Phase 3 Sly Syndrome Data Presented at MPS Meeting

James Radke

New topline data from Ultragenyx’s phase 3 Sly Syndrome study was presented at 14th International Symposium on MPS and Related Diseases in Bonn, Germany and the trial has met its primary endpoint. The trial, testing the efficacy of recombinant human beta-glucuronidase (rhGUS) in patients with Mucopolysaccharidosis 7 (aka Sly syndrome) showed a reduction of 65% of urinary GAG (dermatan sulfate) excretion after 24 weeks of treatment (P < .0001).
The study also showed improvements in several secondary endpoints, but did not quite reach statistical significance. For example, the Multi-domain Responder Index (MDRI) score at 24 weeks of treatment had an overall mean improvement (±SD) of +0.5 domains (±0.80) (P = .0527). The MDRI is a summation of scores from each of the following domains: the six-minute walk test (6MWT), forced vital capacity (FVC), shoulder flexion, visual acuity, and the Bruininks-Oseretsky Test of Motor Proficiency (BOT-2) fine motor and gross motor function. 
All patients experienced treatment emergent adverse events (AEs), which were generally mild to moderate in severity. There were no deaths and no treatment discontinuations or missed infusions due to AEs. Seven of the 12 patients developed anti-rhGUS antibodies, which were not associated with immune-mediated AEs.
In a press release, Ultragenyx noted that they plan to meet with the FDA and EMA this year to discuss their plans to submit regulatory filings in the first half of 2017.

About MPS 7 (Sly Syndrome)

Mucopolysaccharidosis 7 (MPS 7, Sly syndrome), is a rare genetic, metabolic disorder caused by the deficiency of beta-glucuronidase, an enzyme required for the breakdown of the glycosaminoglycans (GAGs) dermatan sulfate, chondroitin sulfate and heparan sulfate. 
In the video clip below, we talked with Dr William Sly about the condition that he was named after.
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