THERAPEUTIC AGENTS - PowerPoint PPT Presentation

Loading...

PPT – THERAPEUTIC AGENTS PowerPoint presentation | free to download - id: 3fca45-MmU2M



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

THERAPEUTIC AGENTS

Description:

THERAPEUTIC AGENTS N7-2006 L. Duroux Slides assembled from diverse sources Recommended reading list - textbooks Novel Therapeutic Proteins (2001) Peter Stadler ... – PowerPoint PPT presentation

Number of Views:239
Avg rating:3.0/5.0
Slides: 122
Provided by: AthenaF2
Learn more at: http://homes.nano.aau.dk
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: THERAPEUTIC AGENTS


1
THERAPEUTIC AGENTS
N7-2006 L. Duroux Slides assembled from diverse
sources
2
Recommended reading list - textbooks
  • Novel Therapeutic Proteins (2001)
  • Peter Stadler Klaus Dembowsky
  • Wiley-VCH, ISBN 3527302700
  • Human Gene Therapy (2003)
  • Gabor M. Rubanyi Seppo Ylä-Herttuala
  • Springer, ISBN 3540004130
  • The Development of Human Gene Therapy (1999)
  • Theodore Friedmann
  • CSHL Press, ISBN 0879695285

3
Lecture Plan
  1. Introduction
  2. Recombinant Proteins
  3. Nucleic Acids

4
1. INTRODUCTION
5
Therapeutic Agents
  • Before the advent of molecular biotechnology most
    human proteins were available in only small
    (limited) quantities.
  • Today hundreds of genes (1000) for human
    proteins have been cloned, sequenced, expressed
    in the host cells and are being tested as
    therapeutic agents (drugs) in humans.

6
Biotechnology Today
  • 4400 biotech companies worldwide
  • Sales of 40-50 billion
  • 1500-2000 biotech companies in US
  • 160,000 employees
  • Major biotech companies include Genetech, Amgen,
    BiogenIdec, Genzyme, Centocor, MedImmune, Chiron,
    Novo Nordisk, Serono
  • Many large pharma companies investing in biotech

A. Demain, 2004, ChimicaOggi
7
Biopharmaceuticals
  • Over 140 on the market over 400 in clinical
    trials
  • Biopharmaceuticals include
  • Proteins (made in bacterial, fungal or mammalian
    cell culture)
  • erythropoietin (EPO)
  • insulin
  • interferon (Intron A)
  • granulocyte-colony stimulating factor (G-CSF)
  • human growth hormone (HGH, human somatotropin)
  • tissue plasminogen activator (tPA)
  • Monoclonal antibodies (made in mammalian cell
    culture)
  • Vaccines
  • live and inactivated viruses and bacteria
  • subunit vaccines
  • recombinant vaccines
  • Gene Therapy Products (viral and non-viral)

8
FDA-Approved Antibodies
9
Recombinant Protein Production(including MAbs)
Formulation/ Filling
Transfection
Cell culture
Purification

Drug product - (sterile)
Cells and plasmid
Cell line
Drug substance (crude)
Drug substance (pure)
10
Bioprocess Engineering in Recombinant Protein
Production
Formulation/ Filling
Transfection
Cell culture
Purification

Drug product - (sterile)
Cells and plasmid
Cell line
Drug substance (crude)
Drug substance (pure)
Cell line manufacture Medium development
Bioreactor process development scale-up
Downstream purification
Analytical characterization
11
BIOPROCESS ENGINEERING
  • Natural products
  • mostly from fungi and actinomyctes
  • filamentous organisms
  • many anti-fungal, anti-bacterial, anti-cancer
    compounds
  • also statins for lowering cholesterol are natural
    products and semi-synthetics Zocor (Merck),
    Lipitor (Pfizer)

12
BIOPROCESS ENGINEERING
  • Gene Therapy Products
  • gene delivered by one of many vehicles
  • Non-viral vectors naked DNA, DNA plasmid,
    liposomes
  • Viral vectors adenovirus, retrovirus,
    lentivirus, adeno-associated virus

J.R. Morgan and M.L. Yarmush, Gene Therapy in
Tissue Engineering. InC.W. Patrick, A.G. Mikos,
L.V. McIntire, eds. Frontiers in Tissue
Engineering, Elsevier Science Publishers, 1997
13
The Drug Development Process
Regulatory Considerations
Lead Optimization (metabolism, toxicology)
Process Development/ Material Generation
Drug Discovery
Animal Clinical Testing
Iterative Process
14
Bioprocess Development
Biological Assay Development and Support
Cell/Virus Culture Development/ Media
Optimization
Purification Process Dev.
Cell Line/ Viral Vector/ Construction
Formulation Design/ Drug Delivery Design
Facility/Equipment Design Technology
Transfer Process Validation Pilot-Scale cGMP
Production Commercial-Scale Production
15
2. Recombinant Proteins
16
2A. Human Interferons
  • Fighting Viral Infections

17
Mechanisms of Resistance against Infections
18
What is Interferon?
  • Scientists discovered an antiviral protein in
    1957 that inhibited growth of influenza virus in
    chicken embryos. It was named interferon because
    it interfered with the growth of influenza virus.

19
Interferons
  • Anti viral proteins released by host cells
  • Interfere with viral multiplication
  • Host cell specific but not virus specific
  • Different types of cells in animals produce
    different interferons

20
Human Interferon
  • 3 types
  • alpha interferon (13 genes)
  • beta interferon (2 genes)
  • gamma interferon (1 gene)
  • Alpha beta usually produced early in viral
    infections (viruses or viral RNA)
  • Gamma appears later
  •    

21
Interferon
  • Presence of double-stranded RNA indicates cell is
    infected
  • Viral infected cells release alpha and beta
    interferons
  • Diffuse to neighboring cells
  • Virus cant replicate

22
Antiviral Treatment
  • Interferon therapy
  • Limited lifetime, short lasting effect
  • Recombinant interferons
  • Pure and fast
  • Hybrid genes for enhanced/new activity
  • Oral administration

23
AMARILLO Biosciences Inc.s IFNa
24
  • Amarillo Biosciences, Inc. (ABI)
  • (OTCBBAMAR)
  • 806-376-1741 ? Fax 806-376-9301
  • E-mail abi_at_amarbio.com
  • October 31, 2006

25
The Company
Amarillo Cell Culture Company, Inc. was formed in
1984. The Company is the world leader in the
development of low-dose interferon-alpha for oral
delivery to humans and animals. Before an initial
public offering in 1996, the name of the Company
was changed to Amarillo Biosciences, Inc. (ABI).
The Companys goal is to achieve regulatory
approval of a safe and effective low dose oral
formulation of a human interferon alpha.

26
Company Overview
  • Founded in 1984
  • Product focus - oral delivery of interferon
    alpha
  • 8 active Investigational New Drug (IND)
    applications in USA
  • 24 human clinical trials completed or ongoing
  • 50 animal clinical trials worldwide
  • Advanced clinical development programs
  • Phase 2 in oral warts for HIV patients
    enrollment starting in November
  • Phase 2 in Behcets disease in Turkey 39 of
    90 patients enrolled
  • Phase 2 in chronic cough planned
  • Strategic alliance with Hayashibara Biochemical
    Laboratories

27
Why are Side Effects Common and Severe for
Injectable Interferon?
  • Injectable interferon is approved world-wide for
    the
  • treatment of various cancers and viral diseases.
  • Interferon is a protein readily eliminated from
    the blood
  • by the kidney. To counteract the kidneys
    clearance of
  • interferon from the blood injectable interferon
    must be
  • given in doses much higher than what occur
    naturally.

28
How is Oral Interferon Different?
  • Low-dose oral interferon is given in doses 10
    thousand times less than injectable interferon.
    Therefore, side effects are dramatically reduced.
  • Oral interferon is human interferon alpha
    administered in a small tablet (lozenge) to
    humans or in powder to animals.
  • Oral interferon binds to surface (mucosal) cells
    in the mouth and throat resulting in stimulation
    of white blood cells and activates hundreds of
    genes affecting the immune system in the
    peripheral blood of man, cattle and mice.
  • Studies show oral interferon is effective against
    disorders such as cancer, viral diseases and
    autoimmunity.

29
What is Special about ABIs Oral Interferon?

Comparison Oral Injectable Dose Up to 500
IU Up to 10,000,000 IU Side Effects Rare/mild
Common/severe Treatment Cost Cost
Effective Expensive Administration
Lozenge/powder Needle/syringe Physician
Visits Infrequent Frequent Stability Stable at
Room Refrigeration Required Temperature

30
Unique Oral Formulation
VELDONA (Very Low Dose Oral Natural Alpha) is the
brand name of the interferon lozenges which have
been tested in thousands of patients. The formula
is stable at room temperature for 2 years and at
refrigeration temperature for 5 years.
The combination of IFN? subspecies (INF?2b, INF?7
and INF?8) provide superior immunomodulatory,
anticancer and antiviral effects.
31
Manufacturing Steps for ABIs Interferon
32
Mechanism of Action
Oral Epithelial Cells
Tonsil
IFNa
Mandibular Lymph Nodes
Activation of Perioral Lymphoid Cells and
Peripheral Lymphoid Tissues
Activation of Humoral Immunity (Antibody)
Activation of Cell Mediated Immunity
Virus
Interferon placed in the mouth binds to receptors
in the mucosal lining and initiates systemic
effects on the immune system in animals and man.
These immunomodulatory effects are safe and
effective in helping control viral and autoimmune
diseases and cancer.
33
Intellectual Property
The Company has 13 issued and one pending patent
with claims to the manufacture of the oral
formulation or the use of interferon orally to
manage numerous diseases. ABI has clinical data
on safety and efficacy from 24 human and 50
animal studies.
34
ABIs Pipe Line for Human Health
Human diseases in which oral interferon has been
tested and reported to be safe
35
The market for Injectable interferon exceeds 5
billion annually. The Company believes low dose
oral interferon is superior to injectable in
safety, cost and ease of administration. The
Company is working toward FDA approval for oral
interferon to treat influenza, Behcets disease,
oral warts in HIV patients and in idiopathic
pulmonary fibrosis. Once oral interferon is FDA
approved, the Company projects sales to exceed
100 million annually.
36
Oral Interferon Human Health Market Europe and
United States
Disease Population Potential Market

Oral Warts in HIV Patients 80,000 170 million
Behcets Disease 39,000 40 million
Influenza (seasonal) Cough (COPD IPF) 77 million 39 million Over 1 billion Over 1 billion
37
Influenza - Introduction
  • Highly contagious, acute respiratory illness
    known as influenza has caused epidemics and
    pandemics of humans and animals for centuries.
  • About 20 of children and 5 of adults worldwide
    develop symptomatic influenza each year.
  • Most influenza infections are spread by
    virusladen respiratory droplets through coughing
    and sneezing.
  • Influenza can be transmitted to people by pigs or
    birds.

38
Human Study Influenza and Interferon
  • 14,000 people participated in controlled studies
    of placebo versus interferon treatment during a
    natural outbreak of Hong Kong influenza.
  • Interferon (about 128 units) or placebo was
    dripped into the nose daily for 5 days starting
    about the time of the first reported influenza
    cases.
  • Interferon significantly (Plt0.01) reduced the
    number of influenza cases.

Soloviev, Bull. WHO 41683-688, 1969.
39
Oral Interferon Protected Mice Against a Fatal
Challenge of Influenza
40
Summary - Oral Interferon
  • Patented oral interferon technology upregulates
    hundreds of genes affecting immune function -
    stable at room temperature for 2 years, safe and
    effective without significant side effects, easy
    to administer.
  • Injectable interferon market is 5 billion for
    treatment of cancer, autoimmune and viral
    diseases although side effects are moderate to
    severe for many patients.
  • Potential US European markets for oral
    interferon treatment of oral warts in HIV
    patients, Behcets disease, influenza and cough
    over 1 billion
  • Company Goal - Achieve regulatory approval of a
    safe and effective low dose oral formulation of a
    human interferon alpha.

41
Strategies for Optimisation of Recombinant
Production
  • Screening libraries of recombinant genes (IFNs,
    human growth hormone, TNF-a)
  • Screening of recombinant expression systems (E
    coli, fungi, Mammalian cells)
  • Delivery by intestinal bacteria (lactobacilli)

42
2B. Enzymes
  • Treating Cystic Fibrosis

43
A Fatal Genetic Disease
  • Cystic fibrosis (CF) is one of the most fatal
    heredity diseases among European and their
    descendants with 30,000 cases in the US and
    23,000 in Canada.
  • Furthermore among European descendants it occurs
    in 1 in 2,500 live birth and 1 in 25 are
    carriers.
  • It is caused by more than 500 different mutations
    in the cystic fibrosis transmembrane conductance
    regulator (CFTR) gene.
  • Individuals with CF are highly susceptible to
    bacterial infection and antibiotic treatment
    often results in resistant strains.

44
Symptoms of Cystic Fibrosis
  • Clogging and infection of lungs
  • plugging of small bile ducts in liver (impedes
    digestion)
  • plugging of ducts of pancreas (impedes digestion)
  • obstruction of small intestine
  • males are infertile (blocked vas deferens)
  • malfunctioning sweat glands

The theme is that small ducts become clogged with
a thick mucus
45
A variety of organs are affected
46
A large effort was launched to identify the gene
responsible
  • Identified a gene on chromosome 7
  • CF was caused by a 3 base pair deletion in Cystic
    Fibrosis Transmembrane Regulator (CTFR)
  • The gene is very large

47
The CF gene
48
How could such a minor change cause such a
dramatic effect?
  • F508 is deleted
  • The encoded protein looks like an ABC transporter
    coupled to a channel
  • If the mutant protein is isolated and put into a
    membrane it will function normally
  • So what is wrong?

49
Improperly folded proteins are not allowed to
leave the ER
Currently theories are that the protein is not
recognized as being properly folded
50
How does this protein work?
  • The gene is a pore coupled to two ABCs
  • It transports Cl- ions after being phosphorylated
    and binding two ATP molecules
  • It has a large regulatory domain that is
    phosphorylated by a cAMP dependent protein kinase

51
(No Transcript)
52
The proteins physiological role
A normal lung Chloride into airway sodium out
- keeps mucus moist and thin Normal CFTR
regulates the sodium channel (inactivates it)
53
A CF Lung
Chloride does not get into airway more sodium
leaves More salt in cell - water comes in This
makes the mucus thick
54
The resultphysiology of a normal lung
55
The result physiology of a CF lung
56
Treatments
  • Chloride delivery - activate other chloride
    carriers
  • Viscous mucus - pounding, DNase treatment,
    gelosin
  • recurrent infections - antibiotics
  • tissue damage due to immune response -
    anti-inflammatory drugs (ibuprofen)

57
DNase 1 (GeneTech)
  • A thick mucus which is a results of
  • Alignate produced by bacteria
  • DNA from lysed cells
  • Leucocytes which accumulate due to the infection
  • Makes breathing difficult.
  • Scientist at Genentech isolated the gene for
    DNase1
  • The purified enzyme was delivered as an aerosol
    to the lung where it hydrolysed the DNA into
    short oligonucleotides.
  • This decrease the viscosity in the lungs and made
    breathing easier.

58
Alginate Lyase
  • Alginate is a polysaccharide polymer that is
    produced by seaweed and some soil and marine
    bacteria.
  • The excretion of alginate by Pseudomonas
    aeruginosa of patients with CF contributes to the
    viscosity in the lung.
  • The enzyme alginate lyase can liquefy bacteria
    alginate.
  • Alginate lyase was isolate from Flavobacterium
    sp. and cloned into E. coli.

59
Alginate Lyase
  • The expressed gene produced a protein of 69,000
    Da.
  • The 69,000 Da protein produced a proteolytic
    enzyme of 6,000 Da.
  • The remain 63,000 Da protein was cleaved to
    produce a 43,000 Da which is able to liquefy
    bacterial alginate.
  • Combined with DNase1, alginate lyse is able to
    reduce the mucus in the lungs of patients with CF.

60
Alginate lyase
61
2C. Monoclonal Antibodies
62
Clinical Applications
  • Transplantation muronomab (OKT3) 1986,
    basiliximab 1998
  • Cardiovascular disease abciximab 1994
  • Cancer rituximab 1997, trastuzumab 1998
  • Viral infection palivizumab 1998
  • Inflammatory diseases infliximab 1998,
    etanercept 1999

63
Side effects
  • Transfusion reactions
  • Infections, immunosuppression
  • Cardiac, respiratory arrest
  • Pharmacological toxicity

64
Production of Monoclonal Antibodies
  • Monoclonal antibodies results from a clone of a B
    lymphocyte producing a single antibody which will
    bind to a specific epitope of an antigen.
  • What is a polyclonal antibody?
  • Monoclonal antibodies are produced
  • Fusion of a myeloma (B cell which has become
    cancerous) with a spleen cell that is immunized
    with a specific antigen.
  • The resulting hybridomas are tested for the
    production of a monoclonal antibodies.

65
Background and development
  • Diluted to one cell cultures
  • Hypoxanthine Guanine Phosphoribosyl Transferase
    (HGPT) negative myeloma cells
  • Grown in Hypoxanthine Aminopterin Thymidine (HAT)
    medium
  • De novo nucleotide synthesis blocked
  • Only successful fusion cells grow (rare)

66
Production of Monoclonal Antibodies
Major Problems with non-human ABs Immunological
Responses ? Humanization of ABs
67
The Structure of Antibodies
68
Chimeric Ab
65 90 human and consist of the murine variable
regions (? fused to the
constant or effector part)
69
Production of Human Monoclonal Antibodies by E.
coli
  • Hybridoma cells grow relatively slow and require
    expensive media.
  • To circumvent this problem human monoclonal
    antibodies are grown in E. coli.
  • The produce involves
  • mRNA is isolated from the B cell.
  • cDNA is synthesized from the mRNA by the enzyme
    reverse transciptase.
  • Both heavy and light chains are amplified
    separately from the cDNA using PCR.
  • The amplified products are cut with restriction
    enzymes and cloned into Lambda vector.

70
Production of Human Monoclonal Antibodies by E.
coli
71
Production of Human Monoclonal Antibodies by E.
coli
  • During cloning different light and heavy chains
    are cloned.
  • The DNA of one heavy and one light chain are
    cloned into the same vector.
  • Many different combinations of H and L chains are
    cloned together in the same vector.
  • Lambda is not useful for producing large amounts
    of proteins.
  • The L and H chains are excised from Lambda and
    cloned into an E. coli plasmid and the
    recombinant plasmid transformed into E. coli.

72
Production of Human Monoclonal Antibodies by E.
coli
73
Humanized Ab
95 human, and are made by grafting the
hypervariable region (or CDR) of the murine
antibody which determines Ab specificity
74
Isolation of CDR Segments
  • PCR amplification of CDR segments from mouse
    monoclonal antibody to desired target
  • Insert into cDNA clone of human antibody
  • Produce human antibody with desired CDRs and
    antigen specificity

75
Combinatorial Library
  • Create new variations of antibodies
  • New combinations of heavy and light chains
  • mRNA from immunized individual
  • PCR H and L chains
  • Clone into vector in new H/L combinations

76
Vector for Combinatorial Library
77
Antibody Display Libraries
78
Screening a M13 Combinatorial Library
79
Single-chain Fixed variable
only one heavy-chain variable
domain and one light-chain variable
domain? covalently linked by peptide
80
Single-Chain Combinatorial Antibody Library
81
Application Immunotoxins
  • Protein toxin connected to Fv region
  • Single-chain or S-S linked Fv region
  • Toxin localized to antigen-expressing cells

82
2D. Examples of Ab therapy
83
Improved Drug Targeting
84
Targeting Thrombolytic Plasminogen Activator
85
Targeting TPA
86
Dr. Judah Folkman hypothesis (1971)
In the absence of vascularisation, solid
tumours remain dormant and 23mm3 in size, with
size being limited by the ability of oxygen and
nutrients to diffuse into the tumour
Folkman J. N Engl J Med 197128511826
87
(No Transcript)
88
(No Transcript)
89
(No Transcript)
90
(No Transcript)
91
Angiogenic switch
  • Larger tumour
  • Vascular
  • Metastatic potential
  • Small tumour (12mm)
  • Avascular
  • Dormant

Bergers G, et al. Nature 2002340110
92
Bevacizumab (Avastin)
  • Recombinant humanised monoclonal antibody
    targeting the angiogenic
  • factor VEGF
  • Similar to Herceptin
  • 93 human, 7 murine

93
(No Transcript)
94
3. Nucleic Acids
95
3A. Methods
96
Nucleic Acids as Therapeutic agents
  • Many human disorders e.g. cancer and inflammatory
    conditions (virus, parasites) are often caused by
    overproduction of a normal protein.
  • Theoretically a small ss nucleic acid can
    hybridize to a specific gene or mRNA and diminish
    transcription or translation.
  • An oligonucleotide (oligo) that binds to a gene
    and blocks transcription is an antigene.
  • An oligo that binds to mRNA and blocks
    translation is called an antisense oligo.
  • Ribozyme (catalytic RNA) and interfering RNA (
    RNAi) can target specific mRNA for degradation.

97
Antisense RNAs
  • Gene segment cloned into expression vector in
    reverse orientation
  • Formation of dsRNA can interfere with RNA
    processing or translation

98
Antisense RNA Applications
  • Episomally based expression vectors with cDNA for
    insulin-like growth factor 1 (ILGF-1) receptors
    were constructed in the antisense version.
  • ILGF-1 is prevalent in malignant glioma a common
    form of brain cancer and prostate carcinoma.
  • Culture of glioma cells when transfected with the
    antisense version of ILGF-1 in ZnSO4 lost its
    tumurous properties.
  • A similar treatment of mice which were injected
    with prostate carcinoma cells caused small or no
    tumor to develop.

99
Antisense Oligonucleotides
  • Antisense deoxynucleotides can also be used as
    therapeutic agents.
  • However when injected into the body is
    deoxynucleotides are susceptible to degradation.
  • To prevent this modified deoxynucleotides are
    used including phosphorothioate, phosphoramidate
    and polyamide.
  • Free oligos are usually introduced into to the
    body encapsulated in a liposome.

100
Modified Deoxynucleotides
101
Modified Deoxynucleotides
102
Liposome Delivery of Therapeutic Nucleic Acids
  • Small vesicles of phospholipid bilayer
  • Fuse to cells and release contents into cytoplasm
  • Approach can target human cells and/or infectious
    agent in early stage tests (e.g. mycobacterium
    tuberculosis)

103
Antisense Oligos and Psoriasis
  • Antisense oligos have also been tested in the
    treatment of psoriasis.
  • Psoriasis is uncontrollable epidermal growth.
  • ILGF-1 receptors are implicated in the
    pathogenesis of psoriasis.
  • 15 nt antisense oligo were transferred into
    keratinocytes using liposome and the amount of
    ILGF-1 protein was decreased by 45-65.
  • When mouse with human psoriasis lesions were
    injected with anitsense oligi complementary to
    ILGF-1 receptor mRNA there was significant
    reduction (58-69) in epidermal thickness.

104
Correct Mutation in Splice Site in beta-globin
gene (Thalassemia)
  • Synthetic oligonucleotide blocks site of mutation
    which created mutant alternative splice
    junction
  • Acts at RNA level

105
RNAi
  • RNA interference or gene silencing
  • dsRNA processed by nucleases and small segments
    then target RNase to complementary RNA molecules
  • Works well in plants and many animals
  • Not humans

106
Interfering RNA
  • The addition of dsRNA to an animal cell causes
    the degradation of the mRNA from which it is
    derived.
  • This process is called gene silencing or RNA
    inference (RNAi).
  • Gene silencing has been shown to be a natural
    mechanism which plant and animals use to protect
    against viruses.
  • The dsRNA that is introduced is cleaved by
    dicer-like dsRNAse into ssRNA of 21-23 nt.
  • These short oligos complex with RISC ( RNA
    inference inducing silencing complex) which
    degrade the mRNA complimentary to the oligos.
  • This process can be used to target specific mRNA.

107
RNAi as Therapeutic Agents
  • A viral vector was used to deliver a small
    fragment of RNA to brain cells of mice with SCA1
    (human neurodegenerative disease spinocerebellar
    ataxia 1).
  • This suppress the SCA1 gene and the mice has
    normal coordination and movement.
  • Scientists are optimistic about using RNAi to
    treat other neurological diseases such as
    Alzheimers and Huntings disease.

108
3B. Gene Therapy
109
Strategies for Treating Genetic Disorders
110
Gene Therapy Clinical Trials 1990 - 1999
111
Production of Gene-encoding Vectors
112
Prodrug Activation
  • Cells of tumor often interconnected by
    cytoplasmic bridges and pores
  • Introduce expression vector into some tumor cells
  • Gene expressed converts prodrug into lethal
    compound
  • Shared with other interconnected tumor cells
  • Bystander effect

113
Prodrug Activation Systems With a Bystander Effect
114
THE END
115
HIV Therapeutic Agents
  • Acquired immune deficiency syndrome (AIDS) is
    caused by the human immunodeficiency virus (HIV).
  • The target of HIV are the T helper cells (TH).
  • TH cells play a pivotal role in the immune system
    by the release of cytokines which stimulate other
    immune cells.
  • The gp120 glycoprotein of HIV binds to CD4
    receptors of TH cells.
  • The TH cells become infected with the virus and
    are destroyed, slowly shutting down the immune
    system.

116
Interaction of HIV with CD4
117
HIV Therapeutic Agents
  • HIV antiviral strategies may include
  • Production of antibodies to CD4 (will block CD4
    receptors on TH cells and prevent infection by
    HIV).
  • Production excess CD4 protein (react with gp120
    protein therefore HIV cannot infect TH cells).
  • Both strategies do not destroy HIV but only block
    infection.
  • To stop HIV infection we need to develop
    strategies which will destroy HIV.

118
HIV Therapeutic Agents
  • One strategy which will protect TH cells and
    destroy HIV include the production of a fusion
    protein.
  • The fusion protein will have 2 parts CD4 protein
    attached to the Fc portion of an immunoglobulin
    (CD4 immunoadhesion).
  • The CD4 portion will attach to the gp120 protein
    of HIV or virus infected cells.
  • The immunoglobulin portion will initiate a
    cytotoxic response to destroy the virus or virus
    infected cell.

119
CD4 Immuno-adhesion Fusion Protein
120
HIV Therapeutic Agents
  • Another strategy involves making a second fusion
    protein.
  • The CD4 sequence is ligated to the sequence of
    Pseudomonas exotoxin A to form a fusion protein.
  • HIV infected cells have gp120 proteins on their
    surfaces.
  • The CD4 portion of the fusion protein will attach
    to the infected cells.
  • The fusion protein will enter the cells and
    initiate the killing of the infected cell.
  • Pseudomonas exotoxin A inactivates the protein
    synthesis by affecting elongation factor EF-2.
    This prevents further protein synthesis and
    eventually causes death of the infected cell.

121
CD4-Pseudomonas Exotoxin Fusion Protein
About PowerShow.com