Two gene therapies for the treatment of sickle cell disease have been approved by the US Food and Drug Administration.
Casgevy and Lyfgenia are the first cell-based gene therapies for the treatment of sickle cell disease in patients 12 years and older to be granted approval from the FDA. Casgevy, a CRISPR-based gene therapy has already been authorised by the UK medicines regulator (see BioNews 1216) and has now become the first treatment that uses CRISPR-based genome editing to be approved by the US medicines regulator. In contrast to Casgevy, Lyfgenia uses a lentiviral vector to deliver genetic material to the cells.
'Sickle cell disease is a rare, debilitating and life-threatening blood disorder with significant unmet need, and we are excited to advance the field especially for individuals whose lives have been severely disrupted by the disease by approving two cell-based gene therapies today,' said Dr Nicole Verdun, director of the Office of Therapeutic Products within the FDA's Centre for Biologics Evaluation and Research. 'Gene therapy holds the promise of delivering more targeted and effective treatments, especially for individuals with rare diseases where the current treatment options are limited.'
Sickle cell disease is caused by a single 'letter' mutation in a gene that encodes haemoglobin, an essential blood molecule that helps red blood cells carry oxygen around the body. It is more prevalent in people of African descent, and patients with the disease have red blood cells that are a sickle shape, rather than the disc shape of healthy red blood cells. These sickled red blood cells restrict blood flow and limit oxygen delivery, leading to severe pain and organ damage.
Both Casgevy and Lyfgenia therapies involve a treatment known as an allogeneic haematopoietic stem cell transplant, more commonly known as a bone marrow transplant. The patients' own blood stem cells are collected and modified outside the body before being transplanted back into the patients, who are then able to produce the functioning blood molecule.
However, patients must firstly undergo chemotherapy and radiotherapy to wipe out their immune system before it is rebuilt in a single-dose infusion of their own modified stem cells.
'Now, after decades of limited progress in treating sickle cell disease, we have reached a historical moment with two new gene therapies.' Dr Alexis Thompson, chief of the division of haematology at Children's Hospital of Philadelphia, said.
However, Victoria Gray, the first person with sickle cell disease to be treated with Casgevy has said: 'Cost is a worry'.
Casgevy has a list price of $2.2 million per patient, while Lyfgenia is priced at $3.1 million per patient, making them among the most expensive medicines on the market. All patients who received the drugs will be monitored to evaluate each drug's safety and effectiveness in a long-term follow up study.
Casgevy was developed by Vertex Pharmaceuticals in Boston, Massachusetts, in partnership with CRISPR Therapeutics from Zug, Switzerland. Lyfgenia was developed by Bluebird Bio Inc in Somerville, Massachusetts.
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