How Does Gene Therapy Work?

In vivo and Ex vivo Approaches to Gene Therapy

Just how does gene therapy work? And how is genetic material delivered to cells in the first place? Let’s take a deeper look at gene therapy and build knowledge that will help you understand the specific techniques that help researchers and healthcare professionals find ways to treat diseases at the genetic level.

How genetic material is delivered to cells

For any type of gene therapy to work, genetic material first needs to get inside the cells of the person living with the disease.1 This can happen in 1 of 2 ways:

  1. Genetic material can be delivered to target cells that remain inside a person’s body (this is called In vivoinside the body

    See glossary for more terms >
  2. Genetic material can be delivered to a person’s cells after they are taken out of their body (this is called Ex vivooutside the body

    See glossary for more terms >

Choosing the appropriate method to get genetic material into a cell depends on the specific disease and cells involved, as well as the end goal of the treatment. For example, an in vivo treatment that targets specific cells, such as cells in the eye, works well for treating a disorder that affects the structure or function of a person’s eyes. Selecting an ex vivo treatment may be better suited for treating conditions that affect the blood, such as hemophilia, where a person’s own self-renewing stem cells can be engineered with a functional working gene and then delivered into their body.1,2,3

Current in vivo and ex vivo approaches

Image of in vivo gene therapy
Image of ex vivo gene therapy

In vivo delivery

In vivo gene therapy refers to direct delivery of genetic material either intravenously (through an IV) or locally to a specific organ (eg, directly into the eye).2

  • In vivo gene therapy works through the help of a vector, which directly inserts functional copies of a gene into target cells to treat a mutated or missing gene1
  • In vivo delivery of gene therapy has been proven in many areas of research. Some of the currently approved gene therapies deliver genetic material in vivo. Targeted in vivo gene therapy will continue to evolve as scientists continue to refine methods of gene delivery1
Image of ex vivo gene therapy

Ex vivo delivery

Ex vivo gene therapy refers to the process of removing specific cells from a person, genetically altering them in a laboratory, and then transplanting them back into the person.2,3

  • Ex vivo gene therapy works by genetically modifying a patient’s stem cells, which then replace target cells that have a missing or malfunctioning gene2,3
  • Today, ex vivo gene therapy is most frequently applied to hematopoietic stem cells (HSCs); this is used to treat blood and immunological diseases as well as genetic diseases that affect tissues and organs that can be reached by blood cells4

Learn more about VECTORS and how they deliver genetic material in gene therapy.

Genetics and Gene Therapy in Action

View in vivo and ex vivo gene therapy approaches

Explore Genehome
Curious to learn more about the gene therapy treatment process?
Explore Genehome
Curious to learn more about the gene therapy treatment process?
Gene therapy techniques infographic
Discover the different types of gene therapy and learn how they work

Keep learning with Genehome

Expand your knowledge with gene therapy and content sent directly to your inbox.


1. STAT Reports. The STAT guide to viral vectors, the linchpin of gene therapy. STAT News; 2019. 2. American Society of Gene & Cell therapy. Gene and cell therapy FAQs. Accessed May 4, 2021. 3. Keeler AM, ElMallah MK, Flotte TR. Gene therapy 2017: progress and future directions. Clin Transl Sci. 2017:10(4):242-248. 4. Tajer P, Pike-Overzet K, Arias S, Havenga M, Staal F. Ex vivo expansion of hematopoietic stem cells for therapeutic purposes: lessons from development and the niche. Cells. 2019:8(169);1-15.

to Top