Gene therpay is a promising treatment process and it involves the use of various drugs and their mechanisms are important to study for their effevtive usage.

1. Gene Insertion
• These treatments use a harmless virus to carry a good gene into cells,
where the virus inserts it into the existing genome, canceling the effects of
harmful mutations in another gene.
Gendicine
• Gendicine is a virus engineered to carry a gene that has instructions for
making a tumor-fighting protein.
• The virus introduces the gene into tumor cells, causing them to increase
the Expression of tumor-suppressing genes and immune response factors.
• Gendicine is a recombinant adenovirus engineered to express wildtype-
p53 (rAd-p53). This virus is designed to treat patients with tumors which
have mutated p53 genes.
• China’s regulatory agency approved the world’s first commercially
available gene therapy in 2003 to treat head and neck squamous cell
carcinoma, a form of skin cancer.

2. Gendicine mechanism of Action
• Gendicine enters the tumour cells by way of receptor-mediated endocytosis
and begins to over-express genes coding for the p53 protein needed to fight
the tumour.
• Ad-p53 seems to act by stimulating the apoptotic pathway in tumour cells
which increases the expression of tumour suppressor genes that is
Immune response factors.
• It also decreases the expression of multi-drug resistance, vascular
endothelial growth factor and matrix metalloproteinase-2 genes blocking
transcriptional survival signals.
• Ad-p53 appears to act synergistically with conventional treatments such as
chemo- and radiotherapy.
• This synergy still exists in patients with chemotherapy and radiotherapy-
resistant tumors. Gendicine produces fewer side effects than conventional
therapy.

3. Mechanism

5. GLYBERA
• The first gene therapy to be approved in the European Union treated
lipoprotein lipase deficiency (LPLD), a rare inherited disorder that can
cause severe pancreatitis.
• Glybera is used to treat adults with lipoprotein lipase deficiency who have
severe or multiple attacks of pancreatitis (inflammation of the pancreas)
despite maintaining a low-fat diet.
Mechanism of action
• Glybera contains the human LPL (lipoprotein lipase)gene variant LPL
S447X in an adeno-associated virus serotype 1 (AAV1) vector intended to
target the muscle.
• Glybera is injected as a one-time series into the muscle of the lower
extremities where it is taken up by myocytes.
What are myocytes?
• A muscle cell is also known as a myocyte when referring to either a
cardiac muscle cell (cardiomyocyte), a smooth muscle cell as these are
both small cells.
• A skeletal muscle cell is long and threadlike with many nuclei and is called
a muscle fiber.

6. Glybera Mechanism of action
 The adeno-associated virus serotype 1 (AAV1) viral vector
delivers an intact copy of the human lipoprotein lipase (LPL)
gene to muscle cells.
 Glybera contains alipogene tiparvovec as the active
substance. The drug works by breaking down the
chylomicron particles present in the blood. It delivers a
normal LPL gene into the body for correcting the LPL
deficiency.
 The LPL gene is not inserted into the cell's chromosomes but
remains as free floating DNA in the nucleus.
 The injection is followed by immunosuppressive therapy to
prevent immune reactions to the virus.
 The drug normalises the metabolism of fat in the blood and
thereby prevents episodes of pancreatitis.

7. Advantages/Disadvantages
• The advantages of AAV include apparent lack of
pathogenicity, delivery to non-dividing cells, much smaller
risk of insertion compared to retroviruses, which show
random insertion with accompanying risk of cancer.
• AAV also presents very low immunogenicity, mainly
restricted to generating neutralising antibodies, well defined
cytotoxic response.
• The cloning capacity of the vector is limited to replacement
of the virus's 4.8 kilobase genome.
Availability :
• Because LPLD occurs in so few patients, the drug was
unprofitable.
• By 2017 its manufacturer declined to renew its marketing
authorization; Glybera is no longer on the market.

8. Chimeric antigen receptor therapy
(CAR-T )
• CAR-T cell therapy, uses a virus to insert a gene that codes for proteins
called chimeric antigen receptors (CARs) into a patient’s T cells.
• When these cells are reintroduced into the patient’s body, the CARs
allow them to attach to and kill cancer cells in the bloodstream.
Working
• It works by introducing a new gene into a patient’s own T cells that
enables them to find and kill cancer cells.
Definition of (CAR-T):
• They are synthetic receptors comprising an extracellular domain,
derived from an antibody single-chain variable fragment (scFv), An
intracellular domain comprising of signaling domain and a costimulatory
domain derived from T cells.
• Costimulatory receptors are a class of molecules expressed by T
lymphocytes that regulate Activation of T cells and Generation of
effector T-cell responses

9. Insertion of CARs
• Genetic insertion of CARs, most frequently into the T cell genome but
also in other immune cells, allows redirecting them to a desired antigen .
CAR T cell products
Two CAR T cell products specific for the B-cell marker CD19 are as :
• Kymriah (Novartis)
• Yescarta (Kite Pharma)
They became the first therapeutic products registered by the FDA
comprising a genetic engineering element for the treatment of B-ALL and
DLBCL.

10. KYMRIAH:
• Developed for patients with B cell lymphoblastic leukemia, a type of
cancer that affects white blood cells in children and young adults.
• Kymriah was approved by the FDA in 2017 and the E.U. in 2018.
• Clinical trials using anti-CD19 CAR T cells led to a paradigm change
in cancer therapy, based on their unprecedented response rates in
adult patients with recurrent/refractory diffuse large B cell
lymphoma (DLBCL) or pediatric refractory B cell acute
lymphoblastic leukemia (B-ALL) .
• KYMRIAH is a CD19-directed genetically modified autologous T cell
immunotherapy indicated for the treatment of patients up to 25 years of
age with B-cell precursor acute lymphoblastic leukemia (ALL) that is
refractory or in second or later relapse.

11. The most common side effects of KYMRIAH are
• Difficulty breathing.
• Fever (100.4°F/38°C or higher)
• Chills/shaking chills.
• Confusion.
• Severe nausea, vomiting, diarrhea.
• Severe muscle or joint pain.
• Very low blood pressure.
• Dizziness/lightheadedness.
YESCARTA
• Developed to treat a cancer called large B cell lymphoma.
Large B cell lymphoma affects white blood cells called
lymphocytes.
• Yescarta was approved by the FDA in 2017 and in the E.U. in
2018. It is in clinical trials in China.

12. LUXTURNA
• The drug was approved by the FDA in 2017 and in the E.U. in 2018 to
treat patients with a rare form of inherited blindness called biallelic
RPE65 mutation-associated retinal dystrophy.
Leber congenital amaurosis (LCA)
• Leber congenital amaurosis (LCA) is a rare type of inherited eye disorder
that causes severe vision loss at birth. It is the most common cause of
inherited blindness in childhood, and is found in two to three out of
every 100,000 babies.
• Leber's congenital amaurosis, is progressive blindness. Voretigene is the
first treatment available for this condition. It is given as a subretinal
injection.
• The gene therapy is not a cure for the condition, but substantially
improves vision in those treated.

13. Voretigene neparvovec
Voretigene is indicated for the treatment of people with vision loss due to
inherited retinal dystrophy caused by confirmed biallelic RPE65 mutations
and who have sufficient viable retinal cells.
LUXTURNA
It Uses adeno-associated viral vector serotype 2 (AAV2) to carry a functional
copy of the RPE65 gene into the retinal pigment epithelial (RPE) cells to
compensate for the RPE65 mutation.
The RPE65 gene provides instructions for making a protein that is essential
for normal vision.
The RPE65 protein is produced in a thin layer of cells at the back of the eye
called the retinal pigment epithelium (RPE).
Restoring the visual cycle:
With the functional RPE65 protein, 11-cis-retinal (a critical visual pigment
component) regenerates to restore the visual cycle

14. Retinal
• 11-cis-retinal is a retinal having 2E,4Z,6E,8E-double bond geometry.
• It has a role as a chromophore, a human metabolite and a mouse
metabolite.
• A diterpene derived from the carotenoid VITAMIN A which functions as
the active component of the visual cycle.

15. • About 15 patients are diagnosed in Europe every year with severe
immunodeficiency from a rare inherited condition called adenosine
deaminase deficiency (ADA-SCID).
• These patients’ bodies cannot make the ADA enzyme, which is vital for
healthy white blood cells.
Strimvelis :
• Strimvelis, approved in the E.U. in 2016., works by introducing the gene
responsible for producing ADA into stem cells taken from the patient’s
own marrow.
• The cells are then reintroduced into the patient’s bloodstream, where
they are transported to the bone marrow and begin producing normal
white blood cells that can produce ADA.
Adenosine deaminase deficiency (ADA-SCID).

16. Spinal muscular atrophy
• Spinal muscular atrophy (SMA) is a genetic (inherited) neuromuscular
disease that causes muscles to become weak and waste away.
• It is an autosomal recessive disorder characterized by progressive
degeneration of lower motor neurons.
ZOLGENSMA
• In May 2019 the FDA approved Zolgensma for children younger than two
years with spinal muscular atrophy, a neuromuscular disorder that
affects about one in 10,000 people worldwide. It is one of the leading
genetic causes of infant mortality.
survival motor neuron (SMN) gene
• The survival motor neuron (SMN) gene is the putative disease gene for
human spinal muscular atrophy (SMA),
• Two copies of the gene, centromeric and telomeric are present in the
same 5q13 chromosomal region in humans.

17. Conti…
• The SMN1 and SMN2 genes are more than 99 percent identical and lie
within an inverted duplication on chromosome 5q13.
• SMN1 lies telomeric of SMN2. The main difference between them is a C
to T transition in exon 7 of SMN2.
• All individuals with spinal muscular atrophy have mutations in both
copies of the SMN1 gene. As a result, little or no SMN protein is
produced from this gene. The SMN2 gene can help replace some of the
missing SMN protein.
Zolgensma
• Zolgensma delivers a healthy copy of the human SMN gene to a patient’s
motor neurons in a single treatment.

18. ZYNTEGLO
• Granted approval in the E.U. in May 2019, Zynteglo treats a blood disorder
called beta thalassemia.
• Gene Therapy for Patients 12 Years and Older with Transfusion-Dependent β-
Thalassemia Who Do Not Have β⁰/β0 Genotype.
• It reduces a patient’s ability to produce hemoglobin, the protein in red blood
cells that contains iron, leading to life-threatening anemia.
Thalassemia
• Thalassemia is an inherited blood disorder that causes your body to have less
hemoglobin than normal. Hemoglobin enables red blood cells to carry oxygen.
• Thalassemia can cause anemia, leaving you fatigued. If you have mild
thalassemia, you might not need treatment.
• TDT is a severe genetic disease caused by mutations in the β-globin gene that
result in reduced or significantly reduced hemoglobin (Hb).
• In order to survive, people with TDT maintain Hb levels through lifelong chronic
blood transfusions.
• These transfusions carry the risk of progressive multi-organ damage due to
unavoidable iron overload.

19. LentiGlobin BB305 Drug Product
• LentiGlobin BB305 Drug Product aims to treat beta-thalassemia major and
severe sickle cell disease by inserting a functional human beta-globin
gene into the patient's own hematopoietic stem cells ex vivo and then
returning those modified cells to the patient through an autologous stem
cell transplantation.
• LentiGlobin for β-thalassemia adds functional copies of a modified form
of the β-globin gene (βA-T87Q-globin gene) into a patient’s own
hematopoietic (blood) stem cells (HSCs).
• Once a patient has the βA-T87Q-globin gene, they have the potential to
produce HbAT87Q, which is gene therapy-derived hemoglobin, at levels
that may eliminate or significantly reduce the need for transfusions.
• The therapy has been approved for individuals 12 years and older who
require regular blood transfusions.