Immunosuppressants

Very, very powerful Immunosuppressants available

Non-Pharmacological:• Irradiation • Plasmapheresis removal of autoantibodies in diseases like MG

Pharmacological:• deplete T cells or B cells completely with anti-CD3 or anti-CD20 antibodies• chemotherapy • calcineurin inhibitors, steroids

Problem: Immunosuppression (infections)

Side-Effects of Immunosuppressants

1) General Side Effect: Immunosuppression• Reactivation of latent viral infections (e.g. herpes, varicella, CMV, PML)• Bacterial and fungal infections • Bone marrow suppression• Increased risk of cancer

2) Specific Side Effects:• Nephrotoxicity of the calcineurin inhibitors• Metabolic changes with steroids• “cytokine release syndrome” with anti-CD3 Ab

Corticosteroids

broad anti-inflammatory effects

High dose pulses of i.v. methylprednisolone (SOLU-MERDOL, A-METHAPRED) used to reverse acute transplant rejection and acute exacerbations of autoimmune diseases like MS or SLE

also used to suppress allergic reactions to biologics (e.g. first-dose cytokine storm in transplantation with muromonad-CD3 or thymoglobulin)

Invaluable for short-term use!!!

Cytotoxic Agents

Are typically covered in Oncology.

For this lecture it is sufficient you to know that all cytotoxic drugs that are used for cancer therapy also hit all fast dividing cells in the body:

• immune system• gut mucosa• hair follicles

Cyclophosphamide and methotrexate often used in RA and MS

Calcineurin Inhibitors:• Cyclosporine

• Tacrolimus

Bind to immunophilins (cyclophilin or FK506-binding protein [FKBP]) forming a complex that inhibits calcineurin Calcineurin does not dephosphorylate NFAT NFAT does not translocate to the nucleus Inhibition of T cell proliferation and IL-2

production

Cyclosporine (Cyclosporin A)

cyclic 11 amino acid polypeptide (very lipophilic, orally absorbed)

very effective against T cell dependent responses, less effective against B cells

Therapeutic uses:• kidney, liver, heart and other organ transplantation• severe cases of RA• severe disabling psoriasis where other therapies have failed

Pharmacokinetics:• Administered i.v. (SANDIMMUNE Injection) or orally • oral availability 20-50% [Different formulations like SANDIMMUNE gelatine capsules and NEORAL microemulsion are NOT bioequivalent; should not be freely substituted!!!]• plasma peak between 1.5 to 2 h; t1/2 5-18 hours• extensively metabolized through CYP3A4; excreted through bile Plasma drug levels must be monitored, drug interactions avoided and doses adjusted for hepatic insufficiency

Drug Interactions with Cyclosporine any drug that is metabolized through CYP3A4 affects CsA metabolism

CYP3A4 blockers (ketoconazole, fluconazole, verapamil, idinavir, grape fruit juice) increase CsA plasma levels

CYP3A4 inducers (phenobarbital, phenytoin) reduce CsA plasma levels

Cyclosporine Side Effects1. Nephrotoxicity: occurs in nearly all patients cessation

or modification of therapy2. Hypertension: occurs in ~50% of kidney and 100% of

heart transplant patients3. Hyperlipidemia4. Tremor5. Hirsutism and hypertrichosis6. Diabetogenic in combination with glucocorticoids

Tacrolimus (FK506)

macrolide antibiotic produced by Streptomyces tsukunaensis

available for oral and i.v. administration (PROGRAF)

t1/2 ~12 hours, PK variable. Metabolized through CYP3A4 (same interactions like CsA)

Therapeutic Uses:• Similar to CsA but much less commonly used• “Rescue Therapy” in patients who show rejection despite therapeutic CsA plasma levels

Side Effects:• Same as CsA, nephrotoxicity is limiting

Sirolimus (Rapamycin) RAPAMUNE Macrocyclic lactone produced by Streptomyces hygroscopicus (soil of Easter Islands)

Originally developed by Wyeth as an antifungal when it was found to be an immunosuppressant

Mechanism of Action:• Inhibits T cell activation downstream of the IL2 receptor by binding to the immunophilin FKBP-12

sirolismus-FKBP-12 complex inhibits the protein kinase mTOR (mammalian target of rapamycin), which is a key enzyme in cell-cycle progression cell cycle arrested in G1-S phase transition

PK:• oral availability ~15%, plasma peak after 1-2 hours, t1/2 = 62 h, metabolized by CYP3A4

Sirolimus continued

Therapeutic Uses (introduced in 1999):

• used in combination with calcineurin inhibitors and glucocorticoids for organ transplantation (Synergy!!)

• in patients experiencing or at high risk for calcineurin-inhibitor associated nephrotoxicity used with glucocorticoids and mycophenolate mofetil to avoid permanent renal damage

• also coated onto stents to prevent restenosis following angioplasty

Side Effects:

• increase in cholesterol and triglycerides

• delayed wound healing ( often started delayed after surgery)

• much less nephrotoxic than calcineurin inhibitors but carries warning about associated nephrotoxicity since Oct. 2008

Cyclosporine and Sirolismus (rapamycin) are synergistic Often combined to reduce CsA toxicity

Azathioprine (IMURAN)N

N NH

N

S N

NO2N

CH3

Mechanism of Action (Antimetabolite):Cleaved by nucleophiles like glutathione to 6-mercaptopurine Inhibits purine synthesis and thus cell proliferation

Therapeutic Uses:• in combination for organ transplantation• severe RA

Side Effects:• bone marrow suppression (leukopenia, sometimes thrombocytopenia)• hepatotoxicity• increased risk of infections and cancer

Mycophenolate Mofetil (CELLCEPT)

Prodrug (2-morpholinoethyl ester) that is rapidly hydrolyzed to mycophenolic acid (MPA), which is a reversible inhibitor of ionosine monophosphate dehydrogenase (IMPDH), an enzyme involved in guanine nucleotide synthesis

T and B cells highly dependent on guanine nucleotide synthesis ( other cells can use other pathways) MPA inhibits T cell and B cell proliferation as well as antibody production

O

OH

O

OOH

MeO

Mycophenolic acid (MPA)

Therapeutic Uses:• Prevention of transplant rejection (typically in combination with glucocorticoids and calcineurin inhibitors)• approved for renal transplant in 1995, other transplants later; indications might widen in the future

Side Effects:• Leukopenia• Increased incidence of infections (in June 2006 Roche and FDA issued warning about PML; 17 cases, 7 fatal)

Progressive Multifocal Leukoencephalopathy (PML)

PML is a rare demyelinating disease of the CNS that usually is fatal or leads to severe disability. PML is caused by reactivation of the JC virus, a polyomavirus that resides latently in 70-90% of adults worldwide.

PML presents with ataxia, hemiparesis, confusion, apathy, cognitive deficiencies and radiographic evidence of white matter disease.

PML should be considered in any transplant or autoimmune disease patient who is on immunosuppression and who presents with neurological symptoms.

Other than reducing the dose of immunosuppressant there are no interventions that can stop or treat PML.

[see also Natalizumab for MS treatment]

FTY720

NH2

OH

OH

Fingolimod (FTY720) is sphingosine-1-phosphate receptor 1 agonist that prevents egress of lymphocytes from lymph nodes

was not superior to calcineurin inhibitors in Phase-3 clinical trial for kidney transplantation as a monotherapy

Very encouraging effects in Phase-2 clinical trial for MS (relapse rate reduced by 80%); various other trials going on

FTY720 sequesters T cells in lymph nodes and prevents them from recirculating

Will probably become a new drug for combination therapy

Antithymocyte Globin (THYMOGLUBIN)

Purified gamma globulin fraction from the serum of rabbits immunized with human thymocytes

contains cytotoxic Abs that bind to CD2, CD3, CD4, CD8, CD11a, CD18, CD25, CD45 and MHC class I and II (and probably a lot more!!)

Abs deplete circulating lymphocytes by direct cytotoxicity (complement and cell mediated) and block cell surface receptors

Therapeutic Uses:• Approved for acute renal transplant rejection• Often used immediately after kidney transplant if graft function is delayed to avoid early use of nephrotoxic calcineurin inhibitors

Toxicity:• Polyclonal rabbit Ab xenogenic protein elicits acute allergic reactions (fever, chill, hypotension) premedication with glucocorticoids, acetaminophen and antihistamines• Anti-ATG Abs develop but do not limit repeated use

Anti-CD3 Monoclonal Antibodies

Antibodies directed against the chain of the T cells receptor CD3 treatment induces rapid internalization of the TCR and is followed by depletion and extravasation of T cells from the blood and lymphoid organs (redistribution to the lungs)

Muromonab-CD3 (OKT3) original mouse IgG2a introduced in 1986 Fully humanized Ab: hOKT1; less cytokine release

Therapeutic Uses:• Mouse Ab still used to reverse glucocorticoid resistant rejection episodes (repeated use results in neutralizing Abs)• Humanized Ab for treatment and prevention of acute rejection • Phase-2/3 clinical trials for prevention of T1DM

Side Effects:• “cytokine release syndrome” typically 30 min after infusion (TNF, IL2, IL6, INF from activated T cells and macrophages) high fever, chills, tremor (worst on first dose)• Glucocorticoid administration on first dose is now standard

Rituximab (RITUXAN)

monoclonal anti-CD20 Ab approved in 1997 for the treatment of B-cell non-Hodgkin lymphomas

binds to CD20 on the surface of B cells and seems to induce apoptosis of CD20+ cells and/or induce complement and cell mediated cytotoxicity (ADCC), drastically reduces number of circulating B cells

Therapeutic Uses:• Leukemia, lymphoma [see Hem/Onc]• In combination with methotrexate for severe RA• Clinical trials ongoing for various autoimmune diseases including idiopathic autoimmune hemolytic anemia, MS, T1DM, Sjogren's syndrome, SLE

Side Effects:• Infusion reactions similar to anti-CD3 Abs• Immunosupppression [carries Box Warning about PML]

Anti-CD25 (Anti-IL-2 Receptor)

Daclizumab (ZENAPAX): humanized chimeric monoclonal Ab

Basiliximab (SIMULET): murine-human chimeric monoclonal Ab

both Abs seem to inhibit activated T cells without significant depletion

Therapeutic Uses:• Prophylaxis of acute transplant rejection (pre-operatively and afterwards in biweekly intervals)• Combination for maintenance therapy with other immuno-suppressants (azathioprine, glucocorticoids, cyclosporine)

Side Effects:• no cytokine release syndrome• anaphylaxis can occur

Abatacept (ORENCIA)

fusion protein composed of human immunoglobulin fused to the extra-cellular domain of CTLA-4

Costimulation of CD28 through B7-1/2 (CD80/CD86) is necessary for full activation of naïve T cells; Engagement of the related receptor CTLA-4 inhibits/reduces T cell activation Abatacept prevents co-stimulation and can potentially induce tolerance

Abatacept continued

Therapeutic Uses:• Currently approved for RA patients who have failed methotrexate and anti-TNF reagents• Currently in clinical trials for T1DM prevention, colitis, psoriasis and transplant rejection

Side Effects:• usual risk of increased infections and malignancies• should not be used in combination with TNF-antagonist (no additional benefit and greatly increased risk of infections)

Anti-TNF Reagents Infliximab (REMICADE): chimeric anti-TNF- monoclonal Ab containing a human constant and a murine variable region; binds with high affinity to TNF- and prevents it from binding to its receptor

Etanercept (ENBREL): Fusion protein of Fc portion of human IgG1 and ligand binding portion of TNF- receptor

Adalimimab (HUMIRA): fully humanized recombinant monoclonal anti-TNF- antibody for i.v. use

Therapeutic Uses: Infliximab and Adalimimab: approved for psoriasis, Crohn's disease, ankylosing spondylitis, psoriatic arthritis, rheumatoid arthritis, sarcoidosis and ulcerative colitis Etanercept (various formulations including autoinjector pen): approved for RA; $4.3 billion sales in 2006!! (7th top selling drug)

Side Effects:• Increase incidence of lymphomas and infections [Black box warning]• Rare cases of demylelination (contra-indicated in MS)

Other Biologics[Recently introduced or in Development]

Efalizumab (RAPTIVA): targets LFA-1 and blocks T cell adhesion and activation

Anakinra (KINERET): IL-1 receptor antagonist approved for RA

Alefacept (AMEVIVE): Fusion protein that targets CD2, approved for moderate to severe psoriasis

Campath-1H (ALEMTUZUMAB): humanized anti-CD52 Ab depletes T cells, B cells, macrophages and NK cells; approved for renal transplantation

Anti-IL-12/IL23 antibody: clinical trials for MS and RA

There will be many more new immunosuppressants in future as we understand the immune system better.

Therapy of Organ Transplantation

For solid organs like heart and kidney it is rarely possible to achieve perfect HLA matching because of limited supply of organs (exception: live kidney donation from identical twin)

Strong immunosuppression necessary

At most transplant centers intensive biologic induction therapy followed by maintenance therapy

Induction Therapy (delays use of nephrotoxic agents):• Anti-CD3 Abs ( anti-CD25)• Antithymocyte globin• plasmapheresis if high titers of anti-HLA antibodies

Maintenance Therapy (typically triple therapy at low doses for synergy):• calcineurin inhibitor + glucocorticoid + mycophenolate mofetil• sirolimus + glucocorticoid + mycophenolate mofetil• calcineurin inhibitor + sirolimus + third agent

Therapy of Organ Transplantation

Therapy of Established or Acute Rejection:

• High dose methylprednisolone• Anti-CD3 Abs ( anti-CD25)• Antithymocyte globin

Calcineurin Inhibitors and kidney transplants:• Ultrasound guided biopsy best way to differentiate nephro-toxicity (too much CsA) from rejection (too little CsA)

Future??Currently a lot of research going on into the possibility of achieving tolerance with sirolimus (spares Tregs in contrast to CsA) and/or abatacept

Therapy of Autoimmune Diseases

Typically “milder” immunosuppression used than for prevention of transplant rejection

Choice of therapy should be guided by:

1. Knowledge about specific pathology of autoimmune disease

2. Careful weighing of benefits of therapy versus side effects since treatment is typically for the rest of the patient’s life

Example of a “bad” strategy:In the late 1980s and early 1990s cyclosporine was used to prevent T1DM during the “honeymoon” period very effective at preventing T1DM but abandoned because of nephrotoxicity

Example: Rheumatoid Arthritis

American College of Rheumatology recommends that treatment should be chosen based on:

how long a patient has had rheumatoid arthritis the severity of rheumatoid arthritis symptoms potential for side effects tuberculosis screening (required before starting biologic DMARDs) cost of treatment (real issue with biologics!!) patient preference regarding treatment options

DMARD = disease modifying anti-rheumatic drugs (as opposed to NSADs like aspirin that purely treat the symptoms)

The 2008 ACR Recommendations for Rheumatoid Arthritis Treatments:

Initiating treatment with methotrexate or leflunomide for most RA patients

Methotrexate plus Plaquenil (hydroxychloroquine) for RA patients with moderate to high disease activity

Treatment with TNF- antagonist (etanercept, infliximab, adalimumab) plus methotrexate for patients with early rheumatoid arthritis (symptoms for less than 3 months) and high disease activity

For RA with moderate to long disease duration, TNF- antagonists for those who failed to get a satisfactory response from methotrexate therapy

Abatacept and rituximab should be reserved for patients with at least moderate disease activity and inadequate treatment response to other agents

Treatment with methotrexate or the biologics should not be resumed or started during an active bacterial or viral infection

Severe flair-ups: CsA or methylprednisolone

Example: Multiple Sclerosis

Chronic, immune-mediated demyelinating disease of the CNS that is characterized by inflammation, gliosis and axonal damage

Most common neurological disease in young adults (age of onset 15-50 years); affects 400 000 people in the US and about 2.5 million worldwide

•

•

MS is a T cell mediated disease

myelin-antigen specific T cells with a Th1 profile can be isolated both from the blood and the CSF of MS patients

Although myelin-antigen specific T cells are also present in the blood of healthy controls and occur with the same frequency, their activation state in MS patients is different. Myelin-reactive MS patients T cells secrete larger amounts of IL-2, IFN- and TNF- than T cells from controls, and are predominantly of a Th1/Th0 memory phenotype

CD4

CD3

Extravasating T cells in a postmortem brain section from a MS patient

FDA APPROVED TREATMENT OPTIONS FOR MS

Immunomodulatory drugs:• IFN-• Copaxone (Glatiramer acetate)• Natalizumab

Immunosuppressive drugs:• Acute severe attack: methylprednisolone• Cyclophosphamide and mitoxantrone for secondary

progressive and primary progressive MS

[Diagnosis and symptoms of MS will be covered in Neurology]

Interferon- naturally occurring cytokine with still unknown mechanism of action: - suppresses T cell proliferation - reduces T cell migration into the CNS - changes cytokine profile from Th1 to Th2 (?)

like most proteins interferons are potentially immunogenic (especially when produced recombinantly altered glycosylation) and neutralizing Abs appear in many patients still hotly debated whether these antibodies reduce efficacy of INF-

Glatiramer Acetate (Copaxone)

random polymer of glutamic acid, lysine, alanine and tyrosine (which compose MBP) with unclear mechanism:

1) induction of tolerance to MBP (?)2) induces a population of GA-reactive Th2-type

“regulatory” T cells that secrete Th2 cytokines in the brain and create an “anti-inflammatory milieu” either spontaneously or after cross-stimulation with myelin antigens (?)

long-term treatment also seems to induce serum Abs

Phase III Trials: Reduction in Annual Relapse Rate

*For patients who had been in the study for 2 years.

Jacobs et al. Ann Neurol. 1996;39:285; IFNB MS Study Group. Neurology. 1993;43:655; IFNB MS Study Group and University of British Columbia MS/MRI Analysis Group. Neurology. 1995;45:1277; Johnson et al. Neurology. 1995;45:1268; PRISMS Study Group. Lancet. 1998;352:1498;

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Avonex30 mcg

Betaseron875-1000 mcg

Copaxone140 mg

Rebif

66 mcgRebif

132 mcg

P=0.002*

P=0.0004 P<0.0001P<0.0001

P=0.007

30

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20

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INF- INF-

Natalizumab (Tysabri)Anti-VLA-4 Monoclonal Antibody

66% reduction in relapses 92% reduction in active MRI lesions Monthly IV administration 2/1200 patients treated developed PML and died

Tysabri removed from the market in early 2005

March 2006: an FDA advisory committee recommended that it should return to the market (massive pressure from MS patients and NMSS)

Symptom Management of MS

PrimaryCaused by actual demyelination within the CNS

Fatigue, tremor, incontinence, spasticity, depression

antidepressants, anti-spastics

SecondaryCaused by failure to manage the primary

Contractures, decubiti, fractures, muscle atrophy

physiotherapy

TertiaryPsychological, social, marital, vocational, personal antidepressants, Viagra, Life-style changes