In the treatment of Duchenne muscular dystrophy (DMD)

Gene therapy may reveal
a new path forward

Pfizer’s investigational gene therapy is being evaluated in clinical trials for the treatment of DMD and is not FDA approved.1-4

Gene therapy is a type of genetic medicine and aims to target the underlying cause of genetic conditions5

Genetic medicine, which uses genetic material in the treatment or prevention of disease, is being studied across various therapeutic areas.6,7 Some examples of genetic medicine include gene therapy,* gene editing, and gene regulation.6‑8

Gene editing is the removal or correction of pieces of DNA within the genome.5

Gene regulation is where the delivered genetic material changes the activity of a gene that is already present in a cell.5

This website primarily focuses on gene therapy.

*Gene therapy may also be called gene transfer or gene addition.

How gene therapy works9-11

Gene therapy diagram

Gene therapy4,9,12

(eg, adeno-associated virus
[AAV] gene addition/transfer)4,9,12

The delivery of a gene into target cells using a vector to produce a functional protein, which is often referred to as gene addition/transfer4

AAV vectors may be used to deliver transgenes10

The vectors used in gene therapy may be broadly classified as viral or non-viral, and as integrating or non-integrating.13

AAV vectors are viral and commonly used as platforms for gene therapy.10

Why AAV vectors may help forge this new path

In the recombinant form used as therapeutic vectors, AAV lacks all viral DNA that codes for viral proteins, and instead contains a transgene (functional gene). Even though these types of vectors are bioengineered based on viral platforms, they are not themselves viruses.10

AAV vectors have broad tropism: many different serotypes exist and can be further engineered to better target specific human cell types.10

Recombinant AAV DNA largely remains episomal, and random integration events are observed with low frequency (<1%).9,14

AAV was first used in clinical trials over 25 years ago, and there is a growing body of evidence supporting the use of AAV vectors for gene therapy.9,10

Gene therapies using AAV vectors are FDA approved for certain diseases, and clinical trials are ongoing for more diseases.2,15,16

Key considerations

Although AAV vectors are considered less immunogenic than other viral vector types, they can be associated with an immune-mediated response in some patients.10

The transgene itself may also elicit an immune response, which can affect the initial gene delivery.17

Gene therapies are under investigation for many different diseases. As clinical trials progress, the scientific understanding of the safety profile for these therapies will continue to evolve.10

  • Risks vary depending on the specific gene therapy and the disease being treated18
  • Among these risks, immunogenicity remains a significant challenge in gene therapy18

Gene therapy trials for some diseases have shown that the duration of transgene expression varies from one individual to another. Research is ongoing to better understand these implications.19

People may have preexisting NAbs to AAV serotypes from prior exposure, which may limit eligibility for gene therapy.1,20

Coprevalence of NAbs against multiple serotypes may limit options for using gene therapies with other viral vectors in the future.1,20

Following gene therapy administration, a long-lasting immunity may develop.1,20 This may preclude retreatment with the same or similar gene therapies, potentially limiting current options to a single administration.1,17

Attributes that may be important to consider when determining appropriate patients for gene therapy include:

  • Eligibility for gene therapy
  • Safety considerations
  • Post-infusion follow-up requirements (including long-term monitoring)

Research on genetic medicines
for DMD is ongoing

Gene therapy is an evolving science

Research is ongoing to understand Pfizer’s investigational gene therapy for DMD, including safety considerations, immune response, efficacy, durability, and post-treatment considerations.1-3,21,22

If Pfizer's gene therapy for DMD is FDA approved, patients will be monitored in the short and long term following treatment.