Genetic editing has been performed in the laboratory until now. Living cells within Petri-dishes have been put under the microscope while gene editing tools such as CRISPR were used to cut, nick and replace parts of the DNA or genome that is defective with bits of DNA that is correct in its sequence. Now doctors in California have attempted to edit cells within a living person.
Hunter syndrome or Mucopolysaccharidoses II, is a genetically inherited disease. It is caused due to a specific defect within the gene. This defect leads to lack of production of a key enzyme that helps to break down long sugary molecules in diet called mucopolysaccharides. So these build up within the body and lead to damage of the major organs such as the brain. It can be fatal in any individuals. As a treatment these patients are given regular replacement with the enzyme that is needed for breaking down mucopolysaccharides so as to prevent their accumulation. Brian Madeux – a 44 year old man from Arizona, underwent this experimental therapy where the gene editing tool was used to correct the defect in his DNA. The treatment is yet to show results.
His treatment involved correcting the DNA that was faulty. He was given an infusion that transferred the active agent into his blood stream. This week on Monday (13th of November 2017) he underwent the treatment at Oakland's UCSF Benioff Children's Hospital. Within the injectable infusion were two molecular scissors. These are called zinc finger nucleases or precise enzymes that can cut the DNA in two specific locations only. It would cut the two ends of the faulty sequence in the DNA. This would open up a place for the new correct piece of DNA to be inserted. This corrected piece of DNA would correctly code for the enzyme that was missing. The action would take place within the liver cells of Mr. Madeux.
According to one of the team of doctors who are trying this experimental therapy, Dr Chester Whitley, said that the process has been a success in laboratory mice. Now if it shows success among humans, a safer method of administering gene therapy could be here. For Hunter syndrome, he wishes to try this therapy shortly after birth. This would prevent the loss of mental abilities or IQ among babies born with Hunter’s syndrome, he explained.
A lot more work needs to go into this research say the team of experts to make this a “valid therapy”. Safety of the therapy also needs to be understood before it can be applied on general population. The team speculates that if there are no side effects seen in Mr. Madeux – as has been seen so far, the treatment would be experimentally tried in nine other patients of Hunter’s syndrome.
Sangamo Therapeutics designed this new gene therapy. Dr Sandy Macrae, from the same organization said that this was the first time something like this was attempted within a person. It could open up a new area in genomic medicine he said. Dr. Edward Conner, senior vice president and chief medical officer at Sangamo Therapeutics said that all it took was a two to three hour infusion. Once safety and effectiveness of this treatment is established, haemophilia B and Hurler syndrome treatment would also be planned as a next step.