Immunosuppressants Prof Alhaider 1431 H I II Definition

Immunosuppressants Prof. Alhaider, 1431 H I. II. Definition Clinical Uses (Organ transplants & Autoimmune diseases) Pre-requisite to understand immunosuppressive drugs (Basic immunology). Review of immune system (see Table 56 -1) III. IV. I. III. IV. Cell mediated vs humoral immunity Importance of cytokines Immunophilins Calcineurin

Classification of Immunosuppressant (Based on Mechanism of Action) • A) Antiprolifirative Agents 1) Drugs Acting on Immunophilins: a) Selective Inhibitors of Cytokine production ) (Calcineurin Inhibitors) (e. g: Cyclosporine; Tacrolimus) b) Inhibitor of cytokine function (e. g. Sirolimus). 3) Antimetabolites (Azathioprine; Mycophenolate Mofetil) 4) Alkylating Agents (Cyclophosphamide) B) Lymphocyte Depletion Agents 1) Corticosteroids 2. Immunosuppressive Antibodies a) Polyclonal Antibodies (Antilymphocyte Globulin) b) Monoclonal Antibodies (Selective inhibitors of IL 2 (Basiliximab; Daclizumab)

Immunosuppressant Classes Non-selective • Corticosteroids Ø Prednisone (PO) & Methylprednisolone (IV) • Antimetabolite (DNA synthesis inhibitors) Ø Azathioprine & Myclophenolate mofetil q Immunoglobulins Ø Anti-lymphocyte antibodies Selective • Ø Ø • Calcineurin Inhibitors Cyclosporine Tacrolimus (Rapamycin) Selective IL-2 Receptor antagonists Ø Basiliximab, Daclizumab & Infliximab q Mamalian target of Rapamycin (m. TOR) inhibitors ü Sirolimus

Selective Inhibitors of Cytokine Production (Drugs Acting on Immunophilins) • 1) Cyclosporine (Cyclic peptide from Soil Fungus (1971) – MOA: (See Figure 40. 4) • Cs. A binds to cyclophillin forming a comlex Bind to Calcineurin dephosphorylation NFATc Synthesis of IL 2 proliferation of T cells • Thus, decreases the level of IL-2, the primary chemical stimulus for increasing the number of T lymphocytes • Note: Suppress only cell immunity with no effect on humoral immunity.

– PK • Cs. A available as oral (capsule) or parental (i. v) • Oral bioavailability (20 -50%), it undergoes extensive hepatic metabolism by Cyt. P 450 (CYP 3 A 4) (Affected by some drugs EXAMPLES) and mainly excreted in the bile.

– Clinical Uses of Cyclosporine: • 1) Drug of choice for preventing organ transplant rejection in combination with steroids and other immunosuppressants. • 2) Severe active rheumatoid arthritis, as alternative for methotrexate • 3) Lower doses (7. 5 mg/kg/d) for autoimmune diseases (Uveitis; RA; early Rx of DM 1) • 3) Psoriasis and asthma ? . – Side Effects (remember most immunosuppressant are very toxic) • Dose-dependent nephrotoxicity ( Risk of Rejection); enhanced of given with other nephrotoxic drugs (Aminoglycosides; NSADs) • Hepatotoxicity • Neurotoxicity as tremor and hallucination • Infection How? • Lymphoma and cancer How? • Hypertension; hyperlipedemia; Hyperkalemia; D. M; Osteoporosis Hirsutism and gum hyperplacia (So What)

• 2. Tacrolimus (FK 506): – More potent than Cyclosporine – MOA: Similar to Cyclosporine (Calcineurin Antagonist) but it bind to different immunophilin (FKBP) Figure 40. 6. – PK: Almost Similar to Cyclosporine – Side Effects: differ from Cyclosporine, that it ((Tac) has no hirsutism or gum hyperplasia but may show more hyperglycemia than cyclosporine. – Note: It is like cyclosporine, could lead to nephrotoxicity and hyperglycemia (more hyperglycemia than cyclosporine) , and hyperlipedemia.

• Clinical uses of Tacrolimus: ØPreferred over Cs. A because: Ø of more potency (50 -100 times more potent than cyclosporine). Ølower rejection episodes, Ø and lower doses of glucocorticoids are used with lower side effects ØBetter first choice for woman? ØSevere refractory atopic dermatitis, local application of an ointment ØAn ointment for psoriasis.

• 3. Sirolimus (Rapamycin Maclolides) – MOA: • 1) Binds to the same immunophilin as Tacrolimus, but does not form a complex with calcineurin, instead, it binds to m. TOR (Mammalian Target of Rapamycin) which is essential for many cellular functions (See Figure 40. 6) • 2) Sirolimus does not affect IL-2 production, unlike Cs. A & TAc, rather inhibits T-cell response to it (Blocks cytokine-stimulated cell proliferation) • 3) Potent inhibitor of B-cell proliferation and immunoglobulin production (humor immunity)

• Uses of Sirolimus: – 1) can be used together with cyclosporine (to increases the activity of cyclosporine for organ transplanted patients. – 2) As replacement of cyclosporine if transplanted patient developed cancer of skin or lips. – 3) used in cardiac catheter stint to prevent stenosis? ? – 4) as an ointment for atopic dermatitis and psoriasis • Side Effects: – 1) Pneumonitis – 2) hyperlipedemia (more then calcineurinantagonist)

• Antiproliferatives (Continue…) • 2. Antimetabolites (Cytotoxic Drugs) – 1) Azathioprine: is a prodrug of mercaptopurine. • Cytotoxic, rarely used as chemotherapeutic drug, but commonly used for immunosuppression. • It is a pro-drug converted in the body to the active metabolite, 6 -mercaptopurine and thioinosinic acid. • MOA: (see Figure) – Simply, it inhibits purine synthesis (antimetabolite), thus interfering with nucleic acid metabolism and lead to inhibition of the proliferation of leukocytes and lymphocytes. – Why it is considered as cytotoxic agent? – Because the purine analog of Azathioprine can destroy lymphoids cells. – Why it is very important to know the structure of azathioprine? .

Metabolic pathway for azathioprine 6 -thiouracil (-) Xanthine Oxidase Alloburinol Nonenzymatic AZA HPRT 6 -MP TPMT 6 -MMP thioiosinic acid (TIMP) TPMT 6 -MMP ribonucleides 6 -thioguanine ( 6 -TG)

• Cliniclal Uses of Azathioprine (Imuran. R) – 1) maintenance of renal allograft and other transplantations together with steroids and cyclosporine. – 2) Can be used for glomerulonephtitis and SLE; RA; Crohn’s disease and multiple sclerosis. • Side Effects – 1) it is like cyclosporine, not teratogenic (Unlike TAC or Siro) but carcinogenic if given together with alkylating agents. (here higher doses are used as compared to autoimmune diseases. – 2) strong bone marrow suppression (Leucopenia; anemia; thrombocytopenia How? – 3) Hepatic dysfunction as increase AP and mild jaundice. – 4) Hypersensitivity reactions (as rashes, fever, diarrhea) Why? .

q. Adverse Effects: bone marrow suppression (leukopenia, thrombocytopenia, anemia), hepatotoxicity, ü Combination with ACEIs or cotrimoxazole can cause severe leukopenia in renal transplants Ø It can be given both orally and by IV

• 2) Mycophenolate Mofetil (Cellcept. R) – The most important discovery among the immunosuppressant agents. – MOA: (See Figure) • Mycophenolic acid acts as non-competitive, selective 7 reversible inhibitor of inosine monophosphate dehydrogenase • Decreases GMP, which is a key enzyme in the de novo pathway of purine synthesis. This leads to suppression of both B and T lymphocyte activation. • PK: Good oral absorption; – Side Effects • Less than azathioprine, Bone marrow suppresion (leukopenia and anemia); NV and diarrhea (decresed by Enteric-coated form). • Unlike azathiorine it is teratogenic.

– Clinical Uses • 1) As a replacement for the more cytotoxic drug, azathioprine in renal allograft patients as well as liver, heart et act. Why? • As replacement of azathioprine or cyclophosphamide for autoimmune diseases (RA, SLE (especialy before lupus nephritis); Glomerulonephritis • Has good oral bioavailability • Note: in renal or liver transplant, patients may take the followings: • Corticosteriods as prednisolone (Low dose) + cyclosporine or Tac + Mycophenolate Mofetil

– 3. Lefunomide: - A Pro-drug of an inhibitor ofn PYRIMIDINE synthesis rather than purine like azathioprine and mycophenolate. – Orally active used only for RA – Side effects: Alopecia; increase LFT, nephrotoxicity, teratogenicity. • 3. Alkylating Agents (e. g. Cyclophosphamide) – The most potent immunosuppressant – Destroys proliferating lymphoid cells (cytotoxic agent) also alkylate some resting cells (Thus, it is very toxic) – Clinical Uses: • Before the discovery of Mycophenolate, cyclophosphamide was the drug of choice for treatment of many autoimmune diseases like SLE; autoimmune hemolytic diseases and RA. – Side Effects • • Pancytopenia Hemorrhagic cystitis Infertility Teratogenic

B) Lymphocyte Depletion Agents • 1. Corticosteroids • The most commonly used immunosuppressant • MOA: – At biochemical level: act on gene expression, which lead to decrease synthesis of PGs; LKTs; cytokines and other signaling molecules that participate in immune response. – At the cellular level: they inhibit the proliferation of T lymphocytes (cell mediated) and slightly dampen humoral immunity (by increasing the catabolism of immunoglobulins). – At immunosuppressive doses, Corticosteroids are cytotoxic and continuous uses lowers Ig. G.

• Uses: – In combination with other immunossppressants for transplanted patients (To prepare the patients as well as maintenance). – To Rx acute rejection episodes (high doses) – To Rx undesirable immunoreactions (to drugs or asthma). – To autoimmune diseases (ITP; IBD; RA; SLE; GN) – Side Effects:

Ø Adverse effects: (revise endocrine system) Ø Increased blood pressure How? Ø hyperglycemia due to increased gluconeogenesis, insulin resistance, and impaired glucose tolerance ("steroid diabetes"); Ø Osteoporosis Ø Visceral and truncal fat deposition (central obesity) and appetite stimulation Ø Weight gain (water & salt retention) How? Ø Muscle breakdown (proteolysis), weakness; reduced muscle mass and repair Ø Increased skin fragility, easy bruising Ø Cataracts Ø Adrenal cortex suppression (NO ABRUPT WITHDRAWAL) Ø Increase tendency to infections How?

2. Immunosuppressive Antibodies a) Polyclonal Antibodies (Antilymphocyte Globulins) Definition: Thymocytes are considered as T-cell precursors. What are the differences between polyclonal and monoclonal antibodies? 1) Antithymocyte (Antilymphocyte) Globulins (ALG): this antisera can be obtained by immunization of large animals (e. g. rabbits) with human lymphoid cells. MOA: Antibodies bind to the surface of circulating T lymphocytes forming a comlex. This complex will be phagocytosed in liver or spleen and leading to destruction or inactivation of T cells. ALG mainly affects the cellular immunity with no effect on humoral, resulting in antibodies against these foreign proteins. PK: Administered by IM or slow IV infusion with long half-life of 3 -9 days Side Effects: 1) Mainly result from the introduction of foreign proteins obtained from heterogeneous serum (Anaphylactic and serum sickness reactions; Local pain and erythema at site of injection). 2) Chills & fever and Leukopenia & thrombocytopenia 3) Viral infections and skin rashes 4) Lymphoma and cancer

Polyclonal Antibodies (continue…) Clinical Uses of ALG : 1) Rx of hyperacute phase of allograft rejection 2) To prepare the bone marrow transplanted patient (Large doses of ALG for 7 days) 2) Immune globulin Intravenous (IGIV): - Prepared from a pool of thousands of healthy donors. Uses: 1) Refractory ITP Advantages: Has no antigenicity

B) Monoclonal Antibodies (Muromonab; Basiliximab; Abciximab; Daclizumab. 1) Muromonab-CD 3 (IL-2 -antagonist): From its name, it is murine monoclonal antibody that prepared by hypridoma technology and directed against the glycoprotien CD 3 antigen of human T cells. Used mainly for cases of acute allograft rejections of kidney, heart and liver. it is also used to deplete T cells from donor bone marrow before transplantation. Advantage over ALG: More specific and T lymphocytes return to normal within 24 hr. Side Effects: 1) Cytokine release syndrome (Anaphylactoid reactions) Why; and seizure (contraindication) Therefore it is not used.

Side Effect of Muromonab • Its use has been declined much because of multiple side effects and the emergence of newer and more selective antibodies therapy ØAnaphylaxis may occur ØCytokine release syndrome, flu-like to dangerous shock-like reactions can occur, & high fever ØCNS: Seizures, encephalopathy, cerebral edema & headache ØInfection like CMV ØContraindicated with pregnancy, breast feeding, history of seizures, uncompensated heart failure

• 2) Modified Types of monoclonal antibodies (e. g: Selective Inhibitors of IL 2): • Note: Monoclonal Antibodies are not limited for immunosuppression but could be utilized for other purposes (See Table 56 -3) • By using the genetic engineering, most murine amino acids of Muromonab have been replaced by human ones; producing monoclonal antibody designated humanized (e. g. Daclizumab; Transtuzumab). While the chimeric (Mixed) antibodies contain XI in their name (e. g. Abciximab; Infliximab; Rutuximab). • Clinical Uses: See Table 56 -3 • Advantages over polyclonal antibodies

B- Selective IL-2 Receptor Antagonists Basiliximab & Daclizumab • Basiliximab is a chimeric antibody composed of 25% murine & 75% human protein. Block IL • Daclizumab is humanized antibody composed of 90% human protein • Therapeutic Use: Ø Prophylaxis against acute rejection of kidney transplantation Ø Used in combination with steroids or Cs. A

Selective IL-2 Receptor Antagonists Basiliximab & Daclizumab (Continue…) • Mechanism of action: Ø They are anti-CD 25 antibodies Ø They bind to the -chain of the IL-2 R (CD 25 or TAC subunit) on the activated T-cells Ø Then, IL-2 binding to IL-2 R is prohibited & Tcell activation and proliferation are suppressed

VI- Selective IL-2 Receptor Antagonists Basiliximab & Daclizumab (Continue. . . ) • Pharmacokinetics: Given by IV route Ø Daclizumab has serum half-life of 20 days & receptor blockade for 120 days § Administered in 5 doses; the first 24 hours before transplantation and next 4 doses at 14 -days intervals Ø Basiliximab has serum half-life of 7 days § Administered in two doses; the first at 2 hours before transplantation & the second at 4 days after surgery

Selective IL-2 Receptor Antagonists Basiliximab & Daclizumab (Contiue. . ) • Adverse Effects: Ø Both are well-tolerated Ø Gastrointestinal toxicity is the major one Ø NO antibodies, of clinical relevance, to the drugs are produced Ø Infection & malignancy are not reported

• Alemtuzumab: • Humanized monoclonal antibody directed against CD-52, and produce profound depletion of T cells. • Used for refractory B- cell chronic lymphocytic leukemia. However, it is currently in use for organ transplant.

3 - Rho. D Immunoglobulin • Rho(D) Immune Globulin (Rhogam) Ø Rhogam is an immunoglobulin that recognizes the Rho(D) antigen Ø Prepared from pooled sera from Rhonegative volunteers immunized with D+ erythrocytes Ø It prevents erythroblastosis fetalis or hemolytic disease of the newborn Ø When a Rho(D)-negative mother carries a Rho(D)-positive fetus, mother becomes sensitized

Rho. D Immunoglobulin • It is usually given to the mother within 72 hours after the birth of Rh-positive baby • This would prevent hemolytic anemia that may occur in subsequent pregnancies • Adverse Effects: Ø Chills Ø Fever Ø Anaphylaxis (rare)

Rho(D) Immune Globulin: • – Used to prevent Rh hemolytic disease in newborn. – Thus, Rho(D) Immune Globulin antibodies are given to the mother within 72 Hrs after birth of Rh positive baby. – Uses: • Erythroblastosis Faetalis • Miscarriages