November 6, 2026 Authors : Leonor Rodrigues and Joana Simões (pharmacists ) What is gene therapy? Gene therapy is an innovative medical approach that aims to treat, prevent or modify the course of certain diseases by altering the genetic material within cells . It involves introducing, removing or modifying genes within a patient’s cells. Genes contain the information required for the body to function normally, and changes in these genes can cause a range of diseases. By acting directly on the genetic cause of disease, gene therapy can correct genetic alterations rather than simply treating the symptoms. Which diseases can be treated with gene therapy? Gene therapy is already part of clinical practice for certain specific diseases, including: Rare genetic diseases , such as hemophilia A and hemophilia B; Certain types of cancer , such as acute lymphoblastic leukemia and diffuse large B-cell lymphoma; Blood disorders , such as sickle cell disease and beta-thalassemia; Inherited eye disorders , such as Leber congenital amaurosis; Rare metabolic diseases , such as cerebral adrenoleukodystrophy and aromatic L-amino acid decarboxylase (AADC) deficiency; Neuromuscular diseases , such as spinal muscular atrophy. Most gene therapies currently approved are intended to treat rare and serious diseases. In some cases, a single administration may provide long-lasting benefits, although the duration of the response varies depending on the disease and the treatment. Despite advances in this area, access to gene therapy remains limited because of its high cost and the strict clinical criteria governing its use . Nevertheless, this is a rapidly evolving field, with new therapies currently under development and evaluation. How does gene therapy work? In simple terms, gene therapy can work through different mechanisms: Replacing an altered gene with a functional copy; Inactivating a gene that causes disease; Introducing or modifying a gene so that cells can perform their function correctly. Vectors are used to deliver genetic material into cells. These vectors are generally viruses that have been modified in the laboratory so that they are safe and unable to cause disease. The purpose of using vectors is to deliver genetic material efficiently to the target cells, allowing them to produce the intended therapeutic effect. How is gene therapy administered? Depending on the disease and the therapy used, gene therapy can be administered in two ways: In vivo , where the vector is administered directly into the body, for example by injection or intravenous infusion; Ex vivo , where cells are collected from the patient, such as blood or bone marrow cells, modified in the laboratory and then infused back into the patient. The choice of strategy depends on the type of disease, the tissue to be treated and the technology used. What are the benefits of gene therapy? In some patients, gene therapy may: Act directly on the cause of the disease; Significantly improve symptoms and quality of life; Reduce or eliminate the need for ongoing treatment; In certain situations, provide long-lasting clinical benefits after a single administration. However, outcomes vary between patients and depend on the disease being treated, the therapy used and other individual factors. Does gene therapy have risks? Before being approved for clinical use, gene therapies are rigorously evaluated in clinical trials to determine their safety, efficacy and benefit-risk balance . Like any treatment, gene therapy may be associated with certain risks, including: Immune system reactions; Allergic reactions; Unexpected effects on treated cells; A limited or variable duration of the therapeutic effect; Complications related to administration, depending on the route used. For this reason, these treatments are provided at specialist centers and require careful clinical monitoring . Does the patient have an important role? Patient involvement is essential to the success of the treatment. It is important to: Understand the treatment and discuss any questions or concerns with the healthcare team; Follow the clinical monitoring and follow-up plan; Inform the healthcare team of any symptoms or possible adverse reactions. A new era in medicine Gene therapy represents one of the most promising areas of modern medicine. By acting directly on the cause of certain diseases, it offers new treatment possibilities for people who, until only a few years ago, had very limited options. Although challenges remain regarding access, cost and the need for long-term follow-up, continued developments in this field suggest that gene therapy will play an increasingly important role in clinical practice . Sources Encina Silva G. Avances en terapia génica en humanos: algunos conceptos básicos y un recorrido histórico. Rev Med Cli Las Condes 2022;33:109-18. Euro GCT. Terapia génica . Sociedad Española de Farmacia Hospitalaria. Decálogo de terapia génica en los servicios de farmacia hospitalária . US Food and Drug. How gene therapy can cure or treat diseases . US Food and Drug. What is gene therapy? The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item. English translation generated with AI and reviewed by the editorial team.
