GENE GENE THERAPYTHERAPY

By Sam Lai and Meng LeeBy Sam Lai and Meng Lee

Gene TherapyGene Therapy

Introduction : What is it?Introduction : What is it? Gene Therapy : A Closer LookGene Therapy : A Closer Look How much did you learn?!How much did you learn?! Case Study : SCIDCase Study : SCID Model for Gene Therapy Medical Model for Gene Therapy Medical

FrameworkFramework Discussion / Q&ADiscussion / Q&A

What is it?What is it?

Gene therapyGene therapy, which was first conceived in , which was first conceived in the mid-1970s, aims to insert working copies the mid-1970s, aims to insert working copies of genes into cells containing dysfunctional of genes into cells containing dysfunctional ones ones

treat, cure, or ultimately prevent disease by treat, cure, or ultimately prevent disease by changing the expression of a person's genes changing the expression of a person's genes

current gene therapy is primarily current gene therapy is primarily experimental, with most human clinical trials experimental, with most human clinical trials only in the research stages only in the research stages

Most often in context of treating lethal and Most often in context of treating lethal and disabling diseases, potential also for disease disabling diseases, potential also for disease preventionprevention

Human Genome Human Genome ProjectProject A A genomegenome is all the DNA in an is all the DNA in an

organism, including its genes. Genes organism, including its genes. Genes carry information for making all the carry information for making all the proteins required by all organisms proteins required by all organisms

Variations in structure of person’s Variations in structure of person’s genes collectively helps define us as genes collectively helps define us as individualsindividuals

Rationale for GT is based on Rationale for GT is based on knowledge of the human genetic code knowledge of the human genetic code

Began formally in 1990, set as a 13 Began formally in 1990, set as a 13 year project. year project.

HGP GOALS HGP GOALS

Identify aproximately 30,000 genes Identify aproximately 30,000 genes Determine 3 billion chemical base Determine 3 billion chemical base

pairs that make up human DNApairs that make up human DNA Store information in databasesStore information in databases Improve tools for data analysisImprove tools for data analysis Address ethical, legal and social Address ethical, legal and social

issues that might arise from thisissues that might arise from this

HGP cont…HGP cont…

Achieve these goals, Achieve these goals, researchers look at researchers look at genetic makeup of genetic makeup of other organismsother organisms

This project is This project is important because important because the government's the government's dedication to the dedication to the transfer of transfer of technology to the technology to the private sector private sector

Which Cells Targeted?Which Cells Targeted?

somatic gene therapy the recipient's somatic gene therapy the recipient's genome is changed, but the change is genome is changed, but the change is not passed along to the next generation not passed along to the next generation

germline gene therapy, the sex cells are germline gene therapy, the sex cells are changed with the goal of passing these changed with the goal of passing these changes to their offspring. But, this is changes to their offspring. But, this is not being actively investigated, at least not being actively investigated, at least not humans, although a lot of discussion not humans, although a lot of discussion is being conducted about its value and is being conducted about its value and desirability. desirability.

Somatic Stem Cells Somatic Stem Cells

Somatic stem cells are remarkable Somatic stem cells are remarkable cells in the bodycells in the body

These different stem cell types are These different stem cell types are targets for gene therapytargets for gene therapy

Genetically treated stem cells, when Genetically treated stem cells, when reintroduced into the patient's body reintroduced into the patient's body are expected to naturally travel are expected to naturally travel through the blood stream to the bone through the blood stream to the bone marrow. marrow.

Germline Gene Germline Gene TherapyTherapy Gene therapy in germline cells has the Gene therapy in germline cells has the

potential to affect not only the individual, potential to affect not only the individual, but also their children as well. but also their children as well.

Any genetic changes in the reproductive Any genetic changes in the reproductive cells or changes made to the embryo cells or changes made to the embryo before the stage of differentiation, would before the stage of differentiation, would affect all future offspring of that person. affect all future offspring of that person. This makes an vital distinction, affecting This makes an vital distinction, affecting major ethcial issues major ethcial issues

Delivery of GenesDelivery of Genes

Need an efficient method to Need an efficient method to deliver the gene to live cells.deliver the gene to live cells.

Done via vectors (gene carriers), Done via vectors (gene carriers), delivering therapeutic genes to delivering therapeutic genes to cells - common vector is virusescells - common vector is viruses

Alternative delivery methods seen Alternative delivery methods seen with use of lipids and proteinswith use of lipids and proteins

Use of VirusesUse of Viruses

Viruses evolved a way of Viruses evolved a way of delivering their genes to human delivering their genes to human cells in pathogenic matter.cells in pathogenic matter.

Take advantage of this, Take advantage of this, manipulate genome to remove manipulate genome to remove disease genes and insert disease genes and insert therapeutic genestherapeutic genes

Risks with GT trialsRisks with GT trials

Viruses can usually infect more than Viruses can usually infect more than one type of cell. one type of cell.

When DNA is injected directly into a When DNA is injected directly into a tumor, there is a slight chance that tumor, there is a slight chance that this DNA could unintentionally be this DNA could unintentionally be introduced into reproductive cells.introduced into reproductive cells.

Other concerns include the possibility Other concerns include the possibility that transferred genes could be that transferred genes could be "overexpressed""overexpressed"

Add a new Add a new chromosome?chromosome? Experimentation seen with Experimentation seen with

introduction of 47introduction of 47thth chromosome chromosome Exist along 46Exist along 46thth chromosome, chromosome,

large vector capable carrying large vector capable carrying genetic code, that hopefully the genetic code, that hopefully the immune system would not attackimmune system would not attack

Understanding? Understanding?

Scientists know little about Scientists know little about function of the thousands of function of the thousands of genes. Attempting therapy genes. Attempting therapy without this knowledge would without this knowledge would address few genes of a particular address few genes of a particular diseasedisease

i.e. Sickle Cell Anemiai.e. Sickle Cell Anemia

Sickle Cell AnemiaSickle Cell Anemia

Caused by error in gene that Caused by error in gene that informs our body on how to make informs our body on how to make hemoglobinhemoglobin

Prevalent in African AmericansPrevalent in African Americans However deadly the error is, this However deadly the error is, this

increased the survival rate for increased the survival rate for those who also had malaria in the those who also had malaria in the regionregion

Hurdles… Hurdles…

Most genetic disorders involve Most genetic disorders involve more than one gene, only few more than one gene, only few genetic diseases involve merely genetic diseases involve merely oneone

This multigene disorders also This multigene disorders also involve the environment, such as involve the environment, such as diet, exercise, smoking, etc.diet, exercise, smoking, etc.

Everything has a priceEverything has a price

High costs associated with High costs associated with developing this technology, and developing this technology, and regulations that needed to be regulations that needed to be implied on it with implied on it with experimentations are great experimentations are great hurdles for experimenters in this hurdles for experimenters in this field.field.

First Human Gene First Human Gene Therapy attemptTherapy attempt Began in 1990, using Began in 1990, using ex vivoex vivo

strategy, where patient cells were strategy, where patient cells were cultivated in laboratory and cultivated in laboratory and incubated with vectorsincubated with vectors

transplanted back into the patienttransplanted back into the patient Attempted to treat 2 genetic Attempted to treat 2 genetic

disorders, including children with disorders, including children with immune defiency as well as people immune defiency as well as people with high levels of serum cholesterolwith high levels of serum cholesterol

First Human GT cont…First Human GT cont…

Practical approaches, delivering Practical approaches, delivering genes based on so-called genes based on so-called in vivoin vivo GT where viruses are directly GT where viruses are directly given to patientsgiven to patients

First model was dependent on a First model was dependent on a version of adenovirus to treat version of adenovirus to treat cystic fibrosiscystic fibrosis

GT on Cancer GT on Cancer TreatmentTreatment Researchers are working to improve Researchers are working to improve

the body's natural ability to fight the the body's natural ability to fight the disease or to make the cancer cells disease or to make the cancer cells more sensitive to other kinds of more sensitive to other kinds of treatment, such as chemotherapy treatment, such as chemotherapy

Substitution of a "working" copy of a Substitution of a "working" copy of a gene for an inactive or defective gene for an inactive or defective gene. gene.

GT on Cancer cont…GT on Cancer cont…

Injection of cancer cells with a gene Injection of cancer cells with a gene that makes them more sensitive to that makes them more sensitive to treatment with an anticancer drug. treatment with an anticancer drug.

Introduction of the multidrug Introduction of the multidrug resistance gene into stem cells. The resistance gene into stem cells. The MDR gene is used to make the stem MDR gene is used to make the stem cells more resistant to the side cells more resistant to the side effects of the high doses of effects of the high doses of anticancer drugs. anticancer drugs.

Hurdles SummaryHurdles Summary

There are many obstacles that There are many obstacles that prevent researchers and scientist prevent researchers and scientist from developing successful gene from developing successful gene therapy techniques.therapy techniques.

The issues being confronted are The issues being confronted are the same ones that are faced the same ones that are faced whenever a powerful new whenever a powerful new technology is developed. technology is developed.

When All is Said…When All is Said…

A proposed gene therapy trial, or A proposed gene therapy trial, or protocol, must be approved by at protocol, must be approved by at least two review boards at the least two review boards at the scientists' institution. scientists' institution.

Any studies involving humans Any studies involving humans must be reviewed with great care. must be reviewed with great care.

CASE STUDY: SCIDCASE STUDY: SCID SCID = SCID = SSevere evere CCombined ombined IImmunommunoddeficiencyeficiency

What is SCID?What is SCID?

SCID patients can neitherSCID patients can neither– Construct cell-mediated immune Construct cell-mediated immune

responseresponse– Make AntibodiesMake Antibodies

Patients do not die of SCID itselfPatients do not die of SCID itself More Boys than GirlsMore Boys than Girls

SCID Cases, Past & SCID Cases, Past & PresentPresent Not discovered until early Not discovered until early

1960s1960s Occur in 1 out of 1.000,000Occur in 1 out of 1.000,000 ““Bubble Boy” – David Bubble Boy” – David

VetterVetterSpent 12 years in Texas Hospital Spent 12 years in Texas Hospital Sterile TentSterile Tent

Usually not discovered until Usually not discovered until too latetoo late

Science Behind SCID Science Behind SCID (1)(1)

What Happens in SCIDWhat Happens in SCID Lymphocyte T & B cells do not get Lymphocyte T & B cells do not get

developeddeveloped– Normal catabolism of purines Normal catabolism of purines

deficientdeficient Body lack messenger to identify Body lack messenger to identify

foreign bodiesforeign bodies Cannot initiate immune responseCannot initiate immune response

Science Behind SCID Science Behind SCID (2)(2)

What Caused SCID?What Caused SCID? ADA (ADA (AAdenosine denosine DDeamineaminaase) se)

enzyme deficiencyenzyme deficiency– Autosomal recessive inheritance of Autosomal recessive inheritance of

genes coding for ADA (25%)genes coding for ADA (25%) Cannot Make T cellsCannot Make T cells

– Spontaneous Mutation of IL-7 GeneSpontaneous Mutation of IL-7 Gene

Science Behind SCID Science Behind SCID (3)(3)

Science Behind SCID Science Behind SCID (4)(4)

Possible TherapiesPossible Therapies

Gem free tent (life long)Gem free tent (life long) Regular injections of PEG-ADA Regular injections of PEG-ADA Bone Marrow TransplantBone Marrow Transplant Gene TherapyGene Therapy

GT Curing SCID GT Curing SCID (1)(1)

How mutated genes were How mutated genes were discovered?discovered?

Late 1970s – understood Late 1970s – understood mechanism for immune systemmechanism for immune system

Match SCID to missing enzymeMatch SCID to missing enzyme Brute force / luckBrute force / luck 1983 – ADA cDNA identified & 1983 – ADA cDNA identified &

clonedcloned

GT Curing SCID GT Curing SCID (2)(2)

How mutations are correctedHow mutations are corrected Recombinant DNA technologies!!!Recombinant DNA technologies!!! Gene SplicingGene Splicing Insertion of correct gene into Insertion of correct gene into

retrovirus vectorretrovirus vector Separate & MultiplySeparate & Multiply Insert into patientInsert into patient

GT Curing SCID GT Curing SCID (3)(3)

How to decide on delivery mechanism?How to decide on delivery mechanism? Goals:Goals:

– Must take up long-term residence in patientMust take up long-term residence in patient– Must be expressed adequatelyMust be expressed adequately

Methods:Methods:– 1990 – use patient’s own T cells (ADA)1990 – use patient’s own T cells (ADA)– 1993 – use blood stem cells (ADA)1993 – use blood stem cells (ADA)– 1999 – use blood stem cells (X-linked IL-7)1999 – use blood stem cells (X-linked IL-7)

GT Curing SCID GT Curing SCID (4)(4)

Gene Therapy SuccessesGene Therapy Successes So far approximately 80% So far approximately 80%

success ratesuccess rate Restoration of normal cellular Restoration of normal cellular

immunity in patientsimmunity in patients Blood Stem Cells Method done on Blood Stem Cells Method done on

an increasing scalean increasing scale

SCID Cure AnalysisSCID Cure Analysis

Why GT works in SCID?Why GT works in SCID? Defect at a single gene locusDefect at a single gene locus Genes identified & clonedGenes identified & cloned Undergo irradiation or Undergo irradiation or

immunosuppressive immunosuppressive chemotherapychemotherapy

Treatment of young childrenTreatment of young children

Discussion of Ethical, Discussion of Ethical, Legal & Social IssuesLegal & Social Issues Many issues & concerns, little Many issues & concerns, little

answersanswers Real life solutions come from idea Real life solutions come from idea

brainstormsbrainstorms

Today: Sample MedicalToday: Sample Medical

System FrameworkSystem Framework

Current DevelopmentCurrent Development

Signs of DevelopmentSigns of Development– State Laws & Federal Bills which State Laws & Federal Bills which

prohibits discrimination based on prohibits discrimination based on genetic informationgenetic information

– Special committee reviewing gene Special committee reviewing gene therapy (NIH + FDA)therapy (NIH + FDA)

– 3-5% of all funds for genetics studies 3-5% of all funds for genetics studies must be used for investigation of must be used for investigation of such issuessuch issues

Targeted IssuesTargeted Issues

Regulation of Gene TherapyRegulation of Gene Therapy– Assurance of Quality of TreatmentAssurance of Quality of Treatment– Targeted TreatmentTargeted Treatment

Disease Treatment vs. EnhancementDisease Treatment vs. Enhancement Only Disease TreatmentOnly Disease Treatment

Fair & Readily Available TreatmentFair & Readily Available Treatment– Same Treatment for everyoneSame Treatment for everyone– At an affordable priceAt an affordable price

Protection of Genetic InformationProtection of Genetic Information

AssumptionsAssumptions

Possible to isolate and provide Possible to isolate and provide treatment only for disease alleles treatment only for disease alleles without committing enhancementwithout committing enhancement

Development in medical Development in medical technologies will make medication technologies will make medication cheaper in the long runcheaper in the long run

Model applies for a closed country Model applies for a closed country onlyonly

Model PhilosophyModel Philosophy

Possession of genetic information Possession of genetic information causes many problemscauses many problems

Must have a tightly regulated Must have a tightly regulated system in place (multi-level, multi-system in place (multi-level, multi-group)group)

ProposalProposal Central Gene Therapy Monitoring Central Gene Therapy Monitoring

AdministrationAdministration

Structure of Medical Structure of Medical SystemSystem 3 Levels, 5 Groups3 Levels, 5 Groups

Government:Government: CGTMACGTMA Review CommitteeReview Committee

Practitioners:Practitioners: DoctorsDoctors Gene TherapeuticsGene Therapeutics

Patients:Patients: PatientsPatients

Patient Treatment Patient Treatment Process Process (1)(1)

7 Steps7 Steps1.1. Disease IdentificationDisease Identification

1.1 Doctor Identifies Genetic Problem1.1 Doctor Identifies Genetic Problem

2.2. Application for TreatmentApplication for Treatment2.1 Doctor Submit Application2.1 Doctor Submit Application

3.3. Treatment ApprovalTreatment Approval3.1 CGTMA Reviews Application3.1 CGTMA Reviews Application

Patient Treatment Patient Treatment Process Process (2)(2)

4.4. Preparation of Delivery MaterialPreparation of Delivery Material4.1 Gene Therapeutics cure the disease 4.1 Gene Therapeutics cure the disease genes, deliver to patient’s stem cellgenes, deliver to patient’s stem cell

5.5. Confirmation of Appropriate Confirmation of Appropriate ChangesChanges5.1 CGTMA confirms for appropriate changes5.1 CGTMA confirms for appropriate changes

6.6. Gene TherapyGene Therapy6.1 Doctor conducts Gene Therapy to Patient6.1 Doctor conducts Gene Therapy to Patient

Patient Treatment Patient Treatment Process Process (3)(3)

7.7. CheckupCheckup7.1 Confirm patients received only approved 7.1 Confirm patients received only approved treatment (by CGTMA)treatment (by CGTMA)

Groups Responsibility Groups Responsibility (1)(1)

CGTMACGTMA– Check validity of genetic treatment Check validity of genetic treatment

(i.e. only targeting disease genes)(i.e. only targeting disease genes)– Check for appropriate preparation of Check for appropriate preparation of

genetic material for gene therapygenetic material for gene therapy– Monitor Treatment by DoctorMonitor Treatment by Doctor

Review CommitteeReview Committee– Determine disease genes vs. Determine disease genes vs.

enhancement genesenhancement genes

Groups Responsibility Groups Responsibility (2)(2)

DoctorsDoctors– Identifying DiseaseIdentifying Disease– Submitting Application for Gene TherapySubmitting Application for Gene Therapy– Conducting Gene TherapyConducting Gene Therapy

Gene TherapeuticsGene Therapeutics– Manipulate genes based on applicationManipulate genes based on application

Both group faces penalty for illegal practicesBoth group faces penalty for illegal practices

Important FactorsImportant Factors

Must have good internal and Must have good internal and external monitoring by each external monitoring by each groupgroup

Must be aware and implement Must be aware and implement policy for patient’s privacy rightspolicy for patient’s privacy rights

Education of the general publicEducation of the general public

Discussion + Q&ADiscussion + Q&A

How model answers targeted How model answers targeted issuesissues

Flaws with the modelsFlaws with the models DiscussionDiscussion Additional Q&AAdditional Q&A

End (Yeah finally…)End (Yeah finally…)

Thanks for your patience !Thanks for your patience !