Immunomodulation Therapy Flashcards
What are the main uses of immunosuppressive drugs?
- Transplant rejection
- Graft VS Host Response
- Autoimmunity
Hyperacute Rejection
Occurs within minutes of transplant
Caused by pre‐existing reactive antibodies - avoided via crossmatching before the operation
Acute Rejection
6‐12 months post transplant
T cell‐mediated
Chronic Rejection
Months to years
Due to fibrosis causing damage to the graft blood vessels
What type of rejection is immunosuppression aimed towards preventing?
Immunosuppressive therapy aimed at preventing acute rejection and prolonging graft survival
What is the use of multi-tiered drugs in immunosuppression?
It allows for the targeting of multiple aspects of the immune system as well as allowing for lower doses
What are some examples of the adrenocortical steroids (glucocorticoids)?
- Prednisone (prodrug)
- Prednisolone
What are the effects of prednisone/prednisolone?
• non‐specific inhibitor of the immune system and/or immune system genes (e.g. cytokines)
• inhibits expression of critical pro‐inflammatory CH3
• decreases the numbers of circulating leukocytes
MOA of Prednisone/Prednisolone
- Glucocorticoids diffuse into cells and bind their receptors in the cytoplasm
- Promote receptor dimerization & nuclear translocation
- Active receptors bind to target genes and influence their expression - either increase or decrease
- Inhibition of critical immunoregulatory genes inhibits the immune response
Indications of Prednisone/Prednisolone
• Commonly used in combination with other agents in standard immunosuppressive therapy regimens to prevent organ graft rejection
• High dose IV pulses of steroids additionally used to combat:
‐ Acute rejection episodes
‐ GvHD in BMT
‐ Treatment of Cytokine‐Release Syndrome (cytokine storm)
• Autoimmune and Inflammatory Diseases: rheumatoid arthritis, lupus, multiple sclerosis, psoriasis, inflammatory bowel disease, skin diseases, eye diseases, asthma
Prednisone/Prednisolone SE
‐ Hyperglycemia, Hypertension, Hyperlipidemia, Obesity
‐ Increased risk of exacerbating pre‐existing diabetes and/or developing diabetes
‐ Osteopenia
‐ Cataracts
‐ Growth retardation in children
‐ Poor wound healing
What is typically done with glucocorticoids in order to minimize SE?
The doses are slowly tapered over the first month - do NOT abruptly withdraw though due to possibility of acute adrenal crisis
What are the drugs of the proliferation inhibitors/anti-metabolites?
- Azathioprine (prodrug of 6-mercaptopurine)
* Mycophenolate mofetil
Why is azathioprine used of 6-mercaptopurine?
It has a high oral bioavailability and it will then be converted to 6-mercaptopurine
MOA of Azathioprine
It is converted to 6-mercaptopurine and then 6-TIMP which inhibits de novo purine synthesis.
A further metabolite, 6-TGTP inhibits CD28/Rac1 T cell costrimulation as well as the induction of apoptosis via DNA damage.
All of this prevents lymphocyte proliferation.
Indications of Azathioprine
- Prophylactic prevention of graft rejection following organ transplantation
- Autoimmune diseases and other immune‐mediated diseases
• Rheumatoid arthritis
• Crohn’s
• Multiple sclerosis
Azathioprine SE
a) Diarrhea, nausea & vomiting
b) Leukopenia & thrombocytopenia
c) Hepatotoxicity
d) Increased risk of infections
e) Increased risk of malignancy
What are the drug interactions of azathioprine?
Allopurinol and Febuxostat - xanthine oxidase inhibitors will lead to the build-up of 6-mercaptopurine which can be toxic.
Xanthine oxidase normally also metabolized 6-mercaptopurine
What is mycophenolate mofetil a prodrug of?
Mycophenolic Acid
MOA of Mycophenolate Mofetil
Mycophenolic acid (MPA) is a non‐competitive, reversible inhibitor of inosine monophosphate dehydrogenase (IMPDH) type II ‐ the rate‐limiting enzyme in the de novo synthesis of purine nucleotides
Indications of Mycophenolate Mofetil
- To prevent graft rejection following organ transplantation
- Some autoimmune diseases and immune‐mediated disorders
Mycophenolate Mofetil SE
a) Diarrhea, nausea & vomiting
b) Leukopenia & anemia
c) Embryo/fetal toxicity‐ risk of first trimester loss and congenital abnormalities d) Increased risk of infections – bacteria, viruses (esp. CMV), fungi & parasites
e) Increased risk of malignancies (lymphoma/skin)
f) Progressive multifocal leukoencephalopathy (RARE, but potentially fatal)
Contraindications of Mycophenolate Mofetil
Pregnancy, women of child bearing age who wish to become pregnant, and men who wish to become fathers – due to the teratogenicity ‐ azathioprine is preferred in these patients
Why are lymphocytes specifically affected by mycophenolate mofetil?
Lymphocytes are more dependent on de novo purine biosynthesis than are other cell types because there is no Salvage pathway - IMPDH II is also selectively expressed in lymphocytes
Methotrexate MOA
Inhibition of dihydrofolate reductase indirectly inhibits purine/pyrimidine synthesis
Methotrexate Indications
Autoimmune diseases (especially Rheumatoid arthritis)
Methotrexate SE
Renal, hepatic & GI toxicity, lung damage, BM suppression, neurotoxicity, increased risk of malignancy, teratogenic
Methotrexate Contraindications
Pregnancy
Cyclophosphamide MOA
Nitrogen mustard alkylating agent crosslinks DNA, RNA and proteins