Transcript Document

History of
immunosuppressants
Dr.
1st successful kidney transplant
Dec 23, 1954
– Peter Bent Brigham
Hospital, Boston MA
– Dr. Joseph Murray
23 yr old identical twin
brothers
– No immunosuppression
used
– d. 1962 due to disease
recurrence
(glomerulonephritis)
N Engl J Med 2004;351:2761-6
History of immunosuppression in
transplantation
Goals of immunosuppression (IMS)
To prevent allograft rejection
To prolong allograft functional life
To optimise allograft function
Prolong patient survival
Improve patient quality of life
To minimize toxicity of IMS agents
– immunodeficiency complications
– non-immune toxicities
Transplantation and the immune
system
Recognition of allograft as non-self
Donor and recipient antigen presenting
cells
(APC’s = dendritic cells, macrophages)
– Present donor antigen to host T-lymphocyte
Key event:= T-lymphocyte activation
Immunosuppression:
3 ways to achieve
Depletion of lymphocytes
– Polyclonal antibodies (horse, rabbit anti-thymocyte
globulin)
– Mouse monoclonal anti-CD3 antibody (OKT3)
– Humanized monoclonal anti-CD52 (alemtuzumab)
– B-lymphocyte monoclonal anti-CD20 (rituximab)
Diversion of lymphocyte traffic
Blocking of lymphocyte response
NEJM 2004;351:2715-29.
Calcineurin inhibitors Anti-IL2 receptor Antibodies
Corticosteroids
Antigen
presenting
cell
Basiliximab
Daclizumab
Ciclosporin
Tacrolimus
Helper
T
Lymphocyte
A
C
T
I
V
A
T
I
O
N
Activated
T
Lymphocyte
IL-2
IL-2
ILIL-2 R (High affinity)
Antigen /T-cell
receptor/ MHC II
Everolimus
Sirolimus
P
R
O
L
I
F
E
R
A
T
I
O
N
T
Lymphocyte
DNA
synthesis
T
Lymphocyte
Mycophenolic acid
Azathioprine
Immune system:
3 signal model of T-cell activation
Signal 1: Antigen-specific signal
Donor antigen is presented on APC
(antigen presenting cell)
T-cell recognized antigen as “non-self”
Complex formed between MHC-AntigenTcell receptor (TCR)
Immune signal is transduced through CD3
complex
N Engl J Med 2004;351:2715-29.
Signal 2: Non-antigen-specific
co-stimulatory signal
Binding of co-receptors between APC and
T-cell
– CD80/86 (aka B7) on APC with CD28 on Tcell
“reinforces” and strengthens immune
signal transduced through CD3 complex
Combined action of signals 1 & 2 activate
important intracellular pathways
N Engl J Med 2004;351:2715-29.
Combined action of signals 1 & 2 activate
important intracellular pathways
– Calcium-calcineurin pathway
– RAS-MAP kinase pathway
– Nulcear factor-κB pathway
Leads to
– production of IL-2 and other growth promoting
cytokines
– Expression of IL-2 receptor (CD25)
N Engl J Med 2004;351:2715-29.
Signal 3: Mammalian target of
rapamycin (mTOR) activation
IL-2 produced binds to newly activated IL2 receptor (CD25)
Binding activates mTOR
mTOR activation triggers cell cycle
– Lymphocyte proliferation
– Results in large numbers of effector T-cells
N Engl J Med 2004;351:2715-29.
Result of effector T-cells
Effector T-cells targeted at donor antigen
infiltrate graft
– Interstitial and/or perivascular infiltration
– Cascade of activation of macrophages, Bcells, plasma cells
– Resultant cell lysis
– Severe – edema, hemorrhage, vasculitis
Three Signal Model of T cell Activation
[adapted from Sing-Leung 2001]
Antigen Presenting Cell
Signal 1
Signal 2
MHC II
B7
Antigen
CD45
CD4
CD3
Signal 3
Interleukin-2
CD28
Interleukin-2 receptor
TCR
Calcineurin
Pathway
TOR
Pathway
Cytokine gene
nucleus
T Lymphocyte
Purine
Cell Cycle
Synthesis
Target lymphocyte
Sites of Action of Immunosuppressive Medications
[adapted from Sing-Leung 2001]
Antigen Presenting Cell
Steroids
Signal 1
MHC II
OKT3
ATG
CD45
Signal 2
CD4
Calcineurin
Pathway
Steroids
B7
Belatacept
CD3
TCR
Signal 3
CD28
Cyclosporine
& Tacrolimus
Anti-IL-2R
Interleukin-2
Interleukin-2 receptor
TOR
Pathway
Cytokine gene
Cell Cycle
nucleus
T Lymphocyte
Sirolimus
MMF
Purine
Synthesis
Target lymphocyte
Individual Immunosuppressive Drugs and Sites of
Action in the Three-Signal Model
N Engl J Med 2004;351:2715-2729
Target Antigens
Immunosuppressant drugs
Anti-metabolites
Calcineurin inhibitors
– Ciclosporin A
– Tacrolimus
– Azathioprine
– Mycophenolates
– Leflunomide?
m-TOR inhibitors
– Sirolimus
– Everolimus
Newer antibody drugs
Alemtuzumab
Rituximab
IL-2 receptor ‘mabs’
– Basiliximab
– Daclizumab
CNI’s:
Tacrolimus and Cyclosporine
Major breakthrough in modern
transplantation
Lead to significant improvements in
outcome
“Backbone” of most IMS protocols
Similar mechanisms of action
– Differ in structure and receptor interactions
Transplant Proc 2004;36:25S-32S. Am J Kidney Dis 2006;47:S3-21.
Calcineurin inhibitors (CNIs) :
Mechanism of action
Forms complex with cytosolic proteins (aka
immunophilins)
– CSA = cyclophilin
– Tacrolimus = FKBP-12 (FK-binding protein)
↑ affinity and binding of immunophilin-drug
complex to calcineurin
Inhibits of transcription of IL-2, other cytokines
↓ T-cell activation & proliferation
Transplant Proc 2004;36:25S-32S. Circulation 2004;110:3858-65.
Calcineurin inhibitors (CNIs)
Ciclosporin A (CyA) binds to intracellular
protein, cyclophilin
only active once bound
Tacrolimus (FK506) binds to intracellular
protein, FKBP-12
only active once bound
The fungus Tolypocladium
inflatum
Fungal source of CyA
Hydrophobic cyclic
endecapeptide
Scanning electron micrograph
of Streptomyces tsukubaensis
Bacterial source of
tacrolimus
Sirolimus from
Streptomyces
hygroscopicus & very
similar structure
Basic mode of action
(Drug + immunophilin) inhibits calcineurin
– Prevents dephosphorylation (activation) of NF-Act Tcell
– factors which stimulate cytokine (i.e. IL-2/IFN-) gene
transcription
– Net result: impaired IL-2 production
‘reversible inhibition of T-cell activation,
proliferation & clonal expansion’
– Stops cell cycle at G0-G1 stage
Ciclosporin A & tacrolimus share a
mechanism of action and metabolic route
Never given together (additive
nephrotoxicity)
Tac interacting with CyA?
12-24hr gap only if converting
Differences include ADR’s & efficacy
Ciclosporin
Oral absorption
– Large inter & intra-patient variability
– Food & juices
– IV dose & administration
Distribution – extensive (not dialysed)
Metabolism
– CYP450 3A4 with adult half-life 5-18 hours
Shorter in children
Steady state 2-3 days after change of dose
Tacrolimus
Absorption
– Fatty food decreases rate & extent
>80% distributes into erythrocytes
– Whole blood trough levels
– Remainder 99% protein bound
CYP450 3A4 metabolism
– Adult half-life approx 9-12 hours
Clearance faster in <6yrs
Metabolic interactions on CNI & m-TOR inhibitor levels
Interacting drug
Effect on blood level
Erythromycin & clarithromycin
Increased
Diltiazem, nicardipine, verapamil
Increased
Fluconazole, itraconazole, ketoconazole,
voriconazole
Increased
Rifampicin
Decreased
Carbamazepine
Decreased
Phenobarbital
Decreased
Phenytoin
Decreased
St John’s Wort
Decreased
Typical CNI doses target levels
Calcineurin
inhibitor
Common
initial oral
doses
Ciclosporin
5mg/Kg bd
Tacrolimus
0.15mg/Kg
bd
Once daily?
Typical target blood
levels
0-6 months Greater 6
months
150 to
75 to
300ng/mL 150ng/mL
10 to
5 to
15ng/mL
10ng/mL
Anti-metabolites
Only purine anti-metabolites routinely used
1) Azathioprine
2) Two mycophenolate presentations
– mofetil
– sodium EC
Azathioprine
Guanine anti-metabolite
– rapidly converted  6-mercaptopurine
 thioguanine nucleotides
– Disrupts synthesis of developing cellular DNA
& RNA strands & so prevent mitosis
‘Prevents early stages of activated T & Bcell proliferation’
One metabolic route involves thiopurine
methyltransferase (TPMT).
– Absent in 1 in 300
Toxicity
Final metabolism to inactive 6-thiouric acid
– Via xanthine oxidase
Quarter dose in combination with allopurinol
Usual starting dose 1-2mg/Kg
– Can use 50% dose if giving iv
Maintenance immunosuppression over first year after transplantation (1994-2003).
(2005 OPTN/SRTR Annual report)
Mycophenolic acid precursors
Isolated in 1896 from Penicillium spp.
mofetil ester rapidly cleaved  active
mycophenolic acid (MPA)
1 enzyme is rate limiting step in lymphocyte de
novo purine biosynthesis
– Inosine Mono-Phosphate DeHydrogenase
Mycophenolic acid non-competitively inhibits
IMPDH
– Prevents production of Guanosine triphosphate (GTP)
– Impairs production of DNA limiting lymphocyte
proliferation
T & B-lymphocytes preferentially use this
pathway for purine production.
– Other cell lines have salvage pathways.
Molar equivalent doses:
– 1gram MMF = 720mg MPS EC
Paed MMF dose with ciclosporin 600mg/M2 bd
MMF dose with tacrolimus = less (50-25%)
– MPA glucuronide undergoes entero-hepatic recirculation
– Second peak maintains levels
– ciclosporin inhibits this recirculation
MMF injection available if necessary
– Same dose iv as oral
– Requires aseptic manipulation
Interactions
Magnesium & aluminium (antacids)
– Reduced absorption
Cholestyramine
– Reduced entero-hepatic recirculation
(Val) aciclovir
– Competes for tubular secretion with MPAG
– Modest effect
+12% MPAG AUC & +20% aciclovir AUC
Pros & cons of mycophenolate
Reduced incidence of ACR c.f. placebo or
azathioprine with Sandimmune & steroid
Lower incidence CAN c.f. azathioprine
– Reduced interstitial fibrosis?
Much more expensive than azathioprine
Higher incidence of GI ADR - strategies
diarrhoea 12.7 – 31.5%
abdominal pain 11.5 – 26%
nausea 4.2 – 14% and vomiting 2.4 – 12%.
Higher incidence of anaemia (15%)
Sirolimus
Another macrocyclic antibiotic
– Immunophilin binder (like CyA & FK506)
also bind ubiquitous protein, FKBP-12
Does not inhibit cytokine (i.e. IL-2) gene transcription
Complex inhibits m-TOR
– Inhibits multiple biological steps
e.g. activation of p70S6 kinase
– Prevents IL-2-mediated signal transduction to cell
nucleus
Cell cycle arrest at G1-S phase
Also inhibits tumour cell & smooth muscle cell
proliferation (CAN)
Absorption is poor
– Food also affects rate & extent
Consistency
Widely distributed into tissues
CYP450 3A4 & P-glycoprotein metabolism
– Adult half-life long (57-63 hours)
Clearance slightly higher in <11yrs cf 12-18yrs
Levels 4-12ng/mL, no more frequently
than every fortnight.
Adverse effect profile dissimilar to CNIs
– Not nephrotoxic
– Wound healing delay & fascial dehiscence
lymphocele formation
–
–
–
–
–
–
–
Mouth ulceration – transient? Topical steroid
Acne and pilosebaceous rash - doxycycline
Peripheral & angioedema >10% - withdrawal
Dose related mixed hyperlipidaema - statins
Anaemia & thrombocytopaenia
Arthralgias – dose reduction or withdrawal
Interstitial lung disease - withdrawal
Adverse events leading to discontinuation
Reason
SRL
(N=85)
CNI
(N=53)
Chronic allograft
nephropathy
Raised creatinine
Mouth ulcers
Pneumonitis
Rash
Diarrhoea
Other Adverse Event
0
1
1
6
2
10
3
10
1
0
0
0
0
0
Total
32
2
Transplantation 2003: 76; 364-370.
Use of sirolimus
Licensed for use with ciclosporin A for 1st
3 months only in adult renal transplant
– Rarely used in this way
Where to position sirolimus?
– Replace CNI or replace anti-metabolite
Appears to offer better GFR (graft
survival?) than CNI maintenance.
Skin cancers??
Alemtuzumab
Licensed for chronic lypmphcytic leukaemia
Recombinant humanised mab vs CD52
– CD52 cell surface antigen
T&B lymphocytes, monocytes, macrophages
Depleting mab
– Binds and leads to immediate cell lysis
Single 30mg dose leads to profound lymphocyte
depletion
– Persists 6-12 months before recovery
– Optimal dose, frequency & timing unknown
Mainly as induction immunosuppression
Instead of rATG or IL-2R mabs
– Also used to treat acute rejection
Very limited RCT evidence
Similar 1 year graft/patient survival & ACR
incidence to basiliximab, dacilzumab & rATG
Infusion-related ADRs very common
– Fever, rigors, hypotension, urticaria,
hypotension, bronchospasm, ARDS, arrest
– Must be infused over 2 hours
Preceded by iv MePred, Piriton & paracetamol
Pancytopenia, leukopenia,
thrombocytopenia
Rituximab
Chimeric mouse/human mab vs CD20
– CD20 cell surface antigen
Pre-B & mature B lymphocytes
– Not stem cells or other cell lines
Depleting mab
– Inhibits B cell proliferation
Reduces PRA titre
– New, healthy cells regenerate 9-12 months
Effects still apparent at 15 months
Role of rituximab in transplant unclear
– Licensed for lymphoma/leukaemia &
autoimmune disorders
Humeral rejection episodes
Some data but no local experience
Pre-transplant, pre-conditioning regimes
– High donor-relevant HLA antibody titre
With DFPE, IVIG (?), mycophenolate
Single doses 375mg/M2
– ABO incompatible transplant
Early infusion-related ADRs in > 50%
– Classic ‘cytokine –release’ syndrome
– Fever, rigors, hypotension, urticaria,
bronchospasm, angioedema, ARDS, death
– Infusion started slowly and rate adjusted
Preceded by iv steroid, Piriton & paracetamol
Tumour-lysis syndrome association
Leucopaenia/thrombocytopenia
– Less common than with alemtuzumab
Anti-CD 25 antibodies
Two IL-2 receptor (IL-2R) ‘mabs’
– Daclizumab
– Basiliximab
Both ‘humanised’ monoclonal antibodies
against the  chain of IL-2R
– aka anti-Tac/CD25 antibodies
Bind to, saturate & block activated IL-2R
– don’t affect resting T-cells
Both manipulated to prevent patient
antibody formation
– unlike OKT3 or ???Thymoglobuline
Used exclusively as induction agents
– Duration
Pooled analysis for anti-CD 25 antibodies
Biopsy confirmed
acute rejection
absolute difference
(95% CI)
Biopsy confirmed
acute rejection
odds ratio
(95% CI)
Daclizumab
versus
placebo
-16%
0.48
(-24% to –8%)
(0.33 to 0.70)
Basiliximab
versus
placebo
-14%
0.51
(-20% to –9%)
(0.40 to 0.65)
New Engl J Med
1998: 338; 161-165
Transplantation
1999: 67; 110-115
Lancet 1997: 350;
1193-1198
Transplantation 1999:
67; 276-284
Transplantation 2001:
72; 1261-1267
IL-2R blocking ‘mabs’
Advantages
– reduce renal rejection rates
by approx 30% in classic
triple therapy
– short courses
iv, in hospital only
Compliance guaranteed
– ‘Few’ adverse effects
Severe re-exposure
hypersensitivity seen with
both
Disadvantages
– Cost
But cost-effective to add
basiliximab to ciclosporin
regimens
Same report states that
should not be added to
tacrolimus based
regimens.
– Daclizumab is a 5 dose,
fortnightly regimen &
requires infusion