What is gene therapy?

Gene therapy is a treatment being developed to fight diseases caused by genetic defects. This is a relatively new medical intervention that is mostly experimental, including human and animal trials, to treat certain diseases, such as cystic fibrosis.

Gene therapy aims to change the unhealthy proteins produced by disease-causing genes.

What is gene therapy?

Some diseases are caused by known genetic defects or gene mutations. This means that there is an inherited or acquired error in the DNA molecule that codes for the production of a specific protein in the body. Altered proteins do not function as they should, leading to disease.

The idea behind gene therapy is to instruct the body to produce healthy proteins that don’t cause disease.

This therapy involves the delivery of DNA or RNA. RNA molecules are intermediate molecules formed during protein production. Genetic defects in some diseases have been identified, but many genetic mutations have not been identified (they may appear in the future).

Ways to correct genetic defects associated with certain diseases are being researched. Different types and approaches of gene therapy are being investigated.

The basis of genes, DNA and chromosomes

Types of gene therapy

Genetic mutations can be inherited, which means they are inherited from parents. Genetic defects can also be acquired, sometimes due to environmental factors such as smoking.

Gene therapy is being evaluated as a potential treatment for both mutations. There are several ways to deliver corrected DNA or RNA into the human body.

Most cells in your body are somatic cells. The only cells that are not somatic are germ cells, which produce eggs and sperm cells that can produce offspring.

Somatic gene therapy: Somatic gene therapy aims to correct defects in the DNA of somatic cells or to deliver RNA molecules to treat or prevent genetic disorders in the person receiving treatment. This treatment is available if you have a genetic mutation or the mutation due to environmental factors.

Germline gene therapy: Germline gene therapy aims to correct defects in egg or sperm cells to prevent inherited diseases that ultimately affect future offspring.


A person’s own cells can sometimes be taken from the bone marrow, genetically modified in the lab, and then reimplanted in the body.

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viral vector

A viral vector is a virus that has been engineered so that it does not cause viral infection. The correct DNA or RNA sequence is then injected. Gene therapy can be performed by injecting a viral vector containing the correct gene into the human body.

stem cell

Stem cells are immature cells that have the potential to develop into different types of cells. Sometimes genetically modified stem cells are transplanted into the body to replace defective cells as a way to treat diseases.


This technique uses lipids (fats) to deliver genetic DNA or RNA material.

Why Gene Therapy?

Some genetic mutations direct the body to make disease-causing proteins. Some genetic mutations are nonfunctional—they cause disease because the body lacks the healthy proteins that genes should normally produce.

Gene therapy aims to instruct the body to produce healthy proteins or inhibit the production of defective proteins. It depends on the type of mutation that causes the disease.

Gene Enhancement Therapy: Replacing Mutated Genes

With genetic enhancement, the goal is to help the body make healthy protein.

Sometimes a DNA molecule can insert a gene. This is to permanently change the DNA so that the body can produce new cells with the correct DNA code. The new cells will then also produce healthy products.

Some studies using gene-enhancing therapy involve inserting healthy DNA molecules or RNA sequences into cells, but not the recipient’s DNA. Experimental studies have shown that this triggers the production of healthy proteins, but future copies of cells are not expected to contain healthy genes.

Gene suppression therapy: inactivating mutant genes

Sometimes gene therapy is aimed at eliminating the activity of a mutated gene to prevent the production of a disease-causing protein. This is done by inserting a non-mutated genetic DNA sequence into the DNA molecule.

Make disease cells visible to the immune system

Another type of gene therapy involves the body’s immune system. An example of such therapy is the use of checkpoint inhibitors. With this therapy, the immune system is modified to recognize substances in the body produced by mutated genes, thereby destroying them and preventing the diseases they cause.

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Risks of gene therapy

Gene therapy has some known risks. By far the most common problem associated with gene therapy is lack of effectiveness. However, there are also possible adverse effects.

unwanted immune system response

Gene therapy involving the immune system can cause an excessive immune response to healthy cells that resemble diseased cells, potentially causing damage to healthy cells.

wrong target cell

Potentially, the immune response mediated by gene therapy may affect the wrong cell type rather than the intended target cells.

Infections caused by viral vectors

When viral vectors are used, there may be a risk of infection by the virus. Depending on the underlying disease being treated, a person receiving gene therapy may have a weakened immune system and therefore may have difficulty fighting the virus.

possible tumor

New DNA sequences inserted into human genes can cause mutations that can lead to cancer formation.

What to expect from gene therapy

If you are considering gene therapy, you will go through a process of diagnosis, treatment and medical monitoring to assess the effect.


This step will determine if you have a disease that can be treated with gene therapy. This means that you will need to send a blood sample to a laboratory to identify treatable genetic mutations associated with your medical condition.

Examples of diseases that can be treated with gene therapy include:

  • Cystic fibrosis: an inherited disorder that produces sticky mucus that blocks the airways and hinders the production of digestive enzymes
  • sickle cell disease: an inherited disorder that causes abnormal production of hemoglobin (the oxygen-carrying protein in red blood cells)
  • Leber’s Hereditary Optic Neuropathy (LHON): An inherited disorder that causes cells in the optic nerve to die, resulting in loss of central vision
  • Inherited or acquired retinal disease: a disorder that damages the retina (the light-sensitive layer at the back of the eye)
  • WW-domain-containing oxidoreductase (WWOX) epileptic encephalopathy syndrome: a genetic disorder that causes severe epilepsy, developmental delay, and early death
  • Spinocerebellar ataxia and autosomal recessive 12 (SCAR12): an inherited disorder that causes seizures, developmental delay, and inability to coordinate movements in infancy
  • Cancer: Multiple Cancers


Your treatment may involve harvesting your cells and using viral vectors or liposomes to deliver genes into your cells. The modified cells will return to your body after treatment.

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The effect of your treatment will be assessed and you will be monitored for adverse events (side effects). If this happens, you may be treated again.

Clinical Trials

You can find clinical trials for gene therapy by talking to your doctor or searching for organizations that support your medical condition, such as the Cystic Fibrosis Foundation.


Gene therapy is a relatively new type of treatment aimed at relieving disease by modifying the defective gene or altering the protein produced by the defective gene. There are several ways to insert healthy genes into the body, such as inside an inactivated virus or inside fat particles.

Sometimes immature and healthy cells are transplanted to replace cells with a disease-causing mutation. This type of therapy can cause side effects and there is also a risk that it may not work.

VigorTip words

If you have a genetic disorder with a known and established genetic mutation, you may be a candidate for gene therapy treatment in clinical trials. This type of treatment is not standard, and you need to monitor it closely so you and your doctor know if the treatment is working and if you have any side effects.

You can discuss gene therapy with your doctor. This treatment is not universal, so if there are no studies near you, you may need to travel to participate in clinical trials.

Frequently Asked Questions

  • Is gene therapy safe?

    This therapy is considered safe, but there are risks and side effects. You may have the opportunity to participate in a clinical trial and will be monitored for side effects and adverse reactions.

  • What is an example of gene therapy?

    An example of such a therapy is the use of inactivated viruses to insert a portion of a DNA molecule into human cells, so that healthy DNA sequences can provide the blueprint for healthy proteins.

  • What is the main goal of gene therapy?

    The main goal of gene therapy is to provide DNA or RNA that encodes healthy proteins so that the body is not affected by genetic diseases.