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Mahesh

19/12/23 10:42 AM IST

The era of CRISPR therapeutics

In News
  • Recently, two highly anticipated CRISPR-based therapies for sickle-cell disease and β-thalassaemia in the U.K. and the U.S was approved.
CRISPR technology
  • The discovery of the CRISPR system was the result of almost three decades of pure academic pursuit.
  • Clustered regularly interspaced short palindromic repeats (CRISPR) are DNA elements that Spanish researchers discovered in archaea in 1993, and named and described later in a number of bacterial genomes.
  • These elements contain pieces of genetic material derived from viruses that infect bacteria (i.e. bacteriophages) and a set of proteins called Cas, or CRISPR-associated.
  • Researchers tried to explain the elements’ effect on antiviral immunity in 2005, but later found that CRISPR + Cas proteins could detect and prevent viral infections.
  • That is, the two formed an antiviral defence system and helped bacteria ‘acquire’ resistance.
  • In 2010, scientists demonstrated that CRISPR + specific proteins called Cas9 had the ability to cut double-stranded DNA at specific points. They also found the RNAs molecules that guided the Cas9 proteins to specific positions on a genome.
  • The 2020 Nobel Prize didn’t only honour the researchers: it also symbolised the start of a time in which people couldn’t just read human genomes but also edit or modify the genetic code, with potentially long-lasting impacts on the future of medicine and genetic engineering.
CRISPR in medicine
  • The national regulator in the U.K., the Medicines and Healthcare products Regulatory Agency (MHRA), approved the use of a CRISPR-based method called exagamglogene autotemcel – sold under the brand ‘Casgevy’ – to treat sickle-cell disease and transfusion-dependent β-thalassemia.
  • The approval came after the MHRA evaluated safety and efficacy data in an ongoing clinical trial in 29 and 42 patients respectively.
  • The U.S. Food and Drug Administration also approved Casgevy to treat sickle-cell disease, rendering it one of the first CRISPR-based therapeutics to be approved by two major drug regulators.
  • In Casgevy, a patient’s blood stem cells are extracted, their genes modified to remove the defect that produces the sickling, and regrafted back. These cells then proliferate to produce normal red blood cells.
Concerns
  • None of these technologies are without caveats. Researchers have already reported several safety and accuracy issues.
  • An important one is off-target events: where a CRISPR-Cas9 system becomes inaccurate and edits some other part of the genome, with unintended consequences.
  • Many of these therapies are also too early in their development cycle.
  • Continued scrutiny and surveillance may yet reveal ‘side effects’ that we aren’t aware of today.
Source- The Hindu

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