Get to Know the Different Types of Gene-Based Therapies

There are several types of therapies that aim to treat diseases by using genes—and gene replacement therapy is just one type. These approaches replace a nonworking or missing gene, change how your existing genes act, or introduce modified cells into your body.

Let’s take a closer look at the most common types of gene-based therapies.

A missing or nonworking gene and a new working copy of the gene

Gene replacement therapy

Gene replacement therapy gives the cells a new, working copy of the missing or nonworking gene.

This gene is created in a laboratory and then packaged in a delivery vehicle called a vector. This vector carries the gene into the nucleus of specific cells. Once there, the gene may become part of the cell’s DNA, or it may stay separate. Either way, it starts to make the protein that’s missing or in short supply. When the vector is no longer needed, it is eliminated from the body.

Vector entering a cell

Gene replacement therapy has been an area of study in humans since 1989. It has taken nearly 30 years for the first gene replacement therapy to be approved by the Food and Drug Administration (FDA) for use in people outside of a clinical study. In late 2017, a gene replacement therapy was approved for the first time to treat a rare, inherited form of vision loss.

Many gene-based therapies are currently being investigated in clinical trials.

Gene editing

Gene editing

This technique inserts, removes, changes, or replaces specific pieces of a person’s existing DNA.

To treat diseases, scientists are exploring ways to edit pieces of DNA at precise spots along the gene. The goal of gene editing is to change the existing gene and correct mutations where they occur.

Gene editing is a lot like editing a movie: different scenes or images (ie, genes) can be added, removed, or put into a different order.

While several types of editing have been developed, the most common is called clustered regularly interspaced short palindromic repeats, or CRISP-R, which is a lot easier to say. It is used to change DNA sequences and gene function.

Gene editing has been studied since the 1980s. Clinical trials with many different kinds of genetic diseases are ongoing to further investigate its safety and efficacy. There are no FDA-approved treatments available at this time.

CAR-T cell therapy

CAR-T cell therapy

CAR-T stands for chimeric antigen receptor (CAR) T-cell therapy. It is a type of cell therapy that is used with gene-based therapies, but it is not a type of gene-based therapy by itself.

CAR-T cell therapy involves changing a person’s own immune cells to recognize and fight cancer cells inside the body. Here’s how it works:

CAR-T cell therapy process diagram
  1. T cells, a type of immune cell, are taken from a person’s blood.
  2. Then, in the laboratory, gene replacement therapy is used to add a new gene to T cells. This new gene adds a special receptor, called a chimeric antigen receptor (CAR), to T cells to make CAR-T cells. CAR-T cells are able to bind to and attack certain cancer cells.
  3. Large numbers of the CAR-T cells are made in the laboratory, and once a sufficient amount has been produced, the cells are put back into the body to fight certain cancers.

CAR-T cell therapy is just one type of cell therapy. Because of all the different types of cells that may be used, cell therapy has the potential to treat many different types of conditions such as cancer, autoimmune diseases, and neurologic disorders. It may also be used to rebuild damaged cartilage in joints, repair spinal cord injuries, and strengthen a weakened immune system.

A question mark inside a magnifying glass

What’s the difference?

Here is a quick summary of the differences between gene replacement therapy, gene editing, and CAR-T cell therapy.

Gene replacement therapy Gene editing CAR-T cell therapy
Places a new, working gene inside the nucleus of the cell A checkmark Sometimes A checkmark
Uses viral vectors to deliver genes into cells A checkmark Sometimes A checkmark
Directly edits or changes DNA to correct its code A checkmark
Removes cells from the body for modification A checkmark
Is being studied in human clinical trials A checkmark A checkmark A checkmark
Is a treatment mechanism with FDA approval A checkmark A checkmark

Check your understanding of gene replacement therapy

Q&A

How does gene replacement therapy differ from gene editing?

Gene replacement therapy differs from gene editing in that it does not directly change, or edit, a person’s DNA. Instead, a vector delivers a new, working gene into the nucleus of the cell where it can make the protein the body needs. Both methods offer great promise in the treatment of genetic diseases and are the result of decades of research in the laboratory, in animal models, and in clinical trials with humans.

Discover the history of gene-based therapies.