Skip to content
AlternativeMed

Gene Editing and CRISPR Explained

What gene editing and CRISPR are in plain language, the one approved CRISPR medicine and its evidence, the risks of unintended edits, and why germline editing is different.

Content last updated . This page has not been medically reviewed.

Quick answer
Genome editing, also called gene editing, is a group of technologies that give scientists the ability to change an organism's DNA, adding, removing or altering genetic material at particular places. [1] CRISPR-Cas9 is the best-known example. It was adapted from a bacterial immune system. [1] This page explains the idea and the evidence. It gives no laboratory methods, sequences or instructions, and none belong in a wellness setting.

Field, tool and product are different things

  • Genome editing is the field. CRISPR-Cas9 is one tool in it. A therapy is a specific product that uses a tool for a specific condition.
  • Gene editing changes DNA already in the cell, whereas classic gene therapy introduces new genetic material. [2] The pages Gene Therapy vs Gene Editing and Gene Addition and Gene Therapy Explained compare them.
  • MedlinePlus notes that genome editing is used in cells and animal models in research labs to understand diseases, and that scientists are still working to determine whether this approach is safe and effective in people. [1] One approved product is described next.

Somatic and germline editing

Most edits in medicine are in somatic cells, meaning cells other than egg and sperm cells, and are not passed on. Edits to egg, sperm or embryo cells could be passed to future generations. MedlinePlus states that, based on ethics and safety concerns, germline and embryo editing are currently illegal in the United States and many other countries. [1] Laws change and this is not legal advice. See Somatic vs Germline Interventions and Ethics.

What is still investigational

A 2024 review counts scores of CRISPR, base and prime editing clinical trials across phases 1 to 3, in both in vivo and ex vivo approaches. [9] A registered trial does not show a treatment works. Newer tools are covered in Base Editing and Prime Editing.

Cost and access

A 2024 Nature article states that genetic therapies are the most expensive drugs on the market, with list prices exceeding US$4 million per patient. [10] See Gene-Therapy Access and Cost.

Frequently asked questions

Is CRISPR a cure?

One CRISPR-based medicine is approved for specific blood disorders. In a single-group trial most evaluable participants with sickle cell disease had no severe pain crises for at least 12 months. [6] Long-term outcomes are still being followed, and the EU authorisation is conditional. [5]

Is gene editing legal for people?

Approved medicines can be used under their labels. Editing egg, sperm or embryo cells is described by MedlinePlus as illegal in the United States and many other countries. [1] This is not legal advice.

Can CRISPR make mistakes?

Yes. Unintended off-target and on-target changes can occur and are a recognized safety concern. [7]

Is CRISPR the same as gene therapy?

They overlap but differ: editing changes existing DNA while classic gene therapy adds new genetic material. [2]

Does a clinic offering CRISPR mean it is approved?

No. See Medical Tourism for Unproven Treatments.

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.

How to read the evidence labels

Labels used on this page: approved medicine (a regulator approved a named product for a named use), investigational (still being tested), and preclinical (cells or animals only). See How We Label Evidence in Specialty Topics.

The approved example: Casgevy
In December 2023 the FDA described Casgevy as the first FDA-approved therapy using CRISPR/Cas9. The patient's own blood stem cells are modified by genome editing outside the body and transplanted back, where they increase production of fetal hemoglobin. [3]

What the regulators say (read 2026-10-22).


  • US FDA: the product page lists indications for sickle cell disease with recurrent vaso-occlusive crises and transfusion-dependent beta-thalassemia, with one listing for patients aged 2 years and older and another for patients aged 12 years and older. [4]

  • European Medicines Agency (EU): used in patients 12 years and older with beta thalassaemia needing regular transfusions or severe sickle cell disease with recurrent painful crises, under a conditional authorisation granted 9 February 2024, which means the company must provide additional evidence. [5]

What the trial showed (human, single group, open label). In a phase 3 study of 44 people aged 12 to 35 with sickle cell disease, 29 of the 30 who could be evaluated (97%; 95% CI 83 to 100) had no severe pain crises for at least 12 consecutive months. There was no comparison group; results were compared with an assumed 50% response. Treatment included chemotherapy-type conditioning with busulfan, and the safety profile was consistent with that conditioning and stem-cell transplantation. No cancers occurred in the follow-up reported, median 19.3 months. [6] The editing is only part of the experience: conditioning and a hospital transplant are required.

Side effects. The FDA lists low platelets and white blood cells, mouth sores, nausea and pain among the most common. [3] The EMA notes a theoretical risk of cancer from unintended changes in genetic material, with no such cases seen so far, and a risk of bleeding from low platelets. [5]

Risks specific to editing
Editing can cause unintended off-target and on-target changes, including small insertions or deletions and larger structural changes such as translocations, inversions and large deletions. [7] In one animal study in zebrafish (preclinical, not a human result), structural variants made up 6% of editing outcomes and some unintended changes were passed to offspring. [8] Researchers therefore test for such effects before clinical use. See Off-Target Effects, Durability and Long-Term Monitoring.
Safety note
Gene editing is not available as a do-it-yourself product. See DIY Gene-Therapy Claims and Unapproved Clinics and Medical Tourism for Cell Therapies. People with sickle cell disease or beta-thalassemia should discuss options with their hematology team.
References
  1. MedlinePlus Genetics, What are genome editing and CRISPR-Cas9?. Read 2026-10-22.
  2. MedlinePlus Genetics, What is gene therapy?. Read 2026-10-22.
  3. US FDA, FDA Approves First Gene Therapies to Treat Patients with Sickle Cell Disease (8 Dec 2023). Read 2026-10-22.
  4. US FDA, CASGEVY product page. Read 2026-10-22.
  5. European Medicines Agency, Casgevy EPAR. Read 2026-10-22.
  6. Frangoul H et al. Exagamglogene Autotemcel for Severe Sickle Cell Disease. N Engl J Med 2024. Read 2026-10-22.
  7. Beyond the promise: evaluating and mitigating off-target effects in CRISPR gene editing for safer therapeutics. Front Bioeng Biotechnol 2023. Read 2026-10-22.
  8. CRISPR-Cas9 induces large structural variants at on-target and off-target sites in vivo that segregate across generations. Nat Commun 2022. Read 2026-10-22.
  9. Five Years of Progress in CRISPR Clinical Trials (2019-2024). CRISPR J 2024. Read 2026-10-22.
  10. A roadmap for affordable genetic medicines. Nature 2024. 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.