Transkaryotic Therapies Inc has dosed the first patient in the Assessment of Iduronate-2-Sulfatase in MPS II (AIM) Pivotal Trial. The AIM study is a randomized, double-blind, placebo-controlled, clinical trial to evaluate the effect of iduronate-2-sulfatase (I2S) over twelve months in patients with Hunter syndrome, also referred to as MPS II.

Ninety patients with Hunter syndrome will be enrolled at eight sites around the world. If the results are positive, TKT expects to file applications for market approval in the United States and Europe in 2005. There is currently no effective therapy for Hunter syndrome.

"Patients in the initial trial saw significant improvements in overall activity levels and treatment was generally well-tolerated," said Dr. Joseph Muenzer of the University of North Carolina at Chapel Hill and lead investigator of the study. "We are excited to expand the scope of clinical testing for I2S and are hopeful this study will demonstrate robust clinical benefit in a much wider patient population."

The primary objective of the study is to determine safety and efficacy of I2S as a treatment for Hunter syndrome. Ninety patients will be randomized equally to three treatment groups receiving either weekly or every other week infusions of I2S at a dose of 0.5 mg/kg or weekly infusions of placebo for twelve months. Efficacy outcomes will be measured at baseline and at four month intervals. There will not be an interim analysis performed in the study. The primary efficacy endpoint will be a single composite variable. The composite variable will combine two clinical measurements: forced vital capacity as a measure of respiratory function and the six-minute walk test as a measure of functional capacity. Additional efficacy endpoints include measurements of joint range of motion and combined liver and spleen size.

"It is devastating for families to learn that a child has Hunter syndrome. However, today's news provides reassurance that we are one step closer to turning the hope of treatment into a reality through the development of I2S," said Christine Lavery of the United Kingdom MPS Society. "If successful, I2S will be the first treatment to clinically address Hunter syndrome and we are hopeful that all patients will have access to this important therapy."