Pharmacology of immunomodulating drugs
Immune system :
The importance of the immune system is to protect the body
against harmful foreign molecules (living and non-living
pathogens) and defend against diseases.
Components of immune system:
1- Lymphoid organs and tissues
2- Leukocytes (WBCs)
3- Soluble proteins:
Immune system (cont’d)
1- Lymphoid organs and tissues
2- Leukocytes
- Granulocytes
- Monocytes (Phagocytes)
- Lymphocytes
3- Soluble proteins:
- Complement system.
- Acute phase proteins.
- Antibodies.
- Cytokines.(are soluble , signaling proteins that produced by
various population of immune cells and other cells to interact
with cell surface receptors on a variety of affecter cells and
they play many roles as pro-inflammatory, anti-nflammatory,
growth regulation and others).
Cytokines include
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Interleukins (ILs)
Interferons (IFNs),
Tumor Necrosis Factors (TNFs),
Transforming Growth Factors (TGFs)
Colony-stimulating factors (CSFs).
Mammalian Immunity
1- Innate immunity
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Non- specific, constitutive.
First line of defense. Present from birth.
No immunologic memory.
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Includes physical, chemical and biochemical barriers.
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Includes physical, chemical and biochemical barriers.
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Inflammation
2- Acquired Immunity
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It is secondary to the innate response.
Adaptive and specific.
Recognition ( self/ non-self or pathogenic discrimination).
Essential to the development of specific immunity is the
recognition of antigen.
Immunological memory (long lasting).
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Two types of specific immune response:
1- Cell-mediated immunity (CMI):
All immunologic activities in which cellular elements play a
direct role e.g. activation of antigen-specific T-lymphocytes.
2- Humoral immunity (HI):
It is directly dependent on the production of antigen –
specific antibody by B lymphocytes and involve the
coordinated interaction of antigen-presenting cells, T
lymphocytes and B-lymphocytes.
 Function of T helper cells:
Antigen presenting cells (APCs) present antigen on their
Class II MHC molecules (MHC2). Helper T cells recognize
these, with the help of their expression of CD4 co-receptor
(CD4+). The activation of a resting helper T cell causes it to
release cytokines and other stimulatory signals (green arrows)
that stimulate the activity of macrophages, killer T cells and B
cells, the latter producing antibodies. The stimulation of B
cells and macrophages succeeds a proliferation of T helper
cells.
3- Passive Immunity
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It is a form of induced immunity.
Antibodies are borrowed from another sources.
It usually gives short-term resistance (2 weeks – 6 months).
Two types are recognized:
- Natural Passive
e.g. Baby in uterus (placenta) and Breast-fed babies (milk)
- Artificial Passive
e.g. Gamma globulin injection. Extremely fast, but short lived
(e.g. snake venom)
Immune system (cont’d)
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In some instances, the response of immune system can
result in serious problems. For example, the introduction of
an allograft (that is, the graft of an organ or tissue from one
individual to another who is not genetically identical) can
elicit a damaging immune response, causing rejection of
the transplanted tissue. Transplantation of organs and
tissues (for example, kidney, heart, or bone marrow) has
become routine due to improved surgical techniques and
better tissue typing.
Another immune-related problem is the problem associated
with autoimmune diseases (e.g. SLE, RA, MS,
autoimmune hemolytic anemia, acute glomerulonephritis),
when the immune system fail to recognize the self antigen
and attack it.
Immunosuppressant drug are now utilized to inhibit
rejection of transplanted tissues and to treat the autoimmune
diseases.
Because of their severe toxicities when used as
monotherapy, a combination of immunosuppressive agents
(2-4 agents with different mechanisms of action), usually at
lower doses, is generally employed.
Immunosuppressant agents
I. Selective inhibitors of cytokine production or function:
1) Calcineurin inhibitors
 Cyclosporine
 Tacrolimus (FK506)
2) Sirolimus (rapamycin).
II. Inhibitors of cytokine gene expression
◦ Corticosteroids
(Prednisone,
Methylprednisolone, Dexamethasone)
Prednisolone,
III. Cytotoxic drugs
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Inhibitors of purine or pyrimidine synthesis
(Antimetabolites):
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Azathioprine
Myclophenolate Mofetil
Leflunomide
Methotrexate
Alkylating agents:
Cyclophosphamide
IV. Immunosuppressive antibodies
that block T cell surface molecules involved in signaling
immunoglobulins
◦ antilymphocyte globulins (ALG).
◦ antithymocyte globulins (ATG).
◦ Rho (D) immunoglobulin.
◦ Basiliximab
◦ Daclizumab
◦ Muromonab-CD3
V. Interferon
VI. Thalidomide
I. Selective Inhibitors of Cytokine Production and Function
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Cytokines are soluble, antigen-nonspecific, signaling proteins
that bind to cell surface receptors on a variety of cells.
Of particular interest when discussing immunosuppressive
drugs is IL-2 cytokine, a growth factor that stimulates the
proliferation of antigen-primed (helper) T cells, which
subsequently produce more IL-2, IFNɣ, and TNFα. These
cytokines collectively activate natural killer cells, macrophages,
and cytotoxic T lymphocytes.
Drugs that interfere with the production of IL-2, such as
cyclosporine, and Tacrolimus (FK506) are also known as
calcineurin inhibitors . Example of drugs that inhibit IL-2
action is sirolimus (rapamycin)
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Cyclosporine (CsA) is a lipophillic cyclic polypeptide
composed of 11 amino acids that is extracted from a soil
fungus (Tolypocladium inflatum).
Mechanism of action:
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Cyclosporine preferentially suppresses cell-mediated
immune reactions, whereas humoral immunity is affected to
a far lesser extent.
It acts by blocking activation of T cells by inhibiting
interleukin-2 production (IL-2).
It also decreases proliferation and differentiation of T cells.
After diffusing into the T cell, CsA binds to cytosolic
protein known as cyclophilin (immunophilin) that acts as
CsA intracellular receptors. Cyclosporine-immunophilin
complex inhibits calcineurin, a phosphatase necessary for
dephosphorylation of transcription factor NFATc (cytosolic
Nuclear Factor of Activated T cells). required for
interleukins synthesis (IL-2). NFATc suppresses cellmediated immunity.
Pharmacokinetics:
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Can be given orally or I.V. infusion. It is slowly and
incompletely absorbed from GIT.
Peak levels is reached after 2– 4 hours, elimination half life
is 24 h.
Oral absorption is delayed by fatty meal. CsA is usually
available in soft gelatin capsules, microemulsion that has
higher bioavailability-is not affected by food.
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50 – 60% of cyclosporine accumulates in blood
(erythrocytes & lymphocytes).
CsA is extensively metabolized by liver CYP-450, primarily
by hepatic CYP3A4.
Excreted mainly through the biliary route, and about 6% is
excreted in urine.
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Therapeutic Uses:
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CsA is used to prevent rejection of kidney, liver, and cardiac
allogeneic transplants.
CsA is most effective in preventing acute rejection of
transplanted organs when combined in a double-drug or tripledrug regimen with corticosteroids and an antimetabolite such a
smycophenolate mofetil.
CsA is used for the treatment autoimmune disorders like severe,
active rheumatoid arthritis, and recalcitrant psoriasis that does
not respond to other therapies.
Adverse Effects:
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Many of the adverse effects caused by CsA are dose
dependent; therefore, it is important to monitor blood levels
of the drug
Nephrotoxicity; critical to monitor kidney function.
Reduction of the CsA dosage can result in reversal of
nephrotoxicity in most cases, although nephrotoxicity may be
irreversible in 15% of patients. Symptoms of nephrotoxicity
is enhanced by co-administeration with NSAIDs and
aminoglycosides antibiotics.
Liver dysfunction.
Hypertension, hyperkalemia.(K-sparing diuretics should
not be used).
Hyperglycemia.
Multiple infections especially viral infections (Herpes cytomegalovirus).
Lymphoma (Predispose recipients to cancer).
Hirsutism
Neurotoxicity (tremor).
Gum hyperplasia.
Anaphylaxis may experienced after I.V.
Drug Interactions
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Clearance of cyclosporine is enhanced by co-administration
of CYP450 inducers (Phenobarbitone, Phenytoin & Rifampin
 rejection of transplant.
Clearance of cyclosporine is decreased when it is coadministered with erythromycin or Ketoconazole, Grapefruit
juice  cyclosporine toxicity.
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Tacrolimus (TAC, originally called FK506) is a macrolide
lactone antibiotic that is isolated from a soil actinobacteria
(Streptomyces tsukubaensis)
Mechanism of action:
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TAC exerts its immunosuppressive effect in the same
mechanism as CsA, except that it binds to a different
immunophilin protein , FKBP-12 (FK506-binding protein12) creating a new complex (tacrolimus- FKBP12 complex)
that inhibits calcineurin.
Pharmacokinetics:
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TAC may be administered orally , I.V., or some topical
preperations (ointment).
GI absorptin of TAC is incomplete and variable, reduced by fat
and carbohydrate meals.
TAC is from 10- to 100-fold more potent than CsA.
It has half-life after I.V. adminsteration is 9-12 hours.
It is highly bound to plasma proteins and is also concentrated in
erythrocytes.
It is undergoes hepatic metabolism by the CYP3A4 isozyme;
thus, the same drug interactions with CsA occur.
At least one metabolite of TAC has been shown to have
immunosuppressive activity.
Excreted mainly in bile and minimally in urine.
Therapeutic Uses:
as cyclosporine
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Organ and stem cell transplantation
Prevention of rejection of liver and kidney transplants
(given with a corticosteroids and/or an antimetabolite).
TCA is also used in treatment of dermal symptoms
associated with some autoimmune disorders (e.g. dermatitis
and psoriasis).
Adverse Effects:
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Nephrotoxicity (more than CsA)
Neurotoxicity; tremor, seizures, and hallucinations, (more than
CsA)
insulin-dependent diabetes mellitus
GIT disturbances
Hperkalemia
Mild hypertension
Anaphylaxis
NO hirsutism or gum hyperplasia
Drug interactions: as CsA
What are the differences between CsA and TAC ?
TAC is more favorable than CsA due to:
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TAC is 10 – 100 times more potent than CsA in
immunosupression capacity.
TAC has decreased episodes of rejection.
TAC is combined with lower doses of glucocorticoids., But
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TAC is more nephrotoxic and neurotoxic.
TAC has also been found to have a lower incidence of
cardiovascular toxicities such as hypertension and
hyperlipidemia, both of which are common disease states
found in kidney transplant recipients.
Sirolimus (SRL) is macrolide antibiotic
It was first discovered as a product of the bacterium
(Streptomyces hygroscopicus ) in a soil sample from a pacific
island known as Rapa Nui, hence it was initially marketed
under the name Rapamycin
Mechanism of action:
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Sirolimus is to bind the cytosolic protein FKBP12 (in a
manner similar to tacrolimus), but instead of inhibition of
calcineurin, Sirolimus-FKBP12 complex inhibits the
mammalian target of rapamycin1 (mTOR).
mTOR is a serine-threonine kinase that is essential for many
cellular functions, such as cell-cycle progression, DNA
repair, and regulation of protein translation
Binding of Sirolimus-FKBP12 complex to mTOR blocks
the activated T -cells proliferation, B cell proliferation &
immunoglobulin production.
Unlike CsA and TAC, SRL does not owe its effect to
lowering IL-2 production but, rather, to inhibiting the
cellular responses to IL-2.
Pharmacokinetics:
• The drug is available only as oral preparations.
• It is readily absorbed from GIT (rate is decreased by high-fat
meals)
• A loading dose is required at the time of initiation of therapy.
• SRL is extensively bound to plasma proteins (~ 92%) and
has a long half-life (57-63 hours) compared to those of CsA
and TAC.
• SRL is metabolized by the CYP3A4 isozyme and has the
same drug-drug interactions as CsA and TAC.
• Due to competition in protein binding sites, SRL increases
the drug concentrations of CsA, and careful blood level
monitoring of both agents must be employed to avoid
harmful drug toxicities uppon combined therapy.
• SRL and its metabolites are predominantly eliminated in the
feces.
Therapeutic Uses:
SRL has both anti-proliferative and immunosuppressive effects
(equipotent to CsA).
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In renal transplantation(used mainly combined with CsA
and corticosteroids)
To limit the long-term side effects of the calcineurin
inhibitor, SRL is often utilized in calcineurin inhibitor
withdrawal protocols in patients who remain rejection free
during the first 3 months posttransplant.
Heart allografts
In halting graft vascular disease (SRL-coated stents inserted
into the cardiac vasculature inhibit restenosis of the blood
vessels by reducing proliferation of the endothelial cells).
Hematopoietic stem cell transplant recipients.
Adverse Effects:
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Hyperlipidemia (elevated cholesterol and triglycerides),
The combination of CsA and SRL or TAC and SRL are
more nephrotoxic than CsA or TAC alone
headache, nausea
thrombocytopenia.
and
diarrhea,
leukopenia,
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Impaired wound healing especially in obese and diabetic
patients which may represents a problem immediately
following the transplant surgery.
The corticosteroids were the first pharmacologic agents to
be used as immunosuppressives both in transplantation and
in various autoimmune disorders.
They have both anti-inflammatory
immunosuppressant effects.
action
and
II. Inhibitors of Cytokine gene expression
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The corticosteroids were the first pharmacologic agents to be
used as immunosuppressives both in transplantation and in
various autoimmune disorders.
They
have
both
anti-inflammatory
immunosuppressant effects.
action
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They are still one of the mainstays for attenuating rejection
episodes. The most common agents are Prednisone,
prednisolone, methylprednisolone, and dexamethasone
Mechanism of action:
On entering cells, they bind to the glucocorticoid receptor (GR).
The glucocorticoid-GR complex translocates into the nucleus and
interacts with DNA to regulates the gene transcription of .
Among the genes affected are those involved in inflammatory
responses.
- Decrease production of inflammatory mediators as
prostaglandins, leukotrienes, histamine, PAF, bradykinin mainly
by their inhibitory action on annexin-1 (a phoshplipase A
inhibitor).
- Decrease production of a wide array of proinflammatory
cytokines like IL-1, IL-2,IL-3,…, TNF-, GM-CSF.
- Stabilize lysosomal membranes.
- Decrease generation of IgG, and nitric oxide.
- Inhibit antigen processing by macrophages.
- Suppress T-cell helper function
- Decrease T-lymphocyte proliferation.
Pharmacokinetics:
- Corticosteroids may be administered by a variety of routes.
Most are active when given orally, and parentrally . In
addition topical preparations, eye/ear/ nasl drops and
aerosoles are also available.
- Corticosteroids (~90%) bind to corticosteroid-binding
globulin (CBG) and to albumin with variable tendencies.
- Plasma half-life 2-8 hours, with variable durations depending
on preparation ;(8-12 hrs for SAGCs e.g. Cortisol, 18-36 hrs
for IAGCs e.g. Predinsolne, and 36-54 hrs for LAGCs e.g.
Dexamethasone, Betamethasone).
- Generally GCs are metabolized in the liver by both
microsomal (mainly CYP3A4 & CYP2D6) and nonmicrosomal enzymes, where they are reduced and conjugated
(glucourinate and sulfate), forming inactive water-soluble
metabolites that are excreted by the kidney (~75%) in
addition to ~25% are execreted in feces.
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Some GCs are bioactivated after adminstration like
Prednisone that is converted in vivo to active metabolite
prednisolone.
Therapeutic Uses:
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Corticosteroids are first line therapy for solid organ
allografts & haematopoietic stem cell transplantation to
attenuating rejection episodes.
Autoimmune diseases as refractory rheumatoid arthritis,
systemic lupus erythematosus, temporal arthritis, and asthma.
Acute or chronic rejection of solid organ allografts.
Adverse Effects:
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The use of these agents is associated with numerous adverse
effects. For example,
◦ Hypercholesterolemia
◦ Hyperglycemia
◦ Hypertension
◦ Cataract
◦ Osteoporosis
◦ Increase liability to infection
◦ Adrenal suppression
III. Cytotoxic agents
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Alkylating agents
e.g. Cyclophosphamide
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Inhibitors of purine or pyrimidine synthesis
(Antimetabolites):
Azathioprine
Myclophenolate Mofetil
Leflunomide
Methotrexate
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Cyclophosphamide is a cytotoxic agent acts by alkaylation of
the DNA. Cyclophosphamide is a prodrug that is undergo some
modification by the effect of liver CYP450 to form the active
compounds, phosphoramide mustard and acrolein.
Reaction of the phosphoramide mustard with DNA is
considered to be the cytotoxic step especialy to those rapidly
deviding cells like neoplastic cells,proliferating lymphoid cells
and germ cells.
Pharmacokinetics:
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It is administered orally& intravenously
Cyclophosphamide is converted by mixed-function oxidase
enzymes (cytochrome P450 system; see chart) in the liver to
active metabolites.The main active metabolite is 4hydroxycyclophosphamide, and aldophosphamide. Most
of the aldophosphamide is oxidised by the enzyme aldehyde
dehydrogenase (ALDH) to make carboxyphosphamide. A
small proportion of aldophosphamide freely diffuses into
cells, it is decomposed into two compounds, phosphoramide
mustard and acrolein.
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The execretion occurs equally between renal and bilary
routs.
Therapeutic Uses:
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It is widely utilized in treatment of a wide variety of neoplastic
diseases (anticancer), such aslymphoma and breast cancer.
Immunosupressant in autoimmune disorders such as rheumatoid
arthritis ,
systemic lupus erythrematosus, Autoimmune
hemolytic anemia
Adverse effects:
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Alopecia and GIT disorders (Nausea -vomiting-diarrhea)
Bone marrow suppression
Hemorraghic cystitis , which can lead to fibrosis of the bladder.
The latter toxicity has been attributed to acrolein which is toxic
to the bladder epithelium. This can be prevented through the use
of aggressive hydration and/or MESNA (sodium 2mercaptoethane sulfonate), which neutralizes the toxic
metabolites, minimizes this problem.
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Sterility (testicular atrophy and aspermia in male& amenorrhea
in females)
Veno-occlusive disease of the liver
Antimetabolites
1- Azathioprine
It is a purine analogue immunosuppressive drug that was the
first agent to achieve widespread use in organ transplantation.
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It is a prodrug that is converted first to 6-mercaptopurine (6MP) and then to the corresponding nucleotide, thioinosinic
acid.
Mechanism of action:
The immunosuppressive effects of azathioprine are due to this
nucleotide analog.
Because of their rapid proliferation in the immune response,
lymphocytes (B &T) are predominantly affected by the
cytotoxic effects of azathioprine.
Azathioprine Inhibits de novo synthesis of purines required for
lymphocytes proliferation.
Pharmacokinetics:
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It is administered orally or intravenously.
Widely distributed but does not cross BBB.
Metabolized in the liver to 6-mercaptopurine or to thiouric
acid (inactive metabolite) by xanthine oxidase.
Excreted primarily in urine.
Therapeutic Uses:
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It is used to prevent organ rejection following organ
transplantation
To treat a vast array of autoimmune diseases, including
rheumatoid
arthritis,
Systemic
lupus
erythematosus
inflammatory bowel disease (such as Crohn's disease and
ulcerative Colitis), multiple scleross, autoimmune hepatitis,
atopic dermatitis, Myasthenia Gravis, Acute glomerulonephritis,
and others.
Adverse effects:
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Bone marrow suppression (leukopenia&thrombocytopenia).
Nausea , vomiting and diarrhea
Hepatotoxicity.
Increased risk of infections and mutagencity (Lymphoma)
Drug Interactions:
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Concomitant use with ACE inhibitors in renal transplant
patients can lead to an exaggerated leukopenic response.
Allopurinol, an inhibitor of xanthine oxidase that is used to treat
gout, significantly inhibits the metabolism of azatihioprine;
therefore, the dose of azathioprine must be reduced by 60 to 75
percent.
2- Mycophenolates
• Both Mycophenolate mofetil (MMF) and mycophenolate
sodium (MPS) are semisynthetic derivative of mycophenolic
acid from fungus source.
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Both are Prodrugs that are rapidly hydrolyzed in the
gastrointestinal tract to mycophenolic acid (MPA)
Mechanism of action:
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Inhibit de novo synthesis of purines (especially guanosine
nucleotides).
MPA is a potent inhibitor of inosine monophosphate
dehydrogenase (IMPDH), crucial for purine synthesis
deprivation of proliferating T and B cells of nucleic acids.
Pharmacokinetics:
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It is given orally, I.V or I.M. Dose 2-3 g/day.
Rapidly and completely absorbed after oral administration.
It undergoes first-pass metabolism to give the active moiety,
mycophenolic acid (MPA).
MPA is extensively bound to plasma protein.
metabolized in the liver by glucuronidation.
Excreted in urine as glucuronide conjugate
Therapeutic uses:
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Solid organ transplants (heart, kidney, and liver transplants).
Steroid-refractory hematopoietic stem cell transplant patients.
Combined with prednisone as alternative to CSA or tacrolimus.
Rheumatoid arthritis & dermatologic disorders.
Adverse effects & drug interaction:
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GIT toxicity: Nausea, Vomiting, diarrhea, abdominal pain.
Leukopenia, neutropenia & anemea
Higher risk of CMV infection.
It is CI to be administered during pregnancy
Concomitant administration with antacids containing Mg2+ or
Al 3+, or with cholestyramine, can decrease absorption of the
drug.
3- Leflunamide
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Leflunomide is a synthetic disease-modifying antirheumatic
group of drugs- antimetabolite immunosupressant (DMARD).
It acts by inhibiting dihydroorotate dehydrogenase (an enzyme
involved in de novo pyrimidine synthesis)
It is a prodrug ,following oral administration, leflunomide is
metabolized to teriflunomide, which is responsible for all of the
drug's activity in vivo.
Pharmacokinetics:
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The drug is given orally. It is rapidly metabolized to its
pharmacologically- active metabolite teriflunomide.
Teriflunomide is metabolized in the liver and excreted as well
renally and billary.
After oral administration, peak plasma levels of teriflunomide
occurred between 6 and 12 hours after dosing. Due to its very
long half-life (approximately 2 weeks), a loading dose of
100 mg for 3 days is required to reach steady-state levels
quickly.
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Therapeutic uses:
Leflunomide has both immunosuppressant and antiinflammatory effects. Leflunomide has been approved for the
treatment of rheumatoid arthritis or psoriatic arthritis. It
slows the progression of the disease and relief the
associated symptoms such as joint tenderness and decreased
joint and general mobility in human patients.
Adverse effects:
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Elevation of liver enzymes
Renal impairment
Teratogenicity (Women or men should not have babies
before 2 years after termination of therapy have elapsed or
undergo a rapid wash-out procedure like an eleven-day
scheme with oral cholestyramine or the use of activated
charcoal is indicated and will soon decrease plasma levels
below the critical limit of 0.02 mg/l ).
Cardiovascular effects (tachycardia).
Leflunomide
has
the
potential
to
myeloid/lymphatic malignancies or solid cancers
promote
Methotrexate (MTX) is synthetic antimetabolite used mainly in
treatment of cancer, and autoimmune diseases
It acts by inhibiting the metabolism of folic acid. It Inhibits
DHFR enzyme required for folic acid activation
(tetrahydrofolic) and as a result Inhibition of DNA, RNA
&protein synthesis occur.
Pharmacokinetics:
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It can be taken orally or administered by injection (I.M., I.V.,
S.C., or I.T.). Methotrexate is metabolized by intestinal bacteria
to the inactive metabolite 4-amino-4-deoxy-N-methylpteroic
acid (DAMPA), which accounts for less than 5% loss of the oral
dose
Oral doses are taken weekly. It is excreted in urine.
Therapeutic uses:
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Cancer Chemotherapy: In the treatment of a number of
cancers including: breast, head and neck, leukemia, lymphoma,
lung, osteosarcoma, and bladder.
Autoimmune disorders: It is used as a treatment for some
autoimmune diseases including: psoriasis and psoriatic arthritis,
Crohn's disease, and rheumatoid arthritis.
Pregnancy termination: Methotrexate is commonly used
(generally in combination with misoprostol) to terminate
pregnancies during the early stages (i.e., as an abortifacient). It
is also used to treat ectopic pregnancies.
Adverse effects & drug interaction:
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Nausea, vomiting,
stomatitis.
diarrhea,
Fatigue, fever, and dizziness
abdominal
pain,
ulcerative
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Alopecia
Bone marrow depression (low white blood cell count)
Predisposition to multiple infection
Pulmonary fibrosis
Renal & hepatic disorders
Methotrexate is a highly teratogenic drug and contrindicated
during pregnancy.
IV. Immunosuppressive antibodies
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The use of antibodies plays a central role in prolonging
allograft survival. Most of them block T cell surface molecules
involved in signaling immunoglobulins. They include:
- Antithymocyte globulins (ATG).
- Muromonab-CD3
- Rho (D) immunoglobulin.
- Basiliximab
- Daclizumab
- Infliximab
Preparation:
1. By immunization of either rabbits or horses with human
lymphoid cells producing a mixture of polyclonal antibodies
directed against a number of lymphocyte antigens (variable,
less specific).
2. Hybridoma technology: produce antigen-specific, monoclonal
antibody (homogenous, specific).
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Hybridomas are produced by fusing mouse antibodyproducing cells with human immortal, malignant plasma
cells. Hybrid cells are selected and cloned, and the antibody
specificity of the clones is determined. Clones of interest can be
cultured in large quantities to produce clinically useful amounts
of the desired antibody.
3. Recombinant DNA technology:
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Antibodies can be obtained by replace part of the mouse gene
sequence with human genetic material thus humanized antibody
produced (less antigenicity-longer half life).
The names of monoclonal antibodies conventionally contain
“Muro-” in their names are from a murine (mouse) source or
contain “zu” or “xi” if they are humanized .
1-Antithymocyte globulins (ATG)
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Thymocytes are cells that develop in the thymus and serve as
T-cell precursors.
The antibodies developed against them are prepared by
immunization of large rabbits or horses with human
lymphocytes (Polyclonal antibodies).
The antibodies bind to the surface of circulating T
lymphocytes, which then undergo various reactions, such as
antibody-dependent cytotoxicity, and apoptosis.
The antibody-bound cells are phagocytosed in the liver and
spleen, resulting in lymphopenia and impaired T-cell
responses & cell-mediated immunity.
Pharmacokinetics:
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The antibodies are slowly infused I.V.
Their half-life extends from 3 to 9 days.
Therapeutic uses:
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They are primarily employed, together with other
immunosuppressive agents (like cyclosporine), at the time of
transplantation to prevent early or acute allograft rejection, or
they may be used to treat severe rejection episodes .
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Corticosteroid-resistant
Acute allograf rejection.
Adverse effects:
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Hypersenstivity (chills and fever, skin rashes)
leukopenia and thrombocytopenia,
Tendency to infections especially CMV or other viruses.
2- Muromonab-CD3
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Muromonab-CD3 is a murine monoclonal antibody that is
synthesized by hybridoma technology and directed against cell
surface glycoprotein CD3 antigen of human T cells.
Binding to CD3 (antigen recognition site) leading to disruption
of T-lymphocyte function, and depletion of. circulating T cells
with decreased immune response.
Because muromonab-CD3 recognizes only one antigenic site,
the immunosuppression is less broad than that seen with the
polyclonal antibodies. T cells usually return to normal within 48
hours of discontinuation of therapy.
Pharmacokinetics:
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The antibody is administered I.V., initial binding of
muromonab-CD3 to the antigen transiently activates the T cell
and results in cytokine release (cytokine storm).
It is therefore usual to premedicate the patient with
Prednisolone, diphenhydramine , and acetaminophen to
alleviate the cytokine release syndrome.
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The antibody is metabolized and excreted in the bile.
Therapeutic uses:
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Muromonab-CD3 is used for treatment of acute rejection of
renal allografts
For treatment of corticosteroid-resistant allograft rejection in
cardiac and hepatic transplant patients.
It is also used to deplete T cells from donor bone marrow prior
to transplantation.
3- Rho (D) immune globulin
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Rho (D) is a concentrated solution of human IgG containing
higher titer of antibodies against Rho (D) antigen of red cells. In
a Rh negative mother Rho(D) Immune Globulin can prevent
temporary sensitization of the maternal immune system to Rh D
antigens, which can cause rhesus disease in the current or in
subsequent pregnancies.
Given to Rh-negative mother within 24-72 hours after delivery
or miscarriage of Rh-positive baby (2 ml, I.M.) to prevent
development of an immunological condition known as Rhesus
disease (or hemolytic disease of newborn; erythroblastosis
fetalis) of the next Rh positive babies.
Adverse Effects:
- Local pain
- Fever
4- Alemtuzumab
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A humanized monoclonal antibody directed against surface
protein (CD52) – expressed on lymphocytes, monocytes,
macrophages, natural killer cells and thymocytes
It exerts its effects by causing profound depletion of T cells
from the peripheral circulation as well as peripheral lymph
nodes.
it is being utilized in combination with low-dose CNIs or
sirolimus especially, in corticosteroid avoidance protocols in
renal and liver transplantation especially in HCV-infected
subjects.
Adverse effects: include Cytokine storm syndrome, requiring
premedication with acetaminophen, and diphenhydramine,
in addition to neutropenia, and anemia.
5- IL-2-receptor antagonists
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The antigenicity and short serum half-life of the murine
monoclonal antibody have been averted by replacing most of
the murine amino acid sequences with human ones by genetic
engineering.
Basiliximab is a chimeric human-mouse monoclonal IgG (25%
murine, 75% human protein).
Daclizumab is a humanized monoclonal IgG (90% human
protein).
They have less antigenicity & longer half lives than murine
antibodies
Mechanism of action:
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Both compounds are anti-CD25 antibodies and bind to CD25
(α-subunit chain of IL-2 receptor on activated lymphocytes)
They thus block IL-2 stimulated T cells proliferation and & Tcell response to any antigenic stimulus interfere with the
proliferation of these cells.
Basiliximab is more potent than daclizumab as a blocker of IL-2
stimulated T-cell replication.
Therapeutic uses:
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Both agents have been used for prophylaxis of acute rejection in
renal transplantation in combination with CsA and
corticosteroids.
They are not used for the treatment of ongoing rejection.
Pharmacokinetics:
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Both antibodies are given intravenously.
The serum half-life of daclizumab is about 20 days, Five doses
of daclizumab are usually administered (the first at 24 hours
before transplantation, and the next four doses at 14-day
intervals).
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The serum half-life of basiliximab is about 7 days. Usually, two
doses of this drug are administered (the first at 2 hours prior to
transplantation, and the second at 4 days after the surgery).
Adverse effects:
Both Daclizumab and Basiliximab are well tolerated. Their
major toxicity is GI upset, mild hypersensitivity symptoms with
minimal risk of opportunistic infections and post-transplant
lymphoproliferative disorder.
6- Anti TNF-α therapy
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TNF-α receptor antibodies approved for clinical use are
infliximab , certolizumab,and adalimumab chimeric humanmouse monoclonal IgGs that targets variable components of
TNF- α receptors (both soluble and cell-membraneIt bound)
and neutralize them and inhibits further activity.
Etanercept is a humanized fusion protein linking mimics
inhibitory effects of naturally occurring soluble TNF receptors.
Mainly used in treatment of autoimmune disorders.
Adverse effects:
- Infusion reaction – fever, urticaria, hypotension, dyspnoea
- Opportunistic infections – TB, RTI, UTI
V- Interferones
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Interferons are a family of naturally occurring, inducible
glycoproteins cytokines that are used clincally in many
purposes. They have different immunomodulating actions.
The interferons are synthesized by recombinant DNA
technology.
Three types of interferon exist, α , β, and γ.
IFN- γ : Acts as immunostimulant. It increases expression of
MHC molecules, enhances the activity of macrophages and
natural killer cell, and stimulates production of IgG.
IFN- α, β : Act as inhibitors of cellular proliferation (cancer
cells, Immune cells and viral infections)
Therapeutic uses:
- Treatment of certain infections e.g. Hepatitis B&C (IFN- α ).
- Certain forms of cancer e.g. melanoma, renal cell carcinoma
(IFN- α ).
- Autoimmune diseases e.g. Rheumatoid arthritis (IFN- α & β ).
- Multiple sclerosis (IFN- β): reduced rate of exacerbation.
Adverse effects:
Fever, chills, myelosuppression.
Immunosstimulants
 Immunosstimulants are substances that stimulate the immune system by
inducing activation or enhancing the activity of any of its components.
 Immunosstimulant agents are now utilized to enhancing cellular and/or
humoral immunity
 should benefit people with immune deficiencies (primary and secondary)
and severe infections and cancers.
 Degree of stimulation relatively small
Types of immunostimulant agents:
 1- Synthetic drugs:
e.g. Levamisole and Thalidomide
 2- Immunostimulant vaccines:
e.g. BCG vaccine
 3- Recombinant cytokines :
e.g. IFN-,GM-CSF, IL-2
 4- Immunization vaccines (active and passive)
 5-Immunostimulatory MAbs
I-Immunostimulant drugs
1- Levamisole
 Levamisole (LMS) is an imidazothiazole derivative that has an
immunomostimulator and anthelminthic activities .It is usually used
as phoshates or hydrochloride salts.
 It has been used in humans to treat many parasitic worm infections,
In addition to its utilization as immunostimulant in combination with
some chemotherapeutic agents (like 5-FU) to treat many types of
human cancers like colon cancer, melanoma, and head and neck
cancer.
 Levamisole’s mechanism of action for its immunostimulating effects
are not well understood. It is believed it enhances cell-mediated
immune function in peripheral T- and B-lymphocytes and stimulates
phagocytosis by monocytes. Its immune stimulating effects appear to
be more pronounced in the immune-compromised individuals.
 Levamisole may also interferes with the growth of cancer cells and
slows their growth and spread in the body by blocking carbohydrate
metabolism.
 Side effects include GI upset, loss of appetite, change in taste and
smell, muscle aches, fatigue, dizziness, headache and skin rash.
 Alcohol and alcohol containing products should be avoided while
taking levamisole. Flushing, nausea, vomiting, stomach pain
headache, swelling, and rashes can occur.
2-Thalidomide
 Thalidomide was first introduced as a sedative and antiemetic drug
during the period of world war II, it was withdrawn due to sever side
effects “teratogenicity and neuropathy”.
 Now there are revived interests in using thalidomide as
immunostimulating agent used to treat a number of medical
conditions like cancer (e.g. multiple myeloma) and tough infectious
diseases like leprosy.
 Thalidomide has many mechanisms by which it exerts the
immunostimulatory effect:
- It stimulates T-cells proliferation
- It enhances activation of NK cells
- It stimulate production of IL-2& IFN-γ and inhibits the
production of other cytokines (e.g. IL-10 ).
- Thalidomide has antiangiogenic effect (inhibits the growth of
new blood vessels), which makes it be useful in treating some
types of cancer like multiple myloma, prostate cancer and
lymphomas.
 Thalidomide is contraindicated in women within childbearing
potential due to the high risk of teratogenicity.
II-Bacterial-derived Immunostimulant Vaccines
Bacillus Calmette-Guérin (BCG) vaccine
 BCG is a vaccine prepared from life-attenuated bovine tuberculosis
bacillus, Mycobacterium bovis, that has lost its virulence in humans,
but still retained its strong antigenicity enough to stimulate immune
system to produce the corresponding antibodies.
 BCG is used predominantly as upperarm I.D. injection for vaccination
against tuberculosis.
 BCG is also used as intravesical therapy in the treatment of superficial
forms of bladder cancer and colorectal cancer. The mechanism is
unclear, it appears a local immune reaction is mounted against the
tumor (may act in part by stimulating TNF-α release from
macrophages).
 A number of cancer vaccines in development use BCG as an adjuvant
to provide an initial stimulation of the patients' immune system.
 The most noticeable adverse effects associated with BCG are causes
some pain and scarring at the site of injection, hypersensitivity, chills,
fever, skin rashes, hypotension and may be shocking.
III- Cytokines
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Human cytokines prepared by recombinant DNA technology
1- human recombinant IL-2 (rhIL-2 ); aldesleukin, proleukin
 It binds to the IL-2 receptor on T-lymphocytes
 It stimulates the proliferation and diffrentiation of antigen-primed
(helper) T cells, which subsequently produce more cytokines( IL-2,IL1, IFNɣ, and TNFα).
 These cytokines collectively activate natural killer cells, macrophages,
and cytotoxic T lymphocytes.
 rhIL-2 is used in metastatic renal cell cancer and melanoma.
Adverse effects:
 Inflammation and increased vascular permeability, peripheral edema,
fever and hypotension.
 Cardiac arrhythmia, anemia, nausea, vomiting, diarrhea, confusion
2- Interferone (INF-ɣ)
 INF-ɣ boosts the activity of macrophages and NK cells.
 It stimulates the expression of MHC molecules and production of IgG.
 It causes cancer cells to produce more antigens , suppresses the
growth of cancer cells and inhibits angiogenesis
 It is approved for use with some leukemias, lymphoma, renal cancer
and melanoma in addition to prevention of secondary infections in
chronic granulomatous diseases.
Adverse effects:
 Flu-like symptoms – fever, chills, headache, GI disturbance
 Hypotension, Arrhythmia
 CNS- depression and confusion
3-Granulocyte-macrophage colony-stimulating
factor (GM-CSF)
 GM-CSF is a cytokine secreted mainly by macrophages, mast cell in
addition to endothelial cells, and fibroblasts. It functions as a white blood
cell growth factor.
 rhGM-CSF interacts with specific cell-surface receptors found on various
immune component cells. GM-CSF stimulates stem cells to produce
granulocytes (neutrophils, eosinophils, and basophils) and monocytes. It
also activates the phagocytic activity of mature monocytes and prolongs
their survival in the circulation.
 GM-CSF is used in cancer patients after chemotherapy to treat
neutropenia and increased risk of serious infection receiving cancer
chemotherapy
 It is also used to used to accelerate myeloid recovery after autologous
BMT in patients with lymphoma, and acute lymphoblastic leukemia
Adverse effects:
 include fever, malaise, arthralgias, myalgias, and a capillary leak
syndrome characterized by peripheral edema and pleural or pericardial
effusions. Allergic reactions may occur but are infrequent.
Spleenomegaly is a rare but serious complication of the use of GM-CSF.
IV- Immunization vaccines
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Vaccines are biological preparations that improves immunity. It could
act against particular disease or boost the general immune function.
Active immunization (vaccination): include administration of the
antigen of the disease-causing microorganism in the form of
weakened or killed microbe , its toxins or a specific protein or peptide
constituent of an organism that stimulate the immune system to
recognize these antigens and generate an adaptive immune response
by raising the specific antibodies to destroy it, and "remember" it, so
that the immune system can more easily recognize and destroy any of
these microorganisms that it later encounters. the response takes
days/weeks to develop but may be long lasting even lifelong.
Vaccines can be prophylactic to prevent or ameliorate the effects of a
future infection by pathogen (e.g. polio vaccine, MMR vaccine)., or
therapeutic (e.g. vaccines against cancer)
Passive immunization: fortification of the immune system by
administration of prepared imunglobulines antibodies to protect
against infection; it gives immediate, but short-lived protection for
several weeks to 3 or 4 months at most. It is mainly used as
replacement therapy in individuals with primary immune deficiency
diseases . Also, to manage some acute infections when active
vaccination is inadequate
Passive immunity is usually classified as natural or acquired. The
transfer of maternal tetanus antibody (mainly IgG) across the placenta
provides natural passive immunity for the newborn baby for several
weeks/months until such antibody is degraded and lost. In contrast,
acquired passive immunity refers tothe process of obtaining serum
from immune individuals, pooling this, concentrating the
immunoglobulin fraction and then injecting it to protect a susceptible
person.
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Examples: vaccines of hepatitis B, botulism, diptheria, tetanus, rabies
V- Immunostimulatory MAbs
 Monoclonal antibodies prepared against surface antigenic marker
proteins specific for tumor cells (e.g. anti-HER2/Neu, anti-VEGF)
 mAbs act directely when binding to a cancer specific antigens and
induce immunological response to cancer cells. Such as inducing
cancer cell apoptosis, inhibiting growth, or interfering with a key
function.
 mAbs also was modified to deliver a toxin, radioisotope, cytokine or
other active conjugates into cancer cells.