Gene therapy: what is it and how does it work?

Gene therapy is an experimental technique that involves the delivery of therapeutic nucleic acid polymers into a patient’s cells to treat or prevent a disease.

What is gene therapy?

Gene therapy is an experimental technique that involves the delivery of therapeutic nucleic acid polymers into a patient’s cells to treat or prevent a disease. Gene therapy has demonstrated clinical benefits in different diseases including cancers and inherited disorders [1]. A defective or missing gene could be present from birth or could mutant over an adults life-time. Once a gene is defecitve it can dirupt how proteins are made leading to different diseases [2].

With the number of cell and gene therapy products in development increasing, bioanalytical methods are playing an important role in ensuring the success of these novel therapies. As potential gene therapies are investigated, it is essential to use bioanalytical methods to quantify the DNA, the vector and the expressed gene moieties to gain a complete understanding of PK, PD and safety.

Gene therapies are uniquely able to target ‘undruggable’ targets, forming the third major drug platform after traditional small and large molecule therapeutics. It is important that the newly introduced gene doesn’t cause an immune response and reaches the correct target. Therefore, bioanalytical techniques have a role to play in accurately evaluating PK/PD and immunogenicity assessment.

How does gene therapy work?

Normally, a healthy copy of a gene is inserted into the cell that is not functioning properly. A vector, which is the carrier, is genetically engineered to deliver the gene into the correct cell. Modified viruses have made for effective vectors as they can target certain cells and deliver the correct gene. For example, adenoviruses introduce their DNA into the nucleus of the cell, but the DNA is not integrated into a chromosome. This is contrasted to retroviruses, which do integrate their genetic material into the chromosome.

The vector can be administered into the patient by injection or intravenously, or alternatively a patient’s cells can be removed and then introduced to the vector in the laboratory before being returned into the patient [1]. The cells are often left in the laboratory to multiply, before being introduced to the patient, where they can continue to multiply and produce the desired effect [2]. Once the vector and gene have been delivered correctly, the cell will now make a functioning form of the protein. Gene therapies can also be used to turn off certain gene that are causing problems.

How does a gene therapy get approval?

Before a gene therapy product can be used in humans it has to be tested for both safety and effectiveness. The US FDA have approved three gene therapy products since August 2017 and two of these reprogram a patient’s own cells causing them to attack cancerous cells. The US FDA is responsible for reviewing these treatments as they thoroughly assess data before clinical trials can take place [2].

What diseases have been helped by gene therapies?

Most gene therapies that are currently up for approval focus on treating cancer or rare inherited genetic disorders. Rare inherited disorders, which are passed along from parents, are assisted by gene therapies as they can add or change the non-functioning gene. The majority of gene therapies have been used to assist inherited diseases, which include: hematology/blood disorders like sickle cell disease, neurological disorders, musculoskeletal diseases, retinal disorders and oncology (blood cancers) [3].


  1. How does gene therapy work? Genetics Home Reference. [Accessed 29 June 2020].
  2. What is gene therapy? How does it work? US Food and Drug Administration. [Accessed 29 June 2020].
  3. Gene therapy basics. American Society of Gene and Cell Therapy. [Accessed 29 June 2020].