Transkaryotic Therapies Inc reported results from a Phase I/II study evaluating its investigational enzyme replacement therapy, iduronate-2-sulfatase (I2S) enzyme replacement therapy, as a treatment for Hunter syndrome. At the American Society of Human Genetics Annual Meeting, Joseph Muenzer from the University of North Carolina at Chapel Hill reported that in the trial I2S administration was generally well-tolerated and demonstrated evidence of clinical activity in patients with Hunter syndrome. TKT believes these data support the advancement of this program into pivotal clinical testing.

"Patients with Hunter syndrome often lead shortened lives with only palliative treatment options available," said Dr. Muenzer. "For the first time, we have a specific therapy that may improve the prognosis of children with Hunter syndrome."

The randomized, double-blind, placebo-controlled study evaluated the safety of I2S and its clinical activity in twelve patients affected with Hunter syndrome. Three doses were studied (0.15 mg/kg, 0.5 mg/kg, and 1.5 mg/kg), and within each dose group three patients were randomized to receive I2S and one patient to receive placebo by a 60-minute IV infusion biweekly for six months. All twelve patients have completed the six-month study and have elected to enroll in an open-label extension study. Nine of the 12 patients have now received I2S for at least one year.

Overall, I2S displayed a favorable safety profile. The most common side effects from I2S treatment were hives, chills, fever, and facial flushing. Infusion-related reactions occurred in five of six treated patients in the 0.5 mg/kg and 1.5 mg/kg groups and have been successfully managed by slowing the infusion rate and using premedications. Only one of the nine treated patients developed an antibody to I2S.