Vaccines, Blood & Biologics

What is Gene Therapy?

Human gene therapy is the administration of genetic material to modify or manipulate the expression of a gene product or to alter the biological properties of living cells for therapeutic use 1.

Gene therapy is a technique that modifies a person’s genes to treat or cure disease. 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.

There are a variety of types of gene therapy products, including:

  • Plasmid DNA: Circular DNA molecules can be genetically engineered to carry therapeutic genes into human cells.
  • Viral vectors: Viruses have a natural ability to deliver genetic material into cells, and therefore some gene therapy products are derived from viruses. Once viruses have been modified to remove their ability to cause infectious disease, these modified viruses can be used as vectors (vehicles) to carry therapeutic genes into human cells.
  • Bacterial vectors: Bacteria can be modified to prevent them from causing infectious disease and then used as vectors (vehicles) to carry therapeutic genes into human tissues.
  • Human gene editing technology: The goals of gene editing are to disrupt harmful genes or to repair mutated genes.
  • Patient-derived cellular gene therapy products: Cells are removed from the patient, genetically modified (often using a viral vector) and then returned to the patient.

This graphic depicts the two major types of gene therapy.  The illustration on the left shows ex vivo gene therapy, where the cells are modified outside the body and then are delivered back to the patient.  The illustration on the right shows in vivo gene therapy, where the genetic modification of the cell takes place inside the body.
Gene therapy products are biological products regulated by the FDA’s Center for Biologics Evaluation and Research (CBER). Clinical studies in humans require the submission of an investigational new drug application (IND) prior to initiating clinical studies in the United States. Marketing a gene therapy product requires submission and approval of a biologics license application (BLA).


1 Federal Register Volume 66, Number 12. Thursday, January 18, 2001

Page Last Updated: 08/30/2017
Note: If you need help accessing information in different file formats, see Instructions for Downloading Viewers and Players.
Language Assistance Available: Español | 繁體中文 | Tiếng Việt | 한국어 | Tagalog | Русский | العربية | Kreyòl Ayisyen | Français | Polski | Português | Italiano | Deutsch | 日本語 | فارسی | English