronounced side-effects. Uses: Prophylaxis of solid-organ allograft rejection For liver, kidney, heart, pancreas, and bone marrow transplant applications. Topical preparation available for use in dermatitis and psoriasis.

Toxicity - Tacrolimus Nephrotoxicity Neurotoxicity-Tremor, headache, motor disturbances, seizures GI Complaints Hypertension Hyperglycemia Hypersensitivity, Risk of tumors, Risk of infections Increased risk of lymphomas,

Sirolimus (rapamune) Macrolide similiar to tacrolimus Contrary to cyclosporine and tacrolimus, drugs that affect the first phase of T lymphocyte activation, sirolimus affects the second one (namely signal transduction and lymphocyte clonal proliferation). It binds to FKBP1A like tacrolimus, however the complex does not inhibit calcineurin but another protein, mTOR (mammalian target of rapamycin). It indirectly inhibits several T lymphocyte-specific kinases and phosphatases, hence preventing their transition from G1 to S phase of the cell cycle. Sirolimus prevents B cell differentiation into plasma cells, reducing production of IgM, IgG, and IgA antibodies. Contrary = opposite

Uses: Prophylaxis of organ transplant rejection with other drugs Toxicity: Increase in serum cholesterol, Triglycerides Anemia Thrombocytopenia Hypokalemia Fever GI effects Risk of infection Risk of tumors Thrombocytopenia: decrease of thrombocytes, commonly known as platelets

ANTIMETABOLITES / ANTIPROLIFERATVE AGENTS

Azathioprine (Imuran ) An imidazolyl derivative of 6-MP The main immunosuppressive cytotoxic substance. It is non-enzymatically cleaved to mercaptopurine, that acts as a purine analogue and an inhibitor of DNA synthesis. By preventing the clonal expansion of lymphocytes in the induction phase of the immune response, it affects both the cell and the humoral immunity. Uses Prevention of organ transplant rejection Rheumatoid arthritis, systemic lupus erythematosus Toxicity Bone marrow suppression- leukopenia, thrombocytopenia, anemia Increased susceptibility to infection Hepatotoxicity, Alopecia, GI toxicity

Mycophenolate Mofetil Prodrug  Mycophenolic acid Inhibits Inosine monophosphate dehydrogenase (IMPDH) enzyme (the IMPDH enzyme in guanine synthesis is a major target for both antitumor and immunosuppresive drug design.) T, B cells are highly dependent on this pathway for cell proliferation Selectively inhibits lymphocyte proliferation & function , Antibody formation, cellular adhesion, migration

Prophylaxis of transplant rejection Uses Prophylaxis of transplant rejection Combination: Glucocorticoids, Calcineurin Inhibitors Toxicity GI (Diarrhea) Hematological (Leukopenia) Risk of Infection Increased incidence of lymphomas and other malignancies Drug Interaction Decreased absorption when co-administered with antacids Acyclovir, Ganciclovir compete with mycophenolate for tubular secretion

Antibodies Against lymphocyte cell-surface antigens Polyclonal / Monoclonal Antibodies are used as a quick and potent immuno-suppression method to prevent the acute rejection reaction

Antibodies Antithymocyte Globulin Monoclonal antibodies Anti-CD3 Monoclonal antibody E.g. Muromonab-CD3 Anti-IL-2 Receptor antibody E.g. Daclizumab, Basiliximab)

Anti-thymocyte Globulin Purified gamma globulin from serum of rabbits immunized with human thymocytes Cytotoxic to lymphocytes & block lymphocyte function Uses Treatment of acute transplant rejection Toxicity Hypersensitivity Risk of infection, Malignancy

Anti-CD3 Monoclonal Antibody (Muromonab-CD3 ) Binds to CD3, a component of T-cell receptor complex involved in antigen recognition cell signaling & proliferation Uses: Treatment of acute organ transplant rejection Toxicity “Cytokine release syndrome: High fever, Chills, Headache, Tremor, myalgia, arthralgia, weakness Prevention: Steroids

Anti-IL-2 Receptor Antibodies E.g. Daclizumab and Basiliximab Bind to IL-2 receptor on surface of activated T cells  Block IL-2 mediated T-cell activation Uses Prophylaxis of Acute organ rejection Toxicity Anaphylaxis, Opportunistic Infections

Anti-TNF Agents Infliximab E.g. Infliximab (Remicade), Etanercept (Enbrel), Adalimumab (Humira) Infliximab Uses Rheumatoid arthritis Psoriasis Psoriatic arthritis Ankylosing spondylitis Toxicity Infusion reaction – fever, urticaria, hypotension, dyspnoea Opportunistic infections – TB, RTI, UTI Infusion related reactions include hypersensitivity reactions and cytokine release syndromes. 

Etanercept Adalimumab Uses: Rheumatoid arthritis Fusion protein produced through expression of recombinant DNA. It is TNFα inhibitor ( TNF is a cytokine that  attract white blood cells to sites of inflammation. Uses: Rheumatoid arthritis Adalimumab Recombinant human anti-TNF mAb Uses : moderate to severely active crohn’s disease Fc = fragment crystallizable

LFA-1 Inhibitor - Efalizumab Monoclonal Ab Targeting Lymphocyte Function Associated Antigen Blocks T-cell Adhesion, Activation, Trafficking. Uses Organ transplantation Psoriasis - Withdrawn from the market due to fatal brain infetion. - Lymphocyte function-associated antigen 1 (LFA-1) is found on all T-cells and also on B-cells, macrophages, neutrophils and NK cells and is involved in recruitment to the site of infection. It binds to ICAM-1 on antigen-presenting cells and functions as an adhesion molecule.