Gene Therapy vs Gene Editing

Gene therapy usually adds or replaces genetic material; gene editing changes DNA already in the cell. This page compares the two, with one approved example, risks and what remains unproven.

Content last updated October 22, 2026. This page has not been medically reviewed.

Quick answer

The two terms overlap, which causes confusion. Gene therapy is the broader medical idea of treating disease by changing genetic material or cell biology. Gene editing is one set of tools that can be used within it. This page compares them, describes one approved product of each kind, and makes no claim that either is better. It is information only; it does not describe how any procedure is carried out. Evidence labels used: approved medicine, established, investigational, insufficient evidence.

Definitions

Gene therapy. The FDA says it modifies a person's genes to treat or cure disease, for example by replacing a disease-causing gene with a healthy copy, inactivating a gene, or introducing a new or modified gene. [1] Early forms, called gene transfer or gene addition, introduce a non-faulty gene copy. [2]
Gene editing (genome editing). Instead of introducing new genetic material, it introduces molecular tools that change the existing DNA in the cell. [2] In CRISPR-Cas9, a guide RNA finds the target sequence and the Cas9 enzyme cuts the DNA at that location. [3]
Relationship. MedlinePlus describes genome editing as a newer technique that may potentially be used for gene therapy. [4] The FDA also lists human gene editing among types of gene therapy products. [1]

See Gene Addition and Gene Therapy Explained and Gene Editing and CRISPR Explained.

The difference at a glance

	Gene addition / gene transfer	Gene editing
Basic idea	Add a working gene copy or a new gene [2][1]	Alter DNA already in the cell, at a chosen spot [2][3]
Delivery	A vector, often a modified virus [4]	Editing tools also need delivery; viruses and nanoparticles are used [4]
US example (FDA-approved)	Lyfgenia, a cell-based gene therapy that uses a lentiviral vector to modify blood stem cells [5]	Casgevy, the first FDA-approved therapy to use CRISPR/Cas9 [5]
Known risks	A viral vector can trigger a dangerous immune response; some vectors can cause errors that lead to cancer [4]	Whether the approach is safe and effective in people is still being worked out for most uses [3]
Regulator	FDA, as biological products requiring a biologics license application [1]	Same pathway when used as a therapy [1]

Frequently asked questions

Is gene editing a type of gene therapy?

The terms overlap. MedlinePlus says genome editing may potentially be used for gene therapy, and the FDA lists human gene editing among gene therapy product types. [4][1]

What is the main difference?

Gene therapy often adds genetic material, while gene editing changes DNA already in the cell. [2]

Is any gene-editing treatment approved?

In the US, the FDA says Casgevy is its first approved therapy using CRISPR/Cas9. [5] Its indications are limited to specific blood disorders. [6]

Are gene therapies safe?

They carry risks that include immune reactions and, with some vectors, cancer-causing errors. [4] Each approved product has its own risks, which are in its label.

More details: evidence, limits and cautions

The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.

One approved example in detail: Casgevy

The FDA approved Casgevy in December 2023 for sickle cell disease in patients 12 and older with recurrent vaso-occlusive crises. [5] The FDA product page (current as of July 2026) lists its indications as sickle cell disease with recurrent vaso-occlusive crises and transfusion-dependent beta-thalassemia, for patients aged 2 and older. [6] The patient's own blood stem cells are edited with CRISPR/Cas9 and returned. [5] Before treatment, the patient must undergo high-dose chemotherapy that clears bone marrow. [5] This is a serious medical procedure and not a general model for editing other conditions. Evidence label: approved medicine (FDA, for those indications only, read 2026-10-22).

Approval of Casgevy does not mean other gene-editing products work or are safe, and the approval does not cover other diseases.

Risks and limits

MedlinePlus notes that early gene therapy studies showed serious risks such as toxicity, inflammation and cancer, and that newer techniques aim to reduce dangerous immune reactions. [7]
For genome editing, scientists are still determining whether the approach is safe and effective in people for most uses. [3]
Nothing in the sources read supports do-it-yourself gene therapy or editing, or treatments sold outside regulated trials. See DIY Gene-Therapy Claims and Gene-Therapy Access and Cost.

Rules differ by country. This page describes US FDA statements only and is not legal advice.

References

FDA, What is Gene Therapy? (current as of 07/25/2018). Read 2026-10-22.
MedlinePlus Genetics, What is gene therapy?. Read 2026-10-22.
MedlinePlus Genetics, What are genome editing and CRISPR-Cas9?. Read 2026-10-22.
MedlinePlus Genetics, How does gene therapy work?. Read 2026-10-22.
FDA press announcement, first gene therapies for sickle cell disease, 8 December 2023. Read 2026-10-22.
FDA, CASGEVY product page (current as of 07/02/2026). Read 2026-10-22.
MedlinePlus Genetics, Is gene therapy safe?. Read 2026-10-22.

Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.