Immunosuppressive Drugs Flashcards
What is the function of immunosuppressive drugs?
Used to dampen the immune response in organ transplantation and autoimmune disease
What are the major classes of immunosuppressive drugs?
Calcineurin inhibitors
Antiproliferative/antimetabolic agents
Biological (antibodies)
Glucocorticoids
What is the primary objective of immunosuppressive treatment?
Prevent the acute rejection of organ transplant
What is the secondary objective of treatment?
Install a tolerance for the transplanted organ
How are the objectives of the immunosuppressive treatment obtained?
- Down-regulation of the immune system activity to achieve a therapeutic objective
- Achieve immunological tolerance: re-educating the body not to reject
What are the steps when administering immunosuppressive treatment?
- Intensive induction and lower-dose maintenance drug protocols
- Greater immunosuppression is required to gain early engraftment
- Early high-risk acute rejection is replaced over time by the increased risk of medications’ side effects
- Reach a slow reduction of maintenance immunosuppressive drugs
How is early engraftment achieved?
Treat established rejection rather than maintain long-term immunosuppression
What are examples of Calcineurin inhibitors?
Cyclosporins
Tacrolimus
What are examples of mTOR inhibitors?
Sirolimus
Tacrolimus
Everolimus
What are examples of anti-metabolites?
Azathioprine
Mycophenolate
Mofetil
What are examples of steroids?
Prednisolone
Methylprednisolone
What are examples of monoclonal antibodies?
Basiliximab
Alemtuzumab
Rituximab
Adalimumab
What is the the normal pathway of calcineurin?
- TCR Activation
- Phospholipase C Activation –> Ca2+ release
- Ca2+ & Calcineurin
- Calcineurin + Immunophilin
- Dephosphorylation of nuclear factor of activated T - cells (NFAT)
- NFAT Translocation
- Upregulation of cytokine genes –> Cytokine
At which point of the normal calcineurin pathway do calcineurin inhibitors act?
Step 3: When calcineurin acts alongside calcium
What are the PK of calcineurin inhibitors? (4)
- Narrow therapeutic index
- Orally bioavailable
- Highly protein bound
- Metabolized by CYP3A4
What is the drug interactions of calcineurin inhibitors like?
Potential for drug interactions with Sirolimus, an mTOR inhibitor
What is the precaution taken with calcineurin inhibitors because of their low therapeutic index?
Therapuetic drug monitoring
What is cyclosporine absorption influenced by?
P-glycoprotein (permeability glycoprotein - pump/variability among individuals ABCB1)
What percentage of calcineurin inhibitors is protein-bound?
90%
What is the alternative name for Sirolimus?
Rapamycin
What is Sirolimus?
A macrolide identified in a bacterial strain of STreptomyces that produces a potent antifungal metabolite
What are the medical purposes of mTOR inhibitors?
Approved in renal transplantations in combination with other agents
Also used in drug-eluting stents in coronary artery intervention
How does Rapamycin help with stents?
Deferred release of antiproliferative drugs such as Rapamycin controls the rapid and undesired cell growth process in the stent
What are the PK of mTOR inhinbitors? (3)
- Highly protein bound
- Adminisered as tablets
- Metabolised by CYP3A4, also a substrate for P-glycoprotein
What % of mTOR inhibitor drugs is protein-bound?
92%
What happens when Rapamycin binds to FKBP12?
Catalyzes peptidyl-prolyl cis/trans isomerization and functions as molecular chaperone
What is FKBP12?
A target for Rapamycin
What is Everolimus?
A derivative of Sirolimus
What is Tacrolimus?
FKB506, which binds to FKBP12
What is the MOA of mTOR inhibitors?
Binding of FK binding protein FKBP12 and inhibiting T-cell proliferation and progression from G1 to S phase of the cell cycle
What are the adverse effects of mTOR inhibitors?
Hyperlipidemia
Risk of kidney failure with combination therapy with Cyclosporine
What is Azathioprine (AZA)?
A prodrug converted into 6-Mercaptopurine, which is an immunosuppressive medication
How does AZA work?
Works by interfering with DNA synthesis
What is the effect of AZA?
Reduces inflammation
Where is AZA converted into 6-Mercaptopurine?
Gut/ liver
When is AZA used?
Used in moderate to severe cases of immune reaction
Also used in patients with severe IBD or those who are steroid-resistant or steroid-dependent
What is the MOA of AZA?
- Impair purine biosynthesis
- Inhibition of DNA replication and RNA transcription
- Limit lymphocytes’ proliferation and increase apoptosis
- Inhibit inflammation (TNFa & INFγ)
What is the half-life of 6-Mercaptopurine like?
Short: 1 to 2 hours
What are the drug interactions of 6-Mercaprtopurine?
Increased toxicity when combined with Alluprinol
What is Alluprinol?
A Xanthine oxidase inhibitor
What does the metabolism of 6-Mercatopurine depend on?
Differences in TPMT activities
What are the side effects of 6-Mercaptopurine?
Pancreatitis
Major dose-related adverse effect is bone marrow suppression
Vomiting and nausea
Fever, rash, and arthralgia (less common)
Hepatitis (rare)
What is MMF?
Mycophenolate Mofetil, an anti-metabolite
What is MMf hydrolyzed into?
Mycophenolic acid
What is the medical use of MMF?
Prevention of graft rejection in solid organ transplants
What are the PK of MMF?
- Better efficacy and safety profile than AZA
- Excellent bioavailabilty
- Metabolised via entero-hepatic circulation
What is the MOA/target of MMF?
It is a non-competitive inhibitor of Inosine monophosphate dehydrogenase (IMDPH)
The effects are more pronounced in rapidly dividing cells
Affects the DNA synthesis
What are the PK of glucocorticoids?
Good absorption/ excellent bioavailability
Oral or IV
What are examples of glucocorticoids?
Methylprednisolone
Hydrocortisone
When are GC treatments recommended? Why?
Addition to organ perfusate solution and pretreatment of transplant donors, to help reduce ischemia-reperfusion injury peri-transplant
What is the purpose of GC?
To reduce side effects or induce immune tolerance instead of immunosuppression
Which kind of GC is used in combination with dexamethasone with inducers of immune-regulatory cells?
GCs with low bioavailability and high potency for GC receptors, like Budesonide
What is the MOA of steroids?
- The steroid present in the blood bound to CBG, binds in free form
- The main receptor is an intracellular steroid receptor that is associated with heat shock protein HSP90
- Receptor complex H - receptor is formed, HSP90 is release
- H/R enters the nucleus as a dimer, binds GC response elements on the gene and regulates transcription factor
- Protein expression/modulation decreases
What are antithymocyte globulins (ATG)?
Antibody preparation derived from rabbits or horses hyperimmunized with human thymocytes (non-specific/anti-CD3) –> polyclonal
What is an example of anti-CD3-OKT3?
Muromonab
Which was the first ever monoclonal antibody approved for human use?
Muromonab
What is Adalimumab?
Anti-TNFa
What are examples of Anti-CD25?
Basilixumab/Daclizumab
What is Alemtuzumab?
Anti-CD52
What is Fingolimod?
Sphingosine 1 Phosphate-receptor modulator
What is Basiliximab?
A chimeric murine/ human monoclonal antibody
What is Daclizumab?
A chimeric humanized monoclonal antibody
What is the target of both Basiliximab and Daclizumab?
The alpha chain of IL2 receptor –> CD25
What is the MOA of BAsilixumb and Daclizumab?
High-affinity for IL2 receptor, CD25, which is a receptor expressed on the surface of the activated T lymphocytes
Works in response to antigenic stimulation only when lymphocytes are activated
What is Alemtuzumab?
A humanised antibody and CD52
How does Alemtuzumab work?
Upon T cell activation, CD52 is cleaved and released.
It is activated by other T-cells by binding a special receptor, the Siglec10.
This is an amplification of the immune response; Alemtuzumab blocks CD52
What is the main medical purpose of Alemtuzumab?
Multiple sclerosis
Which drugs are nephrotoxic? (12)
- Calcineurin inhibitors
- NSAIDs
- Antibiotics and anti-fungi
- Chemotherapy
- ACE-inhibitors/ARBs/Renin inhibitors
- Orlistat
- Statins
- Mesalamine
- Herbal remedies
- Radiocontrast
- Heavy metals
- Aminoglycosides
How can drugs be nephrotoxic? (7)
- Direct drug nephrotoxicity
- Drug-Uromodulin interaction –> cast formation
- Intracellular drug accumulation
- Increased drug concentration within cells –> transporter competition
- Insoluble drug in urine –> crystal formation
- Immune drug effects (haptens, molecular mimicry, antibody formation, increased T-cell activity)
- Combination of nephrotoxic drugs
What is the effect of chronic rapamycin use, as found in animals?
Found to cause hyperlipidemia, reduce fat mass, promote glucose intolerance, and diabetes-like syndrome
How does chronic rapamycin use causes hyperlipidemia?
Coordinately downregulates genes required for lipid uptake and storage in adipose tissue (ATGL, MGL, DAGL)
What is the effect of endogenous/ exogenous FKBP38 ligand on mTOR?
Blocks mTOR and decreases lipogenesis, and rapamycin interferes by binding FKBP38