Gene therapy is a medical technique that corrects a genetic problem by modifying a person's genes to treat or cure a disease. It targets the root genetic cause of a disease rather than just the symptoms. Gene therapies are often one-time treatments, though the long-term effectiveness of newer approaches is still being evaluated.

How gene therapy works

Gene therapy can work in several ways by using a carrier, or vector, to deliver genetic material to target cells. The most common vectors are modified, harmless viruses. The genetic material is delivered either inside or outside the body:
In vivo (inside the body): The vector is injected directly into the patient's bloodstream or specific tissue.
Ex vivo (outside the body): The patient's cells are removed, modified in a lab, and then returned to the patient.

The main approaches include:
Gene addition: A working copy of a gene is inserted to compensate for a missing or faulty one.
Gene editing: Molecular tools, such as CRISPR-Cas9, are used to make precise changes to the existing DNA to fix a genetic alteration.
Gene silencing: A faulty gene is "turned off" to prevent it from causing disease.

Who is a candidate for gene therapy

People who need gene therapy typically have genetic disorders caused by a single gene mutation. However, current research is exploring its use for more complex diseases caused by multiple genes.
Candidates for gene therapy are chosen through a complex evaluation process by a medical team, including genetic testing to confirm a specific gene mutation. For some therapies, blood or bone marrow cells may be extracted and modified.

Diseases treated with gene therapy

Gene therapy has been successfully used to treat specific conditions and is being researched for many others.

FDA-approved gene therapies include treatments for:

* Inherited blood disorders: Sickle cell disease and beta-thalassemia.
* Inherited eye diseases: Leber congenital amaurosis.
* Neuromuscular disorders: Spinal muscular atrophy (SMA) and Duchenne muscular dystrophy (DMD).
* Certain types of cancer: CAR T-cell therapy for lymphomas and leukemia.
* Genetic skin disorders: Dystrophic epidermolysis bullosa.

Gene therapy is also being studied in clinical trials for:

* Heart disease: Including ischemic heart disease, heart failure, and arrhythmias.
* Other genetic disorders: Such as cystic fibrosis and hemophilia.
* Infectious diseases: Including HIV and hepatitis.
* Neurodegenerative diseases: Like Alzheimer's disease and Parkinson's disease.