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PHOENIX (AP) – The first partial results of a historical gene editing study give encouraging signs that treatment may be safe and at least some of the expected effect, but it is too early to know if this end up at.
The results announced Wednesday are from the first human test of gene modification in the body, an attempt to permanently change someone's DNA to cure a disease – in this case, a genetic disorder called Hunter's syndrome that often kills teenagers.
In two patients who received an average dose of treatment, the urinary levels of large sugars characteristic of Hunter's syndrome had decreased by half, on average four months later – a possible sign of treatment. Two other people who received a low dose experienced little change in these sugars until now.
There is no way of knowing if the change in medium-dose patients is due to gene editing or anything else, but the fact that their sugars have decreased so constant as the treatment suggests.
"I absolutely can not say that it's a treatment effect," but the fall is "really encouraging," said the study's lead, Dr. Joseph Muenzer of the University of North Carolina, Chapel Hill. The main goal of early treatment studies is to test safety, although researchers are also looking for clues about how the treatment works. Muenzer gave the results at a conference in Greece and consulted the California-based maker of treatments, Sangamo Therapeutics.
The company's president, Dr. Sandy Macrae, said the tests of about five months will reveal more, but that the change in the medium-dose group so far "looks really good."
"The most rational explanation for this is that what we were hoping to achieve was going to happen," he said.
Several independent experts accepted.
"The results are exciting" and suggest that gene editing is working to some extent, with no safety issues up to now, said Dr. Howard Kaufman, a Boston scientist and panel member of the Institutes national health authorities.
Dr. Matthew Porteus, an expert in genetics at Stanford University and a consultant for two other companies developing gene therapies, said more time was needed to see how the immune system continued to respond to treatment and whether patients effects lasted, but added. "I would love to keep moving forward" based on these results.
HOW IT WORKS
Gene editing is a more accurate method of gene therapy, elimination of a bad gene or lack of gene. Doctors hope this will treat a host of diseases that can not be treated properly now.
In November, Brian Madeux, a man with Hunter syndrome in the Phoenix area, became the first to test this in the body. It lacks a gene that produces an enzyme that breaks down certain large sugar compounds called GAGs. These accumulate in the cells and cause havoc throughout the body.
Through an IV, Madeux has received many copies of a gene fix and a gene editing tool called zinc nucleases to help him locate himself in his DNA. He was one of two patients who had been administered a very low dose of treatment because this first test in humans required extreme caution.
First results
At Madeux and in the other low dose patient, urine sugar levels rose 9% on average after four months. Muenzer said that it was difficult to know if it was a significant change. Little is known about the biology of these compounds, including whether they fluctuate during the day or before or after meals.
A liver biopsy on a patient who received a low dose of treatment revealed no evidence of genetic modification, but Sangamo scientists said this dose was well below the level at which these signs had been detected in primate research.
Two other patients received an average dose corresponding to twice that of the first two patients. Their GAG levels decreased by 51% after four months, on average. Two of the main types of these sugars that accumulate in the tissues decreased by 32% and 61% respectively.
It is unclear whether such declines can improve patient health or slow the progression of the disease.
"This is not proof that this therapy is successful, but that these patients have had enough gene editing to provide them with the enzyme they need for the rest of their lives," said Muenzer.
But he said that an important goal was achieved: the treatment seems safe. There were two serious side effects – one patient was hospitalized for bronchitis and another for an irregular heartbeat – but these were judged due to their disease and pre-existing conditions, not to gene therapy.
Blood tests did not detect the missing enzyme. The company's scientists said it could be due to the fact that everything that was manufactured was quickly used by the cells rather than entering the bloodstream – an explanation accepted by outside experts. What matters, they said, was the result of enzymatic activity, the fall of sugars.
NEXT STEPS
Two other patients received the highest dose tested – 10 times the initial dose – for a total of six patients included in the study. The next step is to start removing patients from the weekly enzymatic treatments they've received to see if gene therapy has changed their bodies so that they themselves produce enough enzyme. .
More results are expected at a medical meeting in February.
"We have to see sustained levels to make it practical, if it only works for six months, it's not very beneficial," Muenzer said. "Time will tell."
In an interview at his Arizona home last month, Madeux, 45, told The Associated Press that he had volunteered for the study in the hope to be able to stop the weekly three-hour enzymatic infusions, but also to help future generations. with the disease.
"I'm old and having Hunter has done a lot of damage to my body," said Madeux. "In fact, I'm lucky to have lived that long."
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Marilynn Marchione can be followed on http://twitter.com/MMarchioneAP.
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This Associated Press series was produced in partnership with the Howard Hughes Medical Institute's Department of Science Education. The AP is solely responsible for all content.
Copyright 2018 The Associated Press. All rights reserved. This material may not be published, disseminated, rewritten or redistributed.
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