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What is gene therapy, and how does it work?
Many diseases come from a single gene that is missing, broken, or overactive. Gene therapy aims to correct that instead of treating the symptoms. There are three main approaches. Gene addition delivers a working copy of the gene, usually inside a harmless modified virus called a vector, most often an adeno associated virus (AAV). Gene silencing turns down a harmful gene. Gene editing, using tools like CRISPR, cuts and repairs the DNA itself. The therapy can be given directly into the body, as an infusion or an injection into the eye or spinal fluid, or done outside it: stem cells are collected, modified in a lab, and returned, which is how sickle cell gene therapies work.
Approved examples show the range. Luxturna (2017) restores some vision in a rare inherited blindness. Zolgensma (2019) treats spinal muscular atrophy in infants with a single infusion. Hemgenix (2022) lets many people with hemophilia B stop regular factor infusions. Casgevy (December 2023) was the first CRISPR based medicine, for sickle cell disease and beta thalassemia. Most trials today are in rare genetic diseases, inherited eye and blood disorders, and neurological conditions, with growing work in more common diseases like heart failure and Parkinson's. Our article on the future of gene therapy in clinical trials goes deeper.
Types of gene therapy clinical trials
Rare inherited disease trials. The core of the field: muscular dystrophies, spinal muscular atrophy, inherited retinal diseases, hemophilia, sickle cell disease, metabolic disorders, and hundreds of ultra rare conditions. Many enroll children, some enroll infants identified by newborn screening before symptoms appear.
Gene editing trials. CRISPR and newer editors tested in blood disorders, liver diseases, high cholesterol, and hereditary angioedema, including trials that edit genes directly inside the body rather than in cells outside it.
Neurological trials. Gene therapies delivered to the brain or spinal fluid for Parkinson's disease, drug resistant epilepsy, Huntington's disease, ALS, and childhood neurological disorders.
Common disease trials. A newer wave: gene therapies for heart failure, osteoarthritis, hearing loss, and wet macular degeneration, aiming to replace ongoing injections or pills with a one time treatment.
Long term follow up studies. Regulators require years of monitoring after gene therapy. These studies enroll people who already received a gene therapy in an earlier trial and track safety and durability.
Natural history studies. Before a gene therapy can be tested, researchers need to know how a rare disease progresses untreated. These enroll people with the condition, give no treatment, and often become the comparison group for later trials.
How much does gene therapy cost?
Approved gene therapies are the most expensive medicines in the world, from roughly 2.1 million dollars (Zolgensma) to 4.25 million (Lenmeldy) for a one time treatment. Insurers increasingly cover approved uses because the alternative is decades of care. In a clinical trial, the gene therapy itself is typically provided at no cost to the participant.
Who can participate in gene therapy trials?
Almost every gene therapy trial requires a confirmed genetic diagnosis, usually a specific mutation identified by genetic testing, so a test report is the first thing to have. Many enroll a narrow age range, often children, because treating before damage accumulates works best. Studies frequently exclude people who already have antibodies against the viral vector from a past infection, which is checked with a blood test at screening, and people with significant liver disease. Trials for common conditions have broader medical criteria. Natural history and long term follow up studies often have the widest doors and welcome families early. Eligibility always varies by study.
Do gene therapy trial participants get paid?
Some studies offer compensation for time and travel, and study related care, including the gene therapy itself and required monitoring, is typically provided at no cost to participants. Because gene therapy trials often involve travel to a specialized center, many sponsors cover travel and lodging. Compensation varies by trial and is always described during the informed consent process before you agree to anything.
Curious whether clinical trials pay participants? Here's how compensation actually works.
How to enroll in a gene therapy clinical trial
Identify your trial. Use the filters to combine the condition with gene therapy. Titles usually name the gene or disease and the approach, such as "AAV gene therapy," "gene editing," or "long term follow up."
Check the location and travel support. Gene therapy trials run at a small number of specialized centers and may require several visits or a hospital stay. The study details say whether travel and lodging are covered.
Complete the health profile. Click "Get started" to begin the 5-step application. Have three things ready: the genetic test report showing the diagnosis, the age of the person being enrolled and how the condition has progressed so far, and any prior treatments, including earlier gene therapies.
Submit the application. A study coordinator reviews it and contacts you. Nothing is decided until you have gone through informed consent, which for gene therapy covers long term follow up as well as immediate risks, and participation is voluntary at every step. For children, a parent or guardian consents, and older children are asked for their own agreement.