CHAPEL HILL – A man suffering from a rare genetic disease has been treated with a novel genome-editing therapy at the University of North Carolina’s Clinical and Translational Research Center.

The therapy, called SB-913, is based on a proprietary genome-editing technology developed by Sangamo Therapeutics, a biotechnology company in the San Francisco Bay area. It was given last week in Chapel Hill to a 40-year-old patient with Hunter’s syndrome, also known as mucopolysaccharidosis II (MPS II), a metabolic disorder caused by a deficient or missing enzyme.

The man is one of as many as nine adult males who are being treated with the investigational therapy in a Phase 1/2 clinical trial, called CHAMPIONS, sponsored by Sangamo. CHAMPIONS is an open-label clinical study designed to assess the safety, tolerability and preliminary efficacy of three dose levels of SB-913.

Dr. Joseph Muenzer

The UNC patient was treated by Joseph Muenzer, M.D., Ph.D., a pediatric biochemical geneticist who specializes in disorders such as Hunter syndrome. It was the first time in his long research career that Muenzer administered a gene therapy treatment to a patient with this condition.

“I developed a mouse model for Hunter syndrome at UNC about twenty years ago to help develop therapies for this rare disorder,” Muenzer said. “I spent many years working on gene therapy in my UNC research lab, and it is with great pleasure that I am able to finally perform gene therapy on an individual with Hunter syndrome. Gene therapy has the potential to dramatically improve the quality of life for individuals with Hunter syndrome.”

Muenzer and his team “are renowned experts in the treatment of MPS diseases and continue to lead the field into a new frontier of genomic medicine,” said Ed Conner, M.D., chief medical officer of Sangamo.

Hunter syndrome is a progressive inherited disorder that primarily affects males and is caused by mutations in the gene encoding the iduronate-2-sulfatase (IDS) enzyme. Because the body lacks enough of the IDS enzyme to break down certain complex sugar molecules, the molecules build up in harmful amounts, causing permanent, progressive damage affecting appearance, mental development, organ function and physical abilities.

Symptoms can range from mild to severe, depending on the mutation and the degree of residual enzyme activity.

Children with the severe form of Hunter syndrome begin showing symptoms of developmental delay by age two or three and develop enlarged liver and spleen, airway and cardiac disease, skeletal abnormalities, hearing loss and short stature. If untreated, they often die in their teenage years.

Individuals with the milder form can have similar symptoms but never develop cognitive impairment.

Sangamo’s therapy is designed as a single treatment that inserts a corrective gene into a precise location in the DNA of liver cells, allowing a patient’s liver to produce a continuous, lifelong and stable supply of the IDS enzyme.

The therapy is based on the company’s proprietary zinc finger nuclease genome-editing technology. The ability to integrate the therapeutic IDS gene into a patient’s DNA permanently and precisely differentiates Sangamo’s genome-editing approach from other gene-therapy methods, some of which insert genes randomly into the genome.

About one in 100,000 to 170,000 males are born with Hunter syndrome in the United States. There is no cure.

Most patients receive weekly infusions of enzymes, the current standard-of-care treatment. Within a day of receiving enzyme-replacement therapy, however, their levels of the IDS enzyme plummet to nearly undetectable levels in the blood.