US scientists attempt gene editing inside the human body

16 Nov 2017

Gene editing is making major advances. Image: Christoph Burgstedt

New therapy will permanently alter DNA, and could help to defeat previously incurable diseases.

In a gene editing breakthrough, Brian Madeux has become the first person to intravenously receive billions of copies of a corrective gene and a genetic tool to precisely cut his DNA, according to Associated Press.

Madeux has Hunter syndrome, a very rare genetic disorder caused by a missing or malfunctioning enzyme. Symptoms can include an enlarged head, skeletal irregularities and developmental delays.

He described being the first person to test the procedure as “kind of humbling” and said he was willing to take the risk if the treatment could hold the chance to help him and others suffering from a myriad of metabolic illnesses.

Signs of its effectiveness could come in as little as a month, while definitive tests in three months will demonstrate whether it works for sure.

Invisible mending

Dr Sandy Macrae, president of Sangamo Therapeutics (the company carrying out the treatment), said: “We cut your DNA, open it up, insert a gene, stitch it back up – invisible mending. It becomes part of your DNA and is there for the rest of your life.”

Another expert, Dr Eric Topol of the Scripps Translational Science Institute, said that although the risks couldn’t be fully known, studies into this treatment should move ahead for incurable diseases. For him, gene editing has too much potential to be disavowed just yet: “So far, there’s been no evidence that this is going to be dangerous. Now is not the time to get scared.”

Science explained that although researchers could one day use gene editing to repair the flawed gene in cells that cause diseases such as Hunter syndrome, that is not the goal of the trial Madeux is taking part in.

“Instead, the company inserts a replacement copy of the gene, using gene editing to snip the DNA helix of liver cells in a specific place near the promotor, or on-off switch, for the gene for a protein called albumin.

“The cells fix the repair by inserting the DNA for the new gene supplied by the researchers, along with the gene editor’s DNA scissors, and the gene’s activity is then controlled by the powerful albumin promotor.”

In short, transforming these modified liver cells into a factory for making the enzyme missing in Hunter syndrome is the aim.

Although those with Hunter syndrome can receive weekly infusions of the enzyme in question, their blood levels can drop within a day. Researchers hope that a one-time, three-hour intravenous infusion could allow the liver to steadily produce the enzyme for years.

Gene editing could change lives

Technically, Madeux is not the first human being to benefit from gene editing. Science explained that several years ago, Sangamo Therapeutics used the same type of DNA scissors, called a zinc finger nuclease (ZFN), to protect patients from HIV by “by harvesting their blood cells, disrupting a gene in them in culture cells and then transfusing the cells back into the patients”.

However, this is the first time ZFNs have been used to modify DNA in living patients, which is much more complicated than editing genes in a lab dish.

Despite the risks, Madeux said he was “nervous and excited” to see the outcome of the possibly life-altering treatment: “I’ve been waiting for this my whole life, something that can potentially cure me.”

Ellen Tannam was a journalist with Silicon Republic, covering all manner of business and tech subjects