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Science of
Gene Therapy

There are different approaches and processes to genetic medicine being studied across various therapeutic areas today. Some examples include changing
gene regulation
Gene regulation
The process of turning genes on and off. During early development, cells begin to take on specific functions. Gene regulation ensures that the appropriate genes are expressed at the proper times. Gene regulation can also help an organism respond to its environment. Gene regulation is accomplished by a variety of mechanisms, including chemically modifying genes and using regulatory proteins to turn genes on or off.
, gene transfer or addition, and
gene editing
Gene editing
The goal of gene editing is to remove or correct pieces of DNA within a person’s gene, rather than replace the gene in the cell with a healthy gene, as gene transfer or addition would do.
. While some approaches like gene editing are being explored in early stage
clinical research
Clinical research
A controlled way to study health and illness in people.
in hemophilia, most later stage research and
phase III clinical trials
Phase III clinical trials
Usually the last stage of research before a new medicine can be considered for regulatory approval by an organization like the FDA. Compared to phase I or phase II clinical trials, phase III trials usually include more participants to evaluate a medicine’s efficacy and safety in a larger group.
in hemophilia have focused on gene transfer or addition. The content on this website is focused on this particular approach,
gene transfer or addition
Gene therapy (transfer or addition)
The transfer or addition or genetic material into a cell. Once in the cell, a working copy of a gene can help make proteins despite the presence of a faulty or mutated gene.
hereby referred to as gene therapy.
illustration of a carrier shell with a gene inside

In gene therapy, a carrier shell Capsid / Carrier / Carrier Shell A protein that contains therapeutic genes to deliver to cells. A capsid with the therapeutic gene inside is called a vector. Often, these vectors are created from parts of a virus. The virus has been changed so that a person doesn’t get sick from it. delivers a healthy (working or functioning) gene, which is introduced into the cells of a person to treat a specific genetic condition.

illustration of a carrier shell with a gene inside and four drone propellers representing gene therapy vector delivery

When carriers contain healthy or functional genes, they are called vectors. Vector A vector is a vehicle designed to deliver therapeutic genes directly into target organs, such as the liver. Vectors are made up of carriers or capsids, with therapeutic or healthy genes contained inside. Vectors are essentially vehicles designed to deliver healthy genes directly into target organs, such as the liver.

illustration of a fictional drone vector in flight delivering a gene to a landing pad symbolizing the liver

When carriers contain healthy or functional genes, they are called vectors. Vector A vector is a vehicle designed to deliver therapeutic genes directly into target organs, such as the liver. Vectors are made up of carriers or capsids, with therapeutic or healthy genes contained inside. Vectors are essentially vehicles designed to deliver healthy genes directly into target organs, such as the liver.

illustration of a fictional drone vector in flight

There are different types of vectors, and they are often made of modified viruses. Although viruses sometimes have a negative association, scientists researching gene therapy have developed ways to use only the carrier shell of a virus as a delivery system, so all viral DNA Viral DNA DNA of a virus, included within the capsid or protein shell of the virus. DNA viruses infect host cells and use them to replicate or copy the viral DNA. is removed.

While gene therapy introduces a healthy gene to a person’s body, it does not replace or edit the mutated gene or change a person’s DNA. The healthy gene simply provides the body with the information that is needed to produce the missing or nonfunctional protein. In the case of hemophilia, the healthy gene provides the information needed for the body to produce clotting factor protein VIII or IX. Since a person’s DNA is not changed after gene therapy, people treated with gene therapy may still pass on genetic mutations and conditions to their children.

The illustrations are for educational purposes only and do not exactly represent the carriers in gene therapy.

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In gene therapy, a carrier shell Capsid / Carrier / Carrier Shell A protein that contains therapeutic genes to deliver to cells. A capsid with the therapeutic gene inside is called a vector. Often, these vectors are created from parts of a virus. The virus has been changed so that a person doesn’t get sick from it. delivers a healthy (working or functioning) gene, which is introduced into the cells of a person to treat a specific genetic condition.

When carriers contain healthy or functional genes, they are called vectors. Vector A vector is a vehicle designed to deliver therapeutic genes directly into target organs, such as the liver. Vectors are made up of carriers or capsids, with therapeutic or healthy genes contained inside. Vectors are essentially vehicles designed to deliver healthy genes directly into target organs, such as the liver.

When carriers contain healthy or functional genes, they are called vectors. Vector A vector is a vehicle designed to deliver therapeutic genes directly into target organs, such as the liver. Vectors are made up of carriers or capsids, with therapeutic or healthy genes contained inside. Vectors are essentially vehicles designed to deliver healthy genes directly into target organs, such as the liver.

While gene therapy introduces a healthy gene to a person’s body, it does not replace or edit the mutated gene or change a person’s DNA. The healthy gene simply provides the body with the information that is needed to produce the missing or nonfunctional protein. In the case of hemophilia, the healthy gene provides the information needed for the body to produce clotting factor protein VIII or IX. Since a person’s DNA is not changed after gene therapy, people treated with gene therapy may still pass on genetic mutations and conditions to their children.

The illustrations are for educational purposes only and do not exactly represent the carriers in gene therapy.

Why vectors are used
for hemophilia gene
therapy research

Most later-stage gene therapy research for hemophilia is exploring vectors made from a type of virus called
adeno-associated virus (AAV)
Adeno-associated virus (AAV)
A single-stranded DNA virus that has not been found to cause disease in humans. It is currently the most frequently used virus in gene therapy clinical research.
. AAVs were first used in clinical trials over 20 years ago, and there is growing support for using them in hemophilia gene therapy.
In hemophilia research, the AAV viral DNA is removed and replaced with a healthy gene, creating a recombinant AAV (rAAV). The rAAV or recombinant adeno-associated virus is designed to travel in the body and deliver the healthy or functional gene to its target—liver cells— where clotting factor can be produced.
AAVs are not known for causing disease and can be found in the environment. In fact, some people will have already been exposed to them and have developed
neutralizing antibodies (NAbs)
Neutralizing antibodies (NAbs)
A specific type of antibody, or immune system protein, that defends cells from foreign substances like bacteria or viruses that can cause disease. In gene therapy clinical research, individuals may have neutralizing antibodies to an adeno-associated viral vector, and these may attack and destroy the vectors before they are able to deliver the healthy gene to the intended cells in the body.
as a result (and some people may not be aware if they have been exposed to AAV during their lifetime).
In gene therapy clinical trials, some patients have been tested to measure existing levels of NAbs in the body, and some trials have used the presence of NAbs to include or exclude certain patients from research.
The potential impact of NAbs on gene therapy efficacy, safety, and length of effect is an important question that is currently being assessed in research. As the science evolves, we will learn more about the importance of NAbs and whether NAb testing can inform patients about their eligibility for different gene therapies.
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Discover how Gene Therapy works by watching this video:

Exposure to the rAAV vector through gene therapy may cause the body to produce NAbs, which may impact future dosing.

For more information on these and other considerations, click below.

See Considerations
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