OVERVIEW THERAPY OF GENETIC

DISORDERSHendrik Sutopo

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Current Therapy of Genetic Disorders

Preventive Metabolic Manipulation Gene Product Replacement Cell or Organ Transplantation Somatic Gene Therapy

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Therapy of Genetic Disorders Preventive Therapy

Prenatal diagnosis Preimplantation diagnosisPreventive screening for disease onset

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Therapy of Genetic Disorders

Metabolic ManipulationDietary restriction

○ Lactose restriction for Lactase deficiency; phenylalanine restriction for PKU

Dietary Supplementation ○ Vitamin C for Scurvy, Biotin for Biotinidase deficiency, Starch for G-

6-P deficiency

Chelation and enhanced excretion○ copper chelation for Wilson Disease

Metabolic inhibitors○ allopurinol for gout, Statins for hypercholesterolemia

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Therapy of Genetic Disorders Gene Product Therapy

Hormone, protein or enzyme replacement○ Hormone supplementation:

Hypothyroidism: thyroid Congenital adrenal hyperplasia: cortisolGrowth hormone

○ Hemophilia; clotting factors ○ Diabetes: insulin ○ Enzyme replacement

Beta glucosidase : GauchersAlpha glucosidase: PompeAdenosine deaminase (PEG): ADA- SCID

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Somatic Gene TherapyIntroduction of recombinant genes into somatic cells

to treat genetic or acquired disease• applicable to any disease with molecular basis of

pathogenesis

• currently does not involve removal, repair or site-specific replacement of mutant genes

• need repetitive therapy

• All gene therapy so far in people has been directed at somatic cells

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The Beginning… In the 1980s, Scientists began to look into gene

therapy.

They inserted human genes into a bacteria cell.

Then the bacteria cell would transcribe and translate the information into a protein

Then they would introduce the protein into human cells

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The First Case The first gene therapy was performed on

September 14th, 1990Ashanti DeSilva was treated for SCID

○ Sever combined immunodeficiency

Doctors removed her WBC○ inserted the missing gene into the WBC, then○ put them back into her blood stream.

This strengthened her immune systemworked for a few months

Real treatments performed with retroviral system

Severe Combined Immunodoficiency (SCID)

Mutation on Chromosome 20 is often to blame

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10http://encarta.msn.com/media_461561269/Gene_Therapy.html

How It Works

Real treatments performed with retroviral system

Problems:• not cure of the disease• maintenance of venous access to administer the therapy• shortage• cost• requirement of frequent, repeated administrations• allergic, inflammatory and immune responses to the

infused materials• • …

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Future Treatments

Stem Cells

Therapeutic Cloning

Advanced IVF Techniques

Gene Therapies

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“If your ship doesn’t come in, swim out to it”

Jonathan Winters

The future is here

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..Adult Stem Cells

•Stem cell collected from adult can be harvested from many area including the bone marrow.

•Alternative to Embryonic Stem cells

•Potential to reverse and cure Diabetes

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..Embryonic Stem Cells•Use undifferentiated cell from embryos and cultures them to grow into need cells

•Neurons Grown from Embryonic Stem Cells Restore Function in Paralyzed Rats

•Hold potential cures for 1000s of diseases many genetic disorders.

•Many ethical and social concerns surrounding this research

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..Therapeutic Cloning

•Using stem cells to replace or create tissues and organs

•Currently heart tissues and full bladders are being grow in lab

Fig. Stem cell treatments and tissues recreated in the heart of a child

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Advanced IVF Techniques

•This treatment is aimed at women who would pass on a genetic defect to the child.

•Also helps women who suffer with mitochondria disease.

•Faulty genes are removed from the embryo, and replaced by healthy genes from the additional woman.

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Ethical Issues

Who decides what diseases to cure?

Who will have access to therapy?

Is it interfering with God’s plan?

Is it alright to use the therapy in the prenatal stage of development in babies?

Courtesy of www.cbs.dtu.dk

GENE THERAPY

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all Inherited and acquired disorders

cancer

AIDS/HIV

Goal of gene therapy

Management and correction of human diseases

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The Bubble Boy In 2002, then 18-month-

old Rhys Evans received one of the first successful gene therapy treatments for a genetic disorder, which cured his severe combined immunodeficiency (SCID).

Courtesy of news.bbc.co.uk

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Major Advancements

2002- Scientists are able cure children of SCID. 2003- Researchers are able to insert genes to

the brain, opening up a wider variety of diseases that could be cured.

2006- Successfully treat two cancer patients.

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Gene therapy could be very different for different diseases• Gene transplantation (to patient with gene deletion)

• Gene correction (To revert specific mutation in the gene of interest)

• Gene augmentation (to enhance expression of gene of interest)

• Change the regulation of gene repairs

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Target sites for gene therapy

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Gene Transfer

Transcription(nucleases)

Exogenous DNA+ vector (viral)

Cytosol

Endosome

Lysosome

Protein expression

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Vectors in gene transfer: Viruses

Retroviruses

Adenoviruses

Adeno-associated viruses

Envelope protein pseudotyping of viral vectors

Non-viral methods

Naked DNA

Oligonucleotides

Lipoplexes and polyplexes

Hybrid methods

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Retrovirus Engineering

From: Alberts et al. Molecular Biology of the Cell

The Gene Therapy Process

1. A desired gene is selected and inserted into a genome to replace an “abnormal”, disease-causing gene.

2. The genome is then transferred into a vector, most commonly an adenovirus, which will transport the gene into the patient.

3. The vector is sent to a target cell in the patient’s genome and then “unloads” the genetic material in the virus.

4. Once the genetic material has been inserted into the target cell, the cell will continue its reproductive cycle with the new therapeutic gene . This will cause new generations of cells with the integral therapeutic gene which will cure the desired disease in the patient.

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Non viral vectors

Un complexed plasmid DNA

DNA coated gold particles

Liposomes

DNA – protein conjugates

Injections of naked DNA

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Gene Transfer techniques

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Problems with Gene Therapy

Difficult to integrate desired DNA into a genome. Effects are usually temporary Immune system automatically attacks foreign objects reduce

effects of gene therapy. The possibility of the modified adenovirus to revert back to its

harmful state. In rare cases therapy has induced tumors leukemia (if integrated

in a tumor suppressor gene because insertional mutagenesis)

Multigene Disorders Heart disease, Hypertension, Alzheimer’s, arthritis, diabetes : hard to treat

Until today : Efficacy in any gene therapy protocol not definitive.

Problems with Gene Therapy

Economic : Funding for therapy fluctuates with

rise and fall of success. Most funding in government

research, + $400 million a year. Difficult to afford and can’t be

covered by insurance. Economic market : something new?

Ethic? Law?

Courtesy of dir.nichd.nih.gov

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Current Status FDA hasn’t approved any human gene therapy productsamples: 18-year-old Jesse Gelsinger died from multiple organ

failure 4 days after treatment Death was triggered by severe immune response to adenovirus carrier

January 2003, halt to using retrovirus vectors in blood stem cells because children developed leukemia-like condition after successful treatment for X-linked SCID

Inadequate understanding of biological interactions of vector and host.

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The Future treatment for genetic disorders is Experimental (incld. Gene Therapy)

It is not currently available outside a clinical trials

Current Status

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Thank You

QUESTIONS ??