What is Gene Therapy?

Gene therapy represents a landmark opportunity to treat inherited genetic disease.  Several thousand human diseases are caused by harmful changes to a single gene, and scientists have identified the genes responsible for many of these illnesses.  Gene therapy aims to treat specific diseases by correcting the faulty gene.  Some well-known diseases attributable to changes in a single gene include cystic fibrosis, hemophilia, muscular dystrophy, spinal muscular atrophy, and sickle cell anemia.  In addition, scientists are designing other gene therapies to combat cancer and infectious diseases. 

DNA is the genetic material we inherit from our parents, and its unique code inscribes a master plan for all of our biological processes.  DNA contains information for all of the proteins produced in our body.  Each gene carries instructions for creating a particular protein, and proteins carry out the majority of cellular functions.  For instance, antibodies, enzymes, and hormones are all proteins. 

Gene therapy treats disease by introducing new genetic material.  Often, the therapy provides instructions for making a beneficial protein.  There are five distinct strategies deployed in gene therapy.

- Gene addition supplements the cell with a working copy of the mutated gene or a new gene, and it is a common approach in gene therapy.

- Gene correction attempts to repair the original, defective gene.

- Gene silencing prevents protein production stemming from the detrimental gene.

- Reprogramming delivers multiple genes to completely change the cell.

- Cell elimination delivers “suicide” genes to destroy the cell. 

Because cells do not efficiently take up genes, a specialized transporter is required.  Scientists are developing viral and non-viral vectors for this purpose. 

- Viral vectors are designed using a modified virus whose illness-causing elements have been removed and replaced with the therapeutic gene.  Once the viral vector infects the cells, the therapeutic payload gets to work restoring normal physiology. 

- Non-viral vectors are designed using synthetic molecules that protect the therapeutic gene and permit entry into cells.  Once inside, the genetic cargo initiates salutary changes.

Gene therapy can be administered directly to the patient.  Alternatively, specific cells can be extracted from the patient, treated with gene therapy in the laboratory, and the tailored cells returned to the patient. 

In the U.S., the FDA approved gene therapies for the first time in 2017.  Approved therapies include Kymriah™ for acute lymphoblastic leukemia, Yescarta™ for B-cell lymphoma, and Luxturna™ for RPE65-mediated retinal disease.  Luxturna™ signifies the first FDA approval for an inherited genetic disease.  In addition, there are currently more than 700 gene therapy trials open in the U.S., and many are demonstrating early stage successes. 

This watershed moment in medical science arrives nearly 50 years after scientists first proposed the concept of gene therapy.  Dynamic research programs conducted by laboratories around the world led to these remarkable achievements, and future innovations are maturing in the pipeline.  Gene therapy strives to offer hope, improve outcomes, and transform medicine.