• Scientists think they have achieved the first gene editing inside the body, altering DNA in adults to try to treat a disease, although it’s too soon to know if this will help.
• Preliminary results suggest that two men with a rare disorder now have a corrective gene at very low levels, which may not be enough to make the therapy a success.
• Still, it’s a scientific milestone toward one day doctoring DNA to treat many diseases caused by faulty genes.
What is Gene editing?
• Gene editing is intended as a more precise way to do gene therapy, to disable a bad gene or supply a good one that’s missing.
• Trying it in adults to treat diseases is not controversial and the DNA changes do not pass to future generations, unlike the recent case of a Chinese scientist who claims to have edited twin girls’ genes when they were embryos.
• The studies involve men with Hunter or Hurler Syndrome, diseases caused by a missing gene that makes an enzyme to break down certain sugar compounds.
• Without it, sugars build up and damage organs, often killing people in their teens.
• In 2017, Brian Madeux of Arizona became the first person to try it.
• Through an IV, he received many copies of a corrective gene and an editing tool called zinc finger nucleases to insert it into his DNA.
• Results on him and seven other Hunter patients, plus three with Hurler Syndrome, suggest the treatment is safe, which was the main goal of these early experiments.
• Three problems bronchitis, an irregular heartbeat and a hernia — were deemed due to the diseases, not the treatment.
• Tissue samples showed evidence of gene editing at very low levels in two Hunter patients who were given a middle dose but not in one given a low dose.
• Tests are expected later this year on patients who received the highest dose and on Hurler patients.
• Blood tests detected slightly higher levels of the missing enzyme in a few of the Hunter patients but none of them reached normal levels.
• One patient had a larger increase but also showed signs that his immune system might be attacking the therapy. He was treated for that and symptoms resolved.
• More encouraging results were seen in Hurler patients enzyme levels rose to normal in all three after treatment, tests on certain blood cells showed.
• None of the patients with either disease showed a sustained decline in urine levels of the sugar compounds, though, and some other tests also did not detect intended effects of the therapy.
A positive sign
• The key test will be stopping the patients’ weekly enzyme treatments to see if their bodies can now make enough of it on their own.
• Three have gone off treatments so far and one was recently advised to resume them because of fatigue and rising levels of the sugar compounds.
• The others have not been off long enough to know how they will fare.
• “It looks like it’s safe that’s a very positive sign,” said one independent expert, Dr. Kiran Musunuru of the University of Pennsylvania.
• He called the early results promising but said “it’s hard to be sure it’s doing any good” until patients are studied lo
Mains Paper 3: Science and Technology
Prelims level: gene editing