The purpose of the study is to evaluate the safety, efficacy and pharmacokinetics of two dose levels of weekly intravenous infusions of recombinant human N-acetylgalactosamine 4-sulfatase (rhASB) for a minimum of 24 weeks in patients diagnosed with MPS VI.

Inclusion Criteria:

• Patient consent
• Patient must be five years of age or older
• Patient must have documented diagnosis of MPS VI, confirmed at screening by measurable clinical signs and symptoms of MPS VI
• Leukocyte ASB enzyme activity level less than 20% of the normal range
• Clinical evidence of significant MPS VI disease that provides adequate opportunity to achieve quantitative, short-term therapeutic benefit in three or more of the following parameters: endurance (as measured by a six-minute walk test), forced vital capacity (as measured by spirometry), joint range of motion, urinary glycosaminoglycans, and hepatomegaly.
• Ability to perform all protocol tests
• Ability to stand independently for six minutes
• Sexually active subjects must agree to use an adequate form of contraception

Exclusion Criteria:

• History of bone marrow transplantation
• Pregnant or lactating patient
• Use of an investigational drug or device within 30 days prior to study participation.
• A medical condition, serious intercurrent illness, or other extenuating circumstances that may significantly decrease study compliance including prescribed follow-up
• Known hypersensitivity to rhASB or to components of the study drug
• History of cancer (except low grade and fully resolved skin malignancy)