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ETHICAL AND SAFETY ISSUES IN GENE TRANSFER

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Title: ETHICAL AND SAFETY ISSUES IN GENE TRANSFER


1
ETHICAL AND SAFETY ISSUES IN GENE TRANSFER
  • David Jay Weber, M.D., M.P.H.
  • Professor of Medicine, Pediatrics Epidemiology
  • Epidemiologist, GCRC
  • University of North Carolina at Chapel Hill

2
ACKOWLEDEGMENTS
  • Special thanks to the following for kindly
    sharing their slides
  • John Wiley and Sons
  • Dr. Martin Evans, Professor University of
    Kentucky Medical Center

3
INFECTION CONTROL
  • Charge
  • Prevent patient-to-patient, patient-to-staff,
    staff-to-patient transmission laboratory worker
    acquisition
  • Biologically active agents
  • BCG Used for bladder fulguration risk
    mycobacteriosis
  • Non-sterile pharmaceuticals
  • Blood (gt20 agents transmitted by needlestick),
    organs/tissue, leeches, other (e.g., human growth
    home risk CJD)
  • Sterile pharmaceuticals
  • Most drugs risk intrinsic or extrinsic
    contamination

4
INFECTION CONTROL
  • Surveillance (Comprehensive)
  • Outbreak investigations
  • Policies/procedures (gt70 policies)
  • Education (Every employee, every year)
  • Provision of personal protective equipment
  • Infection control rounds (assure compliance)
  • Monitoring Environment, equipment
  • Occupational health

5
PERSON-TO-PERSON ACQUISITION
Weber D, Rutala W. CID 200132446.
6
LECTURE TOPICS
  • Basics of gene transfer (gene therapy)
  • Scope of gene therapy trials
  • Ethical and safety issues
  • Infection control and laboratory safety issues

7
HUMAN EXPERIMENTATION CHALLENGES FOR THE 21ST
CENTURY
  • Current
  • Gene transfer
  • Near future
  • Xenotransplantation, biological and chemical
    agents of terrorism, cloning (reproductive,
    therapeutic), genetic screening, in utero gene
    transfer, stem cell transplantation
  • More distant future
  • Nanotechnology, life prolonging therapy (drugs
    altering program cell death)

8
GENE TRANSFER COMPONENTS
  • Gene transfer products
  • Gene(s) encoding the therapeutic protein
  • Vector that delivers gene into the cells
  • Vectors
  • Viral (e.g., retroviruses, adenoviruses)
  • Non-viral (e.g., naked DNA)
  • Cellular (e.g., allogenic, xenogenic, or
    autologous cells)

9
STRATEGY OF GENE TRANSFER
Virus
VG 1
VG 2
VG 3
TG
Insert Transgene
Infect Host
10
EX VIVO GENE TRANSFER
11
IN VIVO GENE TRANSFER
12
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13
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14
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15
STRATEGIES FOR USE OF GENE THERAPY TRANSFER
  • Supplementation
  • Transfer a functional gene into cells that have a
    defective gene
  • Example Transfer gene that produces factor IX
  • Immunotherapy
  • Deliver a gene that will elicit an immune
    response when the gene product is expressed
  • Example Infect with vaccinia containing
    prostate-specific antigen gene

16
STRATEGIES FOR USE OF GENE THERAPY TRANSFER
  • Cancer therapy
  • Deliver a therapeutic gene into cancer cell
  • Example Infect cancer cells with adenovirus
    containing the gene for tumor necrosis factor
  • Chemoprotection
  • Transfer of a gene for drug resistance into
    normal cells to protect them from chemotherapy
  • Example Transfer a multi-drug resistance gene
    into normal bone marrow cells transplant the
    cells and administer chemotherapy to kill
    unprotected tumor cells

17
STRATEGIES FOR USE OF GENE THERAPY TRANSFER
  • Ablative therapy
  • Deliver a gene that will allow activation of a
    prodrug leading to cell death
  • Example Insert the herpes simplex virus
    thymidine kinase gene into tumor cells and
    administer ganciclovir
  • Antiviral therapy
  • Deliver a gene into infected cells that
    interferes with viral replication
  • Transfer a gene for hairpin ribozyme, which
    cleaves HIV-1 RNA in HIV-infected T cells

18
STRATEGIES FOR USE OF GENE THERAPY TRANSFER
  • Marking
  • Insert a gene into cells to identify them when
    the gene is expressed
  • Example Infect harvested bone marrow cells with
    a retrovirus containing neomycin
    phosphotransferase gene after transplantation,
    look for cells producing the enzyme as evidence
    of engraftment

19
SCOPE OF GENE TRANSFER TRIALS
20
HUMAN DISEASES TARGETED FOR GENE TRANSFER
  • Monogenic diseases
  • Adenosine deaminase severe immunodeficiency
  • X-linked severe combined immunodeficiency
  • Cystic fibrosis
  • Hemophilia B
  • Chronic granulomatous disease
  • Thalassemia
  • Sickle-cell anemia
  • Cancers
  • Head and neck
  • Glioblastoma
  • Lung
  • Breast
  • Liver
  • Colon
  • Prostate
  • Cervix, ovary
  • Hematologic

21
HUMAN DISEASES TARGETED FOR GENE TRANSFER
  • Infectious diseases
  • Hepatitis B infection
  • Influenza infection
  • HIV
  • Herpes virus infection
  • CMV
  • Other
  • Coronary artery disease
  • Peripheral artery disease
  • Amyotrophic lateral sclerosis
  • Rheumatoid arthritis

22
CLINICAL TRIALSPROTOCOLS
23
CLINICAL TRIALSPATIENTS
24
ETHICAL AND SAFETY ISSUES
25
OVERSIGHT OF GENE TRANSFER
FDA CBER
NIH/OBA RAC
Gene Transfer Safety Assessment Board
Principal Investigator
Institutional Biosafety Committee (IBC)
Institutional Review Board (IRB)
Infection Control Committee
26
SAFETY ISSUES PATIENT
  • Administration risks (e.g., bleeding,
    anaphylaxis)
  • Risks due to vector
  • Infection due to replication competent virus
  • Inflammatory response
  • Cancer (e.g., activation of oncogene)
  • Injury to healthy cells or tissue

27
SAFETY ISSUES INFECTION CONTROL
  • Vector production Laboratory workers
  • Vector transport Transportation personnel
  • Vector administration Healthcare workers
  • Post-administration care Healthcare workers,
    contacts

28
ADVERSE EVENTS
  • Death Pennsylvania, 1999
  • Disease Partial ornithine transcarbamylase
    (OTC) defiency
  • Benefit None demonstrated
  • AER Death
  • Mechanism Inflammatory reaction to adenovirus
    vector injected into hepatic artery

29
ADVERSE EVENTS
  • Cancer France, 2002
  • Disease Severe combined immunodeficiency
    disorder (SCID)-XI (caused by mutations in
    X-linked gene IL2RG that encodes ?chain of the
    lymphocyte receptors for IL-2
  • Benefit Immune recovery in gt90 of treated
    infants
  • AE 2 children have developed T-cell leukemia
    (gt1 year after gene therapy)
  • Mechanism Insertion of vector in chromosome in
    or near gene LM02 (insertion mutagenesis)

30
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31
ASSESSING RISK
  • Principle Development can proceed using drug
    and vaccine approach
  • History Extrapolation of no observed effect
    level (NOEL) and maximally tolerated dose (MTD)
    has been based on animal experiments
  • Issue For gene therapy with human pathogens
    (e.g., adenovirus) animal data may not be
    relevant

32
ASSESSING RISK
  • Principle Level of toxicity is proportional
    to the gene transfer or that toxicity and
    administration dosage are at least in a constant
    relation
  • In pharmacology, this principle is generally
    valid and is limited only by some mainly
    genetically based individual pre-dispositions
    that are statistically of low frequency
  • In gene therapy the above may not be true. For
    example, 5 of the population are not immunized
    to Ad type 5. Such people may have an extremely
    divergent immunological pre-disposition.

33
LOCAL GENE TRANSFER REVIEW COMMITTEES
  • Standard IRB membership
  • Community advocate
  • Epidemiologists, statisticians
  • Physicians, scientists
  • Expert(s) in gene therapy
  • Infection control, laboratory safety
  • Vector expert (high level of technical expertise
    required)
  • Animal model expert
  • Disease specialist (Limited choices if disease is
    rare)

34
KEY ISSUES TO REVIEW
  • Benefits to the patient (if any)
  • Risks to the patient
  • Benefits to society
  • Risks to society
  • Informed consent
  • Benefits not over emphasized
  • Risks not minimized

35
KEY ISSUES TO REVIEW
  • Vector production
  • Specific vector
  • Replication competence (i.e., genes deleted)
  • Virulence
  • Susceptible cells
  • Site of genome integration
  • Adventitial material
  • Gene(s) inserted
  • Laboratory safety

36
KEY ISSUES TO REVIEW
  • Method of delivery
  • In vivo versus ex vivo
  • Source of target cells
  • Route (e.g., inhalation, injection, etc.)
  • Number of administrations
  • Precautions to prevent exposure to healthcare
    workers

37
KEY ISSUES TO REVIEW
  • Study design
  • Trial phase
  • Clear hypothesis
  • Patient selection (minimize risks, therapy
    warranted)
  • Adequate sample size
  • Appropriate outcome measures
  • Appropriate safety monitoring
  • Adequate duration of monitoring

38
KEY ISSUES TO REVIEW
  • Previous studies
  • Animal studies
  • Appropriate animals
  • Appropriate doses
  • Sufficient numbers
  • Safety analysis (e.g., pathology of organs)
  • Adequate analysis of adverse events
  • Human studies
  • Appropriate doses
  • Sufficient number
  • Adequate analysis of adverse events

39
INFECTION CONTROL
  • MANAGING RISKS TO HEALTHCARE WORKERS, LABORATORY
    PERSONNEL, AND PATIENT CONTACTS

40
GENE TRANSFER HOSPITAL CARE
  • Isolation precautions
  • Standard
  • Airborne?, droplet?, contact?
  • Visitor guidelines
  • Travel outside research/hospital room
  • Disinfection Surfaces, equipment
  • Restrictions on HCWs

41
GENE TRANSFER HOSPITAL CARE
  • Laboratory testing risks
  • Percutaneous injury (bloodborne vector)
  • Aerosolization (body secretions containing
    vector)
  • Monitoring
  • Research subject/patient
  • Medical staff
  • Environment
  • Household contact (visitor)

42
INFECTION CONTROL ISSUES
  • Replication competency of vector
  • Method of vector administration
  • Ability of vector to integrate into host genome
  • Ability of vector to establish latent or long
    lived infection
  • Mode of transmission (i.e., contact, droplet,
    airborne)
  • Infectivity (communicability)
  • Environmental survival of vector
  • Susceptibility to disinfectants

43
LIMITATIONS OF RECOMMENDATIONS
  • Limited data published on which to base
    recommendations
  • Data often considered proprietary
  • Focus on efficacy not potential infection control
    problems
  • Limitations of data obtained from current trials
  • Small number of patients in current trials
  • Highly selected patients
  • Special handling of vectors
  • Few phase III trials
  • Major problem difficulty of assessing rare
    events

44
BASIS OF INFECTION CONTROL RECOMMENDATIONS
  • Infection control recommendations based on
    microbiology and epidemiology of vector used in
    gene therapy protocol
  • Recommendations altered after scientific studies
    provide data to liberalize or alter
    recommendations

45
GENERAL RECOMMENDATIONS
  • Laboratory
  • Manage vector as per biosafety guidelines (NIH)
  • Research personnel should use appropriate
    personnel protective equipment (PPE)
  • Dispose of vectors and contaminated material as
    infectious waste
  • Decontamination using EPA registered disinfectant
  • Pharmacy
  • As per laboratory

46
GENERAL RECOMMENDATIONS
  • Patient management
  • Isolation precautions based on vector, mode of
    transmission, and risk of transmission
  • Manage all patients using Standard Precautions
    (PPE to prevent contact with all secretions and
    excretions except sweat)
  • Healthcare workers should use appropriate PPE
  • Avoid sharps injuries

47
CDC ISOLATION PRECAUTIONS
48
GENERAL RECOMMENDATIONS
  • Healthcare workers
  • Appropriate training in use of PPE
  • May require screening and restriction
  • Example Do not allow HCW with possible
    adenovirus infection to work with patient
    receiving aerosolized adenovirus vector
  • Protocol for dealing with sharp injuries

49
SPECIFIC RECOMMENDATIONS
50
NIH BIOHAZARDOUS AGENTS AND GENE TRANSFER VECTORS
  • Risk group 1 Not associated with human disease
  • Adeno-associated virus, murine leukemia virus
  • Risk group 2 Associated with human disease which
    is rarely serious and for which therapeutic or
    preventative interventions are often available
  • Adenovirus, poxviruses, herpes viruses,
    laboratory attenuated strains of vesicular
    stomatitis virus

51
NIH BIOHAZARDOUS AGENTS AND GENE TRANSFER VECTORS
  • Risk group 3 Associated with serious or lethal
    human disease for which therapeutic or
    preventative interventions may be available (high
    individual but low community risk)
  • Retroviruses (HTLV, HIV, SIV), Semliki forest
    virus
  • Risk group 4 Likely to cause serious or lethal
    human disease for which therapeutic or
    preventative interventions are not usually
    available (high individual and high community
    risk)
  • Ebola

52
PERSONAL PROTECTIVE EQUIPMENT
  • Use gloves that protect against viruses
  • Use handwashing agents effective against viruses
  • Alcohol not effective against non-enveloped
    viruses
  • Prevent mucous membrane exposure with masks and
    when necessary eye protection
  • Minimize risks of sharp injuries

53
DISINFECTION
  • Use appropriate disinfectant (EPA or FDA cleared)
  • Use appropriate use dilution and contact time
  • Thorough cleaning prior to disinfection critical
  • Efficacy depends on microbe (hydrophobic viruses
    less susceptible to disinfectants)
  • Hydrophobic viruses Coxsackie B1, polio virus 1
  • Lipophilic viruses Herpes viruses, vaccinia

54
DISINFECTANTS
55
ETHICL AND SAFETY ISSUESCONCLUSIONS
  • Risks and benefits of gene therapy unclear
  • Review of proposals requires a committee with
    expertise in vector production, disease to be
    studied, animal experimentation, infection
    control and laboratory safety
  • Better access to adverse events associated with
    clinical trials subdivided by transgene, vector,
    disease, delivery method is critical

56
INFECTION CONTROLCONCLUSIONS
  • Recommendations based on vector, route of
    transmission, environmental survival
  • Recommendations limited by lack of published data
    on vector survival, persistence of vector, risk
    of transmission, and risk of development of
    replication competent vector
  • Risk of wide spread use of gene therapy unknown
    since use confined to research trials (highly
    selected patients, research pharmacies, therapy
    in research units)

57
SPECIFIC RECOMMENDATIONSBY VECTOR
58
COMMON VECTORS
  • Adenoviruses
  • Retroviruses
  • Adeno-Associated viruses
  • Pox viruses
  • Herpes virus
  • Virus-like particles

59
VECTORS OF CONCERN
  • Replication competent
  • Or able to combine with endogenous virus leading
    to competency
  • Ability to establish latent infection
  • Able to integrate into host genome
  • Transmission via airborne/droplet or contact
    routes
  • High infectivity
  • Vector able to produce disease
  • Transgene potentially detrimental to normal host

60
RETROVIRUS EPIDEMIOLOGY
  • Murine retroviruses
  • Are not known to cause human disease
  • Are inactivated by human complement
  • Have a lipid envelope and do not withstand
    dessication
  • Lentiviruses (HIV) are bloodborne human pathogens

61
MURINE RETROVIRUSES
  • Advantages
  • Does not cause human disease
  • Elicits little host immune response
  • Transgenes may be expressed for life
  • Disadvantages
  • Oncogenic potential because integrates into the
    host genome
  • Inactivated by human complement
  • Must be given ex vivo
  • Only infects dividing cells

62
RECOMMENDATIONS FOR MURINE RETROVIRAL VECTORS
  • Standard Precautions
  • Manage blood spills with 110 final dilution of
    household bleach (like HIV or HBV)

63
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64
LENTIVIRUSES
  • Advantages
  • Can be given in vivo
  • Not inactivated by human complement
  • Infects dividing and non-dividing cells
  • Transgenes may be expressed for life
  • Disadvantages
  • Oncogenic potential because integrates into the
    host genome
  • May cause human disease

65
RECOMMENDATIONS FORLENTIVIRAL VECTORS
  • Standard Precautions
  • Avoid sharps injuries
  • Manage spills with 110 dilution of household
    bleach
  • Role of anti-retrovirals post-exposure?

66
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67
ADENOVIRUSES
  • Cause epidemic keratoconjunctivitis (pink eye),
    pharyngoconjunctival fever (head cold),
    gastroenteritis, acute hemorrhagic cystitis,
    pneumonia, meningoencephalitis
  • Mortality 18-20 in liver and kidney transplant,
    and 10-60 in BMT patients

68
ADENOVIRUS EPIDEMIOLOGY
  • Can be recovered from infected eyes for up to 14
    days, and in the stool of AIDS patients for up to
    2 years
  • Transmission by close personal contact
  • Attack rates in hospitals range from 16 to 50
    with up to 300 secondary cases

69
ADENOVIRUS
  • Advantages
  • Infects a wide variety of dividing and
    non-dividing cells
  • Little oncogenic potential because does not
    integrate into the host genome
  • Can carry larger transgenes
  • Disadvantages
  • Causes human disease
  • Host immune response may limit use

70
ADENOVIRUS INFECTION CONTROL ASPECTS
  • The viruses are extremely hardy
  • They persist on surfaces for up to 30 days
  • Are not eliminated by soap and water, ethanol,
    chlorhexidine gluconate
  • Quaternary ammonium compounds have variable
    efficacy

71
EARLY ADENOVIRUS VECTOR TRIALS
  • Low vector doses (105-109 pfu)
  • Patients hospitalized 2 days before receiving
    vector
  • Negative pressure isolation
  • Isolated until cultures for RCAs and vector were
    negative for 3 days

72
EXPERIENCE WITH ADENOVIRUS VECTORS
  • 12 trials involving more than 300 patients
  • Vectors with deletions in E1 and E3
  • Doses ranging from 105 to 1013 pfu
  • Multiple routes of administration
  • RCAs and vectors looked for with culture and PCR
    in most studies
  • --------------------------------------------------
    --------------------------------------------------
    ----------------------
  • No RCAs isolated in any study
  • Vector recovered in 5 studies

73
RECOMMENDATIONS FOR ADENOVIRAL VECTORS
  • Private room
  • Standard Precautions if inoculum lt1013 particles
  • Droplet Precautions if inoculum larger or for
    aerosol administration
  • Clean with quaternary ammonium compounds if data
    supports efficacy or 110 dilution of household
    bleach solution
  • Monitor RCA and vector shedding

74
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75
ADENO-ASSOCIATED VIRUS
  • Single stranded DNA parvovirus
  • Provirus integrated into the host-cell genome
  • Remains latent until helper virus supplies genes
    for replication
  • Helper viruses include adenovirus, herpesvirus,
    vaccinia

76
AAV EPIDEMIOLOGY
  • No known clinical illness
  • 80 of adults have antibody
  • Only isolated in patients with adenoviral
    infection
  • Presumed route of transmission is respiratory or
    gastrointestinal

77
ADENO-ASSOCIATED VIRUS
  • Advantages
  • Does not cause a known human disease
  • High rates of transduction of muscle, brain, and
    liver cells
  • May intercalate into the human genome at a
    predictable location
  • Disadvantages
  • Small size (can only carry genes up to 5 kb)
  • Oncogenic potential due to integration

78
RECOMMENDATIONS FOP AAV VECTORS
  • Same as those for adenovirus
  • Prevention of infections with helper viruses may
    be of value

79
Portrait of Edward Jenner (1749-1823)
Ann Intern Med 1997127635-42
80
ADVERSE REACTION RATES
Adapted from CDC.Vaccinia (smallpox vaccine)
recommendations of the ACIP, 2001. MMWR
200150(RR-10)
81
VACCINIA VIRUS
  • Advantages
  • Can carry large transgenes (lt25kb)
  • Genetically stable
  • Infect a wide variety of cell types
  • No oncogenic potential
  • Easy to store as a freeze-dried preparation
  • Disadvantages
  • Not engineered to be replication-incompetent
  • Many potential side effects
  • Less effects with an immune response

82
INFECTION CONTROL CONCERNS FOR VACCINIA VECTORS
  • A replication-competent virus
  • Shedding begins with appearance of the papule,
    reaches a maximum 4 to 14 days after inoculation,
    and persists until the lesion scabs over
  • Cross-transmission occurs by close personal
    contact

83
RECOMMENDATIONS FOR VACCINIA
  • Screen for susceptible close contacts
  • Young children, immunocompromised (HIV), pregnant
  • Immunize in a private room with Standard
    Precautions
  • Cover vaccination site with gauze and
    semipermeable transparent dressing
  • Consider immunization for healthcare workers

84
PRECAUTIONS BASED ON VECTOR AND ROUTE OF
ADMINISTRATION
Precautions A, airborne C, contact D, droplet
S, standard NA, not appicable
85
CONCLUSIONS
  • Recommendations based on vector, route of
    transmission, environmental survival
  • Recommendations limited by lack of published data
    on vector survival, persistence of vector, risk
    of transmission, and risk of development of
    replication competent vector
  • Risk of wide spread use of gene therapy unknown
    since use confined to research trials (highly
    selected patients, research pharmacies, therapy
    in research units)

86
REFERENCES
  • Weber DJ Rutala WA. Gene therapy. ICHE
    199920530-32.
  • Evans ME, et al. Clinical infection control in
    gene therapy A multidisciplinary conference.
    ICHE 200021659-73.
  • Evans ME Lesnaw JA. Infection control for gene
    therapy. CID 200235597-605.
  • Dettweiler U, Simon P. Points to consider for
    ethics committees in human gene therapy trials.
    Bioethics 200115number 5/6.
  • Preclinical evaluation of gene transfer products
    safety and immunologic aspects. Toxicology
    200217413-19.
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