1. Subjects previously treated with PRO044.
2. Continued use of glucocorticoids for a minimum of 60 days prior to study entry with a reasonable expectation that the subject will remain on steroids for the duration of the study. Changes to the dose regimen or cessation of glucocorticoids will be at the discretion of the Principle Investigator (PI) in consultation with the subject/parent and the Medical Monitor. If the subject is not on steroids, involvement in the study needs to be discussed with the medical monitor

1. Current, or history of, liver or renal disease.
2. Acute illness within 4 weeks prior to the first dose of PRO044 (Week 1) which may interfere with the measurements.
3. Severe cardiac myopathy which in the opinion of the Investigator prohibits participation in this study
4. Need for daytime mechanical ventilation.
5. Screening aPTT above the upper limit of normal (ULN).
6. Screening platelet count below the lower limit of normal (LLN).
7. Use of anticoagulants, antithrombotics or antiplatelet agents.
8. Use of any investigational product within 6 months prior to the start of Screening for the study.
9. Current or history of drug and/or alcohol abuse