Cell and Gene Therapy for Sickle Cell Disease Final.pdf

Cell and gene therapy are innovative medical treatments that involve using cells and genes to prevent, treat, or cure diseases. Here's a brief overview:

*Cell Therapy:*

- Involves introducing healthy cells into the body to replace damaged or diseased cells
- Can be used to treat various conditions, such as:
- Cancer (e.g., CAR-T cell therapy)
- Genetic disorders (e.g., sickle cell anemia)
- Autoimmune diseases (e.g., type 1 diabetes)
- Regenerative medicine (e.g., tissue engineering)

*Gene Therapy:*

- Involves introducing healthy copies of a gene into cells to replace faulty or missing genes
- Can be used to treat genetic disorders, such as:
- Inherited diseases (e.g., cystic fibrosis)
- Cancer (e.g., gene editing to selectively kill cancer cells)
- Rare genetic conditions (e.g., muscular dystrophy)

*Types of Gene Therapy:*

- Ex vivo: Cells are removed, genetically modified, and returned to the body
- In vivo: Genes are introduced directly into cells within the body
- Gene editing: Technologies like CRISPR/Cas9 enable precise editing of genes

*Benefits and Challenges:*

Benefits:

- Potential for long-term or permanent treatment of genetic diseases
- Targeted treatment with minimal side effects
- Innovative approach to treating complex diseases

Challenges:

- Safety concerns (e.g., off-target effects, immune responses)
- Efficacy and durability of treatment
- High costs and accessibility
- Regulatory frameworks and ethical considerations

Cell and gene therapy hold tremendous promise for revolutionizing the treatment of various diseases. Ongoing research and advancements aim to address the challenges and unlock the full potential of these innovative therapies.

1. Emerging Cell Therapies for Sickle
Cell Disease
Abba C. Zubair MD., PhD
Professor and Consultant Transfusion Medicine,
Dean, Mayo Clinic Alix School of Medicine Florida Campus

2. Agenda
•Overview of Sickle Cell Disease
•Diagnostic Techniques
•Emerging Cell Therapies for
Sickle Cell Disease

3. An
Introduction
to Sickle
Cell Anemia
Definition of Sickle Cell Anemia
Sickle cell anemia is a genetic blood disorder that
affects the shape and function of red blood cells,
leading to pain, infection, and organ damage.
Prevalence of Sickle Cell Anemia
Sickle cell anemia is most common in people of
African, Middle Eastern, and Mediterranean
descent, but it also affects people from other
ethnic backgrounds. It is estimated that over
300,000 babies are born with sickle cell anemia
every year around the world.

4. Causes and
Symptoms
of Sickle
Cell Anemia
Genetic Causes
•Sickle cell anemia is caused by a genetic mutation in the
HBB gene that affects the production of beta-globin in
hemoglobin, a protein in red blood cells that carries
oxygen throughout the body. This causes red blood cells
to become fragile and break down more quickly than
normal cells.
Symptoms of Sickle Cell Anemia
•Vaso-occlusive phenomena and hemolysis are the clinical
hallmark
•Symptoms of sickle cell anemia can range from mild to
severe and include:
•Bone and joint complications
•Cerebrovascular disease
•Fever
•Hepatic disease
•Pain management
•Priapism
•Pulmonary hypertension
•Renal manifestations

5. Available Treatments for Sickle
Cell Anemia
Blood Transfusions
Blood transfusions are a common treatment for sickle cell anemia. They can help
increase the number of healthy red blood cells in the body and reduce
complications associated with the disease.
Bone Marrow Transplants
Bone marrow transplants are often used to treat sickle cell anemia in severe
cases. The procedure involves replacing the patient's bone marrow with healthy
bone marrow from a donor.
Medications for Symptom Management
Medications can be used to manage symptoms of sickle cell anemia, including
pain, infections, and complications. These medications may include pain
relievers, antibiotics, and hydroxyurea, among others.

6. Management of
Sickle Cell Anemia
Lifestyle Changes
Patients with sickle cell anemia can manage their
condition by making lifestyle changes such as
drinking plenty of fluids, getting enough rest, eating a
healthy diet, and avoiding extreme temperatures.
Support Groups
Joining a support group can help patients with sickle
cell anemia feel less isolated and improve their
overall quality of life. Support groups can provide
emotional support, connect patients with resources,
and provide a sense of community.

7. Diagnostic
Techniques

8. Diagnostic Techniques for Sickle
Cell Disease
•Hemoglobin electrophoresis
•DNA analysis
•Newborn screening

9. Common diagnostic techniques for sickle cell
disease
•Hemoglobin electrophoresis is the
most common diagnostic test for
SCD
•Newborn screening is now
standard practice in the United
States
•DNA analysis can confirm
diagnosis and identify carrier
status

10. Curative Therapies in
Sickle Cell Disease

11. Stem Cell Therapy for
Sickle Cell Disease
•Stem cell therapy involves using
stem cells to replace damaged or
diseased cells
•Hematopoietic stem cell
transplantation is a type of stem cell
therapy
•Challenges include finding
compatible donors and minimizing
complications

12. Hematopoietic Stem
Cell Transplantation
•Allogeneic Hematopoietic
Stem Cell Transplantation
•Matched Sibling Donor (MSD)
established treatment
•Alternative donors
(haploidentical, matched
unrelated) becoming viable
options
•Gene Therapy
•Use in SCD is evolving

13. Potentially Curative Therapies
Discussion
•Potentially curative therapies for
SCD patients
•Indications
•Clinical outcomes
•Transplant strategies specific to SCD
population

14. Other Therapies
for SCD
Hydroxyurea
•Hydroxyurea use in sickle cell
disease
Other medical therapies
•Prevent pain and other
complications
Transfusions
•Red blood cell transfusion in
sickle cell disease:
•Indications and transfusion
techniques'
Investigational non-
curative approaches
•Investigational pharmacologic
therapies
Routine pediatric care
•infancy and childhood:
•Routine health care
maintenance and
anticipatory guidance
Comprehensive
specialist care
•Management and prognosis

15. Terminology and
Clinical
Phenotype
Gene Therapy
and Gene
Editing
Delivery of genetically modified autologous HSCs
Genetic modification can be achieved by gene addition or
gene editing
Hematopoietic
Stem Cell
Transplantation
(HCT)
Allogeneic transplantation uses HSCs from a donor
Autologous transplantation uses patient's own HSCs
Conditioning regimens can be myeloablative,
nonmyeloablative, or reduced-intensity
Sickle Cell
Disease (SCD)
Includes homozygosity for sickle cell variant in beta globin
gene
Characterized by hemolytic anemia, microvascular
occlusion, and sickling

16. Decision to
Consider
Curative
Therapy
Professional opinions vary on whether children and
adults with SCD should receive curative therapy
•Due to continued evolution of care for SCD
•Increased number of curative therapy options
•Short lifespan in adults
•Lack of randomized controlled trials
Opinions for children vary widely
•From only offering curative therapy for severe cases
•To offering curative therapy to children as young as two years of age
Opportunity for discussion and shared decision-
making
•Decision to consider transplantation is challenging and highly
individualized
•Patients should have the opportunity to discuss risks and benefits
with their primary hematologist and experts at a center that treats
SCD

17. Planning and
Preparation for
Transplantation
•Best outcomes in patients
•HLA-matched sibling donor transplantation
Timing of
transplantation
•HLA-matched sibling donor provides greatest chance of
cure
•Other options include haploidentical donor or matched
unrelated donor
Donor Selection
•No direct comparisons between bone marrow and
peripheral blood stem cells
•Endorse source used in multicenter peer reviewed clinical
trials
Stem Cell Source
•Advocate pursuing complete donor-derived myeloid
chimerism
Conditioning
Regimen
Testing and
Interventions Prior
to Transplant

18. Clinical
Experience and
Transplant
Outcomes
First successful allogeneic HCT for SCD in 1984
•8-year-old patient with recurrent vaso-occlusive pain episodes and AML
•Received bone marrow from matched related sibling with sickle cell trait
•Resolution of vaso-occlusive pain episodes and full donor chimerism
Experience with allogeneic HCT has continued to accrue
•No randomized trials comparing HCT with medical therapy or different transplantation
protocols
•Preferred approach may differ in adults and children
Survival with HLA-identical sibling donors is excellent in children and adults
Graft failure has continued to improve
Risk factors for GvHD include patient age, donor type, stem cell source,
conditioning regimen, GvHD prophylaxis, and recipient characteristics

19. Post
-
Transplantation
Care
Slow weaning of
GvHD prophylaxis
•Immunosuppressive
therapy used for
longer periods than
in transplantations
for hematologic
malignancies
•Pre-transplant ATG
and post-transplant
cyclophosphamide
used as rejection
and GvHD
prophylaxis
•Commonly used
immunosuppressive
medications include
sirolimus,
cyclosporine,
tacrolimus, and
mycophenolate
mofetil
Assessing
engraftment and
donor chimerism
•Engraftment
assessed according
to degree of donor
chimerism
•Donor chimerism of
>95% is considered
full donor
chimerism
•Donor chimerism of
•Donor chimerism
between 5% and
95% is called mixed
chimerism
Supportive care

20. Overview of Gene Therapy and Gene Editing
•These approaches modify the person's own HSCs
•Concerns about GvHD and the need for immunosuppression do not
apply
Gene therapy and gene editing have
the potential to cure SCD
CRISPR-Cas9 is one of the most
studied tools for gene editing
•Lovotibeglogene autotemcel (lovo-cel, Lyfgenia) is a gene therapy
construct
Two autologous cell-based therapies
approved by FDA in December 2023
Other general conceptual strategies
include replacing the abnormal allele,
increasing Hb F expression, and
expressing delta globin
Issues remain related to the safety and
efficacy of the delivery methods
Myeloid malignancy is a particularly
concerning outcome
Other areas of active research include
alternatives to myeloablative therapy
and direct delivery to the patient

21. Approaches to
CRISPR-Cas9 Gene
Editing Technology
•Homology-directed repair is a precise
and efficient method of gene editing
•Non-homologous end joining is a less
precise method of gene editing
•CRISPR-Cas9 can be used for gene
knockouts, gene correction, and gene
insertion

22. CRISPR-Cas9 Gene
Editing Technology
•CRISPR-Cas9 allows scientists to
make precise changes to the DNA of
living organisms
•Cas9 acts like molecular scissors,
cutting the DNA at the targeted
location
•CRISPR-Cas9 has the potential to
transform medicine, agriculture, and
many other fields

23. Beta Globin Gene Correction
Correction of Sickle Cell Variant
•Reversion to wild-type sequence at beta globin gene
locus
•Converts SCD to sickle cell trait or normal adult
hemoglobin
Gene Correction and Editing
•Wild-type beta globin gene used as template for
endonucleases to repair mutant sequence
•Preclinical model able to correct sickle mutation in
cultured bone marrow cells
Nulabeglogene Autogedtemcel
•CRISPR-Cas9 gene editing system used to correct sickle
cell mutation
•Clinical trial paused due to unexpected cytopenias
attributed to therapy

24. Anti-Sickling
Beta Globin
Gene Therapy
Anti-sickling beta globin gene (lovo-cel, Lyfgenia)
•An artificial version of the beta globin gene
•Creates an amino acid substitution of glutamine for threonine at
position 87 (beta globin T87Q)
Gene therapy with lovotibeglogene autotemcel (lovo-
cel, Lyfgenia)
•Consists of autologous CD34-enriched hematopoietic stem and
progenitor cells transduced with the lentiviral vector BB305 that
expresses Hb AT87Q
Clinical experience
•13-year-old boy with SCD treated with an autologous
transplantation using this construct
•Increasing expression of the modified beta globin until it reached
stable levels of approximately 50 percent of total hemoglobin at
nine months

25. Gamma Globin
Upregulation
•Separate from beta globin and does not contain
Hb S mutation
Gamma globin gene is
source of gamma chains
for fetal Hb F
•Blocking BCL11A function can increase Hb F
levels and reduce sickling and vaso-occlusive
complications
Switch from gamma to
beta globin expression
controlled by BCL11A
gene
•Exa-cel (Casgevy) disrupts BCL11A expression in
autologous HSCs
•OTQ923 disrupts gamma globin promotor region
Gene editing using
CRISPR-Cas9 can target
BCL11A or gamma globin
promotor
•BIVV003 uses ZFN to target BCL11A
Gene editing using zinc
finger nucleases can
also target BCL11A
•shRNA embedded in microRNA for erythroid-
specific knockdown in autologous HSCs
RNAi can target BCL11A
mRNA

26. Delta Globin Gene
•Delta globin gene produces beta globin-like
chains for Hb A2
•Hb A2 inhibits the polymerization of
Hb S
•Increasing delta globin gene expression
may be valuable for SCD treatment
•Studies in transgenic SCD mice
support this
•Gene therapy to introduce delta globin
gene has not been reported
•Patients with high Hb A2 levels have
milder SCD phenotype

27. Plerixafor for
Mobilization
Plerixafor is used for mobilizing CD34
positive stem and progenitor cells in SCD
•13 out of 15 patients had adequate numbers of
CD34 positive cells after a single dose
•11 patients experienced pain, with 3 requiring
hospitalization
•Plerixafor-mobilized HSCs were enriched for an
engrafting population
Severity of SCD, number of medications
used against chronic pain, and period of
hydroxyurea being held prior to mobilization
influenced CD34 positive yields

28. Concern about
Myeloid
Malignancy in
Gene Therapy
Studies
Gene therapy studies using lentiviral vectors were suspended
temporarily after 2 individuals developed myeloid malignancies
For the first participant, MDS/AML was not related to the viral
vector but was a result of the conditioning regimen in combination
with a higher risk of mutational burden due to the underlying SCD
Evaluation of the second patient determined that the gene therapy
construct was unlikely to be responsible
Two other patients who were originally suspected of having MDS
had transfusion-dependent anemia and trisomy 8, but there was
no evidence of dysplasia or blasts on bone marrow evaluation
Studies are indicated to assess for genetic risk factors for MDS
and AML development after gene therapy for SCD

29. Choice of Gene
Therapy/Gene
Editing
Approaches
Caution advised for children with severe SCD
pursuing gene therapy or gene editing
•4% of participants in one trial developed MDS/AML
•High rate of mortality
Therapeutic dilemma posed by availability of two
different therapies
•Lovotibeglogene autotemcel (Lyfgenia)
•Exagamglogene autotemcel (exa-cel, Casgevy)
No conclusions on comparative safety or efficacy
due to absence of side-to-side comparison
Lyfgenia may cause anemia with erythroid dysplasia
in patients with alpha thalassemia trait
Patients with high baseline Hb F expression should
be evaluated before initiating Casgevy

30. Challenges and
Future Directions
•Limited availability of donors
•High costs
•Complications of
transplantation
•Research on other cell
therapies
•Collaboration among
researchers and clinicians

31. Summary and Recommendations
Definitions of curative therapies for SCD
Decision to consider curative therapy is highly individualized
Curative therapy is most likely to be considered for individuals with SCD complications associated with early
mortality or severe morbidity
Transplantation is most successful in children using myeloablative conditioning and an HLA-matched sibling
donor
Gene therapy and gene editing have been approved and appear promising, but long-term outcomes need
further study