This table includes more information about the clinical trials for gene therapies, including the trials that are currently enrolling or expected to begin enrollment.

The table below describes the current gene therapies and gives information so that families can see what they have in common and how they are different. This table also includes very short summaries of results data that have been released thus far, as well as information about side effects.

Many families ask us which of these gene therapies is the “best”, and the answer to that is that we do not yet know. Because the gene therapies are in clinical trials, we are still gathering data to understand how well they work and how long they last.

• The data that we currently have suggests that the gene therapies, especially at the current higher doses, result in increased expression of the micro/mini-dystrophin and that the increase lasts for at least a year.
• Current data also shows that most boys who receive the gene therapy will have side effects. For most, the side effects occur soon after the dosing and are manageable with medications such as steroids and other treatment, and in some cases, hospitalizations.
• We also know that, tragically, one child died after receiving gene therapy. Details regarding what happened for that child are limited.
• We also do not yet know how well the micro/mini-dystrophins will function as a replacement for standard dystrophin or how long the production of the micro/mini-dystrophin will last.

Adeno–associated viruses (AAV) are small viruses that can be deactivated and used to transmit gene–based treatments to patients.

A protein used by the immune system to recognize foreign material in the body. An antibody can bind foreign material to prevent it from infecting a cell or signal the immune system to attach an infected cell.

The measure of how many antibodies a person has for a particular virus. An individual can be tested for the amount of antibodies in the blood that prevent AAV from infecting a cell, i.e. neutralizing antibodies. Alternatively, an individual can be tested for the presence of antibodies that can bind to AAV, though the ability of an antibody to bind a virus does not mean it will prevent the virus from infecting a cell.

The outside shell that protects a virus and helps it penetrate a cell membrane. A capsid is a protein coat that surrounds a virus. A capsid protects the contents, and helps the virus attach to a targeted cell to penetrate the cell membrane. In gene editing, the special characteristics of a capsid can enable gene delivery to specific cells.

CRISPR is a gene–editing technique that allows scientists to alter DNA sequences easily and precisely in order to modify gene function. CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats that are a type of DNA sequence in a gene. This type of DNA sequence is understood by scientists who can use molecular tools to modify how the gene functions.

Gene editing makes targeted changes to existing DNA in genes located on the chromosomes. With gene editing, researchers can enable or disable targeted genes, correct harmful mutations, and change the activity of specific genes. Gene editing is a set of techniques that enable researchers and clinicians to rewrite the instruction encoded in the DNA of genes. These molecular–biology techniques can enable or disable targeted genes, correct harmful mutations, modify expression of genes or change activity of a specific cell, with the goal of restoring normal function. CRISPR is an example of a gene editing technique.

Gene therapy is a technique that modifies a person’s genes to treat or cure disease. Human gene therapy seeks to modify or manipulate the expression of a gene or to alter the biological properties of living cells for therapeutic use. Gene therapies can work by several mechanisms:

• Replacing a disease–causing gene with a healthy copy of the gene
• Inactivating a disease–causing gene that is not functioning properly
• Introducing a new or modified gene into the body to help treat a disease

Gene therapy products are being studied to treat diseases including cancer, genetic diseases, and infectious diseases.

Regions of DNA that direct the production of proteins that are the building blocks of our bodies. Genes are inherited from our biological parents. Defective genes can result in a disease or medical disorder. Genes direct biologically important functions throughout the body. Mutations, or errors, in genes can cause disease by failing to produce sufficient levels of a functional protein.

A type of antibody that binds foreign material, like a virus, and prevents it from infecting cells.

Antibodies to a specific virus that an individual has been exposed to and the immune system has developed antibodies to prevent future infection.

A sequence of DNA that controls where in the body the transgene is expressed or turned on.

Different variations of viruses. Adeno-associated virus has many serotypes being tested in clinical trials. Serotypes can be naturally occurring variations or modified versions created by researchers. Antibodies to one serotype may still retain the ability to neutralize another variant.

The genetic material being delivered to modify, replace, or restore gene expression to begin producing protein.

The ability of different vectors to target specific cell types or tissues. A tropism is the natural attraction of a virus or vector to receptors present only on certain cells or tissues. Gene therapy researchers exploit tropisms to help different viruses, lipid particles, or other therapeutic carriers reach their targeted cells.

Modified virus, cells, or nanoparticles that shuttle the transgene and promoter DNA sequences into the cells of the body.