British regulators this week approved the first CRISPR therapy for treating humans and US regulators could approve the therapy - designed to treat blood disorders - as early as December. At the same time, the US company behind another CRISPR technology, "base editing", reported a successful initial study, although two of the ten subjects suffered heart attacks, leading to the death of a trial participant.

British regulators on Thursday approved a therapy using CRISPR gene-editing technology to treat two blood diseases. U.S. federal regulators are poised to approve this same treatment in December.

The exa-cel therapy, which goes by the brand name Casgevy, is the first CRISPR therapy for humans to be approved for the market.

CRISPR is a gene-editing technology that acts like a pair of “genetic scissors,” allowing scientists to modify sections of DNA by “cutting out” specific portions and replacing them with new segments. First announced in a 2012 paper, CRISPR is considered a simple and inexpensive way to edit genes.

Its inventors were awarded the Nobel Prize in Chemistry in 2020. In recent years, applications in plant manipulation and research into possible use in humans have proliferated, with the technology being touted as a potential solution to issues ranging from disease to food security to climate change.

But this research has been highly controversial, and a long series of papers have been published detailing the unintended effects of CRISPR gene editing, which has been shown to produce many types of severe, unintended DNA damage.

Casgevy is designed to treat two blood diseases: sickle cell disease and beta thalassemia. Sickle cell disease, also known as sickle cell anemia, occurs most often in people of African or Caribbean descent. It can cause debilitating pain.

People with beta thalassemia, which can cause mild or severe anemia, may need regular blood transfusions.

Both of these genetic diseases are caused by errors in the genes for hemoglobin, a protein that allows red blood cells to carry oxygen around the body, and both can be fatal.

The therapy, developed by Vertex Pharmaceuticals and CRISPR Therapeutics, was approved after a sickle cell trial that followed only 29 participants out of a total of 45 for 16 months. Twenty-eight of the people monitored no longer had pain after a year, according to Nature.

In the clinical trial for beta thalassemia, 39 of 42 trial participants did not need to receive a red blood cell transfusion for at least 12 months after receiving Casgevy. They usually need blood transfusions every three to five weeks.

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