Watch this video for a quick introduction to genetic therapies. Medical Animation Copyright © 2020 Nucleus Medical Media, All rights reserved.
Genetic therapies are approaches that treat genetic disorders by providing new DNA to certain cells or correcting the DNA. Gene transfer approaches, also called gene addition, restore the missing function of a faulty or missing gene by adding a new gene to affected cells. The new gene may be a normal version of the faulty gene or a different gene that bypasses the problem and improves the way the cell works.
Genome editing is a newer approach that allows precise correction or other targeted changes to the DNA in cells to restore a cell’s function. Genome editing can do the following:
- Remove a stretch of DNA that causes a disease
- Turn off a gene to prevent it from making a harmful protein
- Turn on a gene or instruct a cell to make more of a needed protein
- Correct a mutated gene
Gene transfer or genome editing treatments can directly modify the cells in your body, or your cells can be collected and treated outside of your body and then returned to you. For example, a doctor can removecells or bone marrow cells from your body, modify their DNA, and then re-introduce the cells to your body.
The only genetic therapies that are currently approved by the U.S. Food and Drug Administration (FDA) are for a rareeye condition, as well as certain types of cancer. Genetic therapies that are in development could treat or cure other inherited disorders; treat other cancers; or treat infections, including HIV.
Explore this Health Topic to learn more about genetic therapies, our role in research and clinical trials to improve health, and where to find more information.
How It Works - Genetic Therapies
Genetic therapies may use gene transfer or genome editing approaches to change the DNA in a patient’s cells to treat a condition.
- Genetic Therapies
Gene transfer introduces an additional gene into specific cells. This gene may stay as an extra piece of DNA in the cell or be inserted into the cell’s ownand thus become part of the cell’s own DNA.
A molecular package called acarries the gene to the cell nucleus, which is the central part of the cell where DNA is packaged in chromosomes. Vectors are created in the laboratory, often from that have been modified to remove viral genes that cause disease and to carry a treatment gene.
Once the gene is inside the nucleus, the cell will start to make the critical protein needed for the cell to work properly. The new proteins make up for missing or faulty proteins and are meant to improve health for people who receive genetic therapies.
- Genetic Therapies
Watch this video to learn about how genome editing works. Medical Animation Copyright © 2020 Nucleus Medical Media, All rights reserved.
Genome editing introduces components that function together into cells. One component is a protein that cuts DNA, similar to a pair of molecular scissors. Another component is a guidethat can stick to DNA at specific sites. When the guide molecule sticks to an area of faulty DNA, the scissors protein attaches to the guide molecule, and cuts out the faulty DNA.
After the target DNA is cut, several things can happen. The cell may leave behind a gap, return the DNA to its original state, or fill in this gap with the corrected DNA. The cell can fill in the corrected DNA if it has a template DNA to direct the cell to rebuild a healthier version of the DNA that was removed. Therefore, sometimes a small piece of template DNA is introduced as a third component. This DNA is a corrected version of the faulty DNA, and it is used to rebuild the DNA correctly after it is cut open.
Who May Benefit - Genetic Therapies
In the future, genetic therapies may be used to prevent, treat, or cure certain inherited disorders, such as cystic fibrosis, alpha-1 antitrypsin deficiency, hemophilia, beta thalassemia, and sickle cell disease. They also may be used to treat cancers or infections, including HIV.
Genetic therapies that are currently approved by the FDA are available for people who have Leber congenital amaurosis, a rare inherited condition that leads to blindness. CAR T-cell therapy is FDA approved for people who have blood cancers, such as acute lymphoblastic leukemia (ALL) and diffuse large B-cell lymphoma.
What to Expect During Treatment - Genetic Therapies
Genetic therapies are still in the early stages of research, development, and clinical trials, but researchers already know a lot about how they may work as a treatment. For example, if you participate in a clinical trial or receive genetic therapy in the future, treatment may be provided in one of two ways. Your cells may be directly modified inside your body, or your cells may be collected and modified outside your body and then returned to you. The method may depend on your condition and what organ or types of cells in your body need to be treated.
Treatments for blood and immune conditions
- Genetic Therapies
If you have a blood or immune condition, the doctor may take blood from your veins or bone marrow from your hip bone to be modified in a laboratory with genetic therapy. Blood and bone marrow contain hematopoietic, which produce other key cells that make up the blood and immune system.
In the laboratory, scientists may use either gene transfer or genome editing to change the sample of stem cells provided by you. The modified cells are returned to your body through an intravenous (IV) line in one of your blood vessels. This procedure is called cell-based therapy or a blood and bone marrow transplant. The altered hematopoietic stem cells will produce healthy blood or immune cells.
Genetic therapies for sickle cell disease are examples of how this approach is being developed. Currently, a blood and bone marrow transplant of stem cells from a relative or an unrelated well-matched donor can cure sickle cell disease, but many patients do not have a well-matched donor available. Genetic therapies that modify a person’s own hematopoietic stem cells may provide a cure for people who do not have a well-matched donor. Modified hematopoietic stem cells can be injected into the blood, then the cells travel in the bloodstream to the marrow spaces inside the bones. Once inside the bone marrow, the cells can produce healthy red blood cells that do not sickle. Watch the video below to learn more about how genome editing is being tested for sickle cell disease.
This animation discusses how genome editing may be used to treat or cure sickle cell disease. Medical Animation Copyright © 2020 Nucleus Medical Media, All rights reserved.
Treatments for organs or tissues
- Genetic Therapies
Sometimes, genetic therapies are needed to alter cells that cannot be easily removed from the patient for treatment in the laboratory. Researchers are still working on ways to deliver the genetic therapy for these conditions. The methods being studied include IV infusion into the bloodstream, injection directly into an organ, and other ways to directly deliver the therapy into the affected tissues.
One condition that could be treated this way is hemophilia B. Hemophilia is caused by a faulty gene that prevents production of a protein necessary to clot the blood after an injury. Genetic therapy that is being developed for Hemophilia B involves infusing a vector carrying the normal clotting factor gene into the bloodstream. The vector then reaches liver cells to produce the clotting factor needed for better health.
What Are the Risks? - Genetic Therapies
Genetic therapies hold promise to treat many diseases, but they are still new approaches to treatment and may have risks. Potential risks could include certain types of cancer, allergic reactions, or damage to organs or tissues if an injection is involved.
Recent advances have made genetic therapies much safer. Better safety has resulted in the FDA approving some gene transfer therapies for clinical use in the United States. There have been a few clinical studies on genome editing, but the approach is much newer than gene transfer. Researchers are still studying the risks.
The National Institutes of Health, which includes the NHLBI, does not perform or fund studies on genome editing targeting sperm, eggs, or embryos in humans. These changes would be passed on to the patient’s children and could have unanticipated effects.
Research for Your Health
Improving health with current research
- Genetic Therapies
Learn about some of the ways we continue to translate current research into improved health for people using genetic therapies. Research on this topic is part of the NHLBI’s broader commitment to advancing blood disorders and blood safety scientific discovery.
- Accelerating Cures for Patients Who Have Sickle Cell Disease. The Cure Sickle Cell Initiative is an NHLBI-led collaborative research effort to develop genetic therapies for patients who have sickle cell disease. The goal is to have these genetic therapies ready to safely use in clinical research in 5 to 10 years. The patient-focused Initiative brings together academic and private sector researchers, patients, providers, advocacy groups, and others as it supports research, education, and community engagement activities.
- Supporting Safe Manufacturing of Cell-based Therapies. The NHLBI’s Production Assistance for Cellular Therapies (PACT) supports translational research on cellular and genetic therapies by increasing the capacity to manufacture cell products that follow cGMP (current Good Manufacturing Practices) regulations. PACT offers education and resources through its five cell processing facilities and a coordinating center that support activities such as safety testing, product shipment, and design of clinical testing protocols.
- Addressing Issues in Blood and Marrow Transplantation. The Blood and Marrow Transplant Clinical Trials Network (BMT CTN) was established to conduct large multi-institutional clinical trials to understand possible treatment approaches in blood and marrow transplants. In the United States, nearly 21,000 patients receive blood or marrow transplants annually, mainly for rare blood disorders.
- Supporting Development of Genome Editing Tools. The NHLBI is helping to manage The Somatic Cell Genome Editing Program, a program supported by the NIH Common fund that aims to develop quality tools to perform effective and safe genome editing in human patients. These research tools will be made widely available to the research community to reduce the time and cost required to develop new therapies.
- Combining New Approaches for Genome Editing in Sickle Cell Disease. NHLBI-funded research used a new genome editing technique, called CRISPR-Cas9, to remove the sickle cell mutation in stem cells in the laboratory. The researchers then used a virus vector to add a corrective gene to the stem cells. In preliminary laboratory tests, the red blood cells derived from the corrected stem cells produced almost all normal hemoglobin and very little sickle hemoglobin. This genetic therapy approach may hold promise for sickle cell disease, but more research is needed. Visit Experimental gene-editing approach holds promise for curing sickle cell disease for more information.
Advancing research for improved health
- Genetic Therapies
In support of our mission, we are committed to advancing research on genetic therapies in part through the following ways.
- We perform research. Our Division of Intramural Research, which includes investigators in our Hematology Branch and Sickle Cell Program, is actively engaged in research on genetic therapies. Researchers in NHLBI’s Cellular and Molecular Therapeutics Laboratory are pursuing strategies to correct the underlying mutation that causes sickle cell disease by using newly developed genome editing approaches.
- We fund research. The research we fund today will help improve our future health. Our Division of Blood Diseases and Resources (DBDR) and Division of Cardiovascular Sciences oversee much of the research on genetic therapies we fund, helping us advance new genetic therapies for noncancerous blood disorders. The DBDR’s Gene Therapy Resource Program supports translational research on investigational genetic therapies to clinical testing by aiding the development of vectors, assisting with regulatory affairs, and funding genetic therapy clinical trials. Our Division of Lung Diseases also supports research that includes genetic therapies for inherited lung diseases such as cystic fibrosis. Search the NIH RePORTer to learn about research on genetic therapies that NHLBI is funding.
- We stimulate high-impact research. Our Cure Sickle Cell Initiative is a patient-focused effort that engages investigators to develop genetic therapies for patients who have sickle cell disease. The NHLBI Strategic Vision highlights ways we may support research over the next decade, including new efforts for genetic therapies.
Learn about other exciting ways we are advancing research to improve lives.
- Genetic therapies for alpha-1 antitrypsin (AAT) deficiency. The NHBLI continues to support research on the development of innovative methods to effectively deliver genetic therapy to treat the inherited lung disease, AAT deficiency. This work will build on previous work developing viral vectors that showed promise in earlier studies.
- Genetic therapies for congestive heart failure. The NHLBI is supporting research into genes that may be useful for treating congestive heart failure and heart disease through gene transfer approaches. Some of this research aims to identify genes that might be ready to start testing for genetic therapy approaches.
- Genetic therapies for cystic fibrosis. The NHLBI is supporting research on new genetic therapies to treat cystic fibrosis. New gene transfer virus vectors are being studied that may be better at delivering a corrected gene to lung cells. Researchers are also working on better methods to improve their genetic therapies in the laboratory before moving to clinical trials. Other research has shown success with genome editing that can fix the mutation in the gene that leads to cystic fibrosis using unique vectors that are not viruses. Researchers hope to improve these methods to use in clinical trials. Visit Genome editing for cystic fibrosis: A Q&A with Peter Glazer, Ph.D., M.D., for more information.
- Genetic therapies for hemophilia. An NHLBI-supported study is testing the safety and success rate of genetic therapies in people who have hemophilia B. An early study showed promise, finding that almost half of the men who received genetic therapy could stop their regular treatment with clotting factor replacement therapy.
- Improving genetic therapy approaches. Gene transfer into stem cells in bone marrow transplants is often not as successful as expected, so the NHLBI is supporting research into improving vectors and transplant techniques in the laboratory. The NHLBI is also funding research that will test new vectors for unique genome editing approaches for treating a range of diseases.
Participate in NHLBI Clinical Trials
We lead or sponsor many studies relevant to genetic therapies using gene transfer or genome editing. See whether you or someone you know is eligible to participate in our.
Do you or a child you know have lymphoma?
Do you know a newborn or toddler who has severe combined immunodeficiency?
Are you an adult who has kidney cancer?
After reading our Genetic Therapies Health Topic, you may be interested in additional information found in the following resources.
Related Health Topics
- Genetic Therapies
- Genetic Therapies
- Cystic Fibrosis (National Library of Medicine [NLM], MedlinePlus)
- Genes and Gene Therapy (NLM, MedlinePlus)
- Genetics 101 (NLM, MedlinePlus)
- Hemophilia (NLM, MedlinePlus)
- Learning About Cystic Fibrosis (National Human Genome Research Institute)
- Sickle Cell Disease: What You Should Know (NLM, MedlinePlus)
- What Is Gene Therapy? How Does It Work? (U.S. Food and Drug Administration)