Sangamo Therapeutics announced treatment of the first patient in the Phase 1/2 clinical trial (the CHAMPIONS study) evaluating SB-913, an investigational in vivo genome editing therapy for people with mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome.

"For the first time, a patient has received a therapy intended to precisely edit the DNA of cells directly inside the body. We are at the start of a new frontier of genomic medicine," said Dr. Sandy Macrae, CEO of Sangamo Therapeutics.

Sangamo aims to treat MPS II by using genome editing to insert a corrective gene into a precise location in the DNA of liver cells with the goal of enabling a patient's liver to produce a lifelong and stable supply of an enzyme he or she currently lacks.

Without that enzyme, called iduronate-2-sulfatase (IDS), people with MPS II suffer debilitating buildup of toxic carbohydrates in cells throughout their body. Approximately one in 100,000 to one in 170,000 people are born with MPS II. Many people with MPS II receive weekly infusions of enzyme replacement therapy (ERT), the current standard-of-care treatment. Within a day of receiving ERT, however, IDS returns to near undetectable levels in the blood.

The CHAMPIONS study, which is also screening subjects at hospitals specializing in the care of patients with MPS II, including hospitals in Chapel Hill, Chicago, Minneapolis and Philadelphia, is an open-label clinical study designed to assess the safety, tolerability and preliminary efficacy of the SB-913 investigational genome editing therapy in up to nine adult males with MPS II.

Sangamo's SB-913 makes use of the company’s zinc finger nuclease (ZFN) genome editing technology to insert a corrective gene into a precise location in the DNA of liver cells. To restrict editing to liver cells, the ZFNs and the corrective gene are delivered in a single intravenous infusion using AAV vectors that target the liver. The ZFNs enter the cells as inactive DNA instructions in a format designed only for liver cells to unlock.

The ability to permanently and precisely integrate the therapeutic IDS gene into the DNA differentiates Sangamo's in vivo genome editing approach from conventional AAV cDNA gene therapy and from lenti- or retroviral-based gene therapies that insert genes randomly into the genome.

Two additional clinical trials are underway in the United States to evaluate Sangamo's in vivo genome editing therapeutics for hemophilia B and MPS I, which is also known as Hurler or Hurler-Scheie syndrome. All three trials use ZFNs designed to edit liver cells at the same location in the albumin gene, but differ in delivering the corrective gene relevant to the respective disease.

All three of Sangamo's in vivo genome editing product candidates have received Fast Track and Orphan Drug designations from the U.S. Food and Drug Administration (FDA). Additionally, SB-318 for MPS I and SB-913 for MPS II have received Rare Pediatric Disease designations from the FDA.