Young child playing violin with DNA strand stemming from their hand with their friend without Duchenne playing violin

What is gene therapy?

Gene therapy is the transfer or addition of genetic material in cells to help treat a disease and is a type of genetic medicine.1,2 For rare genetic conditions like Duchenne, genetic medicine can be a way to treat the disease at the genetic level.3 This site focuses mainly on education of one type of genetic medicine—gene therapy.

Pfizer's gene therapy for Duchenne muscular dystrophy is being evaluated in clinical trials and is not approved by the FDA. If FDA approved, it may not be an appropriate treatment for all children with Duchenne.

Young child playing violin with DNA strand stemming from their hand with their friend without Duchenne playing violin

Learn the basics of the different types
of genetic medicine approaches


Slide left and right to see types of genetic medicine

Gene regulation with on and off switch

Gene regulation

Changes how the gene
acts, which may include
turning it on or off1

Gene therapy with vector

Gene therapy

Transfers or adds part of a
functioning gene to work in place
of the gene that does not work1

Gene editing with scissors

Gene editing

Removes or corrects
parts of a person’s gene1

Gene regulation, gene therapy (also known as gene transfer or gene addition), and gene editing are all being explored for Duchenne.4 This site focuses mainly on gene therapy education.

Gene therapy uses a shell called a vector, which carries a functional gene to the nucleus of the DMD gene.1,5 This process helps with the production of functional dystrophin protein.6

Viral vector illustration with capsid and functional gene labeled

Viral vectors are made to deliver functional genes5

Viral vectors are created from part of a virus in a lab.5 The outer shell of a virus (the capsid) helps it enter the body’s cells but does not cause a disease.5 Gene therapy uses the capsid but replaces what's inside with other parts, including a functional gene to treat the condition.5

Viral vectors are the most common way to deliver gene therapy.5

The adeno-associated virus (AAV)

The most common type of viral vector in gene therapy is the adeno-associated virus (AAV), which can be made to target certain types of cells.5 Over 20 years of research have shown that AAVs are able to deliver a functioning gene, but there is still more to learn about what this could mean for patients as research continues.7

AAVs do not cause disease and can be found in nature.5 When used in gene therapy, the viral DNA is removed from the AAVs and replaced with a functional copy of a gene; also known as transgene.6,8

It is possible for a child to already have come into contact with AAVs. As a result, the body may have developed neutralizing antibodies (NAbs).6,9 NAbs are found in the immune system and are designed to protect the body from diseases or anything unknown.6 If a child has certain NAbs, this may impact whether they would be a good candidate for gene therapy.

AAV delivering a functioning gene in a cell illustration

How may gene therapy work for Duchenne?

Gene therapy can target a single gene4

Duchenne is caused by mutations to one gene, the DMD gene,4 and gene therapy can target this gene by adding or transferring a functioning gene to produce the functioning dystrophin.1

Gene therapy is designed to target muscle cells6

The AAVs used in gene therapy are designed to target muscle cells to deliver a functioning gene. This transferred gene is being studied for its ability to help restore dystrophin production.5,6 However, the gene transferred does not change the DNA.6

Important studies are underway4

Studies are currently looking at how gene therapy may be able to help slow muscle breakdown and maintain function.4 These are two of the main goals in treating Duchenne.4

Research is ongoing to learn more about Pfizer’s potential gene therapy for Duchenne. This includes safety considerations, immune reaction, how well the treatment may work, how long the treatment may last, and post-treatment considerations.4,10-13

If FDA approved, patients will be closely monitored in the short and long term following treatment as we continue to learn more.

Explore considerations and potential risks


Learn more about the potential gene therapy process

Understand how gene therapies may be administered, what treatment may look like, and get answers to some common questions.

Learn more

1. Food and Drug Administration. What is gene therapy? FDA. Published July 25, 2018. Accessed August 1, 2023. 2. What Are Genetic Therapies? National Heart Lung and Blood Institute. U.S. Department of Health and Human Services. Accessed August 1, 2023. 3. MedlinePlus. Help me understand genetics: MedlinePlus genetics. Accessed August 1, 2023. 4. Duan D, Goemans N, Takeda S, Mercuri E, Aartsma-Rus A. Duchenne muscular dystrophy. Nat Rev Dis Primers. 2021;7(1):1-19. doi: Accessed August 1, 2023. 5. Vectors 101. ASGCT - American Society of Gene & Cell Therapy. Accessed August 1, 2023. 6. Wang D, Tai PWL, Gao G. Adeno-associated virus vector as a platform for gene therapy delivery. Nat Rev Drug Discov. 2019;18(5):358-378. doi: Accessed August 1, 2023. 7. Hastie E, Samulski RJ. Adeno-associated virus at 50: A golden anniversary of discovery, research, and gene therapy success—A personal perspective. Human Gene Therapy. 2015;26(5):257-265. doi: Accessed August 1, 2023. 8. Ryffel GU. Transgene flow: facts, speculations and possible countermeasures. GM Crops Food. 2014;5(4):249-258. doi:10.4161/21645698.2014.945883. Accessed August 1, 2023. 9. Batty P, Lillicrap D. Hemophilia gene therapy: Approaching the first licensed product. HemaSphere. 2021;5(3):e540. Published 2021 Feb 10. doi:10.1097/HS9.0000000000000540. Accessed August 1, 2023. 10. Fortunato F, Rossi R, Falzarano MS, Ferlini A. Innovative therapeutic approaches for Duchenne muscular dystrophy. J Clin Med. 2021;10(4):820. doi: 10.3390/jcm10040820. Accessed December 1, 2023. 11. A study to evaluate the safety and tolerability of PF-06939926 gene therapy in Duchenne muscular dystrophy. Published January 10, 2022. Accessed December 1, 2023. 12. A gene transfer therapy study to evaluate the safety and efficacy of SRP-9001 in participants with Duchenne muscular dystrophy (DMD) (EMBARK). Published December 16, 2021. Accessed December 1, 2023. 13. Microdystrophin gene transfer study in adolescents and children with DMD (IGNITE DMD). Updated August 24, 2021. Accessed December 1, 2023.