What is Sickle Cell Anaemia?

Sickle Cell Anaemia is a blood disorder regarding the change of red blood cells' shape, becoming misshapen into a sickle shape. 

This causes the red blood cells to struggle to transport oxygen around the body, causing symptoms such as chronic pain, stroke, lung problems, eye problems, infections, and kidney disease (NHS, 2019).

[ Link to NHS sickle cell page]

What is the new treatment?

The newly approved treatment, developed by Vertex Pharmaceuticals, is named Casgevy and utilises the CRISPR-Cas9 mechanism to modify the patient's stem cells (Vertex Pharmaceuticals Newsroom, 2023). Casgevy uses two methods for this modification.

The first approach replaces the mutation with a functional gene using a donor DNA template. 

The second mechanism removed the mutated gene via a gene knockout in the Haemoglobin called the β-globin gene, specifically in the BCL11A gene. This then switches off the gene-producing adult haemoglobin and replaces it with fetal haemoglobin (Synthego, 2019; Haydar Frangoul et al., 2024).

Image : (Greenfieldchemical.com, 2024)

Treatment Outline :

Step 1:

Pre-treatment with mobilisation drugs allows blood stem cells to move from the bone marrow into the bloodstream, where they can be extracted and separated into different cell types. Some cells are left untreated; these are called rescue cells and are reserved for use in cases of adverse reactions.

Step 2:

The collected stem cells are sent to manufacturers for genetic engineering using  CRISPR-Cas9 and then produced into CAGEVY. This may take up to 6 months.

Step 3:

Before the transplant, the patient will receive conditioning medicine, which removes the remaining cells from the bone marrow. This causes blood cell levels to drop drastically, so the patient must remain in the hospital for monitoring.

Step 4:

The transfusion is administered intravenously; recovery can take 4-6 weeks, which may vary.

(www.casgevy.com, n.d.)

Images : (Human, 2025), (www.istockphoto.com, n.d.), (Npr.org, 2019), (Kolata and Holston, 2024)

"Researchers concluded there was a ‘functional cure’ in 96.6% of exa-cel trial participants who received it. Clinical trials suggest exa-cel can stop painful and unpredictable sickle cell crises – the most common symptom of sickle cell disease – where blood vessels become blocked, causing severe pain, with experts saying the therapy offers patients a chance of a disease-free life."

(Church, 2025)

The potential negatives of treatment 

Side affects :

The medication before the treatment causes a decrease in white blood cells and platelet count, leading to an increased risk of infection and multiple side effects such as:

  1. increase risk of bleeding.
  2. severe headaches
  3. Abnormal bruising 
  4. Bleeding without injury: such as nosebleeds, bleeding gums, blood in urine and or vomiting/coughing up blood.

A health care professional should be called if ...

  • Fever 
  • chills 
  • or other signs of infection 

(www.casgevy.com, n.d.)

[ Link to Casgevy website to side effect pages ] 

Image:  (www.casgevy.com, n.d.)

How much will it cost ?

Sickle Cell Treatment Cost
Casegevy Treatment £1.65 million

NHS England has struck a deal to access the treatment at a reduced price for taxpayers, enabling it to be offered through the Innovative Medicines Fund, which fast-tracks funding for new medicines (England, 2025).

In the US, patients who have no access to in-state treatment centres, Medicaid agencies would pay for patients to receive the therapies in another state. Between 50% and 60% of sickle cell patients are on Medicaid, according to federal estimates. 

(www.cms.gov, n.d.)

References:

NHS (2019) Diagnosis - Sickle cell disease.  NHS. Available at: https://www.nhs.uk/conditions/sickle-cell-disease/diagnosis/. (Accessed 1 April 2025)

Vertex Pharmaceuticals Newsroom  (2023) Vertex and CRISPR Therapeutics Announce Authorization of the First CRISPR/Cas9 Gene-Edited Therapy, CASGEVYTM (exagamglogene autotemcel), by the United Kingdom's MHRA for the Treatment of Sickle Cell Disease and Transfusion-Dependent Beta Thalassemia Vertex Pharmaceuticals Newsroom.  Available at: https://news.vrtx.com/news-releases/news-release-details/vertex-and-crispr-therapeutics-announce-authorization-first  (Accessed 1 April 2025)

Synthego (2019) The complete guide to understanding CRISPR sgRNA. Available at: https://www.synthego.com/guide/how-to-use-crispr/sgrna
(Accessed 1 April 2025)

Hirsch, F., Lemaitre, C., Chneiweiss, H. and Montoliu, L (2019) Genome Editing: Promoting Responsible Research. Pharmaceutical Medicine, 33(3), pp.187–191.

www.casgevy.com. (n.d.). Patient Information CASGEVYTM (exagamglogene autotemcel). Available at: https://www.casgevy.com/. (Accessed 1 April 2025)

Church, E  (2025) ‘Functional cure’ for sickle cell disease now offered on NHS Nursing Times.  Nursing Times. Available at: https://www.nursingtimes.net/haematology/functional-cure-for-sickle-cell-disease-now-offered-on-nhs-31-01-2025/. (Accessed 1 April 2025)

England, N (2025)  NHS England» Revolutionary gene-editing therapy for sickle cell ‘offers hope of a cure’ for NHS patients. [online] England.nhs.uk. Available at: https://www.england.nhs.uk/2025/01/revolutionary-gene-editing-therapy-for-sickle-cell/. (Accessed 1 April 2025)

www.cms.gov (n.d.) CGT Access Model Frequently Asked Questions  CMS. Available at: https://www.cms.gov/cgt-access-model-frequently-asked-questions. (Accessed 1 April 2025)

Images:

Sickle cell - https://www.istockphoto.com/photo/sickle-cell-anemia-3d-illustration-gm1281522904-379538616

Greenfieldchemical.com (2024) CASGEVYTM: A Paradigm Shift in Sickle Cell Disease Treatment through CRISPR Gene Editing – GreenField Chemical Inc. Available at: https://greenfieldchemical.com/2024/01/05/casgevy-a-paradigm-shift-in-sickle-cell-disease-treatment-through-crispr-gene-editing/.(Accessed 7 May 2025)

Human (2025) Stem Cells Images – Browse 106,798 Stock Photos, Vectors, and Video. Adobe Stock. Available at: https://stock.adobe.com/search?k=stem+cells&asset_id=233726552 (Accessed 30 April 2025)

www.istockphoto.com (n.d.) Crispr Cas9 Stock Photos, Pictures & Royalty-Free Images - iStock.  Available at: https://www.istockphoto.com/photos/crispr-cas9.(Accesed 7 May 2025)

Npr.org  (2019) NPR Choice page. Available at: https://www.npr.org/sections/health-shots/2019/10/10/766765780/after-a-life-of-painful-sickle-cell-disease-a-patient-hopes-gene-editing-can-hel.(Accessed 7 May 2025)

 Kolata, G. and Holston, K (2024) First Day of a ‘New Life’ for a Boy With Sickle Cell.  New York Times  Available at: https://www.nytimes.com/2024/09/16/health/sickle-cell-gene-therapy-kendric-cromer.html .(Accessed 7 May 2025)

www.casgevy.com (n.d.)  Patient Information | CASGEVYTM (exagamglogene autotemcel). Available at: https://www.casgevy.com/.(Accessed 7 May 2025)