Immunosuppressant Drugs Lecture

• Immunosuppressant drugs are the subject of this lecture

Immunosuppressant Drugs

• Immune system responses can sometimes cause severe problems, such as rejection of transplanted organs
• An allograft is a graft of an organ or tissue from one individual (the donor) to another (the recipient).
• The recipient's immune system recognizes the allograft as foreign and triggers an immune response
• This immune response can damage the transplanted organ
• Transplant rejection is the process where the body rejects a transplanted organ
• Transplant rejection can occur rapidly (acute rejection) or over a long period (chronic rejection)
• Immunosuppressants treat graft-versus-host disease (GvHD), a complication of allogeneic tissue transplants like stem cell or bone marrow transplants
• Organ transplant rejection can occur despite close matching of the donated organ and the transplant patient
• Organ and tissue transplantation has become routine due to surgical and tissue typing improvements

Immunosuppressant Drug Actions

• Immunosuppressant drugs reduce rejection risks and protect the new organ
• These drugs block the immune system, making it less likely to react against the transplanted organ
• A wide variety of immunosuppressants reduce the risk of rejection in different ways
• Besides preventing organ/tissue rejection, immunosuppressants treat autoimmune diseases like psoriasis and rheumatoid arthritis (RA)
• Immunosuppressants also treat Crohn's disease, alopecia areata, multiple sclerosis (MS), and systemic lupus erythematosus (SLE)
• More autoimmune diseases treated by it include autoimmune hemolytic anemia and acute glomerulonephritis

Immunosuppressant Drug Classification

• Autoimmune diseases mean the immune system loses its recognition characteristic and attacks the body's own antigens
• Immunosuppressant drugs are classified into five categories based on their molecular mode of action
• Immunophilin-binding drugs inhibit cytokine production or function
• Glucocorticoids alter the gene expression of immune-regulating proteins like cytokines
• Cytostatic/cytotoxic drugs affect cell division and growth
• Immunosuppressive antibodies block T cell surface molecules involved in signaling immunoglobulins
• Miscellaneous immunosuppressants: Includes drugs such as interferons, opioids, and fingolimod

Types of Immunophilin-binding drugs

• Calcineurin inhibitors: includes Cyclosporine, and Tacrolimus (FK506)
• Antiproliferative drugs: includes Sirolimus (Rapamycin), Everolimus, Biolimus A9 (umirolimus), Myolimus, Novolimus, and Zotarolimus

Types of Cytostatic/Cytotoxic drugs

• Inhibitors of purine or pyrimidine synthesis (antimetabolites): includes Azathioprine, Myclophenolate Mofetil, Leflunomide, and Methotrexate
• Alkylating agents: includes Cyclophosphamide

Types of Immunosuppressive antibodies

• Antilymphocyte globulins (ALG)
• Antithymocyte globulins (ATG)
• Rho (D) immunoglobulin
• Basiliximab
• Daclizumab
• Muromonab-CD3

Immunosuppressant Drug Specifics

• Some immunosuppressants have a diffuse effect on the immune system
• Other immunosuppressants have specific targets
• Drugs with diffuse effects cause more adverse effects
• The effectiveness of specific drugs may be reduced if their action is bypassed by alternative metabolic pathways, resulting in resistance
• Treatment protocols use drug combinations (2-4 agents) to minimize adverse effects and prevent resistance
• After transplant, most patients receive a combination of drugs from the main groups, such as Cyclosporin, Azathioprine, Prednisolone, and Basilixmab
• Over time, drug doses and the number of drugs taken are reduced as rejection risks decrease
• Most patients take at least one immunosuppressant for life

Immunophilin-binding drugs Details

• Immunophilins are abundant endogenous cytosolic proteins
• Immunophilins catalyze the cis-trans isomerization of proline residues within proteins
• Immunophilins aid in protein folding
• Examples of immunophilins: FKBP-12 and cyclophillin
• These are intracellular binding proteins of several immunosuppressive drugs
• Immunophilin-binding drugs mainly inhibit cytokine gene expression or function
• Cytokines are soluble, antigen-nonspecific, signaling proteins
• Cytokines bind to cell surface receptors on various cells
• Interleukin-2 (IL-2) cytokine is of particular interest
• IL-2 is a growth factor that stimulates the proliferation of antigen-primed (helper) T cells
• These T cells produce more IL-2, IFNɣ, and TNFα
• IL-2, IFNɣ, and TNFα collectively activate natural killer cells, macrophages, and cytotoxic T lymphocytes
• Calcineurin inhibitors interfere with the production of IL-2. Examples: Cyclosporine, and Tacrolimus (FK506)
• Drugs inhibiting IL-2 action: Sirolimus (rapamycin) and Everolimus

Cyclosporin Details

• Cyclosporine (CsA) is a lipophilic cyclic polypeptide of 11 amino acids
• Cyclosporine is extracted from the soil fungus Tolypocladium inflatum
• Cyclosporine suppresses cell-mediated immune reactions, while humoral immunity is less affected
• Cyclosporine blocks T cell activation by inhibiting interleukin-2 (IL-2) production
• Cyclosporine inhibits Calcineurin, a phosphatase necessary for dephosphorylation of transcription factor activity
• Cyclosporine then inhibits T cell proliferation and differentiation
• After diffusing into the T cell, CsA binds to cytosolic immunophilin protein, cyclophilin
• Cyclophilin acts as CsA intracellular receptors
• The Cyclosporine-cyclophilin complex inhibits Calcineurin
• Calcineurin normally activates IL-2 transcription
• T-cell receptor (TCR) activation normally increases intracellular Ca2+
• Ca2+ activates Calmodulin to activate calcineurin
• Calcineurin dephosphorylates the transcription factor NFATc (cytosolic Nuclear Factor of Activated T cells)
• NFATc moves to the nucleus of the T-cell
• Once there, it stimulates the transcription of genes for IL-2, lymphokinines, and related cytokines
• Cyclosporin induces mitochondrial swelling and dysfunction, leading to cell apoptosis
• CsA prevents the mitochondrial permeability transition pore from opening
• CsA's mitochondrial effects are not the primary mechanism of action for clinical use

Cyclosporin Pharmacokinetics

• Cyclosporine can be administered orally or by IV infusion
• It is slowly and incompletely absorbed from the gastrointestinal tract (GIT)
• Peak levels of cyclosporine are reached after 2-4 hours
• Elimination half-life of cyclosporine is 24 hours
• Oral absorption is delayed by fatty meals
• Cyclosporine is typically available in soft gelatin capsules (microemulsion) for higher bioavailability, unaffected by food
• 50-60% of cyclosporine accumulates in blood (erythrocytes & lymphocytes)
• Cyclosporine is extensively metabolized by liver CYP-450, primarily by hepatic CYP3A4
• Cyclosporine is mainly excreted through the biliary route
• About 6% of cyclosporine is excreted in urine

Cyclosporin uses

• Cyclosporine (CsA) prevents rejection of kidney, liver, and cardiac allogeneic transplants
• Cyclosporine is most effective in preventing acute rejection of transplanted organs
• Most effective when combined with corticosteroids and an antimetabolite (mycophenolate mofetil)
• Cyclosporine is also used to treat autoimmune disorders
• It is typically used for severe, active rheumatoid arthritis, and recalcitrant psoriasis that does not respond to other therapies

Cyclosporin Adverse Effects

• Many adverse effects are dose-dependent; monitor blood levels of the drug
• Nephrotoxicity is an important adverse effect, so monitor kidney function
• Reduction of the CsA dosage can reverse nephrotoxicity in most cases
• Irreversible nephrotoxicity can occur in 15% of patients
• Symptoms of nephrotoxicity are enhanced with NSAIDs and aminoglycosides antibiotics
• Liver dysfunction
• Hypertension, hyperkalemia, so K-sparing diuretics should not be used
• Hyperglycemia
• Multiple infections, specifically viral infections like Herpes and cytomegalovirus

Cyclosporin Drug Interactions

• Lymphoma (predisposes recipients to cancer)
• Hirsutism
• Neurotoxicity (tremor, numbness, and tingling)
• Gingival hyperplasia
• Anaphylaxis after I.V. administration
• Clearance of cyclosporine is enhanced by co-administration of CYP450 inducers
• Examples of inducers: Phenobarbitone, Phenytoin & Rifampin
• This causes rejection of the transplant
• Clearance of cyclosporine decreases when co-administered with cimetidine, erythromycin, or ketoconazole and Grapefruit juice
• This causes cyclosporine toxicity
• Additive nephrotoxicity with NSAIDs and aminoglycosides

Tacrolimus Details

• Tacrolimus (TAC, originally called FK506) is a macrolide antibiotic isolated from soil actinobacteria
• Streptomyces tsukubaensis is main source

Tacrolimus Function

• Tacrolimus (TAC) exerts its immunosuppressive effect with the same mechanism as cyclosporine but binds to a different immunophilin protein
• Different immunophilin protein: FKBP-12 (FK506-binding protein-12)
• This creates a new complex (tacrolimus-FKBP12 complex) that inhibits the phosphatase activity of calcineurin
• This prevents dephosphorylation and translocation of nuclear factor of activated T-cells (NFATc)
• As a result, gene transcription of cytokine IL-2 is inhibited
• Tacrolimus inhibits the transcription for genes encoding IL1, IL-3, IL-4, IL-5, GM-CSF, and TNF-α

Tacrolimus Pharmacokinetics

• Tacrolimus (TAC) may be administered orally, IV, or as topical preparations (creams or ointment)
• GI absorption of TAC is incomplete and variable and reduced by fat and carbohydrate meals
• TAC potency is 10-100 times greater than CsA
• The half-life after IV adminstration is 9-12 hours
• Tacrolimus is highly bound to plasma proteins and concentrated in erythrocytes
• Undergoes hepatic metabolism by the CYP3A4 isozyme, so the same drug interactions with CsA occur
• At least one Tacrolimus metabolite has immunosuppressive activity
• Tacrolimus is mainly excreted in bile (>90%), a minimal amount is excreted in urine

Tacrolimus Use

• Tacrolimus (TAC) can be used as cyclosporine
• For use with Organ and stem cell transplantation
• Liver and kidney transplantation
• Also given with corticosteroids and/or an antimetabolite
• Cyclosporine studies show that Tacrolimus use reduces acute rejection
• Useful to treat dermal symptoms linked to autoimmune disorders (dermatitis and psoriasis)
• Can also be used to topically treat eczema
• Tacrolimus suppresses inflammation as steroids do, yet not as strong
• Tacrolimus can be used directly on the face without thinning the skin, whereas topical steroids cannot

Tacrolimus Adverse Effects

• Nephrotoxicity (more than CsA)
• Neurotoxicity; tremor, seizures, and hallucinations
• (More than CsA)
• Insulin-dependent diabetes mellitus
• GIT disturbances, blurred vision, and insomnia
• Hyperkalemia
• Mild hypertension
• Anaphylaxis and itching
• No hirsutism or gum hyperplasia
• Drug interactions: similar to CsA

Tacrolimus vs Cyclosporin

• TAC is more favorable than CsA because:

• TAC is 10-100 times more potent than CsA with immunosuppression

• TAC is linked to reduced rejection episodes

• TAC can be combined with lower doses of glucocorticoids

• TAC has a reduction to cardiovascular toxicities: hypertension and hyperlipidemia

• TAC more nephrotoxic and neurotoxic, however

Sirolimus (Rapamycin) Details

• Sirolimus (SRL) is a macrocyclic lactone antibiotic
• First discovered as a product of the bacterium Streptomyces hygroscopicus in a soil sample from Rapa Nui, pacific island.
• It was initially marketed under the name rapamycin

Sirolimus (Rapamycin) Mechanism of Action

• Sirolimus inhibits T- and B-lymphocyte activation and clonal proliferation from antigenic and cytokine response
• Sirolimus inhibits mitogenic response to IL-2
• Sirolimus binds to cytosolic protein FKBP12, but instead of inhibiting calcineurin, the Sirolimus-FKBP12 complex inhibits the mammalian target of rapamycin 1 called mTOR1
• mTOR1 is a serine-threonine kinase for many cellular function such as cell-cycle progression, DNA repair, and protein translation
• Binding of Sirolimus-FKBP12 complex to mTOR1 inhibits its function
• This inhibits cytokine-activated T-cell and B-cell clonal proliferation
• Inhibiting G1 to S phase cell cycle and blocking immunoglobulin production
• SRL does not lower IL-2 production but interferes with the IL-2 signal transduction pathway

Sirolimus (Rapamycin) Pharmacokinetics

• The drug is availble as oral preparations
• It is readily absorbed from GIT, rate decreased by fat content
• A loading dose is needed at initiation
• SRL is extensively bound to plasma proteins (~92%) and has long half-life of (57-63 hrs) than CsA and Tacrolimus
• SRL is metabolized by CYP3A4 isozyme and has drug-drug interactions as SRL ,CsA and Tacrolimus
• SRL increases the drug concentrations of CsA, blood level monitoring is vital
• SRL and its metabolites are predominantly eliminated by feces

Sirolimus (Rapamycin) Therapeutic Uses

• SRL has both anti-proliferative and immunosuppressive effects
• in renal, and cardiac transplantation, (used mainly combined with an antimetabolites and corticosteroids)
• SRL is often utilized in calcineurin inhibitor withdrawal protocols
• used for patients who are free from rejection during the 1st 3 months post-transplant
• sirolimus has been used with coronary stents, to prevent restenosis in coronary arteries following balloon angioplasty
• Halting graft vascular disease, endothelial cells, vascular smooth muscles and reducing proliferation
• Used for Hematopoietic stem cell transplant recipients.

Sirolimus (Rapamycin) Adverse Effects

• Hyperlipidemia (elevated cholesterol and triglycerides in 38%- 57% of cases), treatment to statins and Gemfibrozil,
• Drug combinations of CsA and SRL or TAC and SRL increase the incidence of nephrotoxicity more than just CsA or TAC
• Headache, nausea and diarrhea
• Blood changes
  • leukopenia,
  • Thrombocytopenia
  • anemia treatment. With iron & Erythropoietin
• Impaired wound healing obese and diabetic
• Post-transplant surgery

Everolimus Details

• It is a synthetic derivative of sirolimus
• A 40-O-(2-hydroxymethyl)derivative
• It functions as an mTOR1 inhibitor
• It is currently used as an immunosuppressant to prevent rejection of organ transplants
• It is used as targeted therapy for use in cancers
• Everolimus blocks the growth factor-driven cell proliferation
• It stops IL-2 Signal Transduction pathway
• It stops cellular responses to IL-2

Everolimus Mechanism Of Action

• Everolimus is a mTOR1 inhibitor, With high affinity it binds to the FK-binding protein (FKBP-12), forming a drug complex

• The drug complex can inhibite the activation of mTOR1

• Inhibits the

  • activity of effectors downstream in p70S6 kinase,
  • Block in cells from G1 into S phase,
  • Cell growth arrest and apoptosis

• Cytokine-driven T-cell and B- cell clonal proliferation

• Inhibition of the expression of Hypoxia-inducible factor (HIF) the expression of vascular endothelial growth factor in anticancer effect

• mTOR1 is inhibited for reduction in

  • Cell proliferation
  • Angiogenesis
  • Glucose uptake.

Everolimus Pharmacokinetics

• the drug is given orally 5-70 mg/day
• Rate is decreased by high fat
• Peak are reached 1-2 hrs
• The drug is bond to a plasma protein 74%
• A half-life is 30 hours
• It's metabolized by the CYP3A4 isozyme, The drug-drug interactions of SRL,CsA and Tac
• Its is eliminated Mainly in feces >80

Everolimus Uses

• Used to prevent organ transplants
• Used to treat renal cell cancer
• Also, can be as eluting coronary stents

Everolimus Adverse Effects

• Can lead to High blood presssure 30% of cases
• Headaches,nausuea,diarreah,Anorexia and fatigue
• Blood change
• Shortness, breath, fever
• liver enzymes

Glucocorticoid Details

• Glucocorticoids were the 1st Pharmacologic agents used
• immunosuppressives for transplantation
• UsedVarious autoimmune disorders.

Glucocorticoids have both anti-inflammatory Actions + immunosuppresant effects

• Used in attenuating rejection episodes
• They are Prednisone,prednisolone, Methylprednisolone, and betamethasone dexamethasone

Glucocorticoid Mechanism Of Action

• Binding to Cell via receptors
• GR translocate and interact to nucleus With DNA that regulates gene transcription
• Involved in inflammatory responses - Decrease production of inflammatory mediators - prostaglandins, - leukotrienes, - histamine, PAF, - bradykinin, stimulatory action -Annexin 1 -proinflammatory cytokines decrease - IL-2 - TNF
• Stabilize Lysosomal membranes.
• *Decrease Generation
  • IgG from oxide
  • Inhibit macrophages
  • Suppress cell
  • Lymporocyte decrease

Glucocorticoid Pharmacokinetics

• they can be administered various ways

• topical preparations

• They can bind to coricosteriod-binding (CBG) Albumen

• There halflife is 2-8 hours, different duration, variable dependaning on preparation -

• CORTISOL is 8-12 hours

• Predsolne is 18 -35hrs Dexa is 36-54 hrs

• Metabolized at - CYP3A4 *non microsomal

• Active or Converted in vivo; prednisolone

Glucocorticoid Therapeutic Uses

• They function in therapy

• Used to treat rejection

• Haematopoietic stem transplantation use during episodes

• Treats temporal arthritis

• Alergic

  • Asthma Rhintis

• Also can aid as replacement therapy in adrenal insufficiency.

Glucocorticoid Adverse Reaction

• Multiple side effects such as a libility to infections

• Increase Insulin release

Skin- Decrease

• Calcium reuptake, osteoporosis
• Weight increase due fat deposition
• Hypercortisolemia from 3xcess use cushing syndrome
• Decreases in Adrenal when stopped
• Impared memor and attention
• Break down Muscle, with weight gain
• Affect Central nervous
• Cause Anovulation irregular menstruation
• Glaucoma
• Hypercholesterolemia
• Hypertension
• Peptic uclers
• Hirsutism