A comprehensive overview of gene therapy with a special focus on transfusion medicine. This presentation by Dr. Abrar Kabir Shishir covers the history, types, strategies, and recent advancements in gene therapy, including CRISPR, ex vivo approaches, and applications in β-thalassemia and sickle cell disease. Essential for medical students, clinicians, and researchers in hematology and genetic medicine.

1. Good Morning…

2. Gene therapy
Dr. Abrar Kabir Shishir
MBBS, MD (Transfusion Medicine)

3. ❑There are over 6,000 known genetic disorders
around the globe.
❑Around 1 in 50 people are affected by a known
single-gene disorder.
❑Around 3% and 4% of Bangladeshi population are
carrier of β Thalassaemia and Hb E respectively.
INTRODUCTION
Pictures: Genetic disorders around the world

4. SOME GENETIC DISEASES

5. ❑ Medications
❑ Chemotherapy
❑ Blood transfusions
❑ Organ transplants
❑ Radiation therapies & Chemotherapies
❑ Surgery
TREATMENT OPTIONS
Picture: Different treatment options for
genetic diseases

6. New treatment
GENE THERAPY

7. GENE

8. ❑ Definition: Gene therapy is the introduction
of new genetic material into the cells of an
organism for therapeutic purposes.
GENE THERAPY
❑ Often, gene therapy works by adding new
copies of a gene that is broken, or by
replacing a defective or missing gene in a
patient’s cells with a healthy version of that
gene.

9. ❖ 1960s: Gene therapy was first conceptualized
❖ 14 September 1990: The first successful gene therapy
on 4 year old Ashanthi DeSilva for ADA-SCID
(Adenosine Deaminase Deficiency Severe Combined
Immunodeficiency).
HISTORY
Ashanthi DeSilva now
Ashanthi DeSilva in 1990

10. • 2003: The first commercial gene therapy, Gendicine, was approved in China for the
treatment of head and neck squamous cell carcinoma.
• 2011: Neovasculgen (Cambiogenplasmid – a gene therapy), was registered in
Russia for treatment of peripheral artery disease that delivers the gene encoding
for vascular endothelial growth factor (VEGF).
• August 17, 2022: FDA approved Zynteglo (Betibeglogene Autotemcel) for the
treatment of β thalassaemia
• December 08, 2023: FDA approved Casgevy (exagamglogene autotemcel) and
Lyfgenia (lovotibeglogene autotemcel) for the treatment of sickle cell disease
SOME COMMERCIAL GENE THERAPY

11. TYPES OF GENE THERAPY

12. SOMATIC VS GERM LINE
Topic Somatic cell gene therapy (SCGT) Germ line gene therapy (GGT)
1. Therapeutic genes transferred
into
Somatic cells (e.g., Blood cells, skin
cells etc.)
Germ cells during pre
implantation phase
2. Passes on to later generation No Yes
3. Technical difficulties Less More
4. Ethical problems Absent Present
5. Disadvantages Sometimes short lived, cells of most
tissue ultimately die and replaced by
new cells
May be deleterious and harmful,
with potential for unforeseen
effects on future generation
6. Use At present all researches directed to
correct genetic defects in somatic
cells
For safety, ethical and technical
reasons, it is not being attempted
at present

13. STRATEGIES OF GENE THERAPY
❑ Gene Augmentation Therapy (GAT) :
Addition of functional alleles. For diseases
caused by recessive gene, multiple genes or a
dominant gene.
❑ Targeted Killing of Specific Cells :
Suicidal genes (encoding toxic compounds) kill
specific cells of cancer.

14. ❑ Targeted Inhibition of Gene Expression:
Block the expression of any diseased gene.
Infectious diseases & some cancers.
STRATEGIES OF GENE THERAPY CONTD.
❑ Gene Editing:
This is a type of genetic engineering in
which a gene sequence is inserted,
deleted, modified or replaced in the DNA
of a living organism. Now done by
clustered regularly interspaced short
palindromic repeats (CRISPRs)

15. APPROACHES OF GENE THERAPY
A. In vivo gene therapy:
❑ Procedure:
• A Therapeutic gene is prepared in lab.
• Therapeutic gene is introduced into a vector.
• The vector is introduced to the patient
❑ This is done in:
• Cells which cannot be cultured in vitro.
• Re implantation of cultured cells is not efficient.
❑ Example:
• Brain,
• Retina etc.

16. B. Ex vivo gene therapy:
❑ Procedure:
• Therapeutic gene is prepared in lab.
• Therapeutic gene is introduced into a vector.
• Targeted cells are collected from the patient.
• Viral transduction in the lab.
• Transduced cells are introduced into patient.
❑ Example: Hematopoietic stem cells, skin cells etc.
❑ Benefit over in vivo: Better tolerated and less
associated with severe immune responses.
APPROACHES OF GENE THERAPY CONTD.

17. VECTORS IN GENE THERAPY
❑ Definition: To transfer the therapeutic gene
into a targeted cell, a carrier is required. Such
vehicle of gene delivery are known as vectors.

18. TYPES OF VECTORS
Vectors
Non viral
Physical
Electroporation
Microinjection
Gene gun
Magnetofection
Chemical
Calcium
phosphate
Liposome
Viral
Retrovirus
Adenoviruses
Adeno-associated viruses
Herpes simplex viruses
Figure: Different types of vectors

19. • Efficiently transfer the gene to appropriate target
• Accommodate foreign genes of variable sizes
• Ability to transduce dividing and non dividing cells
• Non toxic
• Non immunogenic
• Non infective
• Avoid harmful side effects
CRITERIA OF IDEAL VECTOR

20. ADVANTAGE OF VIRAL VECTORS
• Target specific types of cells
• They are vey good at entering into cells
• Low immunogenicity and non pathogenic
• Works in both dividing & non dividing cells

21. ❑ New gene might be inserted into wrong location in the
DNA
❑ Vector viruses can infect more than one type of cell
❑ Over expression of missing protein
❑ Gene therapy effectiveness can be reduced by
enhanced immune system.
❑ Costly
COMPLICATIONS OF GENE THERAPY

22. Stem cell mobilizers (eg.
G-CSF,Motixafortide,
plerixafor etc.) are used
for 6 days.
On 5th & 6th day
stem cell is
collected by
Apheresis.
Healthy copy of β-
globin gene is
transferred via
vector into
collected patient’s
stem cell in very
specialized
laboratories
PROCEDURE IN THALASSAEMIA

23. Myeloablation is
done by
chemotherapy to
prepare bone
marrow to receive
corrected stem cell.
Corrected stem cell is
given through IV in 30
minutes/ bag (just like a
blood transfusion). Upto 4
bags are used. Number
of bags varies from
patient to patient.
Continuous
monitoring for 3-6
weeks ,then
annually for 15
years
PROCEDURE IN THALASSAEMIA CONTD.

24. SUMMERY OF THE PROCEDURE

25. Gene Therapy And Transfusion Medicine
❑ To isolate hematopoietic cells in suitable quantities for
transduction–transfection and to support them ex vivo
in culture.
• Transfection and Transduction are gene transfer
techniques. They use different methods to deliver
nucleic acids into the target cell.
• Apheresis machines are used to collect
hematopoietic stem cells.
❑ Supportive treatment (transfusion of blood
component) during myeloablation.
peripheral blood stem cells (PBSCs)
collection in Dhaka Medical College
(30th Nov, 2023)

26. Gene Therapy And Transfusion Medicine
❑ Infusion of either gene-modified cells or direct
administration of vectors that contain the
therapeutic genetic material.
❑ Transfusion medicine laboratories are currently
involved in clinical gene therapy trials.
Picture: Venipuncture

27. ❑ In phase 3 (Ongoing as of march 2021), two studies of 41 patients ( 39 non-
β0/β0 and 12 β0/β0 ) are done. After the treatment with ZYNTEGLO
(betibeglogene autotemcel, gene therapy for thalassaemia) 89% people stopped
transfusions and had a hemoglobin of ≥9 g/dL for ≥12 months.
❑ In phase 2 (Completed enrollment on December, 2022), clinical trial was done
on 380 patients with Mantle Cell Lymphoma (MCL). After treatment with
Tecartus (brexucabtagene autoleucel, gene therapy for relapse/recurrent MCL)
result shows 78% Complete Response Rate and 90% Overall Response Rate
in 12 months follow up.
RESULTS OF GENE THERAPY:

28. ❖ Now multiple clinical trials in Phase 2 and Phase 3 of Gene Therapy are
ongoing on Sickle cell disease, hemophilia A, Multiple myeloma, B-cell
lymphoma, Lipoprotein lipase deficiency, adenosine deaminase deficiency
(ADA-SCID), Duchenne muscular dystrophy, cerebral adrenoleukodystrophy,
head and neck squamous cell carcinoma, B cell lymphoblastic leukemia,
Spinal muscular atrophy, Melanoma etc.
❖ The number of diseases that has been treated successfully by gene therapy
increases.
RESULTS OF GENE THERAPY CONTD.

29. SUMMERY
❑ Genetic Diseases are emerging health issues around the globe and new genetic
disorders are constantly being described in medical literatures every year.
❑ Gene therapy can be permanent and reliable solution for these untreatable
diseases.
❑ Gene therapy is also being applied in many malignant diseases.
❑ Newer form of ex vivo technique of gene therapy is becoming more popular.
❑ Transfusion medicine plays a vital role in gene therapy.

30. Thank You