Shire has submitted a biologics license application (BLA) to the FDAfor idursulfase under the tradename Elaprase, formerly referred to as I2S. If approved, Elaprase would be the first human enzyme replacement therapy for the treatment of Hunter syndrome, also known as Mucopolysaccharidosis II (MPS II).

The BLA contains data results of the pivotal AIM (Assessment of I2S in MPS II) study, which studied 96 patients over 52 weeks, and is the largest study ever conducted for a MPS disorder. The primary efficacy outcome assessments were distance walked during six minutes as a measure of endurance, and percent predicted forced vital capacity as a measure of pulmonary function. The primary endpoint combined these two components into a composite score. Patients who received 0.5mg/kg of Elaprase on a weekly basis showed a statistically significant difference in the primary efficacy endpoint, compared to patients receiving placebo.